Abstract: A recovery cryostat, external to a cryogen storage tank, uses a cryocooler to condense vapor of cryogen from the storage tank and return the cryogen to the storage tank as a liquid. The process may be continuous or cyclical depending on the orientation of the recovery cryostat. If the recovery cryostat is located such that liquid can drain back to the storage tank, the process can be continuous. If the liquid cannot be drained back, a valve on the liquid return line is closed while the cryocooler condenses the vapor, a valve on the vapor supply line is then closed, the valve on the liquid return line is opened, and pressure in the recovery cryostat is increased to drive the liquid out. The storage tank is a type that can have vapor that boils off external to the tank be returned to the vapor space above the liquid in the tank.

Abstract: A pneumatically driven cryogenic refrigerator operating primarily on the Gifford-McMahon (GM) cycle is switched from cooling to heating by a switch valve between a rotary valve and a drive piston that causes the displacer to reciprocate. The rotary valve has ports at two radii, one that cycles flow to the displacer and a second that cycles flow to the drive piston. Two ports cycle flow to the top of the drive piston, the “cooling” port optimizes the cooling cycle and the “heating” port provides a good heating cycle. A switch valve that changes the flow from one port to the other can be linearly or rotary actuated. The rotary valve does not reverse direction.

Abstract: A heat station for a GM or Stirling cycle expander provides a versatile, efficient, and cost effective means of transferring heat from a remote load at cryogenic temperatures that is cooled by a circulating cryogen to the gas in a GM or Stirling cycle expander as the gas flows between a regenerator and a displaced volume. The heat exchanger includes a shell that has external and internal fins that are thermally connected, are aligned parallel to the axis of the shell, and are enclosed in a housing having a single port on the bottom of the housing.

Abstract: The object of this invention is to increase the life of the displacer and stem seals of the reciprocating displacer of a Gifford McMahon (GM) cryogenic expander. The seal comprises a ring that is relatively long and thin and uses the pressure difference across the seal, acting behind the ring, as the primary force to bring the ring into contact with the cylinder and stem walls. The pressure difference across the seal ring pushes the ring to one end of the groove, and the friction force pushes the ring in the same direction while it is moving. The sealing force is distributed over a larger area compared with a conventional backed “O” ring thus reducing the wear rate and increasing the seal life.

Abstract: A Gifford-McMahon (GM) type double-inlet pulse tube system providing cooling at cryogenic temperatures is provided. The system has a co-axial double-inlet valve that includes a base having an adjustable port, a fixed needle partially engaged in one end of the adjustable port, an adjustable needle partially engaged in another end of said adjustable port, and a body for housing the base, the fixed needle and the adjustable needle. The base is configured to be adjustable along an axial direction. The adjustable needle is arranged co-axially with the fixed needle. The adjustable port and the adjustable needle are configured to control an alternating current (AC) flow and a direct current (DC) flow between the stem port and the end port and to produce the DC flow in either direction between the stem port and the end port.

Abstract: A pneumatically driven cryogenic refrigerator operating primarily on the Gifford-McMahon (GM) cycle is switched from cooling to heating by a switch valve between a rotary valve and a drive piston that causes the displacer to reciprocate. The rotary valve has ports at two radii, one that cycles flow to the displacer and a second that cycles flow to the drive piston. Two ports cycle flow to the top of the drive piston, the “cooling” port optimizes the cooling cycle and the “heating” port provides a good heating cycle. A switch valve that changes the flow from one port to the other can be linearly or rotary actuated. The rotary valve does not reverse direction.

Abstract: A Gifford-McMahon (GM) type double-inlet pulse tube system providing cooling at cryogenic temperatures is provided. The system has a co-axial double-inlet valve that includes a base having an adjustable port, a fixed needle partially engaged in one end of the adjustable port, an adjustable needle partially engaged in another end of said adjustable port, and a body for housing the base, the fixed needle and the adjustable needle. The base is configured to be adjustable along an axial direction. The adjustable needle is arranged co-axially with the fixed needle. The adjustable port and the adjustable needle are configured to control an alternating current (AC) flow and a direct current (DC) flow between the stem port and the end port and to produce the DC flow in either direction between the stem port and the end port.

Abstract: A double-inlet valve for a Gifford-McMahon (GM) type double-inlet pulse tube cryocooler system for providing cooling at cryogenic temperatures includes a fixed restrictor and a needle valve coupled to the fixed restrictor in parallel. The needle valve produces asymmetric flow. The combination of the fixed restrictor and the needle valve having an asymmetric flow provides improved alternating current (AC) flow characteristics and adjustability of direct current (DC) flow to increase the available cooling.

Abstract: This invention relates to oil lubricated helium compressor units for use in cryogenic refrigeration systems, operating on the Gifford McMahon (GM) or Brayton cycle. The objective of this invention is to provide redundancy by having a water cooled compressor manifolded to an air cooled compressor and sensors to detect faults so that an expander can be kept running if there is a failure in either the water or air supply.

