Two-tube hydropneumatic shock absorber

Abstract

A hydropneumatic shock absorber comprises an outer tube centered on an upright axis, an inner tube coaxially spaced inside the outer tube and forming therewith an outer gas/liquid chamber, a piston rod inside the inner tube, generally coaxial with the tubes, and forming with the inner tube an inner liquid chamber, and a piston carried on the rod and radially outwardly engaging the inner tube, whereby axial displacement of the piston and rod relative to the tubes in one direction pressurizes the inner chamber. A foot valve between the inner and outer chambers permits limited liquid flow therebetween. An annular plug is fixed at the upper axial ends of the tubes and axially upwardly blocks the inner and outer chambers. A guide bushing in the plug surrounds the piston rod and an annular outer seal in the plug surrounds the piston rod above the bushing and forms with the bushing and plug an annular compartment surrounding the rod. The plug is formed with an inner passage having one end opening into the compartment and another end opening into the inner chamber and with an outer passage having one end opening into the compartment and another end opening into the outer chamber. A porous body is provided in the inner passage and a check valve in the outer passage permits flow only from the compartment into the outer chamber. An annular inner seal in the plug and surrounds the piston rod immediately below the bushing.