Seal for a joint or juncture – Seal between fixed parts or static contact against... – Contact seal between parts of internal combustion engine
Reexamination Certificate
1998-03-02
2001-08-28
Brittain, James R. (Department: 3626)
Seal for a joint or juncture
Seal between fixed parts or static contact against...
Contact seal between parts of internal combustion engine
C277S594000, C277S595000
Reexamination Certificate
active
06279916
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to flat gaskets, which for example can be used as cylinder head gaskets or exhaust gaskets.
BACKGROUND OF THE INVENTION
Flat gaskets must, on the one hand, adjust themselves to irregularities in the faces to be sealed (micro-sealing) and, on the other hand, absorb the preliminary tension imparted by the screw forces during continuous duty without further deformation.
To improve micro-sealing the flat gaskets can be provided with a soft top coating, which is made of soft metal or plastic. In order to attain an improved seal, the coating should firstly be soft, so that it adapts well to the irregularities of the mating faces to be sealed in a cold static state, even during installation. Secondly, the sealing effect should also continue to exist during subsequent operation over as long a time of use as possible. In the case of severe dynamically stressed gaskets, such as cylinder head gaskets or exhaust gaskets, which work at high temperatures and under severe pressure loading, there is a tendency for the soft coatings of blowing out, so that adequate sealing is no longer assured. Therefore, flat gaskets attaining a good seal under the said conditions were required.
SUMMARY OF THE INVENTION
It is an object of the invention, therefore, to provide flat gaskets, which, even upon installation, adapt themselves to the mating faces to be sealed and lead to a good micro-seal and which also do not lose their sealability in subsequent operation when subjected to high surface pressure and high temperature.
This object is achieved by the flat gasket according to claim
1
. Further embodiments of the flat gaskets according to the invention are described in claims
2
to
8
.
On the one hand the term “flat gasket” here includes single-piece as well as multi-piece gaskets, such as for example, composite metal gaskets and soft material gaskets having metal edging around the openings to be sealed. On the other hand the term relates to such flat gaskets, which elastically adapt to changing pressure loads during operation, as well as to gaskets made of pressure-resistant material, which under operating conditions are not deformable in thickness. Normally, the gaskets according to the invention are made of metal, for example, aluminium. However, they can also be made from heat-resistant plastic or similar materials.
The gaskets according to the invention are characterized in that they comprise one or several high pressure lines in the region of their main sealing faces, hereinafter denoted as sealing ridges. These sealing ridges are very small compared with the main sealing faces and form regions of greater surface pressure and easier deformability. Such construction of the flat gaskets leads to an improved seal, even during installation.
The invention is described hereinafter with reference to single-piece gaskets made of pressure-resistant, non-deformable material, without restricting the invention to such gaskets. The following description applies similarly for the other types of gaskets mentioned above.
The single-piece pressure-resistant gaskets referred to in the following have a relief-like surface configuration. In variance to other gaskets they are formed such that they are already adapted to suit the topography of the mating faces to be sealed even before being installed. Such a flat gasket in the installed state and under operating conditions is pressure resistant and cannot be deformed in the thickness.
The relief-like functional faces of these flat gaskets according to the invention comprise main sealing faces, which have the function of sealing and bearing load and serve to absorb preliminary tension forces, which arise due to the forces of the screws. They are thus both sealing faces and bearing faces at the same time. In the flat gaskets according to the invention these main sealing faces are designed in their width so that their surface pressure is relatively low. Within the main sealing faces are one or several embossed sealing ridges. These sealing ridges are very narrow compared with the width of the main sealing face, and they only project by just a small amount in height above the main sealing face. In the vicinity of these sealing ridges a region of greater surface pressure and easier deformability compared with the remaining portion of the functional faces results. Due to this easier deformability and greater surface pressure, an improved seal can be attained even during installation.
Sealability can be further increased by the application of a coat. By the configuration of the functional faces according to the invention it is possible to choose an essentially harder, more resistant coat for continuous duty, so that the gasket will attain a better sealability right from the start.
Firstly, the gasket according to the invention enables superior micro-sealing to be achieved even during installation. Secondly, the problem of blowing out of the coating can be avoided, so that even during continuous duty under high temperature and pressure loading an excellent sealability is assured.
It is generally known that the adding of narrow, raised sealing faces can, under exposure to the same sealing pressure, lead to an improvement in the sealing properties. The main difference between the gaskets according to the invention and those of the state-of-the-art exists in the dimensions of the sealing ridges. According to the invention it is essential that the sealing ridges only slightly protrude over the main sealing faces of the gasket surface and, compared with the width of the main sealing faces, are very narrow. For example, the sealing ridges on cylinder head gaskets (the main sealing faces of which normally having a width of 1.3 to 3 mm) generally have a width of 0.1 to 0.5 mm. The width should, preferably, be 0.3 to 0.4 mm. The height of the sealing ridge in this case is normally 0.01 to 0.03 mm. Surprisingly, these small dimensions suffice to increase surface pressure and deformability in this region, such that micro-sealing can be considerably improved. However, in so doing, care is taken to avoid the sealing ridges sinking into the mating face to be sealed.
In contrast to conventional multi-layered steel gaskets, the single-piece gasket according to the invention has the advantage of being much simpler to construct. The single-piece construction requires no additional steps in applying any further seals or edging strips made of another material.
Even in the case of multi-layered gaskets, combinations of support lines and sealing faces—however in separated form—are known. For example, a sealing bead having a narrow compressive face can be arranged behind a bearing face. On gaskets having a predetermined distribution of thickness, the bearing face prevents vertical movement in said region, due to preliminary tension existing under all operating conditions. However, in the region adjacent to the bearing faces vertical movements in gap of the seal can occur in operation as a result of angular movements. Therefore, the narrow sealing faces on such an adjacent arrangement must be designed so that they can resiliently follow any minor displacement. In the configuration according to the invention this is not necessary, since the sealing faces lie within the bearing faces and these provide necessary rigidity to prevent movement.
Even on resiliently deformable gaskets, improvements in sealing can be attained, in that sealing ridges are applied additionally to main sealing faces. The sealing ridges, in differing from hitherto known designs, are, as noted, smaller in their dimensions. Due to the increased surface pressure and easier deformability in the region of the sealing ridges, sealing at the installation stage con be improved even further in comparison to conventional resiliently deformable gaskets.
REFERENCES:
patent: 2127372 (1938-08-01), Victor et al.
patent: 4285527 (1981-08-01), Connely
patent: 4635949 (1987-01-01), Lucas et al.
patent: 4676515 (1987-06-01), Cobb
patent: 4796897 (1989-01-01), Inciong
patent: 4817969 (1989-04-01), McDo
Beres John L.
Brittain James R.
Nixon & Peabody LLP
Safran David S.
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