Seal for a joint or juncture – Seal between fixed parts or static contact against... – Contact seal between parts of internal combustion engine
Reexamination Certificate
1999-03-31
2001-05-29
Knight, Anthony (Department: 3626)
Seal for a joint or juncture
Seal between fixed parts or static contact against...
Contact seal between parts of internal combustion engine
C277S600000
Reexamination Certificate
active
06237919
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to the an engine cylinder head gasket having a high load bearing UV coating. More particularly, the invention relates to a coating for use on a cylinder head gasket.
BACKGROUND OF THE INVENTION
Gaskets are often used as a seal between mating mechanical components. One common application involves gasket placement between the engine block and cylinder head of an internal combustion engine. The engine block and cylinder head are bolted together and the gasket relies on the force of the bolted connection to seal the various openings between the two mating components. In particular, cylinder head gaskets typically extend around cylinder bores to provide a combustion seal, maintaining the high temperature gases of combustion within the cylinder bores. Simultaneously, the gaskets also seal fluid flow openings such as coolant and oil openings to prevent undesirable mixing.
It is typical for a cylinder head gasket to include a main gasket body with a cylinder bore opening, the periphery of which is surrounded by a metallic generally U-shaped flange. The flange engages both the upper face and the lower face of the main gasket body. The flange provides improved protection to the gasket body from the high temperature gases of combustion and serves to dissipate the heat of combustion into the gasket body and away from the cylinder bore opening.
Load bearing coatings have been incorporated onto surfaces of the cylinder head gasket to provide static sealing of joints such as those for which cylinder head gaskets are used. These coatings often contain silicone and normally contain solvents, and require heat to cure. In such a case, the increased sealing property of the silicone is attained at the expense of a decreased load bearing property. Furthermore, the weakness of the coating results in the inability of the gasket to maintain its mechanical structure once the pressure of a load is removed from the gasket. As a result, the gasket must often be replaced when the pressure of a load is removed from the gasket during maintenance or repair of an engine using the gasket.
Accordingly, it is desirable to provide a coating having a high sealing property, increased strength and durability, a high cross-link density when cured, and a good release property. It is also desirable that the coating be readily available for use after long periods of storage. It is further desirable to provide a cylinder head gasket that has a high load bearing characteristic at both high and low temperatures, and adequately seals the joints to which the gasket is mated.
SUMMARY OF THE INVENTION
A cylinder head gasket according to the present invention includes a main gasket body having a multi-faced surface, and a coating about the surface, where the coating contains a silicone system having a vinyl ether incorporated therein. The gasket may also include a fluid flow opening defined by a periphery of the main gasket body, and a metallic generally U-shaped flange with an outer surface, where the flange has opposing legs separated by a central section that is disposed within the fluid flow opening. The upper leg engages the upper face and the lower leg engages the lower face with the central section extending radially into the opening away from the periphery. When the flange is incorporated with the gasket, the coating covers the outer surface of the U-shaped flange. In a preferred embodiment of the invention, the coating entirely covers both the surface of the main gasket body and the outer surface of the U-shaped flange.
The coating is preferably an ultraviolet (“UV”) curable coating. Furthermore the vinyl ether incorporated in the silicone system is preferably cyclohexanedimethanol divinyl ether. When cured, the coating has an effective thickness of at least 0.0002 inches (0.0051 mm). In a preferred embodiment, the thickness after curing is in a range of up to 0.0015 inches (0.0381 mm). However, the range can be extended to a higher upper limit when the surface of the head gasket is rough or when a component that mates with the gasket is rough.
The present invention also includes a method of coating a substrate of a load bearing component of an engine, which comprises the steps of combining a silicone copolymer, a vinyl ether compound, a photoinitiator, and a UV-curable polymer to form the coating; applying the coating to the substrate; and curing the coating at an ambient temperature.
The applying step may include performing a coating application such as a curtain application, a silk screen application, or reverse roll coating. The curing step includes exposing the coated substrate to UV radiation. As mentioned above, the vinyl ether is preferably cyclohexanedimethanol divinyl ether. The photoinitiator, is preferably in a range from about 2 to about 4 parts by weight, the UV-curable polymer is preferably in a range from about 40 to about 80 parts by weight, the silicone copolymer is preferably in a range from about 10 to about 50 parts by weight, and the vinyl ether is preferably in a range from greater than zero to about fifteen parts by weight.
One advantage of the coating of the present invention is that it consists completely of reactive components prior to curing. Accordingly, no solvents need be present in the coating prior to curing, and heat need not be applied to cure the coating. The inventive coating has high sealing characteristics and a high cross-link density when cured. Moreover, the coating has a high load bearing characteristic at both ambient and elevated engine operational temperatures. Furthermore, the coating has a very good release property following continuous and heavy load subjection on a substrate to which the coating is applied. Finally, the coating has excellent pot life, resulting in the ability to be stored in an uncured state for long periods of time prior to use.
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Boldt Brent
Grant-Acquah Frank C.
Shah Kanu G.
Dana Corporation
Knight Anthony
Pickard Alison K.
Rader & Fishman & Grauer, PLLC
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