Information
-
Patent Grant
-
6396385
-
Patent Number
6,396,385
-
Date Filed
Wednesday, July 26, 200024 years ago
-
Date Issued
Tuesday, May 28, 200222 years ago
-
Inventors
-
Original Assignees
-
Examiners
Agents
- Burns, Doane, Swecker & Mathis, LLP
-
CPC
-
US Classifications
Field of Search
US
- 338 162
- 338 163
- 338 164
- 338 150
- 338 152
- 338 184
-
International Classifications
-
Abstract
A variable resistor includes at least two sliders fixed to the bottom of the concavity of a case, a rotor having an engaging portion for engagement with a tool, on the upper side thereof and rotatably received in the concavity of the case, a resistor substrate having a resistor and an electrode on the underside thereof, capable of being sliding-contacted with the slider, and attached to the underside of the rotor, a cover attached to the opening of the concavity of the case and held in such a manner that the rotor is restrained from rising and is rotatable, and an o ring performing the seal between the inner peripheral surface of the concavity of the case and the outer peripheral surface of the rotor. The rotor has a step portion formed in the outer peripheral surface on the underside thereof with the lower-side portion of the step portion having a short diameter. The resistor substrate is formed into a disk-shape having a diameter longer than that of the short diameter portion of the step portion of the rotor. The O ring is prevented from being released by fixing the resistor substrate to the underside of the rotor.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a seal structure suited for a variable resistor, especially a small-sized variable resistor for use in measuring instruments, communication equipment, sensors, and other industrial apparatuses or equipment.
2. Description of the Related Art
In recent years, there has been the general tendency that apparatuses or equipment is generally miniaturized and small-sized. Regarding the variable resistors which are internal parts of the apparatuses or equipment, the miniaturization has been advanced. In some cases, the apparatuses or equipment is used in a high moisture environment. Accordingly, for the variable resistors, a water-proof, moisture-proof structure is required.
Generally, a variable resistor comprises a case having a concavity, a resistor substrate having a resistor formed on the surface thereof and disposed on the bottom of the concavity of the case,.and a rotor having a slider fixed to the underside thereof and received rotatably in the concavity of the case. The resistance can be changed by sliding the slider on the resistor of the resistor substrate. The above-mentioned rotor is rotatable with respect to the case. Accordingly, sealing between the rotor and the case is needed. For this purpose, a peripheral groove is formed in the outer periphery of the rotor, and an O ring is disposed into the peripheral groove to perform the seal between the rotor and the case.
However, it is a troublesome work to fit the O ring into the peripheral groove of the rotor. Especially, it is very difficult to fit an O ring into the peripheral groove of a small-sized rotor accurately with the O ring being stretched to be enlarged. Fitting defects readily occur, causing imperfect sealing.
As disclosed in Japanese Unexamined Patent Application Publication No. 10-149907, a variable resistor is known, in which a slider is fixed to the bottom of the concavity of a case, a resistor substrate is attached to the underside of a rotor with the resistor of the substrate facing downward, and the slider is slidable in contact with the resistor. In this variable resistor, to render water-proof and moisture-proof properties, an O ring is placed between the upper side of the rotor and the upper side of the case, and by pressing a cover against the O ring, sealing between the rotor and the case is attained.
In this instance, it is unnecessary to fit the O ring onto the rotor with the O ring being stretched to be enlarged as in the above-described first conventional example. The assemblage workability is advantageously enhanced.
However, in the above-described second conventional example, the rotor is in the rising state during assemblage, due to the spring force of the slider, and therefore, the outer peripheral surface of the O ring is not guided by the case, that is, the O ring is simply placed on the outer periphery in the upper side of the rotor. Thus, the O ring is positioned in the unstable state. In this state, the positional slip or release of the O ring readily occurs if a transportation-vibration or the like is applied at assemblage. If the assemblage is carried out in the state that the O ring is positionally slipped, the O ring will be incorrectly engaged there, causing the imperfect sealing.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a variable resistor in which an O ring can be incorporated simply and stably, and imperfect seal is prevented.
It is another object of the present invention to provide a variable resistor of which the number of parts is not increased, and the miniaturization can be realized, due to the O ring of which the release is prevented by utilization of the existing parts.
