Couplings

Abstract

A coupling component having a first end and a second end, the fitting having a longitudinal axis between the first end and the second end, the first end of the component including a first tubular portion having a first internal diameter adapted to form a sliding fit with a first pipe section, and a first sealer adapted such that the first end can be sealed in use to the first pipe section; the second end having a second diameter or cross-sectional area which is larger than the first diameter and wherein the second end incorporates a flange, wherein at least part of the face of said flange is in a plane substantially non-perpendicular to, or offset from, the longitudinal axis of the component.

Claims

1. A coupling assembly for forming a joint between a first secondary pipe section, a second secondary pipe section, and a third secondary pipe section, the coupling assembly accommodating a primary joint therein, in a secondary containment system, the coupling assembly comprising: a first coupling component having a first pipe-fit end, a second pipe-fit end, and a first joint end, the first coupling component having a first longitudinal axis between the first pipe-fit end and the first joint end, and a second longitudinal axis between the second pipe-fit end and the first joint end, the first pipe-fit end of the first coupling component including a first tubular portion having a first internal diameter sized and shaped to receive the first secondary pipe section, and a first sealer positioned such that the first pipe-fit end can be sealed in use to the first secondary pipe section; the second pipe-fit end of the first coupling component including a second tubular portion having a second internal diameter sized and shaped to receive the second secondary pipe section, and a second sealer positioned such that the second pipe-fit end can be sealed in use to the second secondary pipe section; and the first joint end of the first coupling component having a third internal diameter which is larger than the first internal diameter and the second internal diameter, and wherein the first joint end incorporates a first end face, wherein the first end face is in a plane that is at least one of substantially non-perpendicular to, and offset from, both the first longitudinal axis and the second longitudinal axis, and wherein the first joint end further includes a first mating region; and a second coupling component having a third pipe-fit end and a second joint end, the second coupling component having a third longitudinal axis arranged at an angle relative to at least one of the first longitudinal axis and the second longitudinal axis, the third pipe-fit end including a third tubular portion having a third internal diameter sized and shaped to form a sliding fit with the third secondary pipe section, and a third sealer positioned such that the third end can be sealed in use to the third secondary pipe section; and the second joint end of the second coupling component having a fourth internal diameter larger than the third internal diameter, and wherein the second joint end incorporates a second end face, wherein the second end face is in a plane that is at least one of substantially non-perpendicular to, and offset from, the third longitudinal axis, and wherein the second joint end further includes a second mating region sized and shaped to be sealed to the first mating region of the first coupling component.

2. A coupling assembly according to claim 1 wherein the second mating region extends from the second end face.

3. A coupling assembly according to claim 1 wherein the second mating region includes a flange.

4. A coupling assembly according to claim 3 wherein the flange extends radially from the plane of the second end face to define an annular portion or ring.

5. A coupling assembly according to claim 4 wherein the second end face includes both the second mating region and the flange such that the flange is an extension of the second end face.

6. A coupling assembly according to claim 3 wherein the flange extends axially from the plane of the second end face to define a cylindrical portion or ring.

7. A coupling assembly according to claim 6 wherein the flange defines a socket.

8. A coupling assembly according to claim 6 wherein the flange defines a spigot.

9. A coupling assembly according to claim 1 further including a mating seal sized and shaped to seal in use the first coupling component to the second coupling component.

10. A coupling assembly according to claim 1 wherein the first end face at the first joint end of the first coupling component is in a plane at substantially 45° to at least one of the first longitudinal axis and the second longitudinal axis of the first coupling component.

11. A coupling assembly according to claim 1 in which the assembly is generally tubular in configuration.

12. A coupling assembly according to claim 1 wherein the first pipe-fit end is in a plane substantially perpendicular to the first longitudinal axis of the first coupling component.

13. A coupling assembly as claimed in claim 1 wherein the first joint end is non-circular in cross-section.

14. A coupling assembly as claimed in claim 13 wherein the first joint end is substantially oval in shape.

15. A coupling assembly as claimed in claim 1 wherein the first sealer is selected from the group including: (i) an electrofusion heating element and associated electrical terminal connections; (ii) a bond or weld including a chemical bond or weld, an ultrasonic weld or a heat weld; (iii) a gasket seal together with a clamp; or a combination thereof.

