SK21594A3 - Pipejoint and process for production of pipejoints made of polyolefin - Google Patents

Abstract

The end (13) of the pipe (12) from the polyolefin is expanded with the expanding mandrel in the cool, i. e. in the surrounding temperature. After removing of the expanding mandrel the expanded pipe end (13) and required junction part or end (11) of the other pipe (10) are thrusted one on another. The pipe end (13) from the polyolefin consequent to spontaneous re-shaping reversibly changed shape, creates solid and gasproof junction with the juncting part or with the end (11) of another pipe (10).

Description

PIPE COUPLINGS AND METHOD OF MANUFACTURING PIPE COUPLINGS FROM POLYOLEFIN

Technical field

BACKGROUND OF THE INVENTION The present invention relates to a method for manufacturing a pipe joint in which the pipe end of a polyolefin pipe is expanded and slid onto the connecting portion as well as the pipe joint thus produced.

BACKGROUND OF THE INVENTION

In a known analogous process, which is disclosed in DOS 38 17 442.1, such a pipe joint is produced, for example, by means of a clamping sleeve which bridges the connecting portions of both pipes. The clamping sleeve may consist, for example, of a thermoplastic material such as a crosslinked polyolefin. This sheath is joined to the end portions so that the crosslinked polyolefin, after being heated above the melting point of the crystallites, is deformable in the heated state and can be slid on the connecting portions after being expanded in this heated state. In the same way, the cross-linked polyolefin pipe end may be slid onto the connecting portion, for example a T-piece.

The practice of this process entails certain difficulties in practice, since the crosslinked polyolefin must be heated to a relatively high temperature, for example above 135 ° C in the case of the crosslinked polyolefin, and only at that temperature it has a sufficiently easy formability. Consequently, there is a need for the respective parts to be joined together in such a short time that during this time cooling still does not occur below the melting point of the crystallites.

SUMMARY OF THE INVENTION

SUMMARY OF THE INVENTION The object of the invention is to find a method for producing a pipe joint by the aforementioned method, such that the production of a secure pipe joint is carried out at normal temperature, i. j. at ambient temperature, as well as to provide a pipe joint that can be produced under ambient conditions to form a secure and tight joint.

According to the invention, this object is achieved by the fact that the end of a pipe whose inner diameter is smaller than the outer diameter of the connecting part is reversibly expanded at an ambient temperature by an expanding mandrel to an inner diameter which is larger than the outer diameter of the connecting part. After removal of the expanding mandrel, the still expanded pipe end is slid onto the connecting portion, whereby the pipe end is firmly and tightly connected to the connecting portion by self-reshaping the reversibly expanded pipe end.

With respect to the pipe connection, this object is achieved by the fact that it consists of a connection part and at the ambient temperature of the expanded pipe end at an ambient temperature of self-reshapable which is firmly and tightly connected to the end part of the connection part. is smaller than the outer diameter of the connector.

The invention is based on the surprising finding that polyofelins, in particular of medium density, high density or crosslinked polyofelins, have a sufficiently large, reversible formability even in the cold and partially crystalline state, i. in a heated state not exceeding the melting point of the crystallites. This means that the polyolefin is malleable by mechanical action, but in the formed state it seeks to achieve its original shape. If a sufficiently large force is used, for example by means of an expanding mandrel of the conventional type for expanding the pipes, the pipe ends of the polyolefin pipes can be reversibly expanded. Under the given ambient temperature conditions, spontaneous re-shaping to the original state occurs, i. to the original width of the pipe at a relatively low velocity so that the expanding mandrel can be removed from the expanded pipe and the still expanded pipe end slid onto the desired connecting portion. On the other hand, the rate of spontaneous reshaping to its original state is so great that there is no undesirable waiting time.

Compared to another material, polyolefins have the advantage that the extension, while remaining after joining the connection portion, does not cause stress cracking.

The process according to the invention offers a particularly advantageous possibility of joining polyolefin pipes, in particular medium density, high density polyolefin pipes, or crosslinked polyolefins, without the use of thermal energy with any desired connecting part. In this case, a gas-tight connection, in particular a gas-tight connection, is obtained by spontaneously converting the expanded pipe. During the molding, the polyolefin fits particularly rigid and tight to the end, in this case the self-resurfacing foil given the surface structure on the connecting part. Suitable surface structures for increasing the bond strength are, for example, reinforcements, notches, grooves or grooves with which the reshaped polyolefin comes into engagement.