Abstract: A hybrid expander for producing refrigeration at a cryogenic temperature includes a Brayton expander producing refrigeration at a first temperature; a GM expander producing refrigeration at a second temperature, the first temperature being colder than the second temperature, the second temperature being 200K or less. A high pressure line receives a gas from a compressor at a first pressure and supplies it at the first pressure to the Brayton expander and the GM expander simultaneously. A low pressure line returns the gas to the compressor at a second pressure from the Brayton expander and the GM expander, the first pressure being greater than the second pressure. The Brayton expander piston is attached to the cold end of the GM expander displacer and the Brayton expander piston and the GM expander displacer reciprocating together.

Abstract: This invention relates to oil lubricated helium compressor units for use in cryogenic refrigeration systems, operating on the Gifford McMahon (GM) or Brayton cycle. The objective of this invention is to provide redundancy by having a water cooled compressor manifolded to an air cooled compressor and sensors to detect faults so that an expander can be kept running if there is a failure in either the water or air supply.

Abstract: An expansion engine operating on a Brayton cycle which is part of a system for producing refrigeration at cryogenic temperatures that includes a compressor, a counter-flow heat exchanger, and a load that may be remote, which is cooled by gas circulating from the engine. The engine has a piston in a cylinder which has nearly the same pressure above and below the piston while it is moving. A valve connecting the warm end of the cylinder to a buffer tank allows a partial expansion and recompression of gas in the cold displaced volume that increases the refrigeration produced in each cycle with the same compressor flow rate.

Abstract: Losses in the connecting line between the Pressure Wave Generator and the cold head of a GM type pulse tube refrigerator, are reduced while maintaining or improving upon the desirable features of a standard corrugated hose connecting line including vibration isolation, separation distance, and mounting convenience. The basic means are to reduce the internal void volume of the convolutions in a corrugated hose in combination with reducing the number of corrugations, adding fillers to the void volumes, and vibration absorbing coatings.

Abstract: A heat station for a GM or Stirling cycle expander provides a versatile, efficient, and cost effective means of transferring heat from a remote load at cryogenic temperatures that is cooled by a circulating cryogen to the gas in a GM or Stirling cycle expander as it flows between a regenerator and a displaced volume. The heat exchanger comprises a shell that has external and internal fins thermally connected to it that are aligned parallel to the axis of the shell and enclosed in a housing having an inlet port and an outlet port on the bottom of the housing.

Abstract: A heat station for a GM or Stirling cycle expander provides heat transfer from a remote load at cryogenic temperatures that is cooled by a circulating cryogen to the gas in a GM or Stirling cycle expander as the cryogen between a regenerator and a displaced volume. The heat exchanger includes a shell that has external and internal fins thermally connected to the shell that are aligned parallel to the axis of the shell and enclosed in a housing having an inlet port and an outlet port on the bottom of the housing.

Abstract: A cryogenic refrigerator system with heaters is constructed in modular form to serve as a portable servicing system to warm up and then cool down a target object by circulating a gaseous cryogen through a target object cryostat without moving the target object or breaking its vacuum. The main module is a refrigerator cryostat containing a fan that circulates gas through one or more heat exchangers which can warm or cool the gas by heaters and by one or more GM or Brayton cycle expanders. Additional components including one or more compressors, a gas charge and vent assembly, a control system, gas lines, power lines, and vacuum jacketed transfer lines can be assembled in the main module or additional modules. An example is a system that can be wheeled through a hospital to service a MRI cryostat.

Abstract: A cryogenic expander maximizes the energy absorbing capacity of bumpers that prevent the displacer or piston in a pneumatically driven expander from hitting the cold or warm end of a cylinder. A collar at the warm end of the piston which has the same outside diameter as the piston and a lip at the warm end that engages an “O” ring before the piston hits the cold end or bottom of the cylinder. The warm end of the collar also engages an “O” ring before the pistons hits the warm end or top of the cylinder. Having “O” rings that are near the maximum diameter of the cylinder maximizes the amount of energy they can absorb, and thus permits quiet operation of larger size expanders than prior designs.

Abstract: A cryogenic refrigerator system with heaters is constructed in modular form to serve as a portable servicing system to warm up and then cool down a target object by circulating a gaseous cryogen through a target object cryostat without moving the target object or breaking its vacuum. The main module is a refrigerator cryostat containing a fan that circulates gas through one or more heat exchangers which can warm or cool the gas by heaters and by one or more GM or Brayton cycle expanders. Additional components including one or more compressors, a gas charge and vent assembly, a control system, gas lines, power lines, and vacuum jacketed transfer lines can be assembled in the main module or additional modules. An example is a system that can be wheeled through a hospital to service a MRI cryostat.

Abstract: A heat station for a GM or Stirling cycle expander provides a versatile, efficient, and cost effective means of transferring heat from a remote load at cryogenic temperatures that is cooled by a circulating cryogen to the gas in a GM or Stirling cycle expander as it flows between a regenerator and a displaced volume. The heat exchanger comprises a shell that has external and internal fins thermally connected to it that are aligned parallel to the axis of the shell and enclosed in a housing having an inlet port and an outlet port on the bottom of the housing.

Abstract: This invention relates generally to oil lubricated helium compressor units for use in cryogenic refrigeration systems, operating on the Gifford McMahon (GM) cycle. This invention provides redundancy between water cooling and air cooling if there is a blockage in the water or air supply by having air and water cooled after-coolers in series or parallel.