Seal for a joint or juncture – Seal between fixed parts or static contact against... – Contact seal for a pipe – conduit – or cable
Reexamination Certificate
2000-05-16
2002-03-26
Sandy, Robert J. (Department: 3626)
Seal for a joint or juncture
Seal between fixed parts or static contact against...
Contact seal for a pipe, conduit, or cable
C277S616000, C277S626000, C277S644000
Reexamination Certificate
active
06361052
ABSTRACT:
BACKGROUND OF THE INVENTION
It is known in the art to contain fluids under high pressure in conduits and vessels formed by mating two or more parts or to prevent such fluids from entering the conduits or vessels from outside. It is further known that in order to prevent leakage of such fluid at the mating surfaces of the parts, a deformable sealing element made of an elastomeric material can be provided to fill the space through which leakage might otherwise occur.
Deformable sealing elements, when subjected to high pressure differentials, tend to extrude through a clearance between the mating surfaces thereby compromising the integrity of the seal. Prior art solutions for the problem of seal extrusion have included the use of additional sealing components in the form of back-up washers. O-ring's have also been disposed in close-tolerance rectangular grooves to alleviate the problem of seal extrusion.
In addition to O-rings, prior art designs utilized in sealing applications have included lip seals and gaskets. However, all of these approaches have shortcomings. An O-ring profile, although simple and versatile, is impractical for sealing extensive irregular areas. The preparation of an O-ring that will remain in place when subjected to large pressure differentials is difficult as is its installation which is likely to be done incorrectly. Moreover, a close-tolerance rectangular groove is difficult to maintain, requires large amounts of space in the carrier, and concentrates stresses at corners of the groove. An O-ring seal will be subject to extrusion where an excessive gap exists between mating surfaces.
A sometimes more effective solution than those discussed above is sometimes provided by a lip seal profile. A lip seal profile, i.e., one which employs a flap, is capable of developing good contact under stress when mechanically loaded. However, a lip seal is also not without substantial limitations.
A lip seal becomes energized by the fluid pressure it is designed to contain rather than by mechanical loading. As the fluid pressure increases, a greater force is applied from within the hollow of the lip-seal against its flaps thereby increasing the seal's contact stress. As the fluid pressure increases so does the contact stress.
A lip seal is limited to effective sealing in only one direction. Additionally, the manufacture of lip seal elements which require molding of “flap” geometry undercuts to suit each specific application can be costly. Furthermore, a lip seal can be damaged if a small portion is mechanically loaded, for a period of time, prior to its installation in its intended environment. Such damage typically occurs during manufacturing, shipping, and/or storage.
Gaskets, as well as other designs known to the art, are susceptible to damage by excessive mechanical loading. The polymeric material of a such a seal is typically incompressible. If the seal is subjected to excessive compressive forces in the application, the seal is likely to mechanically fracture since it is forced to extrude under the compressive load. Such damage often occurs during installation in the application.
Finally, in the presence of a pressure differential, prior art profiles are subject to continuous and/or intermittent strain relaxation, (“creep”, “extrusion”) in the absence of back-up washers or a close tolerance groove to provide lateral restraint to the sealing element. However, the use of a back-up washer introduces an additional component with its attendant cost and the increased complexity of the interaction between the sealing element and washer. A rectangular groove, normally required to support a back-up structure, does not fully protect the seal from extrusion. Irregularities in the clearance between the mating surface and groove present areas where the seal can extrude. Gaskets by their design are laterally unrestrained seal systems and subject to creep.
SUMMARY OF THE INVENTION
The aforesaid problems of the prior art are overcome by the present invention which provides for a novel sealing element and its use to prevent the flow of fluid under high pressure differentials between the mating surfaces by providing a sealing element formed from a resilient polymeric material. The sealing element has a head with a cross section of generally semicircular circumference and a base to which the head is integrally connected. The base has integral wings extending outwardly in mutually opposite directions. The head of the sealing element is deformed by mechanical pressure applied against it by the mating element thereby increasing its contact surface area with the mating element for preventing passage of fluid between the sealing element and the mating surface. Pressure exerted by the fluid urges the deformed head against the wings for preventing passage of fluid between the sealing element and the carrier.
Fluid is prevented from traversing an interface between a surface of the carrier element and a surface of a the mating element by forming a concave groove in the carrier element, inserting within said groove, an elastomeric sealing element as described above, and placing the mating element surface in engagement with the carrier surface and with the convex outer surface of the head of the sealing element whereby said sealing element is deformed to assume a profile which presents an impenetrable barrier to the flow of fluid.
An object of the invention is to isolate or seal extensive irregular areas between two stationary mating surfaces as well as between symmetrical areas of mating surfaces.
Another object of the invention is to contain fluids, i.e., gas or liquids, within a vessel or conduit or exclude them from a vessel or conduit in the presence of a large pressure differential between the interior and exterior of the vessel or conduit.
Still another object of the invention is to effect a seal between surfaces having available areas which are very small.
REFERENCES:
patent: 3166332 (1965-01-01), Olson
patent: 4368894 (1983-01-01), Parmann
patent: 5074711 (1991-12-01), Glang et al.
patent: 5228702 (1993-07-01), Browne et al.
Levine & Mandelbaum
Sandy Robert J.
Schwing Karlena D.
Seals Eastern Inc.
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