To achieve the above-described objects, according to the present invention, there is provided a variable resistor which includes a case having a reception space, a slider fixed in the bottom of the reception space of the case, a rotor rotatably received in the reception space of the case, a resistor substrate having a resistor formed on the underside thereof and slidable in contact with the slider, and attached to the underside of the rotor, and an O ring performing the seal between the inner peripheral surface of the reception space of the case and the outer peripheral surface of the rotor, the rotor having a step portion formed in the outer peripheral surface on the underside thereof with the lower-side portion of the step portion having a short diameter, the O ring being fitted onto the short diameter portion of the step portion, the whole or a part of the resistor substrate being formed so as to have a diameter longer than that of the short diameter portion of the step portion of the rotor, and the resistor substrate being fixed to the underside of the rotor whereby the O ring is held between the step portion of the rotor and the resistor substrate.
According to the present invention, there is provided a variable resistor which includes a case-having a reception space, a resistor substrate having a resistor on the upper side thereof and disposed in the bottom of the reception space of the case, a rotor rotatably received in the reception space of the case, a slider slidable in contact with the resistor and attached to the underside of the rotor, and an O ring performing the seal between the inner peripheral surface of the reception space of the case and the outer peripheral surface of the rotor, the rotor having a step portion formed in the outer peripheral surface on the underside thereof with the lower-side portion of the step portion having a short diameter, the O ring being fitted onto the short diameter portion of the step portion, the whole or a part of the slider being provided with a base sheet portion having a diameter longer than that of the short diameter portion of the step portion of the rotor, the base sheet portion of the slider being fixed to the underside of the rotor, whereby the O ring is held between the step portion of the rotor and the base sheet portion of the slider.
In the variable resistor according to the present invention, for assemblage, first, the O ring is fitted onto the short diameter portion of the step portion of the rotor, and the resistor substrate is fixed to the underside of the rotor, whereby the O ring is prevented from being released in the axial direction. In this state, the rotor having the resistor substrate fixed thereto is inserted into the reception space of the case. Since the slider is fixed in the bottom of the reception space of the case, the slider and the resistor substrate are contacted together under pressure so that the rotor gets into the rising state. However, since the O ring is prevented from being released, due:to the step portion of the rotor and the resistor substrate, no positional sipping or releasing occurs. The O ring is prevented from being incorrectly engaged or being detached. Thus, the sealing performance is secured.
Further, for incorporation of the O ring, it is needed simply to insert the O ring onto the short diameter portion of the rotor and attach the resistor substrate to the underside of the rotor. Accordingly, it is unnecessary to stretch the O ring for enlargement. The attachment can be performed simply and stably, even if the rotor and the O ring are small-sized parts. Further, the resistor substrate prevents the O ring from being released. Thus, an especial part for preventing the release of the O ring is unnecessary, and the number of the parts is not increased. In addition, since the resistor substrate is attached directly to the underside of the rotor, the height of the rotor can be reduced, which serves to miniaturize the variable resistor.
As a method of attaching the resistor substrate to the underside of the rotor, adhesion, heat caulking, screwing, and so forth may be used. Preferably, a protuberance is formed in the underside of the rotor, an engaging portion into which the protuberance is fitted under pressure is formed in the resistor substrate, and the protuberance of the rotor is fitted under pressure into the engaging portion of the resistor substrate, whereby the rotor and the resistor substrate are joined together integrally, rotatably. By this, the assemblage can be easily performed as compared with other fixing methods. In addition, desirably, eliminated are conduction defects which may be caused by an adhesive or the like adhering to the resistor and an electrode. After the rotor is incorporated into the case, the resistor substrate is pressed by the spring force of the slider so as to be further fitted onto the rotor. Accordingly, there is no possibility that the resistor substrate is released from the rotor while the variable resistor is used.
As regards the method of incorporating the rotor into the case, it is not restrictive that the slider is fixed to the bottom of the case beforehand, and the rotor is incorporated from the upper side. Preferably, a restraining wall for restraining the rotor from being released upward is formed on the upper end of the case, the rotor is inserted through an open portion provided in the bottom of the case, and a slider block having the slider fixed thereto is fitted into the open portion in the bottom of the case. In this instance, preferably, the gap between the open portion in the bottom of the case and the slider block is sealed with a resin to perform both of the fixing and the sealing between the open portion and the slider block.
According to the present invention, the arrangement of the slider and the resistor substrate is reversed as compared with that according to the first aspect of the present invention. That is, the resistor substrate is provided in the bottom of the case, and the slider is attached to the underside of the rotor. The resistor substrate may be formed separately from or integrally with the case.
