Information
-
Patent Grant
-
6257782
-
Patent Number
6,257,782
-
Date Filed
Friday, June 18, 199925 years ago
-
Date Issued
Tuesday, July 10, 200123 years ago
-
Inventors
-
Original Assignees
-
Examiners
Agents
-
CPC
-
US Classifications
Field of Search
US
- 400 496
- 400 4912
- 400 490
- 400 491
- 400 4951
- 400 495
- 200 344
- 200 345
-
International Classifications
- B41J732
- H01H1370
- H01H13705
-
Abstract
A key switch comprising a base, a key top arranged above the base, a pair of link members interlocked to each other and operatively engaged with the base and the key top to support the key top above the base and direct the key top in a vertical direction, a switching mechanism for selectively opening and closing an electric circuit in connection with a vertical movement of the key top. Each of the link members includes a sliding portion slidably and shiftably engaged with either one of the base and the key top. At least one elastic member is disposed between at least one of the link members and either one of the base and the key top with which the sliding portion of each link member is engaged. The elastic member exerts biasing force, relative to a displacement or shifting amount of the sliding portion, onto at least one of the link members in a direction different from, e.g., substantially orthogonal to, the vertical shifting direction of the key top. Preferably, the biasing force assumes a linear relationship with the shifting amount of the sliding portion.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a switch mechanism for a key-entry use and, more particularly, to a key-entry switch (hereinafter referred to as a key switch) preferably used for a relatively thin keyboard incorporated in a portable electronic equipment, such as a notebook-size personal computer or word processor. The present invention also relates to a relatively thin keyboard provided with a plurality of key switches having such structures.
2. Description of the Related Art
In the technical field of portable electronic equipment, such as notebook-size personal computers or word processors, etc., various techniques have been provided, which can facilitate the reduction of height or thickness of an equipment housing including a keyboard, to improve the portability of the equipment. Particularly, when the height of a keyboard provided with a plurality of key switches is reduced, it has been generally required to maintain the stroke of each key switch at a predetermined distance to ensure a constant operational properties thereof and, simultaneously, to reduce the entire height of the key switch upon both the non-operated (or switched-off) and operated (or pushed down and switched-on) conditions thereof.
Japanese Unexamined Utility Model Publication (Kokai) No. 5-66832 (JP-U-5-66832) discloses one example of a key switch for use in such a relatively thin keyboard, which includes a key top adapted to be keyed or pushed down by an operator's finger, a base disposed beneath the key top, a pair of link members for supporting the key top above the major surface of the base and directing it in the vertical or up-and-down direction, a sheet-like switch arranged beneath the base, and an elastic actuating member located between the key top and the sheet-like switch so as to open and close the sheet-like switch corresponding to the vertical or up-and-down movement of the key top.
The pair of link members are pivotably connected with each other, so as to be provided with a generally X-shape in a side view. A first link member is engaged slidably at one end thereof with the base and rotatably at the other end with the key top. A second link member is engaged rotatably at one end thereof with the base and slidably at the other end with the key top. In this manner, the key top is subjected to a parallel displacement in a substantially vertical direction in relation to the major surface of the base, while keeping a predetermined posture of the key top.
The elastic actuating member is a dome-like member integrally formed from a rubber material. The elastic actuating member is placed on the sheet-like switch through an opening formed in the base at a position beneath the key top, with the upper end of the dome facing toward the key top. The sheet-like switch is structured as a pair of conductive contacts opposed to each other and respectively carried on two film-like printed circuit boards. The sheet-like switch is positioned beneath the elastic actuating member normally in an opened state. In this specification, such a contact pair is referred to as a membrane switch, and a pair of film-like boards provided with a membrane switch is referred to as a membrane sheet.
When no external force is applied to the key top, the elastic actuating member supports the key top on the outer surface of the dome upper end, and urges the key top toward an initial position vertically upwardly away from the base. When the key top is pushed downward by a key-entry operation, the elastic actuating member is elastically deformed while exerting a biasing or an elastic restoring force to the key top in an opposite or upward direction. In this condition, a projection formed on the interior surface of the dome upper end serves to push the outer surface of the membrane sheet, so as to close or turn-on the membrane switch. When the downward pushing force applied to the key top is released, the elastic actuating member is elastically restored, so as to return the key top to the initial position and to open or turn-off the membrane switch.
In the above-mentioned conventional key switch, including a pair of link members used as means for supporting/directing the key top, it is possible to fold the link members and put them within a space between the key top and the base as the key top is downwardly displaced. Accordingly, in comparison with other conventional structures including, as means for supporting/directing the key top, a telescopic shaft assembly using a shaft and a bearing which can be slidingly moved relative to each other in a vertical or going up and down direction of the key top, it is possible to further reduce the entire height of the key switch upon both the inoperated and operated conditions thereof, while maintaining the stroke of the key switch at a predetermined distance.
Japanese Unexamined Patent Publication (Kokai) No. 9-27235 (JP-A-9-27235) discloses another example of a key switch also including a pair of link members used as means for supporting/directing a key top. In this key switch, the link members are assembled into a generally X-shape in a side view and are slidably connected with each other at an intersection thereof. Both link members are engaged slidably at one ends thereof with the base and rotatably at the other ends with the key top. In this structure, the key top is also permitted to be subjected to a parallel displacement in a substantially vertical direction in relation to the major surface of the base, and it is also possible to reduce the entire height of the key switch upon both the non-operated and operated conditions thereof, while maintaining a predetermined distance of the stroke of the key switch.
Japanese Unexamined Patent Publication (Kokai) No. 9-190735 (JP-A-9-190735) discloses a further example of a key switch also including a pair of link members used as means for supporting/directing a key top. In this key switch, the link members are assembled into a generally reverse V-shape in a side view and meshed with each other at the toothed ends thereof. Both link members are engaged slidably at one free ends thereof with the base and rotatably at the other toothed ends with the key top. In this structure, the key top is also permitted to be subjected to a parallel displacement in a substantially vertical direction in relation to the major surface of the base, and it is also possible to reduce the entire height of the key switch upon both the inoperated and operated conditions thereof, while maintaining a predetermined distance of the stroke of the key switch.
In a relatively thin keyboard provided with a plurality of key switches each having the above-mentioned pair of link members, a structure is known in which the key top of each key switch is held in an initial projecting position for a key-entry operation during the operating state of the keyboard, while the key top is positively displaced to a retracted position lower than the initial position during the inoperating (or carrying) state of the keyboard, in order to improve the portability of the keyboard.
For example, Japanese Unexamined Patent Publication (Kokai) No. 9-63402 (JP-A-9-63402) discloses a yet further example of a key switch including a dome-shaped elastic actuating member fixedly mounted on a membrane sheet. The elastic actuating member of this key switch can be shifted in a lateral direction together with the membrane sheet in an integral manner under the key top. In the operating state of the keyboard, the elastic actuating member of each key switch is located at a position for supporting the key top thereof in an initial projecting position. On the other hand, during the non-operating state of the keyboard, the elastic actuating member of each key switch is laterally shifted and located at a position where the key top thereof is not supported on the actuating member, and thereby the key top is displaced into a retracted position which corresponds to a pushed-down position in the key-entry operation.
As disclosed in each of the above prior-art documents, the conventional key switch generally utilizes a dome-shaped elastic actuating member as means for opening/closing a membrane switch. The elastic actuating member also serves as means for elastically upwardly biasing the key top away from the base. Therefore, when the actuating member is elastically deformed by a key-entry operation of the key top, the actuating member exerts biasing or elastic restoring force to the key top, which assumes non-linear relationship with a displacement of the key top, due to the dome-shaped profile of the actuating member.
That is, the key switch can establish such a key-entry operating properties that, at the instant when the pushed-down displacement of the key top exceeds a predetermined value, the biasing force, which has been gradually increased until that time, is sharply reduced. As a result, an operator can recognize that the key switch has been correctly and appropriately operated by the finger, even when the keyboard is one adapted to be incorporated in a portable electronic equipment, in which the key switch generally has a relatively short keying stroke.
The dome-shaped elastic actuating member is, however, kept in a location between the key top and the membrane sheet and interposed therebetween in relation to the height of the key switch, regardless of the degree of the deformation of the actuating member. Therefore, the dome-shaped elastic actuating member in itself affects the entire height of the key switch upon both the inoperated and operated conditions thereof. Accordingly, even if the use of the link members as means for supporting/directing the key top could reduce the entire height of the key switch, there is a difficulty in reducing the height or thickness of the key switch and thus of the keyboard, due to the provision of the dome-shaped elastic actuating member.
Further, in the conventional key switch wherein the key top can be displaced into the retracted position by shifting the elastic actuating member in a lateral direction during the inoperating state of the keyboard, it is necessary to define a sufficient space to accommodate not only the link members but also the dome-shaped elastic actuating member not deformed, between the retracted key top and the base. Consequently, the dimension of the key top tends to be increased particularly in the height direction.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a key switch for a key-entry operation, which can significantly reduce the entire height of the key switch upon both the inoperated and operated conditions thereof, by a relatively simple and low-cost structure.
It is another object of the present invention to provide a key switch for a key-entry operation, which can eliminate a dome-shaped elastic actuating member while maintaining the non-linear feeling of the key-entry operation of the key switch.
It is further object of the present invention to provide a keyboard including a plurality of key switches, which can significantly reduce the entire height or thickness of the keyboard and can improve the portability thereof.
In accordance with the present invention, there is provided a key switch comprising a base; a key top arranged above the base; a pair of link members interlocked to each other and operatively engaged with the base and the key top to support the key top above the base and direct the key top in a vertical direction, each of the link members including a sliding portion slidably and shiftably engaged with either one of the base and the key top; at least one elastic member disposed between at least one of the link members and either one of the base and the key top with which the sliding portion is engaged, to exert biasing force, relative to a shifting amount of the sliding portion, onto the at least one of the link members in a direction different from the vertical direction; and a switching mechanism for selectively opening and closing an electric circuit in connection with a vertical movement of the key top.
It is preferred that at least one elastic member exerts biasing force assuming a linear relationship with the shifting amount of the sliding portion, onto at least one of the link members.
It is also preferred that at least one elastic member exerts biasing force in a direction substantially orthogonal to the vertical direction, onto at least one of the link members.
It is also preferred that at least one of the link members is provided with a loading portion separately from the sliding portion, the biasing force being applied onto the loading portion.
In this arrangement, the loading portion may be shifted in a motion different from the sliding portion when the sliding portion is shifted.
At least one elastic member may be fixedly joined to the base and abutted with the at least one of the link members.
Alternatively, at least one elastic member may be fixedly joined to the at least one of the link members and abutted with the base.
The elastic member may comprise a compression spring.
Preferably, the elastic member comprises a plate spring.
It is preferred that the pair of link members are arranged to mutually intersect and are pivotably connected relative to each other at an intersection thereof, that a first one of the link members is engaged slidably at one end thereof with the base and rotatably at another end thereof with the key top, the sliding portion being provided on the one end of the first link member, and that a second one of the link members is engaged rotatably at one end thereof with the base and slidably at another end thereof with the key top, the sliding portion being provided on the other end of the second link member.
It is also preferred that the pair of link members are arranged to mutually intersect and are pivotably and slidably connected relative to each other at an intersection thereof, and that each of the link members is engaged slidably at one end thereof with the base and rotatably at another end thereof with the key top, the sliding portion being provided on the one end of the each link member.
It is also preferred that the pair of link members are meshed with each other at a toothed end of each of the link members, and that each of the link members is engaged slidably at one end thereof with the base and rotatably at another end thereof with the key top, the sliding portion being provided on the one end of the each link member, the toothed end being provided adjacent to the other end of the each link member.
In this arrangement, the link members may be arranged to intersect with each other.
The switching mechanism may comprise a membrane switch arranged in an opening formed in the base beneath the key top, and an actuating member for pushing the membrane switch to close the electric circuit when the key top goes down and is located at a predetermined position above the base.
In this arrangement, the actuating member may be provided on the key top and may enter into the opening of the base to elastically push the membrane switch when the key top is located at the predetermined position.
Alternatively, the actuating member may be provided on at least one of the link members and may enter into the opening of the base to elastically push the membrane switch when the key top is located at the predetermined position.
In this arrangement, the key switch may further comprise an assist member movable between a first position where the assist member comes into engagement with the actuating member and a second position where the assist member is away from the actuating member, during a time when the key top is located at the predetermined position, and the actuating member may come into engagement with the assist member to push the membrane switch.
Alternatively, the actuating member may be disposed above the membrane switch, and a part of the link members may enter into the opening of the base to push the actuating member when the key top is located at the predetermined position, whereby the actuating member pushes the membrane switch.
In this arrangement, the actuating member may be movable between a first position where the actuating member is pushed by the part of the link members and a second position where the actuating member is away from the part of the link members, during a time when the key top is located at the predetermined position.
Alternatively, the membrane switch may be movable between a first position where the membrane switch is pushed by the actuating member to close the electric circuit and a second position where the membrane switch is away from the actuating member to keep the electric circuit open, during a time when the key top is located at the predetermined position.
The key switch may further comprise means for selectively securing the sliding portion of the at least one of the link members in relation to either one of the base and the key top with which the sliding portion is engaged, to hold the key top at a desired lowered position.
The base may include a fixed base element engaged with the pair of link members and a movable base element disposed under the fixed base element in such a manner as to be movable with relation to the fixed base element.
In this arrangement, at least one elastic member may be fixedly connected to the movable base element and abutted onto the at least one of the link members.
Alternatively, at least one elastic member may be fixedly connected to at least one of the link members and abutted onto at least one vertical wall fixedly joined to the movable base element.
The movable base element may be moved in a direction generally parallel to a shifting direction of the sliding portion of the each link member.
Alternatively, the movable base element may be moved in a direction generally orthogonal to a shifting direction of the sliding portion of the each link member.
The present invention further provides a key switch comprising a base; a key top arranged above the base; a guide member operatively engaged with the base and the key top to support the key top above the base and direct the key top in a vertical direction, the guide member including a sliding portion slidably and shiftably engaged with either one of the base and the key top; an elastic member disposed between the guide member and either one of the base and the key top with which the sliding portion is engaged, to exert a biasing force, relative to a shifting amount of the sliding portion, onto the guide member in a direction different from the vertical direction; and a switching mechanism for selectively opening and closing an electric circuit in connection with a vertical movement of the key top.
It is preferred that the guide member is structured from a plurality of link members interlocked to one another, each of the link members being operatively engaged with the base and the key top and including the sliding portion, and that at least one of the link members is associated with at least one the elastic member.
The present invention yet further provides a keyboard comprising a plurality of key switches, each of the key switches being one as defined above.
The present invention yet further provides a keyboard comprising a plurality of key switches, each of the key switches being one as defined above, wherein the movable base element of the each key switch is formed as a single large plate extending over the plurality of key switches, the single large plate being movably disposed under a plurality of fixed base elements of the key switches.
BRIEF DESCRIPTION OF THE DRAWINGS
The above and other objects, features, and advantages of the present invention will become more apparent from the following description of preferred embodiments in connection with the accompanying drawings, in which:
FIG. 1
is an exploded perspective view showing a first embodiment of a key switch according to the present invention;
FIG. 2
is a sectional view of the key switch of
FIG. 1
in an assembled state, taken along line II—II of
FIG. 1
;
FIG. 3
is a sectional view of the key switch of
FIG. 1
in an assembled state, taken along line III—III of
FIG. 1
;
FIGS. 4A
to
4
C illustrate the principle of the key-entry operation properties of the key switch of
FIG. 1
;
FIG. 5
is an exploded perspective view of a modification of the key switch shown in
FIG. 1
;
FIG. 6
is an exploded perspective view showing a second embodiment of a key switch according to the present invention;
FIG. 7
is a sectional view of the key switch of
FIG. 6
in an assembled state, taken along line VII—VII of
FIG. 6
;
FIG. 8
is an exploded perspective view of a modification of the key switch shown in
FIG. 6
;
FIG. 9
is a perspective view of a modification of link members used in the key switch shown in
FIG. 6
;
FIG. 10
is an exploded perspective view showing a third embodiment of a key switch according to the present invention;
FIG. 11
is a sectional view of the key switch of
FIG. 10
in an assembled state, taken along line XI—XI of
FIG. 10
;
FIG. 12
is an exploded perspective view of a modification of the key switch shown in
FIG. 10
;
FIG. 13
is an exploded perspective view showing a fourth embodiment of a key switch according to the present invention;
FIG. 14
is an exploded perspective view showing a fifth embodiment of a key switch according to the present invention;
FIG. 15
is a partially cut-away perspective view showing one embodiment of a keyboard according to the present invention, which is provided with a plurality of key switches as shown in
FIG. 14
;
FIG. 16
is an exploded perspective view of a modification of the key switch shown in
FIG. 14
;
FIG. 17
is an exploded perspective view showing a sixth embodiment of a key switch according to the present invention;
FIG. 18
is a sectional view of the key switch of
FIG. 17
in an assembled state, taken along line XVIII—XVIII of
FIG. 17
;
FIGS. 19A
to
19
C illustrate the principle of the key-entry operation properties of the key switch of
FIG. 17
;
FIG. 20
is an exploded perspective view of a modification of the key switch shown in
FIG. 17
;
FIG. 21
is an exploded perspective view showing a seventh embodiment of a key switch according to the present invention;
FIG. 22
is an exploded perspective view of a modification of the key switch shown in
FIG. 21
;
FIG. 23
is an exploded perspective view showing an eighth embodiment of a key switch according to the present invention;
FIG. 24
is an exploded perspective view of a modification of the key switch shown in
FIG. 23
;
FIG. 25
is an exploded perspective view showing a ninth embodiment of a key switch according to the present invention;
FIGS. 26A
to
26
C are schematic sectional views illustrating the operational principle of an actuating member in the key switch of
FIG. 25
;
FIG. 27
is an exploded perspective view showing a tenth embodiment of a key switch according to the present invention;
FIGS. 28A and 28B
are schematic sectional views illustrating the operational principle of an actuating member in the key switch of
FIG. 27
;
FIG. 29
is an exploded perspective view showing an eleventh embodiment of a key switch according to the present invention;
FIGS. 30A and 30B
are enlarged perspective views illustrating the operational principle of link members in the key switch of
FIG. 29
;
FIGS. 31A
to
31
C are sectional views illustrating the operational principle of an actuating member in the key switch of
FIG. 29
, taken along line XXXI—XXXI of
FIG. 29
; and
FIGS. 32 and 33
are partially enlarged perspective views illustrating the operational principle of a securing member in the key switch of FIG.
29
.
DESCRIPTION OF THE PREFERRED EMBODIMENT
First Embodiment
Referring now to the drawings, in which same or similar components are denoted by common reference numerals,
FIG. 1
shows a key switch
10
according to a first embodiment of the present invention in an exploded perspective view,
FIG. 2
shows the key switch
10
in an assembled state in section, and
FIG. 3
shows the assembled key switch
10
in another section. The key switch
10
includes a key top
12
with an operation surface
12
a
adapted to be keyed by an operator's finger, a base
14
shaped as a rectangular frame and arranged beneath the key top
12
, a pair of link members
16
,
18
for supporting the key top
12
above a major surface
14
a
of the base
14
and directing or guiding the key top
12
in a vertical or an up-and-down direction, and a membrane sheet
22
provided with a membrane switch
20
and disposed under the base
14
.
The key top
12
is a dish-like member having a generally rectangular profile, and includes a pair of pivot supports
24
and a pair of slide supports
26
spaced from the pivot supports
24
, both provided on an inner surface
12
b
of the key top
12
opposite to the operation surface
12
a
(only one pivot support
24
and only one slide support
26
are shown). The pivot supports
24
are located at a rear end side (a right end side in
FIG. 2
) of the key top
12
and spaced from each other, and the slide supports
26
are located at a front end side (a left end side in
FIG. 2
) of the key top
12
and spaced from each other. Please note that the “front” and the “rear” of the key switch
10
are hereinafter defined in a manner as described above in convenience, but, of course, the “front” and the “rear” in an actual use are not restricted in this definition.
