Abstract: A method and apparatus for controlling the reciprocal movement of a free piston, gas-driven displacer in a cooling engine are disclosed. A bi-directional magnetic "detent" is established for the displacer at both the top dead center and bottom dead center portions of the cooling cycle. Each bi-directional magnetic "detent" provides a magnetic snubbing force to limit overshooting of the displacer in one direction and a magnetic retention force to hold the displacer from moving in the other direction until a pre-determined pressure differential is established across the displacer's drive piston. The magnetic "detents" are formed by means of a three pole double magnet with a single core or alternatively, by a two pole single magnet with a double core. The magnetic snubbing and retention forces can be made equal or unequal in magnitude either through the selection of permanent magnet(s) or core configuration(s) or by controlling the field strength of electro-magnets.

Abstract: The disclosed system produces liquid nitrogen from ambient air which is supplied under pressure to a membrane separator. Most of the gases other than nitrogen permeate the membranes, and are vented to the atmosphere leaving almost pure nitrogen gas. The nitrogen gas is then supplied to a Dewar container in the neck of which is mounted the cylindrical cold head of a miniature cryogenic refrigerator. The temperature of the cold head is maintained below the liquefaction temperature of the nitrogen so that the gas is liquified as it passes over the cold head in heat exchanging relationship.

Abstract: A method and apparatus for snubbing the movement of a free, gas-driven displacer in a cooling engine are disclosed. The reciprocal movement of the free, gas-driven displacer is snubbed in each direction of movement as the displacer approaches top dead center and bottom dead center of its cycle by means of a magnetic snubber. Magnetic repulsion forces are generated between the displacer and the displacer containing cylinder of the cooling engine as the displacer approaches both top dead center and bottom dead center of its cycle. Each magnetic repulsive force is non-linear with respect to the displacer and the corresponding end of the displacer containing cylinder.

Abstract: The cryogenic refrigerator includes a movable displacer within an enclosure having first and second chambers of variable volume. A refrigerant fluid is circulated in a fluid path between said chambers and correlated with movement of the displacer. A spool valve controls introduction of high pressure fluid and low pressure fluid to said chambers. The displacer movement is controlled by an electric motor which has a cam for reciprocating the spool valve member. The refrigerator is converted into a source of heat by reversing the direction of rotation of said electric motor.

Abstract: In a cryogenic refrigerator, a refrigerant is circulated in a fluid flow path between first and second chambers by the movement of a displacer means. A slide is connected to the displacer means and reciprocated by a motor. The slide has an axial passage communicating the first and second chambers. The slide has a piston for varying the volume of gas in a third chamber during its reciprocation. The need for a separate compressor is eliminated.

Abstract: A cryogenic refrigeration is disclosed for operation in a first mode wherein an electrical motor reciprocates a displacer, and in a second mode wherein the displayer is reciprocated by both the motor and fluidic pressure, and in a third mode wherein the displacer is reciprocated by fluidic pressure.

Abstract: The cryogenic refrigerator includes a movable displacer within an enclosure having first and second chambers of variable volume. A refrigerant fluid is circulated in a fluid path between said chambers and correlated with movement of the displacer. A spool valve controls introduction of high pressure fluid and low pressure fluid to said chambers. The displacer movement is controlled by an electric motor which has a cam for reciprocating the spool valve member.

Abstract: The cryogenic refrigerator includes a movable displacer within an enclosure having first and second chambers of variable volume. A refrigerant fluid is circulated in a fluid path between said chambers by movement of the displacer. A spool valve controls introduction of high pressure fluid and low pressure fluid. The displacer movement is controlled by fluidic pressure instead of an electric motor.

Abstract: The cryogenic refrigerator includes a movable displacer within an enclosure having first and second chambers of variable volume. A refrigerant fluid is circulated in a fluid path between said chambers by movement of the displacer. A spool valve controls introduction of high pressure fluid and low pressure fluid. The displacer movement, at least at top dead center and bottom dead center is controlled by an electric motor.

Abstract: The cryogenic refrigerator includes a movable displacer within an enclosure having first and second chambers of variable volume. A refrigerant fluid is circulated in a fluid path between said chambers by movement of the displacer. A spool valve controls introduction of high pressure fluid and low pressure fluid. The displacer movement is controlled by an electric motor.

