WO1998009102A1

WO1998009102A1 - Gaskets

Info

Publication number: WO1998009102A1
Application number: PCT/GB1997/002276
Authority: WO
Inventors: Alan William Atkinson; Stephen Peter Bond; John Robert Hoyes; Gary Briggs
Original assignee: Flexitallic Ltd
Current assignee: Flexitallic Ltd
Priority date: 1996-08-29
Filing date: 1997-08-26
Publication date: 1998-03-05
Anticipated expiration: 1999-02-28
Also published as: GB2316720A; AU4024497A; GB9618061D0

Abstract

A gasket (10) comprises a sealing member which forms a closed loop extending around a hole. The sealing member is formed from springy metal and has a transverse cross section which is generally X-shaped and comprises two arms (12a, 14a) which project inwardly of the hole, and two arms (12b, 14b) which project outwardly of the hole. The inwardly projecting arms form a first seal around said hole, and outwardly projecting arms form a second seal around said hole. The arms engage bodies that they are to seal with at a convex surface away from the free ends.

Description

GASKETS

This invention is concerned with gaskets which are adapted when clamped between two bodies to seal the gap between the bodies around a chamber or passage jointly defined by the bodies and a method of sealing such gaps. 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. 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 a gasket of the latter type 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 U.S. 54,877,272 for a V-shaped cross- section) . In these gaskets, 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 . These gaskets form a seal along a single "line of sealing" with the seal of one arm directly beneath the seal of the other arm. The single line of sealing has the disadvantages that any failure along this line can result in leakage, and that the sealing member is poorly "balanced", ie the load on it is concentrated on a small area, and may easily be deformed.

G.B. 495,874 (Babcock & ilcox) shows a resilient seal manufactured from a solid blank of mild steel. Annular corner extensions are provided that project inwardly and outwardly to provide opposed inner and outer seals. The ends of the extensions are rounded to provide bearing surfaces. Whilst the corner extensions of each inner and outer seal are able to flex towards each other to a limited degree, that movement during which effective seals are able to be provided is necessarily restricted owing to the limited length of the extensions and their considerable thickness. Also because of these factors, the degree of rotation that can occur (that being at a particular circumferential location) whereby one of the inner or outer seals is spaced further apart than the other is necessarily limited without one of the seals actually failing.

It is an object of the present invention to provide a gasket which forms seals along two spaced lines of sealing, thereby reducing the possibility of leakage and improving the balance of the gasket. It is a further object to improve the operating characteristics of the gasket .

According to one aspect of the present invention in 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 comprises a sealing member which forms a closed loop extending around a hole which corresponds to the chamber or passage, wherein the sealing member has a transverse cross-section which is generally X-shaped and comprises two arms which project inwardly of the hole, and two arms which project outwardly of the hole, the inwardly projecting arms being adapted to each resiliently engage one of the bodies to form a first seal around said hole, and the outwardly projecting arms being adapted to each resiliently engage one of the bodies to form a second seal around said hole characterised in that the sealing member is formed from springy metal and that each arm has a free end and a surface adapted to seal with a body located away from the free end and provided by an outwardly curved surface of the arm.

In a gasket according to the invention , the first and second seals are on spaced, curved lines of sealing and are independent of one another so that the possibility of leakage is reduced. Furthermore, because the first and the second seals are spaced from one another, the sealing member is well balanced.

In a gasket according to the invention, each arm may present a convex surface to the body which it engages so that the line of engagement of each arm with one of the bodies is spaced from a free end of the arm, eg. each arm may be bow- shaped.

Each arm may be of generally uniform thickness along its length with the portion of each arm that is located away from the surface that is adapted to seal with a body towards the free end of that arm also being of the generally uniform thickness.

