GB2286861A - Gasket - Google Patents

Abstract

A gasket (36; 40) comprises a relatively rigid core layer (20) which extends generally parallel to sealing surfaces (12, 14) of the gasket. The core layer (20) is formed with a plurality of ridges (26) which are defined by an inwardly-facing surface (30) and by an outwardly-facing surface (32). The inwardly-facing surfaces (30) extend substantially normally to the sealing surfaces (12, 14) so that they resist extrusion of sealing material. <IMAGE>

Description

GASKET This invention is concerned with a gasket and, in particular, with a gasket which is suitable for use in providing a seal between opposed flanges, eg in a heat exchanger.

Gaskets for use in providing a seal between two flanges generally comprise an assembly providing two oppositely-facing sealing surfaces, each of which is intended to engage one of the flanges. The sealing surfaces extend between a closed inner edge of the gasket and an outer edge thereof. In service, the closed inner edge will be in contact with fluid under pressure and the gasket is intended to prevent escape of the fluid through the gap between the flanges. Such an assembly often comprises a core layer formed from a relatively rigid material, eg steel, and two sealing layers of relatively soft deformable material which are disposed on opposite sides of said core layer. The soft, deformable material may, for example, be expanded graphite foil and deformation of this material is intended to effect a seal when pressure is applied to compress the gasket between the flanges.

It is well known in such gaskets to provide the core layer with a plurality of ridges which extend around the inner edge of the gasket. Such a prior art gasket is illustrated in Figure 1. These ridges, when viewed along a section extending from the inner edge to the outer edge of the gasket, appear triangular with each ridge being defined by an inwardly-facing surface, ie facing towards the inner edge of the gasket, and by an outwardly-facing surface. The inwardly and outwardly-facing surfaces are both inclined at approximately 450 to the sealing surfaces of the gasket. This profile is known as a "Kamm-profile".

The purpose of the ridges is to displace the deformable material into the grooves formed between the ridges as the pressure on the gasket between the flanges is increased.

The ridges then ensure good sealing along the crests of the ridges and act to resist the deformable material being extruded outwardly by the pressure of the fluid being contained by the gasket.

However, it is found in practice that under certain circumstances, pressure of the fluid can displace the deformable material over the crests of the ridges so that the fluid material escapes through the gasket.

It is an object of the present invention to provide a gasket in which the possibility of fluid escape is reduced.

The invention provides a gasket comprising an assembly providing two oppositely-facing sealing surfaces extending between a closed inner edge of the gasket and an outer edge thereof, the assembly comprising a relatively rigid core layer extending generally parallel to said sealing surfaces, the assembly also comprising two sealing layers formed of relatively soft deformable material disposed on opposite sides of said core layer, the core layer being formed with a plurality of ridges extending around said inner edge, each ridge being defined by an inwardly-facing surface and an outwardly-facing surface, wherein said inwardly-facing surfaces extend substantially normally to said sealing surfaces.

By the term "substantially normally" is intended a direction which is considerably closer to an inclination of 900 to said sealing surfaces than to an inclination of 450 thereto. For example, said direction may be within 100 of said inclination, preferably within 50 thereof.

In a gasket in accordance with the invention, any tendency for the material of the sealing layers to move outwardly of the gasket is opposed by the inwardly-facing surfaces of the ridges which extend substantially normally relative to the possible direction of movement of the deformable material. Thus, the maximum resistance to such movement is provided by said surfaces.

Preferably, the core layer is made of steel and the ridges are formed by machining grooves into the core layer.

Alternatively, the grooves may be formed by roll forming.

Preferably, the sealing layers are formed from expanded graphite foil.

The outwardly-facing surfaces of the ridges may be inclined to said sealing surfaces, eg at approximately 450, in which case, it may be desirable to radius the crests of the ridges to prevent them from cuttting through the sealing layers. Alternatively, the outwardly-facing surfaces may also extend substantially normally to said sealing surfaces in which case said ridges have flat tops.

There now follows a detailed description, to be read with reference to the accompanying drawings, of a prior art gasket and of two gaskets which are illustrative of the invention.

In the drawings: Figure 1 is a cross-sectional view taken through the the prior art gasket; and Figures 2 and 3 are views similar to Figure 1 but of the first and second illustrative gaskets, respectively.

The gasket 10 shown in Figure 1, the first illustrative gasket 36 shown in Figure 2, and the second illustrative gasket 40 shown in Figure 3 are similar in many respects and the same reference numerals are used for similar parwts of each gasket. The gaskets 10, 36 and 40 all comprise an assembly providing two-oppositely facing sealing surfaces 12 and 14. The sealing surfaces 12 and 14 extend between a closed inner edge 16 of the gasket and an outer edge 18 thereof. In these cases, the gaskets are generally cylindrical so that each inner edge 16 is circular in plan view (not shown) as is each outer edge 18.

