The present invention relates to assemblies, in particular an assembly including a first pipe and a second pipe. The invention also relates to a pipe.

US4252349, US4385644 and US4647078 show composite plastic pipes.

Typically composite plastic pipes are made from a fibre reinforcing material held in place by a matrix resin. The fibres may be any type of fibre including glass fibre, aramid fibre (Kevlar), carbon fibre etc. The resin matrix may be any suitable type of plastics material including thermosetting plastics material such as epoxy or polyester materials. Where such pipes are used under arduous conditions, in particular high internal pressures (for example internal pressures from 25 to 750 bar), it is difficult to join two pipes together in a simple and cost effective manner. The above mentioned US patent applications give examples of how plastic pipes may be coupled together. However, in each example coupling is complicated.

Aircraft fuselages are an example of hollow structures that need to be joined, and are subject to large pressure differentials, bending and torsion loads in use. Increasingly, aircraft are being constructed from composite materials which do not lend themselves to the joining methods used in sheet metallic structures (such as riveted butt straps).

An aim of the present invention is to provide an improved method for coupling pipes and pipe-like structures which overcome or at least mitigate the above-mentioned problems. Thus, according to the present invention there is provided an assembly including

a first pipe being made from a composite material having a first pipe end section with a first pipe end section inner surface that tapers inwardly, a first reinforcing element having a first portion positioned inside said first pipe end section and having an outer surface shape corresponding to the shape of the first pipe end section inner surface, the first reinforcing element including a first abutment region,

a second pipe being made from a composite material and having a second pipe end section with a second pipe end section inner surface that tapers inwardly,

a second reinforcing element having a second reinforcing portion positioned inside said second pipe end section and having an outer surface shape corresponding to the shape of the second pipe end section inner surface, the second reinforcing elements including a second abutment region, and

a locking device configured to limit axial movement of the first abutment region relative to the second abutment region.

According to a further aspect of the present invention there is provided an assembly including a pipe being made from a composite material and having an end section with an end section inner surface that tapers inwardly,

the assembly including a reinforcing element having a first portion positioned inside said end section, said first portion having an outer surface shaped to correspond to the shape of the end section inner surface,

the reinforcing element including a second portion having an abutment region proximate the pipe end.

According to another aspect of the present invention there is provided an assembly including

a first pipe having a first pipe end section with a first pipe end section inner surface that tapers inwardly,

a first reinforcing element having a first portion positioned inside said first pipe end section and having an outer surface shape corresponding to the shape of the first pipe end section inner surface, the first reinforcing element including a first abutment region,

a second pipe having a second pipe end section with a second pipe end section inner surface that tapers inwardly, a second reinforcing element having a second reinforcing portion positioned inside said second pipe end section and having an outer surface shape corresponding to the shape of the second pipe end section inner surface, the second reinforcing elements including a second abutment region, and

a locking device configured to limit axial movement of the first abutment region relative to the second abutment region.

According to a further aspect of the present invention there is provided an assembly including a first pipe having a first pipe end section with a first pipe end section inner surface that tapers inwardly, the first pipe including a first abutment region, a second pipe having a second pipe end section with a second pipe end section inner surface that tapers inwardly, the second pipe including a second abutment region, and a locking device configured to limit axial movement of the first abutment region relative to the second abutment region.

According to a further aspect of the present invention there is provided an assembly including a first hollow structure having a first end section with a first end section inner surface that tapers inwardly, the first hollow structure including a first abutment region, a second hollow structure having a second end section with a second end section inner surface that tapers inwardly, the second hollow structure including a second abutment region, and a locking device configured to limit axial movement of the first abutment region relative to the second abutment region.

The abutment regions may be radial flanges integral with the respective structures or provided as part of an additional reinforcement component per the first aspect of the invention.

According to a further aspect of the invention there is provided a pipe defining a tapered end having a cross-section section substantially in the shape of an involute. Preferably the involute is and involute of a circle.

