US Government As Represented by the Secretary of the Army

Mark S Asher

Stuart B Horn

Howard L Dunmire

Richard A Wright

A means for producing an optimized cooler expander waveform for a closed le cryogenic cooler. The cooler displacer is driven by magnetic and spring biasing means through four repeated phases of each cycle to produce four portions of the optimized cooler waveform in which each portion takes up about 25% of the total cycle. The portions are comprised of a constant velocity in opposite direction and dwell times with smoothed corner transitions between each portion. Control means for controlling the displacer movement to produce the specific waveform may be provided by a function generator applying the desired waveform into a displacer control drive circuit which has as a second input a sensory signal of the actual position of the displacer. The actual position and the desired position are continuously compared while the drive circuit drives two opposing solenoids during the constant velocity phases of the displacer movement with two spring biasing means holding the displacer during the dwell times at the end of each stroke.

Means for producing an optimized cooler expander waveform

A Stirling Cooler with a three stage cold finger. The finger includes a sped displacer in a stepped cylinder. The cylinder is loosely surrounded by an outer shell, with regenerator material in the space between the outer shell and the cylinder. The displacer-cylinder define three swept expansion spaces each communicating with the regenerator space. Clearance seals exist between the displacer and the cylinder because of small diametrical clearance and long axial length with respect to the diametrical clearance.

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Woodbridge, VA, United States of America

Mark S Asher