Hydraulic shock absorber

Claim 1

A hydraulic shock absorber, comprising: a cylinder having at least two cylinder chambers defined therein for containing a hydraulic fluid; a fluid passageway for communicating said two cylinder chambers with each other; a piston disposed in said cylinder such that sliding movement of said piston in said cylinder induces hydraulic fluid flow in said fluid passageway; a damping force generating mechanism for generating a damping force restricting the hydraulic fluid flow through said passageway; and control means for selectively communicating said two cylinder chambers so as to control the damping force on the hydraulic fluid flowing between said two chambers, said control means comprising: a tubular guide having a sidewall and opposite ends, one said end being fluidly connected with one of said two cylinder chambers, and the other said end being fluidly connected with the other of said two cylinder chambers; a shutter slidably disposed in said tubular guide for sliding movement in the axial direction of said tubular guide, dividing the interior of said tubular guide into two fluid chambers, and said shutter defining a shutter passage therein; orifice means having an orifice for fluidly communicating the one said cylinder chamber with one said fluid chamber of said tubular guide only through said orifice such that said orifice creates resistance to the flow of hydraulic fluid between the one said cylinder chamber and the one said fluid chamber such that the one said fluid chamber forms a pressure chamber; passage means for fluidly communicating the other said fluid chamber with the other said cylinder chamber with substantially no resistance to the flow of hydraulic fluid therebetween; a bypass passageway for fixedly communicating said two cylinder chambers, said bypass passageway including a guide passage extending through said sidewall of said tubular guide; and means for yieldably retaining said shutter in said tubular guide in an intermediate position whereat said shutter passage fluidly communicates with said guide passage in said sidewall of said tubular guide, said bypass passageway thereby being open; wherein said shutter further has wall means for blocking said guide passage when said shutter is axially shifted from said intermediate position; and wherein said shutter is axially moveable in opposite directions from said intermediate position to block said guide passage with said wall means.