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Patent Searching and Data


Title:
A PIPE FORMING ASSEMBLY
Document Type and Number:
WIPO Patent Application WO/2005/095095
Kind Code:
A1
Abstract:
A method of forming a tubular conduit comprises providing first and second ring moulds (14, 16). A plurality of generally flat wall members (12) provide inner (22) and outer (20) liners for the tubular conduit. The method comprises deforming the wall members (12) to provide tubular members (20, 22), arranging the tubular members (20, 22) to extend between the first and second ring moulds (14, 16) to define an annular space therebetween and disposing a curable material (18) in the annular space to provide a core layer between the inner and outer liners (20, 22). A tubular conduit formed by such a method is also claimed.

Inventors:
BOATMAN PETER JAMES (GB)
Application Number:
PCT/GB2005/001210
Publication Date:
October 13, 2005
Filing Date:
March 29, 2005
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
BOATMAN PETER JAMES (GB)
International Classes:
B28B21/20; B29C53/40; B32B1/08; F16L9/08; F16L9/12; F16L9/17; (IPC1-7): B32B1/08; B29C53/48; F16L9/08; F16L9/12; F16L9/17
Domestic Patent References:
WO2000035664A12000-06-22
Foreign References:
US3217077A1965-11-09
US3066063A1962-11-27
Attorney, Agent or Firm:
Lock, Howard (48 Friar Gate, Derby DE1 1GY, GB)
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Claims:
CLAIMS
1. A method of forming a tubular conduit comprising providing first and second ring moulds, providing a plurality of generally flat wall members to provide inner and outer liners for the pipe, deforming the wall members to provide tubular members, arranging the tubular members to extend between the first and second ring moulds to define an annular space between the tubular members, and disposing a curable material in the annular space to provide a core layer between the inner and outer liners.
2. A method according to claim 1 wherein the tubular liners are cylindrical.
3. A method according to claim 1 or 2 wherein a vacuum means is applied to the region between the, or each, flexible member and the wall member to reduce the pressure between the, or each, flexible member and the wall member, and curing material or hardener is disposed on to the resin material to cure the resin material.
4. A method according to claim 1 , 2 or 3, wherein the inner and outer liners are arranged to extend between the first and second ring moulds, such that the inner liner is arranged adjacent to the outer liner to define a core space therebetween to receive the curable material, and the curable material is disposed in the core space between the inner and outer liners.
5. A method according to any preceding claims, wherein directing means, is provided to direct the curable material into the core space, the directing means comprising a conical or frusto conical member to direct the curable material into the core space, and the directing means further including an insertion member for insertion within the inner liner.
6. A method according to claim 5, wherein a securing member secures the directing means to the first ring mould, the securing means comprises an elongate member, threaded at an upper region thereof, and a bolt to attach the directing means to the securing member.
7. A method according to any preceding claims, wherein opposite edges of the wall members are secured together by a resin transfer process.
8. A method according to claim 7, wherein the wall members are arranged such that opposite edges are adjacent each other, a flexible member is arranged to cover said adjacent opposite edges, a securing material is provided between the flexible member and the wall member, the flexible member is arranged on one surface of the wall member, and the securing material is impregnated with a curable resin material.
9. A method according to claim 8, wherein a further flexible member is arranged on the opposite surface of the wall member, and further resin material is provided between the further flexible member and the wall member.
10. A method according to any preceding claim, wherein the second ring mould comprises a first part to locate the outer liner in its desired position, the first part being a lower part and comprising a locating portion for insertion into the outer liner to engage and locate the outer liner.
11. A method according to claim 10, wherein the second ring mould further includes a second part, to form a groove for a sealing member, the second part projecting inwardly into the core space to provide a recess in the core material.
12. A method according to claim 11 , wherein the second ring mould comprises a third part configured to provide a further portion of the spigot in the core material, the third part being an upper part and comprising means for receiving location elements to locate the inner liner relative to the outer liner, the means for receiving the location elements comprising apertures defined in the third part.
13. A method according to any preceding claim, wherein the assembly comprises support means to be provided within the inner tubular liner during formation of the tubular conduit.
