Abstract: A linear motion actuator which has a body; a member which is movable in a linear direction with respect to the body; an extended member made of shape memory alloy material, extended in a direction transverse to that linear direction so as to intersect it, supported at its ends by the body, and substantially coupled at its intermediate portion to the movable member at least with regard to mutual movement therebetween in that linear direction; and an element for biasing the movable member and the intermediate portion of the extended shape memory alloy member in that linear direction, so as to apply an elongation deformation to the extended shape memory alloy member. This linear motion actuator is inexpensive, compact, and light, and can be operated with a low voltage electrical supply, without being made bulky. Also, this linear motion actuator has an appropriate stroke to force relationship, and can be arranged to have a considerably large stroke.

Abstract: A method for actuating a member made of shape memory alloy, including stressing the shape memory alloy member so that its Ms point becomes positioned between its As point and its Af point, and applying a pulsed supply of electricity to it to heat it up is disclosed. The voltage and the duty factor d of the pulsed supply of electricity ensure that the relations .theta.ha greater than -.theta.ca and "d" less than or equal to .theta..sub.cc /(.theta.cc -.theta.hb ) are satisfied, where .theta..sub.ha is the heating speed of the shape memory alloy member in the region below its As point, .theta.hb is the heating speed of the shape memory alloy member in the region between its As point and its Af point, .theta..sub.cc is the cooling speed of the shape memory alloy member in the region above its Ms point, and .theta.ca is the cooling speed of the shape memory alloy member in the region below its Mf point.