GB2240599A

GB2240599A - Apparatus and fitting for coupling plastics pipes

Info

Publication number: GB2240599A
Application number: GB8922002A
Authority: GB
Inventors: Charles John Ashdown
Original assignee: WELSH WATER PLC; Bruff Manufacturing Co Ltd
Current assignee: WELSH WATER PLC; Bruff Manufacturing Co Ltd
Priority date: 1989-09-29
Filing date: 1989-09-29
Publication date: 1991-08-07
Also published as: GB8922002D0

Abstract

An apparatus for coupling two pipes 1 using a fitting 2 includes an elongate frame 10, a first clamping device 15 mounted on the frame for releasable engagement with a pipe 1 to clamp the pipe to the frame 10 and a second clamping device 14 mounted on the frame 10 for releasable engagement with an intermediate portion (5) of the fitting 2 to clamp the fitting to the frame. The clamping device 15 is mounted for movement along the frame 10, and an actuator device (24) is engageable with the first clamping device 15, to drive it towards the second clamping device 14. <IMAGE>

Description

Improvements in the coupling of pipes This invention relates to an apparatus and a fitting for coupling pipes and a method of coupling pipes.

When laying plastics pipes for water or gas supplies, it is frequently necessary to couple the ends of two pipes to one another, for example when the end of a length of piping is reached, or when an obstruction, such as an electricity supply cable, is encountered, requiring that the pipe is cut and then rejoined below the obstruction.

In order not to delay unduly the pipe laying operation, thereby increasing its cost, it is desirable to be able to couple pipes quickly and efficiently to one another, forming couplings that are mechnically strong and able to withstand the pressure of water or gas supplied through the pipe and the strains imposed on the pipe after it has been laid.

One known method of coupling plastics pipes is to heat the ends of the pipes to melting point and then clamp them in abutment with one another so that the ends fuse as they cool. Such a method is very time consuming however since both the heating and cooling processes are slow.

A method of securing a plastics pipe to a fabricated steel connector is described in British patent application No. 1,596,112. In this method a fitting comprising a flange for securing to the connector, and a cylindrical liner having a plurality of grooves around its external surface, is attached to the pipe by inserting the liner into the pipe end and then driving a cylindrical sleeve over the pipe end. The external diameter of the liner is greater than the internal diameter of the pipe, so that when the liner is inserted into the pipe the external diameter of the pipe increases to exceed the internal diameter of the sleeve.Driving the sleeve over the pipe end thus compresses the pipe end between the sleeve and the liner, causing the plastics material to flow into the grooves and produce a joint between the fitting and the pipe that is mechanically strong, fluid-tight and simple to make. The fitting may then be secured to a connector, for example by passing bolts through the flange.

When attaching the fitting to large diameter plastics pipes, such as gas or water supply pipes, a very large force is required to insert the liner into the pipe and subsequently to drive the cylindrical sleeve over the expanded pipe end, causing the plastics material to flow.

This force is provided by gripping the pipe securely in a clamping device and then bringing a hydraulic ram to bear on the end of the fitting, driving the liner into the pipe. The hydraulic ram must be correctly aligned with its axis of operation coaxial with the axis of the pipe, since the fitting will otherwise be driven crookedly into the pipe, resulting in a faulty joint.

It is suggested in GB 1,596,112 that "a fitting could be provided for joining two lengths of pipe, which fitting would have two coaxial tubular inserts joined by a central flange". Such a fitting has not, in practice, been found to be practical however since, after the fitting has been connected to one of the pipes, the hydraulic ram cannot be brought to bear on the inserted end of the fitting in order to connect it to the second pipe. It has further been believed until now that an arrangement in which the hydraulic ram is not coaxial with the pipe is not practical, since such an arrangement would result in a crooked and unsatisfactory connection.