14. A method according to claim 13, wherein the support means is provided to prevent collapse of the inner tubular liner when the curable material is received between the inner and outer liners.
15. A method according to claims 13 or 14, wherein the support means comprises an annular inflatable member, the inflatable member being inflatable to provide support for the inner liner when the curable material is received in the space between the inner and outer liners.
16. A method according to claims 13, 14 or 15, wherein the support means comprises an annular inflatable bag, the bag having a central hole through which the securing member can extend.
17. A method according to any of claims 13 to 16, wherein the support means comprises an annular inflatable tubular member, the tubular member being toroidal in configuration.
18. A method according to claim 17, wherein retaining means is provided to retain the tubular member, the retaining means comprising a holding member, comprising a tube receiving portion.
19. A method according to claim 18, wherein the holding member has a generally C shaped profile, to hold the tubular member.
20. A tubular conduit comprising first and second tubular liners arranged concentrically of one another and a cured material arranged between the liners, wherein the tubular conduit further includes first and second opposite coupling arrangements, arranged at respective opposite end regions of the pipe. The coupling arrangements are provided to couple the pipe to adjacent identical or similar tubular conduit at the aforesaid opposite end regions.
21. A tubular conduit according to claim 20 wherein a first end region of the tubular conduit includes at least a part of an external joint, comprising an outer socket portion to couple the tubular conduit to an adjacent similar or identical tubular conduit, the outer socket portion being a radially outer socket portion and being provided by the outer liner extending axially beyond a main portion of the core layer.
22. A tubular conduit according to claim 21 , wherein a second end region of the tubular conduit, which is opposite said first end region, includes at least a part of an external joint, said external joint comprising an outer spigot portion to couple the tubular conduit to an adjacent similar or identical tubular conduit, the outer spigot portion being a radially outer spigot portion and having a radially outer facing surface provided by the core layer extending beyond the outer liner.
23. A tubular conduit according to claim 22, wherein one of said first and second end regions of the tubular conduit includes at least a part of an internal joint, said internal joint comprising an inner socket portion to connect the tubular conduit to an adjacent similar or identical tubular conduit, the inner socket portion being a radially inner socket portion, and having a radially inner facing surface, the inner socket portion being provided on the core layer extending beyond the inner liner.
24. A tubular conduit according to claim 23, wherein the other of the first and second end regions of the tubular conduit includes at least a part of an internal joint, comprising an inner spigot portion to connect the tubular conduit to an adjacent, similar or identical tubular conduit, the inner spigot portion being a radially inner spigot portion, and having a radially outer facing surface, the inner spigot portion extending beyond the core layer and is provided by the inner liner.
25. A tubular conduit according to claim 24, wherein the outer socket portion comprises an annular coupling member formed of a nonplastics material, preferably a metallic material, such as stainless steel.
26. A tubular conduit according to any of claims 21 to 25 wherein a first end region of the tubular conduit includes at least part of an external joint comprising a socket portion to couple the pipe to an adjacent, similar or identical tubular conduit, the socket portion being a radially outer socket portion and comprising a coupling member extending beyond a main portion of the core layer.
27. A tubular conduit according to claim 25 wherein a sealing member is provided, the sealing member being expandable on absorption of water, and being an endless annular member.
28. A tubular conduit according to claim 27 wherein the sealing member is formed of hydrofluoric rubber.
29. A tubular conduit according to claim 29, wherein, the coupling member is formed of a nonplastics material, and a recess is defined in the core layer to receive the sealing member, the recess being a groove, adjacent the coupling member, the sealing member being provided in the recess and engages the coupling member, to seal against the coupling member.
30. A tubular conduit according to claim 26, wherein a second end region of the tubular conduit comprises a spigot portion to be received by the socket portion, the spigot portion comprising an axially extending portion of the inner liner extending beyond the main portion of the core layer.
Description:
Tubular Conduits

