Information
-
Patent Grant
-
6577221
-
Patent Number
6,577,221
-
Date Filed
Friday, November 30, 200122 years ago
-
Date Issued
Tuesday, June 10, 200320 years ago
-
Inventors
-
-
Examiners
Agents
-
CPC
-
US Classifications
Field of Search
US
- 337 1
- 337 31
- 337 36
- 337 37
- 337 52
- 337 53
- 337 59
- 337 62
- 337 66
- 337 68
- 337 72
- 337 75
- 337 85
- 337 89
- 337 101
- 337 111
- 337 112
- 337 113
- 337 140
- 200 401
- 200 402
- 200 451
- 200 237
- 200 3181
- 200 3182
- 029 622
-
International Classifications
- H01H7116
- H01H7158
- H01H3702
-
Abstract
A safety switch is constructed to include two metal contact plates, a bimetal contact plate suspended from one metal contact plate, a switching handle, a push and pull bar pivoted to the switching handle and driven by the switching handle to move the bimetal contact plate between the “On” position and the “Off” position, and a S-shaped metal spring plate adapted for supporting and guiding movement of the push and pull bar for enabling the bimetal contact plate to trip off automatically upon an overload despite of the positioning of the push and pull bar or the switching handle.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a safety switch and, more particularly, to such a safety switch, which uses a S-shaped metal spring plate to guide and support a push and pull bar, enabling the On/Off control bimetal contact plate to automatically trip off upon an overload.
2. Description of the Related Art
FIG. 7
shows a conventional seesaw switch, which comprises a switching handle
11
(which has a lamp bulb installed therein), and a press rod
110
supported on a spring in a bottom hole of the switching handle
11
and moved with the switching handle
11
to move a movable metal contact plate
12
between the “On” position and the “Off” position. This structure of seesaw switch is a passive switch that cannot automatically trip off upon an overload. When an overload occurred, the circuit tends to be burned out. In order to eliminate this problem, switches with protective circuit means, i.e., safety switches are developed.
FIGS. 8A and 8B
show a safety switch according to the prior art. This structure of safety switch comprises a housing
10
, a switching handle
13
pivoted to the housing
10
, three metal contact plates, namely, the first metal contact plate
15
, the second metal contact plate
16
, and the third metal contact plate
17
respectively installed in the bottom side of the housing
10
, a bimetal contact plate
170
, the bimetal contact plate
170
having a fixed end fixedly fastened to the third metal contact plate
17
and a free end provided with a contact
171
adapted for contacting a contact
160
at the second metal contact plate
16
to close the circuit, a link
14
coupled between one end of the switching handle
13
and the free end of the bimetal contact plate
170
and driven by the switching handle
13
, to move the contact
171
of the bimetal contact plate
170
toward or away from the contact
160
of the second metal contact plate
16
, and a curved spring plate
18
fixedly connected between one peripheral sidewall of the housing
10
and the free end of the bimetal contact plate
170
and adapted for controlling the moving distance of the free end of the bimetal contact plate
170
. When the temperature of the bimetal contact plate
170
surpasses a predetermined high value due to an overload, it is caused to deform and to trip off from the contact
160
of the second metal contact plate
16
. This structure of safety switch is still not satisfactory in function because of the following drawbacks:
1. When the switching handle
13
jammed or stopped by an external pressure, or the curved spring plate
18
was worn-out, the bimetal contact plate
170
cannot trip off upon an overload.
2. The bimetal contact plate
170
automatically trips off when the temperature surpassed a trip-off temperature (normally 100°˜150° C.). When turning the switching handle
13
to the “On” position at this time, the bimetal contact plate
170
will automatically trip off if the power of deformation of the bimetal contact plate
170
surpasses the spring power of the curved spring plate
18
. If the user holds the switching handle
13
in the “On” position with force to keep the contact
171
of the bimetal contact plate
170
in contact with the contact
160
of the second metal contact plate
16
at this time, the circuit may be caused to burn out.