In this instance, the O ring is prevented from being released by forming in the slider a base sheet portion of which the diameter is wholly or partially longer than that of the short diameter portion of the step portion of the rotor, and fixing the base sheet portion to the underside of the rotor. Accordingly, the O ring can be securely attached without the positional slipping or departing of the O ring occurring. Also in this instance, for the attachment, the O ring is simply inserted onto the short diameter portion of the step, portion of the rotor. Thus, the incorporation work can be easily performed, even if the rotor and the O ring are small-sized parts.
Preferably, a protuberance is formed in the underside of the rotor, and fitted under pressure into an engaging portion formed in the base sheet portion of the slider, whereby the rotor and the base sheet portion of the slider are joined together. This assemblage can be easily performed as compared with other fixing methods.
Also preferably, the rotor is incorporated into the case from the lower side thereof, the open portion in the bottom of the case is closed with the resistor substrate, and moreover, is sealed with a resin.
Preferably, the upper side of the case is provided with an open portion to which a part of the rotor is exposed, and in the open portion of the case, a cover for restraining the rotor from rising and holding the rotor rotatably is attached. In this instance, the rotor can be incorporated into the case form the upper side thereof. If the case is formed so as to be bottomed, it is unnecessary to seal the bottom of the case with a resin.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1
is an exploded perspective view of a variable resistor according to a first embodiment of the present invention;
FIG. 2
is a plan view of the variable resistor of
FIG. 1
;
FIG. 3
is a cross-sectional view taken along line A—A in
FIG. 2
;
FIG. 4
is a bottom view of the variable resistor of
FIG. 1
;
FIG. 5
is a plan view of the case of the variable resistor of
FIG. 1
;
FIG. 6
is a plan view of the rotor and the resistor substrate of the variable resistor of
FIG. 1
;
FIG. 7
is a side view of the rotor and the resistor substrate shown in
FIG. 6
;
FIG. 8
is a bottom view of the rotor and the resistor substrate shown in
FIG. 6
;
FIG. 9
is a cross sectional view of a variable resistor according to a second embodiment of the present invention;
FIG. 10
is a side view of a rotor and a slider used in the variable resistor shown in
FIG. 9
;
FIG. 11
is a bottom view of the rotor and the slider shown in
FIG. 10
;
FIG. 12
is a cross sectional view of a variable resistor according to a third embodiment of the present invention;
FIG. 13
is a cross sectional view of a variable resistor according to a fourth embodiment of the present invention;
FIG. 14
is a side view of a rotor and a slider used in the variable resistor shown in
FIG. 13
, and
FIG. 15
is a bottom view of the rotor and the slider shown in FIG.
14
.
DESCRIPTION OF PREFERRED EMBODIMENT
FIGS. 1
to
8
show a variable resistor according to a first embodiment of the present invention. The variable resistor
1
comprises a case
2
, slider
9
,
10
, and
11
, lead terminals
15
,
16
, and
17
, a rotor
18
, a resistor substrate
24
, an O ring
28
, and a metallic cover
30
.
The case
2
, which is required to be durable to heat generated at soldering and can act stably in a high temperature environment, is formed from a thermoplastic resins such as polyamide types with high heat resistance, e.g.,
46
nylon, polyphenylenesulfide, polybutyleneterephthalate, liquid crystal polymers, or the like, or a thermosetting resin such as epoxy, diallyl phthalate, or the like. A bottomed concavity
3
having a circular transverse cross-section, which is an example of the receiving space, is formed in the case
2
, and is designed in such a manner that the rotor
18
received in the concavity
3
can be smoothly rotated. A tapered guide surface
3
a
for guiding the O ring
28
is formed in the upper edge of the concavity
3
of the case
2
. Engaging holes
4
to be engaged with the attachment claws
34
of the cover
30
are formed in the four corners on the upper side of the case
2
, respectively. Engaging recesses
8
to be engaged with the engaging pieces
35
of the cover
30
are formed in the four side portions on the upper side of the case
2
, respectively.
The sliders
9
,
10
, and
11
are formed from a metallic sheet of copper alloys such as nickel silver, stainless steel or the like, insert-molded with the underside of the case
2
, and partially exposed to the bottom surface of the concavity
3
of the case
2
. The sliders
9
,
10
and
11
each have a double-folding structure, as shown in FIG.
3
. In the upper sheet portions of the sliders
9
,
10
, and
11
, comb-shaped arms
9
a
,
10
a
, and
11
a
are formed in such a manner as to protrude obliquely upward from the bottom surface of the concavity
3
. Contacts
9
b
,
10
b
, and
11
b
(see
FIG. 5
) are formed in the tips of the arms
9
a
,
10
a
, and
11
a
, respectively (see FIG.