This invention relates to tubular conduits, and to assemblies and methods for forming tubular conduits. Embodiments of this invention relates to pipe forming assemblies. This invention also relates to methods of forming pipes, and to pipes.

In order to transport liquids across significant distances, pipelines are often used. In order to lay or repair the pipeline, one way is to provide the materials for making the pipe and form the pipe on site. However, this method has disadvantages associated with transportation among other problems.

According to one aspect of this invention there is provided a tubular conduit forming assembly comprising first and second ring moulds, a plurality of wall members to provide inner and outer liners for the tubular conduit and a curable material to provide a core layer between the inner and outer liners.

According to another aspect of this invention there is provided a method of forming a tubular conduit comprising providing first and second ring moulds providing a plurality of wall members to provide inner and outer liners for the tubular conduit, the liners comprising tubular members, arranging the tubular members to extend between first and second ring moulds to define an annular space between the tubular members, and disposing a curable material in the annular space to provide a core layer. The method may comprise allowing the curable material to cure to form a solid or substantially solid core.

According to another aspect of this invention there is provided a tubular conduit forming assembly comprising first and second ring moulds, a plurality of generally flat wall members to provide inner and outer liners for the pipe, and a curable material to provide a core layer between the inner and outer liners. Preferably, the wall members are deformable to provide tubular liners. The tubular liners may be cylindrical.

According to another aspect of this invention there is provided a method of forming a tubular conduit comprising providing first and second ring moulds, providing a plurality of generally flat wall members to provide inner and outer liners for the pipe, deforming the wall member to provide tubular member, arranging the tubular members to extend between the first and second ring moulds to define an annular space between the tubular members, and disposing a curable material in the annular space to provide a core layer between the inner and outer liners. The method may comprise allowing the curable material to cure to form a solid or substantially solid core.

Opposite edges of the wall members may be secured together by suitable securing means, for example, by the use of a resin. Opposite edges may be secured together by a resin transfer process, for example resin transfer moulding. Conveniently, the edges are secured together by vacuum assisted resin transfer moulding. Alternatively, the opposite edges can be secured together by a hand lay up process.

The wall member may be arranged such that opposite edges are adjacent each other. A flexible member may be arranged to cover said adjacent opposite edges. A securing material may be provided between the flexible member and the wall member. The flexible member may be arranged on one surface of the wall member. The securing material may comprise a sheet. The sheet may be impregnated with a resin material, which may be curable. The sheet may comprise a mat, cloth or roving, which may be formed of a fibre material, such as glass fibre. In this embodiment, the resin binds the fibres together.

A further flexible member may be arranged on the opposite surface of the wall member. Further resin material may be provided between the further flexible member and the wall member. In one embodiment, a vacuum means may be applied to the region between the, or each, flexible member and the wall member to reduce the pressure between the, or each, flexible member and the wall member. A curing material or hardener may be disposed, for example by injection, on to the resin material to cure the resin material. The curing material may be mixed with the resin material and the mixture may be injected onto the fibrous sheet, desirably to wet, and preferably to impregnate, the fibres.

The, or each, flexible member may be removed when the resin material has hardened.

The inner and outer liners may be arranged to extend between the first and second ring moulds, such that the inner liner is arranged adjacent to the outer liner to define a core space therebetween to receive the curable material. Desirably, the inner liner is arranged within the outer liner to define the core space therebetween. Preferably, the space has an annular profile and is conveniently cylindrical in configuration. The curable material may be disposed in the core space between the inner and outer liners. Preferably, the curable material is disposed in the core space by pouring.

The first ring mould may comprise a base ring mould. The second ring mould may comprise a top ring mould.

Directing means, may be provided to direct the curable material into the core space. The directing means may comprise a conical or frusto concial member to direct the curable material into the core space. The directing means may further include an insertion member for insertion within the inner liner. The insertion member may be substantially cylindrical in configuration. A securing member may secure the directing means to the first ring mould. The securing means may comprise an elongate member, which may be threaded, preferably at an upper region thereof. A bolt may be provided to attach the directing means to the securing member. The second ring mould may comprise a first part to locate the outer liner in its desired position. The first part may be a lower part and may comprise a locating portion for insertion into the outer liner to engage and locate the outer liner. The first part conveniently has a shape to form a spigot in the core material.

The second ring mould may further include a second part, which may form a groove for a sealing member. The second part may be a middle part. Preferably, the middle part projects inwardly into the core space to provide a recess in the core material. The second part may be in the form of a split ring.

The second ring mould may comprise a third part which may be configured to provide a further portion of the spigot in the core material. The third part may be an upper part and may comprise means for receiving location elements to locate the inner liner relative to the outer liner. The location elements may be threadable and may comprise location screws. The means for receiving the location elements may comprise apertures defined in the third part. The third part may comprise an upper part.

The assembly may comprise support means to be provided within the inner tubular liner during formation of the tubular conduit.

According to another aspect of this invention there is provided a tubular conduit forming assembly comprising first and second ring moulds, a plurality of wall members to provide inner and outer liners for the tubular conduit, a curable material to provide a core layer between the inner and outer liners, and support means to be provided within the inner liner during formation of the tubular conduit.

According to another aspect of this invention there is provided a method of forming a tubular conduit comprising providing first and second ring moulds providing a plurality of wall members to provide inner and outer liners for the tubular conduit, the liners comprising tubular members, arranging the tubular members to extend between the first and second ring moulds to define an annular space between the tubular members, providing a support means within the tubular member formed by the inner liner, and disposing a curable material in the annular space to provide a core layer between the inner and outer liners, and allowing the curable material to cure to form a solid or substantially solid core, wherein the support means supports the inner liner when the core is being formed.

