Abstract: A device to provide overload protection for a shape memory metal (SMM) wire of an SMM-type actuator and to automatically compensate for cyclic creep and maintain the tension of the SMM wire. During normal operation, a restraining drum, in cooperation with a biasing spring, maintains the position of one end of the SMM wire so that the other end of the SMM wire can move an actuator. Under excessive loads, the restraining drum permits the first end of the SMM wire to move, thereby reducing the tension and preventing damage to the SMM actuator. When the excessive load is removed, the restraining drum permits the first end of the SMM wire to move under the influence of the biasing spring to its original position. By permitting the first end of the SMM wire to move in dependence upon the tension on the SMM wire, the device automatically takes up any slack caused by cyclic creep and maintains proper tension of the SMM wire.

Abstract: A shape memory metal (SMM) actuator includes an SMM actuator element mounted to an end fitting. An end portion of the actuator element adjacent the end fitting is cold formed to a thickness no more than 40% of the original thickness of the actuator element. This cold formed region extends by about 5 times the diameter of the actuator element away from the end fitting. The cold formed end region remains in the austenitic state, and is therefore relatively hard and strong. For this reason, the tendency of the actuator element to break at the end fitting is reduced, even though the end fitting acts as a temperature sink and maintains the cold formed end region below the transition temperature of the SMM actuator element.

Abstract: A shape memory metal actuator includes an actuator element that is secured at one end to an end fitting which is in turn secured to an overload protection spring. An adjustable screw is mounted to a frame and is positioned such that the overload protection spring biases the end fitting into contact with the adjustment screw. The end fitting lifts off of the adjustment screw when excessive stretching forces are applied to the actuator element. The adjustment screw can be moved to vary the rest position of the end fitting, thereby allowing manual compensation for cyclic creep of the actuator element.

Abstract: A lamp such as a fog lamp for a vehicle is provided with a housing which serves to mount an array of parallel louvers. The louvers are controlled by a heat driven actuator. Such as one which incorporates a shape memory metal actuator element. This actuator element is heated either by resistive heating or by direct heat of the light bulb when the lamp is activated. When heated, the actuator serves to pivot the louvers into an open position. Once the lamp is deactivated, heating of the actuator is terminated, and the louvers are automatically closed to protect the lens by a spring as the actuator cools.