PIPE JOINT

Abstract: A pipe joint where a first pipe (1) and a second pipe (2) are joined together by placing a sleeve (3) between the pipes. The sleeve (3) is provided with at least one inward curved projection (3a) and the inner pipe (2) with a groove (2a) on the outer surface, the projection (3a) setting into the groove (2a).

Description: PIPE JOINT The invention relates to a pipe joint for joining together a first pipe and a second pipe, the pipe joint comprising a sleeve, the sleeve being meant to be positioned inside the end of the first pipe and the end of the second pipe being meant to be positioned inside the sleeve, and means for preventing an axial movement of the pipes to be joined that would open the joint. In pressure pipe use, forces proportional to the medium pressure in a pipe are caused in pipe joints and sockets. A decisive factor for dimensioning a pipe socket is the peripheral stress arising in the pipe wall, the stress requiring the wall thickness of the socket to be at least the same as that of the rest of the wall. As disclosed in Finnish Patent 94902, for instance, it is often considered necessary to emphasize the strength properties of the socket portion especially in the peripheral direction, to achieve a tight and reliable pipe joint. The strength properties of the pipe portion are instead mostly directed both peripherally and axially according to the loads the pipe portion is subjected to. If the pipe is provided with a socket afterwards by expanding, the wall becomes thinner when expanded, and accordingly, the pipe blank has to be thicker at the place of the future socket than the rest of the pipe. This can be implemented for instance in such a way that, at the manufacture, the draw rate of the pipe is slowed down at the place of the future socket. However, a solution of this kind is uncomfortable and complicates the manufacture of a pipe. A thickening is known from U.S. Patent 4,428,900, for instance. At reducers, branch joints, bent angles or valves in a pipeline, there occur axial forces tending to open the joint. It would be most ideal if the pipe joint itself were provided with a mechanism preventing the opening, but in pipes provided with sockets this is not possible because of the big forces caused by locking means and the dimensional accuracy required. In practice, the locking problem is solved for example by casting the problematic places in concrete or by winding cast iron bands interconnected by bars around the joined pipes. Moreover, a solution to reinforce a socket is known from Finnish Publication 97036, for instance, where a sufficient axial and radial strength of a locking solution inside the socket is achieved by a reinforcement outside the socket. A third problem associated with the use of a pipe socket consists in after-shrinkage of sockets. The socket tends to revert to its original measures and to make a joint is difficult, especially if pipes have to be stored exposed to sun shine, for example, for a long time after the socket has been made. In these conditions, it is difficult to make sockets with accurate measures, and especially difficult to make sealing grooves having accurate inner measures, particularly if there are many of them. This is an especially severe problem with pipes made of polyethylene PE, and therefore, these pipes are joined together by welding, in practice. Another common problem affecting a weak socket coupling is that the end of the pipe expands and the sealing ring slides out of the joint. An attempt has been made to solve this problem by using for example sealing rings which have a metallic or plastic support bracing the ring. This solution is disclosed for example in US Patent 4,030,872. Another solution has been a metal band installed around the pipe mouth. Molecule-orientated MOPVC pipes are made of polyvinyl chloride by blow moulding in such a way that a plastic tubular blank is positioned inside a mould, it is heated and expanded against the mould by blowing from the inside, as disclosed in British Patent 1 ,432,539. This allows a socket to be formed simultaneously in the pipe, but in this case the outer dimensions of the socket become accurate, whereas the inner, i.e. significant, dimensions are inaccurate. The same problem concerns for instance the method and apparatus for the manufacture of a biaxially orientated pipe by heating a tubular blank and by pressing it with fluid pressure against the mould, as disclosed in WO 98/13190. For the above reasons, more demanding socket applications are found among fittings manufactured by casting or injection moulding. WO 96/07048, for instance, discloses an injection moulded socket