5
). The contacts
9
b
,
10
b
, and
11
b
can be contacted with the center electrode
26
, the outer peripheral electrode
27
, and the resistor
25
of the resistor substrate
24
which will be described later.
A land (not shown) is provided with the slider
9
. The land is exposed to an opening
5
for connection of a lead terminal provided on the underside of the case
2
(see FIG.
4
). Similarly, a land (not shown) is provided with the slider
10
and exposed to an opening
6
for connection of a lead terminal provided on the underside of the case
2
. The lead portion
11
c
of the slider
11
, led out through the side face of the case
2
, is folded from the side face onto the underside of the case
2
.
In this embodiment, as the lead terminals
15
,
16
, and
17
, pin terminals each having a circular cross-section are employed, as shown in
FIGS. 1 and 4
. The lead terminals
15
and
16
are connected to the lands of the sliders
9
and
11
exposed to the openings
5
and
6
formed in the underside of the case
2
, respectively, in a method such as soldering, resistance welding, supersonic welding, or the like. The lead terminal
17
is connected to the lead portion
11
c
of the slider
11
folded onto the underside of the case
2
.
The rotor
18
is formed into a substantially columnar shape, e.g., from a ceramic material such as alumina, or a heat resistant resin such as polyphenylenesulfide or the like. The outer peripheral surface of the case
2
are positioned near to the inner peripheral surface of the concavity
3
. Tool-engagement grooves
19
with which a tool such as a screwdriver or the like is to be engaged are formed in the center of the upper side of the rotor
18
, and exposed upward in the concavity
3
of the case
2
. An arrow portion
19
a
for indicating the direction of the rotor
18
is provided at the tool-engagement grooves
19
. An escaping groove
20
having a substantially arch shape is provided around the tool-engagement grooves
19
, and a stopper
21
is provided at a predetermined position in the escaping groove
20
. A round-rod shaped protuberance
22
a
and a claw-shaped protuberance
22
b
are provided in the underside of the rotor
18
(see FIG.
8
). A step portion
23
is formed in the outer periphery on the underside of the rotor
18
with the lower portion of the step portion
23
having a short diameter.
The resistor substrate
24
is attached to the underside of the rotor
18
. The resistor substrate
24
is formed into a disk shape from a ceramic material such as alumina or the like, a heat resistant resin such as polyphenylenesulfide or the like. The diameter of the resistor substrate
24
is longer than that of the short diameter portion
23
a
of the step portion
23
of the rotor
18
and is shorter than or equal to that of the large diameter portion
23
b
of the step portion
23
. The resistor substrate
24
is provided with a hole
24
a
and a notch
24
b
of which the shapes are conformed to the protuberances
22
a
and
22
b
, respectively. The rod-like protuberance
22
a
is inserted under pressure into the hole
24
a
, and the claw-like protuberance
24
b
is engaged with the notch
24
b
, so that the resistor substrate
24
is fixed to the rotor
18
concentrically and securely rotatably therewith. When the resistor substrate
24
is attached to the rotor
18
, a reception groove
29
for the O ring
28
is defined by the step portion
23
of the rotor
18
and the resistor substrate
24
. A substantially C-character-shaped resistor
25
formed of e.g., a cermet resistor or a carbon resistor is formed in a method such as screen printing, transfer, or the like. The both ends of the resistor
25
are electrically connected to the center electrode
26
and the outer peripheral electrode
27
which are formed concentrically with the resistor
25
.
The O ring
28
is received in the reception groove
29
formed by the step portion
23
of the rotor
18
and the resistor substrate
24
, as described above. The outer peripheral surface of the O ring
28
is protruded to some degree from the outer peripheral surface of the large diameter portion
23
b
of the rotor
18
. Desirably, the O ring
28
is made of a silicone rubber or the like which is heat-resistant. When the rotor
18
is incorporated in the concavity
3
of the case
2
, the outer peripheral surface of the O ring
28
is contacted under pressure with the inner peripheral surface of the concavity
3
of the case
2
, while the inner peripheral surface of the O ring
28
is contacted under pressure with the short diameter portion
23
a
of the step portion
23
of the rotor
18
. Thus, the seal between the case
2
and the rotor
18
is secured.
