Patent ID: 7237380

Claim:
An actuator comprising: a housing having a part with a generally cylindrical interior that has a longitudinal axis, the housing including a first slot extending through the housing; a chamber within the housing and containing a working fluid that changes phase upon heating; an electrical heater disposed within the chamber for heating the working fluid upon application of electrical power to the electrical heater; a first piston slidably disposed within the housing and movable along the longitudinal axis between first and second positions within the housing, wherein the first piston is driven and slides from the first position to the second position in response to heating of the working fluid by the electrical heater, and the first piston includes a first guide pin extending transverse to the longitudinal axis and protruding into the first slot for guiding sliding movement of the first piston and coupling to an external mechanical device, wherein length of the actuator, measured along the longitudinal axis, is constant, independent of the position of the first piston; and a spring biasing the first piston toward the first position.