Each of the pivot supports
24
is formed as a small plate uprightly projecting from the inner surface
12
b
of the key top
12
, and includes a bearing hole
24
a
penetrating through the thickness of the plate and a slit
24
b
extending generally perpendicularly to the inner surface
12
b
to communicate with the bearing hole
24
a
. The pivot supports
24
are positioned on the inner surface
12
b
of the key top
12
in such a manner that the bearing holes
24
a
of respective pivot supports
24
are aligned with each other in a penetrating direction thereof.
Each of the slide supports
26
is also formed as a small plate uprightly projecting from the inner surface
12
b
of the key top
12
, and includes a bearing slot
26
a
penetrating through the thickness of the plate and extending generally parallel to the inner surface
12
b
to open to a front side facing away from the pivot support
24
. The slide supports
24
are positioned on the inner surface
12
b
of the key top
12
in such a manner that the bearing slots
26
a
of respective slide supports
26
are aligned with each other in a penetrating direction thereof. The pivot support
24
and the slide support
26
in a corresponding location are substantially aligned with each other in a longitudinal or forward/backward direction on the inner surface
12
b
of the key top
12
.
The base
14
is a frame-like member having a generally rectangular profile, and includes a generally rectangular center opening
15
covered with the key top
12
. The base
14
is provided, along opposed inner edges
14
b
thereof defining the center opening
15
, with a pair of pivot supports
28
and a pair of slide supports
30
spaced from the pivot supports
28
in a longitudinal or forward/backward direction. More particularly, the pivot supports
28
are located at a rear end side of the base
14
and spaced from each other, and the slide supports
30
are located at a front end side of the base
14
and spaced from each other.
Each of the pivot supports
28
is formed as a small plate a part of which projects from the major surface
14
a
of the base
14
, and includes a bearing hole
28
a
penetrating through the thickness of the plate and a slit
28
b
extending generally perpendicularly to the major surface
14
a
to communicate with the bearing hole
28
a
. The pivot supports
28
are positioned on the inner edges
14
b
of the base
14
in such a manner that the bearing holes
28
a
of respective pivot supports
28
are aligned with each other in a penetrating direction thereof.
Each of the slide supports
30
includes an L-shaped wall part projecting from the major surface
14
a
and the inner edge
14
b
of the base
14
, and a bearing slot
30
a
extending generally parallel to the major surface
14
a
is formed inside the wall part. Each bearing slot
30
a
opens to a front side, away from the pivot support
28
, and to a bottom side of the base
14
. The slide supports
30
are positioned on the opposed inner edges
14
b
of the base
14
in such a manner that the bearing slots
30
a
of respective slide supports
30
are aligned and faced with each other. The pivot support
28
and the slide support
30
in a corresponding location are substantially aligned with each other in a longitudinal or forward/backward direction on the inner edges
14
b
of the base
14
.
The pair of link members
16
,
18
are structured as a first link member
16
and a second link member
18
, which have a mutually substantially identical shape, and which are assembled together so as to be provided with a generally X-shape in a side view. Each of the link members
16
,
18
includes two arms
32
extending parallel to each other, and a bar
34
mutually connecting the ends of the arms
32
. Axles
36
are provided on one ends of the arms
32
to mutually coaxially project on the opposite sides to the bar
34
. Axles
38
are provided on the other ends of the arms
32
to mutually coaxially project on the same sides as the axles
36
.
The first and second link members
16
,
18
are arranged to mutually intersect and are pivotably connected relative to each other at an intersection thereof. More particularly, the first and second link members
16
,
18
are pivotably connected with each other by pivots
40
provided at generally longitudinal centers of the respective pair of arms
32
.
The axles
36
formed on one ends of the arms
32
of the first link member
16
are slidably fitted or received in the respective bearing slots
30
a
of the slide supports
30
on the base
14
, and the axles
38
formed on the other ends of the arms
32
of the first link member
16
are pivotably fitted or received in the respective bearing holes
24
a
of the pivot supports
24
on the key top
12
, whereby the first link member
16
is arranged between the key top
12
and the base
14
in such a manner as to be pivotable about the axles
38
on the key top
12
.
The axles
36
formed on the ends of the arms
32
of the second link member
18
are pivotably fitted or received in the respective bearing holes
28
a
of the pivot supports
28
on the base
14
, and the axles
38
formed on the other ends of the arms
32
of the second link member
18
are slidably fitted or received in the respective bearing slots
26
a
of the slide supports
26
on the key top
12
, whereby the second link member
18
is arranged between the key top
12
and the base
14
in such a manner as to be pivotable about the axles
36
on the base
14
.
Therefore, in this embodiment, the axles
36
of the first link member
16
and the axles
38
of the second link member
18
constitute sliding portions of the respective link members
16
,
18
. The first and second link members
16
,
18
are interlocked to each other through the pivots
40
so as to be synchronously pivotable, so that the key top
12
is permitted to be subjected to a parallel displacement in a substantially vertical direction in relation to the major surface
14
a
of the base
14
, while keeping a predetermined posture of the key top
12
wherein the operation surface
12
a
thereof is generally parallel to the major surface
14
a.
The membrane sheet
22
includes two film-shaped circuit boards stacked one on the other with a spacer interposed therebetween, and the membrane switch
20
is structured by conductive contacts formed oppositely on the respective circuit boards. The membrane sheet
22
is stationarily supported on a support plate
42
under the base
14
, and locates the membrane switch
20
at the generally center position in the opening
15
of the base
14
.
On the other hand, as shown in
FIG. 3
, the key top
12
is provided at the generally center position of the inner surface
12
b
thereof, to which the membrane switch
20
of the membrane sheet
22
is substantially aligned in a height direction, with a projection
44
on which a compression coil spring
46
is mounted. The compression coil spring
46
acts as an actuating member or means for selectively opening and closing the membrane switch
20
in connection with a vertical or up-and-down movement of the key top
12
.
The membrane switch
20
is normally kept in a condition where the contacts thereof are opened. When the key top
12
is pushed down by a key-entry operation while being directed by the first and second link members
16
,
18
, the free end of the compression coil spring
46
enters into the center opening
15
of the base
14
and is abutted to the membrane sheet
22
, at a predetermined pushed-down position of the key top
12
, and thus the membrane switch
20
is closed due to an elastic pushing applied through the compression coil spring
46
. When a pushing-down force to the key top
12
is released, the key top
12
returns to an initial position as described later, and thus the compression coil spring
46
clears the membrane sheet
22
to open the membrane switch
20
.
It should be noted that various elastic members, such as a cylindrical rubber block, can be used as an actuating member or means for opening/closing the membrane switch
20
, instead of the compression coil spring
46
. In any case, it is preferred that the actuating member has an elasticity, so as to absorb an impact caused due to the key top
12
upon being pushed down, as far as the easy closure of the membrane switch
20
is not hampered.
The key switch
10
further includes a plate spring
48
or an elastic member, disposed between the base
14
and the first link member
16
, which acts as biasing means for elastically urging upward the key top
12
away from the base
14
. As diagrammatically shown in
FIG. 2
, the plate spring
48
is integrally joined at one end thereof to a front inner edge
14
c
of the base
14
opposite to the bearing slots
30
a
of the slide supports
30
, and is abutted at the other free end thereof to the bar
34
of the first link member
16
. The plate spring
48
acts as a compression spring between the inner edge
14
c
of the base
14
and the bar
34
of the first link member
16
.
When no external force is applied to the key top
12
, the plate spring
48
urges or biases the bar
34
of the first link member
16
toward a backward position spaced from the front inner edge
14
c
of the base
14
and supports the bar
34
in this position, as well as, through the first link member
16
and the second link member
18
interlocked thereto, urges or biases the key top
12
toward the initial position vertically upwardly away from the base
14
and supports the key top
12
in this position (see FIG.
2
).
When the key top
12
is pushed down by a key-entry operation, the axles
36
of the first link member
16
slidingly move frontward along the bearing slots
30
a
of the slide supports
30
of the base
14
and, simultaneously, the bar
34
shifts toward the front inner edge
14
c
of the base
14
. During this operation, the plate spring
48
is deformed while exerting biasing or elastic restoring force to the bar
34
(i.e., a loading portion) of the first link member
16
in a direction substantially orthogonal to the pushing-down direction of the key top
12
. When the pushing-down force to the key top
12
is released, the plate spring
48
elastically restores to return the key top
12
to the initial position through the first and second link members
16
,
18
. In this respect, the plate spring
48
is a linear characteristics spring of a simple structure, and thus exerts the biasing force onto the bar
34
, which assumes a linear relationship with the shifting amount or displacement of the bar
34
.
According to the key switch
10
, it is possible to establish key-entry operating properties with non-linear characteristics, similar to that established by a dome-shaped elastic actuating member in the conventional key switch, by using the plate spring
48
with linear characteristics. This is caused by the unique arrangement of the plate spring
48
which applies the biasing force to the first link member
16
in a direction substantially orthogonal to the pushing-down direction of the key top
12
. The operational principle of the plate spring
48
is described below with reference to
FIGS. 4A
to
4
C.
FIG. 4A
diagrammatically shows a constitution in which a link having a length “L” (the first link member
16
) is obliquely arranged and a compression spring (the plate spring
48
) is joined to the bottom end (the bar
34
) of the link, and in which the top end (the axles
38
) of the link is pushed down in a vertical downward direction. In this constitution, the reaction force “f” of the compression spring is applied to the bottom end of the link in a horizontal direction, in connection with the pushing-down force “F” applied to the top end of the link in the vertical downward direction. Please note here that:
F=f·tan θ (θ is a link angle);
f=k·x (k is a spring constant, x is a horizontal displacement of link bottom end);
X=L (sin θ
0
−sin θ) (X is a vertical displacement of link top end, θ
0
is a link angle at f=0); and
x=−L·(cos θ
0
−cos θ).
The inventors of the present application numerically analyzed the parameter 0≦θ≦45° in accordance with the above principles, supposing that θ
0
=45°, L=5 mm, k=120 gf/mm, and determined the relationship between the vertical displacement of the link top end and the pushing-down force. The results thereof is shown in FIG.
4
B. As illustrated, a characteristic curve was obtained, wherein, at the instant when the vertical displacement “X” of the link top end exceeds a predetermined value, the pushing-down force “F”, which has been gradually increased until that time, is reduced to the contrary.
Consequently, according to the key switch
10
, it is possible to establish a key-entry operating properties similar to that established in the conventional key switch using a dome-shaped elastic actuating member, wherein, at the instant when the pushed-down displacement of the key top
12
exceeds a predetermined value, the biasing force, which has been gradually increased until that time, is sharply reduced. In an actual operation, the synthetic characteristic curve is obtained, as shown by a solid line in
FIG. 4C
, since the reaction force “R” due to the compression coil spring
46
acting as the actuating member for the membrane switch
20
is additionally exerted, after the key top
12
passes the predetermined pushed-down position.
As described above, in the key switch
10
, the key-top biasing function and the membrane-switch actuating function, both included in the conventional dome-shaped elastic actuating member, are assigned to the plate spring
48
and the compression coil spring
46
, respectively, so that the dome-shaped elastic actuating member is omitted. The plate spring
48
is not placed between the key top
12
and the membrane sheet
22
in the height direction of the key switch
10
, which is different from the conventional dome-shaped elastic actuating member, and which makes it possible to further reduce the entire height of the key switch
10
upon both the inoperated and operated conditions thereof.
In this respect, it is only necessary for the compression coil spring
46
to come into contact with the membrane switch
20
when the key top
12
reaches the predetermined position, so that the compression coil spring
46
hardly affects in itself the height of the key switch
10
. Further, the plate spring
48
can establish the key-entry operating properties with non-linear characteristics, similar to that established by the conventional dome-shaped elastic actuating member, due to the arrangement of the plate spring
48
, despite the plate spring
48
having a simple, linear characteristic spring, and therefore it is possible to reduce the production cost for the key switch
10
without deteriorating the operational feeling thereof.
In the above embodiment, the plate spring
48
is integrally joined to the inner edge
14
c
defining the center opening
15
of the base
14
, but a plate spring
50
may be used as a modification, which is integrally joined to the first link member
16
, as shown in FIG.
5
. In this modification, the plate spring
50
is integrally joined at one end thereof to the neighborhood of the bar
34
of the first link member
16
, and is abutted at the other free end thereof to the inner edge
14
c
of the base
14
. It will be understood that this structure can also provide effects equivalent to those of the first embodiment.
The plate spring
48
may be formed integrally with the base
14
, both made from the same resinous material or the same metal. Alternatively, the metal plate spring
48
may be integrally joined to the resinous base
14
through an insert molding process. Also, the plate spring
50
may be formed integrally with the first link member
16
, both made from the same resinous material or the same metal. Alternatively, the metal plate spring
50
may be integrally joined to the resinous first link member
16
through an insert molding process.
FIG. 5
shows, by a broken line, an embedded portion
50
a
of the plate spring
50
joined to the first link member
16
through the insert molding process.
The other elastic members having linear characteristics, such as a compression coil spring, an extension coil spring, etc., may be used instead of the plate spring
48
,
50
. Further, in the above embodiment, the plate spring
48
,
50
is arranged between the base
14
and the loading portion or bar
34
of the first link member
16
, but, in addition or instead, the elastic member having linear characteristics, such as a plate spring, may be disposed between the key top
12
and, e.g., the sliding portion or axle
38
of the second link member
18
.
Second Embodiment
FIGS. 6 and 7
show a key switch
60
according to a second embodiment of the present invention. The key switch
60
includes a key top
62
with an operation surface
62
a
adapted to be keyed by an operator's finger, a base
64
shaped as a rectangular frame and arranged beneath the key top
62
, a pair of link members
66
,
68
for supporting the key top
62
above a major surface
64
a
of the base
64
and directing or guiding the key top
62
in a vertical or going up and down direction, a membrane sheet
22
provided with a membrane switch
20
and disposed under the base
64
, and a support plate
42
for stationarily supporting the membrane sheet
22
. The membrane switch
20
, the membrane sheet
22
and the support plate
42
have the same structures as those in the key switch
10
of the first embodiment, and thus a detailed description thereof is not repeated.
The key top
62
is a dish-like member having a generally rectangular profile, and includes two pairs of pivot supports
70
, one pair being spaced from the other, on an inner surface
62
b
of the key top
62
opposite to the operation surface
62
a
(only two pivot supports
70
are shown). The pivot supports
70
of respective pairs are located at a front end side (a left end side in
FIG. 7
) and a rear end side (a right end side in
FIG. 7
) of the key top
62
and spaced from each other in each pair. Please note that the “front” and the “rear” of the key switch
60
are hereinafter defined in a manner as described above in convenience, but, of course, the “front” and the “rear” in an actual use are not restricted in this definition.
Each of the pivot supports
70
is formed as a small plate uprightly projecting from the inner surface
62
b
of the key top
62
, and includes a bearing hole
70
a
penetrating through the thickness of the plate and a slit
70
b
extending generally perpendicularly to the inner surface
62
b
to communicate with the bearing hole
70
a
. Two pivot supports
70
of each pair are positioned on the inner surface
62
b
of the key top
62
in such a manner that the bearing holes
70
a
of these pivot supports
70
are aligned with each other in a penetrating direction thereof. The pivot supports
70
in a corresponding location between two pairs are substantially aligned with each other in a longitudinal or forward/backward direction on the inner surface
62
b
of the key top
62
.
The key top
62
is also provided generally at the center position of the inner surface
62
b
thereof, to which the membrane switch
20
of the membrane sheet
22
is substantially aligned, in a height direction, with a projection and a compression coil spring mounted thereon (not shown), which are respectively similar to the projection
44
and the compression coil spring
46
in the first embodiment. The compression coil spring acts as an elastic actuating member for selectively opening and closing the membrane switch
20
in connection with a vertical or up-and-down movement of the key top
62
.
The base
64
is a frame-like member having a generally rectangular profile, and includes a generally rectangular center opening
65
covered by the key top
62
. The base
64
is provided, along opposed inner edges
64
b
thereof defining the center opening
65
, with two pairs of slide supports
72
, one pair being spaced from the other in a longitudinal or forward/backward direction, and two slide supports
72
in each pair being spaced from each other.
Each of the slide supports
72
disposed adjacent to the front end of the base
64
includes an L-shaped wall part projecting from the major surface
64
a
and the inner edge
64
b
of the base
64
, and a bearing slot
72
a
extending generally parallel to the major surface
64
a
is formed inside the wall part. These front bearing slots
72
a
open to a front side, away from the rear slide supports
72
, and to a bottom side of the base
64
. Each of the slide supports
72
disposed adjacent to the rear end of the base
64
also includes an L-shaped wall part projecting from the major surface
64
a
and the inner edge
64
b
of the base
64
, and a bearing slot
72
a
extending generally parallel to the major surface
64
a
is formed inside the wall part. These rear bearing slots
72
a
open to a rear side, away from the front slide supports
72
, and to a bottom side of the base
64
.
Two slide supports
72
of each pair are positioned on the opposed inner edges
64
b
of the base
64
in such a manner that the bearing slots
72
a
of respective slide supports
72
are aligned and faced with each other. Also, the slide supports
72
in a corresponding location between two pairs are substantially aligned with each other in a longitudinal or forward/backward direction on the inner edges
64
b
of the base
64
.
The pair of link members
66
,
68
are structured as a first link member
66
and a second link member
68
, which have a mutually substantially identical shape, and which are assembled together so as to be provided with a generally X-shape in a side view. Each of the link members
66
,
68
includes two arms
74
extending parallel to each other, and a bar
76
mutually connecting one ends of the arms
74
. Axles
78
are provided on one ends of the arms
74
to mutually coaxially project on the opposite sides to the bar
76
. Axles
80
are provided on the other ends of the arms
74
to mutually coaxially project on the same sides as the axles
78
.
The first and second link members
66
,
68
are arranged to mutually intersect, and are pivotably and slidably connected relative to each other at an intersection thereof. More particularly, the first and second link members
66
,
68
are pivotably and slidably connected with each other by respective interengagements between pivots
82
provided at generally longitudinal centers of one arms
74
of respective link members and elliptic holes
84
provided at generally longitudinal centers of the other arms
74
of respective link members.
The axles
78
formed on one ends of the arms
74
of the first link member
66
are slidably fitted or received in the respective bearing slots
72
a
of the front slide supports
72
on the base
64
, and the axles
80
formed on the other ends of the arms
74
of the first link member
66
are pivotably fitted or received in the respective bearing holes
70
a
of the rear pivot supports
70
on the key top
62
, whereby the first link member
66
is arranged between the key top
62
and the base
64
in such a manner as to be pivotable about the axles
80
on the key top
62
.
The axles
78
formed on one ends of the arms
74
of the second link member
68
are slidably fitted or received in the respective bearing slots
72
a
of the rear slide supports
72
on the base
64
, and the axles
80
formed on the other ends of the arms
74
of the second link member
68
are pivotably fitted or received in the respective bearing holes
70
a
of the front pivot supports
70
on the key top
62
, whereby the second link member
68
is arranged between the key top
62
and the base
64
in such a manner as to be pivotable about the axles
80
on the key top
62
.
Therefore, in this embodiment, the axles
78
of the first link member
66
and the axles
78
of the second link member
68
constitute sliding portions of the respective link members
66
,
68
. The first and second link members
66
,
68
are interlocked to each other through the slidable interengagements between the pivots
82
and the elliptic holes
84
so as to be synchronously pivotable, so that the key top
62
is permitted to be subjected to a parallel displacement in a substantially vertical direction in relation to the major surface
64
a
of the base
64
, while keeping a predetermined posture of the key top
62
wherein the operation surface
62
a
thereof is generally parallel to the major surface
64
a.
The key switch
60
further includes a pair of plate springs
86
or elastic members, disposed between the base
64
and the first and second link members
66
,
68
, which act as biasing means for elastically urging upward the key top
62
away from the base
64
. As diagrammatically shown in
FIG. 7
, one plate spring
86
is integrally joined at one end thereof to a front inner edge
64
c
of the base
64
opposite to the bearing slots
72
a
of the front slide supports
72
, and is abutted at the other free end thereof to the bar
76
of the first link member
66
. The other plate spring
86
is integrally joined at one end thereof to a rear inner edge
64
c
of the base
64
opposite to the bearing slots
72
a
of the rear slide supports
72
, and is abutted at the other free end thereof to the bar
76
of the second link member
68
. The plate springs
86
act as compression springs between the inner edges
64
c
of the base
64
and the bars
76
of the first and second link members
66
,
68
, respectively.
