Seal for a joint or juncture – Seal between fixed parts or static contact against... – Contact seal between parts of internal combustion engine
Reexamination Certificate
1997-08-29
2001-06-19
Mah, Chuck Y. (Department: 3626)
Seal for a joint or juncture
Seal between fixed parts or static contact against...
Contact seal between parts of internal combustion engine
C277S627000, C277S652000
Reexamination Certificate
active
06247703
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
Performance characteristics required of many gaskets includes both compression failure resistance and sealing ability. Gaskets frequently must operate under pressures in the range of from about 3,000 to about 30,000 PSI (pounds per square inch). At the same time the gasketing is also required to provide a seal against fluids.
In some instances, in order to provide a good seal, gasketing is coated to get sealing ability. Fibrous gaskets or soft porous materials are types of gasketing which is given coatings since this gasketing is very porous and has problems in giving an adequate seal for use. Unfortunately, the coating used to give sealing ability penetrates the gasket, and reduces the ability of the gasket to withstand pressure. It would be beneficial to develop a gasket which delivers good sealing ability which, at the same time, is compression-failure resistant, especially if the gasket could operate at flange pressures in the range of from about 20 to about 30,000 PSI.
Gasketing which is presently known in the art includes gaskets described by U.S. Pat. No. 3,661,401 which requires that the gasketing be given a coating which covers the walls of the apertures in addition to the gasketing faces. Such gasketing, however, being completely coated, will perform poorly at such high pressures. This severely limits the field of use of the gaskets.
The present invention beneficially provides gaskets which have an adequate sealing ability and are compression-failure resistant. Gaskets which are capable of withstanding operating pressures of at least 3,000 PSI are provided. Furthermore, gaskets which operate well in the range of from about 20 to about 30,000 PSI are provided; the present gaskets remarkably being capable of sealing at both high and low flange pressures.
SUMMARY OF THE INVENTION
In accordance with the present invention, a soft gasket material has two opposed surfaces (faces), said gasket having an edge perpendicular to the facial surfaces. The edge has a surface which is given a coating. Where the edge is on an aperture, the coating on the edge of the aperture gives the gasket a primary seal against fluid leaks that would come from the aperture across the porous edge of the soft gasket material and into the gasket. A coating on a perimeter edge gives only a secondary seal.
The opposed, facial surfaces, however, have only a limited coating in order to preserve compression failure resistance. The more coating that is given to the face of the gasket the more loss of compression failure resistance there is. Having a portion of the gasket surface uncoated provides better compression failure resistance than the gasket would have with a sealing coating on at least some of the uncoated surface. Release coatings are permitted and optionally, in any given application the gasket can be given a release coating which does not cause compression failure. Preferably, no coating for sealing ability can be made on gasketing which would cover more than about 50% of either or both faces. More preferably, for more compression failure resistance, no more than about 30% of both faces are coated for sealing ability. Most preferably, in fact, the opposed, facial surfaces are not substantially coated with sealing coatings. Having substantially no coating on either face of the gasket will give the gasket a better compression failure resistance than the gasket would have if the same gasket did have a coating on up to about 30% of both faces or even on some portion of at least one face.
The coating permitted on the opposed, facial surfaces (the face) is limited to 1) a sealing coating on one or both gasket faces while leaving uncoated portions on one or both gasket faces, the uncoated portions of the gasket being present in an amount effective to give the gasket better compression failure resistance than it would have if at least a portion of the uncoated surface was coated, and/or 2) release coatings which do not substantially affect compression-failure resistance and do not substantially penetrate the gasket.
Suitably, the coating on the edge covers all of the portions of the edge which must be coated in order to give the gasket a good sealing ability. Preferably, however, the entire edge is coated. The coating of the entire edge will allow the gasket to provide a better seal. Acceptable embodiments include, however, instances where the coating covers major portions of the edge. The edge can, thus, be coated in an effective amount to achieve a substantial sealing of the gasket along the edge of the aperture. The edge, for example, can be coated up to about 75% of the aperture's edge. Such embodiments can be used for good sealing ability, where the very best sealing ability obtained from coating the entire edge of the gasket does not have to be used. If, for example, a bolt area was near the aperture, the high pressure near the bolt may decrease the need for a full coating of the edge. A bolt area is an area near or under the bolt where higher pressure is put on the gasket than on areas further away from the bolt.
In another embodiment the edge of the gasket sheet material contains pores into which the coating material on the edge has penetrated. This helps to seal off pores and gives the gasket sheet a better sealing ability.
A wide edge-coating on a gasket sheet edge which covers the edge from corner to corner and extends beyond the corner, protruding past the corner plane (past the corner) in a direction perpendicular to the facial plane, will give the gasket a better sealing ability, especially since it can seal against two types of fluid flow; both through the gasket and across the gasket face. This is particularly true for an edge which has been cut in the gasket. The cut edge will have more pores than another surface which is not cut even in porous and compressible gaskets. Coating the edge so that the coating penetrates or closes off the pores will be effective to seal off the pores to fluid which could seep through the gasket.
Where a gasket has both the aperture's edge coated and a coating on a portion of at least one face which abuts an aperture and forms a border around the aperture, the edge coat is arbitrarily designated coating A (in this description) while the coating on the face abutting the aperture is designated coating B; a coating on the edge which is around the outside (periphery) of the gasket material is coating C.
Different coating materials may be used to form coating A and B, although it is also permissible to coat the different areas with the same coating material.
As more coating for sealing ability is put on the gasket faces, the performance of the gasket in response to higher pressures will deteriorate, even if the coating on the face is limited to a strip of coating abutting the aperture's coated edge on at least one side of the gasket. For this reason, therefore, it is preferred that coating B, abutting the aperture's coated edge should be limited in width, so that it covers only a limited portion of the gasket face(s). Preferably, the coating (coating B) on at least one gasket face, abutting the aperture's coated edge can be up to about 1.5 centimeters wide on the face. Preferably, such coating strips, on the face of the gasket and abutting the aperture, can cover up to about 50% of one or both faces.
As the data of Example 8 herein demonstrates, for preferred embodiments it can also be important to limit the thickness of the coating on each gasket face. The thicker the coating on the face of the gasket the lower the pressure at which compression failure of the gasket occurs. Thus, coatings for sealing which are put on the gasket face are preferred to be a maximum of about 11 mils thick.
REFERENCES:
patent: 1772173 (1930-08-01), Yates
patent: 2070918 (1937-02-01), Peterson
patent: 2289620 (1942-07-01), Bernstein
patent: 3302953 (1967-02-01), Glasgow
patent: 3355181 (1967-11-01), Olson
patent: 3655210 (1972-04-01), Farnam et al.
patent: 3661401 (1972-05-01), Farnam
patent: 3729205 (1973
Forry John S.
Lehr Brian C.
Interface Solutions, Inc.
Mah Chuck Y.
Patel Vishal
Womble Carlyle Sandridge & Rice
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