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. The piston and valves can be either mechanically or pneumatically actuated and the pressures above and below the piston can be nearly equal by virtue of a regenerator that connects the two spaces or by valves.

Abstract: A hybrid expander combines a Brayton engine first stage with one or more GM colder stages that uses the flow from the Brayton engine to provide refrigeration at one or more remote heat stations.

Abstract: To provide refrigeration below 200 K, a Brayton cycle engine contains a light reciprocating piston. The refrigerator includes a compressor, a gas-balanced reciprocating engine having a cold rotary valve, a counterflow heat exchanger, a gas storage volume with valves that can adjust system pressures, a variable speed engine and a control system that controls gas pressure, engine speed, and the speed of the piston. The engine is connected to a load such as a cryopanel, for pumping water vapor, through insulated transfer lines.

Abstract: This invention relates generally to oil lubricated helium compressor units for use in cryogenic refrigeration systems, operating on the Gifford McMahon (GM) cycle. The objective of this invention is to keep the oil separator and absorber, which are components in an oil lubricated, helium compressor, in an indoor air conditioned environment while rejecting at least 65% of the heat from the compressor outdoors during the summer. The balance of the heat is rejected to either the indoor air conditioned air, or cooling water. This is accomplished by circulating hot oil at high pressure to an outdoor air cooled heat exchanger and returning cooled oil to the compressor inlet, while hot high pressure helium is cooled in an air or water cooled heat exchanger in an indoor assembly that includes the compressor, an oil separator, an oil absorber, and other piping and control components. It is an option to reject the heat from the oil to the indoor space during the winter to save on the cost of heating the indoor space.

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. Low pressure on a piston drive stem provides a force imbalance to move the piston towards the warm end.

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. Low pressure on a piston drive stem provides a force imbalance to move the piston towards the warm end.

Abstract: A refrigeration system for minimizing the cool down time of a mass to cryogenic temperatures including a compressor, an expander, a gas storage tank, interconnecting gas lines, and a control system. The compressor output is maintained near its maximum capability by maintaining near constant high and low pressures during cool down, gas being added or removed from the storage tank to maintain a near constant high pressure, and the speed of said expander being adjusted to maintain a near constant low pressure, no gas by-passing between high and low pressures.

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: 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. The piston and valves can be either mechanically or pneumatically actuated and the pressures above and below the piston can be nearly equal by virtue of a regenerator that connects the two spaces or by valves.

Abstract: Apparatus and method for controlling the speed for a GM type expander includes relays that interrupt power when the current in the line is zero. The speed controller apparatus limits the maximum speed providing the expander with sufficient gas to meet its cooling requirements.

Abstract: A rotary valve unit which reduces the torque required to turn the valve disc, and the amount of wear dust that is blown into the cold head, using differential gas forces to keep the valve disc in contact with the valve seat, and which enables larger diameter valve discs to be utilized for multi-ported pulse tubes that have less force on the face of the valve disc, resulting in reduced torque and reduced wear rate.

Abstract: A standard size cryopump adapted to be mounted behind a nonstandard gate valve by extending the inlet array to a larger diameter. A standard size cryopump adapted to be mounted behind a nonstandard gate valve by using an extension attached to flanges, where the flanges correspond to the diameter of the nonstandard gate valve.

Abstract: An improved method of reducing wear dust and torque required to turn a multi-port rotary disc valve utilizes a thrust bearing to hold the valve seat and/or valve disc such that they are not in contact with each other, or have light contact each other.