3. Because the bimetal contact plate
170
is a planar structure for one-way trip-off functioning only, the curved spring plate
18
must be used to achieve bi-directional trip-off functioning. However, it is difficult to control the spring power of the curved spring plate
18
during its fabrication. If the spring power of the curved spring plate
18
does not match, the bimetal contact plate
170
will be unable to function normally.
FIGS. 9A and 9B
show a safety switch with overcurrent protection. This structure of safety switch comprises a switching handle
20
, an electrically insulative driving element
21
and a link
22
coaxially pivoted to one end of the switching handle
20
, a spring member
24
connected between a fixed point and the other end of the driving element
21
, and a bimetal contact plate
23
. The bimetal contact plate
23
has a fixed end fixedly fastened to a first metal contact plate connected to one terminal of power supply, and a free end connected to the other end of the link
22
and moved with the link
22
relative to a contact at a second metal contact plate connected to the other terminal of power supply. When an overcurrent occurred, the bimetal contact plate
23
is heated to deform and to trip off from the contact of the second metal contact plate, and at the same time the driving element
21
is moved upwards with the free end of the bimetal contact plate
23
and forced into engagement with a curved positioning portion
25
in the housing of the safety switch to hold the bimetal contact plate
23
in the “Off” position. This structure of safety switch still has drawbacks. If the switching handle
20
, the driving element
21
, or the link
21
fails to function normally, the bimetal contact plate
23
will be unable to trip off upon an overload. Further, the spring power of the spring member
24
must be accurately controlled during its fabrication. If the spring power of the spring member
24
does not match, the driving element
21
will be unable to function properly.
Therefore, it is desirable to provide a safety switch that eliminates the aforesaid drawbacks.
SUMMARY OF THE INVENTION
The present invention has been accomplished to provide a safety switch, which eliminates the aforesaid drawbacks. It is one object of the present invention to provide a safety switch, which automatically trips off upon an overload. It is another object of the present invention to provide a safety switch, which has a simple structure, and achieves the auto trip-off functioning of a conventional complicated fuseless mechanical switch. It is still another object of the present invention to provide a safety switch, which can be smoothly accurately switched between the “On” position and the “Off” position. To achieve these and other objects of the present invention, the safety switch comprises a housing holding two metal contact plates, which are respectively connected to the two opposite terminals of power supply, a bimetal contact plate suspended from one metal contact plate, a switching handle pivoted to the housing and adapted for moving the bimetal contact plate between the “On” position to close the circuit between the two metal contact plates and the “Off” position to open the circuit between the two metal contact plates, a push and pull bar pivoted to one end of the switching handle and driven by the switching handle to move the bimetal contact plate between the “On” position and the “Off” position, and a S-shaped metal spring plate adapted for supporting and guiding movement of the push and pull bar for enabling the bimetal contact plate to trip off automatically upon an overload despite of the positioning of the push and pull bar or the switching handle.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1
is an exploded view of a part of a safety switch constructed according to a first embodiment of the present invention.
FIG. 2
is a sectional view of the safety switch according to the first embodiment of the present invention when switched on.
FIG. 3
is a sectional view of the safety switch according to the first embodiment of the present invention when switched off.
FIG.
4
(
a
) is sectional view in an enlarged scale of a part of the safety switch according to the first embodiment of the present invention showing the relative action between the push and pull bar and the bimetal contact plate (I).
FIG.
4
(
b
) is sectional view in an enlarged scale of a part of the safety switch according to the first embodiment of the present invention showing the relative action between the push and pull bar and the bimetal contact plate (II).
FIG.
4
(
c
) is sectional view in an enlarged scale of a part of the safety switch according to the first embodiment of the present invention showing the relative action between the push and pull bar and the bimetal contact plate (III).
FIG.
5
(
a
) is sectional view in an enlarged scale of a part of the safety switch according to the second embodiment of the present invention showing the relative action between the push and pull bar and the bimetal contact plate (I).
FIG.
5
(
b
) is sectional view in an enlarged scale of a part of the safety switch according to the second embodiment of the present invention showing the relative action between the push and pull bar and the bimetal contact plate (II).
