The present invention relates to one in a pipe-connection included, with connecting device equipped pipe-end for at least one of the pipe-ends of preferably polyethylene-pipes for high media-pressures included in the pipe-connection and where said pipe-connection shows connecting parts for co-operation with an exterior casing for pulling together and retaining these connecting parts. The invention also relates to a method and a device for manufacturing this pipe-end, which is included in the pipe-connection and equipped with a pipe-connecting device.

Plastic pipes and especially polyethylene-pipes intended for high media-pressures, are today mostly connected by means of an electric butt-welding method. Other methods are also used where the pipe-parts which are to be connected are sealed and retained by applying a sealing ring and a clamping sleeve against the outer surface of the pipes.

However, the surface roughness of the outside surface of said polyethylene-pipes is bad, which causes leakage at high pressures. As a result these types of connections for pipes are approved only for transportation of water. But if you want to achieve a perfectly safe sealing when connecting these plastic pipes, using the electric butt-welding method is at present the only solution.

PVC (polyvinyl chloride)-pipes for high pressure are nowadays connected by cementing.

These pipes cannot be welded by the electric method. On the other hand, polyethylene-pipes cannot be cemented but must be electric welded.

Consequently, the electric butt-welding method requires access to electric current, which in itself is not very flexible, because you mostly have to apply the welding equipment on the very spot where the pipes are to be connected. Furthermore, this method is rather time consuming.

The object of the present invention is to eliminate the drawbacks described above and to produce a pipe-connection, where a pipe-end equipped with a connecting device of the kind WO 01/77567 PCT/SE01/00817 mentioned in the introduction and a method and device for its manufacturing are included.

The characteristics of the invention are set forth in the patent claims enclosed.

Thanks to the invention a pipe-connection has been accomplished, which in an extraordinary way fulfils its purposes and where at the same time the method of connecting by means of a fitting-device, used according to the invention, is fast and cheap to accomplish, and where at the same time the production cost for the connection itself according to the invention can be kept low. By the procedure of using this pipe-connection according to the invention especially for polyethylene-pipes a completely safe sealing also for high media pressure is achieved, without the need of any electric equipment. Using the pipe-connecting part, described in the introduction and included in the pipe-connection, it is possible to, besides connecting such pipe-lengths having connecting parts butt-welded in the factory, even pipes of any length can be connected. This method is based upon the fact that polyethylene, heated to a temperature of about 120 ° C becomes so soft that it is easy to cut into the material, and another condition is that the plastic material has a low heat-conduction coefficient, because the outer part of the pipe should for stabilization reasons not become soft, something which not happens if the temperature there is only about 110 ° C.

The invention is described more in detail below, by means of a shown example, referring to the enclosed drawings, on which Fig. 1 shows a schematic longitudinal cross-section of a connection between two plastic pipes according to the present invention, Fig. 2 shows a view from above of the connection shown in fig 1, Fig. 3 shows a cross-section through the connection along the line III-III in fig. 1, Fig. 4 shows a longitudinal cross-section of the in the pipe-connection according to fig. 1 included pipe-connecting part according to the present invention, Fig. 5 shows a schematic longitudinal cross-section of a device consisting of a fitting-device intended for the fitting of the pipe-connecting part shown in fig. 4 into a pipe-end and said WO 01/77567 PCT/SE01/00817 device is shown in a first moment when it has been positioned over and around the actual pipe-end and before the pipe-connecting part is pushed into the pipe, Fig. 6 shows the fitting-device of fig. 5 in a position where the pipe-connecting part has been pushed into the pipe and before the knife or the saw in the fitting-device has removed the excess material in the pipe, Fig. 7 shows a longitudinal cross-section of the pipe-end, including a finally fitted pipe- connecting part and with an applied, force resistant round flange for co-operation with one in the pipe-connection included exterior casing, Fig. 8 shows a longitudinal cross-section of the fitting-device itself, and Fig. 9 shows a view of the end of the fitting-device, shown in fig. 8.

As described in fig. 1 the invention, according to a shown example, consists of a pipe- connection 1 for polyethylene-pipes 2,3 intended for high media pressures. The pipe- connection 1 shows connecting parts 4,5 where at least one of them has a continuous cylindrical or conical shape and which are pulled and kept together by an exterior casing 6.

The exterior casing 6 consists of two halves 7 and 8, possible to pull together by means of screws 9 and nuts 10. In the shown example one of the connecting parts 4, consisting of a pipe 2, cut to any appropriate length, and with a pipe-connecting part 12, which may be manufactured in stainless steel or in other suitable material, is applied in the end 11 of said pipe 2, by means of a fitting-device 13.

The pipe-connecting part 12, shown more in detail in fig. 4, consists of a sleeve 14 with a flat contact surface 14', showing the same inside diameter all over its length but with at least two sleeve-parts 16 and 17 extending from the middle part 15 of the sleeve 14 in both directions said sleeve-parts in the actual case having different outside diameters. The first sleeve-part 16 having the smaller outside diameter, has a sharp-edged end 18 and a dimension somewhat larger than the inside diameter of the actual pipe-end 11. The sleeve-part 16 is insertable into the pipe-end 11, when a predetermined part 19 of the inside mantle-surface of the pipe 2 at the same time is cut away. The other sleeve-part 17 having the larger outside diameter, is of a dimension mainly as large as the outside diameter of the actual pipe-end 11 and is able to WO 01/77567 PCT/SE01/00817 co-operate with the parts belonging to the pipe-connection 1. The other sleeve-part 17 also shows on its outside mantle-surface 20 the contact-surface 14'intended for the pipe-end 11 and a round flange 21, made of polyethylene or metal, for co-operation with the outer casing 6, said round flange 21 having been pushed up upon the pipe-connecting part 12 and upon adjacent part of the pipe and has been positioned on the pipe-connecting part 12 by means of one in a groove 22'in the sleeve-part 17 applied force-resistant metal ring 22, made in two halves, and by means of a locating locking washer 23, which in its turn is attached into a groove 23'in the round flange 21.

