Controlled clearance seal

Claim 1

A controlled clearance seal for use on a shaft rotatably supported in a housing to seal high pressure hydraulic fluid in a housing having a sealing face adjacent the shaft and symmetrical with respect to the center line of the shaft, said seal comprising a generally annular body formed of a high strength material having a coefficient of expansion slightly greater than the coefficient of expansion of said shaft, said body having a sealing face engageable with said sealing face on said housing, said body having a flange portion projecting axially away from said sealing face on said body with said flange portion having an inner circumferential surface engageable with said shaft with said inner surface having an inside diameter slightly larger than the diameter of said shaft thereby permitting said body to rotate with said shaft until high pressure hydraulic fluid presses said sealing face on said body against said sealing face on the housing to frictionally retain the seal body in a fixed position relative to said housing and causing said flange to be compressed radially to decrease clearance between said body and said shaft causing said body to rub said shaft with resulting friction generating heat which causes expansion of said body and said shaft, whereupon said body expands at a greater rate than said shaft permitting the clearance between said body and said shaft to increase until rubbing of said shaft by said body ceases, thus stopping the heat generation whereupon said body instantly contracts due to cooling and pressure, until said body and said shaft again come into rubbing contact, with such cycle as just described involving rubbing, heating, expansion, cooling, contraction, and rubbing, being repeated several times per second resulting in a dynamic balance of said forces thereby establishing a virtually constant controlled clearance between said body and said shaft resulting in an extremely low leakage rate over a wide range of temperatures and pressures with such operational efficiency of said seal being a direct result of the combination of cross-section design and high strength material selection.