The sealing surface of each inwardly projecting arm may be arranged to change to move further away from the free ends of those arms or towards the free ends of those arms as the gap between those arms alters. The sealing surface of each outwardly projecting arm may be arranged to change to move further away from the free ends of those arms or towards the free ends of those arms as the gap between those arms alters. The sealing surface of each inwardly projecting arm may be arranged to move away from the free ends of those arms when the gap between the outwardly projecting arms reduces to be less than the gap between the inwardly directed arms. The sealing surface of each outwardly projecting arm may be arranged to move away from the free ends of those arms when the gap between the inwardly projecting arms reduces to be less than the gap between the outwardly directed arms.

A gasket according to the invention may have its sealing member formed from two pieces of metal, one of the pieces overlying the other. In this case, each piece forms one of said inwardly projecting arms and one of said outwardly projecting arms. For example, the pieces may be in the form of sheets, eg. of steel. The two pieces may be secured together by a sealing joint, the term "sealing joint" being used herein to indicate a joint which will not allow the passage of fluid from the chamber or passage around which the gasket seals. Preferably, the sealing joint is located in the central region of the sealing member, the central region being located between said first and said second seals. The sealing joint is to prevent leakage between the pieces and to secure the pieces together. The sealing joint may be formed by a continuous weld or by adhesive.

In an alternative construction, the sealing member is formed from two pieces of metal arranged side-by-side, one piece forming both of said inwardly projecting arms and the other piece forming both of said outwardly projecting arms, the two pieces being secured together by a joint located in a central region of the sealing member, the central region being located between said first and said second seals. For example, the two pieces may be both C- shaped in transverse cross-section with the open sides of the C's facing in opposite directions. In this construction, the joint does not need to be a sealing joint as there is no danger of leakage between the pieces.

In a further alternative construction, the sealing member is formed in one piece as an extrusion which is formed into a loop and has its ends welded together.

In further alternative constructions, the sealing member is formed by forming a ring to the required transverse cross-section by machining or by a combination of machining and deformation. The ring can be cut from a sheet, formed from strip with the ends being welded together, cut from the end of a cylinder etc. For example, slots can be machined into the top and the bottom surfaces of the ring and the ring (which then has a cross- section in the shape of an "H") and this machined ring can be bent to an X-cross section. The slots can alternatively be machined into the inside and outside surfaces of the ring.

A gasket according to the invention may also comprise layers of deformable material secured to said arms at least in the areas thereof which engage said bodies. This deformable material, which may, for example, be expanded graphite, soft metal or PTFE, is not intended to provide a sealing force but is intended to fill small fissures or cracks in the body or the arm to thereby improve the seal . The arms may be provided with ridges running longitudinally of the sealing member and the deformable material may cover these ridges. The ridges have the function of reducing the possibility that the deformable material will be extruded from the seal.

In order to prevent the sealing member from being crushed to such an extent that resilience is lost, the gasket may also comprise a compression- limiting stop. The stop may be provided by a thickened portion of the sealing member in a central region thereof. Alternatively, a compression-limiting stop may be secured to the sealing member at a central region thereof which is between said first and said second seals. Compression limiting stops may be welded or otherwise secured to both the top and the bottom of the sealing member.

The present invention also includes two bodies incorporating a gasket as herein referred to in which the gasket seals the gap between the bodies around a chamber or passage jointly defined by the bodies.

According to a further aspect of the present invention a method of sealing the gap between two bodies around a chamber or passage jointly defined by the bodies with a gasket comprises locating a sealing member of the gasket to form a closed loop extending around a hole which corresponds to the chamber or passage, the method comprising causing two arms of the sealing member to project inwardly of the hole, and two arms to project outwardly of the hole, the inwardly projecting arms each resiliently engaging one of the bodies to form a first seal around said hole and the outwardly projecting arms each resiliently engaging one of the bodies to form a second seal around the hole, the method being characterised in that the sealing member is formed from springy metal with each arm being caused to sealingly engage a body at a location spaced from the free end of the arm at an outwardly curved surface of the arm.