16. A coupling assembly as claimed in claim 1 wherein at least one of the first mating region and the second mating region includes an electrofusion heating element and electrical terminal connections.

17. The coupling assembly according to claim 1, wherein the angle formed by the third longitudinal axis, and the second longitudinal axis is substantially 90°.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will now be described by way of example only with reference to the accompanying drawings wherein:

(2) FIG. 1 illustrates joining two secondarily contained pipes in a linear fashion using conventional fittings;

(3) FIG. 2 illustrates joining secondarily contained pipes in a T configuration using conventional fittings;

(4) FIG. 3 illustrates various methods of forming a 90° elbow in a secondarily contained pipe using conventional fittings;

(5) FIGS. 4 and 5 show coupling component according to a first embodiment of the present invention;

(6) FIG. 6 shows the coupling components of FIGS. 4 and 5 fitted together in a 90° elbow configuration;

(7) FIG. 7 shows the coupling components of FIGS. 4 and 5 fitted together in a linear configuration;

(8) FIGS. 8 and 9 illustrate the coupling components of FIGS. 4 and 5 assembled around a 90° elbow in an open position to allow welding and pressure testing of a primary 90° elbow fitting;

(9) FIGS. 10, 11 and 12 show the coupling components of FIGS. 8 and 9 in a closed or welded position;

(10) FIGS. 13 and 14 show the coupling components in a closed and open position respectively forming a linear or in-line joint;

(11) FIGS. 15A to D illustrate an embodiment of the invention applied to a T fitting;

(12) FIGS. 16 to 20 illustrate cutaway, plan elevation, expanded and assembled views respectively of a further embodiment of a T fitting;

(13) FIGS. 21, 22 and 23 illustrate expanded plan and perspective views and an assembled plan view of a further embodiment of a T fitting;

(14) FIGS. 24, 25 and 26 illustrate expanded plan and perspective views and an assembled plan view of a further embodiment of a T fitting;

(15) FIGS. 27, 28 and 29 illustrate expanded plan and perspective views and an assembled plan view of a further T fitting according to the present invention;

(16) FIGS. 30 and 31 illustrate a coupling in which the sealing means is a bolted gasket seal;

(17) FIGS. 32 and 33 illustrate cut away views of a coupling assembly for an elbow joint according to a further embodiment of the present invention;

(18) FIG. 34 illustrates a cross section cut away view of a coupling assembly for a T-joint according to a further embodiment of the present invention;

(19) FIGS. 35A to 35D illustrate an alternate construction of T-joint using the same socket and spigot arrangement as in FIG. 34;

(20) FIGS. 36A to 36D illustrate an alternate construction of T-joint using the same socket and spigot arrangement as in FIG. 34;

(21) FIGS. 37A to 37D illustrate an alternate construction of T-joint using the same socket and spigot arrangement as in FIG. 34; and

(22) FIGS. 38A to 38E illustrate an alternate construction of T-joint using the same socket and spigot arrangement as in FIG. 34.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(23) The embodiments of the present invention will now be described by way of example only. They are currently the best ways known to the applicant of putting the invention into practice but they are not the only ways in which this can be achieved.

(24) In FIG. 1 the numeral 1 identifies the outer pipe and numeral 2 the inner pipe of a double-pipe conduit, and numeral 3 identifies a free space between the outer and inner pipes. Pipes of this kind are used, among other things, in underground conduits for transporting petroleum liquids (gasoline) in petrol stations and the like. The double pipes enhance security against leakage. Any fluid leaking through the inner pipe 2 will be collected in the annular space 3 between the pipes and conducted to the lowest point of the conduit.

(25) When joining such pipes together, however, there arises the problem that the annular passageway 3 between the outer pipe and the inner pipe must also be sealed at the joint location against both the space in the inner pipe 2 and the atmosphere outside the outer pipe 1.

(26) FIG. 1 illustrates how such a joint is formed at present with the aid of conventional fusion welding sockets. These include two reduction sockets 4, and a fusion welding socket 9. Electrical energy is supplied to these sockets through terminals 6, 7, 10 and 11. The inner pipes 2 are joined using a welding socket 12, using terminals 13 and 14 to supply electrical energy. It will be appreciated that three separate components are required, and three electrofusion welds are needed, in order to join two pieces of secondary pipe 1 around a primary pipe connection.

