Pressure balanced reciprocating shaft seal

Claim 1

In combination with a pair of relatively reciprocable elements comprising a housing and a shaft carried therein, a shaft seal between said housing and said shaft and separating the interior of said housing into first and second chambers, said seal being adapted to substantially prevent fluid movement in one direction between said chambers but to permit fluid movement in the opposite direction between said chambers, said seal comprising a sleeve member having an elastically deformable generally cylindrical portion closely surrounding said shaft and terminating in a sharp edge engageable with said shaft, said cylindrical portion being exposed to fluid pressure in one of said chambers whereby said edge is urged into such engagement, a closing ring having a conical surface disposed in engagement with the end of said sleeve member adjacent said sharp edge and responsive to an axial force urging said ring and sleeve members together to force said sharp edge inwardly against said shaft and preloading means acting between said housing and one of said sleeve and closing ring members so as to axially urge together said sleeve and closing ring, said preloading means in combination with said one of said sleeve and closing ring members having a surface in said one chamber exposed to axially directed pressures which oppose the action of said preloading means, whereby an increase in pressure on said one chamber reduces the force by which said preloading means urge together said sleeve and closing ring so as to at least in part balance the increase in the engaging force caused by the action of said fluid pressure on said sleeve member cylindrical portion.