provided with a locking ring. However, the major part of the sockets of a pipe line are pipe sockets, and to replace them by fittings is not economically sensible. Further, a joint is known where the socket portion is manufactured by injection moulding and connected to the end of a straight pipe by butt welding. However, such a solution is complicated and expensive to implement, and moreover, all pipe materials used at present are not weldable. SE publication 465,792 discloses a pipe joint where a sealing ring is arranged between the socket and the insert end. The sealing ring is provided with an auxiliary portion which is supported to a groove at the insert end to resist to the opening of the joint. The joint is, however, fairly weak in the radial direction, because the socket formed to the outer pipe is the weakest point in the pipe. The pipe joint is therefore not suitable for pressure pipes. Furthermore, the dimensions of the portions inside the socket that rest against the insert end are inaccurate. Finnish Publication 945107 discloses a pipe joint for insert pipes, the end of a first pipe being expanded and a sleeve being positioned inside it, or the sleeve being expanded and the first pipe being positioned inside the sleeve. Subsequently, the end of a second pipe is positioned inside the sleeve. Such a joint is suitable for joining insert pipes, but it is difficult to achieve a tight joint and said joint would not last at pressure pipe use, but the force caused by pressurized medium would move the first pipe and the second pipe loose from each other quite easily. DE publication 3,003,040 discloses a pipe joint comprising a connecting piece with an insert and a clamping ring arranged inside it, the pipe to be joined being innermost in the joint. Between the insert and the clamping ring there is a wedge surface, the clamping ring being wedged against the pipe when the inner pipe is withdrawn from the joint. This kind of a pipe joint is most complex and it is very difficult to form the joint in such a way that the insert and the connecting piece can be made immovable with respect to each other. GB publication 2,028,945 discloses a socket joint suitable for vacuum cleaner hoses. The joint comprises a sleeve arranged around an inner tube. To lock the sleeve and the inner tube together, the sleeve has inner projections, the inner tube being provided with holes into which the projections are engaged. The outer tube end's diameter is so large that the tube can surround the sleeve. In the inside, the joint is provided with a spring ring which has an outward projecting pin. The inner tube, the sleeve and the outer tube have an opening through which the pin is engaged. The spring ring holds the pin in place, and the pin can be pressed down to release the outer tube, for example, from the sleeve. The pipe joint in question is very complex, and for example the withdrawal of the inner tube from the inside of the sleeve is most difficult. Moreover, the joint is cumbersome and cannot be applied for example to pipes carrying liquids, and particularly not to pressure pipes. US Patent 5,299,838 discloses a pipe joint comprising a connection slot and a sleeve arranged inside it with a screw thread. Inside the sleeve is arranged a clip assembly, the pipe to be joined being pushed inside the clip assembly. The clip assembly comprises retaining members made of bent plates arranged about the axis, the outer ends of the retaining members being arranged to clamp to inner grooves of the sleeve when the inner pipe is pulled outward, their inner ends being arranged to clamp to the outer surface of the inner pipe. In other words, the retaining members are meant to prevent the inner pipe from being withdrawn from the inside of the connection slot. This is a most complicated pipe joint and difficult to implement, and, in pressure pipe use in particular, it is extremely difficult to make sure the joint is tight. It is an object of the present invention to provide a fairly simple pipe joint with a good pull-out strength. The pipe joint of the invention is characterized in that a sleeve comprises at least one inward curved projection and the outer surface of a second pipe has a groove into which the projection sets. An essential idea of the invention is that inside the end of a first pipe to be joined is arranged a sleeve and the end of a second pipe to be joined, the sleeve being set between the first pipe end and the second pipe end and provided with at least one inward curved projection, the outer surface of the inner pipe comprising a groove into which the projection sets. A preferred embodiment is based on the idea that the sleeve