MECHANICAL SEAL WITH A BALANCE SHIFT MECHANISM

摘要

An O-ring balance shift mechanism is provided in a dry lift-off face mechanical seal to maintain necessary hydraulic closing forces on the seal faces when pressurized from either the inside or outside diameter of the balance shift mechanism to shift the diameter balance of the seal rings radially under reversed pressure conditions. This mechanism includes a shift ring with two O-rings wherein the shift ring is H-shaped or S-shaped in two alternate embodiments. The O-rings are radially spaced from each other and move axially with the shift ring during reverse pressure conditions.

主权项

1. In a mechanical seal for sealing an annular sealing space between a housing and an axially-elongated rotatable shaft, said mechanical seal including a plurality of annular seal components surrounding said shaft wherein said seal components comprise at least a non-rotatable first seal ring, a first support member for said seal ring, and a rotatable second seal ring non-rotatably mounted on said shaft so as to rotate therewith, said first and second seal rings having opposing seal faces which sealingly separate a first chamber with a first pressurized fluid at a first fluid pressure from a second chamber with a second pressurized fluid at a second fluid pressure different than said first fluid pressure, comprising the improvement wherein:
a secondary seal is provided between a first said seal component and a second said seal component to prevent leakage between said first and second chambers, said first and second seal components having respective first and channel portions wherein said first and second channel portions open toward each other and together define an annular channel formed radially and axially between said first and second seal components; and said secondary seal comprising a balance shift mechanism disposed within said annular channel which comprises a shift ring which is received in said annular channel and has opposite ends respectively exposed to said first and second pressurized fluids which move said shift ring between first and second operative positions, said shift ring further including inner and outer gaskets which face in opposite inward and outward radial directions to sealingly contact said first and second seal components, said shift ring being movable by a relative pressure difference between said first and second fluid pressures so as to be in said first operative position in contact with said first seal component when said first fluid pressure is higher than said second fluid pressure, and be in said second operative position in contact with said second seal component when said second fluid pressure is higher than said first fluid pressure.