Patent ID: 6698729
Filing Date: 2004-03-02
Classification: F16F

Abstract:
A gas spring for moving a load relative to a body between a closed position of the load relative to the body, corresponding to a retracted position of the gas spring, and an open position of the load relative to the body, corresponding to an extended position of the gas spring, comprising:a cylinder member having an axis, an inner surface forming a chamber, a rod end and a closed end; a piston rod seal/guide received in the rod end of the cylinder member; a piston rod received in the seal/guide for movement into and out of the cylinder member between said retracted and extended positions of the gas spring; a floating piston received in the cylinder member for movement along the axis and in sealed engagement with the inner surface to define in the chamber a gas section between the floating piston and the rod end and a closed end section between the floating piston and the closed end; a piston assembly mounted on the axially inner end of the piston rod within the gas section; a mass of gas under a pressure above atmospheric pressure contained in the gas section on both axial sides of the piston assembly; means for moving the floating piston axially of the cylinder member to vary the pressure of the gas in the gas section; means for sensing a characteristic of the gas spring indicative of the force applied to the rod by the gas in the gas section and producing a signal indicative thereof; and means for controlling the means for moving the floating piston in response to the signal, at least in the retracted position of the gas spring, so as to vary the volume of the gas section of the cylinder member such that the force exerted on the piston rod by the gas is maintained at a substantially constant predetermined level at the closed position of the load sufficient to move the load away from the closed position.