Electricity: electrothermally or thermally actuated switches – Electrothermally actuated switches – With bimetallic elements
Reexamination Certificate
2001-08-24
2003-09-09
Vortman, Anatoly (Department: 2835)
Electricity: electrothermally or thermally actuated switches
Electrothermally actuated switches
With bimetallic elements
C337S066000, C337S075000, C337S089000
Reexamination Certificate
active
06617951
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a safety switch that has a bi-metal plate which has an end movably engaged with a gap defined in a switch member so that even if the switch member is stuck, the bi-metal plate is deformed when the switch is overridden.
BACKGROUND OF THE INVENTION
A conventional see-saw switch is shown in FIG.
1
and includes a switch member
11
having a protrusion
110
which movably presses a plate
12
so that two contacts on two ends of the plate
12
can be respectively pushed to contact a corresponding contact point. This type of switch cannot automatically jump off when it is overridden.
FIGS. 2A and 2B
show a switch disclosed in U.S. Pat. No. 5,262,748 that includes a switch member
13
which has one end connected to a connection plate
14
which is connected to a bi-metal plate
170
. A curve resilient plate
18
has one end connected to the easing
10
of the switch device and the other end connected to one end of the bi-metal plate
170
. Three terminal plates
15
,
16
,
17
are connected to the casing
10
of the switch device and the bi-metal plate
170
has the other end thereof connected to the terminal plate
17
. A contact point
171
is connected on the bi-metal plate
170
and another contact point
160
is connected to the terminal plate
16
. The bi-metal plate
170
is lowered by pushing the switch member
13
to close the circuit. When the switch is overridden, the bi-metal plate
170
is deformed to separate the two contact points
171
,
160
. However, if the switch member
13
is stuck or if the resilient plate
18
fails, the bi-metal plate
170
will not be deformed. Besides, if the deformation force of the bi-metal plate
170
is larger than the force of the resilient plate
18
, the resilient plate
18
will keep the bi-metal plate
170
at an open status. If the users push the switch member
13
again, the bi-metal plate
170
will jump off again, and this could result in sparks and has potential danger.
FIGS. 3A and 3B
show a Taiwanese published patent No. 334165 that includes a switch
20
with a driving member
21
which is slidably engaged with a connection member
22
. A spring
24
is connected between the driving member
21
and an inside of the casing of the switch device. A bi-metal plate
23
has one end thereof fixed to one of two terminal plates of the casing and the other end of the bi-metal plate
23
is engaged with the connection member
22
. The bi-metal plate
23
contacts the other terminal plate when the switch member
20
is pushed. When current overrides, the bi-metal plate
23
is deformed and pushes the driving member
21
to let a convex portion of the driving member
21
engage with a recess
25
defined in an inside of the casing, and the bi-metal plate
23
is separated from the terminal plate. When either one of the switch member
20
, the driving member
21
or the connection member
22
is out of order or stuck, the circuit cannot be opened. If the spring force
24
is too large, then the bi-metal plate
23
cannot jump off from the terminal plate, and if the spring force
24
is too small, then the bi-metal plate
23
could jump off often.
FIGS. 4A
,
4
B and
4
C show a switch device disclosed in U.S. Pat. No. 5,760,672 that includes a switch member
28
which has one end connected to a connection plate
26
which has a hook portion for receiving an end of a bi-metal plate
27
. Three terminal plates are connected to the casing of the switch device and a contact point
271
on the bi-metal plate
27
is to contact another contact point
272
on one of the terminal plates. A gap AS is defined in the hook portion so as to allow the bi-metal plate
27
to be deformed. However, this type of switch can only used with a specific type of see-saw switch member. Besides, because the switch member
28
, the connection member
26
and the bi-metal plate
27
are normally engaged with each other, if any one of the parts is stuck or out of order, the bi-metal plate
27
could not jump off when the temperature drops, the deformed bi-metal plate
27
will contact the contact point
272
again. Because the overridden situation is not released, the circuit will be opened and closed repeatedly.
SUMMARY OF THE INVENTION
In accordance with one aspect of the present invention, there is provided a safety switch which comprises a casing having a first terminal plate and a second terminal plate. A first contact point is connected to the first terminal plate and a bi-metal plate is fixedly connected to the second terminal plate. A second contact point is connected to the bi-metal plate. A movable member is movably engaged with the casing and has two protrusions extending from an inside of the movable member. A free end of the bi-metal plate is movably located between the two protrusions.
The primary object of the present invention is to provide a safety switch device wherein the bi-metal plate is deformed even if the switch member is stuck.
The present invention will become more obvious from the following description when taken in connection with the accompanying drawings which show, for purposes of illustration only, a preferred embodiment in accordance with the present invention.
REFERENCES:
patent: 2148880 (1939-02-01), Sattler
patent: 2911503 (1959-11-01), Garbers
patent: 4371859 (1983-02-01), Sorimachi
patent: 5262748 (1993-11-01), Tsung-Mou
patent: 5539371 (1996-07-01), Yu
patent: 5760672 (1998-06-01), Wang
patent: 5828284 (1998-10-01), Huang
patent: 5933069 (1999-08-01), Huang
patent: 6072381 (2000-06-01), Yu
patent: 6400250 (2002-06-01), Wang
patent: 6452125 (2002-09-01), Yu
patent: 496643 (1992-07-01), None
patent: 2063566 (1981-06-01), None
Tsung-Mou Yu
Vortman Anatoly
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