Patent ID: 7194991

Claim:
An actuator, comprising: a housing having first and second ports; an actuation cylinder in the housing defining a longitudinal axis and including first and second partial cylinders terminating in respective 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; 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 spring subsystem exerting force both in the first and second directions, the spring subsystem being configured to return the actuation piston to a neutral state; a second piston rod connected to the second surface of the actuation piston; a fluid bypass that short-circuits 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; a second flow mechanism in fluid communication between the second fluid space and the second port; at least one of the first and second flow control mechanisms being at least partially closed when the actuation piston does not overlap either of the first and second partial cylinders; and each of the first and second flow mechanisms being at least partially open when the actuation piston overlaps at least one of the first and second partial cylinders.