(27) FIG. 2, in which a similar numbering system has been used to that in FIG. 1, illustrates application of the conventional technology when joining together three double-pipe conduits with the aid of a so-called T-coupling. As will be apparent from the figure, this operation requires the use of a large number of components. Firstly, the inner pipes must be coupled together with the aid of an inner T-shaped tubular part 16 that is joined to respective inner pipes with the aid of three welding sockets 12 of the same type as those used in the straight join shown in FIG. 1. It is then necessary to connect an outer T-shaped tube part 17 to the outer pipes 1 with the aid of reduction welding sockets 4 and outer welding sockets 9 in a manner similar to that used in the straight join shown in FIG. 1. Thus, a total of eleven components and at least two time-spaced welding operations are required, with associated time consumption and cost. As in the former case, it is not possible to check whether or not the welding operations carried out in joining the inner pipes have been effected correctly prior to assembly of the secondary containment system.

(28) For completeness, FIG. 3 illustrates two options for making a secondarily contained 90° elbow joint using conventional fittings. It will be understood that both types of assembly would not generally be used on the same primary pipeline and are shown in this combination for illustrative purposes only. FIG. 3 illustrates two pieces of primary pipe 32 which are connected by means of a 90° elbow 46 and two primary welding sockets 42. The secondary pipe is either oversized, in the case of pipe 31, in which case a correspondingly oversized secondary welding socket 48 and secondary elbow 47 are required. Alternatively, a snug fitting secondary pipe 31 is used, similar to the examples given in FIGS. 1 and 2. In that case, a sliding reducer 35 is used to connect to the oversized 90° secondary elbow 47, the secondary elbow being sized to accommodate the primary welding sockets used to join the primary pipes 32 to the primary elbow 46.

(29) As explained above, generally both sides of the elbow connection would be similar in construction. That is to say they would be a mirror image about line C-C in FIG. 3. The different arrangements are shown in the same drawing for illustrative purposes only.

(30) Turning now to FIG. 4, this illustrates an electrofusion coupling component in the form of a sliding elbow component 60. This component is generally tubular in form having a first end 61 made up of a first tubular portion 62. This first portion has an internal diameter that is designed to be a tight sliding fit over the external diameter of a pipe (not shown), typically a secondary pipe. The first tubular portion also incorporates an electrical heating element (not shown). This heating element comprises an electrical winding coil located at or near the inner surface of the internal diameter of the first end of the component. Each end of the winding is connected to an electrical terminal connection 64, 65. Only one terminal is visible in the view shown in FIG. 4 but both these terminals are shown clearly in FIG. 9. Connection of these terminals to a welding machine and passing electrical current causes the first end of the coupling component to become fused to any pipe that is a sliding fit within that end of the component.

(31) In this embodiment of the invention, electrofusion heating elements, and associated electrical terminal connections, are used as a sealing means to join two or more plastic components together in a substantially fluid-tight manner. It will however be appreciated that electrofusion is only one type of sealing means that can be used to join plastic components in this fashion. Other suitable sealing means include forming a bond or weld, including a chemical bond or weld, an ultrasonic weld or a heat weld; or a gasket seal with some clamping means to clamp the gasket between the plastic components. Suitable clamping means include bolts through the flanges. An example of this sealing method is illustrated in FIGS. 30 and 31 and described below.

(32) A combination of these sealing means may also be used, as determined by the materials specialist.

(33) The use of non-electrofusion means for sealing the respective coupling components to each other, and to the associated pipework, means that a wide range of different plastics, including thermosetting plastics, can be used to construct the various coupling components and the pipes being joined. So these coupling assemblies are not limited to use with electrofusible plastics. They can, for example, be used with pipes made from PVC and from FRP (fibre reinforced polymer). In these examples and with these materials, chemical bonding is particularly preferred.

(34) Possible thermosetting plastics may be selected from the group comprising:—

(35) Allyl resins (Allyls);

(36) Epoxys;

(37) Polyesters;

(38) Polyurethanes (PU).

(39) Corresponding resins may be used for bonding the various components together, and to the pipes.

(40) So, whilst these examples employ electrofusion welding as a sealing means, this is not intended to be a limiting feature, in that any suitable sealing means may be employed. The technology associated with such sealing means is known per se.

