US Patent 9080634 Shock absorber with frequency dependent passive valve

A shock absorber has a pressure tube with a piston assembly slidably disposed within the pressure tube and attached to a piston rod. The piston assembly divides the pressure tube into an upper working chamber and a lower working chamber. The piston assembly includes a frequency dependent valve assembly attached to the piston rod which defines a housing attached to the piston rod and a piston disposed within the housing. The piston moves within the housing to control the fluid flow through a bypass fluid passage that bypasses the piston assembly.