According to the present invention, there is provided an apparatus for coupling two pipes using a fitting including a substantially cylindrical body member comprising two end portions each for insertion into a pipe end and an intermediate portion, and two cylindrical sleeves each for arrangement around a pipe end to compress the pipe end between the cylindrical sleeve and the respective end portion of the body member, the apparatus including an elongate frame, a first clamping device mounted on the frame for releasable engagement with a pipe to clamp the pipe to the frame with the axis of the pipe substantially parallel to the longitudinal axis of the frame, a second clamping device mounted on the frame for releasable engagement with the intermediate portion of the body member to clamp the body member to the frame with the axis of the body member substantially coaxial with the axis of the pipe when clamped in the first clamping device, at least one of the clamping devices being mounted for movement along the frame, and an actuator device engageable with the movable clamping device, for driving the movable clamping device towards the other clamping device.

The apparatus may be used to couple two pipes to one another quickly and efficiently, forming a joint that is mechanically strong and fluid-tight. Since the second clamping device engages the intermediate portion of the body member of the fitting, it is possible to drive an end portion of the fitting into a pipe, even after the other end portion has been connected to another pipe.

The arrangement of the clamping devices on the elongate frame, such that the axis of the body member is substantially coaxial with the axis of the pipe, ensures that the end portion is inserted correctly into the pipe to reduce the risk of forming a faulty joint.

Preferably, the apparatus includes a device for releasably gripping the external cylindrical surface of a pipe, the device being engageable with the first clamping device to prevent longitudinal movement in at least one direction of the pipe relative to the clamping device.

Advantageously, the gripping device may be loosened to allow it to slide freely over the pipe, and includes means for engaging a cylindrical sleeve so that movement of the device relative to the pipe in at least one direction causes similar movement of the sleeve relative to the pipe. The gripping device may therefore be used to grip the pipe when the end portion is being inserted into the pipe end and then, after being loosened, to bear on the cylindrical sleeve causing it to be driven over the expanded end of the pipe.

The gripping device may include two semi-cylindrical shells and means for clamping the shells to one another about a pipe, to clamp the device to the pipe. The internal cylindrical surface of each shell may be roughened, to improve its grip on the pipe.

The first clamping device and the second clamping device may include similar clamping elements suitable for engaging either a pipe or the intermediate portion of the body member, thereby making it unnecessary, after connecting the fitting to one of the pipes, to reverse the apparatus in order to connect the fitting to the other pipe.

Each clamping device may include a seating for engagement with the cylindrical wall of a pipe or a cylindrical part of the intermediate portion of the body member, and means for retaining the pipe or the body member in the seating.

The actuator device may be mounted on the elongate frame with its axis of operation parallel to, and spaced from, the longitudinal axis of a pipe when clamped to the frame. Preferably, the axis of operation of the actuating device is substantially coaxial with the longitudinal axis of the elongate frame.

The actuating device may be a hydraulic ram.

The position of the hydraulic ram is adjustable with respect to the length of the frame, to enable it to be brought into engagement with the movable clamping device.

Preferably, the frame includes two parallel beams, and the movable clamping device includes a plurality of rollers engaged in channels in the beams. As an alternative to guiding the clamping device with rollers, the device may be slidably mounted by, for example, a sliding shoe mechanism.

At least one of the clamping devices may be pivotable with respect to the frame, making it simpler to clamp the device to a curled-up end of a pipe.

According to the present invention, there is further provided a fitting for coupling two pipes to one another, the fitting including a substantially cylindrical body member having two end portions each for insertion into a pipe end and an intermediate portion shaped to receive a substantial force in a direction parallel to the axis of the body member, and two cylindrical sleeves each for arrangement around a pipe end to compress the pipe end between the sleeve and the respective end portion of the body member.

The shaping of the intermediate portion to receive a substantial force in a direction parallel to the axis of the body member, enables it to be inserted into a pipe end without the need to apply a substantial force to the end of the body member. The body member can therefore be connected to a second pipe after it has been connected to a first pipe.