The method may comprise the sealing surface of each inwardly projecting arm changing to move further away from the free ends of those arms or towards the free ends of those arms upon alteration of the gap between those arms. The method may comprise the sealing surface of each outwardly projecting arm changing to move further away from the free ends of those arms or towards the free ends of those arms as the gap between those arms alters. The sealing surface of each inwardly projecting arm may move away from the free ends of those arms when the gap between the outwardly projecting arms reduces to be less than the gap between the inwardly directed arms. The sealing surface of each outwardly projecting arms may move away from the free ends of those arms when the gap between the inwardly projecting arms reduces to be less than the gap between the outwardly directed arms.

The present invention also includes a method of sealing the gap between two bodies around a chamber or passage jointly defined by the bodies with a gasket as herein referred to.

There now follow detailed descriptions, to be read with reference to the accompanying drawings, of five gaskets which are illustrative of the invention.

In the drawings:

Figure 1 is a transverse cross-sectional view taken through one side of the first illustrative gasket; Figures 2 to 5 are views similar to Figure 1 but of the second to fifth illustrative gaskets, respectively;

Figures 6, 7 and 8 are schematic views showing a gasket sealing with two flanges in a large spacing, a reduced spacing and at a rotational relationship respectively.

The first illustrative gasket 10 shown in Figure 1 is adapted when clamped between two bodies (not shown) , for example pipe flanges, to seal the gap between the bodies around a chamber or passage jointly defined by the bodies. The gasket 10 comprises a sealing member which forms a closed circular ring which extends around a hole through the gasket which corresponds to the chamber or passage. Figure 1 shows a transverse cross-sectional view through one side of the ring.

The sealing member of the gasket 10 is formed from two pieces 12 and 14 of springy sheet steel. Each piece

12 and 14 can be formed by stamping out an annulus from a sheet of steel or by bending a strip of steel into an annulus and welding its ends together. The piece 12 overlies the piece 14 and is secured thereto by a continuous weld forming a joint 16. The joint 16 is a sealing joint, ie. it seals between the pieces 12 and 14 completely around the gasket. The joint 16 is located in the central region of the sealing member.

The sealing member of the gasket 10 has a transverse cross-section which is generally X-shaped (as can be seen from Figure 1) . This cross-section comprises two arms 12a and 14a which project inwardly of the hole through the gasket 10, and two arms 12b and 14b which project outwardly of said hole. Each piece 12 and 14 forms one of the inwardly projecting arms and one of the outwardly projecting arms.

The inwardly projecting arms 12a and 14a are adapted to each resiliently engage one of the bodies, when the gasket 10 is in use, in order to form a first seal around the hole through the gasket. In other words, the arm 12a engages one of the bodies, eg. a first flange, and, as the clamping pressure increases, the deformation of the arm 12a causes pressure to build up along the line of engagement between the arm and the flange. The same occurs in relation to the arm 14a and the other body, eg. a second flange.

The outwardly projecting arms 12b and 14b are adapted to each resiliently engage one of the bodies to form a second seal around the hole through the gasket . The arms 12b and 14b act in similar manner to the arms 12a and 14a to press against the bodies. The lines of engagement of the arms 12b and 14b with the respective bodies constitute a second seal .

The arms 12a, 12b, 14a, and 14b are bow-shaped, bowing upwardly in the case of the arms 12a and 12b and downwardly in the case of the arms 14a and 14b to present convex surfaces to said bodies. Each arm, thus, presents a convex surface to the body which it engages. Because of the bow-shape of the arms, the line of engagement of each arm 12a, 12b, 14a and 14b with its respective body is spaced from a free end of the arm, ie. the end which is remote from the joint 16.

The gasket 10 also comprises layers of deformable material 18, specifically expanded graphite, which are secured by adhesive to the convex outer surfaces of the arms 12a, 12b, 14a and 14b. Thus, these layers 18 are on the areas of the arms which engage said bodies. The deformable material layers 18 are very thin (10 to 500 microns, eg. 50 to 200 microns) . The deformable material is intended to improve sealing by filling cracks or fissures in the bodies or arms.

