Thermal switch
First Claim
1. A thermal switch comprising a base, a fixed contact means and a movable contact means mounted on said base, a bimetallic element disposed on said base and operable upon being heated to deflect and to cause said movable contact means to be out of contact with said fixed contact means and to thereby dispose the switch in an open state, said switch having a closed state in which said movable contact means is biased into contact with said fixed contact means and current flows along a current path which includes said movable contact means and said fixed contact means, said base being connected electrically in parallel with said current path, said base being made of an electrically conductive plastic material having a resistance such that said base does not generate heat when the switch is in said closed state, said base being operable to generate heat when said switch is in said open state to maintain said bimetallic strip in said deflected state.
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Accused Products
Abstract
This invention provides a small-size thermal switch having a base formed of an electrically conductive plastic. The thermal switch is arranged such that, after a bimetallic element deflects in a reverse direction and opens the circuit of the thermal switch, the bimetallic element is self-held in such a reversely deflected state and the self-held state of the bimetallic element is maintained until an electrical power source is switched off. This invention further provides a thermal switch in which one surface of its movable-contact leaf spring is maintained in contact with the surface of its bimetallic element which is formed of a metal having the lower coefficient of expansion. Since the bimetallic element is sandwiched between the base and the movable contact, the stability of the bimetallic element in a recess of the base is improved.
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Citations
16 Claims
- 1. A thermal switch comprising a base, a fixed contact means and a movable contact means mounted on said base, a bimetallic element disposed on said base and operable upon being heated to deflect and to cause said movable contact means to be out of contact with said fixed contact means and to thereby dispose the switch in an open state, said switch having a closed state in which said movable contact means is biased into contact with said fixed contact means and current flows along a current path which includes said movable contact means and said fixed contact means, said base being connected electrically in parallel with said current path, said base being made of an electrically conductive plastic material having a resistance such that said base does not generate heat when the switch is in said closed state, said base being operable to generate heat when said switch is in said open state to maintain said bimetallic strip in said deflected state.
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16. A thermal switch comprising a base, a fixed contact means having a fixed contact element and a first terminal mounted on said base, a movable contact means being a movable contact element, a leaf spring, and a second terminal mounted on said base, a bimetallic element disposed on said base and operable upon being heated to deflect and to cause said movable contact means to be out of contact with said fixed contact means and thereby dispose the switch in an open state, said switch having a closed state in which said movable contact means is biased by said leaf spring into contact with said fixed contact means and current flows along a current path which includes said second terminal, said leaf spring, said movable contact element, said fixed contact element and said first terminal, said base being connected electrically in parallel with said current path, said base being made of an electrically conductive plastic material having a resistance such that said base does not generate heat when the switch is in said closed state, said base being operable to generate heat when said switch is in said open state to maintain said bimetallic strip in said deflected state.
Specification