Mechanical seal with a balance shift mechanism

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, said first and second fluid pressures acting on said seal components to define a balance diameter relative to said first and second seal faces, 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 axially by a relative difference between said first and second fluid pressures so as to be in said first operative position adjacent said first seal component when said first fluid pressure is higher than said second fluid pressure, and be in said second operative position adjacent said second seal component when said second fluid pressure is higher than said first fluid pressure, said outer gasket defining said balance diameter in a first radial position when said shift ring is in said first operative position, and said inner gasket defining said balance diameter in a second radial position when said shift ring is in said second operative position wherein said balance diameter is in said first radial position when said first fluid pressure is greater than said second fluid pressure and said balance diameter shifts radially to said second radial position when the relative pressure difference between said first and second fluid pressure reverses and said second fluid pressure becomes greater than said first fluid pressure.

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 a gland mountable to said housing, a first seal ring non-rotatably mounted on said gland, a shaft sleeve mountable to said shaft, and a second seal ring non-rotatably mounted on said shaft sleeve so as to rotate with said shaft, said first and second seal rings having opposing seal faces disposed in sealing relation with each other to define a sealing region extending radially along said seal faces, said sealing region radially separating 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 one of said seal components and a second one of said seal components to prevent leakage between said first and second chambers through a secondary flow path defined between said first and second seal components, said first and second seal components having respective first and channel portions which each opens radially and axially toward the other of said first and second seal components wherein said first and second channel portions 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 for preventing fluid leakage through said annular channel while defining a balance diameter of said seal faces, said balance shift mechanism comprising a shift ring which is received in said annular channel so as to be axially movable therein between first and second operative positions, said shift ring having opposite first and second end faces which face axially and are respectively exposed to said first and second pressurized fluids, said shift ring further including inner and outer gasket channels which face radially inwardly and radially outwardly wherein said balance shift mechanism comprises first and second gaskets received in said inner and outer gasket channels which sealingly contact said first and second seal components within said annular channel, said first end face of said shift ring being in contact with said first seal component when said first fluid pressure is higher than said second fluid pressure which moves said shift ring to said first operative position, and said second end face of said shift ring being in contact with said second seal component when said second fluid pressure is higher than said first fluid pressure which moves said shift ring to said second operative position.

In a mechanical seal for sealing an annular sealing space between a housing and an axially-elongate rotatable shaft, said mechanical seal including a plurality of annular seal components surrounding said shaft wherein said seal components comprise a gland mountable to said housing, a support member which is axially movable relative to said gland, a first seal ring non-rotatably mounted on said support member, and a second seal ring non-rotatably mounted on said shaft so as to rotate therewith, said support ring and said first seal ring being axially movable relative to said gland and being normally biased toward said second seal ring, said first and second seal rings having opposing seal faces disposed in sealing relation with each other to define a sealing region extending radially along said seal faces, said sealing region radially separating 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 said gland and said support member to prevent leakage therebetween, said gland and said support member having respective channel portions which each opens radially and axially toward the other to define an annular channel;
• and
• said secondary seal comprising a balance shift mechanism disposed within said annular channel for preventing fluid leakage through said annular channel while defining a balance diameter of said seal faces, said balance shift mechanism comprising a shift ring which is received in said annular channel so as to be axially movable therein between first and second operative positions, said shift ring further including inner and outer gasket channels which face radially inwardly and radially outwardly wherein said balance shift mechanism comprises first and second gaskets received in said inner and outer gasket channels which sealingly contact said support member and said support gland, said shift ring being in contact with said support member when said first fluid pressure is higher than said second fluid pressure which moves said shift ring to said first operative position, and said shift ring being in contact with said gland when said second fluid pressure is higher than said first fluid pressure which moves said shift ring to said second operative position;
• wherein said inner gasket defines a static seal and said outer gasket defines a dynamic seal with said gland so as to slide axially along said gland during axial movements of said support member and said first seal ring, and wherein after movement of said shift ring to said second operative position, said outer gasket defines a static seal and said inner gasket defines a dynamic seal with said support member so as to slide axially along said support member during axial movements of said support member and said first seal ring.

In a mechanical seal for sealing an annular sealing space between a housing and an axially-elongate rotatable shaft, said mechanical seal defining a sealing region radially separating 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 first and second seal components to prevent leakage between said first and second seal components, said first and second seal components having respective channel portions which each opens radially and axially toward the other to define an annular channel;
• and
• said secondary seal comprising a balance shift mechanism disposed within said annular channel for preventing fluid leakage through said annular channel while controlling a fluid pressure balance within said mechanical seal, said balance shift mechanism comprising a shift ring which is received in said annular channel so as to be axially movable therein between first and second operative positions, said shift ring further including inner and outer gasket channels which face radially inwardly and radially outwardly wherein said balance shift mechanism comprises first and second gaskets received in said inner and outer gasket channels which sealingly contact said first and second seal components, said shift ring being in contact with said first seal component when said first fluid pressure is higher than said second fluid pressure which moves said shift ring to said first operative position, and said shift ring being in contact with said second seal component when said second fluid pressure is higher than said first fluid pressure which moves said shift ring to said second operative position.