The United States of America As Represented by the Administrator of the

Jack Evans

Philip A Studer

A vibration free fluid compressor particularly adapted for Stirling cycle cryogenic refrigeration apparatus comprising a pair of identical opposing ferromagnetic pistons (10, 12) located in a housing (22) and between a gas spring including a sealed volume (52, 54, 60) of a working fluid such as gas under pressure. The gas compresses and expands in accordance with movement of the pistons (10, 12) to generate a compression wave which can be vented out to other apparatus, for example, a displacer unit in a Stirling cycle engine. The pistons (10, 12) are urged outwardly due to the pressure of the gas; however, a fixed electromagnetic coil assembly (56), located in the housing adjacent the pistons, is periodically energized to produce a magnetic field which interlinks the pistons (10, 12) in such a fashion that the pistons are mutually attracted to one another. The mass of the pistons (10, 12) in conjunction with the compressed gas between them form a naturally resonant system which when the pistons are electromagnetically energized, produce an oscillating compression wave in the entrapped fluid medium.

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Baltimore, MD, United States of America

Jack Evans