Preferably, the intermediate portion comprises a cylindrical part having at each end thereof abutment means for receiving the axial force. Each abutment means preferably comprises a circular flange having a diameter greater than the external diameter of the cylindrical part. Each cylindrical sleeve may have an internal diameter at least as great as the external diameter of the cylindrical part.

Each end portion may be provided on its external cylindrical surface with a plurality of circumferential grooves.

The present invention further provides a coupling between two pipes including a fitting as described above and two pipes, each end portion of the body member being located within an end of one of the pipes, and a cylindrical sleeve being located around each pipe end to compress the pipe end between the cylindrical sleeve and the respective end portion, the external diameter of each end portion being greater than the internal diameter of the pipe in its free state and the internal diameter of each cylindrical sleeve being at least as great as the external diameter of the pipe in its free state.

The external diameter of the cylindrical part may be substantially equal to the external diameter of the pipe in its free state, thereby enabling a clamping device to be engaged with either the pipe or the body member.

The present invention yet further provides a method of coupling two pipes in which a fitting, which includes a substantially cylindrical body member comprising two end portions and an intermediate portion, and two cylindrical sleeves, is coupled to a first one of the pipes by locating one of the cylindrical sleeves around the pipe so that an end of the pipe projects beyond the sleeve, attaching a gripping device to the pipe to grip the pipe tightly, clamping the pipe in a first clamping device, clamping the body member in the second clamping device with the second clamping device in engagement with the intermediate portion, actuating an actuator device to drive an end portion of the body member into the end of the pipe, loosening the gripping device sufficiently to allow the pipe to slide freely therethrough, and actuating the actuator device again to drive the cylindrical sleeve over the pipe end towards the body member to compress the pipe end between the sleeve and the end portion of the body member, and is then coupled to the second of the two pipes by repeating for the second pipe the steps described above for the first pipe.

Preferably, the pipes are coupled using an apparatus as described above.

By way of example, an embodiment of the invention will now be described with reference to the accompanying drawings, of which: Fig. 1 is a side view of a fitting for coupling pipes, showing the fitting already attached to one of a pair of pipes, Fig. 2 is a side view of an apparatus for coupling pipes using the fitting shown in Fig. 1, Fig. 3 is a plan view of the apparatus shown in Fig. 1, Fig. 4 is a cross-section to an enlarged scale on line IV-IV of Fig. 2, Fig. 5 is a cross-section to an enlarged scale on line V-V of Fig. 2, and Fig. 6 is a view to an enlarged scale and partly in section of a part of the apparatus shown in Fig. 2.

The fitting for coupling pipes, which is shown in Fig. 1 already attached to one end of a pipe 1, consists of a substantially cylindrical body member indicated generally by the reference numeral 2 and two cylindrical sleeves 3. The body member 2 is symmetrical about its mid-point and comprises two end portions 4 for insertion into the ends of the pipes that are to be coupled, and an intermediate portion 5. Only one of the end portions 4 can be seen in Fig. 1 since the other end portion has been inserted into the first pipe.

Each end portion 4 has an external diameter slightly greater than the internal diameter of the pipe 1, and is provided with a plurality of grooves 6 which extend circumferentially around its external surface. The extreme end region 7 of each end portion 4 is frustoconical in shape, tapering towards the end of the body member 2.

The intermediate portion 5 of the body member comprises two raised circular flanges 8, spaced apart by a cylindrical part 9 of external diameter approximately equal to the external diameter of the pipe.

The two sleeves 3 are each provided with a circular bore of diameter substantially equal to the external diameter of the pipe, so that the sleeve is a sliding fit over the pipe. The bore is chamfered at each end of the sleeve to assist movement of the sleeve over the pipe.