The invention will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 is a cross-section of a first pipe and a second pipe according to the present invention,

Figure la is a cross section of the first pipe of Figure 1 showing the geometrical construction thereof,

Figure 2 is a cross-section of a locking ring used to couple the pipes of Figure 1 together,

Figure 3 shows how the locking ring of Figure 2 is assembled onto one of the pipes of Figure 1,

Figure 4 shows how the locking ring is secured to one of the pipes of figure 1, Figure 5 is a cross section view showing the pipes of Figures 1 and 2 assembled, Figure 6 shows the first pipe of Figure 1 mounted on a mandrel,

Figure 7 is an enlarged view of part of Figure 6,

Figure 8 is a cross-section of a further embodiment of a first pipe and a second pipe according to the present invention,

Figure 9 is a cross-section of a further embodiment of the first pipe according to the present invention,

Figure 10 ia a cross-section of a still further embodiment of a first pipe and a second pipe according to the present invention, and,

Figure 11 is a close up view of a part of the pipes of figure 10.

With reference to figures 1 to 5 there is shown an assembly 10 including a first pipe assembly 12, a second pipe assembly 14 and a locking device 60 including a locking ring 16. The first pipe assembly includes a first pipe 20 having a mid section 22 and an end section 24.

The first pipe 20 is made from a fibre reinforced composite material. The fibres may be any type of fibre including high strength fibres such as fibre glass, aramid fibre (Kevlar), carbon fibre and the like. The fibres are held together by matrix of any suitable type, such as a plastic resin. The first pipe has an inside Al and outside Bl . In this case the first pipe is circular and the mid section 22 is cylindrical having an axis CI . As such, the cross-section area of the mid section along the length of the mid section is constant. However, the end section 24 tapers inwardly towards the end 26 of the first pipe 20. In particular the end section 24 has an inner surface 28 which tapers inwardly towards the end 26 of the first pipe 20.

The cross section of the tapered region (i.e. the generatrix) is substantially in the shape of an involute (or evolvent) curve, which advantageously minimises stresses in the pipe 20. Referring to figure la, the pipe end section 24 is the involute of the circle 1 starting from point Zl and extending through an angle of 18 degrees. The circle 1 is of radius r equal to R / (pi - 1) where R is the radius of the pipe mid section 22. The circle lies on the opposite side of the axis CI to the involute curve and touches the axis CI .

The first pipe assembly 12 also includes a reinforcing element 30. The reinforcing element 30 has a first portion 32 and a second portion 34. The first portion 32 tapers inwardly towards the second portion 34. An outer surface 33 of the first portion has a shape that corresponds to that part of the inner surface 28 that faces the outer surface 33. The wall thickness T of the first pipe 20 is generally constant in section 22 but will then gradually increase in thickness in section 24.

The second portion 34 includes a radially orientated flange 36, which in this case is orientated outwardly. The second portion 34 also includes a generally cylindrical rim 38 which will be further described below. As will be appreciated, due to the tapering nature of the first section 32 and due to the radially orientated outwardly facing flange 36, the reinforcing element 30 is mechanically secured relative to the first pipe 20 so as to create the first pipe assembly 12. The second pipe assembly 14 includes a second pipe 40 having a mid section 42 and an end section 44. In this case end section 44 is identical to end section 24 and mid section 42 is identical to mid section 22. The mid section has an axis C2, and the pipe 40 has an inside A2 and an outside B2. Second pipe 40 has an end 46 and the end section 44 has an inner surface 48. The second pipe assembly 40 also includes a reinforcing element having a first portion 52 identical to first portion 32. The reinforcing element 50 also includes a second portion 54 which includes a radially orientated flange 56. However, in this case the reinforcing element 50 does not include a rim equivalent to rim 38 of reinforcing element 30. Nevertheless, it will be appreciated that due to the tapering shape of the outer surface 53 of the first portion 52 and the flange 56 which is orientated outwardly, the reinforcing element 50 is mechanically secured axially relative to the second pipe 40 thereby providing the second pipe assembly 14.

The locking ring 16 forms part of a locking device 60. The locking ring 16 is generally annular and includes a first recess 61 and a second recess 62. The first and second recesses are separated by a support flange 63. The first recess 61 has a first locking surface 64 and the second recess 62 has a second locking surface 65. The radially orientated flange 36 has an outwardly facing surface 36A and an axially facing surface 36B. The radially orientated flange 56 similarly has an outwardly facing surface 56 A and an axially facing surface 56B. The outwardly facing surfaces 36A and 56A are circular having the same diameter. The axially facing surface 36B faces the opposite end of the first pipe assembly. The axially facing surface 56A faces the opposite end of the second pipe assembly 14. The support flange 63 has a radially inwardly facing surface 63A having a diameter slightly larger than the diameter of the outwardly facing surfaces 36A and 56A to allow for assembly as will be described below. The locking device 60 further includes a first locking element 66 and a second locking element 68. Locking element 66 is in the form of a plurality of locking keys 67 (only one of which is shown).

