Pressure responsive sealing means

Claim 1

A sealing device operable without lubrication located between two relatively movable members such as a piston and a cylinder moving along a motion path to separate two regions containing fluids with substantially different higher and lower fluid pressure magnitudes, comprising in combination, sealing structure presenting a first primary sealing surface comprising a self-lubricating plastic material in contact with the surface of one of said movable members to move therealong over said motion path and presenting a second substantially stationary sealing plastic surface substantially normally disposed to said first sealing surface, a groove in one said member receiving said sealing structure, said second sealing surface being located substantially midway of said first sealing surface, at least one resilient member holding at least said primary sealing surface biased lightly toward contact with its mating surface, and pressure conduit means conveying said fluid of higher pressure against the sealing structure to force both said first and second sealing surfaces together with a force substantially exceeding that of said resilient member and proportional to the differential pressure of the two separated fluids.