Double life shaft seal

Claim 2

A fluid seal comprising: a casing member; a flexible sealing element connected to said casing member, said sealing element having a pair of annular sealing surfaces facing a surface to be sealed, one of the sealing surfaces adapted to normally operatively engage said surface to be sealed; shiftable means operable at a first position for biasing said one of said sealing surfaces into engagement with said surface to be sealed and operable at a second position for biasing the other of said sealing surfaces into engagement with said surface to be sealed; means associated with said shiftable means for holding the latter at said first position until predetermined wearing of said one of said sealing surfaces and thereafter releasing said shiftable means; and means for moving said shiftable means to said second position after said releasing whereby said other of said sealing surfaces is operativelY biased into engagement with said surface to be sealed.

Claim 3

A fluid seal for sealing the space between relatively rotating members comprising: a casing member mounted on one of the members; a flexible sealing element connected to said casing member; a pair of annular sealing lips projecting toward the other of said members, one of the lips adapted to normally engage said other of said members with the other of said lips being initially spaced therefrom; first spring means slidably retained on said sealing element for selectively biasing said lips; a shiftable element on said sealing element engaging said first spring means, said shiftable element being movable from a normal first position wherein said first spring means operatively biases one of said lips to a second position wherein said first spring means operatively biases said other of said lips; stop means associated with the shiftable element for holding the latter at said first position until predetermined wearing of said one of said lips; and second spring means between said casing member and said shiftable member for shifting the latter to said second position after said predetermined wearing whereby said other of said lips engages said other of said members to provide a second seal life.

Claim 4

A fluid seal for sealing the space between relatively rotating members comprising: a casing member mounted on one of the members; a flexible sealing element connected to said casing member; a pair of annular sealing lips projecting toward the other of said members, one of the lips adapted to normally engage said other of said members with the other of said lips being initially spaced therefrom; first spring means slidably retained on said sealing element for selectively biasing said lips; a shiftable element on said sealing element engaging said first spring means, said shiftable element being movable from a normal first position wherein said first spring means operatively biases one of said lips to a second position wherein said first spring means operatively biases said other of said lips; stop means associated with the shiftable element for holding the latter at said first position until predetermined wearing of said one of said lips; and second spring means between said casing member and said shiftable member for shifting the latter to said second position after said predetermined wearing whereby said other of said lips engages said other of said members to provide a second seal life.

Claim 5

A dual life shaft seal for sealing the space between a relatively rotating shaft and housing comprising: an annular case mounted on said housing; a sealing annulus formed of a flexible material connected to said case, said sealing annulus including a cylindrical sleeve spaced from the shaft; first and second seal lips formed on the inner surface of and axially spaced along said sleeve, said first and second seal lips having first and second sealing surfaces individually defined by radially inwardly converging frustoconical surfaces, both of said sealing surfaces adapted to engage the shaft with said first sealing surface normally engaging the shaft and said second sealing surface being initially radially spaced therefrom; a tensioned helical spring slidably retained on the outer surface of said sleeve for radially inwardly biasing either of said lips; a split annular contractable ring slidably received over said outer surface of said sleeve and engaging said helical spring; an inwardly projecting tab on said case normally locating said ring and said helical spring at a first position wherein said spring radially inwardly biases said first seal lip thereby providing a first service life for said seal, said ring contracting in diameter upon wearing of said first seal lip and disengaging from said tab after predetermined lip wear; spring biasing means acting on said ring and shifting said ring and said spring after said predetermined lip wear to a second position wherein said helical spring radially inwardly biases said second lip against the shaft to provide a second service life for said seal.

Claim 6

A dual life shaft seal for sealing the space between a relatively rotating shaft and housing comprising: an annular case mounted on said housing; a sealing annulus formed of a flexible material connected to said case, said sealing annulus including a cylindrical sleeve spaced from the shaft; first and second seal lips formed on the inner surface of and axially spaced along said sleeve, said first and second seal lips having first and second sealing surfaces individually defined by radially inwardly converging frustoconical surfaces, both of said sealing surfaces adapted to engage the shaft with said first sealing surface normally engaging the shaft and said second sealing surface being initially radially spaced therefrom; a tensioned helical spring slidably retained on the outer surface of said sleeve for radially inwardly biasing either of said lips; a split annular contractable ring slidably received over said outer surface of said sleeve and engaging said helical spring; an inwardly projecting tab on said case normally locating said ring and said helical spring at a first position wherein said spring radially inwardly biases said first seal lip thereby providing a first service life for said seal, said ring contracting in diameter upon wearing of said first seal lip and disengaging from said tab after predetermined lip wear; spring biasing means acting on said ring and shifting said ring and said spring after said predetermined lip wear to a second position wherein said helical spring radially inwardly biases said second lip against the shaft to provide a second service life for said seal.