Cylinder-cushioning arrangement

Claim 1

A cushioning arrangement for a hydraulic cylinder or the like including a cylinder with an end wall and a piston retractable axially toward and extendable axially away from the end wall, said cushioning arrangement comprising: a fluid port through the cylinder at a point axially spaced from the end wall; a cushioning groove in the piston that is between the port and the end wall when the piston nears the end wall; a damping passage leading from the portside of the cushioning groove to the piston surface, through which fluid can flow between the cushioning groove and the fluid port when the piston is near the end wall; a flow passage leading from the opposite side of the cushioning groove to a surface of the piston, through which fluid can flow between the cushioning groove and the chamber between the piston and the cylinder end wall; and an axially movable damping ring in the cushioning groove that has an outer radial edge in sealing engagement with the cylinder and that is adapted to allow fluid to flow across the groove in either direction between the damping and flow passages regardless of its axial position, said damping ring being axially movable within the cushioning groove between a daMping position in which it partially blocks the damping passage to restrict fluid flowing from said chamber to the port and an open position in which it is removed from blocking the damping passage to allow unrestricted fluid flow therethrough; the flow passage being adapted, regardless of the position of the damping ring, to allow fluid to flow therethrough at a rate substantially greater than the rate of flow through the damping passage when the damping ring is in damping position.