Chemistry: electrical current producing apparatus – product – and – With measuring – testing – or indicating means
Reexamination Certificate
2000-03-29
2002-01-01
Dunn, Tom (Department: 1725)
Chemistry: electrical current producing apparatus, product, and
With measuring, testing, or indicating means
C429S093000, C429S007000, C337S003000, C337S333000
Reexamination Certificate
active
06335113
ABSTRACT:
This application is based on application No.11-90965 filed in Japan on Mar. 31, 1999, the content of which incorporated hereinto by reference.
BACKGROUND OF THE INVENTION
This invention relates to a thermostat that cuts off electrical current when the ambient temperature exceeds a set temperature and to a battery pack that contains the thermostat. In particular, this invention relates to a thermostat in which the thermostat return temperature when the ambient temperature drops after it has reached a high temperature and current has been cut off can be varied depending on the rising temperature and to a battery pack that contains the thermostat.
A thermostat which cuts off current when the ambient temperature exceeds a set temperature is housed, for example, in a battery pack, and cuts off current to protect the batteries when the temperature exceeds a set temperature. Further, the thermostat is housed not only in a battery pack but also an electric appliance containing a heater. The thermostat housed in an electric appliance cuts off current when the ambient temperature exceeds a set temperature and returns to the on state and turns on current when the ambient temperature drops.
The thermostat cuts off current when the ambient temperature exceeds a set temperature, and then it returns to the on state and turns on current when the temperature drops. When the ambient temperature becomes even higher than a set temperature due to an accident to a battery pack and an electric appliance, current should be maintained in a cut-off state for safety's sake. To realize this, a thermostat and a thermal fuse are combined to use. The blowout temperature of thermal fuse is set at a higher temperature than the thermostat cut-off temperature. When the ambient temperature becomes abnormally higher than a set temperature, the thermal fuse is blown out and current is maintained in the cutoff state.
This circuit is safe to use, but has the drawback that parts assembling requires much time and labor and the manufacturing cost is high because two parts of the thermostat and fuse are installed, and also it is difficult to miniaturize because the two parts are installed respectively.
To solve these problems, a thermostat that maintains current in the cut-off state after the ambient temperature has risen abnormally was developed (Japanese Non-examined Patent Publication HEI 8-7729). As shown in a cross-section view of
FIG. 1
, a thermostat described in this publication contains fuse springs
9
. The fuse springs
9
are fixed by thermal deformation materials
10
such as an alloy easily melted and synthetic resin. When the thermal deformation material
10
of synthetic resin fixing the fuse springs
9
is heated to a higher temperature than the thermostat cut-off temperature, it can not maintain the fuse springs
9
due to deformation. When the thermal deformation material
10
becomes in this state, the fuse springs
9
push a movable contact
3
, and the thermostat is maintained in the off state. The number of
4
shows a fixed contact in this figure.
The thermostat, shown in
FIG. 1
, maintains the movable contact
3
in the off state when the thermal deformation material
10
can not maintain the fuse springs
9
due to thermal deformation. Therefore, the thermostat can be so structured as not to return to the on state when the ambient temperature rises abnormally. However, a thermostat with this structure requires thermal deformation materials such as an alloy easily melted and synthetic resin which deform surely to disengage a fixed condition of the fuse springs when the ambient temperature exceeds a set temperature. For this reason, the manufacturing cost is increased. Further, it is necessary for the thermal deformation material to maintain the fuse springs firmly when the ambient temperature is lower than a set temperature. However, the thermal deformation material gets to deform easily due to repetition of being heated almost to a set temperature and has trouble with long-term reliability. Still further, the thermostat has the drawback that it is impossible to test repeatedly the thermal deformation material for the temperature when a fixed condition of the fuse springs is disengaged because the thermal deformation material can not return to its original shape once it has be en deformed by being heated. In addition to that, the thermostat has another drawback t hat the cost of parts is high and miniaturization is difficult since both of the fuse springs and thermal deformation material are housed therein.
The present invention was developed to solve these problems. It is thus a primary object of the present invention to provide a thermostat that can solve above-mentioned problems and a battery pack that contains the thermostat.
The above and further object of the invention will be more fully be apparent from the following detailed description with accompanying drawings,
SUMMARY OF THE INVENTION
The thermostat of the present invention comprises a first laminated metal plate and a second laminated metal plate in which a plurality of metal layers having different rates of expansion are laminated. The first laminated metal plate has a movable contact. The second laminated metal plate is disposed in such a position as to put the first laminated metal plate in the off and on positions. The first off temperature and the second off temperature, which put the movable contact in the off position by causing the first and second laminated metal plates to deform, and the first return temperature and the second return temperature, which return the movable contact from the off position to the on position, are set respectively at different temperatures.
The thermostat of the present invention comprises the first laminated metal plate
1
and the second laminated metal plate
2
having the following structures:
(a) The first laminated metal plate
1
having the movable contact
3
becomes in the on state by causing the movable contact
3
to come in contact with a fixed contact
4
and becomes in the off state by separating the movable contact
3
from the fixed contact
4
.
(b) When the ambient temperature exceeds the first off temperature, the first laminated metal plate
1
thermally deforms in the direction which the movable contact
3
is separated from the fixed contact
4
,
(c) When the temperature falls below the first return temperature, a thermal deformation force acts on the first laminated metal plate
1
in the direction which the movable contact
3
comes in contact with the fixed contact
4
.
(d) The second laminated metal plate
2
is disposed in such a position as to put the first laminated metal plate
1
to the off and on positions.
(e) When the temperature exceeds the second off temperature, the second laminated metal plate
2
thermally deforms in such a shape as to maintain the first laminated metal plate
1
in the off position.
(f) When the temperature falls below the second return temperature, the second laminated metal plate thermally deforms in such a shape as to return the first laminated metal plate
1
to the on position.
(g) The second off temperature is higher than the first off temperature and the second return temperature is lower than the first return temperature.
(h) When the temperature exceeds the first off temperature, the first laminated metal plate
1
becomes in the off position and when the temperature exceeds the second off temperature, the second laminated metal plate
2
maintains the first laminated metal plate
1
in the off state.
(i) When the thermostat is heated to the temperature between the first and second off temperatures, the first laminated metal plate
1
becomes in the off position. In this state, the first laminated metal plate
1
returns to the on position when the ambient temperature falls below the first return temperature.
(j) When the temperature exceeds the second off temperature, the second laminated metal plate
2
thermally deforms in such a shape as to maintain the first laminated metal plate
1
in the off position. In this state,
Nakatani Kensuke
Osaki Kazuo
Takasaki Yoshiharu
Takatsu Takao
Dunn Tom
Johnson Jonathan
Sanyo Electric Co,. Ltd.
Wenderoth , Lind & Ponack, L.L.P.
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