When the gasket 10, 36 or 40 is in service, the inner edge 16 is in contact with fluid under pressure and the sealing surfaces 12 and 14 are in contact with flanges (not shown) between which the gasket is compressed.

The assemblies forming the gaskets 10, 36 and 40 each comprise a core layer 20 extending generally parallel to the sealing surfaces 12 and 14. The core layer 20 is formed from a relatively rigid material, in this case steel, and is of sufficient thickness that the layer 20 is rigid, ie does not substantially deform under the forces applied thereto when the gasket is in service. The core layer 20 extends from the inner edge 16 to the outer edge 18.

The assemblies comprising the gaskets 10, 36 and 40 also each comprise two sealing layers 22 and 24 of relatively soft deformable material, in this case expanded graphite foil. The layers 22 and 24 are disposed on opposite sides of the core layer 20 so that they overlie the layer 20. The sealing layers 22 and 24 extend from the inner edge 16 to the outer edge 18.

The core layer 20 of each of the gaskets 10, 36 and 40 is formed with a plurality of ridges 26 which extend around the inner edge 16. Thus, the ridges 26 are concentric and extend parallel to one another. The ridges 26 are formed by machining the grooves 28 into the surface of a cylindrical sheet of steel having flat upper and lower surfaces. Each ridge 26 is defined by an inwardly-facing surface 30 and an outwardly-facing surface 32. However, the inclinations of the surfaces 30 and 32 vary between the gaskets 10, 36 and 40 causing the shapes of the grooves 28 and the ridges 26 to vary also.

The inwardly-facing surfaces 30 of the gasket 10 all extend substantially at 450 to the sealing surfaces 12 and 14 and the outwardly-facing surfaces 32 are also inclined at 450 to the sealing surfaces 12 and 14 and meet the surfaces 30 at the bottoms of the grooves 28 and at the tops of the ridges 26.

The inwardly-facing surfaces 30 of the first illustrative gasket 36 all extend substantially normally to the sealing surfaces 12 and 24, ie they meet the layers 22 and 24 at 900. The outwardly-facing surfaces 32, however, are inclined at 450 to the sealing surfaces 12 and 14 and meet the surfaces 30 at the bottoms of the grooves 28 and at the tops of the ridges 26.

In the second illustrative gasket 40, the inwardlyfacing surfaces 30 all extend substantially normally to the sealing surfaces 12 and 14 and the outwardly-facing surfaces 32 also all extend substantially normally to said sealing surfaces 12 and 14. Thus, the surfaces 30 and 32 do not meet and the ridges 26 have flat tops 50, extending parallel to the sealing surfaces 12 and 14. The ridges 26 have flat bottoms 54 also extending parallel to the seelaing surfaces 12 and 14.

The gaskets 10, 36 and 40 are intended to be positioned with their sealing surfaces 12 and 14 in contact with opposed flanges (not shown). Upon the application of a tightening force, the sealing layers 22 and 24 are deformed into the grooves 28 and the ridges 26 concentrate the stress causing localised sealing along the tops of the ridges 26. With the gasket 10, there is a possibility that the material of the sealing layers 22 and 24 may be extruded over the tops of the ridges 26 with eventual loss of sealing. With the gaskets 36 and 40, however, tests have shown that this possibility is substantially reduced as any tendency for the material of the sealing layers 22 and 24 to be extruded outwardly is resisted because the material in the grooves 28 is confronted by the surfaces 30 which extend normally to the extrusion direction.

Claims (4)

1A gasket comprising an assembly providing two oppositely-facing sealing surfaces extending between a closed inner edge of the gasket and an outer edge thereof, the assembly comprising a relatively rigid core layer extending generally parallel to said sealing surfaces, the assembly also comprising two sealing layers of relatively soft deformable material disposed on opposite sides of said core layer, the core layer being formed with a plurality of ridges extending around said inner edge, each ridge being defined by an inwardly-facing surface and an outwardly-facing surface, wherein said inwardly-facing surfaces extend substantially normally to said sealing surfaces.

2 A gasket according to claim 1, wherein said outwardly facing surfaces are inclined to said sealing surfaces.

3 A gaskets according to claim 1, wherein said outwardly facing surfaces also extend substantially normally to said sealing surfaces.

4 A gasket substantially as hereinbefore described with reference to, and as shown in, Figure 2 or Figure 3 of the accompanying drawings.