Abstract: Cryogenic refrigeration apparatus characterized as an in-line Stirling engine wherein the piston and displacer are driven by means mechanically linking them to move in phase along a common axis. The flow of fluid between the compressor and expander is controlled by fluid flow control means, actuated by the motion of the driving means, which makes possible the achievement of essentially constant volume heat removal.

Abstract: A gas-driven fluid flow control valve capable of responding to a signal to alter the direction of fluid flow therethrough. When the valve is interposed between high- and low-pressure fluid reservoirs on one side and a cryogenic refrigerator requiring the supplying of high-pressure fluid and the discharging of low-pressure fluid on the other side, it may be used to reverse the flow of fluid through the refrigerator to switch it from a cooling to a warming mode. The incorporation of such a refrigerator into a cryopump in conjunction with the gas-driven valve makes it possible to rapidly warm up the condensing and adsorbing surfaces of the cryopump thus reducing the regeneration cycle of the cryopump from several hours to about 30 to 35 minutes.

Abstract: A cryogenic refrigerator is disclosed which essentially comprises a cylinder, a displacer slidably mounted within the cylinder so as to form a chamber whose volume varies with movement of the displacer, drive means mechanically connected to the displacer for causing the displacer to reciprocate, and valve means for continuous flow of a refrigerant fluid into and out of the chamber, the valve means being operable by said displacer so as to (a) cause high pressure refrigerant fluid to enter the chamber during a first selected portion of the displacer's operating stroke and (b) exhaust low pressure fluid from the same chamber during a second selected portion of the displacer's operating stroke.

Abstract: A cryogenic refrigerator is disclosed which features a novel combination of displacer and refrigerant flow control means. The displacer comprises two sections, with one displacer section being arranged to vary the volume of a first chamber as the displacer undergoes reciprocating motion, and the other displacer section being arranged to vary the volume of a second chamber during the same motion. The first and second chambers, which serve as working chambers from the standpoint of achieving refrigeration, are connected by first and second heat exchangers and first and second thermal regenerators respectively and a flow control means to high and low pressure sources of refrigerant fluid. The flow control means comprises a slide valve which is movable by the displacer and coacts therewith to control movement of refrigerant into and out of the first and second working chambers as their volumes change with movement of the displacer.

Abstract: A self-regulating cryogenic refrigerator is disclosed which features a displacer and novel refrigerant flow control means comprising a slide valve which is movable by the displacer and coacts therewith to control movement of refrigerant into and out of a chamber whose volume varies with movement of the displacer.

Abstract: An improved valve is provided for controlling the flow of working fluid in a cryogenic refrigerator of the type comprising a reciprocating displacer. The valve has a slidable valve member which is arranged to alternately introduce working fluid to or remove working fluid from a cooling chamber in response to reciprocating movement of the displacer. The valve is constructed so as to make certain that sliding movement of the valve member is not restricted by the working fluid.

Abstract: A cryogenic cooler is disclosed which features a displacer and refrigerant flow control means comprising a first slide valve moveable by the displacer means and a second reversible valve operable separately from the first slide valve.

Abstract: A stacked disc heat exchanger for a refrigerator cold finger includes a plurality of discs positioned within a cold finger cylinder and clamped to a cylinder end plate. Radial gas flow passages between the plates join inner and outer longitudinal gas flow passages. The radial passages provide a large surface area for contacting refrigeration gas and effecting efficient heat exchange with a load attached to the end plate. In a preferred embodiment the radial passages are flat grooves in the faces of discs. The stack of discs provides ease in assembly and great flexibility in designing the heat exchanger for particular applications.

Abstract: A heat transfer roller embodying a heat pipe is disclosed. The heat pipe is mounted on a shaft, and the shaft is adapted for rotation on its axis.

Abstract: An improvement in vacuum presses for mounting and laminating graphic arts objects such as photographs and the like, the improvement consisting of providing a platen assembly comprising a flexible metal platen that is supported only at its edges and is engaged and heated by a flexible heater unit.