Abstract: A twin tube shock absorber has concentric inner and outer tubes connected to the wheel of a vehicle. A piston in the inner tube is connected to the chassis of the vehicle and divides the interior of the inner tube into upper and lower chambers. Fluid passes between these chambers and an annular reservoir between the tubes for absorbing shock in a conventional manner. An orifice is provided through the sidewall of the lower portion of the inner tube and is surrounded by a lower sleeve, which normally keeps the orifice closed. Upon upward acceleration of the tubes, the sleeve essentially remains fixed in space. The relative movement between the sleeve and tubes aligns a passage through the sleeve with the orifice and permits fluid to flow from the lower chamber below the piston to the annular reservoir. This provides a softer shock absorber when high upward acceleration is felt by the tubes of the shock absorber and a stiffer shock absorber during times when there is no large upward acceleration.

Abstract: A shock absorber which is inertia responsive in both compression and extension strokes to provide rapid flow in either direction responsive to rapid large changes in loading as caused by a bump or dip. The inertia responsive valving is located in the piston or the piston rod or both affording simple shock absorber body design and simple cooling. The inertia responsive valving members are longitudinally slidable and of substantially uniform cross section so as to be substantially immune to acceleration forces due to turns and are substantially insensitive to pressure changes.