Abstract: The present invention relates to valved cryogenic refrigerators, in particular, Gifford McMahon (GM) refrigerators, and GM type pulse tube refrigerators where gas is cycled between high and low pressures by a valve mechanism that connects to an expander. Input power is reduced by use of a buffer volume which stores gas that flows to and from the warm end of the regenerator through a valve that opens and closes during the periods when the main supply and return valves are closed and is closed when the main supply and return valves are open.

Abstract: A high separation efficacy, compact, bulk oil separator oriented horizontally and used with a scroll-type oil-lubricated compressor unit adapted to compressing helium. The horizontal bulk oil separator contains an integral oil reservoir and removes more than 99.9% of the oil from the helium that exits. The bulk oil separator contains successive chambers where oil separates from the gas by impingement.

Abstract: The problems of reducing the torque required to turn the valve, eliminating wear dust, and extending the life of the valves in Gifford McMahon (G-M) type multi-port pulse tube refrigerators are solved by using a rotary spool valve having radial clearance to control flow to and from the regenerator, and using face seal ports on the end of the spool to control flow to and from the pulse tubes.

Abstract: An oil lubricated compressor which includes a bypass oil line connecting respective oil paths upstream and downstream of the motor. The bypass oil path permits oil to be detoured around the motor in a tube that is external to the compressor shell and flows back into the shell near the scroll inlet. The oil bypass line returns “excess” oil directly to sump 28, rather than having it flow from sump 27 to sump 28 through an air-gap, thereby reducing both the drag on the motor and the input power.

Abstract: Convection losses associated with different temperature profiles in the pulse tubes and regenerators of multi-stage pulse tubes mounted in helium gas in the neck tube of a MRI cryostat are reduced by providing one or more of thermal bridges, and/or insulating sleeves between one or more pulse tubes and regenerators, and/or spacers, and spacer tubes, in one or more pulse tubes and regenerators.

Abstract: A multi valve two-stage pulse tube type GM refrigerator having a rotary valve that comprises one track for flow to the regenerator and two tracks for flow to the pulse tubes where the valve has two high pressure ports to the pulse tubes located on a single track and two low pressure ports from the pulse tubes located on a separate single track and where there are two cooling cycles per revolution of the rotary face valve.

Abstract: A range of buffer volume/pulse tube volume ratios for two-stage hybrid GM type pulse tube cold-heads that are designed to produce refrigeration at 4 K are provided. The ranges of volume ratios for the first and second stages provides a good balance between the inefficiencies but compact size of a four-valve phase shifting mechanism and the better efficiency but larger size of a double-orifice phase shifting mechanism. The buffer volumes are small enough to be conveniently machined into the warm end housing, or as an option, one can be part of a valve disc housing. The drive motor for the valve disc is in an attached housing to make the valve disc readily accessible for service.

Abstract: A two-stage pulse tube refrigerator having a compact design, low vibration and low heat loss is provided where at least the 2nd stage is co-axial but preferably, both stages are co-axial with the second stage pulse tube being central and the first stage pulse tube occupying the annular space between the second stage pulse tube and the first stage regenerator. Convection losses associated with different temperature profiles in the pulse tubes and regenerators are minimized by shifting the thermal patterns in the pulse tubes relative to the regenerators by one or more of spacers in the regenerators, physical differences in length with gas channel connections, adjustment of dc flow, and thermal bridges.

Abstract: A direct current voltage to heat the sensor wire for powering and extracting a signal voltage from a thermocouple-type vacuum sensor. The direct current used produces a DC offset in the sensor output where the heating current flow is stopped for a short interval and the unbiased sensor voltage is then sampled and stored.

Abstract: The present invention applies to single or two stage pulse tube refrigerators that have one or more passive orifices at the hot end(s) of the pulse tube(s) through which gas flows to achieve phase shifting and the phase shifting gas flow circulates to a remote heat sink by adding check valves and an appropriate piping circuit.

Abstract: Disclosed is a method of removing contaminants from a GM type cryogenic refrigerator that incorporates an oil lubricated compressor where such contaminants are introduced during servicing the refrigerator where at least some of the oil is replaced with clean oil.

Abstract: The pulse tubes (165, 175) and regenerators (160, 170) contained within a cryopump housing (210) are arranged in a way that facilitates the fabrication and installation of the cryopanels (265). The pulse tubes and regenerators are located in a common plane in the center of the cryopump housing and the cold (second stage) panels (265) that are pitched parallel to the plane with the tubes.

