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Self-adjusting preload for memory alloy wire

  • US 10,029,829 B2
  • Filed: 03/05/2015
  • Issued: 07/24/2018
  • Est. Priority Date: 01/24/2011
  • Status: Active Grant
First Claim
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1. A preload mechanism for a memory alloy wire actuator, the preload mechanism comprising:

  • a rotating element configured to rotate about a pivot, the rotating element coupled with the memory alloy wire actuator at a first contact point that is displaced upon contraction of the memory alloy wire actuator such that the rotating element rotates from a first position to a second position; and

    a bias element having first and second ends, the first end coupled with the rotating element at a second contact point and the second end configured to be fixed relative to the pivot, wherein;

    the bias element has a line of action extending from the second end through the first end,the preload mechanism comprises an offset distance that is a minimum distance measured orthogonally from the pivot to the line of action, the offset distance having a first value when the rotating element is in the first position and a second value when the rotating element is the second position, andthe first contact point is a knife edge coupling the rotating element to the memory alloy wire actuator, the memory alloy wire actuator comprising a memory alloy wire wrapped around a capstan forming the knife edge, to receive an arm of the rotating element.

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