The cover
30
is made of a metal material such as stainless steel or the like. A screwdriver insertion-hole
31
is formed in the center of the cover
30
, and through the hole
31
, the tool-engagement grooves
19
of the rotor
18
are exposed, as shown
FIGS. 1 and 2
. A part of the inner edge of the insertion hole
31
is bend downward to form a tongue stopper-receiver
32
(see FIG.
3
). The stopper-receiver
32
is engaged with the arched escaping groove
20
of the rotor
18
. The stopper
21
of the rotor
18
is brought into contact with the stopper-receiver
32
to control the rotation angle of the rotor
18
. A calibration
33
for indicating the rotational position of the rotor
18
is carved on the top surface of the cover
30
. In the four corners of the cover
30
, the fixing claws
34
are bent downward, respectively. The tips of the claws
34
are bent upward, respectively. Release-prevention protuberances
34
a
are provided on the opposite sides in the width directions of the claws
34
, respectively, as shown in FIG.
1
. Slits
34
b
are formed in the centers in the width directions of the claws
34
, respectively. The slits
34
b
cause the claws
34
to have an elasticity in the width directions, respectively. The protuberances
34
a
are engaged with the inner edges of the engaging holes
4
of the case
2
, respectively, whereby the cover
30
is prevented from being released from the case
2
. Engaging pieces
35
bend downward are formed protuberantly in the four side portions of the cover
30
, and are engaged with engaging recesses
8
formed in the outer periphery on the upper side of the case
2
. Thus, the engaging pieces
35
have a function of preventing the cover
30
from being transversely slipped.
Hereinafter, an assembly method for the variable resistor
1
of the above-described embodiment will be described.
First, the rotor
18
and the resistor substrate
24
are assembled. In particular, the O ring
28
is inserted onto the short diameter portion
23
a
of the step portion
23
of the rotor
18
. To the underside of the rotor
18
, the resistor substrate
24
is attached with the resistor
25
and the electrodes
26
and
27
facing downward. Thereby, the release of the O ring
28
is prevented. In this instance, the insertion work can be easily performed, since the O ring
28
is simply inserted onto the short diameter portion
23
a
of the rotor
18
. Further, for fixation of the resistor substrate
24
to the rotor
18
, the protuberances
22
a
and
22
b
provided for the rotor
18
are simply engaged with the hole
24
a
and the notch
24
b
of the resistor substrate
24
, respectively. Accordingly, even if they are small-sized parts with a size of about 1 to 2 mm, the workability is good.
Next, the rotor
18
having the resistor substrate
24
and the O ring
28
attached thereto is received into the concavity
3
of the case
2
, and the electrodes
26
and
27
are brought into contact with the contacts
9
b
,
10
b
, and
11
b
, respectively. Then, the rotor
18
is in the rising state, due to the rebounding forces of the arms
9
a
,
10
a
, and
11
a
of the sliders
9
,
10
, and
11
.
Thereafter, the case
2
is covered with the cover
30
from the upper side of the case
2
, and the rotor
18
is pushed into the concavity
3
. In this state, the fixing claws
34
of the cover
30
are inserted under pressure into the engaging holes
4
of the case
2
to be engaged with the holes
4
, respectively. At the moment, the O ring
28
can be smoothly inserted into the concavity
3
of the case
2
, since the outer peripheral surface of the O ring
28
is guided by the guide surface
3
a
on the upper edge of the concavity
3
of the case
2
. The cover
30
is attached as described above, so that the outer peripheral surface of the O ring
28
is contacted under pressure with the inner peripheral surface of the concavity
3
of the case
2
,.and the inner peripheral surface of the O ring
28
is contacted under pressure with the short diameter portion
23
a
of the step portion
23
of the rotor
18
, whereby the inside of the case
2
is tightly sealed.
In the variable resistor
1
assembled as described above, by rotating the rotor
18
with a screwdriver with the tip thereof being pressed to the tool-engagement grooves
19
of the rotor
18
, the contact
11
b
is slid on the resistor
25
, and the contact
10
b
is slid on the outer peripheral electrode
27
, with the contact
9
b
being kept in contact with the center electrode
26
. Accordingly, the resistance between the terminals
15
and
17
or that between the terminals
16
and
17
can be changed. Then, the rotor
18
is stopped at a optional position. The rotation of the rotor
18
is regulated, due to the frictional force of the O ring
28
and the positions at which the resistor
25
and the electrodes
26
,
27
are in contact with the contacts
9
b
,
10
b
, and
11
b
are prevented from changing. Thus, the resistances are stabilized.