FIG.
5
(
c
) is sectional view in an enlarged scale of a part of the safety switch according to the second embodiment of the present invention showing the relative action between the push and pull bar and the bimetal contact plate (III).
FIG. 6
is a sectional assembly view of the safety switch according to the second embodiment of the present invention, showing the bimetal contact plate tripped off, the switching handle turned to the horizontal position.
FIG. 7
is a sectional view of a seesaw switch constructed according to the prior art.
FIG. 8A
is a sectional view of a safety switch constructed according to the prior art when switched off.
FIG. 8B
is similar to
FIG. 8A
but showing the safety switch switched off.
FIG. 9A
is a sectional view of another structure of safety switch constructed according to the prior art when switched off.
FIG. 9B
is similar to
FIG. 9A
but showing the safety switch switched on.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to
FIGS. 1
,
2
, and
4
(
c
), a safety switch is shown comprising:
a housing
3
;
a switching handle
31
suspended in the top open side of the housing
3
and adapted for switching on/off the safety switch, the switching handle
31
having two pivots
32
respectively raised from two opposite peripheral sidewalls thereof on the middle and respectively pivoted to the two opposite peripheral sidewalls of the housing
3
, and a bottom lug
311
disposed near one end thereof;
a first metal contact plate
4
and a second metal contact plate
5
mounted in the housing
1
and respectively connected to the two opposite terminals of power supply, the first metal contact plate
4
having a horizontal top section
41
and a raised contact
42
at the top side of the horizontal top section
41
, the second metal contact plate
5
having a horizontal top lug
51
;
a bimetal contact plate
7
fastened to the horizontal top lug
51
of the second metal contact plate
5
, the bimetal contact plate
7
having a contact
71
on the middle and a tip
72
protruded from the free end thereof;
a third metal contact plate
6
installed in the housing
3
and extended out of a bottom hole (not shown) of the housing
3
for grounding; and
a push and pull bar
8
coupled between the switching handle
31
and the bimetal contact plate
7
, the push and pull bar
8
comprises a horizontal top pin
81
pivoted to the bottom lug
311
of the switching handle
31
, a horizontal bottom rail
86
, a vertical actuating face
83
connected between one end of the horizontal top pin
81
and one end of the horizontal bottom rail
86
, a side opening
82
defined between the horizontal top pin
81
and the horizontal bottom rail
86
, a retaining gap
84
spaced between the side opening
82
and the horizontal bottom rail
86
, and a protruded pushing rod
85
suspended above the retaining gap
84
below the side opening
82
.
The main features of the present invention are outlined hereinafter. A substantially S-shaped metal spring plate
9
is mounted in one peripheral sidewall of the housing
3
within the path of the push and pull bar
8
. The metal spring plate
9
comprises a top positioning flange
95
and a bottom positioning flange
96
respectively extended from the top and bottom ends thereof and fastened to respective positioning portions
34
and
35
of the housing
3
, a first bearing portion
91
disposed near the top positioning flange
95
corresponding to the upper limit position (“On” position) of the push and pull bar
8
, a side opening
92
defined below the horizontal bearing portion
91
, a smoothly arched middle portion
93
, and a second bearing portion
94
spaced between the smoothly arched middle portion
93
and the bottom positioning portion
96
corresponding to the lower limit position (“Off” position) of the push and pull bar
8
. The side opening
92
of the S-shaped metal spring plate
9
extends in direction reversed to the side opening
82
of the push and pull bar
8
. During installation, the push and pull bar
8
is inserted through the side opening
92
of the S-shaped metal spring plate
9
, and moved up and down in the side opening
92
of the S-shaped metal spring plate
9
between the upper limit (“On”) position and the lower limit (“Off”) position.
When the bimetal contact plate
7
is maintained in the electrically connected “On”) position as shown in FIGS.
