GB2327477A

GB2327477A - Jointing gasket and spigot-socket pipe joint incorporating the same

Info

Publication number: GB2327477A
Application number: GB9815559A
Authority: GB
Inventors: Thomas William Wildgoose
Original assignee: Glynwed Pipe Systems Ltd
Current assignee: Glynwed Pipe Systems Ltd
Priority date: 1997-07-18
Filing date: 1998-07-20
Publication date: 1999-01-27
Also published as: GB9815559D0

Abstract

The gasket (1) comprises a body (2) of elastomeric material which is axially extended and has a sealing portion (6) extending for part of its axial length from one end and a holding portion (7) which extends for another part of its axial length from the other end and contains a holding ring (5) within its thickness. The sealing pertion (6) is resilient and of a radial thickness greater than the distance between an outer circumferential wall surface (18) of the spigot (11) and an inner circumferential wall surface (17) of the socket (13). The sealing portion (6) is therefore under radial compressive force when engaged between the two wall surfaces (17,18). The holding portion (7) has a radial thickness less than the distance between the wall surfaces (17,18) and the holding ring (5) affords resistance to deformation of the holding portion (7) The holding ring is a helically coiled spring (5) extending annularly in the holding portion (7).

Description

JOINTING GASKET AND PIPE JOINT INCORPORATING THE SAME This invention relates to a jointing gasket for pipes, and a pipe joint incorporating a jointing gasket.

More particularly the invention relates to an elastomeric jointing gasket for providing a seal in a pipe joint of the spigot and socket kind.

It is to be understood that the expression "pipe" as used herein is intended to include pipes and tubes as such, and also pipe-like fittings used within pipework such as elbows, 'T' bends and similar fittings, and also other elements such as valves incorporated in pipework and having parts of a pipe-like nature.

Joints of the above-mentioned kind are utilised in the interconnection of pipes of water or gas carrying capability, for example, and comprise a socket at one end of a pipe within which is located an annular elastomeric jointing gasket which is sealingly engageable with a spigot of the next adjacent pipe on insertion into the socket, so as to provide a sealed joint. One known example is disclosed in GB Patent Specification No. 827 353 in which the jointing gasket is axially elongated and is made in one piece of an elastomeric material which is intended to have sufficient resilience to provide the sealing engagement at the joint but not so resilient as to be displaced from the joint upon assembly. The gasket has a sealing portion extending for part of its axial length from one end and a holding portion extending for another part of its axial length from the other end. The sealing portion has a radial thickness greater than the distance between the outer circumferential walt surface of the spigot on which the gasket is to be fitted for use and the inner circumferential wall surface of the socket into which the spigot is received. That radial thickness is required for the sealing portion to be under radial compressive force when engaged between the two wall surfaces so as to provide an effective seal. It is necessary for the sealing portion to have some resilience for its fitting and compression. The holding portion has a radial thickness less than the distance between the said wall surfaces and it is desirable for it to have some resistance to deformation so as to restrain the gasket from being blown out of the mouth of the socket under internal pressures in the jointed pipes when the pipes are in use. It is usual for sockets to have an internal lip which partially extends across the gap between the socket and spigot and the holding portion abuts against the inside of the lip around the spigot.

There has been difficulty in providing a one-piece elastomeric jointing gasket such as just described which provides the required resilience at the sealing portion and the resistance to deformation at the holding portion. An alternative proposal has been to make the gasket in two pieces which are joined together, the one piece being of a resilient elastomeric material to provide the sealing portion and the other piece being of a harder elastomeric material to provide the holding portion. A method of manufacture is to mould the piece for the holding portion first and then to mould the piece forming the sealing portion onto that. It is important for there to be a good bond between the two pieces. This has not always been achieved and splitting can occur between the two pieces when the gasket is in use, which is undesirable.

It is an object of the present invention to provide a jointing gasket which affords a reliable seal in pipe joints of the spigot and socket kind, and a pipe joint incorporating such a jointing gasket.

According to a first aspect of the present invention there is provided a jointing gasket for a spigot and socket pipe joint comprising a body of elastomeric material which is axially extended and has a sealing portion extending for part of its axial length from one end and a holding portion extending for another part of its axial length from the other end, the sealing portion being resilient and of a radial thickness greater than the distance between an outer circumferential wall surface of the spigot on which the gasket is adapted to be fitted for use and an inner circumferential wall surface of the socket into which the spigot is to be received at the pipe joint, so as to be under radial compressive force when engaged between the two wall surfaces, and the holding portion having a radial thickness less than the distance between the said wall surfaces and containing within its thickness a holding ring which affords resistance to deformation of the holding portion.

