Abstract: In a cryogenics refrigerator having a piston or piston-like displacer reciprocating in a cylinder, the position of the piston or displacer, the temperature at the cold end of the cylinder and/or a refrigeration gas pressure wave are monitored to provide one or more feedback signals. Valves or a linear motor drive are controlled through electronic control circuitry which responds to the feedback signals. A displacer may be driven by pressure differentials on a drive piston or by an electric motor. The preferred elements provide feedback throughout the refrigeration cycle and include a linear variable displacement transformer and an encoder disc. Preferably, the control circuitry is in the form of a programmable digital processor.

Abstract: Valves for controlling process gas at the cold end of an expansion engine are fluid actuated. The actuating fluid is controlled by a solenoid actuated spool valve positioned at ambient temperature. The fluid is cooled in a thermally regenerative flow path extending between the solenoid actuated valve and the fluid actuated valve.

Abstract: A Stirling refrigeration system includes a compressor having a piston which reciprocates within a cylinder. The piston compresses and expands a working volume of gas to cause sinusoidal variations in gas pressure in a cold finger unit. The mean pressure in the working volume is stabilized, despite gas leakage past the compressor piston seals, by a U-cross-section annular-lip seal in a groove surrounding the piston. A spacer ring within the annular-lip seal and extending beyond the legs of the seal retains the seal away from one of the opposing faces of the groove to insure that the seal consistently tends to permit greater gas leakage in a predetermined direction. With gas leakage in that predetermined direction, the gas pressure reaches a steady condition in which the mean pressure in the working volume of gas is stable relative to the pressure in an hermetically sealed larger crankcase volume of gas on the opposite side of the piston.

Abstract: In a cryogenic apparatus wherein the refrigerator has a reciprocable displacer which must be coordinated with fluid control means, such as a rotary valve, to control the inlet and exhausting of high and low pressure fluid, respectively, to produce cooling, an improvement is disclosed comprising including means for providing proper coordination between displacer movement and fluid control means regardless of the direction in which the motor drive shaft is rotated.

Abstract: A vuilleumier-cycle refrigeration system of the type including first and second communicating, sealed, cylindrical, vessels having first and second displacers respectively mounted therein in sliding, sealing contact with the inner walls thereof, includes magnetic linkage between the two displacers for driving the displacers within the sealed vessels without contaminating the sealed vessels. With regard to the magnetic linkage, there are smaller, auxiliary cylindrical vessels coupled respectively to the first and second vessels, having smaller diameters, and thinner walls than the first and second vessels. Rods attached to the displacers and extending into the auxiliary vessels have magnetic material followers attached thereto. Magnetic-material drivers are moveable along the auxiliary vessels, opposite the followers, to thereby attract and move the magnetic-material followers and their attached displacers.This is a division of application Ser. No. 665,848, filed Mar. 17, 1976, now U.S. Pat. No. 4,118,943.