Abstract: A shock absorber is constructed with a hollow cylinder within which a first piston is disposed to move coaxially. A well is defined within the first piston to receive a second piston. The first piston is also provided with longitudinally extending dampening passageways and relief passageways. A cavity of variable volume filled with a compressible fluid, such as air, is defined between the two cylinders. At the start of a stroke of movement of the first piston within the cylinder, the additional length of the piston rod which enters the cylinder as the first piston moves toward the blind end of the cylinder increases pressure on the compressible fluid within the cylinder. The second piston is thereby pressed further into the first piston and ultimately closes off the dampening passageways, thereby preventing further movement of the first piston and increasing the dampening characteristics of the shock absorber.

Abstract: A shock absorber itself is of the fluid piston-cylinder type and is provided in combination with a fluid reservoir containing a hydraulic compressible fluid under high pressure. A check valve is connected between the shock absorber cylinder and the reservoir for passing fluid from the cylinder to the reservoir when the pressure of fluid in the cylinder exceeds the high pressure of fluid in the reservoir. A pressure relief valve in turn connects the reservoir to the cylinder and is set to open a controlled amount to thereby control the pressure of fluid in the cylinder. The pressure of fluid in the cylinder determines the force exerted on the piston tending to move it out of the cylinder. Also, this pressure controls the viscosity of the fluid and thus the damping characteristics of the shock absorber.