Seal for a joint or juncture – Seal between fixed parts or static contact against... – Contact seal between parts of internal combustion engine
Reexamination Certificate
1998-07-30
2001-06-19
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
C277S593000, C277S597000, C277S938000
Reexamination Certificate
active
06247704
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a gasket for an internal combustion engine and, in particular, to a gasket having outer facing layers on either side of a central core member. Each of the outer facing layers is attached to a respective outer core.
BACKGROUND OF THE INVENTION
Gaskets for use in internal combustion engines are known. One known gasket design has multiple layers of steel and are referred to as “MLS” gaskets. In MLS gaskets, at least two sheets of steel are stacked together. Typically, there are three sheets with one middle sheet and two outer sheets. The outer surfaces have an elastomeric coating to accommodate imperfections that might interfere with creating a fluid tight sealing surface. In MLS gaskets, it is known to provide a bead to help establish suitable sealing stress levels and achieve a tight seal. However, one drawback to MLS gaskets is the increased expense of providing a very smooth surface finish to the clamping members. A second drawback is the cost of the elastomeric coating to compensate for imperfections on mating surfaces, such as cylinder heads or blocks.
Another known type of gasket design has outer facing layers made from graphite which are connected to outer cores. The facing layers and outer cores are attached to a central shim. Graphite outer facing layers conform to imperfections in mating surfaces and have a certain degree of resilience or springiness. U.S. Pat. Nos. 5,468,003 and 5,362,074, commonly assigned to Dana Corporation, describe gaskets of this type and each of their disclosures are incorporated herein by reference.
However, outer facing layers with graphite are susceptible to a relaxation phenomenon which results in a decrease in bolt tension and a corresponding reduction in sealing stress. The reduction of sealing stress could lead to an increased possibility of gasket leakage.
SUMMARY OF THE INVENTION
The present invention is directed to a composite gasket for use in an internal combustion engine and includes a central metallic core member with an upper facing layer located above the central core member and a lower facing layer located below the central core member. In addition, an upper core is connected to the upper facing layer and is located between the upper facing layer and the central core member. Similarly, a lower core is connected to the lower facing layer and is located between the lower facing layer and the central core member. A hollow bead is formed in a predetermined location of the central core member to provide a resilient biasing force that improves sealing.
Optionally, but preferably, an elastomeric coating layer is positioned between the central core member and each of the upper and lower cores to seal between gasket layers and prevent combustion gases or fluids from escaping through the gasket.
In a preferred embodiment, the composite gasket has a central core member made from full hard or extra hard stainless steel because of its excellent high temperature spring properties and corrosion resistance. The upper and lower facing layers are preferably made from graphite to improve gasket conformability with respect to mating surface imperfections and minimize tension loss.
Further, the upper and lower cores are preferably perforated and have a plurality of tangs located on one surface thereof for positively retaining the upper and lower facing layers, respectively.
Therefore, the present invention provides upper and lower facing layers that are able to conform to surface anomalies on mating components and eliminate the cost and expense of achieving a controlled surface finish, as required for a MLS type gasket. The present invention further provides a resilient bead that continually biases the upper and lower facing layers into engagement with mating surfaces, offsetting the effects of the relaxation phenomenon associated with non-metallic facing layer materials.
REFERENCES:
patent: 4898396 (1990-02-01), Udagawa
patent: 4956226 (1990-09-01), Ashizawa et al.
patent: 5004650 (1991-04-01), Ashizawa et al.
patent: 5275139 (1994-01-01), Rosenquist
patent: 5277434 (1994-01-01), Kestly et al.
patent: 5362074 (1994-11-01), Gallo et al.
patent: 5468003 (1995-11-01), Staab et al.
patent: 5490681 (1996-02-01), Plunkett et al.
patent: 5551709 (1996-09-01), Plunkett
patent: 5893566 (1999-04-01), Miyaoh et al.
patent: 6003877 (1999-12-01), Martin et al.
Dana Corporation
Knight Anthony
Rader & Fishman & Grauer, PLLC
Schwing Karlena D.
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