Locking key 67 is arcuate when viewed in the direction of arrow D and includes an abutment surface 70 and an abutment surface 71.

Locking element 68 is in the form of a plurality of locking keys 69. Locking key 69 is identical to locking key 67 and includes abutment surfaces 72 and 73. Surrounding the locking ring 16 is a sleeve 76 having a cylindrical outer surface 77 of substantially the same diameter as the outer surface of the first pipe 20 and second pipe 40. The sleeve has first and second tapering inner surfaces 78 and 79, the shape of which generally matches the shape of the adjacent outer surface of the first pipe and second pipe respectively.

The locking ring will typically be made from a metal, such as steel. The sleeve 76 will typically be made from a composite material (e.g. fibre reinforced composite material). The sleeve 76 and locking ring 16 are provided as a sleeve assembly 75.

Coupling of the first pipe assembly 12 to the second pipe assembly 14 is achieved as far as:- The sleeve assembly 75 is slid onto the end of the first pipe assembly 12 as shown in figure 3. As can be seen the radially inwardly facing flange 63 A partially overlaps the outwardly facing surface 36A of the radially orientated flange 36. In this manner, engagement between the radially inwardly facing surface 63A and the outwardly facing surface 36A ensures that the sleeve is positioned concentrically with the first pipe assembly 12.

The arcuate extent of the locking key 67 can be varied to suit the particular installation, but, for explanatory purposes it is assumed that the arcuate extent of each locking key 67 is 10° arc when viewed in the direction of arrow D. It will be noted that the arcuate extent is also dependent on the diameter of the pipe, and larger pipes will tend to have more locking keys (each of which will extend over a smaller arc). The sleeve assembly 75 has two radially orientated holes 80 and 81 (see figure 4), the arcuate extent of each hole being slightly more than 10°. Each hole passes through both the sleeve 76 and the locking ring 16. It will be noted that the number of holes may be varied depending on the circumstances.

Once the sleeve assembly 75 has been slid onto the first pipe assembly 12 as shown in figure 3, a first locking key 67 can be slid radially down through hole 80 so as to be received in the first recess 61. That first locking key can then be moved circumferentially so as to free the space beneath the radially orientated hole 80 whereupon a second key can be inserted into the first recess 61. The second locking key 67 can then be moved circumferentially which in turn will move the first lock and key circumferentially. The process can be repeated until thirty-six keys have been inserted through radially orientated hole 80.

As best seen in figure 5, the abutment surface 70 of each locking key 67 will be engaged with the first locking surface 64 of the locking ring 16 and the abutment surface 71 of each locking key 67 will be engaged with the axially facing surface 36B of the radially orientated flange 36. Thus, once all thirty-six locking keys 67 have been assembled, it will not be possible to remove the sleeve assembly 75 from the first pipe assembly 12, i.e. it will not be possible to slide the sleeve assembly 75 in the direction of arrow E relative to the first pipe assembly 12. As such, when the locking keys 67 are in place the locking surface 64 of the locking device is axially secure relative to the reinforcing element 30.

Next, the second pipe assembly is moved into position, in particular to a position where the radially orientated flange 56 is adjacent to the radially orientated flange 36. As the second pipe assembly approaches the first pipe assembly the generally cylindrical rim 38 acts to guide the two pipe assemblies into their correct position. As the second pipe assembly nears its final position, the outwardly facing surface 56A will slide underneath the radially inwardly facing surface 63A thereby correctly aligning the axis CI with the axis C2. Once in this position 36 locking keys 69 can sequentially be fed through the radially orientated hole 81 in a manner similar to the assembly of the 36 locking keys 67 through the radially orientated hole 80 as described above. When finally assembled, the abutment surfaces 72 of each locking key 69 will be engaged with the second locking surface 65 and the abutment surfaces 73 of each locking key 69 will be engaged with the axially facing surface 56B as best seen in figure 5. Under these circumstances it is not possible to move the second pipe assembly 14 in the direction of arrow E relative to the locking device 60, and as such the second locking surface 65 of the locking device 60 is secured axially relative to the reinforcing element 50 of the second pipe assembly. When finally assembled, the locking device 60 therefore limits the axial movement of the first radially orientated flange 36 relative to the second radially orientated flange 56.

