DE8910407U1 - Pipe section and associated electrofusion fitting - Google Patents

Description

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Kunststoffwerk Höhn GmbH ' '..'.,' 0.Z. 4414

0-5439 Höhn/Hesterwald 1

Pipe piece and associated electro-welding fitting

The innovation concerns a pipe section and an associated electrofusion fitting for carrying out a weldable connection of plastic profile pieces and fittings with the same outside and inside diameter, preferably for installation in sewage pipes.

Secondly, it is known from DE-OS 31 Ti 079 to insert plastic pipe sections in front of defective pipes, in particular sewage pipes made of concrete or stoneware, and to connect them firmly together. In this way, the defective pipe does not need to be exposed, so the pipe can be pushed into the defective pipe from an excavation pit or from an existing sewage shaft.

Various measures have been proposed to date for connecting such pipe sections. In DE-OS 31 27 079, the connection between two pipe sections is designed as a plug connection, in which one pipe end has an outer cone and the pipe end that interacts with it has an inner cone, and in which one pipe end has a groove and the pipe end that interacts with it has an annular projection that can be locked into the groove by elastic deformation.

However, such a pure plug-in connection is neither sufficiently tight nor is its longitudinal force-fit guaranteed.

According to DE-GMM 85 29 159, 86 03 628 and 87 00 616, the leak-tightness problem is to be solved by inserting an elastic sealing ring. However, since the commonly used elastomers have poor aging resistance and a high swelling capacity, there are considerable concerns about exposing such composites to the aggressive effects of waste water for decades.

The best results in terms of tightness, strength of the bond and resistance to aging are achieved by welding the

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0,Z.4414

In DE-GM 84 28 374 and DE-OS 36 00 156, welded joints are proposed in which the individual pipe sections are inserted into one another at the ends, with one end in each case being designed as a socket part and carrying a winding of electrical resistance wires. In the latter case, the ends of the opposing plastic pipes are designed to be parallel to ^one another and conical. This achieves a large-area, tight and reliable sealing connection. The resistance wires remain in the connection area and are lost.

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However, this state of the art has the disadvantage that the pipe sections that have a heating coil on one side require complex packaging. In order to achieve a perfect weld, both surfaces must be clean and dry. This is particularly critical for the part that has the heating coil, while the counterpart can simply be cleaned by wiping it before being put together. For reasons of handling, it would be desirable if a simpler solution could be found that would reduce the packaging effort to a large extent and that would not require attention to the correct insertion of the respective side during assembly. In addition, the required contact pressure should be achieved using the simplest possible tools.

The plastic pipe sections used here have two identical socket ends 1 with an inner cone (see Fig. 1). They are usually manufactured by extrusion and subsequent machining. The associated electrofusion fittings 2 have an outer cone on both ends which is complementary to the socket cone (see Fig. 1). In Fig. 1, to illustrate the principle, they are inserted into a socket end with the earth on the right, while on the left end a heating coil, in this preferred case a bifilar heating wire 3, is shown partly in plan view. The electrofusion fittings are made of the same material as the plastic pipe sections and are also usually manufactured by extrusion and subsequent machining; however, they can also be obtained by injection molding or other plastic molding processes. The two spigot ends of the fittings are

O.Z. 4414

provided with a heating winding using any method known in the art; they can be wound with heating wire 3, for example (see Fig. 1) or covered with a flat heating element cut out in a meandering shape (see Fig. 2). In a preferred embodiment, the socket end has an annular groove 4, which is used to attach a pressing device during the welding process.

The present weldable connection with the same outside and inside diameter is particularly suitable for so-called "short pipe relining" (see e.g. DE-OSS 31 27 079 and 34 13 294); for the reasons mentioned above, it represents an improvement over the previously known systems with rubber seals. In the short pipe relining process, short pipe sections are introduced into a pipe to be renovated (e.g. through a shaft structure) and assembled to form a new pipe in the old route. In order to achieve a good weld, it is important that the socket end is completely clean before welding; it must therefore be cleaned, e.g. by wiping or with the help of water and compressed air. A significant advantage of the system according to the invention is that only the fitting has to be packaged as a relatively small part.

A particular advantage of the double-conical electrofusion fitting according to the invention is that the required joining force can be applied via two ring grooves 4 and a clamping device. This creates high tensions in the joining surface over the cone angle (preferably 8 to 15 °), which results in good welding. The quality of this is further improved by the fact that the displacement of the spigot end into the socket part during the welding process leads to a shear deformation of the melt. In this way, a tight and longitudinally force-locking connection is obtained. If the fitting and socket are correctly designed, practically no welding bead is created on the inside of the pipes.

Due to the strong welding, the connection can also be used for internally or externally pressurized pipes and lines according to the
Manufacturers can be used.

As materials for this innovation, equal outside diameter
All thermoplastics that can be welded with a heating element can be used for welded pipes. Examples include polyethylene, polypropylene, polyvinylidene fluoride, polyamide, polybutene or polyester. PE-HD is preferred.

Claims (7)

1 "·. O.Z. 4414 Protection claims: 1. Pipe section and associated electrofusion fitting made of thermoplastic material for producing a welded pipe with the same outside diameter, characterized in that a) the pipe section has two identical socket ends (1) with an internal cone; b) the electrofusion fitting (2) has a Has an outer cone that is complementary to the socket cone and can be provided with a resistance heater. 2. Pipe section and fitting according to claim 1, characterized in that the cone angle is 8 to 15 °. 3. Pipe section and fitting according to claims 1 and 2, characterized in that the socket ends have an annular groove (4). 20 4. Pipe section and fitting according to claims 1 to 3, characterized in that the outer cones of the fitting are wound with heating wire (3) 51 nu. 5. Pipe section and fitting according to claims 1 to 3, characterized in that the outer cones of the fitting are covered with flat, meander-shaped heating elements. 30 6. Pipe section and fitting according to claims 1 to 5, characterized by that both are made of PE-HD. 7. Pipe section and fitting according to claims 1 to 6 for the rehabilitation of sewage pipes using short pipe relining.