Electricity: circuit makers and breakers – Electric switch details – Actuators
Reexamination Certificate
2002-08-21
2004-01-06
Friedhofer, Michael (Department: 2832)
Electricity: circuit makers and breakers
Electric switch details
Actuators
C200S520000, C200S524000, C337S036000, C337S056000, C337S066000
Reexamination Certificate
active
06674033
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to electric switches and, more particularly, to a press button type safety switch, which automatically trips off upon an overcurrent and, which enables the user to determine the on/off status from the outer appearance.
2. Description of the Related Art
A variety of electric switches, including seesaw switches and press button switches are known. In early days, a press button switch has only ON→OFF function, and cannot trip off automatically upon an overcurrent. In order to eliminate this problem, a variety of safety switches are developed. Regular safety switches are commonly of seesaw switching type.
FIGS. 1A and 1B
show a seesaw switch
1
invented by the present inventor. This design of seesaw switch
1
uses a plank
11
to move a conducting plate
12
between on/off positions. When an overcurrent occurred, the conducting plate
12
automatically trips.
FIGS. 2A and 2B
show a press button type safety switch according to Taiwan Patent No. 422404. This structure of press button type safety switch is comprised of a housing
21
, a press button
22
, and an actuating block
23
. The press button
22
is connected to the actuating block
23
. The actuating block
23
has a heart-like positioning groove
24
in the right sidewall. The right-sided terminal
25
has a top end connected with a bimetal
26
. The bimetal
26
has a top free end terminating in a retaining portion
261
adapted to engage the heart-like retaining groove
24
. When an overcurrent occurred, heat is transmitted from the right-sided terminal
25
to the bimetal
26
, thereby causing the bimetal
26
to deform and to disengage the retaining portion
261
from the heat-like positioning groove
24
, and at the same time the press button
22
is pushed upwards by the main spring
27
to the off position. This design is not practical in use. When the contacts
291
and
292
of the movable conducting block
29
contacted the contact
251
of the right-sided terminal
25
and the contact
281
of the intermediate terminal
28
, the load of current is at the terminals
25
and
28
and the movable conducting block
29
but not directly produced at the bimetal
26
. When heat produced upon an overcurrent, it is transferred from the movable conducting block
29
to the right-sided terminal
25
and then transferred from the right-sided terminal
25
to the bimetal
26
. Therefore, the bimetal
26
does not trip off immediately upon an overcurrent.
FIGS.
3
A~
3
E show an overload protective press button switch according to Taiwan patent publication no. 458362. This structure of overload protective press button switch comprises a housing
31
, the housing
31
having a top opening
311
and two open chambers
313
and
314
separated by a partition plate
312
, a metal contact unit
33
installed in the housing
31
, a switching mechanism
35
, a press button assembly
32
, and a linkage
34
. The linkage
34
comprises a spring member
342
supported on the partition plate
312
, a press member
341
mounted on the spring member
342
, and a swivel holder
344
pivoted to the housing
31
. The swivel holder
344
has a guide hole
343
, which receives the press member
341
, and a positioning portion
345
connected to the switching mechanism
35
.
When pressed the press button assembly
32
, the press member
341
is forced downwards to compress the spring member
342
and to bias the swivel holder
344
, thereby causing the switching mechanism
35
to switch on the metal contact unit
33
. When switched on, the spring member
342
pushes the press member
341
back to the initial position. The upper part I of this overload protective press button switch is similar to the design of the aforesaid prior art press button switch. The lower part II of this overload protective press button switch is similar to the design of the aforesaid prior art seesaw switch. This design is similar to Yu's Taiwan utility model no. 83365 (equivalent to U.S. Pat. No. 5,262,748) with the exception of the additional press button assembly
32
. The swivel holder
344
is equivalent to Yu's seesaw plank. This structure of overload protective press button switch is complicated, resulting in high manufacturing cost and inconvenience of use. When the push button assembly
32
pressed to the position shown in
FIG. 3C
, and the swivel holder
344
is biased leftwards, the metal contact unit
33
is switched on. When the user released the hand from the push button assembly
32
, the push button assembly
32
is moved to the position shown in FIG.
3
D. Viewing from the outside, it shows no difference between the position of
3
B and the opposition of
3
D, therefore the user cannot know “on” or “off” status of the switch when viewed from the outside. For on/off indication, a complicated indicator circuit must be installed.
SUMMARY OF THE INVENTION
The present invention has been accomplished under the circumstances in view. It is one object of the present invention to provide a press button type safety switch, which enables the user to know “on” or “off” status of the switch from the outer appearance of the switch. It is another object of the present invention to provide a press button type safety switch, which automatically trips off upon an overcurrent. It is still another object of the present invention to provide a press button type safety switch, which is simple and inexpensive to manufacture. To achieve these and other objects of the present invention, the press button type safety switch comprises a housing, the housing having a top opening, spring means mounted inside the housing, at least two terminals mounted in the housing for connecting to power source, a switching mechanism, a press button mounted in the top opening of the housing and supported on the spring means for pressing by hand; and an actuating structure controlled by the press button to switch the switching mechanism between on/off positions. The actuating structure comprises two sliding tracks respectively formed of a plurality of sliding rails and arranged in parallel, and a push member pivoted to the press button at a bottom side and forming with the press button a linkage. The push member comprises two bottom push portions respectively supported on the switching mechanism for synchronous movement with the push member to move the switching mechanism between on/off position, two guide rods extended from two opposite lateral sides thereof and respectively slidably coupled to the sliding tracks for guiding movement of the push member to switch the switching mechanism between on/off positions, and a stop device provided on the inside above the bottom push portions. The switching mechanism comprises a plank disposed in contact with the bottom push portions of the push member adapted for switching the terminals between on/off positions, an overcurrent protective conducting plate adapted to automatically trip off the circuit of the terminals upon an overcurrent, and a stop device upwardly extended from the plank and adapted to hook up with the stop device of the push member when the switching mechanism switched on. The plank is linked to the overcurrent protective conducting plate, and forcible by the overcurrent protective conducting plate to change the tilting angle and to disengage the stop device from the stop device of the push member for enabling the press button to be pushed upwards by the spring means when the overcurrent protective conducting plate tripped off upon an overcurrent.
REFERENCES:
patent: 3551867 (1970-12-01), Ingwersen
patent: 5532444 (1996-07-01), Bonrath et al.
patent: 6335500 (2002-01-01), Chi et al.
patent: 6417756 (2002-07-01), Yu
patent: 6483416 (2002-11-01), Yu
patent: 6504122 (2003-01-01), Yu
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