When no external force is applied to the key top
62
, the plate springs
86
urge or bias the bars
76
of the first and second link members
66
,
68
toward backward and forward positions spaced from the front and rear inner edges
64
c
of the base
64
, respectively, and support the bars
76
in these positions, as well as, through the mutually interlocked first and second link members
66
,
68
, urging or biasing the key top
62
toward the initial position vertically upwardly away from the base
64
and supporting the key top
62
in this position (see FIG.
7
).
When the key top
62
is pushed down by a key-entry operation, the axles
78
of the first and second link members
66
,
68
slidingly move frontward and rearward along the bearing slots
72
a
of the front and rear slide supports
72
of the base
64
, respectively, and, simultaneously, the bars
76
shift toward the front and rear inner edges
64
c
of the base
64
. During this operation, the plate springs
86
are deformed while exerting biasing or elastic restoring force to the respective bars
76
(i.e., loading portions) of the first and second link members
66
,
68
in a direction substantially orthogonal to the pushing-down direction of the key top
62
.
When the pushing-down force to the key top
62
is released, the plate springs
86
elastically restore to return the key top
62
to the initial position through the first and second link members
66
,
68
. In this respect, each of the plate springs
86
is a linear characteristic spring of a simple structure, and thus exerts the biasing force, assuming a linear relationship with the shifting amount or displacement of the bar
76
, onto each of the bars
76
of the first and second link members
66
,
68
. Preferably, the plate springs
86
have shapes and characteristics identical to each other.
According to the key switch
60
, it is possible to establish a key-entry operating properties with non-linear characteristics, similar to that established by a dome-shaped elastic actuating member in the conventional key switch, by using two plate springs
86
with linear characteristics. This is caused by the unique arrangements of these plate springs
86
which apply the biasing force to the first and second link members
66
,
68
in a direction substantially orthogonal to the pushing-down direction of the key top
62
. The operational principle of the key switch
60
is substantially the same as that described concerning the first embodiment and is not repeated.
As described above, in the key switch
60
, a dome-shaped elastic actuating member in the conventional key switch is omitted, and instead, two plate springs
86
, which are not placed between the key top
62
and the membrane sheet
22
in the height direction of the key switch
60
, are used as key top biasing means, so that it is made possible to significantly reduce the entire height of the key switch
60
upon both the non-operated and operated conditions thereof. Further, each plate spring
86
can establish the key-entry operating properties with non-linear characteristics, similar to that established by the conventional dome-shaped elastic actuating member, due to the arrangement of the plate spring
86
, despite that the plate spring
86
being a simple, linear characteristic spring, and therefore it is possible to reduce the production cost for the key switch
60
without deteriorating the operational feeling thereof.
Moreover, in the key switch
60
, two plate springs
86
cooperate to bear the pushing-down force applied to the key top
62
, so that the stress applied to each plate spring
86
can be attenuated. Accordingly, it is possible to prevent the plate spring
86
from being damaged, and to ease the design of the plate spring
86
.
In the above second embodiment, the plate springs
86
are integrally joined to the inner edges
64
c
defining the center opening
65
of the base
64
, but plate springs
88
may be used as a modification which are integrally joined to the first and second link members
66
,
68
, as shown in FIG.
8
. In this modification, the plate springs
88
are integrally joined at one ends thereof to the neighborhood of the respective bars
76
of the first and second link members
66
,
68
, and are abutted at the other free ends thereof to the front and rear inner edges
64
c
of the base
64
. It will be understood that this structure can also provide the effects equivalent to those of the embodiment shown in FIG.
6
. Also, in this modification, the first and second link members
66
,
68
may have a mutually identical structure, and thus it is possible to prevent the number of parts from being increased.
The plate springs
86
may be formed integrally with the base
64
, both made from the same resinous material or the same metal. Alternatively, the metal plate springs
86
may be integrally joined to the resinous base
64
through an insert molding process. Also, the plate springs
88
may be formed integrally with the first and second link members
66
,
68
, both made from the same resinous material or the same metal. Alternatively, the metal plate springs
88
may be integrally joined to the resinous first and second link members
66
,
68
through an insert molding process.
FIG. 8
shows, by a broken line, an embedded portion
88
a
of the plate spring
88
joined to the first link member
66
through the insert molding process. Further,
FIG. 9
shows one example of first and second link members
66
,
68
both provided with plate springs
88
integrally formed therewith from resinous material.
The other elastic members having linear characteristics, such as a compression coil spring, an extension coil spring, etc., may be used instead of the plate springs
86
,
88
. Further, in the above embodiment, two plate springs
86
,
88
are arranged, one for each, between the base
64
and the respective loading portions or bars
76
of the first and second link members
66
,
68
, but instead, the elastic member having linear characteristics, such as a plate spring, may be disposed only between the base
64
and either one of the bars
76
of the first and second link members
66
,
68
. Alternatively, both the plate spring
86
joined to the base
64
and the plate spring
88
joined to the first or second link member
66
,
68
may be incorporated together in the key switch
60
.
Third Embodiment
FIGS. 10 and 11
show a key switch
90
according to a third embodiment of the present invention. The key switch
90
includes a key top
92
with an operation surface
92
a
adapted to be keyed by an operator's finger, a base
94
shaped as a rectangular frame and arranged beneath the key top
92
, a pair of link members
96
,
98
for supporting the key top
92
above a major surface
94
a
of the base
94
and directing or guiding the key top
92
in a vertical or going up and down direction, a membrane sheet
22
provided with a membrane switch
20
and disposed under the base
94
, and a support plate
42
for stationarily supporting the membrane sheet
22
. The membrane switch
20
, the membrane sheet
22
and the support plate
42
have the same structures as those in the key switch
10
of the first embodiment, and thus a detailed description thereof is not repeated.
The key top
92
is a dish-like member having a generally rectangular profile, and includes two pairs of pivot supports
100
, both pairs being disposed side-by-side in a forward/backward direction (a leftward/rightward direction in
FIG. 11
) on an inner surface
92
b
of the key top
92
opposite to the operation surface
92
a
(only two pivot supports
100
are shown). The pivot supports
100
of respective pairs are located at a generally center of the key top
92
and spaced from each other in each pair. Please note that the “front” and the “rear” of the key switch
90
are hereinafter defined in a manner as described above in convenience, but, of course, the “front” and the “rear” in an actual use are not restricted in this definition.
Each of the pivot supports
100
is formed as a small plate uprightly projecting from the inner surface
92
b
of the key top
92
, and includes a bearing hole
100
a
penetrating through the thickness of the plate and a slit
100
b
extending generally perpendicularly to the inner surface
92
b
to communicate. with the bearing hole
100
a
. Two pivot supports
100
of each pair are positioned on the inner surface
92
b
of the key top
92
in such a manner that the bearing holes
100
a
of these pivot supports
100
are aligned with each other in a penetrating direction thereof. The pivot supports
100
in a corresponding location between two pairs are substantially aligned with each other in a longitudinal or forward/backward direction on the inner surface
92
b
of the key top
92
.
The key top
92
is also provided at the generally center position of the inner surface
92
b
thereof, to which the membrane switch
20
of the membrane sheet
22
is substantially aligned in a height direction, with a projection and a compression coil spring mounted thereon (not shown), which are respectively similar to the projection
44
and the compression coil spring
46
in the first embodiment. The compression coil spring acts as an elastic actuating member for selectively opening and closing the membrane switch
20
in connection with a vertical or going up and down movement of the key top
92
.
The base
94
is a frame-like member having a generally rectangular profile, and includes a generally rectangular center opening
95
covered with the key top
92
. The base
94
is provided, along opposed inner edges
94
b
thereof defining the center opening
95
, with two pairs of slide supports
102
, one pair being spaced from the other in a longitudinal or forward/backward direction, and two slide supports
102
in each pair being spaced from each other.
Each of the slide supports
102
disposed adjacent to the front end of the base
94
includes an L-shaped wall part projecting from the major surface
94
a
and the inner edge
94
b
of the base
94
, and a bearing slot
102
a
extending generally parallel to the major surface
94
a
is formed inside the wall part. These front bearing slots
102
a
open to a front side, away from the rear slide supports
102
, and to a bottom side of the base
94
. Each of the slide supports
102
disposed adjacent to the rear end of the base
94
also includes an L-shaped wall part projecting from the major surface
94
a
and the inner edge
94
b
of the base
94
, and a bearing slot
102
a
extending generally parallel to the major surface
94
a
is formed inside the wall part. These rear bearing slots
102
a
open to a rear side, away from the front slide supports
102
, and to a bottom side of the base
94
.
Two slide supports
102
of each pair are positioned on the opposed inner edges
94
b
of the base
94
in such a manner that the bearing slots
102
a
of respective slide supports
102
are aligned and faced with each other. Also, the slide supports
102
in a corresponding location between two pairs are substantially aligned with each other in a longitudinal or forward/backward direction on the inner edges
94
b
of the base
94
.
The pair of link members
96
,
98
are structured as a first link member
96
and a second link member
98
, which have a mutually substantially identical shape, and which are assembled together so as to be provided with a generally reverse V-shape in a side view. Each of the link members
96
,
98
includes two arms
104
extending parallel to each other, and a bar
106
mutually connecting the ends of the arms
104
. Axles
108
are provided on the ends of the arms
104
to mutually coaxially project on the opposite sides to the bar
106
. Axles
110
are provided on the other ends of the arms
104
to mutually coaxially project on the same sides as the axles
108
.
The first and second link members
96
,
98
are meshed with each other at a toothed end of each link members
96
,
98
. More particularly, the first and second link members
96
,
98
are pivotably connected with each other by intermeshings between one tooth
112
projecting from the distal ends, near the axles
110
, of one arms
104
of respective link members and two teeth
114
projecting from the distal ends, near the axles
110
, of the other arms
104
of respective link members.
The axles
108
formed on one ends of the arms
104
of the first link member
96
are slidably fitted or received in the respective bearing slots
102
a
of the front slide supports
102
on the base
94
, and the axles
110
formed on the other ends of the arms
104
of the first link member
96
are pivotably fitted or received in the respective bearing holes
100
a
of the front pivot supports
100
on the key top
92
, whereby the first link member
96
is arranged between the key top
92
and the base
94
in such a manner as to be pivotable about the axles
110
on the key top
92
.
The axles
108
formed on one ends of the arms
104
of the second link member
98
are slidably fitted or received in the respective bearing slots
102
a
of the rear slide supports
102
on the base
94
, and the axles
110
formed on the other ends of the arms
104
of the second link member
98
are pivotably fitted or received in the respective bearing holes
100
a
of the rear pivot supports
100
on the key top
92
, whereby the second link member
98
is arranged between the key top
92
and the base
94
in such a manner as to be pivotable about the axles
110
on the key top
92
.
Therefore, in this embodiment, the axles
108
of the first link member
96
and the axles
108
of the second link member
98
constitute sliding portions of the respective link members
96
,
98
. The first and second link members
96
,
98
are interlocked to each other through the intermeshings between the one tooth
112
and the two teeth
114
so as to be synchronously pivotable, so that the key top
92
is permitted to be subjected to a parallel displacement in a substantially vertical direction in relation to the major surface
94
a
of the base
94
, while keeping a predetermined posture of the key top
92
wherein the operation surface
92
a
thereof is generally parallel to the major surface
94
a.
The key switch
90
further includes a pair of plate springs
116
or elastic members, disposed between the base
94
and the first and second link members
96
,
98
, which act as biasing means for elastically urging upward the key top
92
away from the base
94
. As diagrammatically shown in
FIG. 11
, one plate spring
116
is integrally joined at one end thereof to a front inner edge
94
c
of the base
94
opposite to the bearing slots
102
a
of the front slide supports
102
, and is abutted at the other free end thereof to the bar
106
of the first link member
96
. The other plate spring
116
is integrally joined at one end thereof to a rear inner edge
94
c
of the base
94
opposite to the bearing slots
102
a
of the rear slide supports
102
, and is abutted at the other free end thereof to the bar
106
of the second link member
98
. The plate springs
116
act as compression springs between the inner edges
94
c
of the base
94
and the bars
106
of the first and second link members
96
,
98
, respectively.
When no external force is applied to the key top
92
, the plate springs
116
urge or bias the bars
106
of the first and second link members
96
,
98
toward backward and forward positions spaced from the front and rear inner edges
94
c
of the base
94
, respectively, and support the bars
106
in these positions, as well as, through the mutually interlocked first and second link members
96
,
98
, urging or biasing the key top
92
toward the initial position vertically upwardly away from the base
94
and supporting the key top
92
in this position (see FIG.
11
).
When the key top
92
is pushed down by a key-entry operation, the axles
108
of the first and second link members
96
,
98
slidingly move frontward and rearward along the bearing slots
102
a
of the front and rear slide supports
102
of the base
94
, respectively, and, simultaneously, the bars
106
shift toward the front and rear inner edges
94
c
of the base
94
. During this operation, the plate springs
116
are deformed while exerting biasing or elastic restoring force to the respective bars
106
(i.e., loading portions) of the first and second link members
96
,
98
in a direction substantially orthogonal to the pushing-down direction of the key top
92
.
When the pushing-down force to the key top
92
is released, the plate springs
116
elastically restore to return the key top
92
to the initial position through the first and second link members
96
,
98
. In this respect, each of the plate springs
116
is a linear characteristic spring of a simple structure, and thus exerts the biasing force, assuming a linear relationship with the shifting amount or displacement of the bar
106
, onto each of the bars
106
of the first and second link members
96
,
98
. Preferably, the plate springs
116
have shapes and characteristics identical to each other.
According to the key switch
90
, it is possible to establish a key-entry operating properties with non-linear characteristics, similar to that established by a dome-shaped elastic actuating member in the conventional key switch, by using two plate springs
116
with linear characteristics. This is caused by the unique arrangements of these plate springs
116
which apply the biasing force to the first and second link members
96
,
98
in a direction substantially orthogonal to the pushing-down direction of the key top
92
. The operational principle of the key switch
90
is substantially the same as that described concerning the first embodiment, and thus is not repeated.
As described above, in the key switch
90
, a dome-shaped elastic actuating member in the conventional key switch is omitted, and instead, two plate springs
116
, which are not placed between the key top
92
and the membrane sheet
22
in the height direction of the key switch
90
, are used as key top biasing means, so that it is made possible to significantly reduce the entire height of the key switch
90
upon both the inoperated and operated conditions thereof. Further, each plate spring
116
can establish the key-entry operating properties with non-linear characteristics, similar to that established by the conventional dome-shaped elastic actuating member, due to the arrangement of the plate spring
116
, despite the plate spring
116
being a simple, linear characteristic spring, and therefore it is possible to reduce the production cost for the key switch
90
without deteriorating the operational feeling thereof.
Moreover, in the key switch
90
, two plate springs
116
cooperate to bear the pushing-down force applied to the key top
92
, so that the stress applied to each plate spring
116
can be attenuated. Accordingly, it is possible to prevent the plate spring
116
from being damaged, and to ease the design of the plate spring
116
.
In the above third embodiment, the plate springs
116
are integrally joined to the inner edges
94
c
defining the center opening
95
of the base
94
, but plate springs
118
may be modified and integrally joined to the first and second link members
96
,
98
, as shown in FIG.
12
. In this modification, the plate springs
118
are integrally joined at one ends thereof in the neighborhood of the respective bars
106
of the first and second link members
96
,
98
, and are abutted at the other free ends thereof to the front and rear inner edges
94
c
of the base
94
. It will be understood that this structure can also provide the effects equivalent to those of the embodiment shown in FIG.
10
. Also, in this modification, the first and second link members
96
,
98
may have a mutually identical structure, and thus it is possible to prevent the number of parts from being increased.
The plate springs
116
may be formed integrally with the base
94
, both made from the same resinous material or the same metal. Alternatively, the metal plate springs
116
may be integrally joined to the resinous base
94
through an insert molding process. Also, the plate springs
118
may be formed integrally with the first and second link members
96
,
98
, both made from the same resinous material or the same metal. Alternatively, the metal plate springs
118
may be integrally joined to the resinous first and second link members
96
,
98
through an insert molding process.
The other elastic members having linear characteristics, such as a compression coil spring, an extension coil spring, etc., may be used instead of the plate springs
116
,
118
. Further, in the above embodiment, two plate springs
116
,
118
are arranged, one for each, between the base
94
and the respective loading portions or bars
106
of the first and second link members
96
,
98
, but instead, the elastic member having linear characteristics, such as a plate spring, may be disposed only between the base
94
and either one of the bars
106
of the first and second link members
96
,
98
. Alternatively, both the plate spring
116
joined to the base
94
and the plate spring
118
joined to the first or second link member
96
,
98
may be incorporated together in the key switch
90
.
Fourth Embodiment
FIG. 13
shows a key switch
120
according to a fourth embodiment of the present invention. The key switch
120
is preferably used in a relatively thin keyboard having an improved portability, in which the key top of each key switch is held in an initial projecting position for a key-entry operation during the operating state of the keyboard, while the key top is positively displaced to a retracted position lower than the initial position during the non-operating (or carrying) state of the keyboard.
The key switch
120
includes a key top
62
with an operation surface
62
a
adapted to be keyed by an operator's finger, a fixed base element
122
shaped as a rectangular frame and arranged beneath the key top
62
, a pair of link members
66
,
68
for supporting the key top
62
above a major surface
122
a
of the base element
122
and directing or guiding the key top
62
in a vertical or up-and-down direction, a movable base element
124
shaped as a rectangular frame and arranged under the fixed base element
122
, a membrane sheet
22
provided with a membrane switch
20
and disposed under the movable base element
124
, and a support plate
42
for stationary supporting the membrane sheet
22
. The key top
62
, the link members
66
,
68
, the membrane switch
20
, the membrane sheet
22
and the support plate
42
have the same structures as those in the key switch
60
of the second embodiment shown in
FIG. 6
, and thus the detailed description thereof is not repeated.
The fixed base element
122
is a frame-like member having a generally rectangular profile, and includes a generally rectangular center opening
126
covered with the key top
62
. The fixed base element
122
is provided, along opposed inner edges
122
b
thereof defining the center opening
126
, with two pairs of slide supports
128
, one pair being spaced from the other in a longitudinal or forward/backward direction, and two slide supports
128
in each pair being spaced from each other.
Each of the slide supports
128
disposed adjacent to the front end of the fixed base element
122
includes an L-shaped wall part projecting from the major surface
122
a
and the inner edge
122
b
of the fixed base element
122
, and a bearing slot
128
a
extending generally parallel to the major surface
122
a
is formed inside the wall part. These front bearing slots
128
a
open to a front side, away from the rear slide supports
128
, and to a bottom side of the fixed base element
122
. Each of the slide supports
128
disposed adjacent to the rear end of the fixed base element
122
also includes an L-shaped wall part projecting from the major surface
122
a
and the inner edge
122
b
of the fixed base element
122
, and a bearing slot
128
a
extending generally parallel to the major surface
122
a
is formed inside the wall part. These rear bearing slots
128
a
open to a rear side, away from the front slide supports
128
, and to a bottom side of the fixed base element
122
.
Two slide supports
128
of each pair are positioned on the opposed inner edges
122
b
of the fixed base element
122
in such a manner that the bearing slots
128
a
of respective slide supports
128
are aligned and faced with each other. Also, the slide supports
128
in a corresponding location between two pairs are substantially aligned with each other in a longitudinal or forward/backward direction on the inner edges
122
b
of the fixed base element
122
.
The movable base element
124
is a frame-like member having a generally rectangular profile, and includes a generally rectangular center opening
130
substantially corresponding to the center opening
126
of the fixed base element
122
. The movable base element
124
cooperates with the fixed base element
122
to serve as a base of the key switch
120
. The movable base element
124
can be shifted in a forward/backward direction (shown by an arrow A) of the key switch
120
between the fixed base element
122
and the membrane sheet
22
.
