Patent ID: 6311813
Filing Date: 2001-11-06
Classification: F16F

Abstract:
In a piston-cylinder unit including a cylinder, a piston movable axially within said cylinder, an annular groove in said piston having axially spaced sidewalls and opening towards the internal wall surface of said cylinder, a fluid flow passage extending through said piston and communicating with said annular groove, an annular sealing ring within said groove, the axial width of said sealing ring being less than the axial width of said groove and the radial depth of said sealing ring being less than the radial depth of said groove, said sealing ring being axially movable within said groove in dependence on the direction of axial movement of said piston relative to said cylinder to vary the cross sectional flow area of the fluid flowpath and thereby provide a different fluid flow rate across the piston in dependence on the direction of axial movement of said piston, said sealing ring having opposed axially spaced sidewall surfaces for sealing engagement with respective ones of said sidewalls of said groove and a radially outer wall surface for sealing engagement with the internal wall surface of said cylinder, the improvement comprising:each of said sidewall surfaces of said sealing ring being axially relieved over at least a portion of its radial extent adjacent said radially outer wall surface to define a sidewall sealing surface on each sidewall surface of reduced radial extent relative to the radial extent of said each sidewall surface; andsaid sealing ring sidewall surfaces being substantially symmetrical in transverse cross section.