(41) The term “sliding fit” is a term known in the art, especially to those involved in forming electrofusion connections on pipes. In order for there to be good contact between the outside of the pipe and the inside of the electrofusion fitting, a good snug fit between the two components is required, such that contact is made with the inside of the fitting around substantially the whole outer circumference of the pipe. This is a commonplace design feature in such electrofusion couplings.

(42) A second end of the coupling component 66, which is generally larger in its inside diameter than the first end, terminates in an end face which includes a mating region in the form of a flange 67 extending radially from and radially in the plane of the end face. In this example the end face and thus the face of the flange is substantially planar, but formed in a plane that is substantially non-perpendicular to the general longitudinal axis of the component. This longitudinal axis is shown as a dotted line in FIG. 4, such that the corresponding flange on a second, similar electrofusion coupling component will mate with the flange on the first component to form an electrofusion coupling having one or more predetermined angles.

(43) So for example if the end face and thus the face of the flange on each component is at 45° to the longitudinal axis of the component, as is shown in FIGS. 4 and 5, the two components can mate together to form a 90° elbow coupling 80, as shown in FIG. 6, or a linear coupling 90 as shown in FIG. 7. Thus, providing two complementary components therefore serves two purposes. They can encapsulate a 90° elbow coupling in the primary pipe or a linear, 180° coupling in the primary pipe and thus maintain continuous secondary containment across either configuration of such couplings.

(44) However, these angles can be varied by the designer depending on the desired angle between the pipes to be joined. Nor do the two components need to be symmetrical, providing for further variation in these angles.

(45) It will be understood that the internal diameter of the second end of the component must be larger than the internal diameter of the first end. The second end need not be circular cylindrical in cross-section and an example having a generally oval second end is shown in FIGS. 15A to D described below. So more accurately the internal cross-sectional area of the opening in the second end is greater than that of the first end. Furthermore, the size and angle of the flanges means that two components will only mate together at specific angles. In the fittings described so far those angles are 90° and 180°. In some of the fittings described below the components will only mate together in one particular specific and pre-determined configuration.

(46) The component shown in FIG. 5, in which a corresponding numbering system has been used to that in FIG. 4, is identical to the fitting shown in FIG. 4 with two exceptions. Firstly it is a mirror image of the fitting shown in FIG. 4, although that is not necessary. Secondly, and more importantly, the flange face 77 incorporates an electrical heating element 73. This takes the form of an electrical winding coil located at or near the surface of the flange with each end of the coil attached to an electrical terminal 78, 79. In this way, once the opposing flanges of two components are clamped together, the flanges can be electrofused to become a single component. The electrical terminals for the windings 78, 79 in the component shown in FIG. 5 can be seen more clearly in FIGS. 9 and 14.

(47) FIG. 8 shows a partially completed 90° elbow fitting with secondary containment. Two sections of primary pipe 101 have been joined together using a 90° electrofusion elbow 106 and the integrity of the joint tested. Secondary pipes 102 are already in position with 90° sliding elbow components 60,70 pulled back over the secondary pipe to leave the primary coupling clear so that the join in the primary pipe can be formed unhindered. Once the joint in the primary pipe is completed and tested, the sliding elbow components 60, 70 are slid forward over the secondary pipe such that they meet, as shown in FIGS. 10 and 11. Clamping the two flanges 67, 77 together with a clamping means and connection of terminals 74, 75 to a welding machine enables the two sliding elbow components to be welded together as one and the coupling can then be welded to each secondary pipe either sequentially or in a simultaneous manner. If required the individual components can be welded to the secondary pipe in an initial operation and the flanges welded together in a subsequent operation. Or alternatively all 3 welding operations can be carried out simultaneously.

(48) A finished coupling is shown in FIGS. 10, 11 and 12.

(49) A variety of clamping means can be used to hold the two flanges in close juxtaposition. For example, barbed pins can be incorporated into one of the flanges, these barbed pins being secured, in use, through holes in the corresponding but opposing flange but preferably outside the welding zone. Alternatively U-profile clips can be used to clip over the edges of both flanges, holding them in place while the welding operation takes place. These clips can be separate items or can be incorporated into one or other of the flanges. For example, a quick release over-centre-action fastener, of the type used on ski boots could be employed. Conventional G-clamps or C-clamps of the appropriate size could be used. Alternatively a plurality of toggle clamps could be used. In a further alternative a plurality of spring loaded clamps could be employed.