The support means may be provided to prevent collapse of the inner tubular liner when the curable material is received between the inner and outer liners.

The support means may comprise an inflatable member. The inflatable member is preferably inflatable to provide support for the inner liner when the curable material is received in the space between the inner and outer liners. The support means may be deflated after the curable material has cured in the core space.

The support means may comprise an inflatable bag which may be annular. The bag may have a central hole through which the securing member can extend. Preferably the bag is of a cylindrical configuration.

Alternatively, or in addition, the support means may comprise an annular tubular member. The tubular member may be toroidal in configuration. The tubular member may be inflatable. Retaining means may be provided to retain the tubular member. The retaining means may comprise a holding member, comprising a tube receiving portion. The holding member may have a generally C shaped profile, which may hold the tubular member.

The curable material may comprise a reinforced polymeric material, preferably a polymer concrete. The curable material may be a corrosion resistant material, or may provide a corrosion resistant material when cured.

Each wall member, and hence each liner, may have a thickness in the range of 1 Vz to 2 mm. Preferably, a plurality of wall members are provided in the pipe forming assembly in a predetermined size. The wall members may be cut to said predetermined size.

The tubular conduit may comprise first and second opposite coupling arrangements, arranged at respective opposite end regions of the pipe. The coupling arrangements are provided to couple the pipe to adjacent identical or similar tubular conduit at the aforesaid opposite end regions.

In a first embodiment, first end region of the tubular conduit may include at least a part of an external joint, which may comprise an outer socket portion to couple the tubular conduit to an adjacent similar or identical tubular conduit. The outer socket portion may be a radially outer socket portion and may be provided by the outer liner extending axially beyond a main portion of the core layer. The outer liner may have a radially inner facing surface. Preferably, the outer socket portion is configured to receive a corresponding outer spigot portion on the adjacent tubular conduit.

In the first embodiment, a second end region of the tubular conduit which is preferably opposite said first end region, may include at least a part of an external joint, which may comprise an outer spigot portion to couple the tubular conduit to adjacent similar or identical tubular conduit. The outer spigot portion may be a radially outer spigot portion and may have a radially outer facing surface, which may be provided by the core layer extending beyond the outer liner. Preferably, the outer spigot portion is configured to be received by a corresponding outer socket portion on the adjacent tubular conduit.

In the first embodiment, one of said first and second end regions of the tubular conduit may include at least a part of an internal joint, which may comprise an inner socket portion to connect the tubular conduit to an adjacent similar or identical tubular conduit. The inner socket portion may be a radially inner socket portion, and may have a radially inner facing surface. The inner socket portion may be provided on the core layer extending beyond the inner liner. Preferably, the inner socket portion is configured to receive a corresponding inner spigot portion of an adjacent tubular conduit.

In the first embodiment, the other of the first and second end regions of the tubular conduit may include at least a part of an internal joint, which may comprise an inner spigot portion to connect the tubular conduit to an adjacent, similar or identical tubular conduit. The inner spigot portion may be a radially inner spigot portion, and may have a radially outer facing surface. The inner spigot portion may extend beyond the core layer and may be provided by the inner liner. Preferably the inner spigot portion is configured to be received by an inner socket portion on the adjacent tubular conduit.

The outer socket portion may comprise a coupling member which may be formed of a non-plastics material, preferably a metallic material, such as stainless steel. The coupling member is preferably annular.

Each wall member may comprise a plurality of laminations and each lamination may be formed of a plastics material, for example a fibre material, such as glass fibre and a resin material; the resin material is preferably impregnated on the fibre material. The outer laminations of each wall member may comprise a hardening prevention material, to prevent the laminations adjacent thereto from hardening. The outer laminations may comprise a film material, for example a synthetic film.

In a second embodiment, a first end region of the tubular conduit may include at least part of an external joint, which may comprise a socket portion to couple the pipe to an adjacent, similar or identical tubular conduit. The socket portion may be a radially outer socket portion and may comprise a coupling member extending beyond a main portion of the core layer. Some of the material forming the core layer may also be provided in axial extension beyond said main portion of the core layer. A portion of the outer liner may extend axially beyond the main portion of the core layer. A sealing member may be provided. The sealing member may be expandable on absorption of water. The sealing member may be an endless member, and may be annular in configuration. The sealing member may be expandable, preferably on contact with water or other liquids. Preferably, the sealing member can absorb water or other liquids to expand. The sealing member may be formed of a hydrofluoric rubber. This has the advantage, in the preferred embodiment of absorbing water thereby expanding to prevent the leakage of water past the sealing member.

