Double-acting hydraulic piston-and-cylinder device

摘要

A double-acting hydraulic piston-and-cylinder unit adapted to constitute a damper for movements in a human joint prosthesis has a boot sealingly connected to the cylinder and the piston rod to receive the hydraulic fluid under pressure as the hydraulic fluid is displaced from one or the other of two cylinder chambers upon displacement of the piston rod. The boot has a conically widening region or segment sealingly secured to the rod and adjoining the cylindrical segment of the boot surrounding the cylinder in a transition segment formed as an outwardly convex bulge and designed to ensure that initial inward movement of the piston rod will give rise to a plate membrane deformation of the elastic boot while only further displacement will result in a rolling action of the membrane. This ensures a generally cylindrical uniform configuration of the boot in all positions of the rod as is essential for effective use in a prosthesis.