The gasket 10 provides two seals (one provided by the arms 12a and 14a and the other by the arms 12b and 14b) so that the possibility of leakage is reduced. The gasket 10 is also well balanced because the first and the second seals thereof are on opposite sides of the central region at which the joint 16 is formed.

The second illustrative gasket 20 shown in Figure 2 is the same as the first illustrative gasket 10 except as hereinafter described and like reference numerals are used in Figure 2 for like parts. The gasket 20 differs from the gasket 10 in that the arms 12a, 12b, 14a and 14b are provided with ridges 22 running longitudinally of the sealing member, ie. around the ring formed by the sealing member, and the deformable material 18 covers these ridges. The ridges 22, which are produced by rolling, are intended to reduce the possibility of the deformable material 18 being extruded away from the first seal or the second seal .

The third illustrative gasket 30 shown in Figure 3 is the same as the first illustrative gasket 10 except as hereinafter described and like reference numerals are used in Figure 3 for like parts. The gasket 30 differs from the gasket 10 in that the pieces 12 and 14 from which the sealing member is formed have a greater thickness in the central region adjacent to the joint 16 and the arms taper so that they have reduced thickness at their free ends. The increased thickness in the central region provides a compression-limiting stop of the sealing member so that the gasket 30 cannot be compressed below the combined thickness of the pieces 12 and 14 in the central region. This prevents the sealing member from being compressed so far that it is no longer resilient. The tapering of the arms gives resilience over a wider load range.

The pieces 12 and 14 of the gasket 30 can be produced by machining annular sheets of constant thickness to the profile shown in Figure 3 or by extruding strips with this profile, forming them into a ring and welding their ends together.

The fourth illustrative gasket 40 shown in Figure 4 is the same as the first illustrative gasket 10 except as hereinafter described and like reference numerals are used in Figure 4 for like parts. The gasket 40 has pieces 12 and 14 of constant thickness but a compression- limiting stop is provided in the central region adjacent to the joint 16 by stop pieces 42 and 44 which are welded to the pieces 12 and 14, respectively, in the dips between the arms 12a and 12b, and 14a and 14b, respectively. The layers of deformable material may be included but are omitted from Figure 4.

The fifth illustrative gasket 60 shown m Figure 5 differs from the first illustrative gasket 10 in that it has its sealing member formed from two pieces of metal 62 and 64 arranged side-by-side which together give the sealing member a transverse cross-section which is generally X-shaped. The pieces 62 and 64 are both C- shaped in transverse cross-section and are arranged back- to-back with the open side of the piece 62 facing inwardly of the hole through the gasket and the open side of the piece 64 facing outwardly of said hole. The pieces 62 and 64 are joined by a weld 66 which acts as a joint holding them in the back-to-back relationship. The piece 62 forms two inwardly projecting arms 62a and 62b which act in similar manner to the arms 12a and 14a of the gasket 10. The piece 64 forms two outwardly projecting arms 64a and 64b which act in a similar manner to the arms 12b and 14b of the gasket 10.

In the gasket 60, a first seal is formed by the arms 62a and 62b and a second seal is formed by the arms 64a and 64b. Leakage between the arms 62a and 62b is prevented by the central portion of the piece 62. Thus, the joint 66 does not have to be a sealing joint. The gasket 60 is balanced since the first and the second seals are on opposite sides of a central region of the gasket where the joint 66 secures the pieces 62 and 64 together. The arms 62a, 62b, 64a and 64b are also provided with layers of deformable material 68 which are similar to the layers 18 of the gasket 10 and act in a similar manner.

If desired, any of the illustrative gaskets can be given compression-limiting stops similar to those 42 and 44 of the gasket 40 or ridges similar to the ridges 22.