The method of coupling pipes using the fitting is as follows: first, a cylindrical sleeve 3 is fitted over an end of one of the pipes 1 and is pushed along the pipe until a predetermined length of the pipe end protrudes beyond the sleeve. An end portion 4 of the body member 2 is then forced into the pipe end sufficiently far that the pipe covers at least some of the grooves 6 (preferably 3 or 4 grooves) in the end portion. Because the external diameter of the end portion 4 is greater than the internal diameter of the pipe, insertion of the end portion into the pipe causes the pipe wall to stretch outwardly, thereby increasing the external diameter of that part of the pipe. The sleeve 3, which is positioned beyond the stretched end part of the pipe, is then driven back towards the body member 2 over the stretched part of the pipe until it abuts the nearer flange 8 of the body member 2. Because the internal'diameter of the sleeve 3 is substantially equal to the external diameter of the pipe in its free state, driving the sleeve towards the body member 2 forces the plastics material of the stretched part of the pipe to flow into the grooves 6, thereby enhancing the seal and mechanical connection between the pipe 1 and the fitting.

When the fitting has been attached to an end of one of the pipes by the method described above, the process is repeated with the other pipe, coupling the pipes together.

The apparatus for coupling pipes using the fitting is shown in Figs. 3 to 6. The apparatus includes a frame indicated generally by the reference numeral 10, comprising two parallel beams 11, which are joined to one another by steel cross members. Two strengthening plates 13 are welded to the tops of the beams 11 to reduce bending of the frame 10. As shown in Figs. 4 and 5, the beams 11 have a substantially C-shaped cross section, the open faces of the beams forming outwardlyfacing channels.

Two clamping devices 14 and 15, each consisting of two side plates 16, a top plate 17 and a front plate 18, are mounted on the frame 10. The first clamping device 14 is pivotally attached to the frame 10 by two pivot mounts 19 which extend inwardly through apertures 20 in the C-shaped beams 11 and corresponding apertures in two reinforcing plates 21 welded to the open faces of the beams. The pivot mounts 19 are retained by circlips 22.

The pivotal mounting allows the first clamping device 14 to pivot forwards (i.e. anti-clockwise) from the position shown in Fig. 2. Rearward (i.e. clockwise) movement from that position is prevented by the abutment of the rear (left hand) end of the top plate 17 with the underside of the C-shaped beams 11.

The second clamping device 15 is provided on each of its side plates 16 with two inwardly-facing rollers 23 which are located within the channels formed by the open faces of the C-shaped beams 11. The rollers 23 allow the second clamping device 15 to move forwards and backwards along the frame 10, towards or away from the first clamping device 14.

A hydraulic ram 24, mounted between the C-shaped beams 11 towards one end of the frame 10, engages an abutment member 25 which is securely welded to the top plate 17 of the second clamping device 15. The ram 24 is attached to the frame via an adjustable mounting device 26, which allows the position of the ram along the length of the frame to be changed. Actuation of the hydraulic ram 24 drives the second clamping device 15 towards the first clamping device 14.

As shown in Figs. 4 and 5, a seating 27 for a pipe is attached to the front plate 18 of each clamping device. The seating 27 comprises a steel plate having in its lower edge 29 a semicircular recess 28 of diameter substantially equal to the external diameter of the pipe, in which recess a pipe can be seated.

Attached to the front surface 30 of the seating is a retaining device 31, comprising a pair of levers 32, pivotally mounted about their respective mid-points. The upper ends of the levers 32 are joined by two pivot links 34 and are biassed towards one another by a tension spring 35. The middle joint 36 of the pivot links 34 may be lifted from the position shown in Figs. 4 and 5, causing the upper ends of the levers 32 to move towards one another under the tension in the spring 35, causing the lower ends of the levers to move away from one another. Pressing the middle joint 36 back down to the position shown in Figs. 4 and 5 causes the lower ends of the levers 32 to move back to the positions shown in the drawings. Downward movement of the middle joint 36 beyond that position is prevented by its abutment with a stop member 37.The stop member 37 is positioned to allow the middle joint 36 to move just beyond an imaginary line drawn between the joints of the links 34 with the levers 32, so that when the middle joint is in contact with the stop member 37, the levers are locked in a stable formation.