(50) In summary, any clamping means capable of maintaining these mating flange faces in contact during the electrofusion operation whether integral to the fitting or independent and separate from the fitting may be used.

(51) The same components and procedure can be used to form an in-line joint (180° coupling) as shown schematically in FIGS. 13 and 14.

(52) An embodiment using the principles illustrated in FIGS. 4 to 14 inclusive applied to a T fitting is illustrated in FIGS. 15A to D. This shows a conventional T coupling 126, having a body 127 that provides connections for two primary pipes 121 in an in-line configuration across the top of the T. These connections have built in electrofusion windings 123 and 124. The coupling body also includes a spigot 129 set substantially at right angles to the rest of the fitting. Spigot 128 is electrofusion welded in use to primary pipe 121 using a conventional electrofusion coupling 129.

(53) Two flanged electrofusing coupling components 130 and 140 are provided which are both a sliding fit with secondary pipes 122. Coupling component 130 is a sliding fit with just one portion of secondary pipe 122 and thus may be drawn back, prior to the electrofusion of the two secondary containment coupling components, to allow access for the T coupling on the primary pipe to be installed, welded and the resulting joints pressure tested. This access is important to allow the joints in the primary pipe to be completed and tested before the secondary containment is sealed in place. This access is provided in part by the shape of the fitting and in part by the position of and the angle of the flanged connection between the various parts of the fitting.

(54) As with the previous examples, this electrofusion coupling component has a first end 131 made up of a first tubular portion 132. This first portion has an internal diameter that is designed to be a tight sliding fit over the external diameter of a pipe, typically a secondary pipe. The first tubular portion also incorporates an electrical heating element 133 (not shown). This heating element comprises an electrical winding coil located at or near the inner surface of the internal diameter of the first end of the component. Each end of the winding is connected to a terminal connection 134, 135. Only one terminal is visible in the view shown in FIG. 15. Connection of these terminals to a welding machine and passing electrical current causes the first end of the coupling component to become fused to any pipe that is a sliding fit within that end of the component.

(55) The second end of the fitting 136 terminates in an end face which includes a mating region in the form of a flange 137 extending radially from and radially in the plane of the end face. The size and shape of the component 130 in the region of the second end 136 is such that it will accommodate the primary pipe T coupling designed to fit within it. The flange 137 has a mating face designed to be a mating fit with a corresponding flange 147 on a second electrofusion coupling component 140. The external circumference of the flange may be substantially circular but it could equally well be a different shape, such as generally oblong or oval, as in this example.

(56) A second, complementary coupling component 140 with a mating flange face 147 is also shown in FIG. 15. This second coupling component has tubular portions 142 and 152 that are a tight sliding fit with two separate secondary pipes 122. Electrofusion windings 143 and 153 (not shown) and associated terminal connections 144, 145, 154, 155 enable these tubular portions to be welded in a fluid-tight manner to the secondary pipes 122. The mating flange 147 does not require any electrofusion windings.

(57) It will be appreciated that the location of the flanged joint 137, 147 with respect to the T coupling on the primary pipes can be adjusted to allow full and convenient access to the primary coupling. The two components 130 and 140 are not mirror images of each other so the join between them can be located as required, ensuring proper access to complete the joining together of 3 sections of primary pipe in a T configuration.

(58) FIG. 15B shows the relative dimensions of the secondary pipe 122 which has a diameter Y. Typically Y may, for example, be 125 mm. This contrasts with the primary pipe 121 which has a diameter X, where X may be for example 110 mm where the secondary pipe is 125 mm in diameter as in this example.

(59) FIGS. 16 to 20 inclusive illustrate an alternative version of a secondary T electrofusion coupling. In this case, use is made of the angled coupling components of the type illustrated in FIGS. 4 to 11. A T coupling 166 for joining 3 primary pipes 161 similar to that described in FIG. 15 is shown in the cutaway region of FIG. 16. In this embodiment, four electrofusion coupling components 170, 171, 172, 173 are used to join three separate portions of secondary pipe 162 in a T configuration. Three of these electrofusion coupling components 170, 171, 172 are identical and correspond to the type of component 60 or 70 shown in FIGS. 4 and 5, depending on whether the electrofusion windings are required in these components or are provided in a fourth component 173. It is also possible to use a mixture of components, with and without electrofusion windings if desired. It will be understood that only one flange in a pair of engaging flanges must incorporate electrofusion windings. Which flange contains these windings is not material in terms of the inventive concept but there may be practical advantages of locating these windings in a particular flange face.