FIGS. 9
,
10
, and
11
show a second embodiment of the present invention. In the second embodiment, the same reference numerals used in the first embodiment show similar or equivalent elements, and the description corresponding thereto is not repeated. In the second embodiment, sliders
40
are attached to a rotor
18
, and a resistor
43
and an electrode
44
are formed in the bottom of a case
2
, in contrast to the first embodiment.
A step portion
23
of which the lower portion has a short diameter is formed in the outer periphery on the underside of the rotor
18
. An O ring
28
is fitted onto the short diameter portion
23
a
of the step portion
23
of the rotor
18
. A single slider
40
is fixed to the underside of the rotor
18
, as shown in
FIGS. 10 and 11
. The slider
40
is provided with a substantially disk-shaped base sheet portion
40
a
. Into a caulking hole
40
b
formed in the base sheet portion
40
a
, the convexity
18
a
of the rotor
18
is inserted, and heat-caulked, so that the slider
40
is fixed to the underside of the rotor
18
. For the purpose of securing the fixation of the slider
40
to the rotor
18
, plural concavities
18
a
may be provided, or an additional portion for stopping the rotation of the slider
40
may be provided, for example. As a means for fixing the slider
40
to the underside of the rotor
18
, methods other than the heat caulking, such as pressure-fitting using a concavity and a convexity, adhesion, screwing, or the like may be employed.
The diameter of the base sheet portion
40
a
of the slider
40
is longer than the outer diameter of the underside (short diameter portion
23
a
) of the rotor
18
, and is shorter or equal to the long diameter portion
23
b
of the step portion
23
. Therefore, release of an O ring
28
is prevented by fixing the base sheet portion
40
a
of the slider
40
to the underside of the rotor
18
after the O ring
28
is fitted onto the short diameter portion
23
a
of the step portion
23
of the rotor
18
. In the slider
40
, plural comb-like arms
41
a
and
41
b
(in the figure, seven arms) extending downward from the base sheet portion
40
a
, having spring properties are formed by bending. Contacts
42
a
and
42
b
are formed in the tips of the arms
41
a
and
41
b
, respectively.
In the center of the bottom of the concavity
3
of the case
2
, an electrode
44
is formed, and a substantially C-character shaped resistor
43
is formed concentrically around the electrode
44
. Of the contacts
42
a
and
42
b
of the slider
40
, the plural contacts
42
a
near to the rotation center are contacted with the center electrode
44
, while the plural contacts
42
b
distant from the rotation center are sliding-contacted with the resistor
43
. Three terminals
45
,
46
, and
47
connected to both ends of the above-described resistor
43
and the center electrode
44
, lying in the bottom of the case
2
, are insert-molded. The resistances are output-through these terminals.
The rotor
18
having the slider
40
fixed thereto is received into the concavity
3
of the case
2
, and a cover
30
is pressed against there, whereby the O ring
28
is arranged between the short diameter portion
23
a
of the rotor
18
and the inner peripheral surface of the concavity
3
of the case
2
, in contact under pressure with them. Thus, the seal between the rotor
18
and the case
2
is secured.
In the above-described embodiment, the resistor
43
and the electrode
44
are disposed directly to the bottom of the concavity
3
of the case
2
. A resistor substrate having a resistor and an electrode formed on the surface thereof may be received and fixed in the concavity
3
of the case
2
with the surface facing upward.
FIG. 12
shows a third embodiment of the present invention, in which the first embodiment is partially changed. The same reference numerals used in the first and third embodiments show similar or equivalent elements, and the description corresponding thereto is not repeated.
In the third embodiment, the reception space
3
of a case
2
is opened upward and downward. Instead of the cover
30
mounted onto the upper side of the case
2
, a restraining wall
50
for restraining the rotor
18
from being released upward is formed on and integrally with the upper end of the case
2
. The inner periphery of the restraining wall
50
defines a screwdriver insertion hole
51
. A stopper-receiver
52
is formed on and integrally with the inner edge of the screwdriver insertion hole
52
. The rotor
18
having a resistor substrate
24
fixed thereto is inserted through the open portion in the bottom of the case
2
. A slider block
53
having sliders
9
,
10
, and
11
fixed thereto is fitted into the open portion in the bottom of the case
2
. The seal between the open portion in the bottom and the slider block
53
is performed with a resin
54
. In the inner wall of the open portion in the bottom of the case
2
, formed is a step portion
55
for positioning the slider block
53
.