is made by injection moulding. Another preferred embodiment is based on the idea that the projection is formed into the sleeve by die cutting, the projection being curved inward in connection with the die cutting. An advantage of the invention is that a most tight joint is obtained which is also suitable for pressure pipes and withstands the impact of the force caused by the medium in a pressure pipe, without the pipes that are to be joined together substantially moving in an axial direction with respect to each other. The sleeve compensates for radial forces, so the wall of the outer pipe does not have to be premade thicker at the joint than the rest of the pipe. Furthermore, the sleeve allows a pipe socket with an accurate inner measure to be obtained, because the sleeve prevents the after-shrinkage of the pipe. Injection moulding offers a simple way to manufacture the sleeve, because it allows accurate sleeve measures to be obtained and also difficult shapes to be manufactured, if needed. Furthermore, with injection moulding, it is easy to manufacture a sleeve where enough material is applied to critical points. The sleeve, the projection in the sleeve and the groove of the pipe inside the sleeve provide a simple means for preventing the axial, opening movement between the sleeve and the pipe. The reinforced sleeve significantly strengthens the socket in radial direction, thereby preventing the sealing ring from sliding out of the pipe joint, for example. The invention will be described in greater detail in the accompanying drawings, in which Figure 1 is a schematic, partly sectional side view of a pipe joint of the invention; Figure 2 is a sectional side view of a sleeve of the joint of Figure 1 ; Figure 3 is a schematic, partly sectional side view of another pipe joint of the invention; and Figure 4 is a schematic, partly sectional side view of another pipe joint of the invention. Figure 1 shows a pipe joint, in which a sleeve 3 is positioned inside the end of a first pipe 1 for forming a pipe socket and the end of a second pipe 2 is positioned inside the sleeve 3. The sleeve 3 is arranged substantially at the entire length of the socket formed into the first pipe 1 , the sleeve 3 thus increasing the socket portion's ability to resist to higher pressure at the entire length of the portion. In addition, the sleeve 3 is arranged substantially over the entire length the first and the second pipe 1 ,2 overlap. The end of the second pipe is arranged to rest against the sleeve 3, i.e. the second pipe 2 does not come in contact with the first pipe. The pipe joint of the invention is particularly suitable for pipes with large diameter. The inner diameter of the first pipe 1 , for example, may vary from 75 to 1000mm. The second pipe 2 may be an insert end, for example. The sleeve 3 can be positioned inside the end of the first pipe 1 for example by heating the end of the first pipe 1 and then forcing the sleeve 3 inside the end of the first pipe 1 by pushing. The outer diameter of the sleeve 3 is dimensioned bigger than the inner diameter of the pipe 1 , which makes the joint between the first pipe 1 and the sleeve 3 tight. The outer surface of the point of the sleeve 3 and the inner surface of the end of the pipe 1 can be provided with chamfehngs, which facilitate the pushing of the sleeve 3 into the pipe 1. The end of the first pipe 1 can also be heated and expanded and the sleeve 3 can be pushed into the expanded first pipe 1. Upon cooling, the first pipe 1 presses tightly on the sleeve 3 and the joint between the sleeve 3 and the first pipe 1 becomes tight automatically. In the manufacture of molecule-orientated PVC pipes or other pipes orientated in peripheral and possibly axial direction, the sleeve 3 can be positioned inside the first pipe 1 for example by blow moulding and then cooling the first pipe 1. The sleeve 3 is then pushed into the expanded end of the first pipe 1 and the first pipe 1 is heated so that it presses tightly on the sleeve 3. Further, molecule orientation can be utilized in such a way that, before joining, the sleeve 3 is stretched axially more than the pipe 1 , which expands the sleeve 3 when heated and presses it against the inner surface of the first pipe 1. The sleeve 3 can be positioned as far inside the first pipe 1 that the end of the first pipe 1 extends over the sleeve 3, whereby the end of the first pipe 1 can be bent on the face of the sleeve 3 and, in this way, it is possible to make sure that the sleeve 3 and the first pipe 1 remain immovable with respect to each other. Further, the outer surface of the sleeve 3 can be provided with grooves, protrusions, chamfered