Attached to the lower end of each lever 32 is an inwardly-projecting tooth 38. Each tooth 38 lies in the plane of the seating 27, just below its lower edge 29, and has an inner edge 39 which, when the lower ends of the levers are at their innermost position, lies on the imaginary circle defined by the outline of the semicircular aperture 28. The teeth 38 therefore form extensions of the seating 27 and, when the levers 32 are in the locked position, serve to clamp a pipe in the seating. The pipe may be removed from, or placed in, the seating 29 by lifting the middle joint 36 of the pivot links 34, thereby causing the lower ends of the levers and the teeth 38 to move outwardly beyond the periphery of the semi-circular aperture 28.The teeth 38 are arranged to press sufficiently firmly on the pipe 1 to locate it correctly in the seating 27, but not so firmly as to prevent the pipe from sliding longitudinally through the seating.

The apparatus for coupling pipes also includes a pipe gripping device, indicated generally by the reference numeral 40, which is shown in more detail in Fig. 6. The pipe gripping device 40 comprises two semicylindrical shells 41, each having an internal diameter substantially equal to the external diameter of the pipe 1. The two shells 41 are hinged to one another along one side by a pivot joint 42 and are connected to one another at the other side by a bolt 43 which extends through swivel mountings 44 provided on each shell. When the bolt 43 is removed, the two shells 41 can be opened up to allow a pipe to be placed in, or removed from, the gripping device 40. The internal surface of the go piping device 40 is knurled to provide a rough surface 45 which grips the pipe when the device is clamped around it.

The apparatus is used to couple the pipes as follows: First, a cylindrical sleeve 3 is fitted over an end of one of the pipes 1 and is pushed along the pipe until the pipe end protrudes by a predetermined amount beyond the sleeve. The gripping device 40 is then clamped to the pipe just behind the sleeve 3 (that is, with the sleeve between the gripping device and the pipe end), and the bolt 43 is tightened so that the pipe is gripped securely.

Next, the pipe is offered up to the apparatus and is located in the seating 27 of the first clamping device 14, with the front face 30 of the seating abutting the rear end of the gripping device 40. The pipe is clamped in that position by pressing down on the middle joint 36 of the retaining device 31, to lock the levers 32. The arrangement is such that the end of the pipe protrudes forward of the first clamping device 14, and the sleeve 3, the gripping device 40, and the first clamping device 14 are mounted in that order on the pipe, with the sleeve nearest to the pipe end.

Next, the body member 2 is clamped in the second clamping device 15 with the seating 27 engaging the cylindrical part 9, and the second clamp 15 is pushed towards the first clamping device 14 until the pipe end presses against the end portion 4. This causes the first clamping device 14 to swivel as far as possible in the clockwise direction, until its top plate 17 abuts the beams 11. When that position is reached, the body member 2 and the pipe 1 will be coaxial with the end portion 4 of the body member adjacent the end of the pipe.

The hydraulic ram 24 is then adjusted to engage the abutment member 25 on the top plate 17 of the second clamping device 15, and is activated forcing the second clamping device forwards along the frame 10, and inserting the end portion 4 of the body member 2 into the end of the pipe 1. When the end portion 4 has been inserted far enough into the pipe (so that, preferably, the pipe end covers 3 or 4 of the grooves 6), the ram is halted, and the bolt 43 clamping the two halves of the gripping device 40 is loosened sufficiently to allow the gripping device to slide freely over the pipe, whilst still being mounted around the pipe. The ram 24 is then activated again and, since the pipe is no longer gripped firmly, the gripping device 40 bears against the rear end of the cylindrical sleeve 3, pushing it forwards over the pipe towards the body member 2.The cylindrical sleeve 3 thereby causes the plastic material of the pipe end to flow into the grooves 6, sealing the pipe to the fitting.