The holding ring may have some resilience. Preferably the holding ring is in the form of a helically coiled spring extending annularly, co-axially, in the holding portion. The spring may be embedded, for example by moulding, in the holding portion as the body of the gasket is formed. It may occupy a substantial part of the thickness of the holding portion. By having the holding ring contained within the holding portion the integrity of the elastomeric material of the body of the gasket is maintained, and consequently problems of splitting such as may be experienced with the known two-piece gaskets described are avoided.

The body may be made of any suitable elastomeric material such as rubber or a mouldable polymeric material. It may be made of a relatively soft elastomeric material such as used for the resilient sealing portion of the known two-piece jointing gasket described above. Although such material may be used it has been found that by the provision of the holding ring in the holding portion it is possible to give the holding portion substantial resistance to deformation. The holding portion can thus afford substantial resistance to blowing out of the gasket from the pipe joint to which it is applied for use.

The body of the gasket may taper in thickness gradually from the resilient portion end to the holding portion end.

Used with a socket which has an internal lip at its outer end, the gasket will be fitted for the holding portion to abut against the inside of the lip, in the usual way.

The gasket may be used with a socket which has a locking formation at its inner circumferential wall surface to locate the gasket axially in the socket. The body of the gasket may have a complementary formation adapted to co-operate with the locking formation. One of the formations may comprise a ridge or ridges and the other a groove or grooves.

One or more surfaces of the gasket may be coated with a low friction coating to aid fitting of the gasket in a socket of a pipe and/or fitting of a spigot of a pipe within the gasket.

According to a second aspect of the present invention there is provided a spigot and socket pipe joint including a jointing gasket in accordance with the foregoing first aspect of the invention fitted between an outer circumferential wall surface of the spigot and an inner circumferential wall surface of the socket to seal the joint.

The pipes may be made of various materials, eg plastics, fibreglass, metal, ceramic other compositions, and may take various forms. They may be of various shapes and dimensions.

Embodiments of the present invention will now be described by way of example only with reference to the accompanying drawings in which: Figure 1 is a simplified fragmentary axial section through a spigot and socket pipe joint including a first embodiment of a jointing gasket in accordance with the invention; Figure 2 is a simplified fragmentary axial section through a spigot and socket pipe joint including a second embodiment of a jointing gasket in accordance with the invention, and Figure 3 is an axial section through the spigot and socket pipe joint and gasket of Figure 2 showing the spigot engaged in the socket.

The jointing gasket of Figure 1, generally indicated at 1, has an annular body 2 which is axially extended, is tapered in its cross-section from one, inner, end 3 to its opposite, outer, end 4 and has an annular helically coiled spring 5 contained within its thickness adjacent to the outer end 4. Part of the axial length of the body 2 extending from the inner end 3 forms a sealing portion 6 and part of its axial length extending from the outer end 4 forms a holding portion 7 which contains the spring 5. The inner end 3 is bulbous and the outer end 4 is substantially squared. There is a gradual taper in the thickness of the body from the inner end 3 through the sealing portion 6 and holding portion 7 to the outer end 4, a radially outer surface 8 of the body being substantially cylindrical and a radially inner surface 9 being outwardly flared from the inner end 3 to the outer end 4 to provide the tapering thickness of the body. An annular groove 10 is formed in the radially outer surface 8 at the holding portion intermediate where the spring 5 is contained and the sealing portion 6.

The radial thickness of the sealing portion 6 is greater than the distance between an outer circumferential wall surface of the spigot of a pipe with which the jointing gasket is designed to be used and an inner circumferential wall surface of a socket of a pipe to which the spigot of the one pipe is to be joined. At the holding portion the radial thickness is less than that distance.

The body is made of a resilient elastomeric material such as natural or synthetic rubber. It is moulded to shape. Prior to the moulding operation the spring 5, which is of suitable spring metal, is located in its annular form in the mould. The elastomeric material is then introduced into the mould so that the spring becomes fully embedded in the material at the holding portion of the moulded body. Whereas the sealing portion 6 is resilient, the presence of the spring 5 in the holding portion stiffens that part of the body so that it has substantial resistance to deformation.

By virtue of the fact that just one elastomeric material is used for the body and the body can be moulded in one operation around the spring, which can be inexpensive and can be readily located for the moulding, the gasket can be produced simply and cheaply.

