Dual pneumatic volume for cryogenic cooler

Claim 1

A means for controlling the movement of a free displacer in a cryogenic cooler comprising: an enclosed cooler housing having a regenerator-displacer with a first pneumatic piston rigidly attached thereto which extends through a passageway into an ambient temperature end of said cooler housing and a regenerator-matrix within said free displacer at a cold end of said cooler housing wherein the mating surfaces between said first pneumatic piston and said passageway forms an effective frictional seal between said ambient temperature end and said cold end wherein a working fluid in said cold end has alternating pressure waves applied thereto from a remote compressor to move said free displacer reciprocally within said enclosed cooler housing; and a dual pneumatic volume means in said ambient temperature end to limit movement of said free displacer at its extreme ends of reciprocal movement to provide pneumatic braking in the form of flat displacer waveform dwell times, said dual pneumatic volume means comprised of a pneumatic bounce volume into which said first pneumatic piston extends and a pneumatic spring volume formed inside said first pneumatic piston between a second pneumatic piston moveably positioned along an inside surface of said first pneumatic piston and extending to said enclosed cooler housing at the end of said pneumatic bounce volume wherein compressin within said pneumatic spring volume during the compression cycle of said working fluid and expansion within said pneumatic spring volume during the expansion cycle of said working fluid causes pneumatic braking of said free displacer at the top dead center and bottom dead center to provide flat displacer waveforms.