Patent ID: 7156058
Filing Date: 2007-01-02
Classification: F01L,Y10S

Abstract:
1. An actuator, comprising a housing having first and second ports, 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, 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, at least one first actuation spring biasing the actuation piston in the first direction, at least one second actuation spring biasing the actuation piston in the second direction, a spring controller movable at least longitudinally relative to the housing, the spring controller providing mechanical support for, and controlling the longitudinal position of, the first-direction end of the second actuation spring, at least one piston rod connected to one of the first and second surfaces 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, and a second flow mechanism in fluid communication between the second fluid space and the second port; wherein: at least one of the first and second flow mechanisms is at least partially closed when the actuation piston is not substantially proximate to either of the first and second ends of the actuation cylinder, and each of the first and second flow mechanisms being at least partially open when the actuation piston is substantially proximate to either of the first and second ends of the actuation cylinder.