The coupling member is preferably formed of a non-plastics material, preferably a metallic material such as stainless steel. A recess may be defined in the core layer to receive the sealing member. The recess may be a groove, conveniently an annular groove. The recess may be provided adjacent the coupling member. The sealing member may be provided in the recess and advantageously engages the coupling member, preferably to seal against the coupling member.

Preferably, the sealing member is held in the recess and on absorption of water or other liquids pushes against the coupling member to seal against the coupling member.

In the second embodiment, a second end region of the tubular conduit comprises a spigot portion to be received by the socket portion. The spigot portion may comprise an axially extending portion of the inner liner extending beyond the main portion of the core layer. Some of the material of the core layer may also be provided in axial extension beyond said main portion of the core layer.

A recess may be defined in the spigot portion for receiving a seal element. The recess may be a groove, conveniently an annular groove. The seal element may be annular and may comprise an O-ring seal. The seal element may have a circular profile, or may have a profile of another shape. According to another aspect of this invention there is provided a tubular conduit comprising a main body formed of at least one plastics material, a coupling member to couple the pipe to an adjacent pipe, the coupling member being formed of a non-plastics material and pipe further comprising a sealing member provided between the coupling member and the main body.

According to another aspect of this invention there is provided a method of forming a tubular conduit comprising forming a main body from at least one plastics material, providing a coupling of a non plastics material over the main body to couple the pipe to an adjacent pipe, and providing a sealing member between the coupling member and the main body.

The method of forming the tubular conduit may comprise some or all of the steps for forming the tubular conduit as described above.

The tubular conduit may comprise inner and outer liners, which may comprise tubular members. A core space may be defined between the tubular members. The pipe may comprise a core material in the core space. The core material may be formed from a curable material and may comprise a polymer concrete.

The coupling member may be formed of a metallic material such as stainless steel.

In a first embodiment, a first end region of the tubular conduit may include at least a part of an external joint, which may comprise an outer socket portion to couple the pipe to an adjacent similar or identical tubular conduit. The outer socket portion may be a radially outer socket portion and may be provided by the outer liner extending beyond the core layer. The outer liner may have a radially inner facing surface. Preferably, the outer socket portion is configured to receive a corresponding outer spigot portion on the adjacent tubular conduit. In the first embodiment a second end region of the tubular conduit which is preferably opposite said first end region, may include at least a part of an external joint, which may comprise an outer spigot portion to couple the pipe to adjacent similar or identical tubular conduit. The outer spigot portion may be a radially outer spigot portion and may have a radially outer facing surface, which may be provided by the core layer extending beyond the outer liner. Preferably, the outer spigot portion is configured to be received by a corresponding outer socket portion on the adjacent tubular conduit.

One of said first and second end regions of the tubular conduit may include at least a part of an internal joint, which may comprise an inner socket portion to connect the pipe to an adjacent similar or identical tubular conduit. The inner socket portion may be a radially inner socket portion, and may have a radially inner facing surface. The inner socket portion may be provided on the core layer extending beyond the inner liner. Preferably, the inner socket portion is configured to receive a corresponding inner spigot portion of an adjacent tubular conduit.

The other of the first and second end regions of the tubular conduit may include at least a part of an internal joint, which may comprise an inner spigot portion to connect the pipe to an adjacent, similar or identical tubular conduit. The inner spigot portion may be a radially inner spigot portion, and may have a radially outer facing surface. The inner spigot portion may extend beyond the core layer and may be provided by the inner liner. Preferably the inner spigot portion is configured to be received by an inner socket portion on the adjacent tubular conduit.

In a second embodiment, a first end region region of the tubular conduit may include at least part of an external joint, which may comprise a socket portion to couple the pipe to an adjacent similar or identical tubular conduit. The socket portion may be a radially outer socket portion and may comprise the coupling member, which may extend beyond a main portion of the core layer. Some of the material forming the core layer may also be provided in axial extension beyond said main portion of the core layer. A portion of the outer liner may extend axially beyond the main portion of the core layer.

A sealing member may be provided. The sealing member may be expandable on absorption of water. The sealing member may be an endless member, and may be annular in configuration. The sealing member may be formed of a hydrofluoric rubber. A recess may be defined in the core layer to receive the sealing member. The recess may be a groove, conveniently an annular groove.