In the context of the previously described method, it is possible, if necessary, to further secure the pipe connections made. Pipe clamps of known type can serve for this purpose. However, it is also possible to insert a clamping ring on the pipe end of the polyolefin pipe. This clamping ring can, if it is also made of a reversibly deformable material, slide from the beginning to the pipe end. However, it is also possible after insertion of the pipe joint to slide from the pipe side to the end of the pipe joint, for example by means of known hydraulic means, a non-deformable or low-deformable clamping ring made of metal, for example.

Overview of the figures in the drawing

Exemplary embodiments of pipe joints produced by the method of the invention are shown in the figures and are further explained and described in detail with reference numerals. 1 shows a cross-sectional view of the pipe joint from the connection portion and the pipe end inserted by the method according to the invention;

Figure 2 is a cross-sectional view of the pipe joint of Figure 1 with a clamping ring;

3 shows a cross-sectional view of a pipe joint according to the invention between two pipe ends.

DETAILED DESCRIPTION OF THE INVENTION

When viewed in section in Figure 1, it is possible to see the connecting part 1, which may be, for example, a straight pipe piece, elbow or other coupling piece for connecting two pipes, but also, for example, a triple coupling piece as a T-piece. This connecting part 1 is made of a material such as metal, glass, ceramic, plastic or some other material of choice for a given purpose. At each joining point, the connecting portion 1 is provided with a surface structure increasing the bonding strength. In the illustrated embodiment, this surface structure is formed by a thickened, end-to-end end portion 2. Instead, there may also be one or more thickenings, notches, grooves or grooves or the like.

The illustration in Figure 1 shows a polyolefin pipe 2, preferably a medium or high density crosslinked polyolefin. The inner diameter of the pipe 3 is smaller than the outer diameter of the connecting portion 1; may, as shown, have substantially the same diameter as the inner diameter of the connecting portion 1, thereby avoiding the formation of a flow resistance through the constrictions and deposits in the constrictions from the medium flowing through the connecting part 1 and the pipe 2. the pipe end 4 is widened at ambient temperature, for example by means of an expanding mandrel of conventional type, that the inner diameter of the pipe end 4 is at least as wide as the outer diameter of the connecting part 1 in the region of the reinforced end part 2. the end 6 spontaneously acquires the original shape with the original dimension. As a result, the pipe end 4, as shown, adheres to the outer profile of the connection part 1. Since the pipe end 4 initially had an inner diameter that was smaller than the outer diameter of the connection part 1, the pipe end 6 slips close to its length. The end part 2 of the connecting part 1 is thereby produced at the end of a very large, very tight connection between the pipe end 6 and the connecting part 1.

Figure 2 shows a further embodiment of the previously described pipe joint, the corresponding parts being provided with the same reference numerals. In this embodiment, the clamping ring 5 is used to additionally secure the made tight joint between the pipe end 6 and the connection part 1. This clamping ring 5 is preferably of the same material as the pipe 3. In the example shown, the pipe 3 and the clamping ring are made of crosslinked polyethylene. The inner diameter of the clamping ring 5 is tightly fitted to the outer diameter of the pipe 2 and is slid onto the pipe end 6 before making the pipe joint. In the following expansion procedure, the clamping ring 5 together with the pipe end 5 is pre-expanded so that the expanded pipe end 5 together with the clamping ring 5 is slid onto the end portion 2 of the connecting part 1. Subsequent spontaneous re-deformation leads thereafter between the pipe end 4 and the end part 2 of the connecting part 1, whereby the clamping ring 5 is also retracted and additionally compresses the pipe end in the region of the clamping ring 5 against the end part 2.

Figure 3 shows a pipe joint that is formed between two pipe ends. Both tubes may be of the same or different materials; preferably the pipes are made of crosslinked polyolefin and serve as a conduit for corrosive media. By way of example, industrial, but in particular also domestic or municipal waste water, which requires particularly corrosion-resistant pipe materials. Crosslinked polyolefin pipes have proved to be useful in practice.