The fitting must next be attached to the second pipe, to complete the coupling. This time, the body member 2 is clamped in the first clamping device 14, with the free end portion 4 of the body member projecting forwards of the clamping device and the seating 27 engaging the cylindrical part 9 between the flanges 8 of the body member. A sleeve 3 is fitted onto the end of the second pipe 1 and the gripping device 40 is securely attached to the pipe just behind the sleeve. The second pipe is then clamped in the second clamping device 15, with the seating 27 engaging the pipe just behind the rear of the gripping device 40, so that the arrangement of the pipes in the apparatus is as shown in Figs. 2 and 3.

The hydraulic ram 24 is then activated to force the end portion 4 of the body member 2 into the pipe and, when the end portion has been inserted far enough, the gripping device 40 is loosened so that further activation of the ram causes the second sleeve 3 to be pushed over the stretched end of the pipe, to complete the coupling.

Because the pipe coupling apparatus is very narrow, allowing it to be lowered into a narrow trench, and because it can be operated remotely by a person standing above the trench, the apparatus can be used to couple pipes to one another at the bottom of such a trench.

This ability makes the apparatus particularly appropriate for use with a modern pipe-laying machine, which digs and lays a pipe in a trench that is only slightly wider than the pipe, either to couple lengths to one another, or to rejoin the ends of a pipe which has had to be cut to avoid an obstruction. Using the apparatus and the fitting described above, the cut ends of the pipe can be quickly and efficiently rejoined at the bottom of the trench underneath the obstruction, thereby causing minimal delay to the pipe-laying operation. Further, as it is not necessary to dig a large hole in order to accommodate the pipe-coupling apparatus, disruption to the immediate environment is minimised.

The pivoting movement of the first clamping device 14 allows the apparatus to be clamped to pipes which have a tendency to curl up when cut.

It is, of course, possible that when laying new pipes, the fitting could be supplied already joined to an end of one of the pipes or could be joined to one of the pipes on site before the pipe is lowered into the prepared trench. The use of the apparatus will still however be required to complete the coupling of the two pipes to one another.

Claims

Claims:

1. An apparatus for coupling two pipes using a fitting including a substantially cylindrical body member comprising two end portions each for insertion into a pipe end and an intermediate portion, and two cylindrical sleeves each for arrangement around a pipe end to compress the pipe end between the cylindrical sleeve and the respective end portion of the body member, the apparatus including an elongate frame, a first clamping device mounted on the frame for releasable engagement with a pipe to clamp the pipe to the frame with the axis of the pipe substantially parallel to the longitudinal axis of the frame, a second clamping device mounted on the frame for releasable engagement with the intermediate portion of the body member to clamp the body member to the frame with the axis of the body member substantially coaxial with the axis of the pipe when clamped in the first clamping device, at least one of the clamping devices being mounted for movement along the frame, and an actuator device engageable with the moveable clamping device, for driving the moveable clamping device towards the other clamping device.

2. An apparatus according to claim 1, including a device for releasably gripping the external cylindrical surface of a pipe, the device being engageable with the first clamping device to prevent longitudinal movement in at least one direction of the pipe relative to the clamping device.

3. An apparatus according to claim 2, in which the gripping device may be loosened to allow it to slide freely over the pipe, and includes means for engaging a cylindrical sleeve so that movement of the device relative to the pipe in at least one direction causes similar movement of the sleeve relative to the pipe.

4. An apparatus according to claim 2 or claim 3, in which the gripping device includes two semicylindrical shells and means for clamping the shells to one another about a pipe, to clamp the device to the pipe.

5. An apparatus according to claim 4, in which the internal cylindrical surface of each shell is roughened.

6. An apparatus according to any one of the preceding claims, in which the first clamping device and the second clamping device include similar clamping elements suitable for engaging a pipe or the intermediate portion of the body member.