The gaskets could also be made out of one piece only such as by machining or extruding the gaskets.

Any of the gaskets could be used to seal the flanges 70 and 72 shown in Figures 6 to 8. For convenience though that sealing will be described in relation to the gasket 10 alone.

In figure 6 the gasket 10 seals the flanges 70 and 72 at inner and outer locations with the sealing parts of the arms being towards the ends of the arms on the arcuate surfaces of the arms . As the flanges move towards each other, towards the position shown in figure 7, the part of each arm that provides the seal moves inwardly, away from the free ends of the arms. In all cases though a convex or outwardly curved surface of the arms provides the seal.

When one flange 70 is tilted or rotated relative to the other flange, (or where one flange is not parallel to the other) as shown in figure 8, the gasket still seals at inner and outer regions with the portion of the arms 12b and 14b that provide the seal being further away from the ends of those arms than the position of the arms 12a and 14a that provide the other seal. Tilting or rotation in the other direction will still allow two radially spaced seals to be provided albeit that the parts of the arms that provide the seals will change.

Tilting or rotation of one flange relative to the other may occur as a result of uneven tightening of bolts connecting the flanges or as a result of the flanges being relatively flimsy, or as a result of thermal effects or as a result of excessive internal pressure, for instance.

The reader's attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

All of the features disclosed in this specification (including any accompanying claims, abstract and drawings) , and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

Each feature disclosed in this specification (including any accompanying claims, abstract and drawings) , may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

The invention is not restricted to the details of the foregoing embodiment (s) . The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings) , or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Claims

1. A gasket (10, 20, 30, 40, 60) adapted when clamped between two bodies (70, 72) to seal the gap between the bodies around a chamber or passage jointly defined by the bodies, the gasket comprising a sealing member which forms a closed loop extending around a hole which corresponds to the chamber or passage, wherein the sealing member has a transverse cross-section which is generally X-shaped and comprises two arms (12a, 14a, 62a, 62b) which project inwardly of the hole, and two arms (12b, 14b, 64a, 64b) which project outwardly of the hole, the inwardly projecting arms being adapted to each resiliently engage one of the bodies to form a first seal around said hole, and the outwardly projecting arms being adapted to each resiliently engage one of the bodies to form a second seal around said hole characterised in that the sealing member is formed from springy metal and that each arm has a free end and a surface adapted to seal with a body located away from the free end and provided by an outwardly curved surface of the arm.

2. A gasket as claimed in claim 1 in which the surface of each arm that is adapted to seal with a body is a convex surface.

3. A gasket as claimed in claim 1 or 2 in which each arm is of generally uniform thickness along its length with the portion of each arm that is located away from the surface that is adapted to seal with a body towards the free end of that arm also being of the generally uniform thickness .

4. A gasket as claimed in any preceding claim in which the sealing surface of each inwardly projecting arm (12a, 14a, 62a, 62b) is arranged to change to move further away from the free ends of those arms or towards the free ends of those arms as the gap between those arms alters.

5. A gasket as claimed in any preceding claim in which the sealing surface of each outwardly projecting arm 12b, 14b, 64a, 64b) is arranged to change to move further away from the free ends of those arms or towards the free ends of those arms as the gap between those arms alters.

6. A gasket as claimed in claim 4 or 5 in which the sealing surface of each inwardly projecting arm is arranged to move away from the free ends of those arms when the gap between the outwardly projecting arms reduces to be less than the gap between the inwardly directed arms .

7. A gasket as claimed in any of claims 4 to 6 in which the sealing surface of each outwardly projecting arm is arranged to move away from the free ends of those arms when the gap between the inwardly projecting arms reduces to be less than the gap between the outwardly directed arms .

8. A gasket according to any of the preceding claims, wherein the sealing member (10, 20, 30, 40) is formed from two pieces of metal, one of the pieces overlying the other, each piece forming one of said inwardly projecting arms and one of said outwardly projecting arms, the two pieces being secured together by a sealing joint (16) located in a central region of the sealing member, the central region being located between said first and said second seals.

