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US 5,510,598 AGranted
Electro-thermally actuated switch
AssigneeMartin Marietta Corporation
InventorsElias A. Kawam, Terri A. Cardellino
Life of this patent
Estimating the term…
Abstract
A thermally-actuated switch includes a pair of switch contacts openable or closeable in response to a change in the length of a shape memory metal (SMM) rod. The SMM rod is caused to change its length by having its temperature increased by heat produced when electrical power dissipated in a heating element that is coupled in electrical circuit with the switch contacts. To this end, the heating element is thermally coupled to the SMM rod, such as by a common heatsink. Where the switch is to be openable, the heating element is preferably in series circuit with the contacts, and where the contacts are closeable, the heating element is preferably in parallel therewith.
Claims17
A switch comprising:
- a pair of electrical contacts moveable between open circuit and closed circuit positions;
- a thermally conductive base having a cavity therein;
- a shape memory metal alloy member disposed in said cavity and thermally coupled to said base, said alloy member having first and second locations thereon between which a change in dimension occurs upon said alloy member reaching a predetermined temperature, said first location engaging said base within said cavity and said second location engaging said pair of electrical contacts;
- an electrical heating means for producing heat in response to the flow of electrical current therethrough, said heating means being closely thermally coupled to said base for heating said base and said alloy member to said predetermined temperature;
- and
- means for coupling said electrical heating means in electrical circuit with at least one of the contacts of said pair of electrical contacts for altering the flow of electrical current in said heating means responsive to said pair of contacts changing between their open and closed circuit positions.
3 more elements
Switch apparatus having first and second terminals comprising:
- a mounting base having a cavity adapted for receiving first and second contacts and a heat conducting member;
- first and second electrical contacts in said cavity, the first being moveable in relation to the second for changing between open circuit and closed circuit positions;
- a heat conducting member in said cavity and having a bore therein;
- an elongated shape memory metal alloy member located in said bore and thermally coupled to said heat conducting member, said elongated shape memory metal alloy member having first and second ends between which a change in length occurs upon said elongated shape memory metal alloy member reaching a predetermined temperature, said first end being within said bore and engaging said heat conducting member therein, and said second end extending from said bore for engaging said first electrical contact;
- an electrical heating means for producing heat in response to the flow of electrical current therethrough, said heating means being closely thermally coupled to said heat conducting member for heating said heat conducting member and said elongated shape memory metal alloy member to said predetermined temperature;
- means for coupling said electrical heating means in electrical circuit with at least one,of said first and second electrical contacts for altering the flow of electrical current in said heating means responsive to Said electrical contacts changing between their open and closed circuit positions;
- and
- means for coupling said first electrical contact to said first terminal and said second electrical contact to said second terminal.
5 more elements
Apparatus comprising:
- a battery having positive and negative terminals;
- at least one diode having anode and cathode connections;
- first and second electrical contacts moveable between open circuit and closed circuit positions;
- means for coupling said positive terminal to the cathode of said diode and to said first electrical contact;
- means for coupling said negative terminal to the anode of said diode and to said second electrical contact;
- a shape memory metal alloy member having first and second locations thereon between which a change in dimension occurs upon said alloy member reaching a predetermined temperature, said first location being constrained and said second location engaging one of said first and second electrical contacts;
- means for closely thermally coupling said diode to said shape memory metal alloy member for heating said alloy member to said predetermined temperature when electrical current flows through said diode, wherein the resulting change in dimension causes said first and second electrical contacts to change from the open circuit to the closed circuit position.
4 more elements
Dependencies are inferred from the claim text.