Piston ring construction

Claim 1

In a cylinder having a circular cylindrical wall of predetermined diameter and a generally circular cylindrical member of lesser maximum diameter disposed in the cylinder, a seal arrangement for maintaining a fluidtight seal between the member and the wall against fluid under pressure up to in the neighborhood of 15,000 p.s.i. in the cylinder on one side of the seal arrangement, comprising: a. an annular groove in said member having a generally rectangular cross section with a right cylindrical base and planar upper and lower surfaces spaced a first distance apart, b. said base and upper and lower surfaces having the relatively rough character provided by machining without finish grinding, c. a seal assembly seated in said groove, d. said seal assembly including a unitary sealing ring fabricated of a tough plastic having properties generally characteristic of the polymers of tetrafluoroethylene, e. said sealing ring having an L-shaped cross-sectional configuration, a circular cylindrical inner face of said tough plastic in interference fit with said base of said groove along the entire height of said inner face, and a generally circular cylindrical outer face of said tough plastic in intimate engagement with the wall, f. said height normally being less than said first distance whereby a gap is left between said sealing ring and said upper surface on the one side of said sealing arrangement, g. and a metal split backup ring opposite said plastic ring from the one side seated in the recess defined by the L-shaped cross-sectional configuration of the said sealing ring whereby a generally planar tough plastic face (portion) of said sealing ring and a generally planar face of said backup ring intimately engage said relatively rough planar lower surface of said groove.