Expansion engine for cryogenic refrigerators and liquefiers and apparatus embodying the same

Claim 1

CRYOGENIC APPARATUS INCLUDING HEAT EXCHANGE MEANS ADAPTED TO EFFECT INDIRECT HEAT EXCHANGE BETWEEN FLUID STREAMS OF HIGH AND LOW PRESSURE; FLUID FLOW PATH MEANS, INCLUDING CONDUIT MEANS ADAPTED TO CONDUCT HIGH-PRESSURE AND LOW-PRESSURE FLUID THROUGH SAID HEAT EXCHANGE MEANS; ONE OR MORE FLUID EXPANSION MEANS ASSOCIATED WITH SAID FLOW PATH MEANS AND ADAPTED TO EXPAND HIGHPRESSURE FLUID AND EFFECT THE COOLING THEREOF; AND AN INSULATED HERMETICALLY SEALED HOUSING MEANS EQUIPPED WITH A COVER MEMBER THEREBY DEFINING AN INSULATED CHAMBER CONTAINING SAID HEAT EXCHANGE MEANS, SAID FLUID FLOW PATH MEANS, AND SAID FLUID EXPANSION MEANS, AND HAVING EXTERNAL CONDUIT MEANS EXTENDING THROUGH SAID COVER MEMBER AND IN FLUID COMMUNICATION WITH SAID FLUID FLOW PATH MEANS, SAID APPARATUS BEING CHARACTERIZED IN THAT AT LEAST ONE OF SAID FLUID EXPANSION MEANS COMPRISES, IN COMBINATION (A) A PISTON CYLINDER EXTENDING EXTERNALLY OF SAID HOUSING THROUGH SAID COVER MEMBER; (B) PISTON MEANS MOVABLE WITHIN SAID PISTON CYLINDER, DEFINING THEREIN AN EXPANSION CHAMBER OF VARIABLE VOLUME, AND HAVING PISTON SEALING MEANS MAINTAINED AT ESSENTIALLY AMBIENT TEMPERATURE EXTENDING EXTERNALLY OF SAID HOUSING ADAPTED TO EFFECTT A FLUID-TIGHT SEAL BETWEEN SAID PISTON AND THE INTERNAL WALL OF SAID PISTON CYLINDER; (C) AN INLET VALVE PROVIDING A CONTROLLABLE FLUID CONDUIT BETWEEN A HIGH-PRESSURE PORTION OF SAID FLUID FLOW PATH MEANS AND SAID EXPANSION CHAMBER, AND AN EXHAUST VALVE PROVIDING A CONTROLLABLE FLUID CONDUIT BETWEEN A LOW-PRESSURE PORTION OF SAID FLUID FLOW PATH MEANS AND SAID EXPANSION CHAMBER, EACH OF SAID VALVES COMPRISING, IN COMBINATION