DE3152022C2 - - Google Patents

Description

The invention relates to a method for producing a tubular Subject, wherein a thermoplastic in the form of a powder or Gra nulats with the addition of chemical crosslinking agents as well as additives and Auxiliary materials are subjected to high pressure in a pressure chamber, whereby the temperature of the mixture rises to about 110 ° C, whereupon the Mixing passed through channels of an extrusion device and still heated to cross-linking temperature within the extrusion device becomes.

Such a method is already known from DE-AS 16 79 826. Another method of a similar type for producing molded, ver netting polyolefinic materials by extrusion goes from the EP-A1 00 33 587. With these known methods, a ho mogeneous distribution of the crosslinking agent in the molding compound in particular advantageously ensured, thereby producing a consistently networked product is made possible. A such a product is particularly advantageous for the present invention arrested.

DE-OS 17 04 070 describes a method for producing a tubular plastic molding known in which the molding by means Radiation cross-linked, cut and stretched under Heating is fixed. A molecular structure is achieved which allows the object to be used again after further heating Take shape and dimensions before deformation. However, no con described continuous work process and also no chemical ver carried out.

DE-OS 29 40 719 describes a process for the production of Known shrink articles in which a preform extrudes finally networked and expanded in this state and through Cooling of this expanded blank, its state by freezing is fixed.  

If, for example, a shrink tube processed in this way closes pulled over pulling object, it shrinks when heated briefly about the crystallite melting point in its original shape and dimensions solution and there is a firm and resistant coating, which adapts to the shape of the object. Partial warming for the production of a tubular object as a functional and independent end product is not intended.

For transporting fluid media, for example in heating or Sanitary area, increasingly find plastic products and in particular Plastic pipes application. These materials have excellent Long-term resistance even at high temperatures and pressures on and are against most in both the sanitary and heating sectors occurring additives resistant. For example, if the pipes at Installation to be subjected to a sharp bend to about Fittings provided to be installed in an arrangement, so the Pipes can be fixed in the bent state and cast in if necessary, as right relatively strong restoring forces are present in the pipe and in the hoses are which counteract a strong bend. Will such a If, for example, the tube is bent, this creates a Kink with a reduced cross-section, resulting in an increased Flow resistance is generated. Certain deformations can be no tension at all afterwards or only with large ones To create difficulties.

The object of the invention is therefore a method for producing a to create a tubular object that at its bending points has the same cross section as the undeformed tube.

This object is achieved in accordance with the claim listed procedures.

Below are test examples for producing a specific one Deformation of cross-linked material of the type described above specified.  

example

Finely divided polyethylene is made with 2.5 percent by weight dicumyl peroxide mixed and the mixture obtained is introduced into a pressure chamber and subjected to a high pressure. The temperature of the material at the pressure chamber exit was approx. 110 ° C. The material passes through channels Extrusion device and is then heated to about 160 ° C. At this Temperature the crosslinking reaction takes place quickly and completely, and there is a tube of cross-linked at the exit of the mold Get polyethylene. This tube is in the same work process nuously through a mold and then through a water bath pulled and chilled. The molding tool reduces the Radius by at least 10%, preferably 20%.

If you designate the original shape with A , you get a reduced shape

B = A - Δ A ,

where Δ A is between 10% and 20%.

The invention is explained in more detail with reference to the drawing. Here shows

Figure 1 is an angled fitting with flange element.

Fig. 2 is a Venturi tube;

Fig. 3 is a double pipe member with inner spacer rings;

Fig. 4 also wrestle a double pipe piece with external spacing; and

Fig. 5a-e components of a pipe section with a T-connection.

If, for example, an angular deformation is to be carried out, as shown in FIG. 1, side 1 of the tube produced by the above-mentioned method is irradiated with hot air at a temperature of over 140 ° C. for a while. During this heating, the cross section is expanded, the material endeavoring to adopt the original shape. If the circumferential shape of the tube is heated unevenly, the tube will be angled, since the tube strives to increase the original thickness on the side 1 of the circumference due to the memory effect known per se, while this condition is not on the cooler side 2 more can be achieved.

This heating process therefore increases the radius 1 of the tube, which is reduced by 10% to 20%, to R 2 and finally to R 3 , while the radius R 4 again corresponds to the radius R 1 . The same applies to the wall thickness D 1 of the original thickness, which is also reduced by 10% to 20%. The wall thickness D 3 therefore corresponds approximately to the original wall thickness and this is smaller than D 2 and this in turn is smaller than the wall thickness D 1 . In this way it is achieved that a larger radius and a greater wall thickness are present precisely at the angular point, so that the flow losses due to constrictions which would otherwise occur in the case of contra-angles are avoided. The reductions of a pipe produced, for example, by extrusion can be carried out up to its yield point, so that the original state can be restored to the same order of magnitude with a corresponding subsequent heat treatment.

