Shape memory alloy temperature sensor and switch
First Claim
1. ) A switch responsive to temperature history, comprising:
- a) a body, defining a path from an attachment portion thereof to an engagement portion thereof;
b) a sensing element, having a first portion mounted with the attachment portion such that motion of the first portion toward the engagement portion along the path is constrained, and having a second portion capable of first and second configurations, mounted with the engagement portion such that movement of the second portion toward the attachment portion along the path is prevented by such mounting when in the first configuration and not prevented when in the second configuration, and having a temperature responsive element made of a shape memory alloy mounted with the first and second portions such that changes in the temperature responsive element urge motion of the second portion toward the attachment portion along the path;
c) a switch, mounted with the body such that motion of the second portion toward the attachment portion along the path causes a change in the state of the switch.
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Accused Products
Abstract
A switch, such as an electromechanical or optical switch, whose state is responsive to temperature history, for example temperature excursions above or below a critical temperature. An element of the sensor made from shape memory alloy changes shape when exposed, even temporarily, to temperatures above the Austenitic start temperature As or below the Martensite start temperature Ms of the shape memory alloy sensor element. The shape change of the SMA element causes the sensor to change between two readily distinguishable states. The sensor can include a one-way stop element that creates a persistent indication of the temperature history. The switch also has built-in stops allowing the sensor to be manufactured and stored at temperatures above the Austenitic temperature without causing the indication of an over-temperature event, before the actual use.
32 Citations
20 Claims
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1. ) A switch responsive to temperature history, comprising:
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a) a body, defining a path from an attachment portion thereof to an engagement portion thereof;
b) a sensing element, having a first portion mounted with the attachment portion such that motion of the first portion toward the engagement portion along the path is constrained, and having a second portion capable of first and second configurations, mounted with the engagement portion such that movement of the second portion toward the attachment portion along the path is prevented by such mounting when in the first configuration and not prevented when in the second configuration, and having a temperature responsive element made of a shape memory alloy mounted with the first and second portions such that changes in the temperature responsive element urge motion of the second portion toward the attachment portion along the path;
c) a switch, mounted with the body such that motion of the second portion toward the attachment portion along the path causes a change in the state of the switch. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. ) A switch responsive to temperature history, comprising:
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a) a body, defining a path from an attachment portion thereof to an engagement portion thereof;
b) a sensing element having first and second portions, where the first portion mounts with the attachment portion such that motion of the first portion toward the engagement portion along the path is constrained, and having a temperature responsive element made of a shape memory alloy mounted with the first and second portions such that changes in the temperature responsive element urge motion of the second portion toward the attachment portion along the path;
c) a forcing element, having first and second portions, where the first forcing portion of the forcing element mounts with the second sensing element portion, and where the second forcing portion of the forcing element mounts with the engagement portion of the body;
d) a restraining element mounted with the body such that, when the second portion of the sensing element is in a first position the restraining element substantially prevents motion of the second portion toward the attachment portion;
e) wherein the forcing element is adapted to apply a force to the second sensing element portion having a component of force substantially along the path, wherein the component along the path is sufficient to stretch the temperature responsive element such that the second portion of the sensing element attains the first position when the temperature responsive element is in its Austenitic state but insufficient to stretch the temperature responsive element such that the second portion of the sensing element attains the first position when the temperature responsive element is in its Martensitic state;
f) a switch, mounted with the body such that motion of the second portion toward the attachment portion along the path causes a change in the state of the switch. - View Dependent Claims (13, 14, 15, 18, 19, 20)
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16. ) A switch responsive to a temperature event below a threshold temperature, comprising:
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a) A body;
b) An indicator element mounted with the body, rotatable relative to the body about an axis;
c) A forcing element mounted with the body and with the indicator element, disposed such that the forcing element urges rotation of the indicator element in a first direction;
d) A shape memory alloy element mounted with the body and with the indicator element, disposed such that the shape memory alloy element is in its contracted state when exposed to temperature above the threshold temperature, and when in its contracted state opposes the action of the forcing element with sufficient force to prevent rotation of the indicator element, and such that the shape memory alloy element is in its softened state when exposed to temperatures below the threshold temperature, and when in its softened state does not prevent rotation of the indicator element responsive to the forcing element;
e) Means for preventing the indicator element from rotating opposite the first direction once the indicator element has rotated a first amount in the first direction;
f) a switch mounted with the body such that rotation of the indicator element causes a change in the state of the switch. - View Dependent Claims (17)
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Specification