Patent ID: 7305914

Claim:
A hydraulic actuator device, comprising: a piston within a cylinder, the cylinder having a first fluid port in fluid communication with an open side of the piston, and a second fluid port in fluid communication with a shaft side of the piston, the piston configured to travel in a first direction, toward the shaft side of the piston and in a second direction, toward the open side of the piston; a valve circuit having a valve configured to selectively couple the first fluid port with a high-pressure fluid source while in a first position, and with a low-pressure fluid source while in a second position, the valve further configured to couple the second fluid port to the high-pressure fluid source while in the first or second positions, and the valve also configured to close the second fluid port while in a third position; and a feedback mechanism configured to apply a biasing force to the valve in a direction toward the first position, piston travel in the second direction tending to increase the biasing force and piston travel in the first direction tending to decrease the biasing force.