As best seen in figure 5, between the radially orientated flange 36 and the generally cylindrical rim 38 there is a concave arcuate surface 82. The radially orientated flange 36 includes a flat O-ring contact region 83 and the generally cylindrical rim 36 includes a flat O-ring contact region 84. The reinforcing element 50 includes a convex arcuate surface 85, the shape of which corresponds to the concave arcuate surface 82. The reinforcing element 50 includes a recess 86 and a recess 87. Positioned partially within the recess 86 and in contact with the flat O-ring contact region 83is a seal in the form of an O-ring 88. Positioned partially within the recess 87 and in contact with the flat O-ring contact region 84 is a seal in the form of an O- ring 89.

As shown in figure 5, the first pipe assembly 12 has been coupled to the second pipe assembly 14 but, as yet, no internal pressure has been applied to the pipe. Depending upon the particular circumstances, if the locking ring 16 is relatively stiff er (when considering hoop strain) than the first pipe 20 and the second pipe 40, then under pressure the diameter of the first and second pipes 20 and 40 will increase more than the diameter of the locking ring 16. This in turn will cause the left hand end of the reinforcing element 30 (when viewing figure 1) to expand more than the right hand end of the reinforcing element 30. Similarly, the right hand end of the reinforcing element 50 will expand more than the left hand end of the reinforcing element 50 (the right hand end of the reinforcing element 30 and left hand end of the reinforcing element 50 being restrained by the locking ring 16).

This differential expansion will cause slight relative movement between the concave arcuate surface 82 and the convex arcuate surface 85 such that, when viewing figure 5, the concave arcuate surface 82 appears to rotate clockwise slightly and the concave arcuate surface appears to rotate anticlockwise slightly. Nevertheless, because of the arcuate nature of these two surfaces they are maintained in close proximity to each other thereby enabling the seals 88 and 89 to properly seal the pipe.

It will be noted that under this load condition, the outer ends of the surfaces 82, 85 will be urged together, compressing the O-ring 88 and increasing the sealing effect. By correct positioning of the O-rings, such self sealing effects can be tailored to the pipe load case.

Once the first pipe assembly and second pipe assembly have been coupled together with the locking device 60, if the assembly 10 is subjected to a bending load then that portion of the surfaces 82 and 85 on the compression side of the pipe will move slightly relative to one another as described above. Those parts of the surfaces 82 and 85 on the tension side of the joint will move in an opposite sense, but nevertheless, because the concave arcuate surface 82 matches the concave arcuate surface 85, the two surfaces will be maintained in close proximity to one another and therefore that part of seals 88 and 89 on the tension side of the joint will still be able to operate correctly and maintain a seal.

The left-hand end (not shown) of the first pipe assembly 12 is identical to the left- hand end of the second pipe assembly 14. The right-hand end (not shown) of the second pipe assembly is identical to the right-hand end of the first pipe assembly. Thus, the first and second pipe assemblies are identical and each pipe assembly has a "male" reinforcing element 30 and a "female" reinforcing element 50. In further embodiments the left-hand end of the first pipe assembly may be identical to the right-hand end of the first pipe assembly and the right-hand end of the second pipe assembly may be identical to the left-hand end of the second pipe assembly. Under these circumstances the first pipe assembly will have two "male" reinforcing elements and the second pipe assembly will have two "female" reinforcing elements.

The first pipe assembly 12 is manufactured as follows:- As best seen in figures 6 and 7, an elongate mandrel 90 is provided having a mid section 91 corresponding to mid section 22 and having an end section 92 corresponding to end section 24. Part way along the end section 92 the mandrel is stepped inwardly at step 93. The height H of the step equates to the thickness J of that part of the reinforcing element 30 immediately adjacent the step 93. The reinforcing element 30 is assembled onto the mandrel 90 as shown in figures 6 and 7 and because the height H is the same as the thickness J, there is no step between the outer surface of the mandrel and the outer surface of the reinforcing element 30 where they meet. The opposite end of the mandrel (not shown) includes a similar step and receives a reinforcing element identical to reinforcing element 50. Once the mandrel has been assembled with appropriate reinforcing elements, the pipe 20 can be formed by covering the mandrel and reinforcing elements with a resin material and fibre reinforcement. Typically the fibre reinforcement will be wound onto the mandrel. In this way an even wall thickness T can be provided and locally the wall thickness can be increased, for example near the end 26 of the pipe 20. Because there is no step where the mandrel meets the reinforcing element, the wall thickness of the pipe is constant in this area, and hence no stress raisers in the pipe itself occur in this area. Once the resin has cured the mandrel is then collapsed in a known manner and withdrawn from the pipe. The mandrel can either be withdrawn through reinforcing element 30 or it can be withdrawn through the opposite end.

