| 摘要 |
1,260,701. Piston rings. AIR PRODUCTS & CHEMICALS Inc. 17 April, 1969 [18 April, 1968], No. 19627/69. Heading F2T. A piston ring assembly for a pump or a compression or expansion chamber in a cryogenic refrigeration apparatus comprises a first, split ring 24 having end portions forming a sealed interface and a second ring 26 consisting of one or more hard segmental rings 42, 44 held by a carrier ring 38 composed of elastomeric expandable material. In operation, fluid pressure passes through clearances or passageways to the back of the first and second rings to expand them into engagement. The split ring 24 may be formed with an arcuate interface 28 at the split and may be made of P.T.F.E., metal, plastics, leather or rubber and filled or impregnated with bronze powder, graphite, carbon or molybdenum disulphide. The segmental rings 42, 44 of the second ring may be made of pyrolytic graphite, tungsten carbide or impregnated carbon and the elastomeric expandable carrier ring 38 may be made of P.T.F.E. or synthetic rubber and either impregnated with molybdenum disulphide or filled with carbon for lubricating the cylinder wall. |