The key switch
120
further includes a pair of plate springs
132
,
134
or elastic members, disposed between the fixed base element
122
and the first and second link members
66
,
68
, which act as biasing means for elastically urging upward the key top
62
away from the fixed base element
122
. One plate spring
132
is integrally joined at one end thereof to a rear inner edge
122
c
of the fixed base element
122
opposite to the bearing slots
128
a
of the rear slide supports
128
, and is abutted at the other free end thereof to the bar
76
of the second link member
68
. The other plate spring
134
is integrally joined at one end thereof to an inner edge
130
a
of the movable base element
124
defining the center opening
130
, and is abutted at the other free end thereof to the bar
76
of the first link member
66
while extending through the center opening
126
of the fixed base element
122
.
The plate spring
134
joined to the movable base element
124
is located close to the front inner edge
122
c
of the fixed base element
122
opposite to the bearing slots
128
a
of the front slide supports
128
. The plate springs
132
,
134
act as compression springs between the inner edges
122
c
of the fixed base element
122
and the bars
76
of the first and second link members
66
,
68
, respectively.
As described above, in the fourth embodiment, the plate spring
134
disposed at the front side of the key switch
120
can be shifted together with the movable base element
124
in the forward/backward direction in relation to the fixed base element
122
, which is a different structure from the key switch
60
of the second embodiment shown in FIG.
6
. Consequently, in the key switch
120
, it is possible to change the distance between the plate springs
132
,
134
, and thereby to displace the key top
62
between an initial projecting position and a retracted position during a non-operating condition, as described below.
When the movable base element
124
is located at the rear limit of movement thereof, the plate springs
132
,
134
act in the same manner as the plate springs
86
shown in
FIG. 7
to maintain the key switch
120
in a condition for a key-entry operation. That is, when no external force is applied to the key top
62
, the plate springs
132
,
134
urge or bias the bars
76
of the first and second link members
66
,
68
toward backward and forward positions spaced from the front and rear inner edges
122
c
of the fixed base element
122
, respectively, and support the bars
106
in these positions, as well as, through the mutually interlocked first and second link members
66
,
68
, urge or bias the key top
62
toward the initial position vertically upwardly away from the fixed base element
122
and support the key top
62
in this position.
Also, when the key top
62
is pushed down by a key-entry operation, the axles
78
of the first and second link members
66
,
68
slidingly move frontward and rearward along the bearing slots
128
a
of the front and rear slide supports
128
of the fixed base element
122
, respectively, and, simultaneously, the bars
76
shift toward the front and rear inner edges
122
c
of the fixed base element
122
. During this operation, the plate springs
132
,
134
are deformed while exerting biasing or elastic restoring force to the respective bars
76
(i.e., loading portions) of the first and second link members
66
,
68
in a direction substantially orthogonal to the pushing-down direction of the key top
62
.
When the pushing-down force to the key top
62
is released, the plate springs
132
,
134
elastically restore to return the key top
62
to the initial position through the first and second link members
66
,
68
. In this respect, each of the plate springs
132
,
134
is a linear characteristic spring of a simple structure, and thus exerts the biasing force, assuming a linear relationship with the shifting amount or displacement of the bar
76
, onto each of the bars
76
of the first and second link members
66
,
68
. Preferably, the plate springs
132
,
134
have shapes and characteristics identical to each other.
According to the key switch
120
, it is possible to establish a key-entry operating properties with non-linear characteristics, similar to that established by a dome-shaped elastic actuating member in the conventional key switch, by using two plate springs
132
,
134
with linear characteristics. This is caused by the unique arrangements of these plate springs
132
,
134
which apply the biasing force to the first and second link members
66
,
68
in a direction substantially orthogonal to the pushing-down direction of the key top
62
. The operational principle of the key switch
120
is substantially the same as that described concerning the first embodiment, and thus is not repeated.
Then, the plate spring
134
is shifted frontward, by an actuating mechanism (not shown), together with the movable base element
124
to be located at the front limit of movement thereof. When the plate spring
134
, which serves to support the first link member
66
, is shifted frontward, the first and second link members
66
,
68
are automatically folded-up due to their weight and of key top
62
. As a result, the key top
62
is displaced to the retracted position lower than the initial position. In the retracted position, both the plate springs
132
,
134
are kept free of any substantial elastic deformation.
The height of the key top
62
at the retracted position depends on the location of the front limit of movement of the movable base element
124
. Therefore, in order to sufficiently lower the height of the key top
62
at the retracted position, it is preferred that the components of key switch
120
are dimensioned so that a sufficient gap is defined between the plate spring
134
and the front inner edge
122
c
of the fixed base element
122
when the movable base element
124
is placed at the rear limit of movement. Alternatively, the part of the fixed base element
122
including the front inner edge
122
c
may be removed or cut out, whereby the limit of movement of the movable base element
124
and thus the plate spring
134
can be enlarged frontward. Further, it is desired that, when the key top
62
is in the retracted position, the compression coil spring, provided on the inner surface
62
b
of the key top
62
as a membrane switch actuating member, is positioned so as not to push the membrane sheet
22
.
As described above, in the key switch
120
, a dome-shaped elastic actuating member in the conventional key switch is omitted, and instead, two plate springs
132
,
134
, which are not placed between the key top
62
and the membrane sheet
22
in the height direction of the key switch
120
, are used as key top biasing means, so that it is made possible to significantly reduce the entire height of the key switch
120
upon both the inoperated and operated conditions thereof. Further, each plate spring
132
,
134
can establish the key-entry operating properties with non-linear characteristics, similar to that established by the conventional dome-shaped elastic actuating member, due to the arrangement of the plate spring
132
,
134
, despite the plate spring
132
,
134
being a simple, linear characteristic spring, and therefore it is possible to reduce the production cost for the key switch
120
without deteriorating the operational feeling thereof.
Moreover, in the key switch
120
, two plate springs
132
,
134
cooperate to bear the pushing-down force applied to the key top
62
, so that the stress applied to each plate spring
132
,
134
can be attenuated. Accordingly, it is possible to prevent the plate springs
132
,
134
from being damaged, and to ease the design of the plate springs
132
,
134
.
Furthermore, if a keyboard is structured by incorporating therein a plurality of key switches
120
, it is possible to hold the key top
62
of each key switch
120
in the initial projecting position for a key-entry operation through the first and second link members
66
,
68
when the keyboard is to be used, by shifting the plate spring
134
together with the movable base element
124
to the rear limit of movement, and also to automatically displace the key top
62
of each key switch
120
into the retracted position making the key-entry operation impossible when the keyboard is not to be used, by shifting the plate spring
134
together with the movable base element
124
to the front limit of movement.
When the key top
62
is in the retracted position, only the link members
66
,
68
and the compression coil spring are accommodated inside the key top
62
, so that the dimension of the key top
62
can be decreased particularly in the height direction, in comparison with the conventional key switch using the dome-shaped elastic actuating member. Consequently, according to the key switch
120
, it is possible to significantly reduce the entire height or thickness of the keyboard and can improve the portability thereof.
In the above fourth embodiment, the plate spring
132
may be formed integrally with the fixed base element
122
, both made from the same resinous material or the same metal. Alternatively, the metal plate spring
132
may be integrally joined to the resinous fixed base element
122
through an insert molding process. Also, the plate spring
134
may be formed integrally with the movable base element
124
by stamping and bending a sheet metal material. The other elastic members having liner characteristics, such as a compression coil spring, an extension coil spring, etc., may be used instead of the plate springs
132
,
134
.
Further, in the above embodiment, two plate springs
132
,
134
are arranged, one for each, between the fixed base element
122
and the respective loading portions or bars
76
of the first and second link members
66
,
68
, but instead, the elastic member having liner characteristics, such as a plate spring, may be disposed only between the fixed base element
122
and either one of the bars
76
of the first and second link members
66
,
68
. For example, if only the plate spring
132
is used, an upright wall for supporting the bar
76
of the first link member
66
may be formed integrally with the movable base element
124
, instead of the plate spring
134
. Moreover, contrary to the above embodiment, the rear plate spring
132
may be joined to the movable base element
124
and the front plate spring
134
may be joined to the fixed base element
122
.
Fifth Embodiment
FIG. 14
shows a key switch
140
according to a fifth embodiment of the present invention, which has a structure wherein a key top can be displaced to a retracted position when, e.g., a keyboard incorporating therein a plurality of key switches is not to be used.
The key switch
140
includes a key top
62
with an operation surface
62
a
adapted to be keyed by an operator's finger, a fixed base element
142
shaped as a generally rectangular frame lacking a front part thereof and arranged beneath the key top
62
, a pair of link members
66
,
68
for supporting the key top
62
above a major surface
142
a
of the base element
142
and directing or guiding the key top
62
in a vertical or going up and down direction, a movable base element
144
shaped as a rectangular frame and arranged under the fixed base element
142
, a membrane sheet
22
provided with a membrane switch
20
and disposed under the movable base element
144
, and a support plate
42
for stationary supporting the membrane sheet
22
. The key top
62
, the pair of link members
66
,
68
, the membrane switch
20
, the membrane sheet
22
and the support plate
42
have the same structures as those in the modification of the second embodiment shown in
FIG. 8
, in which plate springs
88
are respectively joined to the link members
66
,
68
, and thus the detailed description thereof is not repeated.
The fixed base element
142
is a frame-like member having a generally rectangular profile, a front part of which is cut-out or removed, and includes a generally rectangular center opening
146
covered with the key top
62
. The fixed base element
142
is provided, along opposed inner edges
142
b
thereof defining the center opening
146
, with two pairs of slide supports
148
, one pair being spaced from the other in a longitudinal or forward/backward direction, and two slide supports
148
in each pair being spaced from each other.
Each of the slide supports
148
disposed adjacent to the front end of the fixed base element
142
includes an L-shaped wall part projecting from the major surface
142
a
and the inner edge
142
b
of the fixed base element
142
, and a bearing slot
148
a
extending generally parallel to the major surface
142
a
is formed inside the wall part. These front bearing slots
148
a
open to a front side, away from the rear slide supports
148
, and to a bottom side of the fixed base element
142
. Each of the slide supports
148
disposed adjacent to the rear end of the fixed base element
142
also includes an L-shaped wall part projecting from the major surface
142
a
and the inner edge
142
b
of the fixed base element
142
, and a bearing slot
148
a
extending generally parallel to the major surface
142
a
is formed inside the wall part. These rear bearing slots
148
a
open to a rear side, away from the front slide supports
148
, and to a bottom side of the fixed base element
142
.
Two slide supports
148
of each pair are positioned on the opposed inner edges
142
b
of the fixed base element
142
in such a manner that the bearing slots
148
a
of respective slide supports
148
are aligned with and face each other. Also, the slide supports
148
in a corresponding location between two pairs are substantially aligned with each other in a longitudinal or forward/backward direction on the inner edges
142
b
of the fixed base element
142
.
The movable base element
144
is a frame-like member having a generally rectangular profile, and includes a generally rectangular center opening
150
substantially corresponding to the center opening
146
of the fixed base element
142
. The movable base element
144
cooperates with the fixed base element
142
to serve as a base of the key switch
140
. The movable base element
144
is also provided with an upright wall
152
integrally joined to an inner edge
150
a
of the movable base element
144
defining the center opening
150
. The upright wall
152
is located in the center opening
146
of the fixed base element
142
at a front side therein so as to be opposed to the rear inner edge
142
c
of the fixed base element
142
.
The movable base element
144
can be shifted together with the upright wall
152
in a forward/backward direction (shown by an arrow A) of the key switch
140
between the fixed base element
142
and the membrane sheet
22
. The plate springs
88
joined to the bars
76
of the first and second link members
66
,
68
are respectively disposed between the upright wall
152
of the movable base element
144
and the bar
76
of the first link member
66
, and between the rear inner edge
142
c
of the fixed base element
142
and the bar
76
of the second link member
68
, so as to act as compression springs.
As described above, in the fifth embodiment, the plate spring
88
disposed at the front side of the key switch
140
is abutted to the upright wall
152
which can be shifted together with the movable base element
144
in the forward/backward direction in relation to the fixed base element
142
, which is a different structure from the modification shown in FIG.
8
. Consequently, in the key switch
140
, it is possible to change the distance between front and rear wall surfaces onto which the plate springs
88
are respectively abutted, and thereby to displace the key top
62
between an initial projecting position and a retracted position during inoperating condition, as described below.
When the upright wall
152
is located together with the movable base element
144
at the rear limit of movement thereof, the plate springs
88
act in the same manner as the plate springs
86
shown in
FIG. 7
to maintain the key switch
140
in a condition for a key-entry operation. That is, when no external force is applied to the key top
62
, the plate springs
88
urge or bias the bars
76
of the first and second link members
66
,
68
toward backward and forward positions spaced from the upright wall
152
of the movable base element
144
and the inner edge
142
c
of the fixed base element
142
, respectively, and support the bars
106
in these positions, as well as, through the mutually interlocked first and second link members
66
,
68
, urging or biasing the key top
62
toward the initial position vertically upwardly away from the fixed base element
142
and supporting the key top
62
in this position.
Also, when the key top
62
is pushed down by a key-entry operation, the axles
78
of the first and second link members
66
,
68
slidingly move frontward and rearward along the bearing slots
148
a
of the front and rear slide supports
148
of the fixed base element
142
, respectively, and, simultaneously, the bars
76
shift toward the upright wall
152
of the movable base element
144
and the inner edge
142
c
of the fixed base element
142
. During this operation, the plate springs
88
are deformed while exerting biasing or elastic restoring force to the respective bars
76
(i.e., loading portions) of the first and second link members
66
,
68
in a direction substantially orthogonal to the pushing-down direction of the key top
62
.
When the pushing-down force to the key top
62
is released, the plate springs
88
elastically restore to return the key top
62
to the initial position through the first and second link members
66
,
68
. In this respect, each of the plate springs
88
is a linear characteristics spring of a simple structure, and thus exerts the biasing force, assuming a linear relationship with the shifting amount or displacement of the bar
76
, onto each of the bars
76
of the first and second link members
66
,
68
. Preferably, the plate springs
88
have shapes and characteristics, both identical to each other.
According to the key switch
140
, it is possible to establish a key-entry operating properties with non-linear characteristics, similar to that established by a dome-shaped elastic actuating member in the conventional key switch, by using two plate springs
88
with linear characteristics. This is caused by the unique arrangements of these plate springs
88
which apply the biasing force to the first and second link members
66
,
68
in a direction substantially orthogonal to the pushing-down direction of the key top
62
. The operational principle of the key switch
140
is substantially the same as that described concerning the first embodiment, and thus is not repeated.
Then, the upright wall
152
is shifted frontward, by an actuating mechanism (not shown), together with the movable base element
144
to be located at the front limit of movement thereof. When the upright wall
152
, which serves to support the plate spring
88
joined to the first link member
66
, is shifted frontward, the first and second link members
66
,
68
are automatically folded-up due to their weight and of key top
62
. As a result, the key top
62
is displaced to the retracted position lower than the initial position. In the retracted position, both the plate springs
88
are kept free of any substantial elastic deformation.
The height of the key top
62
at the retracted position depends on the location of the front limit of movement of the upright wall
152
on the movable base element
144
. The front limit of movement of the upright wall
152
may be determined by adding a base part having a front inner edge
142
c
onto the front side of the fixed base element
142
. Further, it is desired that, when the key top
62
is in the retracted position, the compression coil spring, provided on the inner surface
62
b
of the key top
62
as a membrane switch actuating member, is positioned so as not yet to push the membrane sheet
22
.
As described above, in the key switch
140
, a dome-shaped elastic actuating member in the conventional key switch is omitted, and instead, two plate springs
88
, which are not placed between the key top
62
and the membrane sheet
22
in the height direction of the key switch
140
, are used as key top biasing means, so that it is made possible to significantly reduce the entire height of the key switch
140
upon both the inoperated and operated conditions thereof. Further, each plate spring
88
can establish the key-entry operating properties with non-linear characteristics, similar to that established by the conventional dome-shaped elastic actuating member, due to the arrangement of the plate spring
88
, despite that the plate spring
88
is a simple, linear characteristic spring, and therefore it is possible to reduce the production cost for the key switch
140
without deteriorating the operational feeling thereof.
Moreover, in the key switch
140
, two plate springs
88
cooperate to bear the pushing-down force applied to the key top
62
, so that the stress applied to each plate spring
88
can be attenuated. Accordingly, it is possible to prevent the plate springs
88
from being damaged, and to ease the design of the plate springs
88
.
Furthermore, if a keyboard is structured by incorporating therein a plurality of key switches
140
, it is possible to hold the key top
62
of each key switch
140
in the initial projecting position for a key-entry operation through the first and second link members
66
,
68
when the keyboard is to be used, by shifting the upright wall
152
together with the movable base element
144
to the rear limit of movement, and also to automatically displace the key top
62
of each key switch
140
into the retracted position making the key-entry operation impossible when the keyboard is not to be used, by shifting the upright wall
152
together with the movable base element
144
to the front limit of movement.
When the key top
62
is in the retracted position, only the pair of link members
66
,
68
and the compression coil spring are accommodated inside the key top
62
, so that the dimension of the key top
62
can be decreased particularly in the height direction, in comparison with the conventional key switch using the dome-shaped elastic actuating member. Consequently, according to the key switch
140
, it is possible to significantly reduce the entire height or thickness of the keyboard and to improve the portability thereof.
Keyboard
FIG. 15
shows a keyboard
160
, according to one embodiment of the present invention, which incorporates therein a plurality of key switches
140
. The keyboard
160
is provided, in a predetermined array, with numbers of key switches
140
including the key tops
62
of various dimensions.
The fixed base elements
142
of the key switches
140
are integrally connected with one another, so as to constitute a common large fixed base element
142
′ which extends over the generally entire area of the keyboard
160
and serves as an upper cover part of a housing of the keyboard
160
. In the same manner, the movable base elements
144
, the membrane sheets
22
and the support plates
42
of the key switches
140
are integrally connected respectively with one another, so as to constitute respective common large members
144
′,
22
′,
42
′ extending over the generally entire area of the keyboard
160
. The center openings
146
of the fixed base elements
142
, the center openings
150
and the upright walls
152
of the movable base elements
144
, and the membrane switches
20
are arranged at locations corresponding to the respective key switches
140
.
The common large movable base element
144
′ is provided in the rear end region of the upper surface thereof with two protrusions
162
spaced from each other. Also, the common large fixed base element
142
′ is provided in the rear end region thereof with two apertures
164
corresponding to the protrusions
162
. Each protrusion
162
is inserted into each aperture
164
in such a manner as to be capable of shifting only in a forward/backward direction as shown by an arrow A. When the protrusions
162
are shifted in the apertures
164
in the forward/backward direction, the common large movable base element
144
′ is shifted together with all of the upright walls
152
in the forward/backward direction. Consequently, in all the key switches
140
, the key tops
62
are displaced between the initial projecting positions for a key-entry operation and the retracted positions making the key-entry operation impossible, as former described.
The protrusions
162
of the common large movable base element
144
′ may be manually operated by an operator. Alternatively, if the keyboard
160
is incorporated in a portable electronic equipment including a foldable display unit, such as a notebook size personal computer, it is possible to design an automatic operation of the protrusions
162
, which is interlocked with the open/close motion of the display unit above the keyboard
160
. In this arrangement, a known transmission system can be used which transfers the rotation of a shaft caused due to the open/close motion of the display unit into forward/backward movement or linear motion of the common large movable base element
144
′.
Modification
In the above fourth and fifth embodiments shown in
FIGS. 13 and 14
, one of the plate springs (i.e., the plate spring
134
) for urging and supporting the key top
62
and the link members
66
,
68
, or one of the wall surfaces (i.e., the upright wall
152
) onto which the one plate spring is abutted, is shifted in the forward/backward direction of the key switch
120
,
140
, that is, in a direction for changing a distance between the pair of plate springs or the pair of wall surfaces, and thereby the key top
62
is displaced between the initial projecting position and the retracted position.
