Patent ID: 7481055
Filing Date: 2009-01-27
Classification: F03G

Abstract:
1. An actuator comprising: a housing having a part with a generally cylindrical interior surface surrounding a longitudinal axis and including a plurality of helical grooves; 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 and rotatable about the longitudinal axis between first and second positions; a rolling diaphragm, separating the chamber from the first piston, driven by the working fluid, and sliding the first piston toward the second position upon expansion of the working fluid, wherein a piston rod extending from the piston body in a direction opposite the chamber and protruding from and moving relative to the housing; a plurality of balls, each ball being rotationally disposed in and captured between one of the helical grooves and one of the partially spherical recesses; a spring biasing the first piston toward the first; and a second piston interposed between the first piston and the rolling diaphragm, inhibiting transmission of torsion to the rolling diaphragm.