(60) The fourth component 173 has a central hollow body 174 which is large enough to accommodate within it the primary pipe T coupling and allow access for the primary T-coupling to be formed and pressure tested prior to assembly of the secondary containment. As with the earlier examples, the sliding components 170, 171 and 172 are slid back along the respective sections of secondary pipe while this welding operation on the primary pipes takes place and the integrity of the primary pipe connection is tested. This arrangement is shown in FIGS. 18 and 19. Components 170, 171 and 172 are then slid into place as shown in FIGS. 17 and 20, clamped together as necessary and the electrofusion welds made. The respective components are then welded to the secondary pipes.

(61) As with the previous embodiments, the flange faces of the various coupling components are angled from the plane perpendicular to the general longitudinal axis of the electrofusion coupling assembly. Where there is more than one longitudinal axis, as with a T-fitting, the flanges on all of the components may be angled in this way. The angled orientation and configuration of the flanges is important in order to allow access to construct and test the coupling in the primary pipes.

(62) The respective diameters X and Y of the primary and secondary pipes may be similar to those described above.

(63) A further embodiment is shown in FIGS. 21 to 23 inclusive in which a similar numbering system has been used as in the earlier Figures. FIGS. 21 to 23 illustrate an alternative version of a secondary electrofusion coupling in which the flanges on two of the components, rather than being planar, are formed from two flange portions set substantially at right angles to each other. Thus a first component 230 has two flange faces or portions 237 and 238 set substantially orthogonal to each other. Flange portion 238 is thus in a plane non-perpendicular to the general longitudinal axis of the component. In fact, flange portion 238 is generally parallel to the longitudinal axis of the component. Similarly with component 231, which has flange portions 247 and 248, portion 248 is in a plane generally parallel with the longitudinal axis of the component.

(64) A third component 232 having a planar flange 257, which provides a mating face for flange portion 238 and flange portion 248, completes the electrofusion coupling assembly.

(65) These three components are provided with the necessary electrofusion heating elements and electrical connection terminals 234, 235, 244, 245, 254, 255, 264, 265, 274, 275 such that each component can be electrofused to its respective secondary pipe 222, and to the mating flange or flange portions with which it makes contact in the assembled state, as shown in FIG. 23. FIG. 23 shows the position of these welds.

(66) A variation of the embodiment shown in FIGS. 21 to 23 is illustrated in FIGS. 24 to 26 inclusive. In this case, rather than the flange portions on the two opposing components being at right angles to each other they are angled at about 135°. The flange portions on the third component 332 are angled at approximately 90° to each other. The flange portions thus meet in a star-shaped arrangement as shown in FIG. 26. Heating elements are provided in opposing flange faces as necessary and as determined by the designer. In this embodiment each component has a flange portion that is offset from the longitudinal axis of the component.

(67) It will be appreciated from the above description that the divisions between the various coupling components can be made in a wide variety of ways, as determined by the designer, providing they give clear access to form the primary coupling and the mating flange faces or flange portions can be electrofused together. This novel concept provides a number of advantages. Firstly, a wide variety of sealing means can be used to join the components together, and the invention is not limited to electrofusion couplings, although these are a preferred method of forming a substantially fluid-tight seal between components. Secondly, the arrangement of flange faces and the fact that the fitting components generally slide over the pipe onto which they will eventually be joined, provides unrestricted access to create, make and test the joint in the primary pipe, before making a corresponding joint in the secondary pipe.

(68) A still further embodiment is illustrated in FIGS. 27, 28 and 29. In this example the coupling assembly comprises four components 430, 431, 432, 433. The inter-engaging flanges 437, 438 are on component 433 and these engage with mating surfaces 447 and 448 on component 432. In use the components 432 and 433 are effectively welded around components 430 and 431 and welded to each other. Although they are shown as two separate components, 432 and 433 may be joined or formed together during manufacture with a so-called living hinge (not shown).

(69) Electrofusion heating elements are provided as necessary, with associated electrical terminals.

