Seal for a joint or juncture – Seal between fixed parts or static contact against... – Contact seal between parts of internal combustion engine
Reexamination Certificate
1999-02-12
2001-04-03
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
C277S595000, C277S598000, C029S888300, C029SDIG003
Reexamination Certificate
active
06209883
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a gasket and more particularly to a metal cylinder head gasket used to seal the joint surfaces of a cylinder head and a cylinder block of an engine whereby the gasket has a primary stopper seal that is formed by an extrusion process in combination with a folding operation.
BACKGROUND OF THE INVENTION
It is known to provide metallic gaskets for sealing opposed joint surfaces of a cylinder head and a cylinder block of an engine. Typical gaskets are provided with apertures which cooperate with the combustion chambers, water passages and oil passages in the engine. The apertures are further provided with some kind of sealing element.
Known sealing elements have included a separate sealing layer for the gasket, a welded on shim, or a thermal spray deposit applied to the outer surface of the gasket. Sealing elements of these types involve more materials, more assembly time, and therefore disadvantageously increase production costs.
Other known metallic gaskets include a metal plate having a substantially uniform thickness that has a portion near the apertures folded over onto the metal plate to create an increased thickness sealing surface. Such sealing elements often exhibit performance problems as the fold areas are prone to cracking due to the thickness of the metal plate.
To overcome such problems, one known gasket includes a metal plate that is provided with stepped portions such that the thickness of the plate is varied. The metal plate is folded at the portion of the plate that has a reduced cross-sectional thickness than the remainder of the plate. However, providing the stepped portions on the plate involves an extra machining step, as well as a specialized tooling set up to achieve precise tolerances, thereby serving to drive production costs upward.
Other known gaskets that have folded sealing elements utilize a metal plate with a substantially uniform thickness, but which further includes the addition of annular grooves in a surface of the metal plate. The grooves are positioned at the fold line and at that part at which the free ends of the folded portions are positioned such that the folded free ends do not come into contact with the metal plate. Gaskets of this kind also involve a separate expensive machining step to form the annular rings, thus increasing production costs.
Another known gasket only incorporates sealing beads as the sealing element on the perimeter of the gasket aperture. Sealing beads alone are unsatisfactory because significant compression is necessary to cause the beads to bear against the flanges of the cylinder head and cylinder block to create an adequate seal.
Therefore, there exists a need for a gasket having a minimum number of parts that can be manufactured cost-efficiently without sacrificing sealing effectiveness.
SUMMARY OF THE INVENTION
The present invention is directed to a metal gasket having a sealing element positioned around apertures in the gasket, such as a combustion opening, whereby the sealing element is formed by an extrusion and ironing process in combination with a folding operation.
A first embodiment of the metallic gasket of the present invention includes a plate, preferably constructed of stainless steel for durability, having a body portion and a flange portion which encircles the perimeter of an aperture formed in the gasket. The body portion has a substantially uniform thickness. The flange portion also has a substantially uniform thickness, however, the thickness of the flange portion is less than the thickness of the body portion. The thickness of the flange portion is achieved by extruding and ironing the flange portion of the metal plate to the desired thickness without requiring specialized tooling for precise machining operations.
After extruding, the flange portion is folded forward onto the body portion in facing relationship, creating a stopper seal as a primary seal at an edge of the gasket aperture. Because of the reduced thickness of the flange portions, the seal operating thickness is advantageously only slightly larger than the plate body thickness. An optional embossment spaced radially and outwardly from the stopper seal could also be provided to serve as a secondary sealing element, thereby increasing the durability of the combustion seal area.
In a second embodiment, the metallic gasket of the present invention includes a plate having a body portion and an offset portion which encircles the perimeter of an aperture formed in the gasket. The offset portion includes a tapered thickness portion. A tapered punch cooperates with a die having inclined walls to iron the offset portion, including the tapered portion, to create a flange portion having a thickness less than the thickness of the body portion. As in the first embodiment, the flange portion is then folded forward onto the body portion in facing relationship, creating a stopper seal as a primary seal at an edge of the gasket aperture.
The gasket of the present invention has the advantage of easily controlling seal operating thickness by controlling the flange thickness without having to perform time consuming tooling set-up to achieve precise tolerances, thereby reducing production costs. By simply varying the flange thickness, the seal operating thickness can be cost-effectively varied for a wide range of gasket operating conditions.
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Kashmerick Gerald Emil
Plunkett Thomas P.
Dana Corporation
Knight Anthony
Pickard Alison K.
Rader & Fishman & Grauer, PLLC
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