Should the pipe be for passage of a fluid flow, and losses from boundary layer separation be unacceptable then the manufacturing process may be modified to make the pipe - reinforcement join flush. In this instance, the mandrel 90 would not have a step 93, and would be smooth. The reinforcing element 30 would be assembled onto the mandrel and the composite pipe formed there over with an integral step such that the inner surface of the reinforcing element and pipe are flush. This may be achieved by laying up extra fibre layers throughout the main section of the pipe, and having fewer layers over the reinforcing element. The lack of a step on the pipe interior will reduce separation of the flow boundary layer and reduce turbulence / vortices which may create undesirable forces on the pipe inner, as well as causing vibration and energy losses.

As described above, the locking ring 60 will typically be made from a metal. Similarly the locking keys 67 and 69 and the reinforcing elements 30 and 50 will be made from metal, typically steel. Such materials are better able to withstand the separating forces applied to the coupling when the assembly is pressurised internally.

As can be seen from figure 5, the end 26 of the first pipe 20 is positioned radially within the locking keys 67 and also radially within the locking ring 16. Similarly the end 46 is provided radially within the locking key 69 and the locking ring 16. As such, the coupling system provides a particularly compact system, note in particular that ends 26 and 46 are separated only by the thickness of the radially orientated flange 36 and the thickness of the radially orientated flange 56.

Whilst an assembly according to the present invention can be used on any size of pipe, typically it may be used on pipe diameters of 200 mm or more.

As noted above, the cylindrical outer surface 77 has a diameter substantially equivalent to the outer diameter of the mid portion of the first pipe 20 and second pipe 40. As such, the external diameter of the pipe assembly and sleeve is substantially constant, and in particular there are no projecting parts of the coupling assembly. This is particularly useful when the pipe is to be used for oil drilling and the like or when the pipe needs to be fed through a pipe laying system, for example a set of rollers on the stern of a ship where the pipe is being laid under water. Because the sleeve 76 extends axially over the pipe ends, it reacts any bending loads placed on the pipe joint area, lowering the stresses at the joint by providing an alternative load path.

Whilst the locking element 66 and 68 as described above are in the form of separate locking keys, in further embodiments alternative locking elements could be used, in particular a single elongate key could be fed tangentially into recess 61 or 62. For example a locking strip as shown in the Strong Installation Manual REP320/REV02/04/01, issued 1 April 2001, future pipe industries BV could be used. Alternatively a locking clamp could be used.

Figures 1 to 7 show an arrangement with outwardly facing radially orientated flanges. With reference to figure 8 there is shown a second embodiment of an assembly 110 with components that fulfil the same function as those of assembly 10 labelled 100 greater.

As can be seen, the inner surface of the end sections of pipes 120, 140 taper inwardly. The outer surfaces of the reinforcing elements 130, 150 are shaped to correspond to the tapering inner surface of the end sections of the pipes 120 and 140. In this case the radially orientated flanges 136 and 156 face inwardly. As such the locking ring 116 is positioned radially inwardly of the radially orientated flanges 136 and 156. The pipe 120 has an inside A3 and an outside B3 and the pipe 140 has an inside A4 and an outside B4. In this case a sleeve 176 is a separate component from the locking ring 116.

The first pipe assembly 112 is coupled to the second pipe assembly 114 to form the assembly 110 as follows:-

The sleeve 176 is slid over the end of the first pipe assembly 12 and the locking ring 116 is positioned inside the radially inwardly facing radially orientated flange 136. The locking element 166 is installed. In this case a locking element 166 comprises a series of locking keys 167 and they are assembled through a hole (not shown) in the locking ring 116 in a manner similar to the assembly of locking key 67. Once this has been carried out the second pipe assembly 114 is then positioned in place with the radially orientated flange 156 being positioned outboard of the support flange 163 and the locking element 168 is installed. In this case the locking element 168 comprises a series of locking keys 169 which are installed through a hole (not shown) similar to the manner in which the locking keys 69 are installed.