(70) A further embodiment is shown in FIGS. 30 and 31. These illustrate a three piece coupling comprising two coupling components 560,570 and a gasket 590. A first end of each coupling component 561,571 has an internal diameter designed to be a tight sliding fit over the external diameter of a pipe (pipe not shown for clarity). The internal or inner surface of the sliding fit diameter first end incorporates an electrical winding heating coil (not shown) and electrical terminals 564,565,574,575 to electrofuse the component onto a pipe in use.

(71) The cross-sectional area of the opening in the second end of each component is larger than that of the opening in first end. This allows space within the assembled coupling to accommodate a coupling around a primary pipe housed within a secondary pipe that is joined using the coupling illustrated in FIGS. 30 and 31. Each component 560,570 has at its second end a flange 567,577, the two flanges being adapted to mate together with gasket 590 in between the flanges. That assembly is completed by passing a plurality of bolts 584 through aligned apertures 562,572,591 and tightening units 581 to an even pressure. The nuts and bolts act as a clamping means to keep the two coupling components together. But it will be understood that any other suitable clamping means could also be used.

(72) The gasket 590 can be formed from any material as selected by the materials specialist. Elastomeric plastics or rubber materials are particularly effective, and preferably plastics or rubber materials that are not adversely affected by petroleum liquids or other fluids being carried by the pipe. Soft metal gaskets may also be used. This list is not intended to be exhaustive but rather to illustrate the broad range of materials that might be used in the construction of a gasket seal.

(73) FIG. 30 illustrates an assembled coupling assembly, designed to join two pipes at an angle of less than 180°.

(74) In a further variation, where the coupling components 560, 570 are formed from an electrofusible plastics material, the gasket 590 may take the form of an electrofusible gasket or electrofusible tape or rope. Assembly is in a similar fashion to that described above except a clamp or clamps are used to hold the two coupling components in the correct spatial orientation during electrofusion, rather than bolts. Once the respective parts have been fused together the clamps can be removed.

(75) The above arrangement of mechanical fixing means and a gasket of some type can be applied and incorporated into any of the coupling assemblies described or claimed herein.

(76) FIGS. 32 and 33 illustrate a further alternative embodiment. FIG. 32 shows an electrofusion coupling including two components in the form of a sliding elbow component 600 wherein the outside of the coupling can be seen with a cross section cutaway portion showing the cross section of the coupling and the primary coupling within the coupling of the present invention. FIG. 33 shows the identical coupling of FIG. 32 but this time transparently showing the primary coupling within the coupling of the present invention. The first component 601 is generally tubular in form having a first end 602 made up of a first tubular portion 603. This first portion has an internal diameter that is designed to be a tight sliding fit over the external diameter of a pipe 604, typically a secondary pipe. The first tubular portion also incorporates an electrical heating element (not shown). This heating element comprises an electrical winding coil located at or near the inner surface of the internal diameter of the first end of the component. Each end of the winding is connected to an electrical terminal connection (not shown). Connection of these terminals to a welding machine and passing electrical current causes the first end of the coupling component to become fused to any pipe that is a sliding fit within that end of the component.

(77) A second end of the coupling component 605, which is generally larger in its inside diameter than the first end, terminates in an end face which includes a mating region in the form of a flange extending axially from and axially in the plane of the end face defining a spigot 607.

(78) The second component 611 is generally tubular in form having a first end 612 made up of a first tubular portion 613. This second portion has an internal diameter that is designed to be a tight sliding fit over the external diameter of a pipe 614, typically a secondary pipe. The second tubular portion also incorporates an electrical heating element (not shown). This heating element comprises an electrical winding coil located at or near the inner surface of the internal diameter of the first end of the component. Each end of the winding is connected to an electrical terminal connection (not shown). Connection of these terminals to a welding machine and passing electrical current causes the first end of the coupling component to become fused to any pipe that is a sliding fit within that end of the component.

(79) A second end of the second coupling component 615, which is generally larger in its inside diameter than the first end, terminates in an end face which includes a mating region in the form of a flange extending axially from and axially in the plane of the end face defining a socket 617.

(80) The spigot 607 of the first component is adapted to nest within the socket 617 of the second component and to form a tight sliding fit there between. A sealing means is provided between the contact faces of the spigot 607 and the socket 617. In the example shown a heating element is provided (not shown). This heating element comprises an electrical winding coil located at or near the inner surface of socket 617 or the external surface of spigot 607. Each end of the winding is connected to an electrical terminal connection (not shown). Connection of these terminals to a welding machine and passing electrical current causes the first coupling component to become fused to the second coupling component in a fluid tight manner to create fusion weld 620.