For use the gasket may be fitted for example, as shown, to seal the joint between a cylindrical spigot 11 of a first pipe 12 and a belled socket 13 of a second pipe 14. The socket 13 has an internal lip 15 around its mouth. An annular locking ridge 16 is formed on an inner circumferential wall surface 17 of the socket, axially spaced a short distance from the lip 15. The spigot 11 has an outer circumferential wall surface 18 of smaller diameter than the internal diameter of the lip 15 so that the spigot fits into the socket with clearance from the lip. The gasket is appreciably shorter axially than the depth of the socket 13.

In order to make the joint the gasket is located as a radially close fit inside the socket 13 of the second pipe 14 so that the annular groove 8 at its holding portion 7 is engaged by the locking ridge 16 in the socket and the outer end 4 of the body 2 abuts against the inside of the lip. The thickness of the holding portion at the outer end 4 is contained within the radial extent of the lip, whereas because of its greater thickness the sealing portion extends radially inwardly appreciably further than the lip.

In the illustrated example the gasket occupies only about half of the depth of the socket. Having located the gasket in the socket, the spigot 11 of the first pipe is then inserted into the socket 13 of the second pipe 14 through the gasket. The end of the spigot is chamfered to ease the insertion. Because of the thickness of the sealing portion the spigot has interference engagement with that portion as it is pushed through the gasket and so the sealing portion is resiliently enlarged internally and is also urged outwardly to become tightly compressed between the inner circumferential wall surface 17 of the socket and the outer circumferential wall surface 18 of the spigot. Thus a good effective seal is provided by the gasket between the spigot and the socket.

Interengagement of the locking ridge 16 and groove 8 restrains the gasket from axial movement along the socket as the spigot is inserted into the socket through the gasket. The depth of the socket allows for some variation in the extent to which the spigot is inserted into the socket. It is important that the spigot is inserted at least sufficiently to project through the gasket.

When the pipes are in use pressure will be exerted on the inner end of the gasket by the flow of contents through the pipes. This pressure urges the gasket outwardly of the socket but the stiffening of the holding portion by the spring and the abutment of the outer end 4 against the lip effectively and reliably restrains the gasket from being blown out of the socket.

The jointing gasket of Figures 2 and 3, generally indicated at 40, has an annular body 41 which is axially extended, is tapered in its crosssection from one, inner, end 42 to its opposite, outer, end 43 and has an annular helically coiled spring 44 contained within its thickness adjacent to the outer end 43. Part of the axial length of the body 41 extending from the inner end 42 forms a sealing portion 45 and part of its axial length extending from the outer end 43 forms a holding portion 46 which contains the spring 44. The inner end 42 is formed in two lobes 47, 48 and the outer end 43 is substantially squared. There is a gradual taper in the thickness of the body from the inner end 42 through the sealing portion 45 and holding portion 46 to the outer end 43, a radially outer surface 49 of the body being substantially cylindrical and a radially inner surface 50 being outwardly flared from the inner end 42 to the outer end 43 to provide the tapering thickness of the body. An annular groove 51 is formed in the radially outer surface 49 at the holding portion intermediate where the spring 44 is contained and the sealing portion 45.

The inner surface 50 of the gasket is coated with a low friction coating.

The radial thickness of the sealing portion 45 is greater than the distance between an outer circumferential wall surface of the spigot of a pipe with which the jointing gasket is designed to be used and an inner circumferential wall surface of a socket of a pipe to which the spigot of the one pipe is to be joined. At the holding portion the radial thickness is less than that distance.

The body is made of a resilient elastomeric material such as natural or synthetic rubber. It is moulded to shape. Prior to the moulding operation the spring 44, which is of suitable spring metal, is located in its annular form in the mould. The elastomeric material is then introduced into the mould so that the spring becomes fully embedded in the material at the holding portion of the moulded body. Whereas the sealing portion 45 is resilient, the presence of the spring 44 in the holding portion 46 stiffens that part of the body so that it has substantial resistance to deformation.

For use the gasket may be fitted for example, as shown, to seal the joint between a cylindrical spigot 55 of a first pipe 56 and a belled socket 57 of a second pipe 58. The socket 57 has an internal lip 59 around its mouth. An annular locking ridge 60 is formed on an inner circumferential wall surface 61 of the socket, axially spaced a short distance from the lip 59. The spigot 55 has an outer circumferential wall surface 62 of smaller diameter than the internal diameter of the lip 59 so that the spigot fits into the socket with clearance from the lip. The gasket is appreciably shorter axially than the depth of the socket 57.