As can be seen, this installation is particular compact, since end 126 is able to abut end 146. Figure 9 shows an alternative first pipe assembly 212 that can be assembled with the second pipe assembly 114 and a set of locking keys 169 and a sleeve 176 to form an assembly. As will be appreciated the reinforcing element 130, locking ring 116 and locking keys 167 have all been combined as a single unitary component 230. The first pipe assembly 212 therefore comprises the first pipe 220 and the reinforcing element 230. The first pipe assembly 212 can be manufactured by assembling the reinforcing element 230 onto a suitable mandrel, applying a resin material and fibre reinforcements around the mandrel and around the reinforcing element, allowing the resin to cure, collapsing the mandrel, and removing the mandrel through the reinforcing element 230.

Figure 10 shows and alternative first pipe assembly 312 and an alternative second pipe assembly 314. The first pipe assembly includes a first pipe 320 having a mid section 322 and an end section 324. The first pipe 320 has an inside Al and outside Bl .

However, the end section 324 tapers inwardly towards an end 326 of the first pipe 20. In particular the end section 324 has an inner surface 328 which tapers inwardly towards the end 326 of the first pipe 320.

The first pipe assembly 312 also includes a reinforcing element 330. The reinforcing element 330 has a first portion 332 and a second portion 334. The first portion 332 tapers inwardly towards the second portion 334. An outer surface 333 of the first portion has a shape that corresponds to that part of the inner surface 328 that faces the outer surface 333.

The second portion 334 includes a first axial protrusion 1002, and a second, spaced axial protrusion 1004 having a circumferential groove 1006 defined therebetween. The second pipe assembly 314 includes a second pipe 340 having a mid section 342 and an end section 344. In this case end section 344 is identical to end section 324 and mid section 342 is identical to mid section 322. The pipe 340 has an inside A2 and an outside B2. Second pipe 340 has an end 346 and the end section 344 has an inner surface 348. The second pipe assembly 340 also includes a reinforcing element 350 having a first portion 352 identical to first portion 332. The reinforcing element 350 also includes a second portion 354. The second portion 354 includes a first axial protrusion 1008, and a second, spaced axial protrusion 1010 having a circumferential groove 1012 defined therebetween.

A metal ring 1016 is provided, being endless and having a plurality of radial thorough-bores defined therein.

A sleeve 376 is also provided having a cylindrical outer surface 377 of substantially the same diameter as the outer surface of the first pipe 320 and second pipe 340. The sleeve 377 is similar in shape and function to the sleeve 77. The sleeve 376 defines a plurality of radial bores 1018.

When the pipe assembly is assembled, the protrusions 1002, 1004, 1008, 1010 are interdigitated such that the protrusion 1008 fits into groove 1006, and the protrusion 1004 fits into groove 1012. The metal ring 1016 and sleeve 376 are disposed so as to surround the outer diameter of the pipe ends 326, 346. The bores formed in the sleeve 376, the metal ring 1016 and the outer three protrusions 1002, 1004, 1008 align and locking pins 1014 are inserted to retain the pipes together. The locking pins 1014 define a male thread for engagement with a female thread on the protrusions.

The assembly of figures 10 and 11 is particularly well suited to joining solid propellant rocket motor segments for aerospace applications. In this example, the segments have a diameter of 3m and 200 circumferentially spaced pins 1014 are used.

As will be appreciated, it will be possible to join three or more pipe assemblies to create a pipeline. Each pipe within the pipeline may be identical. To create a pipeline of three pipe assemblies 12 will require:

3 pipe assemblies 12,

144 locking keys, 2 seals 88,

2 seals 89, and

2 locking devices 60. As will be appreciated, the pipes within a pipeline need not be identical, in particular certain pipes may be of different length to other pipes. Furthermore, certain pipes may have "male" reinforcing elements on each end and other pipes may include "female" reinforcing elements on each end. As described above, the invention has been applied to assemblies of a first pipe and second pipe. However, the invention is equally applicable to coupling other generally elongate hollow structures, such as two parts of the fuselage of an aircraft.

The invention as been described in relation to coupling two pipes made from fibre reinforced composite material, though the invention is equally applicable to coupling structures which are not made from a composite material and/or do not include fibre reinforcement.

The invention, as described above, is in relation to the pipe assembly including a pipe and a separate reinforcing element having a radially orientated flange. However, the invention is equally applicable to a pipe, or other hollow structure that tapers inwardly towards its end and has a radially orientated flange wherein the radially orientated flange is made from the same material as the pipe or other hollow structure, i.e. the radially orientated flange is not provided on a separate component.