In this arrangement, it is required to operate the movable base element
124
,
144
in such a manner that the plate spring
134
or the upright wall
152
is correctly and repeatably returned to a predetermined operable position in the rear limit of movement, when the key switch is to be used and the key top
62
is to be held in the initial projecting position. This is because, if the plate spring
134
or the upright wall
152
is incorrectly returned to and thus more or less deviated from the predetermined operable position every time the key top
62
is displaced between the initial projecting position and the retracted position, the key-entry operation properties subtlety varies every time, and thus the operator senses incongruity.
This problem is solved by an alternative arrangement where the plate spring
134
or the upright wall
152
is shifted in a lateral direction of the key switch
120
,
140
, that is, in a direction wherein the plate springs or the wall surfaces are relatively deviated from a face-to-face aligned state while being kept in parallel to each other, so as to displace the key top
62
between the initial projecting position and the retracted position. According to this alternative arrangement, the plate spring
134
or the upright wall
152
is permitted to be correctly and repeatably returned to the predetermined operable position, by a relatively easy operation.
FIG. 16
shows a modification of the key switch
140
shown in
FIG. 14
, which is provided with this alternative arrangement.
In this modification, the fixed base element
142
is a frame-like member having a generally rectangular profile, and includes a pair of cutouts
154
formed as extensions of the generally rectangular center opening
146
and located adjacent respectively to the bearing slots
148
a
of the slide supports
148
on one inner edge
142
b
. On the other hand, the movable base element
144
is provided with a pair of upright walls
156
integrally joined to the inner edge
150
a
defining the center opening
150
, so as to be located close to the front and rear inner edges
142
c
of the fixed base element
142
in the center opening
146
. The movable base element
144
can be shifted together with the upright walls
156
in a lateral direction (shown by an arrow B) of the key switch
140
between the fixed base element
142
and the membrane sheet
22
(FIG.
14
).
The upright walls
156
include main portions extending parallel to each other, and extensions
156
a
extending obliquely from the ends of the main portions to gradually expand the distance between the extensions
156
a
. Each cutout
154
formed on one inner edge
142
b
of the fixed base element
142
has a dimension and shape for receiving each extension
156
a.
In the above structure, when the upright walls
156
are located together with the movable base element
144
at one limit of lateral movement thereof, the plate springs
88
joined to the first and second link members
66
,
68
are respectively abutted and supported on the main portions of the upright walls
156
. In this location, the extensions
156
a
of the upright walls
156
are received respectively in the cutouts
154
of the fixed base element
142
. In this state, the plate springs
88
act in the same manner as the plate springs
86
shown in
FIG. 7
to maintain the key switch
140
in a condition for a key-entry operation.
That is, when no external force is applied to the key top
62
, the plate springs
88
urge or bias the key top
62
toward the initial position vertically upwardly away from the fixed base element
142
and support the key top
62
in this position, through the mutually interlocked first and second link members
66
,
68
. Also, when the key top
62
is pushed down by a key-entry operation, the bars
76
of the first and second link members
66
,
68
shift toward the main portions of the upright walls
156
of the movable base element
144
. During this operation, the plate springs
88
are deformed while exerting biasing or elastic restoring force to the respective bars
76
(i.e., loading portions) of the first and second link members
66
,
68
in a direction substantially orthogonal to the pushing-down direction of the key top
62
. When the pushing-down force to the key top
62
is released, the plate springs
88
elastically restore to return the key top
62
to the initial position through the first and second link members
66
,
68
.
Then, the upright walls
156
are shifted, by an actuating mechanism (not shown), together with the movable base element
144
to be located at the other limit of lateral movement thereof. Thereby, the plate springs
88
leave the main portions of the upright walls
156
and come into contact with the extensions
156
a
to be supported thereon. Finally, the plate springs
88
come to be out of supports of the upright walls
156
. As a result, the first and second link members
66
,
68
are automatically folded-up due to their weight and of the key top
62
, so that the key top
62
is displaced to the retracted position lower than the initial position.
From this location, the upright walls
156
are shifted in a reverse direction together with the movable base element
144
so as to be relocated at one limit of lateral movement thereof. Thereby, the key top
62
is returned to the initial position through the plate springs
88
and the first and second link members
66
,
68
, and the key switch
140
recovers a condition for a key-entry operation. During this operation, the distance between the main portions of the upright walls
156
are kept in uniform, which enables the upright walls
156
to be correctly and repeatably positioned to the predetermined operable position in a relatively easy operation. Consequently, it is possible to effectively prevent the fluctuation of the key-entry operation properties of the key switch
140
.
Sixth Embodiment
In the key switch
10
,
60
,
90
,
120
,
140
of any of the above embodiments, the plate spring
48
,
50
,
86
,
88
,
116
,
118
,
132
,
134
, as an elastic member for urging upward the key top
12
,
62
,
92
away from the base
14
,
64
,
94
,
122
,
142
, exerts biasing force in a generally horizontal direction to the loading portion (the bar
34
,
76
,
106
) which assumes a movement substantially identical to the movement of the sliding portion (the axle
36
,
78
,
108
) of the link member
16
,
66
,
68
,
96
,
98
when the key top
12
,
62
,
92
goes up and down. The present invention is not limited to this construction, but can also provide an alternative construction, as described below, in which a plate spring, as an elastic member for urging upward a key top away from a base, exerts biasing force in a generally horizontal direction to a loading portion of a link member, which assumes a movement different from a movement of a sliding portion of the link member, when the key top goes up and down.
FIGS. 17 and 18
show a key switch
170
according to a sixth embodiment of the present invention. The key switch
170
is one which includes the above-described alternative construction concerning the loading portion of a link member, and the remaining structure of the key switch
170
is substantially the same as that of the key switch
10
of the first embodiment. Therefore, the same or similar components are denoted by the common reference numerals, and a detailed description thereof is not repeated.
The key switch
170
includes a key top
12
, a base
14
shaped as a rectangular frame and arranged beneath the key top
12
, a pair of link members
172
,
174
for supporting the key top
12
above a major surface
14
a
of the base
14
and directing or guiding the key top
12
in a vertical or up and down direction, a membrane sheet
22
provided with a membrane switch
20
and disposed under the base
14
, and a support plate
42
for stationary supporting the membrane sheet
22
.
The pair of link members
172
,
174
are structured as a first link member
172
and a second link member
174
, which have a mutually substantially identical shape, and which are assembled together so as to be provided with a generally X-shape in a side view. Each of the link members
172
,
174
includes two arms
176
extending parallel to each other, and a bar
178
mutually connecting the arms
176
near one ends of the arms
176
. Axles
180
are provided on one ends of the arms
176
to mutually coaxially project on the opposite sides to the bar
178
. Axles
182
are provided on the other ends of the arms
176
to mutually coaxially project on the same sides as the axles
180
.
The first and second link members
172
,
174
are arranged to mutually intersect, and are pivotably connected relative to each other at an intersection thereof. More particularly, the first and second link members
172
,
174
are pivotably connected with each other by pivots
184
provided at generally longitudinal centers of the respective pair of arms
176
.
The axles
180
formed on one ends of the arms
176
of the first link member
172
are slidably fitted or received in the respective bearing slots
30
a
of the slide supports
30
on the base
14
, and the axles
182
formed on the other ends of the arms
176
of the first link member
172
are pivotably fitted or received in the respective bearing holes
24
a
of the pivot supports
70
on the key top
12
, whereby the first link member
172
is arranged between the key top
12
and the base
14
in such a manner as to be pivotable about the axles
182
on the key top
12
.
The axles
180
formed on one ends of the arms
176
of the second link member
174
are pivotably fitted or received in the respective bearing holes
28
a
of the pivot supports
28
on the base
14
, and the axles
182
formed on the other ends of the arms
176
of the second link member
174
are slidably fitted or received in the respective bearing slots
26
a
of the slide supports
26
on the key top
12
, whereby the second link member
174
is arranged between the key top
12
and the base
14
in such a manner as to be pivotable about the axles
180
on the base
14
.
The structure of the first and second link members
172
,
174
described above substantially corresponds to the structure of the first and second link members
16
,
18
of the key switch
10
of the first embodiment, except that, in each link member
172
,
174
, the bar
178
is formed at a position angularly displaced in certain angle relative to the axles
180
about the pivot
184
. Therefore, in this embodiment, the axles
180
of the first link member
172
and the axles
182
of the second link member
174
constitute sliding portions of the respective link members
172
,
174
. The first and second link members
172
,
174
are interlocked to each other through the pivots
184
so as to be synchronously pivotable, so that the key top
12
is permitted to be subjected to a parallel displacement in a substantially vertical direction in relation to the major surface
14
a
of the base
14
, while keeping a predetermined posture of the key top
12
wherein the operation surface
12
a
thereof is generally parallel to the major surface
14
a.
The key switch
170
further includes a plate spring
186
or an elastic member, disposed between the base
14
and the first link member
172
, which acts as biasing means for elastically urging upward the key top
12
away from the base
14
. As diagrammatically shown in
FIG. 18
, a plate spring
186
is integrally joined at one end thereof to a front inner edge
14
c
of the base
14
opposite to the bearing slots
30
a
of the slide supports
30
, so as to extend above the major surface
14
a
of the base
14
, and is abutted at the other free end thereof to the bar
178
of the first link member
172
. The plate spring
186
acts as a compression spring between the base
14
and the bar
178
of the first link member
172
.
When no external force is applied to the key top
12
, the plate spring
186
urges or biases the bar
178
of the first link member
172
toward a backward position spaced from the front inner edge
14
c
of the base
14
and supports the bar
178
in this position, as well as, through the mutually interlocked first and second link members
172
,
174
, urges or biases the key top
12
toward the initial position vertically upwardly away from the base
14
and support the key top
12
in this position (see FIG.
18
).
When the key top
12
is pushed down by a key-entry operation, the axles
180
of the first link member
172
slidingly move frontward along the bearing slots
30
a
of the slide supports
30
of the base
14
and, simultaneously, the bar
178
shifts toward the front inner edge
14
c
of the base
14
. During this operation, the bar
178
assumes a movement different from a movement of the axles
180
, because the bar
178
is formed at a position angularly displaced in certain angle relative to the axles
180
about the pivot
184
. Then, the plate spring
186
is deformed while exerting biasing or elastic restoring force to the bar
178
(i.e., a loading portion) of the first link member
172
in a direction substantially orthogonal to the pushing-down direction of the key top
12
.
When the pushing-down force to the key top
12
is released, the plate spring
186
elastically restores to return the key top
12
to the initial position through the first and second link members
172
,
174
. In this respect, the plate spring
186
is a linear characteristics spring of a simple structure, and thus exerts the biasing force, assuming a linear relationship with the shifting amount or displacement of the bar
178
, onto the bar
178
of the first link member
172
.
According to the key switch
170
, it is possible to establish key-entry operating properties with non-linear characteristics, similar to that established by a dome-shaped elastic actuating member in the conventional key switch, by using the plate spring
186
with linear characteristics. This is caused by the unique arrangement of the plate spring
186
which applies the biasing force to the first link member
172
in a direction substantially orthogonal to the pushing-down direction of the key top
12
. The operational principle of the key switch
170
is substantially the same as that described concerning the first to fifth embodiments with reference to
FIGS. 4A
to
4
C.
Further, it should be noted that the key switch
170
can also provide advantageous effects as described later, because of the angularly displaced arrangement of the bar
178
(the loading portion) of the first link member
172
relative to the axles
180
(the sliding portion) thereof. The operational principle of the first link member
172
and the plate spring
186
is described below with reference to
FIGS. 19A
to
19
C.
FIG. 19A
diagrammatically shows a constitution in which a link having a length “L” (the first link member
172
) is obliquely arranged and a compression spring (the plate spring
186
) is joined to a loading portion (the bar
178
) near the bottom end of the link, and in which the top end (the axles
182
) of the link is pushed down in a vertical downward direction. In this constitution, the reaction force “f” of the compression spring is applied to the loading portion of the link in a horizontal direction, in connection with the pushing-down force “F” applied to the top end of the link in the vertical downward direction. Please note here that:
F=f·tan θ (θ is a link angle);
f=k·x (k is a spring constant, x is a horizontal displacement of link loading portion);
X=L (sin θ
0
−sin θ) (X is a vertical displacement of link top end, θ
0
is a link angle at f=0); and
x=−L·(cos θ
0
−cos θ).
In such a constitution of the key switch
170
, it is possible to push down the axles
182
of top of the first link member
172
to a position lower than the bar
178
as the loading portion of the first link member
172
. Then, the inventors of the present application numerically analyzed the parameter −50≦θ≦40° in accordance with the above principles, supposing that θ
0
−400, L=5 mm, k=120 gf/mm, so as to substantially equalize the downward stroke of the key top
12
or the axles
182
of top of the first link member
172
in the key switch
170
with the downward stroke of the key top
12
in the key switch
10
shown in
FIG. 1
, and compared the results thereof to the results of the analysis in relation to
FIGS. 4A
to
4
C. The relationship, thus determined, between the vertical displacement “X” of the link top end and the pushing-down force “F” is shown by a solid line in
FIG. 19B
in which the curve shown in
FIG. 4B
is complementarily illustrated by a double dot chain line.
As illustrated, the similar characteristic curve was obtained, wherein, at the instant when the vertical displacement “X” of the link top end exceeds a predetermined value, the pushing-down force “F”, which has been gradually increased until that time, is reduced to the contrary. In particular, as shown in
FIG. 19B
, the pushing-down force “F” applied to the link top end in the key switch
170
reaches a maximum value at the shorter vertical displacement “X” of the link top end than that in the first to fifth embodiments. Also, in an actual operation, the synthetic characteristic curve is obtained, as shown by a solid line in
FIG. 19C
in the same way as
FIG. 4C
, since the reaction force “R” due to the compression coil spring
46
acting as the actuating member for the membrane switch
20
is additionally exerted, after the key top
12
passes the predetermined pushed-down position.
In manufacturing the key switch according to the present invention, it is important, for stably and properly actuating the membrane switch, that the pushed-down position of the key top when the actuating member comes into contact with the membrane switch (i.e., upon starting to actuate the latter) is set at a location as high above the physical lowest position of the key top in the vertical stroke thereof (i.e., a location wherein the vertical displacement of the link top end is as short as possible). If, in the characteristic curve of
FIG. 4C
, the actuation starting position of the key top is set at a location “P” higher than a location shown in
FIG. 4C
, the variation of the resulted pushing-down force “F” to the link top end, between a first position of the key top wherein the pushing-down force “F” is maximum and the actuation starting position, is decreased (see FIG.
19
C). As a result, it may become difficult to establish a key-entry operating properties similar to that established in the conventional key switch using a dome-shaped elastic actuating member.
Contrary to this, in the characteristic curve (a solid line) of
FIG. 19C
, even if the actuation starting position of the key top is set at the above-mentioned location “P”, it is possible to obtain the sufficient variation of the resulted pushing-down force “F” between the position wherein the pushing-down force “F” is maximum and the actuation starting position. Consequently, it is possible, in the key switch
170
, to establish a key-entry operating properties with non-linear characteristics, similar to that established in the conventional key switch using a dome-shaped elastic actuating member.
As will be appreciated, the key switch
170
can provide various effects essentially equivalent to those of the key switch
10
of the first embodiment. Also, in this embodiment, the plate spring
186
is integrally joined to the inner edge
14
c
of the base
14
defining the center opening
15
, but a plate spring
188
may be used as a modification, which is integrally joined to the first link member
172
, as shown in FIG.
20
. In this modification, which corresponds to the modification shown in
FIG. 5
, the plate spring
188
is integrally joined at one end thereof to the neighbourhood of the bar
178
of the first link member
172
, and is abutted at the other free end thereof to a wall
190
extending upward from the inner edge
14
c
of the base
14
. The material, the manufacturing process, the arrangement, etc. of the plate spring
186
,
188
may be variously selected, in the same way as the plate spring
48
,
50
of the key switch
10
.
Seventh Embodiment
FIG. 21
shows a key switch
200
according to a seventh embodiment of the present invention, which corresponds to the key switch
60
of the second embodiment shown in FIG.
6
. The key switch
200
is one which includes the alternative construction concerning the loading portion of a link member, and the remaining structure of the key switch
200
is substantially the same as that of the key switch
60
of the second embodiment. Therefore, the same or similar components are denoted by the common reference numerals, and the detailed description thereof is not repeated.
The key switch
200
includes a key top
62
, a base
64
shaped as a rectangular frame and arranged beneath the key top
62
, a pair of link members
202
,
204
for supporting the key top
62
above a major surface
64
a
of the base
64
and directing or guiding the key top
62
in a vertical or going up and down direction, a membrane sheet
22
provided with a membrane switch
20
and disposed under the base
64
, and a support plate
42
for stationarily supporting the membrane sheet
22
.
The pair of link members
202
,
204
are structured as a first link member
202
and a second link member
204
, which have a mutually substantially identical shape, and are assembled together so as to be provided with a generally X-shape in a side view. Each of the link members
202
,
204
includes two arms
206
extending parallel to each other, and a bar
208
mutually connecting the arms
206
near one ends of the arms
206
. Axles
210
are provided on one ends of the arms
206
to mutually coaxially project on the opposite sides to the bar
208
. Axles
212
are provided on the other ends of the arms
206
to mutually coaxially project on the same sides as the axles
210
.
The first and second link members
202
,
204
are arranged to mutually intersect, and are pivotably and slidably connected relative to each other at an intersection thereof. More particularly, the first and second link members
202
,
204
are pivotably and slidably connected with each other by respective interengagements between pivots
214
provided at generally longitudinal centers of one arms
206
of respective link members and elliptic holes
216
provided at generally longitudinal centers of the other arms
206
of respective link members.
The axles
210
formed on the ends of the arms
206
of the first link member
202
are slidably fitted or received in the respective bearing slots
72
a
of the front slide supports
72
on the base
64
, and the axles
212
formed on the other ends of the arms
206
of the first link member
202
are pivotably fitted or received in the respective bearing holes
70
a
of the rear pivot supports
70
on the key top
62
, whereby the first link member
202
is arranged between the key top
62
and the base
64
in such a manner as to be pivotable about the axles
212
on the key top
62
.
The axles
210
formed on the ends of the arms
206
of the second link member
204
are slidably fitted or received in the respective bearing slots
72
a
of the rear slide supports
72
on the base
64
, and the axles
212
formed on the other ends of the arms
206
of the second link member
204
are pivotably fitted or received in the respective bearing holes
70
a
of the front pivot supports
70
on the key top
62
, whereby the second link member
204
is arranged between the key top
62
and the base
64
in such a manner as to be pivotable about the axles
212
on the key top
62
.
The structure of the first and second link members
202
,
204
described above substantially corresponds to the structure of the first and second link members
66
,
68
of the key switch
60
of the second embodiment, except that, in each link member
202
,
204
, the bar
208
is formed at a position angularly displaced in certain angle relative to the axles
210
about the pivot
214
. Therefore, in this embodiment, the axles
210
of the first link member
202
and the axles
210
of the second link member
204
constitute sliding portions of the respective link members
202
,
204
. The first and second link members
202
,
204
are interlocked to each other through the slidable interengagements between the pivots
214
and the elliptic holes
216
so as to be synchronously pivotable, so that the key top
62
is permitted to be subjected to a parallel displacement in a substantially vertical direction in relation to the major surface
64
a
of the base
64
, while keeping a predetermined posture of the key top
62
wherein the operation surface
62
a
thereof is generally parallel to the major surface
64
a.
The key switch
200
further includes a pair of plate springs
218
or elastic members, disposed between the base
64
and the first and second link members
202
,
204
, which act as biasing means for elastically urging upward the key top
62
away from the base
64
. One plate spring
218
is integrally joined at one end thereof to a front inner edge
64
c
of the base
64
opposite to the bearing slots
72
a
of the front slide supports
72
, so as to extend above the major surface
64
a
of the base
64
, and is abutted at the other free end thereof to the bar
208
of the first link member
202
. The other plate spring
218
is integrally joined at one end thereof to a rear inner edge
64
c
of the base
64
opposite to the bearing slots
72
a
of the rear slide supports
72
, so as to extend above the major surface
64
a
of the base
64
, and is abutted at the other free end thereof to the bar
208
of the second link member
204
. The plate springs
218
act as compression springs between the inner edges
64
c
of the base
64
and the bars
208
of the first and second link members
202
,
204
, respectively.
