SMA actuator safety mechanism
First Claim
1. A safety mechanism for an actuator said actuator including at least one active shape memory alloy component selectively heated to deliver an actuating stroke,a passive shape memory alloy component exposed to ambient temperature conditions and activated by exceeding the phase transition temperature of said passive shape memory alloy component due to an ambient overtemperature condition;
- means operated by said passive shape memory alloy component for preventing said delivery of said actuating stroke.
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Accused Products
Abstract
A method and apparatus for preventing the unintended activation of SMA devices by ambient temperatures that exceed the phase transition temperature of the SMA material itself. In one embodiment a passive actuator is coupled to an active actuator, each having identical arrangements of SMA wire, but connected in opposite directions to compensate for temperature drift that is not due to powered heating. A second embodiment consists of a passive SMA wire connected to a latch/release mechanism allowing the actuator itself to move rather than moving the load. In a third embodiment the passive wire is connected to a load coupling, so that the load itself is disconnected from the actuator when the passive wire reaches the phase transition temperature. The passive wire may be made of a lower-temperature wire than the active wires, so that the release action occurs long before the active wire begins to be moved by ambient temperature.
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Citations
30 Claims
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1. A safety mechanism for an actuator said actuator including at least one active shape memory alloy component selectively heated to deliver an actuating stroke,
a passive shape memory alloy component exposed to ambient temperature conditions and activated by exceeding the phase transition temperature of said passive shape memory alloy component due to an ambient overtemperature condition; means operated by said passive shape memory alloy component for preventing said delivery of said actuating stroke. - View Dependent Claims (2, 3, 4)
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5. In a displacement multiplied actuator driven by selectively activated shape memory alloy components to deliver an output stroke, a safety mechanism for preventing spontaneous activation in an overtemperature condition, including:
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at least one passive shape memory alloy component exposed to ambient temperature conditions and activated by being passively heated to exceed the phase transition temperature of said at least one passive shape memory alloy component due to an ambient overtemperature condition;
means operated by contraction of said passive shape memory alloy component for preventing said delivery of said output stroke. - View Dependent Claims (6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30)
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Specification