In the second embodiment, a second end region of the tubular conduit comprising a spigot portion to be received by the socket portion. The spigot portion may comprise an axially extending portion of the inner liner extending beyond the main portion of the core layer, some of the material of the core layer may also be provided in axial extension beyond said main portion of the core layer.

A recess may be defined in the spigot portion for receiving a seal element. The recess may be a groove, conveniently an annular groove. The seal element may be annular and may comprise an O-ring seal.

The sealing member may be provided externally around the core layer, and may engage the outer socket portion of the adjacent pipe to provide a seal against the outer socket portion of the pipe. The sealing member may be an endless member, and may be annular in configuration. The sealing member may be formed of a hydrofluoric rubber.

The sealing member may be provided during casting. A groove may be formed in the core layer, in which the sealing member is received.

In one embodiment the sealing layer may be formed so as to absorb water, and may expand by the absorption of said water to seal against the said outer socket portion. A sealing element may be provided externally around the core layer at the opposite end of the pipe to sealingly engage the outer socket portion of an adjacent pipe. The further sealing element may be a rubber member, which may be annular in configuration. The sealing layer may be formed so as to absorb water and may expand by the absorption of said water to seal against the outer socket portion of an adjacent tubular conduit.

The tubular conduit preferably comprises a pipe.

Embodiments of the invention will now be described by way of example only, with reference to the accompanying drawings, in which:

Fig. 1 is a diagrammatic view of a tubular conduit forming assembly;

Fig. 2 shows wall members formed into inner and outer liners;

Fig. 3 is a diagrammatic view showing opposite edge regions of a wall member being attached to each other.

Fig. 4 is a sectional view of apparatus for forming a tubular conduit;

Fig. 5 is a sectional side view one embodiment of a tubular conduit;

Fig. 5 is a sectional side view of another embodiment of a pipe showing the pipe connected to axially adjacent pipe;

Fig. 6 is a sectional side view of another embodiment of a pipe; and

Fig. 7 is a sectional side view of an end region of the pipe shown in Fig. 6 connected to an axially adjacent pipe.

Fig. 8 is a close up view showing two pipes connected together. Referring to the drawings, Fig. 1 shows a tubular conduit forming assembly in the form of a pipe forming assembly 10 comprising a pair of generally flat wall members generally designated 12, and which are specifically designated 12A and 12B respectively; because each of which has opposite edges 24, 26, and can be deformed to form cylindrical tubular members, and used as the inner and outer liners of a tubular member in the form of a pipe, as explained below. The assembly 10 also includes first and second ring moulds 14, 16 which can be arranged so that the inner and outer liners extend from the first ring mould 14 to the second ring mould 16, and a curable material 18 can be arranged between the inner and outer liners to provide a core layer of the pipe. The ring moulds 14, 16 and the curable material 18 are shown schematically in Fig. 1.

Referring to Figs. 2, 3, and 4 an outer liner 20 (formed from the wall member 12A) and an inner liner 22 (formed from the wall member 12B) are shown. The outer liner 20, and the inner liner 22 are each formed from the respective wall members 12A and 12B, by securing together the opposite edges 24, 26 to provide respective tubular members. The opposite edges 24, 26 of each respective wall member 12 are secured to each other by a suitable known technique, for example a vacuum assisted resin transfer moulding technique, to provide cylindrical liners 20, 22.

Referring to Fig. 3 there is shown a diagrammatic view showing opposite end regions, 24, 26 being attached to each other by a vacuum assisted resin transfer moulding technique. The edge regions 24, 26 are brought together by bending the wall member 12 into liner 20 or 22 of a cylindrical tubular configuration. When the edges 24, 26 have been brought together, a flexible member in the form of a first flexible layer of a release film 30 or bag is located on the now inner surface 32 of the liner 20 or 22. A first layer 34 of a glass fibre material is then disposed on the inner surface 32, spanning across the edge region 24, 26, and between the release film 30 and surface 32. A second flexible layer of a release film 36 is arranged across the edge regions 24, 26 on the outer surface 38 of the liner 20 or 22 and a second layer of a glass fibre material 38 is located between the second layer of the release film 32 and the outer surface 38, such that the second layer of the glass fibre material spans across the two edge regions 24, 26.

A vacuum applying apparatus (not shown) is then applied to the region between the two release films 30, 36 so that they press against the respective layers 34, 38 of the glass fibre material. A hardener is then injected onto the layers of the glass fibre material 34, 38 causing the layers to cure and harden and attach together the two edge regions 24, 26. The release films 30, 36 can then be removed.

