Hydraulic shock absorber for vehicles

Claim 1

A hydraulic shock absorber for vehicles, comprising: inner and outer cylinders filled with a working oil; a piston slidably fitted in said inner cylinder; a piston rod supporting said piston; a bottom valve disposed at the bottoms of said inner and outer cylinders; a first passage provided in said piston so as to pass axially therethrough; a first valve means operatively cooperating with said first passage; a second passage provided in said bottom valve for providing communication between said inner and outer cylinders; a second valve means operatively cooperating with said second passage; a casing defining an oil chamber therein, said oil chamber being arranged to be in communication with the interior of said inner cylinder; a gas chamber hermetically defined by an elastic metal membrane, said gas chamber having gases confined therein; said gas chamber being disposed in said oil chamber; said elastic metal membrane defining said gas chamber being elastically deformable while compressing said gases in said gas chamber at a rate corresponding to a rising oil pressure in said oil chamber during only an initial stage of at least a compression stroke of said piston; the pressure of said gases confined in said gas chamber being set substantially at atmospheric pressure, such that it is substantially the same as said working oil pressure when said piston stands still; and the volume V (cm 3 ) of said gases in said gas chamber being such that: V≦0.75πd.sup.2 or 0.75π(D.sup.2 -d.sup.2) wherein d=the diameter of said piston rod (in centimeters) and D=the inside diameter of said inner cylinder (in centimeters).