In order to make the joint the gasket is located as a radially close fit inside the socket 57 of the second pipe 58 so that the annular groove 49 at its holding portion 46 is engaged by the locking ridge 60 in the socket and the outer end 43 of the body 41 abuts against the inside of the lip. The thickness of the holding portion at the outer end 43 is contained within the radial extent of the lip, whereas because of its greater thickness the sealing portion extends radially inwardly appreciably further than the lip. In this example the gasket occupies only about half of the depth of the socket. Having located the gasket in the socket, the spigot 55 of the first pipe 56 is then inserted into the socket 57 of the second pipe 58 through the gasket. The end of the spigot is chamfered and the inner surface 50 of the gasket coated to ease the insertion. The diameter of the sealing portion of the gasket is greater than the inner diameter of the socket (at surface 49). There is therefore an interference fit between the lobe 48 of the sealing portion and the surface 49 of the socket. In addition, because of the thickness of the sealing portion the spigot has interference engagement with that portion as it is pushed through the gasket and so the lobe 47 of the sealing portion is pushed radially outwards towards the lobe 48 and the sealing portion is also urged outwardly to become tightly compressed between the inner circumferential wall surface 61 of the socket and the outer circumferential wall surface 62 of the spigot. The lobes 47, 48 are designed so as to create a lip seal in addition to the compression seal formed as above. Thus a good effective seal is provided by the gasket between the spigot and the socket.

Interengagement of the locking ridge 60 and groove 49 restrains the gasket from axial movement along the socket as the spigot is inserted into the socket through the gasket. The depth of the socket allows for some variation in the extent to which the spigot is inserted into the socket. It is important that the spigot is inserted at least sufficiently to project through the gasket.

When the pipes are in use pressure will be exerted on the inner end of the gasket by the flow of contents through the pipes. This pressure urges the gasket outwardly of the socket but the stiffening of the holding portion by the spring and the abutment of the outer end 43 against the lip 59 effectively and reliably restrains the gasket from being blown out of the socket.

Claims

1. A jointing gasket for a spigot and socket pipe joint comprising a body of elastomeric material which is axially extended and has a sealing portion extending for part of its axial length from one end and a holding portion extending for another part of its axial length from the other end, the sealing portion being resilient and of a radial thickness greater than the distance between an outer circumferential wall surface of the spigot on which the gasket is adapted to be fitted for use and an inner circumferential wall surface of the socket into which the spigot is to be received at the pipe joint, so as to be under radial compressive force when engaged between the two wall surfaces, and the holding portion having a radial thickness less than the distance between the said wall surfaces and containing within its thickness a holding ring which affords resistance to deformation of the holding portion.

2. A jointing gasket according to claim 1, wherein the holding ring has some resilience.

3. A jointing gasket according to claim 1 or claim 2, wherein the holding ring is in the form of a helically coiled spring extending annularly in the holding portion.

4. A jointing gasket according to claim 3, wherein the spring is embedded in the holding portion as the body of the gasket is formed.

5. A jointing gasket according to claim 3, wherein the spring is embedded in the holding portion by moulding.

6. A jointing gasket according to any of claims 3 to 5, wherein the spring occupies a substantial part of the thickness of the holding portion.

7. A jointing gasket according to any preceding claim, wherein the body is made of a rubber or a mouldable polymeric material.

8. A jointing gasket according to any preceding claim, wherein the body of the gasket tapers in thickness gradually from the resilient portion end to the holding portion end.

9. A jointing gasket according to any preceding claim, wherein the gasket is adapted to be used with a pipe socket which has an internal lip at its outer end, the gasket being adapted to be fitted on the socket for the holding portion to abut against the inside of the lip.

10. A jointing gasket according to any preceding claim, wherein the gasket is adapted to be used with a pipe socket which has a locking formation at its inner circumferential wall surface to locate the gasket axially in the socket, the body of the gasket having a complementary formation adapted to co-operate with the locking formation.

11. A jointing gasket according to claim 10, wherein the complementary formation comprises a ridge or ridges and the other adapted for co-operation with a groove or grooves of the socket.

12. A jointing gasket according to claim 10, wherein the complementary formation comprises a groove or grooves adapted for co-operation with a ridge or ridges of the socket.

13. A jointing gasket according to any preceding claim, wherein one or more surfaces of the gasket are coated with a low friction coating.

14. A spigot and socket pipe joint including a jointing gasket in accordance with any of claims 1 to 13 fitted between an outer circumferential wall surface of the spigot and an inner circumferential wall surface of the socket to seal the joint.

15. A jointing gasket substantially as described herein, with reference to the accompanying drawings.

16. A spigot and socket pipe joint substantially as described herein, with reference to the accompanying drawings.