Piston guide and seal for dual-tube hydropneumatic shock absorber

Abstract

A hydropneumatic shock absorber has an outer tube, an inner tube inside the outer tube, forming therewith an outer gas/liquid chamber and itself internally forming an inner chamber and a piston rod inside the inner tube. A body of liquid fills the entire inner chamber and partially fills the outer chamber. A piston on the rod subdivides the inner chamber into an upper and a lower compartment. A foot valve is located at the lower tube ends. A rigid centering washer has an outer periphery engaged against the upper end of the outer tube and an axially extending ridge engaged directly radially against the upper end of the inner tube. A flexible annular outer lip on the washer engages radially against the upper end of the inner tube to bear flexibly to permit limited fluid flow from the upper compartment to the outer chamber while blocking opposite flow. A flexible annular inner seal underneath the ridge on the washer engages radially inwardly against the piston rod. An outer seal on the washer engages against the outer tube so the washer and outer seal upwardly close off the outer chamber. An upwardly open pocket down into which the inner seal projects is provided in the inner tube at its upper end. A passage extends from the inner chamber past the pocket so that gas collecting in the inner chamber can bleed up past the pocket and then pass by the lip into the outer chamber.