When no external force is applied to the key top
62
, the plate springs
218
urge or bias the bars
208
of the first and second link members
202
,
204
toward backward and forward positions spaced from the front and rear inner edges
64
c
of the base
64
, respectively, and support the bars
208
in these positions, as well as, through the mutually interlocked first and second link members
202
,
204
, urging or biasing the key top
62
toward the initial position vertically upwardly away from the base
64
and supporting the key top
62
in this position.
When the key top
62
is pushed down by a key-entry operation, the axles
210
of the first and second link members
202
,
204
slidingly move frontward and rearward along the bearing slots
72
a
of the front and rear slide supports
72
of the base
64
, respectively, and, simultaneously, the bars
208
shift toward the front and rear inner edges
64
c
of the base
64
. During this operation, the bars
208
assume a movement different from a movement of the axles
210
, because the bars
208
are formed at positions angularly displaced at a certain angle relative to the axles
210
about the pivots
214
. Then, the plate springs
218
are deformed while exerting biasing or elastic restoring force to the respective bars
208
(i.e., loading portions) of the first and second link members
202
,
204
in a direction substantially orthogonal to the pushing-down direction of the key top
62
.
When the pushing-down force to the key top
62
is released, the plate springs
218
elastically restore to return the key top
62
to the initial position through the first and second link members
202
,
204
. In this respect, each of the plate springs
218
is a linear characteristics spring of a simple structure, and thus exerts the biasing force, assuming a linear relationship with the shifting amount or displacement of the bar
208
, onto each of the bars
208
of the first and second link members
202
,
204
. Preferably, the plate springs
218
have shapes and characteristics, both identical to each other.
According to the key switch
200
, it is possible to establish key-entry operating properties with non-linear characteristics, similar to that established by a dome-shaped elastic actuating member in the conventional key switch, by using two plate springs
218
with linear characteristics. This is caused by the unique arrangements of these plate springs
218
which apply the biasing force to the first and second link members
202
,
204
in a direction substantially orthogonal to the pushing-down direction of the key top
62
. The operational principle of the key switch
200
is substantially the same as that described concerning the sixth embodiment.
Particularly, in the key switch
200
, because of the angularly displaced arrangement of the bars
208
(the loading portions) of the first and second link members
202
,
204
relative to the axles
210
(the sliding portions) thereof, it is possible to set the pushed-down position of the key top
62
upon starting to actuate the membrane switch
20
at a location as high as possible above the physical lowest position of the key top
62
in the vertical stroke thereof, while ensuring a key-entry operating properties with non-linear characteristics, similar to that established in the conventional key switch using a dome-shaped elastic actuating member.
As will be appreciated, the key switch
200
can provide various effects essentially equivalent to those of the key switch
60
of the second embodiment. Also, in this embodiment, the plate springs
218
are integrally joined to the inner edges
64
c
of the base
64
defining the center opening
65
, but plate springs
220
may be used as a modification, which are integrally joined to the first and second link members
202
,
204
, respectively, as shown in FIG.
22
. In this modification, which corresponds to the modification shown in
FIG. 8
, the plate springs
220
are integrally joined at the ends thereof to the neighbourhood of the bars
208
of the first and second link members
202
,
204
, and are abutted at the other free ends thereof to walls
222
extending upward from the front and rear inner edges
64
c
of the base
64
, respectively. The material, the manufacturing process, the arrangement, etc. of each plate spring
218
,
220
may be variously selected, in the same way as each plate spring
86
,
88
of the key switch
60
.
Eighth Embodiment
FIG. 23
shows a key switch
230
according to an eighth embodiment of the present invention, which corresponds to the key switch
90
of the third embodiment shown in FIG.
10
. The key switch
230
is one which includes the alternative construction concerning the loading portion of a link member, and the remaining structure of the key switch
230
is substantially the same as that of the key switch
90
of the third embodiment. Therefore, the same or similar components are denoted by the common reference numerals, and the detailed description thereof is not repeated.
The key switch
230
includes a key top
92
, a base
94
shaped as a rectangular frame and arranged beneath the key top
92
, a pair of link members
232
,
234
for supporting the key top
92
above a major surface
94
a
of the base
94
and directing or guiding the key top
92
in a vertical or going up and down direction, a membrane sheet
22
provided with a membrane switch
20
and disposed under the base
94
, and a support plate
42
for stationary supporting the membrane sheet
22
.
The pair of link members
232
,
234
are structured as a first link member
232
and a second link member
234
, which have a mutually substantially identical shape, and which are assembled together so as to be provided with a generally reverse V-shape in a side view. Each of the link members
232
,
234
includes two arms
236
extending parallel to each other, and a bar
238
mutually connecting the arms
236
near one ends of the arms
236
. Axles
240
are provided on the ends of the arms
236
to mutually coaxially project on the opposite sides to the bar
238
. Axles
242
are provided on the other ends of the arms
236
to mutually coaxially project on the same sides as the axles
240
.
The first and second link members
232
,
234
are meshed with each other at a toothed end of each link member
232
,
234
. More particularly, the first and second link members
232
,
234
are pivotably connected with each other by intermeshings between respective one tooth
244
projecting from the distal ends, near the axles
242
, of one arms
236
of respective link members and respective two teeth
246
projecting from the distal ends, near the axles
242
, of the other arms
236
of respective link members.
The axles
240
formed on one ends of the arms
236
of the first link member
232
are slidably fitted or received in the respective bearing slots
102
a
of the front slide supports
102
on the base
94
, and the axles
242
formed on the other ends of the arms
236
of the first link member
232
are pivotably fitted or received in the respective bearing holes
100
a
of the front pivot supports
100
on the key top
92
, whereby the first link member
232
is arranged between the key top
92
and the base
94
in such a manner as to be pivotable about the axles
242
on the key top
92
.
The axles
240
formed on the ends of the arms
236
of the second link member
234
are slidably fitted or received in the respective bearing slots
102
a
of the rear slide supports
102
on the base
94
, and the axles
242
formed on the other ends of the arms
236
of the second link member
234
are pivotably fitted or received in the respective bearing holes
100
a
of the rear pivot supports
100
on the key top
92
, whereby the second link member
234
is arranged between the key top
92
and the base
94
in such a manner as to be pivotable about the axles
242
on the key top
92
.
The structure of the first and second link members
232
,
234
described above substantially corresponds to the structure of the first and second link members
96
,
98
of the key switch
90
of the third embodiment, except that, in each link member
232
,
234
, the bar
238
is formed at a position angularly displaced in certain angle relative to the axles
240
about the mutually intermeshed teeth
244
,
246
. Therefore, in this embodiment, the axles
240
of the first link member
232
and the axles
240
of the second link member
234
constitute sliding portions of the respective link members
232
,
234
. The first and second link members
232
,
234
are interlocked to each other through the intermeshings between the one tooth
112
and the two teeth
114
so as to be synchronously pivotable, so that the key top
92
is permitted to be subjected to a parallel displacement in a substantially vertical direction in relation to the major surface
94
a
of the base
94
, while keeping a predetermined posture of the key top
92
wherein the operation surface
92
a
thereof is generally parallel to the major surface
94
a.
The key switch
230
further includes a pair of plate springs
248
or elastic members, disposed between the base
94
and the first and second link members
232
,
234
, which act as biasing means for elastically urging upward the key top
92
away from the base
94
. One plate spring
248
is integrally joined at one end thereof to a front inner edge
94
c
of the base
94
opposite to the bearing slots
102
a
of the front slide supports
102
, so as to extend above the major surface
94
a
of the base
94
, and is abutted at the other free end thereof to the bar
238
of the first link member
232
. The other plate spring
248
is integrally joined at one end thereof to a rear inner edge
94
c
of the base
94
opposite to the bearing slots
102
a
of the rear slide supports
102
, so as to extend above the major surface
94
a
of the base
94
, and is abutted at the other free end thereof to the bar
238
of the second link member
234
. The plate springs
248
act as compression springs between the inner edges
94
c
of the base
94
and the bars
238
of the first and second link members
232
,
234
, respectively.
When no external force is applied to the key top
92
, the plate springs
248
urge or bias the bars
238
of the first and second link members
232
,
234
toward backward and forward positions spaced from the front and rear inner edges
94
c
of the base
94
, respectively, and support the bars
238
in these positions, as well as, through the mutually interlocked first and second link members
232
,
234
, urging or biasing the key top
92
toward the initial position vertically upwardly away from the base
94
and supporting the key top
92
in this position.
When the key top
92
is pushed down by a key-entry operation, the axles
240
of the first and second link members
232
,
234
slidingly move frontward and rearward along the bearing slots
102
a
of the front and rear slide supports
102
of the base
94
, respectively, and, simultaneously, the bars
238
shift toward the front and rear inner edges
94
c
of the base
94
. During this operation, the bars
238
assume a movement different from a movement of the axles
240
, because the bars
238
are formed at positions angularly displaced at a certain angle relative to the axles
240
about the mutually intermeshed teeth
244
,
246
. Then, the plate springs
248
are deformed while exerting biasing or elastic restoring force to the respective bars
238
(i.e., loading portions) of the first and second link members
232
,
234
in a direction substantially orthogonal to the pushing-down direction of the key top
92
.
When the pushing-down force to the key top
92
is released, the plate springs
248
elastically restore to return the key top
92
to the initial position through the first and second link members
232
,
234
. In this respect, each of the plate springs
248
is a linear characteristic spring of a simple structure, and thus exerts the biasing force, assuming a linear relationship with the shifting amount or displacement of the bar
238
, onto each of the bars
238
of the first and second link members
232
,
234
. Preferably, the plate springs
248
have shapes and characteristics identical to each other.
According to the key switch
230
, it is possible to establish a key-entry operating properties with non-linear characteristics, similar to that established by a dome-shaped elastic actuating member in the conventional key switch, by using two plate springs
248
with linear characteristics. This is caused by the unique arrangements of these plate springs
248
which apply the biasing force to the first and second link members
232
,
234
in a direction substantially orthogonal to the pushing-down direction of the key top
92
. The operational principle of the key switch
230
is substantially the same as that described concerning the sixth embodiment.
Particularly, in the key switch
230
, because of the angularly displaced arrangement of the bars
238
(the loading portions) of the first and second link members
232
,
234
relative to the axles
240
(the sliding portions) thereof, it is possible to set the pushed-down position of the key top
92
upon starting to actuate the membrane switch
20
at a location as high as possible above the physical lowest position of the key top
92
in the vertical stroke thereof, while ensuring a key-entry operating properties with non-linear characteristics, similar to that established in the conventional key switch using a dome-shaped elastic actuating member.
As will be appreciated, the key switch
230
can provide various effects essentially equivalent to those of the key switch
90
of the third embodiment. Also, in this embodiment, the plate springs
248
are integrally joined to the inner edges
94
c
of the base
94
defining the center opening
95
, but plate springs
250
may be used as a modification, which are integrally joined to the first and second link members
232
,
234
, respectively, as shown in FIG.
24
. In this modification, which corresponds to the modification shown in
FIG. 12
, the plate springs
250
are integrally joined at one ends thereof to the neighbourhood of the bars
238
of the first and second link members
232
,
234
, and are abutted at the other free ends thereof to walls
252
extending upward from the front and rear inner edges
94
c
of the base
94
, respectively. The material, the manufacturing process, the arrangement, etc. of each plate spring
248
,
250
may be variously selected, in the same way as each plate spring
116
,
118
of the key switch
90
.
Ninth Embodiment
The above alternative construction wherein the loading portion of the link member, onto which the biasing force of the elastic member is exerted, is formed at a position angularly displaced relative to the sliding portion of the link member, may also be applied to the key switch including a movable base element arranged under a fixed base element, as shown in
FIGS. 13
to
16
.
FIG. 25
shows a key switch
260
including such a movable base element, according to a ninth embodiment of the present invention. The key switch
260
is preferably used in a relatively thin keyboard having an improved portability, in which the key top of each key switch is held in an initial projecting position for a key-entry operation during the operating state of the keyboard, while the key top is positively displaced to a retracted position lower than the initial position during the inoperating (or carrying) state of the keyboard.
The key switch
260
includes a key top
12
with an operation surface
12
a
adapted to be keyed by an operator's finger, a fixed base element
14
(hereinafter referred to as a base
14
) shaped as a rectangular frame and arranged beneath the key top
12
, a pair of link members
172
,
174
for supporting the key top
12
above a major surface
14
a
of the base
14
and directing or guiding the key top
12
in a vertical or up-and-down direction, a movable base element
262
shaped as a rectangular frame and arranged under the base
14
, a membrane sheet
22
provided with a membrane switch
20
and disposed under the movable base element
262
, and a support plate
42
for supporting the membrane sheet
22
. The key top
12
, the base
14
, the link members
172
,
174
, the membrane switch
20
, the membrane sheet
22
and the support plate
42
have substantially the same structures as those in the key switch
170
of the sixth embodiment shown in
FIG. 17
, and thus the detailed description thereof is not repeated.
The movable base element
262
is a frame-like member having a generally rectangular profile, and includes a generally rectangular center opening
264
substantially corresponding to the center opening
15
of the base
14
. The movable base element
262
cooperates with the base
14
(i.e., the fixed base element) to serve as a base of the key switch
260
. The movable base element
262
can be shifted in a forward/backward direction (shown by an arrow A) of the key switch
260
between the base
14
and the membrane sheet
22
.
The key switch
260
further includes a plate spring
266
or an elastic member, disposed between the movable base element
262
and the first link member
172
, which acts as biasing means for elastically urging upward the key top
12
away from the base
14
. The plate spring
266
is integrally joined at one end thereof to an inner edge
264
a
defining the center opening
264
of the movable base element
262
, so as to be arranged near the front inner edge
14
c
of the base
14
opposite to the bearing slots
30
a
of the slide supports
30
, and extends at the other free end thereof through the center opening
15
of the base
14
to project above the major surface
14
a
, so as to be abutted to the bar
178
of the first link member
172
.
The plate spring
266
joined to the movable base element
262
is capable of being shifted together with the movable base element
262
in the forward/backward direction in relation to the base
14
, and, in connection with the shifted position thereof, optionally acts as a compression spring between the base (i.e., the base
14
and the movable base element
262
) and the bar
178
of the first link member
172
. Therefore, in the key switch
260
, it is possible to change the distance between the plate spring
266
and the rear inner edge
14
c
of the base
14
, and thereby to displace the key top
12
between an initial projecting position and a retracted position during inoperating condition, as described below.
When the movable base element
262
is located at the rear limit of movement thereof, the plate spring
266
acts in the same manner as the plate spring
186
shown in
FIG. 17
to maintain the key switch
260
in a condition for a key-entry operation. In this respect, the plate spring
266
is a linear characteristics spring of a simple structure, and thus exerts the biasing force, assuming a linear relationship with the shifting amount or displacement of the bar
178
, onto the bar
178
of the first link member
172
.
Then, the plate spring
266
is shifted frontward, by an actuating mechanism (not shown), together with the movable base element
262
to be located at the front limit of movement thereof. When the plate spring
266
, which serves to support the first link member
172
, is shifted frontward, the first and second link members
172
,
174
are automatically folded-up due to their weight and of key top
12
. As a result, the key top
12
is displaced to the retracted position lower than the initial position. In the retracted position, the plate spring
266
is kept free of any substantial elastic deformation.
The height of the key top
12
at the retracted position depends on the location of the front limit of movement of the plate spring
266
or the movable base element
262
. Therefore, in order to sufficiently lower the height of the key top
12
at the retracted position, it is preferred that the components of key switch
260
are dimensioned so that a sufficient gap is defined between the plate spring
266
and the front inner edge
14
c
of the base
14
when the movable base element
262
is placed at the rear limit of movement. Alternatively, the part of the base
14
including the front inner edge
14
c
may be removed or cut out, whereby the limit of movement of the movable base element
262
and thus the plate spring
266
can be enlarged frontward.
The key switch
260
further includes an actuating member
268
for actuating the membrane switch
20
, which is in the form of a second plate spring integrally provided on the first link member
172
, instead of the compression coil spring provided on the inner surface
12
b
of the key top
12
in the key switch
170
of FIG.
17
. The actuating member
268
is fixedly joined at one end thereof to the generally longitudinally center of one arm
176
of the first link member
172
, and extends at the other free end thereof to close with the bar
178
of the first link member
172
so as to form a bend with a convex surface facing downward. The actuating member
268
is provided at the free end thereof with a generally flat tongue
268
a
extending adjacent to and outwardly bent from the bend.
When the key top
12
is located at the initial highest position in the key-entry operation, the free end of the actuating member
268
is located above the center opening
15
of the base
14
. When the key top
12
is pushed down to and located at a predetermined position, the free end of the actuating member
268
enters into the center opening
15
of the base
14
, and elastically pushes the membrane switch
20
by the convex surface of the bent of the actuating member
268
.
On the other hand, the movable base element
262
is provided integrally with an generally L-shaped assist member
270
arranged along a front inner edge
264
b
of the center opening
264
adjacent to the inner edge
264
a
to which the plate spring
266
is joined, and located in front of the plate spring
266
. The assist member
270
is fixedly joined at one end thereof to the front inner edge
264
b
of the movable base element
262
, and extends through the center opening
15
of the base
14
to project above the major surface
14
a
and to orient the other end thereof toward the plate spring
266
.
The assist member
270
joined to the movable base element
262
can be shifted together with the movable base element
262
and the plate spring
266
in the forward/backward direction relative to the base
14
. Consequently, the assist member
270
can be shifted between a first position where the assist member
270
comes into engagement with the tongue
268
a
of the actuating member
268
and a second position where the assist member
270
is away from the tongue
268
a
, during the time when the key top
12
is located at the predetermined pushed-down position.
When the key switch
260
is held in the condition for the key-entry operation, i.e., when the movable base element
262
is placed at the rear limit of movement thereof, the assist member
270
is located at the above-described first position. During this condition, if no external force is applied to the key top
12
, the plate spring
266
urges or biases the key top
12
toward the initial position vertically upwardly away from the base
14
and supports the key top
12
in this position, through the mutually interlocked first and second link members
172
,
174
. In this state, the free end of the actuating member
268
is located above the center openings
15
,
264
of the base
14
and the movable base element
262
, so as not to contact with the membrane sheet
22
. Also, the membrane switch
20
is positioned beneath the free end of the assist member
270
joined to the movable base element
262
, as shown in
FIGS. 26A and 26B
.
When the key top
12
is pushed down by the key-entry operation, the plate spring
266
is deformed while exerting biasing or elastic restoring force to the bar
178
(i.e., the loading portion) of the first link member
172
in a direction substantially orthogonal to the pushing-down direction of the key top
12
. When the key top
12
reaches the predetermined pushed-down position, the free end of the actuating member
268
enters into the center openings
15
,
264
of the base
14
and the movable base element
262
, so as to be abutted at the convex surface of the bent of the actuating member
268
onto the surface of the membrane sheet
22
(see FIG.
26
A). Then, the key top
12
is further pushed down, whereby the tongue
268
a
of the actuating member
268
comes into engagement with the assist member
270
joined to the movable base element
262
(see FIG.
26
B). The key top
12
is subsequently yet further pushed down, whereby the actuating member
268
is elastically deformed between the first link member
172
and the assist member
270
, so as to elastically push the membrane switch
20
by the bend of the actuating member
268
.
On the other hand, when the movable base element
262
is shifted to and placed at the front limit of movement thereof, the first and second link members
172
,
174
are automatically folded-up inside the key top
12
, as already described, and the key top
12
is thus displaced to the retracted position where the key-entry operation is impossible. During this operation, the assist member
270
is shifted frontward together with the movable base element
262
and is located at the above-described second position (see FIG.