2
and
4
(
a
), the front (free) end of the bimetal contact plate
7
curves upwards, the first bearing portion
91
of the S-shaped metal spring plate
9
imparts a pressure to the push and pull bar
8
, thereby causing the push and pull bar
8
to be tilted in one direction and supported on the second bearing portion
94
of the S-shaped metal spring plate
9
, at this time the tip
72
of the bimetal contact plate
7
is disengaged from the retaining gap
84
but maintained stopped below the protruded pushing rod
85
of the push and pull bar
8
, i.e., the contact
71
of the bimetal contact plate
7
is maintained in close contact with the contact
42
of the first metal contact plate
4
, and the safety switch is maintained in the close circuit (“On”) status. If the temperature of the bimetal contact plate
7
surpassed the predetermined critical level due to an overload during working of the safety switch, the bimetal contact plate
7
is caused to break down and to move from the position A to the position C, thereby causing the safety switch to be switched off.
Referring to FIG.
4
(
b
), when pressing the switching handle
31
from the “On” position to the “Off” position, the protruded pushing rod
85
is lowered with the push and pull bar
8
to force the tip
72
of the bimetal contact plate
7
downwards. When the tip
72
of the bimetal contact plate
7
lowered below the mid point (trip-off) position B between the “On” position A and the “Off” position C, the bimetal contact plate
7
is deformed and tripped to position C to off the circuit.
After trip off of the bimetal contact plate
7
due to breakdown, the switching handle
31
is turned with the hand in the reversed direction to switch on the safety switch. At this time, the push and pull bar
8
is forced downwards and moved along the smoothly arched middle portion
93
of the S-shaped metal spring plate
9
to the second bearing portion
94
as shown in FIGS.
3
and
4
(
a
), and the tip
72
of the bimetal contact plate
7
is forced into the retaining gap
84
of the pus and pull bar
8
, and therefore the bimetal contact plate
7
is linked to the push and pull bar
8
. Therefore, when the push and pull bar
8
lifted, the horizontal bottom rail
86
imparts a pressure to the tip
72
of the bimetal contact plate
7
, causing the bimetal contact plate
7
to deform and to force the contact
71
into close contact with the contact
42
of the first metal contact plate
4
, and therefore the safety switch is switched on. When the push and pull bar
8
moved upwards, the first bearing portion
91
of the S-shaped metal spring plate
9
touches the actuating face
83
of the push and pull bar
8
as shown in FIG.
4
(
a
), thereby causing the push and pull bar
8
to be tilted in one direction, and the tip
72
of the bimetal contact plate
7
is disengaged from the retaining gap
84
of the pus and pull bar
8
and stopped below the protruded pushing rod
85
so that the bimetal contact plate
7
can quickly trip off upon an overload.
As indicated above, the push and pull bar
8
is moved along the inner surface of the S-shaped metal spring plate
9
between the “On” position and the “Off” position smoothly, enabling the switching handle
31
to be smoothly operated to switch on/off the safety switch accurately.
FIGS.
5
(
a
) shows an alternate form of the present invention. According to this alternate form, the push and pull bar
8
comprises a L-shaped extension flange
861
extended from the bottom side of the horizontal bottom rail
86
and suspended in position B′ below the mid point (trip-off) position B. The distance D between the protruded pushing rod
85
and the L-shaped extension flange
861
is sufficient for enabling the bimetal contact plate
7
to trip off. In case the push and pull bar
8
is jammed or damaged and unable to be moved, the bimetal contact plate
7
can still trip off to switch off the circuit.
Referring to FIG.
5
(
b
), when the bimetal contact plate
7
broken down and tripped off during normal functioning of the push and pull bar
8
and the switching handle
31
, the tip
72
of the bimetal plate
7
will carry the L-shaped extension flange
861
to the “Off” position C.