Referring particularly to Fig 4, which shows the apparatus 39 for forming the pipe, the liners 20, 22 are arranged such that the inner liner 22 is within the outer liner 20 to define an annular cylindrical core space 28 therebetween into which the curable material 18 can be poured by a suitable pouring device (not shown).

The apparatus 39 comprises a directing means 40 for directing the core material into the core space 28. The core material is suitably a polymer concrete material which can be poured into the core space 28 and then hardens, conveniently under the action of a hardener or curing agent.

The directing means 40 comprises a conical member 42 which is arranged on the inner liner 22 and extends over the core space 28. The directing means 42 also includes an annular insertion member 44, which is received inside the inner liner 22 and engages the inner surface thereof. An annular shoulder portion 46 engages the tope edge of the inner liner 22.

The directing means is secured to the base ring mould 14 by an elongate member in the form of a bar 48 which is threaded at its upper end, and may be threaded at its lower end. The bar 48 is fixedly or threadably connected to the base ring mould 14 and extends upwardly through a hole in the top of the conical member 42. The upper region of the rod 48 is threaded and a nut 50 is screwed thereon.

A plurality of elongate support members 52 in the form of rods extend upwardly from the base mould 14 and the second or top ring mould 16 is mounted on the upper ends of the support members 52. The preferred embodiment has four support rods 52.

The top ring mould 16 is formed of a plurality of components, and comprises a lower mould member 54 which comprises an annular main portion 56 and an annular insertion portion 58. The lower mould member 54 is located on the upper edge of the outer liner 20 by the insertion of the insertion portion 58 into the outer liner 20 such that the insertion portion 58 engages the inner surface of the outer liner 20.

The top ring mould 16 further includes a central mould member 60 which extends radially inwardly of the lower mould member to define an annular groove (see Figs 6 and 7), which can receive an annular sealing member.

The central mould member 60 is in the form of a split ring that is split along its centre line. The polymer concrete has a tendency to shrink during the moulding process. Such shrinkage is in the region of 1 to 2mm. In order to accommodate such shrinkage, compression means 63 is provided to constrict the central mould member 60 if such shrinkage occurs. The compression means 63 may comprise a rubber washer or a spring, such as a steel spring.

An upper mould member 62 is provided on the central mould member 60, and is mounted radially outwardly of the inner surface of the central mould member 60, includes a locating formation 64 to locate screws 66 therein. The screws 66 are provided to secure the outer and inner liners 20, 22 in the desired position relative to each other. The inner liner 22 is supported on its inside by inflatable support means comprising an inflatable member, in the form of an inflatable generally cylindrical bag 68. The inflatable bag 68 defines a hole therethrough, through which the bar 48 extends. In one embodiment, the inflatable bay 68 is formed of a heavy duty rubber, such as used for inflatable boats, or is formed of a material comprising thermoplastic coated fibres, similar to the material used in children's bouncy castles.

Alternatively, or in addition the support means comprises a plurality of annular inflatable tubular members 70, which in one embodiment are similar in shape to the inner tube of a vehicle tyre. In another embodiment, the annular inflatable tubular members are formed of a heavy duty rubber, such as used for inflatable boats, or is formed of a material comprising thermoplastic coated fibres similar to the material used for children's bouncy castles.

The inflatable tubular members 70 are retained by retaining means 72 having a central portion 74 configured to allow the bar 48 to extend therethrough, or being mounted on the bar 48.

The retaining means 70 further includes a holding portion 76 on the central portion 74. The holding portion 76 is annular in configuration and has a cross-sectional profile which is generally C-shaped.

The inflatable bag 68 and/or the inflatable toroidal tubular members 70 are inflated to engage the inner surface of the inner liner 22 and hold the inner liner 22 in its position as shown in Fig 4.

The curable material 18 is allowed to cure in the annular space 28 and solidify to provide a core layer formed of a polymer concrete material. When the curable material has so solidified, the inflatable support means can be deflated and removed from within the inner liner 22. Referring to Fig. 5, there is shown a tubular member in the form of a pipe 79 formed by the method described above and comprises an outer liner 20, an inner liner 22 and a core layer 80 between the inner and outer liners 20, 22. The core layer 38 is formed of a suitable polymer concrete material.