surfaces, or barbs 3b as shown in Figure 3, and the like, by the effect of which the sleeve 3 and the first pipe 1 remain immovable with respect to each other. When the pipes are made of polyvinyl chloride PVC, for example, the end of the pipe 1 can be swollen and softened using a solvent. When the solvent has evaporated, the sleeve 3 is very tightly attached to the pipe 1. The sleeve 3 is preferably made by injection moulding, due to which the sleeve 3 will have accurate measures and difficult shapes can also be manufactured. One advantage of an injection moulded sleeve 3 is that the projections 3a do not need to be die cut through the sleeve 3, but the wall of the sleeve 3 can be kept uniform to ensure its resistance to pressure. The sleeve 3 can be manufactured of a material, for instance a plastic reinforced with glass fibre, which is so rigid that the pressing of the first pipe 1 on the sleeve 3 does not substantially change the size and shape of the inner part of the sleeve 3. The first pipe 1 and the sleeve 3 are most preferably made of the same material, the material being additionally reinforced at the sleeve 3. The wall of the sleeve 3 can even be thinner than the wall of the pipe 1 , and yet, at the same time, stronger both in the axial and radial directions. The socket of the pipe 1 can have greater pressure resistance than the rest of the pipe 1 , and the tensile strength of the pipe 1 socket in the axial direction can be greater than that of the wall in the rest of the pipe 1. Reinforcements can be used, without the wall thickness increasing too much, to dimension the pressure resistance of the socket's inner sleeve so that the sleeve in itself is able to resist to the pressure the pipe is subjected to. Consequently, the wall of the pipe 1 where the sleeve 3 is to be inserted can be thin, its sole function being then to provide mechanical strength, such as impact resistance. The sleeve 3 can be made of materials such as polyethylene PE, cross-linked polyethylene PEX and polyvinyl chloride PVC. For example, the outer surface of the sleeve 3 can be attached with a hot-melt adhesive to the inner surface of the socket formed by the first pipe 1. Furthermore, the sleeve 3 can be placed to an injection moulding machine to press the socket of the first pipe 1 onto the sleeve. The sleeve 3 and the first pipe 1 are thus welded together extremely tightly. In addition, between the pipe and the sleeve, or for example into the sleeve, can be added welding wires or welding mass, for example, which allow the pieces to be welded together. Two-phased injection moulding, for example, allows a layer to be injection-moulded onto the outer surface of the sleeve 3, the layer being then easy to heat for example by applying high frequency heating and thereby welded to the inner surface of the socket formed by the first pipe 1. Another possibility is to use friction welding for example in such a way that the sleeve 3 is rotated or rotated back and forth by means of a rotary mandrel inside the pre-expanded first pipe 1 such that the sleeve 3 and the first pipe 1 are welded together. The sleeve 3 can be easily locked onto the rotary mandrel by means of the projections 3a of the sleeve. The sleeve 3 can be positioned inside the first pipe 1 at the factory and prefabricated products comprising the sleeve 3 and the pipe 1 can be stored for a desired time. The remaining part of the pipe joint can then be made at the site of use. The end of the second pipe 2 is positioned inside the sleeve 3. Inside the sleeve 3, it is possible to arrange a sealing groove, where a sealing ring 4 can be positioned to secure the tightness of the joint between the sleeve 3 and the second pipe 2. The sleeve 3 has an outward protrusion at the sealing groove, the sleeve 3 being thereby locked to be immovable with respect to the first pipe 1. The sleeve 3 is provided with one or more inward curved projections 3a. The outer surface of the second pipe 2, in turn, is provided with an annular groove 2a extending around the entire periphery of the pipe 2. Therefore, when the second pipe 2 is pushed inside the sleeve 3, the projection 3a bends, thereby allowing the pipe 2 to be pushed in. The second pipe 2 being pushed far enough inside the sleeve 3, the projection 3a bends into the groove 2a in such a way that the second pipe 2 and the sleeve 3 are locked in an axial direction with respect to each other, thereby providing a joint which has an extremely good pull-out strength and which can be used in pressure pipes as well. Another reason why the pipe joint is excellent for pressure pipes is that the sleeve 3 arranged at the socket portion enhances the