Shape memory metal actuator and cable cutter

A shape memory alloy arrangement comprising:

• a mounting;
• at least three shape memory alloy members, each having undeformed states and first and second ends, arranged with their respective first ends proximate each other and with their respective second ends proximate each other, first and second ones of said members each being deformed from its undeformed state in one of compression and tension and a second one of said members intermediate said first and third ones of said members being deformed from its undeformed state in the other one of compression and tension;
• first means for affixing the first end of the first one of said members to said mounting, and the second end of the third one of said members being adapted for coupling to a utilization device;
• means for coupling the second one of said members at its second end to the second end of the first one of said members and at its first end to the first end of the third one of said members;
• and
• means for heating said members to a temperature sufficient for said members to return toward their respective undeformed states;
• whereby the shape changes associated with each of said members returning to its undeformed state tend to cumulate at the second end of said third member.

An apparatus for generating motion relative to a mounting in response to temperature, comprising:

• a plurality of prestressed elements defining first and second ends, each of said prestressed elements exhibiting the property of changing from a stressed dimension to a relaxed dimension between said first and second ends upon reaching a predetermined temperature, the first and second ends of each of said prestressed elements defining an axis therebetween, said plurality of elements including at least one first element which, in a direction parallel to a first axis of said first element, has a stressed dimension which is one of greater than and lesser than its relaxed dimension, and at least second and third elements, each of which, in directions parallel to second and third respective axes of said second and third elements, respectively, have stressed dimensions which are the other one of greater than and lesser than their relaxed dimensions;
• mechanical coupling means coupled to said first, second and third elements, for, with said first, second and third axes mutually parallel, rigidly connecting (a) said first end of said second element to said mounting, (b) said second end of said second element to said first end of said first element, and (c) said second end of said first element to said first end of said third element;
• and
• heating means thermally coupled to said first, second and third elements for causing them to reach said predetermined temperature at a time when said motion is desired, whereby said second end of said third element moves relative to said mounting.