The pipe 79 has a first end region 79A and an opposite second end region 79B. The pipe 79 is provided with suitable coupling means 80, 84 at the opposite end regions 79A, 79B thereof. The coupling means 82, 84 are provided to couple the pipe 79 in end to end relationship with identical or similar pipes (not shown) at each end of the pipe 79. The first coupling means 82 comprises an outer annular socket portion 86. The second coupling means 84 at the opposite end of the pipe 36 is provided with an annular outer spigot portion 88. It will be appreciated that the outer socket portion 86 can receive the inner spigot portion of an adjacent pipe at that end of the pipe. Similarly, the outer spigot portion 88 of the pipe 79 can be received in the outer socket portion of an adjacent pipe at the opposite end of the pipe 79. The outer socket portion 86 comprises an outer extension region 90, which is in the form of an axially extending region of the outer liner 20 which extends beyond the core layer 80. The inner spigot portion comprises a first extending region 92 of the core layer 28 extending beyond the outer liner 20.

The coupling means 40 also comprises an inner socket portion 94 comprising an inner axially extending region 95 of the core layer 80 which extends beyond the inner liner 22. If desired, and as shown in fig. 4, the inner socket portion 94 can include an internal layer of a liner material 96 which is provided around the second axially extending region 95 on the inner surface thereof, and is similar to the inner liner 22.

The opposite end region comprises an inner spigot portion 98 in the form of an inner extension region 100, which is in the form of an axially extending region of the inner liner 22 which extends beyond the core layer 28. The inner spigot portion 98 is received within the inner socket portion 96 of an adjacent pipe. Referring to Fig. 6 there is shown an embodiment in which the outer socket portion 86 is replaced by a stainless steel annular coupling member 102 provided externally around the inner axially extending region 95 of the core layer 80. The stainless steel member 102 is of an annular configuration and is sealed against the inner axially extending region 95 by a suitable seal, for example an annular seal 104 of a hydrofluoric rubber.

The polymer concrete from which the pipe 79 is formed may have a tendency to shrink. In order to accommodate such shrinkage constriction means 119 which may be in the form of a thick rubber washer or a spring is disposed around the steel member 102 to compress the steel member 102 as the shrinkage occurs.

The annular seal 104 is received in an annular groove 106 in the external circumferential surface of the inner axially extending region 95. The opposite end of the pipe 79 includes the outer spigot portion 82 which extends beyond the outer liner 20. A groove 108 is moulded into the external surface of the outer spigot portion 82 to receive a sealing ring 110, which may be the same as the sealing ring 104, and which formed of a hydrofluoric rubber.

In order to couple the pipe 79 to an adjacent pipe, the pipe 79 is arranged such that its first end region 79A is provided in mating engagement with the second end region 79B of an adjacent identical pipe 179, shown in broken lines and having the same features of the second end region 79B of the pipe 79. The stainless steel member 102 extends to the outer spigot portion 82 of the adjacent pipe 136 (shown in broken lines). The sealing members 104, 110 prevent the ingress or egress of water into or out of the pipe. The use of hydrofluoric rubber provides the advantage that the sealing members 104, 110 can absorb water and expand to enhance the sealing effect. The second end region 79B of the pipe 80 can be coupled to the first end region 79A of an adjacent pipe 279, in the same way as described above, utilising the coupling member 102 on the adjacent pipe 79A. Referring to Fig 7 and 8 there is shown a further embodiment of a pipe 79 comprising many of the features shown in Fig 6 and described above. These features have been designated with the same reference numeral.

The pipe 79 shown in Fig 7 comprises a first end portion 112. The first end portion forms and external joint with a similar pipe (see Fig 8) The first end 112 of the pipe 79 comprises a socket formed of an extending portion 114 and extending portion 116 of the core layer 80.

A steel coupling member 118 is provided on the core layer extending portion 116. Referring to Fig 8, an annular seal 120 formed of a hydrofluoric rubber is provided, which expands on absorption of water. The other end 122 of the pipe 79, comprises a spigot and is formed of an extending portion 124 of the inner liner 22 and an extending portion 126 of the core layer 80. The core layer extending portion 126 defines a groove 128 to receive a seal 130. Fig 8 shows the coupling of two pipes 79 to each other. The socket portion 112 of one of the pipes 79 receives the spigot portion 122 of the other of the pipes. The seal 130 is received in the groove 130 seals against the steel coupling member 118.

An annular cushioning member 132 is provided to cushion the two pipes against each other. The cushioning member 132 is used where the pipes are jacking pipes. A cushioning member may not be used for other types of pipes.

Various modifications can be made without departing from the scope of the invention. For example, in some embodiments, the hydrofluoric rubber may be attached by the resin. This problem can be overcome by providing a groove containing silicone or coating the hydrofluoric seal with a suitable resin resistant coating.

Whilst endeavouring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and/or shown in the drawings whether or not particular emphasis has been placed thereon.