In the illustrated embodiment, both tubes have the same outer and inner diameters. However, it does not matter that the same pipe joints can be produced in the present case also between pipes of different diameters, so long as the differences in the inner diameters so connected do not cause unacceptable flow and deposit resistances. The first pipe 10 has a first pipe end 11, the second pipe 12 has a second pipe end 13. It can be seen that the inner diameter of the second pipe end 13 is enlarged and that the expanded second pipe end 13 is slid onto the first pipe end 11 of the first pipe 10. This extension, for example, takes place with a suitable expansion mandrel at ambient temperature and subject to the described spontaneous re-deformation by means of which the expanded pipe end 13 tries to regain its previous state. The large-area, tight abutment between the two pipe ends 11 and 13 also forms a tight pipe connection here, which, due to the corrosion resistance of the material against the aforementioned waste water, will be tight even during long use.

As in Figure 2 illustrating an example of manufacture, the connection can additionally be secured by a clamping ring; however, care must be taken to ensure that no unacceptable change in the shape of the first pipe end 11 is present at the pressure of such a clamping ring, which constitutes a resistance to the flow of waste water flowing or gives rise to waste water deposits in the area of the joint. Instead of the clamping ring, a fastening means may also be used in the present case to additionally secure the joint.

Crosslinked polyolefin pipes are also used for this reason in the waste water technique, since in this way safe, self-sealing joints between smooth pipes can be easily produced. A further advantage is that pipes 10 and 11 made by a continuous process can be laid in one piece without the need for special elbows or other connecting parts so that the pipes can be laid in the desired position. It is therefore only necessary to make connections at the inlet and outlet points between the pipes.

Claims (15)

PATENT CLAIMS Method for producing a pipe joint, in which the pipe end of a polyolefin pipe is expanded and slid onto the connection part, characterized in that the end (4) of the pipe (3) whose inner diameter is smaller than the outside diameter of the connection part (1) at ambient temperature reversibly expands to an inner diameter that is larger than the outer diameter of the connecting portion (1) and that after the expansion mandrel has been removed, the expanded end (4) of the pipe (3) and the connecting portion (1) are pushed together wherein the connecting part (1) is connected firmly and tightly to the pipe end (4) as a result of the self-reshaping of the reversibly expanded pipe end (4). Method according to claim 1, characterized in that the end part (2) of the connecting part (1) is provided with a surface structure increasing the engagement surface with the pipe end (4). Method according to claim 1 or 2, characterized in that the joint is additionally secured by a pipe clamp. Method according to claim 1 or 2, characterized in that the joint is secured by a clamping ring (5). Method according to claim 4, characterized in that the clamping ring (5) consists of a material which can be expanded at ambient temperature and spontaneously re-deformable together with the pipe end (4) reversibly. Method according to claim 4, characterized in that the clamping ring is made of a material which is not deformable or of little shape and, after making the joint, is hydraulically pushed onto the pipe end surrounding the connection part. A pipe joint consisting of a connecting part (1) and at an ambient temperature of the expanded pipe end (4) of a pipe (3) at a self-reshaping ambient temperature which is firmly and tightly connected to an end portion (2) of the connecting part (1); wherein the pipe (3) has an inner diameter smaller than the outer diameter of the connecting portion (1). Pipe joint according to claim 7, characterized in that the end part (2) of the connecting part (1) is provided with a surface structure increasing the engagement surface with the pipe end (4). Pipe joint according to claim 7 or 8, characterized by a clamping ring (5) placed at the pipe end (4), made of a material which is expanded at its ambient temperature and can be deformed by itself. Pipe joint according to Claims 7 to 9, characterized in that the pipe (3) is of medium-density or high-density crosslinked polyolefin. A pipe joint from a first pipe end (11) of a first pipe (10) and at an ambient temperature of an expanded second pipe end (13) of a pipe (12) which is self-reshapable at ambient temperature and is rigidly and tightly connected to the first pipe end . Pipe joint according to claim 11, characterized in that the first pipe end (11) of the first pipe (10) is provided with a surface structure increasing the engagement surface with the second pipe end (13). Pipe joint according to claim 11 or 12, characterized in that the joint is secured by a clamping ring. Pipe joint according to claim 13, characterized in that the clamping ring is made of a material which is expandable and self-deformable at ambient temperature. Pipe joint according to one of Claims 11 to 14, characterized in that the first and second pipes (10, 12) are of medium density and high density or crosslinked polyolefin.