Referring to
FIG. 6
, when the bimetal contact plate
7
tripped off and moved to the “Off” position C due to an overload, the push and pull bar
8
is moved with the bimetal contact plate
7
to the “Off” position C, and at this time the switching handle
31
is turned from the rightwards tilted position to the horizontal position. By means of the indication of the horizontal position of the switching handle
31
, the user knows that the safety switch is not in the “On” position. If the user wishes to switch on the safety switch, press the switching handle
31
leftwards to lower the push and pull bar
8
from the “Off” position C to the position E. At this time, the second push portion
94
of the S-shaped metal spring plate
9
forces the horizontal bottom rail
86
of the push and pull bar
8
inwards, thereby causing the tip
72
of the bimetal contact plate
7
to be engaged into the retaining gap
84
of the pus and pull bar
8
, and therefore the bimetal contact plate
7
is linked to the push and pull bar
8
. When pressing the switching handle
31
rightwards, the push and pull bar
8
is lifted, and the bimetal contact plate
7
is curved again and moved from the “Off” position C to the “On” position A to switch on the circuit.
A prototype of safety switch has been constructed with the features of FIGS.
1
˜
6
. The safety switch functions smoothly to provide all of the features discussed earlier.
Although particular embodiments of the invention have been described in detail for purposes of illustration, various modifications and enhancements may be made without departing from the spirit and scope of the invention. Accordingly, the invention is not to be limited except as by the appended claims.
Claims
- 1. A safety switch comprising:a housing; a switching handle pivoted to said housing and adapted for switching on/off the safety switch, said switching handle having two pivots respectively raised from two opposite peripheral sidewalls thereof on the middle and respectively pivoted to two opposite peripheral sidewalls of said housing, and a bottom lug disposed near one end thereof; a first metal contact plate and a second metal contact plate mounted in said housing and respectively connected to two opposite terminals of power supply, said first metal contact plate having a horizontal top section and a raised contact at said horizontal top section, said second metal contact plate having a horizontal top lug; a bimetal contact plate, said bimetal contact plate having a fixed end fixedly fastened to the horizontal top lug of said second metal contact plate, a contact adapted for contacting the contact of said first metal contact plate, and a free end terminating in a tip; a push and pull bar coupled to said switching handle and moved with said switching handle between an upper limit (“On”) position and a lower limit (“Off”) position, said push and pull bar comprising a horizontal top pin pivoted to the bottom lug of said switching handle, and a horizontal bottom rail adapted for pulling the tip of said bimetal contact plate to force said bimetal contact plate to trip off, a vertical actuating face connected between one end of said horizontal top pin and one end of said horizontal bottom rail, a side opening defined between said horizontal top pin and said horizontal bottom rail, a retaining gap spaced between said side opening and said horizontal bottom rail and adapted for receiving the tip of said bimetal contact plate, and a protruded pushing rod suspended above said retaining gap below said side opening and adapted for pushing the top of said bimetal contact plate; wherein a substantially S-shaped metal spring plate is mounted in one peripheral sidewall of said housing within the path of said push and pull bar between said upper limit (“On”) position and said lower limit (“Off”) position to guide movement of said push and pull bar, said S-shaped metal spring plate comprising a first bearing portion disposed near a top end thereof corresponding to said upper limit position (“On” position), a side opening defined below said horizontal bearing portion and adapted for receiving said push and pull bar, a smoothly arched middle portion, and a second bearing portion disposed near a bottom end thereof corresponding to said lower limit position (“Off” position) and adapted for supporting said push and pull bar.
- 2. The safety switch as claimed in claim 1, wherein the side opening of said S-shaped metal spring plate extends in direction reversed to the side opening of said push and pull bar.
- 3. The safety switch as claimed in claim 1, wherein said S-shaped metal spring plate further comprises a top positioning flange and a bottom positioning flange respectively extended from the top and bottom ends thereof and fastened to respective positioning portions of said housing.
- 4. The safety switch as claimed in claim 1 wherein said push and pull bar further comprises a L-shaped extension flange extended from a bottom side of said horizontal bottom rail and suspended in position below the mid point between said upper limit position (“On” position) and said lower limit position (“Off” position).
US Referenced Citations (17)
Foreign Referenced Citations (3)
Number |
Date |
Country |
647094 |
Dec 1984 |
CH |
2001006513 |
Jan 2001 |
JP |
2001006514 |
Jan 2001 |
JP |