Clearance seals and piston for cryogenic refrigerator compressors

摘要

A cermet piston 36 is positioned to reciprocate within a ceramic sleeve 58 of a cryogenic refrigerator 12. The sleeve 58 forms a very tight clearance seal 67 with the piston 36 yet is allowed to float within a large gap 66 between piston housing 35 and the sleeve. The gap 66 allows the sleeve 66 to compensate for misalignment or distortions of the piston housing 35. Elastic seals 68, 70 prevent gas blow-by between the working space 18 of the piston 36 and the piston's dead space 19. The piston is connected to a motor drive mechanism through connecting rod 44 and helium lubricated wrist pin 48.