GB2316718A - Gasket - Google Patents

Abstract

A gasket (10) comprises a first sealing member (12) and a second sealing member (14) both made of springy metal, and a clamping member (16) which holds the first and the second sealing members in an overlying relationship. The first sealing member (12) has an arm portion (12a) projecting from the clamping member (16), the arm portion being adapted to resiliently form a seal with a first body. The second sealing member (14) has an arm portion projecting from the clamping member (16), the arm portion being adapted to resiliently form a seal with a second body.

Description

GASKET This invention is concerned with a gasket of the type which is adapted when clamped between two bodies to seal the gap between the bodies around a chamber or passage jointly defined by the bodies. Such a gasket may be used, for example, for sealing the gap between flanges at the ends of pipes.

Gaskets require to be resilient in order to achieve a seal. In some gaskets, the resilience is achieved by using inherently resilient material such as rubber or cork and, in other gaskets, the resilience is achieved by utilising springy metal which resists being bent out of its initial shape. This invention is concerned with the latter type of gasket which comprises a sealing member which forms a closed loop extending around a hole which corresponds to the chamber or passage. Such gaskets are often in the shape of an annular ring but may have other shapes.

Accordingly, the term "ring" is used herein to include a continuous band surrounding a hole of any shape.

Known gaskets made of springy metal have sealing members which have generally C or V-shaped transverse cross-sections (see US 4,877,272 for a V-shaped crosssection). The cross-section comprises two arms which project either inwardly or outwardly of the hole, the arms being adapted to each resiliently engage one of the bodies to form a seal around said hole. In this type of gasket, the sealing force is achieved by deformation of a single piece of metal which bends sharply between its lines of engagement with the bodies against which the gasket seals.

Because the single piece of metal has to bend sharply, there is a danger that cracking may occur when the clamping force is applied.

It is an object of the present invention to provide a gasket in which springy metal is used to provide the sealing force, the gasket having a reduced risk of cracking.

The invention provides a gasket adapted when clamped between two bodies to seal the gap between the bodies around a chamber or passage jointly defined by the bodies, the gasket forming a ring extending around a hole which corresponds to the chamber or passage, wherein the gasket comprises a first sealing member and a second sealing member both made of springy metal, and a clamping member which holds the first and the second sealing members in an overlying relationship, the first sealing member having an arm portion projecting from the clamping member, the arm portion of the first sealing member being adapted to resiliently engage one of said bodies to form a seal therewith, and the second sealing member having an arm portion projecting from the clamping member, the arm portion of the second sealing member being adapted to resiliently engage the other of said bodies to form a seal therewith.

In a gasket in accordance with the invention, the sealing forces are provided by two sealing members which do not require to be sharply bent so that they have a reduced risk of cracking. The clamping member can be made of thicker material which can resist cracking better than a springy metal.

Preferably, the clamping member presses said first and said second sealing members together so that a seal is formed between them. This arrangement prevents leakage between the sealing members. The clamping member may be formed from sheet metal and have a generally C-shaped transverse cross-section comprising two legs between which the sealing members are received, the legs engaging the sealing members.

In order to improve the seals by filling small cracks or fissures in the bodies or in the sealing members, the gasket may also comprise layers of deformable material, eg expanded graphite, PTFE or soft metal, which are secured, eg by adhesive, to said arm portions at least in the areas thereof which engage said bodies. The clamping member may also be provided with such layers so that, if it is engaged by said bodies, a better seal is formed supplementing the seal formed by the arms.

In order to prevent the gasket from being crushed to such an extent that resilience is lost, said clamping member may provide a compression-limiting stop to prevent excessive compression of the gasket.

The arm portions may be adapted to engage the bodies with free ends of the arm portions or may, alternatively, be bow-shaped so that they present convex surfaces to the bodies and increase the area of sealing.

There now follows a detailed description, to be read with reference to the accompanying drawing, of a gasket which is illustrative of the invention.

The drawing is a transverse cross-sectional view taken through one side of the illustrative gasket.

The illustrative gasket 10 is adapted when clamped between two bodies (not shown) to seal the gap between the bodies around a chamber or passage defined by the bodies.

For example, the gasket 10 may be utilised to seal around a fluid passage in pipes having flanges at their ends, the gasket 10 being received between the flanges which are then clamped together by bolts. The gasket 10 forms a ring extending around a hole which corresponds to the chamber or passage.

The gasket 10 comprises a first sealing member 12 and a second sealing member 14 which are both made from springy metal in sheet form. The members 12 and 14 can be stamped out of sheet steel as a complete annulus or can be formed from strip steel which is bent into a loop and has its ends joined together by a weld. Although shown as of constant a thickness, the members may vary in thickness, this being achieved, eg, by machining. The gasket 10 also comprises a clamping member 16 which holds the first 12 and the second 14 sealing members in an overlying relationship.