(81) FIG. 34 illustrates another embodiment of the present invention in a T-joint arrangement utilising the same spigot and socket arrangement as described in detail in FIGS. 32 and 33 above. In this embodiment the coupling 700 includes a first component 701 and a second component 711.

(82) The first component 701 has a first end 702 made up of a first tubular portion 703. This first portion has an internal diameter that is designed to be a tight sliding fit over the external diameter of a pipe 704, typically a secondary pipe. The first tubular portion also incorporates an electrical heating element (not shown). This heating element comprises an electrical winding coil located at or near the inner surface of the internal diameter of the first end of the component. Each end of the winding is connected to an electrical terminal connection (not shown). Connection of these terminals to a welding machine and passing electrical current causes the first end of the coupling component to become fused to any pipe that is a sliding fit within that end of the component.

(83) The first component 701 has a second end 702′ made up of a first tubular portion 703′. This first portion has an internal diameter that is designed to be a tight sliding fit over the external diameter of a pipe 704′, typically a secondary pipe. The first tubular portion also incorporates an electrical heating element (not shown). This heating element comprises an electrical winding coil located at or near the inner surface of the internal diameter of the first end of the component. Each end of the winding is connected to an electrical terminal connection (not shown). Connection of these terminals to a welding machine and passing electrical current causes the first end of the coupling component to become fused to any pipe that is a sliding fit within that end of the component.

(84) A third end of the coupling component 705, which is generally larger in its inside diameter than the first end, terminates in an end face which includes a mating region in the form of a flange extending axially from and axially in the plane of the end face defining a socket 707.

(85) The second component 711 is generally tubular in form having a first end 712 made up of a first tubular portion 713. This second portion has an internal diameter that is designed to be a tight sliding fit over the external diameter of a pipe 714, typically a secondary pipe. The second tubular portion also incorporates an electrical heating element (not shown). This heating element comprises an electrical winding coil located at or near the inner surface of the internal diameter of the first end of the component. Each end of the winding is connected to an electrical terminal connection (not shown). Connection of these terminals to a welding machine and passing electrical current causes the first end of the coupling component to become fused to any pipe that is a sliding fit within that end of the component.

(86) A second end of the second coupling component 715, which is generally larger in its inside diameter than the first end, terminates in an end face which includes a mating region in the form of a flange extending axially from and axially in the plane of the end face defining a spigot 717.

(87) The socket 707 of the first component is adapted to nest within the spigot 717 of the second component and to form a tight sliding fit there between. A sealing means is provided between the contact faces of the socket 707 and the spigot 717. In the example shown a heating element is provided (not shown). This heating element comprises an electrical winding coil located at or near the external surface of spigot 717 or the internal surface of socket 707. Each end of the winding is connected to an electrical terminal connection (not shown). Connection of these terminals to a welding machine and passing electrical current causes the first coupling component to become fused to the second coupling component in a fluid tight manner to create fusion weld 720.

(88) FIGS. 35A to 35D, 36A to 36D, 37A to 37D and 38A to 38E illustrate alternate constructions of T-joints using the same socket and spigot arrangement as discussed in detail in relation to FIG. 34 above. For example, coupling 950 contains components, including components defining a socket and spigot analogous to socket 617 and spigot 607, described in detail in FIGS. 32 and 33, which in turn use the same socket and spigot arrangement of FIG. 34 as noted above.

(89) It will be appreciate that the aspects of the different embodiments described above are not exclusive to any particular embodiment and aspects of one embodiment may be used in combination with aspects of another embodiment.

(90) It will be appreciated that aspects of the present invention include methods of manufacturing components and couplings according to the present invention, methods of forming joints using such components and couplings and pipework systems including such joints and couplings.

(91) Couplings according to the present invention can be constructed from any suitable plastics material as determined by the materials specialist. Typically they are formed from a group including thermoplastic polymers such as but in no way limited to:— Polyethylene Polypropylene Polyvinyl chloride Fluoropolymers including tetrafluoropolyethylene Nylon 612 Polyamides Polyamides 6, 11 or 12 Polyethylene terephthalate Polyvinylidene chloride or fluoride Ethylene/vinyl alcohol copolymers
or mixtures of any of the above.