26
C). Accordingly, the assist member
270
cannot be engaged with the tongue
268
a
of the actuating member
268
, and thus the actuating member
268
is not elastically deformed even if the key top
12
goes down. Consequently, the key top
12
is smoothly displaced to the retracted position due to the weight thereof while the actuating member
268
does not close the membrane switch
20
.
As will be appreciated, the key switch
260
can provide various effects essentially equivalent to those of the key switch
170
of the sixth embodiment. If a keyboard is structured by incorporating therein a plurality of key switches
260
, it is possible to hold the key top
12
of each key switch
260
in the initial projecting position for a key-entry operation through the first and second link members
172
,
174
when the keyboard is to be used, by shifting the plate spring
266
and the assist member
270
together with the movable base element
262
to the rear limit of movement, and also to smoothly displace the key top
12
of each key switch
260
into the retracted position making the key-entry operation impossible when the keyboard is not to be used, by shifting the plate spring
266
and the assist member
270
together with the movable base element
262
to the front limit of movement.
When the key top
12
is in the retracted position, the link members
172
,
174
and the actuating member
268
are folded-up and accommodated inside the key top
12
, so that the dimension of the key top
12
can be decreased particularly in the height direction, in comparison with the conventional key switch using the dome-shaped elastic actuating member. Consequently, according to the key switch
260
, it is possible to significantly reduce the entire height or thickness of the keyboard and can improve the portability thereof.
In the above ninth embodiment, the plate spring
266
and the assist member
270
may be formed integrally with the movable base element
262
by stamping and bending a sheet metal material. The other elastic members having liner characteristics, such as a compression coil spring, an extension coil spring, etc., may be used instead of the plate spring
266
. Also, the actuating member
268
may be formed integrally with the first link member
172
, both made from the same resinous material or same metal. Alternatively, the metal actuating member
268
may be formed integrally with the resinous first link member
172
through an insert molding process.
Tenth Embodiment
FIG. 27
shows a key switch
280
according to a tenth embodiment of the present invention. The key switch
280
is preferably used in a relatively thin keyboard having an improved portability, in which the key top of each key switch is positively displaced to a retracted position lower during the inoperating (or carrying) state of the keyboard. The key switch
280
includes the alternative constructions of an actuating member for a membrane switch and of means for eliminating the function of the actuating member when the key top is in a retracted position, and the remaining structure of the key switch
280
is substantially the same as that of the key switch
260
of the ninth embodiment. Therefore, the same or similar components are denoted by the common reference numerals, and a detailed description thereof is not repeated.
That is, the key switch
280
includes a key top
12
, a fixed base element
14
(hereinafter referred to as a base
14
), a pair of link members
172
,
174
, a movable base element
262
, a membrane sheet
22
with a membrane switch
20
, and a support plate
42
. The movable base element
262
is provided integrally with a plate spring
266
as an elastic member, but does not include the assist member
270
in the key switch
260
.
The key switch
280
further includes an actuating member
282
for actuating the membrane switch
20
, which is in the form of a second plate spring integrally provided on the first link member
172
, in the same manner as the actuating member
268
in the key switch
260
. The actuating member
282
is fixedly joined at one end thereof to the generally longitudinally center of one arm
176
of the first link member
172
, and extends at the other free end thereof to close with the bar
178
of the first link member
172
so as to form a bend with a convex surface facing downward. However, the extension as the tongue
268
a
of the actuating member
268
in the key switch
260
is not provided to the free end of the actuating member
282
.
When the key top
12
is located at the initial highest position in the key-entry operation, the free end of the actuating member
282
is located above the center opening
15
of the base
14
. When the key top
12
is pushed down to and located at a predetermined position, the free end of the actuating member
282
enters into the center opening
15
of the base
14
, and elastically pushes the membrane switch
20
by the convex surface of the bent of the actuating member
282
. The actuating member
282
may be formed integrally with the first link member
172
, both made from the same resinous material or same metal. Alternatively, the metal actuating member
282
may be formed integrally with the resinous first link member
172
through an insert molding process.
In the key switch
280
, the membrane sheet
22
can be shifted together with the movable base element
262
in a forward/backward direction relative to the base
14
(shown by an arrow A), to eliminate the function of the actuating member
282
when the key top
12
in the retracted position. Therefore, the membrane switch
20
can be shifted between a first position where the membrane switch
20
is pushed by the free end of the actuating member
282
to close an electric circuit and a second position where the membrane switch
20
is frontwardly away from the free end of the actuating member
282
to keep the electric circuit open, during the time when the key top
12
is located at the predetermined pushed-down position.
The membrane sheet
22
is provided in the rear of the membrane switch
20
with an opening
284
penetrating the membrane sheet
22
, for receiving the free end of the actuating member
282
. Also, the support plate
42
is provided with an opening
286
at a location under the membrane switch
20
located in the first position, for receiving the free end of the actuating member
282
.
During the time when the key switch
280
is held in the condition for the key-entry operation, i.e., when the movable base element
262
and the membrane sheet
22
are placed at the rear limit of movement thereof, if no external force is applied to the key top
12
, the plate spring
266
urges or biases the key top
12
toward the initial position vertically upwardly away from the base
14
and supports the key top
12
in this position, through the mutually interlocked first and second link members
172
,
174
. In this state, the free end of the actuating member
282
is located above the center openings
15
,
264
of the base
14
and the movable base element
262
, so as not to contact with the membrane sheet
22
, as shown in FIG.
28
A. Also, the membrane switch
20
is located in the first position.
When the key top
12
is pushed down by the key-entry operation, the plate spring
266
is deformed while exerting biasing or elastic restoring force to the bar
178
(i.e., the loading portion) of the first link member
172
in a direction substantially orthogonal to the pushing-down direction of the key top
12
. When the key top
12
reaches the predetermined pushed-down position, the free end of the actuating member
282
enters into the center openings
15
,
264
of the base
14
and the movable base element
262
, so as to be abutted, at the convex surface of the bend of the actuating member
282
, onto the surface of the membrane sheet
22
, and to elastically push the membrane switch
20
, as shown by a broken line in FIG.
28
A.
When the movable base element
262
and the membrane sheet
22
are shifted to and placed at the front limit of movement thereof, the first and second link members
172
,
174
are automatically folded-up inside the key top
12
, because the plate spring
266
, which serves to support the first link member
172
, is also shifted frontward, and the key top
12
is thus displaced to the retracted position where the key-entry operation is impossible. During this operation, the membrane switch
20
is shifted frontward to be located at the above-described second position, and the openings
284
,
286
formed respectively in the membrane sheet
22
and the support plate
42
are aligned with each other as well as with the center opening
264
of the movable base element
262
. Accordingly, the free end of the actuating member
282
is not abutted onto the membrane switch
20
even if the key top
12
goes down, but is received in the center opening
264
and the openings
284
,
286
. Consequently, the key top
12
is smoothly displaced to the retracted position due to the weight thereof while the actuating member
282
does not close the membrane switch
20
.
As will be appreciated, the key switch
280
can provide various effects essentially equivalent to those of the key switch
170
of the sixth embodiment. If a keyboard is structured by incorporating therein a plurality of key switches
280
, it is possible to hold the key top
12
of each key switch
280
in the initial projecting position for a key-entry operation through the first and second link members
172
,
174
when the keyboard is to be used, by shifting the plate spring
266
together with the movable base element
262
to the rear limit of movement and shifting the membrane switch
20
into the first position, and also to smoothly displace the key top
12
of each key switch
280
into the retracted position making the key-entry operation impossible when the keyboard is not to be used, by shifting the plate spring
266
together with the movable base element
262
to the front limit of movement and shifting the membrane switch
20
into the second position.
When the key top
12
is in the retracted position, the link members
172
,
174
and the actuating member
282
are folded-up and accommodated inside the key top
12
, so that the dimension of the key top
12
can be decreased particularly in the height direction, in comparison with the conventional key switch using the dome-shaped elastic actuating member. Consequently, according to the key switch
280
, it is possible to significantly reduce the entire height or thickness of the keyboard and can improve the portability thereof.
Eleventh Embodiment
FIG. 29
shows a key switch
290
according to an eleventh embodiment of the present invention. The key switch
290
is preferably used in a relatively thin keyboard having an improved portability, in which the key top of each key switch is positively displaced to a retracted position during the inoperating (or carrying) state of the keyboard.
The key switch
290
includes a key top
292
with an operation surface
292
a
adapted to be keyed by an operator's finger, a fixed base element
294
(hereinafter referred to as a base
294
) shaped as a rectangular frame and arranged beneath the key top
292
, a pair of link members
296
,
298
for supporting the key top
292
above a major surface
294
a
of the base
294
and directing or guiding the key top
292
in a vertical or up and down direction, a movable base element
300
arranged under the base
294
, a membrane sheet
22
provided with a membrane switch
20
and disposed under the movable base element
300
, and a support plate
42
for supporting the membrane sheet
22
. The movable base element
300
cooperates with the base
294
(i.e., the fixed base element) to serve as a base of the key switch
290
. The membrane switch
20
, the membrane sheet
22
and the support plate
42
have substantially the same structures as those in the key switch
10
of the first embodiment shown in
FIG. 1
, and thus the detailed description thereof is not repeated.
The key top
292
is a dish-like member having a generally rectangular profile, and includes two pairs of pivot supports
302
, both pairs being disposed adjacent to each other at a generally center of the key top
292
in a forward/backward direction (a leftward/rightward direction in
FIG. 31A
) on an inner surface
292
b
opposite to the operation surface
292
a
(only two pivot supports
302
are shown). One pair of pivot supports
302
located rearward (rightward in
FIG. 31A
) are spaced from each other, and the other pair of pivot supports
302
located frontward (leftward in
FIG. 31A
) are arranged close to each other. Please note that the “front” and the “rear” of the key switch
290
are hereinafter defined in a manner as described above in convenience, but, of course, the “front” and the “rear” in an actual use are not restricted in this definition.
Each of the pivot supports
302
is formed as a small plate uprightly projecting from the inner surface
292
b
of the key top
292
, and includes a bearing hole
302
a
penetrating through the thickness of the plate and a slit
302
b
extending generally perpendicularly to the inner surface
292
b
to communicate with the bearing hole
302
a
. Two pivot supports
302
of each pair are positioned on the inner surface
292
b
of the key top
292
in such a manner that the bearing holes
302
a
of these pivot supports
302
are aligned with each other in a penetrating direction thereof.
The base
294
is a frame-like member having a generally rectangular profile, and includes a generally rectangular center opening
304
covered with the key top
292
. The base
294
is provided, along opposed inner edges
294
b
thereof defining the center opening
304
, with two pairs of slide supports
306
,
308
, one pair being spaced from the other in a longitudinal or forward/backward direction, and two slide supports
306
,
308
in each pair being spaced from each other.
Each of the slide supports
306
disposed adjacent to the front end of the base
294
includes a reverse U-shaped wall part projecting from the major surface
294
a
and the inner edge
294
b
of the base
294
adjacent to the front inner edge
294
c
of the latter, and a bearing slot
306
a
extending generally parallel to the major surface
294
a
is formed inside the wall part. Each of the slide supports
308
disposed adjacent to the rear end of the base
294
includes a reverse U-shaped wall part projecting from the major surface
294
a
and the inner edge
294
b
of the base
294
adjacent to the rear inner edge
294
c
of the latter, and a bearing slot
308
a
extending generally parallel to the major surface
294
a
is formed inside the wall part. These front and rear bearing slots
306
a
,
308
a
open to a bottom side of the base
294
. Two slide supports
306
,
308
of each pair are positioned on the opposed inner edges
294
b
of the base
294
in such a manner that the bearing slots
306
a
,
308
a
of respective slide supports
306
,
308
are aligned and faced with each other.
The pair of link members
296
,
298
are structured as a first link member
296
and a second link member
298
, which are assembled together so as to be provided with a generally X-shape in a side view. The first link member
296
includes two arms
310
extending parallel to each other, and a connecting part
312
mutually connecting the arms
310
near one ends of the latter. Axles
314
are provided on one ends of the arms
310
to mutually coaxially project on the opposite sides to the connecting part
312
. Axles
316
are provided on the other ends of the arms
310
to mutually coaxially project on the same sides as the axles
314
. The second link member
298
includes two arms
318
extending parallel to each other, and a connecting part
320
mutually connecting the arms
318
. Axles
322
are provided on one ends of the connecting part
320
to mutually coaxially project and face outwardly away from each other. Axles
324
are provided on the other ends of the arms
318
away from the connecting part
320
to mutually coaxially project and face inwardly toward each other.
The first and second link members
296
,
298
are meshed with each other at a toothed end of each link members
296
,
298
. More particularly, each of the arms
310
of the first link member
296
is provided on the inner side opposite to the axle
316
with one teeth
326
extending toward the connecting part
312
, and each of the arms
318
of the second link member
298
is provided on the outer side opposite to the axle
324
with two tooth
328
extending toward the axle
322
. The first and second link members
296
,
298
are pivotably connected with each other by intermeshings between the one tooth
326
and the corresponding two teeth
328
provided on the arms
310
,
318
, respectively.
The axles
314
formed on one ends of the arms
310
of the first link member
296
are slidably fitted or received in the respective bearing slots
306
a
of the front slide supports
306
on the base
294
, and the axles
316
formed on the other ends of the arms
310
of the first link member
296
are pivotably fitted or received in the respective bearing holes
302
a
of the rear pivot supports
302
on the key top
292
, whereby the first link member
296
is arranged between the key top
292
and the base
294
in such a manner as to be pivotable about the axles
316
on the key top
292
.
The axles
322
formed on one ends of the connecting part
320
of the second link member
298
are slidably fitted or received in the respective bearing slots
308
a
of the rear slide supports
308
on the base
294
, and the axles
324
formed on the other ends of the arms
318
of the second link member
298
are pivotably fitted or received in the respective bearing holes
302
a
of the front pivot supports
302
on the key top
292
, whereby the second link member
298
is arranged between the key top
292
and the base
294
in such a manner as to be pivotable about the axles
324
on the key top
292
.
The above-described structure of the first and second link members
296
,
298
substantially corresponds to the structure of the first and second link members
232
,
234
in the modification (
FIG. 24
) of the key switch
230
of the eighth embodiment, except for the generally X-shaped, intersected arrangement of link members
296
,
298
. Therefore, in this embodiment, the axles
314
of the first link member
296
and the axles
322
of the second link member
298
constitute sliding portions of the respective link members
296
,
298
. The first and second link members
296
,
298
are interlocked to each other through the intermeshings between the respective one tooth
326
and the respective two teeth
328
so as to be synchronously pivotable, so that the key top
292
is permitted to be subjected to a parallel displacement in a substantially vertical direction in relation to the major surface
294
a
of the base
294
, while keeping a predetermined posture of the key top
292
wherein the operation surface
292
a
thereof is generally parallel to the major surface
294
a.
The key switch
290
further includes a pair of plate springs
330
,
332
or elastic members, disposed between the base
294
as well as the movable base element
300
and the first and second link members
296
,
298
, which act as biasing means for elastically urging upward the key top
292
away from the base
294
. One plate spring
330
is integrally joined at one end thereof to one end of one arm
310
of the first link member
296
in the vicinity of one axle
314
, and is arranged at the other free end thereof close to the connecting part
312
and near the front inner edge
294
c
of the base
294
. The other plate spring
332
is integrally joined at one end thereof to one end of the connecting part
320
of the second link member
298
in the vicinity of one axle
322
, and is arranged at the other free end thereof close to the connecting part
320
and near the rear inner edge
294
c
of the base
294
.
The base
294
is also provided with a wall
334
extending upward from the major surface
294
a
along the rear inner edge
294
c
. A bump
336
is formed on the wall
334
so as to be capable of coming into contact with the free end of the plate spring
332
joined to the second link member
298
. The movable base element
300
is also provided with a vertical wall
338
extending through the center opening
304
of the base
294
and projecting above the major surface
294
a
. The wall
338
is fixedly joined at one end thereof to the movable base element
300
, so that the other free end thereof is arranged to be capable of coming into contact with the free end of the plate spring
330
joined to the first link member
296
.
The movable base element
300
can be shifted in a forward/backward direction (shown by an arrow A) of the key switch
290
between the base
294
and the membrane sheet
22
. Therefore, the wall
338
joined to the movable base element
300
can be shifted together with the movable base element
300
in the forward/backward direction in relation to the base
294
. The plate spring
330
joined to the first link member
296
optionally acts, in connection with the shifted position of the wall
338
, as a compression spring between the first link member
296
and the movable base element
300
. Also, the plate spring
332
joined to the second link member
298
optionally acts, in connection with the shifted position of the wall
338
, as a compression spring between the second link member
298
and the base
294
. Accordingly, in the key switch
290
, it is possible to change the distance between the wall
338
arranged at a front side in the center opening
304
of the base
294
and the bump
336
arranged at a rear side in the center opening
304
, and thereby to displace the key top
292
between the initial projecting position and the retracted position during inoperating condition, as described below.
When the movable base element
300
is located at the rear limit of movement thereof, the plate spring
330
and the plate spring
332
cooperate with the wall
338
and the bump
336
, respectively, so as to act in the same manner as the plate spring
250
shown in
FIG. 24
to maintain the key switch
290
in a condition for a key-entry operation. That is, the first and second link members
296
,
298
act in accordance with the operational principle as described with reference to
FIG. 19
, because the axles
316
,
318
to be connected with the key top
292
can go down to a lower level (illustrated by an angleφ in
FIG. 30B
) than loading portions of the link members
296
,
298
, to which the biasing force of the plate springs
330
,
332
is applied (see FIGS.
30
A and
30
B). In this respect, the plate springs
330
,
332
are linear characteristics springs of simple structures, and thus exert the biasing force, assuming a linear relationship with the shifting amount or displacement of the connecting parts
312
,
320
, onto the first and second link members
296
,
298
, respectively.
When the wall
338
is shifted frontward, by an actuating mechanism (not shown), together with the movable base element
300
to be located at the front limit of movement thereof, the wall
338
and the bump
336
no longer support the first and second link members
296
,
298
, and thereby the first and second link members
296
,
298
are automatically folded-up inside the key top
292
due to their weight and of key top
292
. As a result, the key top
292
is displaced to the retracted position lower than the initial position. In the retracted position, the plate springs
330
,
332
are kept free of any substantial elastic deformation.
The key switch
290
further includes an actuating member
340
for actuating the membrane switch
20
, which is in the form of a second plate spring integrally provided on the movable base element
300
, instead of the compression coil spring provided on the inner surface
12
b
of the key top
12
in the key switch
170
of FIG.
17
. The actuating member
340
is fixedly joined at one end thereof to a front inner edge of a generally center opening
342
of the movable base element
300
and extends rearward so that the other free end of the actuating member
340
is disposed under the connecting part
320
of the second link member
298
. The actuating member
340
is provided at the free end thereof with a tongue
340
a
(
FIGS. 31A
to
31
C) extending toward the membrane switch
20
of the membrane sheet
22
. The actuating member
340
can be shifted together with the movable base element
300
in the forward/backward direction of the key switch
290
.
As shown in
FIG. 31A
, when the key switch
290
is held in the condition for the key-entry operation, i.e., when the movable base element
300
is placed at the rear limit of movement thereof, the actuating member
340
is located in a first position under a bulge
320
a
formed at a bottom of the connecting part
320
of the second link member
298
. During this condition, if no external force is applied to the key top
292
, the plate springs
330
,
332
urge or bias the key top
292
toward the initial position vertically upwardly away from the base
294
and support the key top
292
in this position, through the mutually interlocked first and second link members
296
,
298
. In this state, the tongue
340
a
at the free end of the actuating member
340
is located is the center opening
304
of the base
294
, so as not to contact with the membrane sheet
22
.
When the key top
292
is pushed down by the key-entry operation, the plate spring
330
and the plate spring
332
cooperate with the wall
338
and the bump
336
, respectively, to be deformed while exerting biasing or elastic restoring force to the neighborhoods (i.e., the loading portions) of the connecting parts
312
,
320
of the first and second link members
296
,
298
in a direction substantially orthogonal to the pushing-down direction of the key top
292
. When the key top
292
reaches the predetermined pushed-down position, the bulge
320
a
of the connecting portion
320
of the second link member
298
enters into the center opening
304
of the base
294
, so as to come into contact with the actuating member
340
. Then, the key top
292
is further pushed down, whereby the bulge
320
a
pushes the actuating member
340
to elastically deform the latter, and the tongue
340
a
of the actuating member
340
in turn pushes the membrane switch
20
to close an electric circuit (see FIG.