socket portion's pressure resistance. The end of the second pipe 2 can be provided with a chamfering 2b that makes it easier to push the second pipe 2a inside the sleeve 3. The chamfering 2b and the annular groove 2a can be formed to the second pipe 2 at the same time, i.e. the chamfering 2b and the groove 2a are most preferably made using one and the same machine. The sleeve 3 can also be used without the locking effect in connection with a conventional second pipe 2 not provided with the groove 2a. In other words, the pipe joint is typically made by arranging the sleeve 3 inside the end of the first pipe 1 , the end of the second pipe 2 being then pushed inside the sleeve 3 and the end of the first pipe 1. Another way to make the pipe joint is to form a chamfering 2b and a groove 2a at the end of the second pipe 2, the sleeve 3 and the sealing ring 4 being then pushed onto the second pipe 2. The end of the first pipe 1 is then pushed onto the sleeve 3 and the end of the second pipe 2, after which the end of the first pipe 1 is fastened to the sleeve 3 by shrinking. Figure 2 shows the sleeve 3 provided with four projections 3a, of which three are shown in the Figure. The projections 3a are of the same structure as the wall of the sleeve 3, and they are preferably made by first injection moulding the sleeve 3 without the projections 3a, which are then die cut to the sleeve 3. In the die cutting, the projection 3a bends inward into the position shown in Figure 2. The end of the projection 3a is at a distance from the end of the sleeve 3, thus allowing a very firm sleeve 3 structure to be easily obtained. The sleeve 3 may most preferably be also made of an extruded pipe. The process then consist of cutting the pipe, followed by upsetting to form a sealing groove into the sleeve 3. The sleeve 3 is then die cut to form the projections 3a. All the above phases can easily be automated. When the sleeve 3 is made of cross-linked polyethylene PEX, the memory of the PEX material can be used when the projection 3a is formed. The projections 3a can be formed to curve inward at the same time when the sleeve 3 is cross-linked. The projections 3a can then be bent straight in normal temperature. When the sleeve 3 is re-heated, the projections bend inward due to the memory of the material, i.e. the heating of the sleeve 3 can be used to renew the pull-out strength of the joint in connection with re-installations, for example. A standard prior art pipe socket provided with a sealing ring is extremely slow to manufacture. The preheating of the pipe end, the forming of the sealing groove, and the subsequent cooling take a lot of time and the result is always somewhat insecure because the after-shrinkage of pipes made of polyolefins produces surprises. Compared with this, it is essentially quicker and more economical for example to separately extrude and manufacture the sleeve 3 and to push it into a slightly preheated pipe. In the prior art solution, costs are further increased by compressible cores, for example, that are needed to form the sealing groove. Furthermore, the inventive solution provides a better end result, because desired tolerances are very easily obtained. The degrees and/or directions of orientation of the materials of the pipe 1 and the sleeve 3 may differ from each other, and they can be modified to suit the purpose of use in question. Orientation may be, besides orientation of polymer molecules but also orientation of a possible fibre reinforcement. If the sleeve 3 is exposed to mainly peripheral loads and forces, the orientation is primarily peripheral. On the other hand, if the sleeve 3 is mostly subjected to axial forces, the orientation of the sleeve is mainly axial. The pipe 1 and the sleeve 3 can be manufactured of the same polymer, but their fillers and/or reinforcing materials, and the contents of the materials may differ from each other. The sleeve 3 preferably comprises reinforcing fibres, the radial expansion of the socket being thereby reduced. In the prior art solution it has not been possible to connect pipes of different material together for example by using a rubber ring socket joint because due to the differences in the heat expansion properties of the pipes, it has not been possible to fit the insert end into the sleeve in cold weather, for example. These problems do not occur when fibre-reinforced sleeve 3 is used because the heat expansion of a fibre- reinforced material is low. Furthermore, a sleeve 3 made of a suitable material and provided with sealings arranged on the inner and outer surfaces can be used together with pipes of varying materials, provided that the diameters of the