Abstract: An actuator which includes a memory metal element, a substantially constant force counteracting spring, and an actuated element. The memory metal transforms from a martensite structure to an austenite structure at a known temperature. The martensite structure is more easily deformed than the austenite structure. The force applied by the counteracting spring is sufficient to deform the martensite structure throughout the transformation temperature range but insufficient to deform the austenite structure such that at least a portion of the memory metal element undergoes a predetermined stroke in response to the transformation of the memory metal element between the martensite and austenite states. The actuated element is connected to the memory metal element to move therewith.