Patent ID: 7302920

Claim:
An actuator, comprising: a housing having first and second fluid ports at different fluid pressures; an actuation cylinder in the housing defining a longitudinal axis and having first and second ends in first and second directions; an actuation piston in the cylinder with first and second surfaces moveable along the longitudinal axis; first and second actuation springs biasing the actuation piston in the first and second directions, respectively; a first fluid space defined by the first end of the actuation cylinder and the first surface of the actuation piston; a second fluid space defined by the second end of the actuation cylinder and the second surface of the actuation piston; a fluid bypass in fluid communication with only the first and second fluid spaces, the fluid bypass being operative to short-circuit the first and second fluid spaces when the actuation piston is not substantially proximate to either the first or second end of the actuation cylinder; a first flow mechanism in fluid communication between the first fluid space and the first port; and a second flow mechanism in fluid communication between the second fluid space and the second port.