As can be seen in the drawing, the first sealing member 12, in transverse cross-section, is generally arcuate, having a generally convex surface facing towards the member 14 and a concave surface facing away from the member 14. The second sealing member 14 has the same shape as the member 12 but is inverted relative thereto so that it has its convex surface facing towards the member 12 and its concave surface facing away therefrom. The first 12 and the second 14 sealing members engage one another along a line 18 at the lowest point of the member 12 and the highest point of the member 14.

The first sealing member 12 has a longer arm portion 12a projecting from the line 18 outwardly of the hole through the gasket and a shorter arm portion 12b projecting from the line 18 inwardly of said hole. The second sealing member 14 has a similar longer arm portion 14a and a similar shorter arm portion 14b. The arms 12a and 14a may vary in thickness, eg tapering to their thinnest at their free ends.

The clamping member 16 and is made of sheet metal which is substantially thicker than that forming the members 12 and 14. The clamping member 16 is generally Cshaped in transverse cross-section, comprising two legs 16a and 16b between which the shorter arm portions 12b and 14b of the sealing members are received. The legs 16a and 16b have lips 16c and 16d which are turned towards the sealing members 12 and 14, the lips being adapted to grip the sealing members and clamp them together. The clamping member 16 also comprises a joining portion 16e from which the legs 16a and 16b project. The joining portion 16e extends past the free ends of the shorter arm portions 12b and 14b. In this case, the joining portion 16e bounds the hole through the gasket 10. Since the joining portion 16e extends normally of the plane of the gasket 10, it is adapted to provide a compression-limiting stop to prevent excessive compression of the gasket, ie if excessive clamping force brings the bodies into contact with the clamping member 16, further compression is resisted by the portion 16e.

The longer arm portions 12a and 12b project away from the clamping member 16 in a direction which is radially outwards of the hole through the gasket 10. The arm portion 12a is adapted so that its free end can resiliently engage one of the bodies between which the gasket 10 is clamped to form a seal therewith. The arm portion 14a is adapted so that its free end can resiliently engage the other of said bodies to form a seal therewith. Thus, the gasket 10 forms a seal with both of said bodies.

In order to improve the seals formed by the arm portions 12a and 14a and to form a seal between the lips 16c and 16d and the sealing members 12 and 14, the gasket 10 also comprises layers of deformable material 20, specifically expanded graphite, which are secured to the concave surfaces of the members 12 and 14. The layers 20, thus, extend into the areas in which the arm portions 12a and 14a engage the bodies and assist in sealing by filling small cracks or fissures in these areas. The layers 20 also pass through the areas where the lips 16c and 16d engage the members 12 and 14, respectively, and serve to improve the seal in these areas.

The gasket 10 provides a good seal without requiring metal sealing members to be sharply bent.

In variations of the gasket 10, layers of deformable material similar to the layers 20 are adhered to the outer surfaces of the legs 16a and 16b and/or to the convex surfaces of the sealing members 12 and 14. It is also possible to have the arm portions 12a and 14a projecting inwardly of the hole through the gasket, the clamping member 16 then facing the opposite way. This latter construction has the advantage that pressure of the fluid in the passage or chamber, around which the gasket seals, acts between the arm portions 12a and 14a and assists in urging them against the bodies.

Claims (7)

1A gasket adapted when clamped between two bodies to seal the gap between the bodies around a chamber or passage jointly defined by the bodies, the gasket forming a ring extending around a hole which corresponds to the chamber or passage, wherein the gasket comprises a first sealing member and a second sealing member both made of springy metal, and a clamping member which holds the first and the second sealing members in an overlying relationship, the first sealing member having an arm portion projecting from the clamping member, the arm portion of the first sealing member being adapted to resiliently engage one of said bodies to form a seal therewith, and the second sealing member having an arm portion projecting from the clamping member, the arm portion of the second sealing member being adapted to resiliently engage the other of said bodies to form a seal therewith.

2 A gasket according to claim 1, wherein the clamping member presses said first and said second sealing members together so that a seal is formed between them.

3 A gasket according to either one of claims 1 and 2, wherein the clamping member is formed from sheet metal and has a generally C-shaped transverse cross-section comprising two legs between which the sealing members are received, the legs engaging the sealing members.

4 A gasket according to any one of claims 1 to 3, wherein the gasket also comprises layers of deformable material which are secured to said arm portions at least in the areas thereof which engage said bodies.

5 A gasket according to any one of claims 1 to 4, wherein said clamping member is adapted to provide a compression-limiting stop to prevent excessive compression of the gasket.

6 A gasket according to any one of claims 1 to 5, wherein said arm portions are adapted to engage said bodies with free ends thereof.

7 A gasket substantially as hereinbefore described with reference to, and as shown in, the accompanying drawing.