pipes fit together. Without the sleeve 3, different tools would have to be used for each material when providing the sockets because the materials differ in shrinkage. Figure 3 is a partly sectional side view of another pipe joint of the invention. Outside the sleeve 3 may be arranged a sealing groove which can be provided with an auxiliary sealing 5. This auxiliary sealing 5 allows the tightness between the pipe 1 and the sleeve 3 to be secured. The sealing ring 4 and the auxiliary sealing 5 can be easily pressed to the sleeve 3 by means of two-phased injection moulding. The sealing ring 4 and the auxiliary sealing 5 can be made of for example cross-linked thermoplastic elastomere, such as rubber. This makes the socket structure significantly less expensive than a socket with a conventional rubber ring. The end of the first pipe 1 is provided with a collar-like additional reinforcement 6 of the pipe 1 mouth, which particularly increases the peripheral strength of the mouth. The cross-section of the groove 2a formed on the outer surface of the second pipe 2 can be either triangular or rectangular. A socket joint which has a good pull-out strength and which also allows the pipe 2 to move slightly inside the sleeve 3 can be obtained by arranging the distance between the counter surface of the projection 3a in the groove 2a and the end of the second pipe 2 to be smaller than the distance between the corresponding points on the sleeve 3, i.e. the distance of the projection 3a from the sleeve 3 portion that rests against the end of the pipe 2 as shown in Figure 3, or the distance of the projection 3a from the first pipe 1 portion that rests on the end of the pipe 2. The second pipe 2 cannot move to the left from the position shown in Figure 3 to any significant degree, i.e. the joint has an extremely good pull-out strength, but the pipe 2 can, however, move to the right slightly. In many plastic pipe lines this is very important because the coefficient of heat expansion for plastic is high. Figure 4 is a partly sectional side view of a third pipe joint of the invention. In the solution of Figure 4, the sleeve 3 only extends until the sealing groove formed to the first pipe 1. The sleeve 3 can therefore be discontinuous in the peripheral direction, i.e. it is not uniformly annular in shape. The tightness of the joint is in this case provided by the sealing ring 4 which is arranged between the first pipe 1 and the second pipe 2. The axial force that draws the joint open further increases the sealing effect of the sealing ring 4. The sealing ring 4 can be made of rubber, for example, and it can be vulcanized or glued to the end of the sleeve 3. The end of the second pipe 2 is arranged to rest against the first pipe 1. The drawings and the related specification are only intended to illustrate the idea of the invention. The details of the invention may vary within the scope of the claims. Consequently, the pipes 1 , 2 and the sleeve 3 may comprise more than one material layer. Outside the joint can be arranged an outer band to ensure that the sleeve stays inside the first pipe. The outer band can be for example a band made of stainless steel which is tightened onto the joint by means of suitable tools. The joint can be opened for example by pushing a thin-walled metal sleeve between the second pipe 2 and the sleeve 3 which bends the projection 3a away from the groove 2a in the second pipe 2 and the second pipe 2 can be withdrawn from the inside of the sleeve 3. The sleeve 3 can also be made of a material that expands relatively easily in the radial direction. The sleeve 3, for example, can then finally set into the sealing groove formed to the first pipe 1 only after the end of the second pipe 2 expands it there. The pipe joint of the invention can also be used in other pipes than pressure pipes meant for conveying pressurized water. It can be used for example in shielding pipes for telecommunications cables and other cables. The locking between the sleeve 3 and the first pipe 1 can then be implemented by shrinking only the first pipe 1 onto the sleeve 3, because the joint does not have to be completely tight. The socket into which the sleeve is arranged does not need to be cylindrical: a conical sleeve 3 can be inserted into a conical socket, which allows a small axial angle of the second pipe 2. By choosing suitable positions and/or length for the projections 3a and by making the groove 2a spiral, the second pipe 2 can be detached from the joint without a special tool simply by turning the second pipe 2 in the sleeve 3, and thus the projections push the second pipe 2 out along the screw line formed by the groove 2a.