9. A gasket according to any one of claims 1 to 7, wherein the sealing member (60) is formed from two pieces of metal arranged side-by-side, one piece forming said inwardly projecting arms (62a, 62b) and the other piece forming said outwardly projecting arms (64a, 64b) , the two pieces being secured together by a joint (66) located in a central region of the sealing member, the central region being located between said first and said second seals.

10. A gasket according to any of claims 1 to 7, wherein the sealing member is formed in one piece as an extrusion.

11. A gasket according to any of claims 1 to 7, wherein the sealing member is formed in one piece by machining.

12. A gasket according to any preceding claim, wherein the gasket also comprises layers of deformable material secured to said arms at least in the areas thereof which engage said bodies.

13. A gasket according to claim 12, wherein the arms are provided with ridges (18, 68) running longitudinally of the sealing member and the deformable material covers these ridges.

14. A gasket according to any one of claims 1 to 13, wherein a compression-limiting stop (42, 44) is provided by a thickened portion of the sealing member in a central region thereof .

15. A gasket according to any one of claims 1 to 14, wherein the gasket also comprises a compression- limiting stop (42, 44) secured to the sealing member at a central region thereof which is between said first and said second seals.

16. A gasket substantially as hereinbefore described with reference to, and as shown in, Figure 1, or Figure 2, or Figure 3 , or Figure 4 , or Figure 5 of the accompanying drawings .

17. Two bodies (70, 72) incorporating a gasket (10, 20, 30, 40, 60) as claimed in any preceding claim in which the gasket seals the gap between the bodies around a chamber or passage jointly defined by the bodies.

18. A method of sealing the gap between two bodies (70, 72) around a chamber or passage jointly defined by the bodies with a gasket (10, 20, 30, 40, 60) comprising locating a sealing member of the gasket to form a closed loop extending around a hole which corresponds to the chamber or passage, the method comprising causing two arms

(12a, 14a, 62a, 62b) of the sealing member to project inwardly of the hole, and two arms (12b, 14b, 64a, 64b) to project outwardly of the hole, the inwardly projecting arms each resiliently engaging one of the bodies to form a first seal around said hole and the outwardly projecting arms each resiliently engaging one of the bodies to form a second seal around the hole characterised in that the sealing member is formed from springy metal with each arm being caused to sealingly engage a body at a location spaced from the free end of the arm at an outwardly curved surface of the arm.

19. A method as claimed in claim 18 comprising arranging for the sealing surface of each inwardly projecting arm

(12a, 14a, 62a, 62b) to change to move further away from the free ends of those arms or towards the free ends of those arms upon alteration of the gap between those arms.

20. A gasket as claimed in claim 18 or 19 in which the sealing surface of each outwardly projecting arm (12b, 14b, 64a, 64b) changes to move further away from the free ends of those arms or towards the free ends of those arms as the gap between those arms alters.

21. A gasket as claimed in claim 19 or 20 in which the sealing surface of each inwardly projecting arm moves away from the free ends of those arms when the gap between the outwardly projecting arms reduces to be less than the gap between the inwardly directed arms .

22. A gasket as claimed in any of claims 19 to 21 in which the sealing surface of each outwardly projecting arms moves away from the free ends of those arms when the gap between the inwardly projecting arms reduces to be less than the gap between the outwardly directed arms.

23. A method of sealing the gap between two bodies around a chamber or passage jointly defined by the bodies with a gasket, the method being substantially as herein described with reference to, and as shown in Figure 1, or Figure 2, or Figure 3, or Figure 4, or Figure 5, or Figure 6, or Figure 7 , or Figure 8 of the accompanying drawings .

24. A method of sealing the gap between two bodies around a chamber or passage jointly defined by the bodies with a gasket as claimed in any of claims 1 to 17.