Patent ID: 6428014
Filing Date: 2002-08-06
Classification: F16J,Y10S

Abstract:
An oil-free reciprocating gas compressor or vacuum pump apparatus, said apparatus comprising a cylinder and a piston arranged to reciprocate within the cylinder, said piston comprising a rider ring retained in an annular recess in the periphery of the piston, said rider ring being a non-sealing fit in the cylinder and being arranged to centre the piston in the cylinder during said reciprocating movement, and a piston sealing ring assembly carried by the piston and including a first and a second cut piston sealing ring each bounded by first and second planar surfaces, a second planar surface of the first piston sealing ring overlying a first planar surface of the second sealing ring, each piston sealing ring having an overlapped cut with generally circumferentially extending inner and outer overlapping portions which contact each other to form a continuous seal extending from the first planar surface to the second planar surface of the piston sealing ring and separating an inner ring gap and an outer ring gap, the overlapped cut of the first piston sealing ring being circumferentially offset from the overlapped cut of the second piston sealing ring whereby the periphery of the outer ring gap of the first piston sealing ring at its second planar surface is sealed by the first planar surface of the second piston sealing ring and the periphery of the outer ring gap of the second piston sealing ring at its first planar surface is sealed by the second planar surface of the first piston sealing ring.