The elbow thus produced shows a permanent shape without any restoring forces and thus tensions act.

The flange part 12 , also shown in FIG. 1, is produced in a corresponding manner.

Another application example is metal pipes from the inside to be coated with plastic, for example in the case of already installed To seal damaged or porous areas.

For this purpose, for example, according to the above. Process herge adjusted polyethylene pipe by the extrusion process, for example 10% reduced in such a way that the tube thus reduced into the repairing metal pipe can be introduced.  

The length of the pipe to be inserted is chosen so that the repairing pipe parts are sufficiently bridged. After Introduction of the plastic tube, this tube combination is heated, so that the plastic inner tube is back by the reduced amount expanded and leans closely against the inner wall.

This heat treatment creates sufficient forces so that a good seal of the plastic pipe over the entire circumference and in a sufficient length to the inner jacket of the to be repaired Rohres takes place.

Another area of application is the production of Venturi nozzles from a single piece of pipe. Such a nozzle is shown in Fig. 2. A Venturi nozzle consists of a narrowing pipe part 3 and a gradually expanding pipe part 4 . If one starts from a primary jump tube 5 with the diameter R 4 and reduces such a tube to the diameter R 5 , the narrowing tube sections 3 and gradually widening tube sections 4 can be produced by subsequent heat treatments in a simple manner. The wall thickness 6 increases at the narrowing points and is greatest at the narrowest point with the radius R 5 . The greatest loads on the pipe also occur here.

To produce other desired changes in shape accordingly Reduced pipes or hoses can also be used accordingly Use shaped templates in which the pipe parts are laid and attached then be warmed until this is due to the shape of the stencils have adopted the specified configuration. It can be used exactly Generate repeatable shape changes, so that a mass production of preformed pipe pieces or the like with more exact Compliance with specified sizes is easily possible.

Another area of application is in the production of Find connections with fittings and pipe connections so that if applicable Sealing rings are not required.  

To do this, it is sufficient to use slightly reduced hoses, which are heated accordingly at their connection points, so that there a predetermined adjustment can be achieved by the heat treatment can.

The method can also be used for the production of pipe systems, which are equipped in the form of double tubes with gas insulation chambers, preferably air chambers. Examples of this embodiment are shown in FIGS. 3 and 4.

As can be seen from FIG. 3, extensions 7 are provided at predetermined intervals around the circumference of a tube 6 , which in the assembled state are designed as supports and seals within an outer tube 8 .

In this way, successive expansions arise Gas chambers with excellent insulation.

To further increase the insulation or the insulating effect can the reduction in these use cases amount to more than 20%.

In a similar way, indentations 9 of an outer tube 10 can also be produced around their circumference at predetermined intervals, which recesses are designed as supports and seals for an inner tube 11 in the assembled state.

Such an embodiment is shown in FIG. 4.

The respective undeformed tube can be made of plastic or metal consist.

FIGS. 5a-e show a T-connector, consisting of a hose connection 16 which is guided with its mold 17 through a bore 15 of the tubular portion 13.

With the help of a pressure piece 18 and screw elements, not shown, the hose connection 16 is clamped to the tube section 13 to form a T-connection. The hose connector 16 is therefore provided with a thread so that the pressure piece is clamped against the pipe section 13 , the piece 17 located in the pipe section 13 allowing the clamping. The T-connection is produced by heating the corresponding pipe section so that this heated part changes into its original shape. The bore 15 is then produced, in a size that corresponds to the diameter of the hose connection 16 . The hose connection 16 is integrally connected to the fitting 17 , which is guided with its oval shape through the bore 15 of the still in its warm outline, the pipe section 13 fully adapting to the fitting 17 when it cools. After cooling the surroundings of the borehole, the pressure piece 18 is guided over the hose connection 16 and clamped with the aid of screwing elements, so that a firm and tight T-connection is created. The shaping of the pipe section 13 can be carried out in such a way that there is no or only a slight flow resistance in the pipe section 13 .

A particular advantage of this method is that a T-connection can also be made with lines that have already been laid, without having to be dismantled. The hose connection 16 is preferably made of metal, as is the pressure piece 18 and the screwing elements, not shown.

Claims (1)

A method of manufacturing a tubular article, wherein a Thermoplastic in the form of a powder or granulate with the addition of chemical cross-linking agents as well as additives and auxiliaries in one Pressure chamber is subjected to a high pressure, reducing the temperature the mixture rises to about 110 ° C, whereupon the mixture through channels performed an extrusion device and still within the strand Pressing device is heated to cross-linking temperature, the extru dated hollow strand in the same work process continuously by Forming tool is pulled, with a stretching of the hollow body around more than 10% - preferably 20% - is done, and in the stretched Mold is cooled and fixed, the hollow strand thus obtained to length cut and partially heated above the crystallite melting point is what the heated place to make a permanent Pipe bend or pipe kink on those fixed in the extrusion press put form striving back.