Claims: CLAIMS I. A pipe joint for joining together a first pipe (1) and a second pipe (2), the pipe joint comprising a sleeve (3), the sleeve (3) being meant to be positioned inside the end of the first pipe (1) and the end of the second pipe (2) is meant to be positioned inside the sleeve (3), and means for preventing an axial movement of the pipes (1, 2) to be joined that would open the joint, characterized in that the sleeve (3) comprises at least one inward curved projection (3a) and the outer surface of the second pipe (2) has a groove (2a) into which the projection (3a) sets. 2. A pipe joint according to claim 1, characterized in that the projection (3a) is substantially of the same structure as the rest of the sleeve (3) wall. 3. A pipe joint according to claim 2, characterized in that the projection (3a) in the sleeve (3) is made by die cutting. 4. A pipe joint according to any one of the preceding claims, characterized in that the first pipe (1 ), the second pipe (2) and the sleeve (3) are of a plastic material. 5. A pipe joint according to claim 4, characterized in that the first pipe (1) is shrunk onto the sleeve (3). 6. A pipe joint according to any one of the preceding claims, characterized in that the sleeve (3) is manufactured by injection moulding. 7. A pipe joint according to any one of claims 1 to 5, characterized in that the sleeve (3) is manufactured by extruding. 8. A pipe joint according to any one of the preceding claims, characterized in that the outer groove (2a) of the second pipe (2) is annular. 9. A pipe joint according to any one of the preceding claims, characterized in that the pipe joint is arranged to be used in pressure pipes, the pipe joint comprising a socket portion at which the sleeve (3) is arranged, the sleeve (3) thus increasing the pressure resistance of the socket portion. 10. A pipe joint according to any one of the preceding claims, characterized in that the sleeve (3) is made of a plastic material and contains reinforcing fibres. II. A pipe joint according to any one of the preceding claims, characterized in that distance between the counter surface of the projection (3a) in the groove (2a) and the end of the second pipe (2) is smaller than the distance of the projection (3a) from the sleeve (3) portion or the first pipe (1 ) portion that rests against the second pipe (2). 12. A pipe joint according to any one of the preceding claims, characterized in that the pipe joint comprises a sealing ring (4) arranged between the sleeve (3) and the second pipe (2). 13. A pipe joint according to claim 12, characterized in that the sealing ring (4) is squeezed to the sleeve (3) by applying two-phase injection moulding. 14. A pipe joint according to any one of the preceding claims, characterized in that the sleeve (3) is arranged to only extend to the sealing groove formed to the first pipe (1), and that a sealing ring (4) is arranged between the first pipe (1) and the second pipe (2). 15. A pipe joint according to claim 14, characterized in that the sleeve (3) is discontinuous in the peripheral direction. 16. A pipe joint according to claim 14 or 15, characterized in that the sealing ring (4) is attached to the end of the sleeve (3) by vulcanizing or gluing. 17. A pipe joint according to claim 12 or 13, characterized in that the sealing ring (4) is made of cross-linked thermoplastic elastomere. 18. A pipe joint according to any one of the preceding claims, characterized in that the sleeve (3) is arranged inside the first pipe (1 ), the end of the second pipe (2) being then pushed inside the sleeve (3) and the end of the first pipe (1). 19. A pipe joint according to any of claims 1 to 17, characterized in that the sleeve (3) is arranged onto the end of the second pipe (2), the end of the first pipe (1) being then arranged onto the sleeve (3) and the end of the second pipe (2) and attached to the sleeve (3) by shrinking. 20. A pipe joint according to any one of the preceding claims, characterized in that the inner diameter of the first pipe (1 ) is at least 75mm. 21. A pipe joint according to any of the preceding claims, characterized in that the end of the projection (3a) is at a distance from the end of the sleeve (3).

Inventors: JAERVENKYLAE JYRI, JAERVENKYLAE, JYRI
Applicants: JAERVENKYLAE JYRI, UPONOR INNOVATION AB, JAERVENKYLAE, JYRI
Application year: 2001
Main classification: F16L21
IPC codes: F16L21, F16L37