Abstract: A shape memory alloy actuator for rotating a pair of rotary members simultaneously and symmetrically like a butterfly moves its wings. The two rotary members are rotatably connected to each other at each one end portion thereof and biased in rotating directions opposite to each other by a biasing device. A wire-shaped shape memory alloy extending in a direction intersecting the rotary plane of the rotary members and fixed at opposite end portions thereof are associated at the intermediate portion thereof with a connected portion between the rotary members. When heated, the alloy shrinks attempting to return to the original length it remembers, and pushes the connected portion to rotate the rotary members against the biasing device. When cooled, the alloy, being stretched, allows the rotary members to be rotated back to their initial positions by the biasing device. A butterfly device involving the actuator is also disclosed.

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 circuit breaker includes first and second contactors having connecting/disconnecting means which normally keeps the two contactors in contact with each other. A shape memory alloy is mechanically connected to a predetermined portion of one of the connecting/disconnecting means of one contactor is electrically connected in parallel with a device to be protected, e.g. an electric circuit or an electric element. When a voltage of a predetermined value or more is applied to the device being protected, a current of a predetermined value or more passes through the shape memory alloy, whereby the alloy is heated to produce its shape memory effect. A shape recovering force is applied to the connecting/disconnecting means of the on contactor in a predetermined direction to separate the contactors.

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.