The fitting device 13, used for attaching the pipe-connecting part 12 into the pipe-end 11 of the pipe 2, consists of an outer and inner cylindrical part 24 and 25 respectively, which parts have a length exceeding the length of the pipe-connecting part 12 and are centered relative to each other and are kept together by the end-part 26 of the cylinder 24. The two cylindrical parts 24,25 have a radial distance between them, forming an annular space 27, allowing the insertion of the pipe-connecting part 12 into the space 27 and into contact with the end-part 26. The inner cylindrical part 25 also shows a cavity 28 with a source of heat 29 for warming up the pipe-connecting part 12 as well as the actual pipe-end 11 from the inside, said pipe-end 11 being insertable into the forward part 27'of the space 27, into contact with the pipe- connecting part 12, before this has been inserted and located in the pipe 2. The fitting device 13 also shows on its inner cylindrical part 25 a sleeve 30, shrunk upon said cylindrical part, and one on its free end applied round saw or knife 31, with an outer diameter mainly corresponding to the inner diameter of the actual pipe 2, to make it possible to cut away the excess material 19 from the inside mantle surface of the pipe 2, after the pipe-connecting part 12 has been fastened.

In the shown example a gas burner 32 is used as heating source, but any other suitable heating device can be used to produce the necessary heating, e. g. induction heat, hot-air unit or the like. In case a gas burner is used, its orifice 40 reaches, as shown in fig. 5, in through the opening 41 in the end-part 26, allowing its gas flame to be spread and burned in the cavity 28.

To facilitate the fitting of the pipe-connecting part 12, the free end of the outer cylindrical part 24 may be equipped with a draw spring unit 33, of which the free end 34 is attachable at a small distance from the end of the actual pipe 2, in order to, after the application of the fitting device 13 on the pipe-end 11 but before the insertion of the pipe-connecting device 12 into the WO 01/77567 PCT/SE01/00817 pipe 2, attain an activated, strained state. Thus, by the upcoming spring force the pipe- connecting part 12 will, during the fitting and as a result of the heating, automatically be pushed into the pipe-end 11.

When the pipe-connecting part 12 is being fitted, it is placed in the bottom of the fitting device 13, said fitting device being pushed with easy running fit up upon the end 11 of the actual pipe 2, which has been cut off to the appropriate length. The inner cylindrical part 25 is being heated from the inside by means of for instance the gas burner 32 and heat from the sleeve 30 radiates to the inner surface of the polyethylene pipe and to the pipe-connecting part.

As is shown more in detail in fig. 5 the material on the inside of the pipe and also the thin part of the pipe-connecting part 12 is heated to the appropriate temperature during the fitting of the pipe-connecting part 12. Thanks to the spring force, acting on the fitting device 13, the sharp-edged pipe-connecting part 12 is being pulled automatically and/or by a helping hand from the fitter into the pipe 2, when the plastic has become soft enough. When the device has cooled down, the pipe-connecting part 12 is kept in place in the polyethylene pipe by a very strong grip, due to different coefficient of thermal expansion for polyethylene and steel.

The material, being pushed away during the fitting procedure by the pipe-connecting part 12, is cut away by the circular saw 31, applied in the front end of the fitting device 13, after slightly cooling down of the polyethylene-material, in which case the circular saw 31 is rotated forwards and backwards when the fitting device is simultaneously pulled out. This procedure involves a guarantee for the proper removal of the excess material. For compensating the reduction in strength in the pipe-end, the pipes intended for cutting to any length can be manufactured with thicker walls.

As is shown more in detail in fig. 7, the round flange 21, intended for co-operation with the exterior casing 6, is positioned on the pipe-connecting part 12 and on the adjacent part of the pipe and is locked to the pipe-connecting part by means of force-resistant metal ring 22 and the locking washer 23. The pipe 2 is now ready for connecting to an adjacent, second pipe 3 to form the pipe-connection 1, shown in fig. 1. For this purpose the free sleeve 17 of the pipe- connecting part 12 is being pushed into and seals against a sealing 35, consisting of an 0-ring, applied in an inward groove 36 in a joining device 37, consisting of a metal sleeve 38, shrunk or pressed into the connecting part 5 in the adjacent, free pipe-end of the pipe 3.

A connection of the actual pipes 2,3, where the pipe-ends show connecting parts 4,5 of the type described above, can be accomplished in the following way. One of the pipes 3 has in this connection an outer end 39, which has a larger inside diameter than the pipe itself and in said end 39 the connecting device 37 consisting of the metal sleeve 38 has been shrunk, while at the same time the other pipe 2, after cutting to appropriate length, is equipped with the pipe-connecting part 12, in the way described above. Thereafter the sealing 35 is placed in the groove 36 in the inside surface of the metal sleeve 38 and the pipe-connecting part 12 is being pushed into the metal sleeve 38, whereupon the two halves 7,8, forming the exterior casing 6, are brought to enclose the connecting parts 4,21,5, while simultaneously the halves 7,8 are pulled together in order to complete the pipe-connection.