Seal for a joint or juncture – Seal between relatively movable parts – Relatively rotatable radially extending sealing face member
Patent
1989-04-07
1991-01-22
Cuchlinski, Jr., William A.
Seal for a joint or juncture
Seal between relatively movable parts
Relatively rotatable radially extending sealing face member
277134, F16J 1532
Patent
active
049865536
DESCRIPTION:
BRIEF SUMMARY
This invention relates to shaft seals, also known as oil seals, for sealing against fluid leakage between shafts, or similar relatively rotatable mechanical members, and their housings.
A widely-used construction of such a seal comprises a rigid case ring, usually an L-section ring of metal or, more recently, a phenolic resin or other rigid plastics material, and a sealing ring secured to the case ring. For a so-called internal seal, the case ring fits, statically sealed, in a housing and the sealing ring bears peripherally, as a wiping seal, against the shaft. For an external seal, only occasionally required, the case ring fits on the shaft and the sealing ring bears against a surrounding cylindrical surface of a housing.
The sealing ring material is commonly an elastomer, such as an oil-resistant synthetic rubber, but for some purposes, particularly for resistance to corrosive fluids, fluorocarbon resins are used, especially polytetrafluoroethylene (PTFE).
PTFE cannot be moulded satisfactorily by simple heat and pressure in the same way as a rubber type elastomer and sealing rings of such material are usually made as discs or washers cut from the sintered resin and pressed and set or otherwise formed to a belled or like frusto-conical shape, for example.
Difficulty is encountered in strongly securing a PTFE sealing ring fluid-right to a rigid case ring. Probably the most widely used construction is one in which a peripheral margin of the sealing ring is clinched in the case ring by a rigid holding ring, with or without a rubber or other deformable packing ring. EP, A, 0122319 (FREUDENBERG) discloses bonding a PTFE lip ring 2 to a stiffening ring 1 by an intermediate layer 6 of rubber-elastic material. FR, A, 2239626 (FREUDENBERG) discloses a fibrous sealing ring 3 having an oil side impermeable layer 5.
It is an object of the present invention to provide a composite shaft seal advantageously combining fluorocarbon and elastomer in a sealing ring.
According to the present invention, a shaft seal comprises a rigid case ring and a resiliently deformable sealing ring secured to the case ring, the sealing ring having two annular components, one component being an annulus of fluorocarbon resin material and the other component being an elastomeric material which extends in a bonded layer over the air side face of the fluorocarbon component to a sealing periphery thereof and forms the wiping seal.
Thus, the elastomeric component can form the shaft seal with the fluorocarbon component resiliently supporting the bonded layer of elastomer and, being on the oil side thereof, additionally providing a corrosion resistance facing therefor; at the same time, the elastomer component can securely bond the fluorocarbon component to the case ring.
In shaft seals, it is now common to provide, on the air side of a seal lip, i.e. facing away from the sealed fluid at the oil side, helical or like ribs or grooves forming a hydrodynamic configuration designed to promote, in use, a positive sealing action by feedback of fluid tending to leak past the sealing lip.
It has not been found satisfactory to mould a hydrodynamic configuration on a PTFE shaft sealing lip and such a configuration is usually formed by coining the resin under high mechanical pressure.
The present invention additionally provides a shaft seal with a hydrodynamic configuration by using technology well-proved from established moulding of elastomeric shaft seals.
According to an embodiment of the present invention, the bonded layer of elastomer is moulded into a hydrodynamic, positive sealing action, configuration over the air side face of the fluorocarbon component.
The invention thus enables a shaft seal to be provided with a PTFE, or like, sealing ring to suit operating requirements and also to have an accurately defined hydrodynamic configuration using the same elastomer moulding technology as is used for securing the PTFE ring in its case.
Other features of the invention are set out in the claims and described with reference, by way of example, to the accompa
REFERENCES:
patent: 3549445 (1964-10-01), McMahon
patent: 3938813 (1976-02-01), Forch
patent: 4194748 (1980-03-01), Forch et al.
patent: 4513976 (1985-04-01), Bentley et al.
patent: 4616836 (1986-10-01), Drygalski et al.
International Automotive Engineering Congress, Detroit, Mich, Jan. 8-12, 1973, SAE, Inc., S. A. Sekulich: "TFE(Teflon) Radial Lip Seals".
Holloran Robert
Lidgate Brian
Preston Stuart
Cuchlinski Jr. William A.
DePumpo Daniel G.
George Angus & Company Limited
Hinds William R.
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