Shape memory metal actuated separation device

Abstract

A shape memory alloy (SMA) actuator predeformed in tension actuates a separation device mechanism. A segmented nut, which engages a threaded bolt to be held and released, is held together by a nut retainer that is movable with respect to the nut and is affixed to the SMA element. The SMA element is heated by an electrical resistance heater to cause it to return to its undeformed state, thereby moving the retainer relative to the nut segments. When the retainer disengages from the segments, the segments are free to move outwardly thereby releasing the bolt or other item. Ones of the shape memory alloy actuator have a plurality of parallelly arranged SMA elements, every other one of which is predeformed in compression and intermediate ones of which are predeformed in tension. The elements are coupled end-to-end so that, when they are heated to cause them to return to their undeformed states, their respective elongations and shrinkages combine at the output to produce an actuation that is the cumulation in the same direction of the changes of all the elements. The plurality of elements may be in a side-by-side or concentric arrangement. Embodiments of the separation nut also include a plunger arrangement for urging the nut segments to move apart when released by the nut retainer and an ejector for pushing the released bolt or other item out of the separation device housing.

Dependencies are inferred from the claim text.