7. An apparatus according to claim 6, in which each clamping device includes a seating for engagement with the cylindrical wall of a pipe or a cylindrical part of the intermediate portion of the body member, and means for retaining the pipe or the body member in the seating.

8. An apparatus according to any preceding claim, in which the actuator device is mounted on the elongate frame with its axis of operation parallel to, and spaced from, the longitudinal axis of a pipe when clamped to the frame.

9. An apparatus according to claim 8, in which the axis of operation of the actuating device is substantially coaxial with the longitudinal axis of the elongate frame.

10. An apparatus according to claim 8 or claim 9, in which the actuating device is a hydraulic ram.

11. An apparatus according to claim 10, in which the position of the hydraulic ram is adjustable with respect to the length of the frame.

12. An apparatus according to any preceding claim, in which the frame includes two parallel beams, and the moveable clamping device includes a plurality of rollers engaged in channels in the beams.

13. An apparatus according to any preceding claim, in which at least one of the clamping devices is pivotable with respect to the frame.

14. An apparatus substantially as described herein with reference to, and as illustrated by, the accompanying drawings.

15. A fitting for coupling two pipes to one another, the fitting including a substantially cylindrical body member having two end portions each for insertion into a pipe end and an intermediate portion shaped to receive a substantial force in a direction parallel to the axis of the body member, and two cylindrical sleeves each for arrangement around a pipe end to compress the pipe end between the sleeve and the respective end portion of the body member.

16. A fitting according to claim 15, in which the intermediate portion comprises a cylindrical part having at each end thereof abutment means for receiving the axial force.

17. A fitting according to claim 16, in which each abutment means comprises a circular flange having a diameter greater than the external diameter of the cylindrical part.

18. A fitting according to claim 16 or claim 17, in which each cylindrical sleeve has an internal diameter at least as great as the external diameter of the cylindrical part.

19. A fitting according to any one of claims 15 to 19, in which each end portion is provided on its external cylindrical surface with a plurality of circumferential grooves.

20. A fitting for coupling two pipes, the fitting being substantially as described herein with reference to, and as illustrated by, the accompanying drawings.

21. A coupling between two pipes including a fitting according to any one of claims 15 to 20 and two pipes, each end portion of the body member being located within an end of one of the pipes, and a cylindrical sleeve being located around each pipe end to compress the pipe end between the cylindrical sleeve and the respective end portion, the external diameter of each end portion being greater than the internal diameter of the pipe in its free state and the internal diameter of each cylindrical sleeve being at least as great as the external diameter of the pipe in its free state.

22. A coupling according to claim 21 when dependent on any one of claims 16 to 18, in which the external diameter of the cylindrical part is substantially equal to the external diameter of the pipe in its free state.

23. A method of coupling two pipes in which a fitting, which includes a substantially cylindrical body member comprising two end portions and an intermediate portion, and two cylindrical sleeves, is coupled to a first one of the pipes by locating one of the cylindrical sleeves around the pipe so that an end of the pipe projects beyond the sleeve, attaching a gripping device to the pipe to grip the pipe tightly, clamping the pipe in a first clamping device, clamping the body member in a second clamping device with the second clamping device in engagement with the intermediate portion, actuating an actuator device to drive an end portion of the body member into the end of the pipe, loosening the gripping device sufficiently to allow the pipe to slide freely therethrough, and actuating the actuator device again to drive the cylindrical sleeve over the pipe end towards the body member to compress the pipe end between the sleeve and the end portion of the body member, and is then coupled to the second of the two pipes by repeating for the second pipe the steps described above for the first pipe.

24. A method according to claim 23, in which the pipes are coupled using an apparatus according to any one of claims 1 to 14.

25. A method of coupling two pipes, the method being substantially as described herein with reference to, and as illustrated by, the accompanying drawings.