In this instance, when the rotor
18
is received in the case
2
, and the slider block
53
is fitted into the open portion in the bottom of the case
2
, the slider block
53
is ready to rise, due to the rebounding force of the sliders
9
,
10
, and
11
. In the state that the slider block
53
is pressed against the-step portion
55
of the case
2
, the resin
54
is cast into the concave portion defined by the open portion in the bottom of the case
2
and the slider block
53
, and hardened, whereby the fixation and the sealing of the slider block
53
are simultaneously carried out.
Also in this embodiment, the release of the O ring
28
is prevented, due to the step portion
23
of the rotor
18
and the resistor substrate
24
. Accordingly, no release of the O ring
28
is caused when the rotor
18
is incorporated in the case
2
. Thus, the incorporation can be securely performed.
FIG. 13
shows a fourth embodiment of the present invention, in which the second embodiment is partially changed. Similar elements in the second and fourth embodiments are indicated with the same reference numerals, and the description corresponding thereto is not repeated.
Also in this embodiment, the reception space
3
of a case
2
is opened upward and downward. A restraining wall
50
for restraining the rotor
18
from being released upward is formed on and integrally with the upper end of the case
2
. The rotor
18
having a slider
40
fixed thereto is inserted through the open portion in the bottom of the case
2
. Into the open portion in the bottom of the case
2
, a resistor substrate
60
having a resistor
43
and an electrode
44
formed on the surface thereof is fitted. Seal between the open portion in the bottom and the resistor substrate
60
is performed with a resin
61
.
In this embodiment, in order to fix the slider
40
to the underside of the rotor
18
, three sectorial protuberances
62
are formed protuberantly on the underside of the rotor
18
. Into the grooves
63
between these protuberances
62
, the two sides elongating perpendicularly to each other of the base sheet portion
40
a
having a substantial T-character shape of the slider
40
are inserted under pressure to be fixed. Then, the O ring
28
can be securely prevented from being released, since the base sheet portion
40
a
having a substantial T-character shape of the slider
40
is protruded outward from the short diameter portion
23
a
of the step portion
23
of the rotor
18
toward the outer diameter side.
In this instance, it is necessary simply to insert the slider
40
into the rotor
18
under pressure. Accordingly, the attachment of the slider
40
to the rotor
18
can be performed more easily, as compared with the second embodiment (see FIGS.
10
and
11
). In the free state, the contacts
42
a
and
42
b
of the slider
40
are protuberant downward from the protuberances
62
. In the state that the rotor
18
and the resistor substrate
60
are incorporated into the case
2
, the protuberances
62
are in contact with the upper side of the resistor substrate
60
, so that the deflection of the contacts
42
a
and
42
b
are limited. Accordingly, advantageously, this prevents the contact pressures to increase unduly, which may be caused by variations in the incorporation.
The variable resistor of the present invention is not limited to the above-described embodiments, and may be variously changed without departing from the sprit and the scope of the present invention.
For example, in the above-described embodiments, the lead terminals
15
,
16
, and
17
are fixed to the sliders
9
,
10
, and
11
, the lead terminals
45
,
46
, and
47
are fixed to the bottom of the case
2
, and the lead terminals
45
,
46
, and
47
are fixed to the resistor substrate
60
. However, the variable resistor of the present invention may be a surface mounting type variable resistor, not limited to the variable resistor having the lead terminals.
As understood in the above description, according to the present invention, the incorporation of the O ring can be easily performed, and moreover, the O ring is prevented from being positionally slipped or released, even if a transportation vibration is applied during assemblage, by inserting the O ring onto the short diameter portion of the step portion of the rotor, and attaching the resistor substrate to the underside of the rotor. Thus, when the rotor is incorporated into the case, the incorrect engagement of the O ring is prevented, and the sealing can be securely performed.
According to the present invention, the O ring is prevented from being released by inserting the O ring onto the short diameter portion of the step portion of the rotor, and attaching the slider to the, underside of the rotor. Similarly, incorrect engagement of the O ring can be prevented. A variable resistor having good sealing properties can be provided.
According to the present invention, the O ring is prevented from being released by utilization of the resistor substrate or the slider which is an existing part. An especial part for preventing the O ring from being released is not required. The number of the parts is not increased. The height of the rotor can be decreased. That is, a variable resistor small in size and having a simple structure can be provided.