31
B).
On the other hand, as shown in
FIG. 31C
, when the wall
338
is shifted together with the movable base element
300
upto the front limit of movement thereof, the first and second link members
296
,
298
are automatically folded-up inside the key top
292
, as already described, and the key top
292
is thus displaced to the retracted position where the key-entry operation is impossible. During this operation, the actuating member
340
is shifted frontward together with the movable base element
300
and is located at a second position away from the bulge
320
a
of the second link member
320
. Accordingly, the actuating member
340
is not elastically deformed even if the key top
292
goes down, and thus the tongue
340
a
is not abutted to the membrane switch
20
. Consequently, the key top
292
is smoothly displaced to the retracted position due to the weight thereof while the actuating member
340
does not close the membrane switch
20
.
The key switch
290
further includes a pair of detents
344
integrally formed with the movable base element
300
, as means for selectively securing the axles
314
,
322
(the sliding portions) of at least one of the first and second link members
296
,
298
in relation to the base
294
and the movable base element
300
. The detents
344
are fixedly joined at one ends thereof to the movable base element
300
, and respectively extend into the bearing slots
306
a
of the front slide supports
306
of the base
294
, so that the other free ends of the detents
344
are respectively placed in the rear of the axles
314
of the first link member
296
. The detents
344
can be shifted together with the movable base element
300
in the forward/backward direction of the key switch
290
inside the respective bearing slots
306
a
of the base
294
.
As shown in
FIGS. 31A
,
31
B and
32
, when the movable base element
300
is placed at the rear limit of movement thereof, each detent
344
is located at a position where the detent
344
cannot interfere with the shifting motion of each axle
314
of the first link member
296
in each bearing slot
306
a
of the base
294
. As shown in
FIGS. 31C and 33
, when the movable base element
300
is placed at the front limit of movement thereof, each detent
344
is also shifted frontward in each bearing slot
306
a
of the base
294
, so as to hold each axle
314
of the first link member
296
between the detent
344
and the wall part of the slide support
306
. In this manner, the mutually interlocked first and second link members
296
,
298
are fixedly held in a condition where the link members
296
,
298
are folded-up inside the key top
292
, and thus the key top
292
is secured in the retracted position.
As will be appreciated, the key switch
290
can provide various effects essentially equivalent to those of the key switch
230
of the eighth embodiment. If a keyboard is structured by incorporating therein a plurality of key switches
290
, it is possible to hold the key top
292
of each key switch
290
in the condition for a key-entry operation through the first and second link members
296
,
298
when the keyboard is to be used, by shifting the wall
338
together with the movable base element
300
to the rear limit of movement and by locating the actuating member
340
at the first position, and also to smoothly displace the key top
292
of each key switch
290
into the retracted position making the key-entry operation impossible when the keyboard is not to be used, by shifting the wall
338
together with the movable base element
300
to the front limit of movement and by locating the actuating member
340
at the second position.
When the key top
292
is in the retracted position, the link members
296
,
298
are folded-up and accommodated inside the key top
292
, so that the dimension of the key top
292
can be decreased particularly in the height direction, in comparison with the conventional key switch using the dome-shaped elastic actuating member. Consequently, according to the key switch
290
, it is possible to significantly reduce the entire height or thickness of the keyboard and can improve the portability thereof. Further, according to the key switch
290
, it is possible to effectively eliminate the damage and noise caused by the fluctuation of the key top
292
.
While the invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the following claims.
Claims
- 1. A key switch comprising:a base; a key top arranged above said base; a pair of link members interlocked to each other and operatively engaged with said base and said key top to support said key top above said base and direct said key top in a vertical direction, each of said link members including a sliding portion slidably and shiftably engaged with either one of said base and said key top; at least one elastic member disposed between at least one of said link members and either one of said base and said key top with which said sliding portion is engaged, to exert biasing force, relative to a shifting amount of said sliding portion, onto said at least one of said link members in a direction different from said vertical direction; and a switching mechanism for selectively opening and closing an electric circuit in connection with a vertical movement of said key top; wherein said at least one elastic member is fixedly joined to said at least one of said link members and is abutted against said base.
- 2. The key switch of claim 1, wherein said at least one elastic member exerts biasing force assuming a linear relationship with said shifting amount of said sliding portion, onto said at least one of said link members.
- 3. The key switch of claim 1, wherein said at least one elastic member exerts biasing force in a direction substantially orthogonal to said vertical direction, onto said at least one of said link members.
- 4. The key switch of claim 1, wherein said at least one of said link members is provided with a loading portion separately from said sliding portion, said loading portion being formed at a position angularly displaced from said sliding portion about a mutually connecting point of said pair of link members, said biasing force being applied onto said loading portion.
- 5. The key switch of claim 4, wherein said loading portion is shifted in a motion different from said sliding portion when said sliding portion is shifted.
- 6. The key switch of claim 1, wherein said elastic member comprises a compression spring.
- 7. The key switch of claim 1, wherein said elastic member comprises a plate spring.
- 8. The key switch of claim 1, wherein said pair of link members are arranged to mutually intersect and are pivotably connected relative to each other at an intersection thereof, wherein a first one of said link members is engaged slidably at one end thereof with said base and rotatably at another end thereof with said key top, said sliding portion being provided on said one end of said first link member, and wherein a second one of said link members is engaged rotatably at one end thereof with said base and slidably at another end thereof with said key top, said sliding portion being provided on said other end of said second link member.
- 9. The key switch of claim 1, wherein said pair of link members are arranged to mutually intersect and are pivotably and slidably connected relative to each other at an intersection thereof, and wherein each of said link members is engaged slidably at one end thereof with said base and rotatably at another end thereof with said key top, said sliding portion being provided on said one end of said each link member.
- 10. The key switch of claim 1, wherein said pair of link members are meshed with each other at a toothed end of each of said link members, and wherein each of said link members is engaged slidably at one end thereof with said base and rotatably at another end thereof with said key top, said sliding portion being provided on said one end of said each link member, said toothed end being provided adjacent to said other end of said each link member.
- 11. The key switch of claim 10, wherein said pair of link members are arranged to intersect with each other.
- 12. The key switch of claim 1, wherein said switching mechanism comprises a membrane switch arranged in an opening formed in said base beneath said key top, and an actuating member for pushing said membrane switch to close said electric circuit when said key top goes down and is located at a predetermined position above said base.
- 13. The key switch of claim 12, wherein said actuating member is provided on said key top, and enters into said opening of said base to elastically push said membrane switch when said key top is located at said predetermined position.
- 14. The key switch of claim 12, wherein said actuating member is provided on at least one of said link members, and enters into said opening of said base to elastically push said membrane switch when said key top is located at said predetermined position.
- 15. The key switch of claim 14, further comprising an assist member movable between a first position where said assist member comes into engagement with said actuating member and a second position where said assist member is away from said actuating member, during a time when said key top is located at said predetermined position, and wherein said actuating member comes into engagement with said assist member to push said membrane switch.
- 16. The key switch of claim 12, wherein said actuating member is disposed above said membrane switch, and wherein a part of said link members enters into said opening of said base to push said actuating member when said key top is located at said predetermined position, whereby said actuating member pushes said membrane switch.
- 17. The key switch of claim 16, wherein said actuating member is movable between a first position where said actuating member is pushed by said part of said link members upon said key top is located at said predetermined position and a second position where said actuating member is away from said part of said link members.
- 18. The key switch of claim 12, wherein said membrane switch is movable between a first position where said membrane switch is pushed by said actuating member to close said electric circuit and a second position where said membrane switch is away from said actuating member to keep said electric circuit open, during a time when said key top is located at said predetermined position.
- 19. The key switch of claim 1, further comprises means for selectively securing said sliding portion of said at least one of said link members in relation to either one of said base and said key top with which said sliding portion is engaged, to hold said key top at a desired lowered position.
- 20. The key switch of claim 1, wherein said base includes a fixed base element engaged with said pair of link members and a movable base element disposed under said fixed base element in such a manner as to be movable with relation to said fixed base element.
- 21. The key switch of claim 20, wherein said at least one elastic member is fixedly connected to said movable base element and abutted onto said at least one of said link members.
- 22. The key switch of claim 20, wherein said at least one elastic member is fixedly connected to said at least one of said link members and abutted onto at least one vertical wall fixedly joined to said movable base element.
- 23. The key switch of claim 20, wherein said movable base element is moved in a direction generally parallel to a shifting direction of said sliding portion of said each link member.
- 24. The key switch of claim 20, wherein said movable base element is moved in a direction generally orthogonal to a shifting direction of said sliding portion of said each link member.
- 25. A keyboard comprising a plurality of key switches, each of said key switches being one defined in claim 20, wherein said movable base element of said each key switch is formed as a single large plate extending over said plurality of key switches, said single large plate being movably disposed under a plurality of fixed base elements of said key switches.
- 26. A keyboard comprising a plurality of key switches, each of said key switches being one defined in claim 1.
- 27. A key switch comprising:a base; a key top arranged above said base; a guide member operatively engaged with said base and said key top to support said key top above said base and direct said key top in a vertical direction, said guide member including a sliding portion slidably and shiftably engaged with either one of said base and said key top; an elastic member disposed between said guide member and either one of said base and said key top with which said sliding portion is engaged, to exert biasing force, relative to a shifting amount of said sliding portion, onto said guide member in a direction different from said vertical direction; and a switching mechanism for selectively opening and closing an electric circuit in connection with a vertical movement of said key top; wherein said elastic member is fixedly joined to said guide member and is abutted against said base.
- 28. The key switch of claim 27, wherein said guide member is structured from a plurality of link members interlocked to one another, each of said link members being operatively engaged with said base and said key top and including said sliding portion, and wherein at least one of said link members is associated with at least one said elastic member.
- 29. A key switch comprising:a base; a key top arranged above said base; a pair of link members interlocked to each other and operatively engaged with said base and said key top to support said key top above said base and direct said key top in a vertical direction, each of said link members including a sliding portion slidably and shiftably engaged with either one of said base and said key top; at least one elastic member disposed between at least one of said link members and either one of said base and said key top with which said sliding portion is engaged, to exert biasing force, relative to a shifting amount of said sliding portion, onto said at least one of said link members in a direction different from said vertical direction; and a switching mechanism for selectively opening and closing an electric circuit in connection with a vertical movement of said key top; wherein said at least one of said link members is provided with a loading portion separate from said sliding portion, said loading portion being formed at a position angularly displaced from said sliding portion about a mutually connecting point of said pair of link members, said biasing force being applied onto said loading portion.
- 30. The key switch of claim 29, wherein said loading portion is shifted in a motion different from said sliding portion when said sliding portion is shifted.
- 31. A key switch comprising:a base; a key top arranged above said base; a pair of link members interlocked to each other and operatively engaged with said base and said key top to support said key top above said base and direct said key top in a vertical direction, each of said link members including a sliding portion slidably and shiftably engaged with either one of said base and said key top; at least one elastic member disposed between at least one of said link members and either one of said base and said key top with which said sliding portion is engaged, to exert biasing force, relative to a shifting amount of said sliding portion, onto said at least one of said link members in a direction different from said vertical direction; and a switching mechanism for selectively opening and closing an electric circuit in connection with a vertical movement of said key top, wherein said pair of link members are arranged to mutually intersect and are pivotably and slidably connected relative to each other at an intersection thereof, and wherein each of said link members is engaged slidably at one end thereof with said base and rotatably at another end thereof with said key top, said sliding portion being provided on said one end of said each link member.
- 32. A key switch comprising:a base; a key top arranged above said base; a pair of link members interlocked to each other and operatively engaged with said base and said key top to support said key top above said base and direct said key top in a vertical direction, each of said link members including a sliding portion slidably and shiftably engaged with either one of said base and said key top; at least one elastic member disposed between at least one of said link members and either one of said base and said key top with which said sliding portion is engaged, to exert biasing force, relative to a shifting amount of said sliding portion, onto said at least one of said link members in a direction different from said vertical direction; and a switching mechanism for selectively opening and closing an electric circuit in connection with a vertical movement of said key top wherein said pair of link members are meshed with each other at a toothed end of each of said link members, and wherein each of said link members is engaged slidably at one end thereof with said base and rotatably at another end thereof with said key top, said sliding portion being provided on said one end of said each link member, said toothed end being provided adjacent to said other end of said each link member.
- 33. A key switch comprising:a base; a key top arranged above said base; a pair of link members interlocked to each other and operatively engaged with said base and said key top to support said key top above said base and direct said key top in a vertical direction, each of said link members including a sliding portion slidably and shiftably engaged with either one of said base and said key top; at least one elastic member disposed between at least one of said link members and either one of said base and said key top with which said sliding portion is engaged, to exert biasing force, relative to a shifting amount of said sliding portion, onto said at least one of said link members in a direction different from said vertical direction; and a switching mechanism for selectively opening and closing an electric circuit in connection with a vertical movement of said key top wherein said pair of link members are arranged to intersect with each other at a toothed end of each of said link members, and wherein each of said link members is engaged slidably at one end thereof with said base and rotatably at another end thereof with said key top, said sliding portion being provided on said one end of said each link member, said toothed end being provided adjacent to said other end of said each link member.
- 34. A key switch comprising:a base; a key top arranged above said base; a pair of link members interlocked to each other and operatively engaged with said base and said key top to support said key top above said base and direct said key top in a vertical direction, each of said link members including a sliding portion slidably and shiftably engaged with either one of said base and said key top; at least one elastic member disposed between at least one of said link members and either one of said base and said key top with which said sliding portion is engaged, to exert biasing force, relative to a shifting amount of said sliding portion, onto said at least one of said link members in a direction different from said vertical direction; and a switching mechanism for selectively opening and closing an electric circuit in connection with a vertical movement of said key top, said switching mechanism comprised of a membrane switch arranged in an opening formed in said base beneath said key top, and an actuating member for pushing said membrane switch to close said electric circuit when said key top goes down and is located at a predetermined position above said base, said actuating member is provided on at least one of said link members, and enters into said opening of said base to elastically push said membrane switch when said key top is located at said predetermined position.
- 35. A key switch comprising:a base; a key top arranged above said base; a pair of link members interlocked to each other and operatively engaged with said base and said key top to support said key top above said base and direct said key top in a vertical direction, each of said link members including a sliding portion slidably and shiftably engaged with either one of said base and said key top; at least one elastic member disposed between at least one of said link members and either one of said base and said key top with which said sliding portion is engaged, to exert biasing force, relative to a shifting amount of said sliding portion, onto said at least one of said link members in a direction different from said vertical direction; a switching mechanism for selectively opening and closing an electric circuit in connection with a vertical movement of said key top, said switching mechanism comprised of a membrane switch arranged in an opening formed in said base beneath said key top, and an actuating member for pushing said membrane switch to close said electric circuit when said key top goes down and is located at a predetermined position above said base, said actuating member is provided on at least one of said link members, and enters into said opening of said base to elastically push said membrane switch when said key top is located at said predetermined position; and an assist member movable between a first position where said assist member comes into engagement with said actuating member and a second position where said assist member is away from said actuating member, during a time when said key top is located at said predetermined position, and wherein said actuating member comes into engagement with said assist member to push said membrane switch.
- 36. A key switch comprising:a base; a key top arranged above said base; a pair of link members interlocked to each other and operatively engaged with said base and said key top to support said key top above said base and direct said key top in a vertical direction, each of said link members including a sliding portion slidably and shiftably engaged with either one of said base and said key top; at least one elastic member disposed between at least one of said link members and either one of said base and said key top with which said sliding portion is engaged, to exert biasing force, relative to a shifting amount of said sliding portion, onto said at least one of said link members in a direction different from said vertical direction; and a switching mechanism for selectively opening and closing an electric circuit in connection with a vertical movement of said key top, said switching mechanism comprised of a membrane switch arranged in an opening formed in said base beneath said key top, and an actuating member, disposed above said membrane switch, for pushing said membrane switch to close said electric circuit when said key top goes down and is located at a predetermined position above said base, wherein a part of said link members enters into said opening of said base to push said actuating member when said key top is located at said predetermined position, whereby said actuating member pushes said membrane switch.
- 37. A key switch comprising:a base; a key top arranged above said base; a pair of link members interlocked to each other and operatively engaged with said base and said key top to support said key top above said base and direct said key top in a vertical direction, each of said link members including a sliding portion slidably and shiftably engaged with either one of said base and said key top; at least one elastic member disposed between at least one of said link members and either one of said base and said key top with which said sliding portion is engaged, to exert biasing force, relative to a shifting amount of said sliding portion, onto said at least one of said link members in a direction different from said vertical direction; and a switching mechanism for selectively opening and closing an electric circuit in connection with a vertical movement of said key top, said switching mechanism comprised of a membrane switch arranged in an opening formed in said base beneath said key top, and an actuating member, for pushing said membrane switch to close said electric circuit when said key top goes down and is located at a predetermined position above said base, said actuating member disposed above said membrane switch, and movable between a first position where said actuating member is pushed by said part of said link members upon said key top is located at said predetermined position and a second position where said actuating member is away from said part of said link members, wherein a part of said link members enters into said opening of said base to push said actuating member when said key top is located at said predetermined position, whereby said actuating member pushes said membrane switch.
- 38. A key switch comprising:a base; a key top arranged above said base; a pair of link members interlocked to each other and operatively engaged with said base and said key top to support said key top above said base and direct said key top in a vertical direction, each of said link members including a sliding portion slidably and shiftably engaged with either one of said base and said key top; at least one elastic member disposed between at least one of said link members and either one of said base and said key top with which said sliding portion is engaged, to exert biasing force, relative to a shifting amount of said sliding portion, onto said at least one of said link members in a direction different from said vertical direction; and a switching mechanism for selectively opening and closing an electric circuit in connection with a vertical movement of said key top; wherein said base includes a fixed base element engaged with said pair of link members and a movable base element disposed under said fixed base element in such a manner as to be movable with relation to said fixed base element and said at least one elastic member is fixedly connected to said at least one of said link members and abutted onto at least one vertical wall fixedly joined to said moveable base element.
- 39. A key switch comprising:a base; a key top arranged above said base; a pair of link members interlocked to each other and operatively engaged with said base and said key top to support said key top above said base and direct said key top in a vertical direction, each of said link members including a sliding portion slidably and shiftably engaged with either one of said base and said key top; at least one elastic member disposed between at least one of said link members and either one of said base and said key top with which said sliding portion is engaged, to exert biasing force, relative to a shifting amount of said sliding portion, onto said at least one of said link members in a direction different from said vertical direction; and a switching mechanism for selectively opening and closing an electric circuit in connection with a vertical movement of said key top wherein said base includes a fixed base element engaged with said pair of link members and a movable base element disposed under said fixed base element in such a manner as to be movable with relation to said fixed base element, and said at least one elastic member is fixedly connected to said movable base element and abutted onto said at least one of said link members.
- 40. A key switch comprising:a base; a key top arranged above said base; a pair of link members interlocked to each other to support said key top above said base, each of said link members including a sliding portion slidably and shiftably engaged with either one of said base and said key top; and at least one elastic member disposed between at least one of said link members and either one of said base and said key top with which said sliding portion is engaged, to exert biasing force, relative to a shifting amount of said sliding portion, onto said at least one of said link members in a direction different from said vertical direction, wherein said at least one elastic member is fixedly joined to said at least one of said link members and is abutted against said base.
Priority Claims (2)
Number |
Date |
Country |
Kind |
10-171727 |
Jun 1998 |
JP |
|
10-374470 |
Dec 1998 |
JP |
|
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5-66832 |
Sep 1993 |
JP |
9-27235 |
Jan 1997 |
JP |
9-45182 |
Feb 1997 |
JP |
9-63402 |
Mar 1997 |
JP |
9-190735 |
Jul 1997 |
JP |