Piston assembly with compression and guiding rings

Claim 1

A piston assembly adapted for use in non-lubricated high-pressure compressors, comprising a piston having a plurality of identical peripheral trapezoidally shaped cross-section grooves therein with each groove having a uniform annular base, a dual ring assembly in each groove protruding from said piston surface so as to contact the cylinder walls of said compressors, thus avoiding direct contact of the piston with said cylinder walls consisting of a seal ring of rectangular-shaped cross-section and a guide ring of largely trapezoidal cross-section with said guide ring seated behind the seal ring in a direction away from the compression end, said seal ring and guide ring in each groove having abutting planar surfaces, said guide ring having a surface opposite the one abutting with the seal ring which is at an acute angle relative to the base thereof to form the said trapezoidal cross-section and at least partially conical in shape, each peripheral groove in said piston having a corresponding wall defining an acute angle with the base of the groove to define an angularly shaped groove enabling said guide ring to hook into same and in abutment therewith, said guide ring being made from carbon-graphite material providing higher resistance to shape deformation than the seal ring said seal ring being made from polytetrafluoroethyle and both rings being more abradable than the material of the piston.