Claims
- 1. A variable resistor comprisinga case having a reception space, a slider fixed in the bottom of the reception space of the case, a rotor rotatably received in the reception space of the case, a resistor substrate having a resistor formed on the underside thereof and slidable in contact with the slider, and attached to the underside of the rotor, and an O ring performing the seal between the inner peripheral surface of the reception space of the case and the outer peripheral surface of the rotor, said rotor having a step portion formed in the outer peripheral surface on the underside thereof with the lower-side portion of the step portion having a short diameter, said O ring being fitted onto the short diameter portion of the step portion, the whole or a part of said resistor substrate being formed so as to have a diameter longer than that of the short diameter portion of the step portion of the rotor, and said resistor substrate being fixed to the underside of the rotor whereby the O ring is held between the step portion of the rotor and the resistor substrate.
- 2. A variable resistor according to claim 1, wherein the underside of the rotor is provided with a protuberance,the resistor substrate is provided with an engaging portion into which said protuberance is fitted under pressure, the protuberance of the rotor is fitted under pressure into the engaging portion of the resistor substrate, whereby the rotor and the resistor substrate are joined together integrally, rotatably.
- 3. A variable resistor according to claim 2, wherein the bottom of the case is provided with an open portion,the upper end of the case is provided with a restraining wall for restraining the rotor from being released upward, the rotor is inserted through the open portion in the bottom of the case, a slider block having the slider fixed thereto is fitted into the open portion in the bottom of the case, and said open portion in the bottom and said slider block is sealed and fixed with a resin.
- 4. A variable resistor according to claim 1, wherein the bottom of the case is provided with an open portion,the upper end of the case is provided with a restraining wall for restraining the rotor from being released upward, the rotor is inserted through the open portion in the bottom of the case, a slider block having the slider fixed thereto is fitted into the open portion in the bottom of the case, and said open portion in the bottom and said slider block is sealed and fixed with a resin.
- 5. A variable resistor according to claim 1, wherein the upper side of the case is provided with an opening to which a part of the rotor is exposed, andover the opening of the case, a cover for restraining the rotor from rising and holding the rotor rotatably is disposed.
- 6. A variable resistor comprisinga case having a reception space, a resistor substrate having a resistor formed on the upper side thereof and disposed in the bottom of the reception space of the case, a rotor rotatably received in the reception space of the case, a slider attached to the underside of the rotor and slidable in contact with the resistor, and an O ring performing the seal between the inner peripheral surface of the reception space of the case and the outer peripheral surface of the rotor, said rotor having a step portion formed in the outer peripheral surface on the underside thereof with the lower-side portion of the step portion having a short diameter, said O ring being fitted onto the short diameter portion of the step portion, the whole or a part,of said slider being provided with a base sheet portion having a diameter longer than that of the short diameter portion of the step portion of the rotor, the base sheet portion of the slider being fixed to the underside of the rotor, whereby the O ring is held between the step portion of the rotor and the base sheet portion of the slider.
- 7. A variable resistor according to claim 6, wherein the underside of the rotor is provided with a protuberance,the base sheet portion of the slider is provided with an engaging portion into which said protuberance is fitted under pressure, the protuberance of the rotor is fitted under pressure into the engaging portion of the base sheet portion, whereby the rotor and the base sheet portion of the slider are joined together integrally, rotatably.
- 8. A variable resistor according to claim 7, wherein the bottom of the case is provided with an open portion,the upper end of the case is provided with a restraining wall for restraining the rotor from being released upward, the rotor is inserted through the open portion in the bottom of the case, the resistor substrate is fitted into the open portion in the bottom of the case, and said open portion in the bottom and the resistor substrate are sealed and fixed with a resin.
- 9. A variable resistor according to claim 6, wherein the bottom of the case is provided with an open portion,the upper end of the case is provided with a restraining wall for restraining the rotor from being released upward, the rotor is inserted through the open portion in the bottom of the case, the resistor substrate is fitted into the open portion in the bottom of the case, and said open portion in the bottom and the resistor substrate are sealed and fixed with a resin.
- 10. A variable resistor according to claim 6, wherein the upper side of the case is provided with an opening to which a part of the rotor is exposed, andover the opening of the case, a cover for restraining the rotor from rising and holding the rotor rotatably is disposed.
Priority Claims (1)
Number |
Date |
Country |
Kind |
11-216091 |
Jul 1999 |
JP |
|
US Referenced Citations (10)
Foreign Referenced Citations (1)
Number |
Date |
Country |
10-149907 |
Jun 1998 |
JP |