Abstract: This invention provides an improved means of quickly warming a pulse tube (165) by shifting the phase relation of flow to the warm end of the pulse tube relative to flow to the warm end (117) of the pulse tube relative to flow to the warm end of the regenerator (160) using a “four valve” concept and the “active buffer” concept. Several different pulse tube configurations and valve timing relations that are effective at reversing the cycle from the normal mode, which produces cooling at the pulse tube heat station, to a reverse mode that produces heating are disclosed.

Abstract: An integrated cryopump and 2 stage pulse tube refrigeration system (100) comprising a cryopump, a compressor for a pulse tube refrigerator, a pulse tube refrigerator located within the vacuum chamber of the cryopump where the hot ends of the pulse tubes (165,175) are connected to each other through a buffer volume (180), are integral to the cryopump vacuum chamber hosing, and a buffer volume (180) is connected to the hot ends (117,119) of the pulse tubes (165,175) through flow restrictors (145,150).

Abstract: Disclosed is a two-stage pulse tube cryopump cooling system in which the pulse tubes and valves are inline, with the hot ends of the pulse tubes at the top and the valve mechanism is at the bottom and the hot ends and buffer volume are cooled by an inline coolant line from the compressor input to the compressor output and attached in heat exchange relationship with the buffer volume.

Abstract: Disclosed are two-stage inter-phasing pulse tube refrigerators with and without shared buffer volumes.

Abstract: In an oil-lubricated helium compressor unit, the adsorber can retain all of the oil that might be transferred from the compressor to the adsorber before the system shuts down. No oil is ever transferred or transferable to, for example, the expander in a GM type refrigeration system connected to the unit. The compressor itself will shut down because of a protective switch or seize for lack of oil before any oil carries outside the compressor unit. The unit and the connected refrigeration system can run for more than a selected design life before the compressor shuts down because the limit of oil in the adsorber has been reached. The adsorber can retain as much oil as might leave the compressor over the life of the system plus a safety margin of at least 25%. The adsorber need not be serviced or replaced for the life of the system.

Abstract: In an oil-lubricated helium compressor unit, the adsorber can retain all of the oil that might be transferred from the compressor to the adsorber before the system shuts down. No oil is ever transferred or transferable to, for example, the expander in a GM type refrigeration system connected to the unit. The compressor itself will shut down because of a protective switch or seize for lack of oil before any oil carries outside the compressor unit. The unit and the connected refrigeration system can run for more than a selected design life before the compressor shuts down because the limit of oil in the adsorber has been reached. The adsorber can retain as much oil as might leave the compressor over the life of the system plus a safety margin of at least 25%. The adsorber need not be serviced or replaced for the life of the system.

Abstract: A throttle device provides a large number of small flow channels generally in parallel rather than a single flow path. The throttling device, a porous cartridge within a tube, may be porous metal, packed ferrous spheres or other particles, packed fibrous material, a plurality of smaller capillaries joined together in parallel, etc. The number and size of the channels provide proper pressure drop performance of the throttle, and flow is laminar with a Reynolds number less than 2,000. Vibrations are low. With certain refrigerant components, and small openings in the porous throttle device, refrigerant flow resistance increases until all flow ceases below selected and repeatable temperature levels. Thus, a temperature-dependent, variable on to off throttle device is provided without moving parts. This self adjusting throttle device can operate in parallel with a fixed throttle device.

Abstract: A precooled vapor-liquid refrigeration cycle includes a basic vapor-liquid cycle and an auxiliary regenerative vapor-liquid cycle having a heat exchange relationship between them. The basic cycle includes a compressor connected in series with a condenser, throttle device, and evaporator. The auxiliary cycle includes a compressor, condenser, throttle device, and a counterflow heat exchanger, successively connected. The cycles each have condensers that are cooled by ambient air; the basic cycle is able to operate independently of the auxiliary cycle. To maximize the coefficient of performance, the basic cycle operates with a small pressure differential between compressor discharge and return. In the heat exchanger, refrigerant flow from the basic cycle condenser is further cooled in a counterflow arrangement by the low temperature refrigerant from the auxiliary cycle until the refrigerant in the basic cycle has been precooled from near ambient temperature to near the intended refrigeration temperature.