CH683026A5 - Welded coupling sleeve for crosslinked polyethylene@ pipe - has non-crosslinked polyethylene@ inner layer and outer reinforcement - Google Patents

Abstract

The welded coupling sleeve for plastics pipes of cross linked polyethylene has an inner layer of non-cross linked polyethylene over at least part of its length. The sleeve has a reinforcement to increase its mechanical strength at the pipe joint. Pref. the coupling has two concentric sleeves (4,5), where the inner sleeve (4) is of non-crosslinked polyethylene, and the outer sleeve (5) is of a cross linked polyethylene. The inner sleeve (4) is divided with their facing ends bent downwards to grip the central ring beading (7) of the outer sleeve (5) between them. The outer sleeve is of a plastics with a higher mechanical resistance than the inner sleeve, or is of a metal such as chrome steel as a shrouding round the inner sleeve, with mating ribs and grooves between them to withstand longitudinal forces on the coupling. USE/ADVANTAGE - The coupling sleeve is for joining plastics pipes, especially in domestic drinking and hot water systems. The sleeve gives an effective sealed joint for the pipes with a long life it is resistant to heat and tension.

Description

1

CH 683 026 A5

2nd

description

It is known that plastic pipes due to their advantageous operating properties, such as corrosion and chemical resistance, easy to install, flexibility, durability, wear resistance, cold and warm bendability, have been very successful in recent years for domestic drinking water installations, heating water systems and other things were used. So far, the thermal welding process has been used successfully for connecting pipe sections, which is essentially available in two variants.

On the one hand, the so-called electro-welding sleeve is used, a hollow cylindrical sleeve made of non-cross-linked polyethylene with an electrical heating coil embedded in the connection area. When excited, this heating coil melts the surrounding material, which expands and, when it comes into contact with the pipe ends projecting into the sleeve, also causes it to melt on the surface. After the molten material has solidified, the two pipes are firmly connected to one another by the sleeve.

According to a further variant, heating element socket welding, the inner surface of one and the outer surface of the other pipe end is heated up to the melting temperature by brief contact with an appropriately shaped electrical heating element, whereupon the pipe ends only have to be pushed into one another against a pre-shaped stop.

It is also known to the person skilled in the art that pipes made of cross-linked polyethylene have hitherto been regarded as fundamentally not weldable with one another, so that the known welding methods are limited to pipes made of polybutene, polypropylene and uncross-linked polyethylene (PE). The disadvantages of these plastics, which were previously considered to be weldable, are also known: While the polybutene, due to the shrinkage and shape tolerances that are difficult to maintain, is difficult to process or complicated to manufacture with a tendency to crack, polypropylene, because of its low strength, requires extremely thick tube walls and is uncrosslinked polyethylene only suitable for cold water, polyvinyl chloride pipe connections are known to be glued and are reluctant to use them due to their environmental unfriendliness (e.g. the formation of hydrochloric acid during combustion).

This contrasts with the generally recognized advantageous properties of cross-linked polyethylene, in particular its high creep rupture strength, as well as aging and temperature resistance, the use of which has so far failed due to the prejudice of non-weldability.

It is also a fact known to experts that only plastics of the same type can be welded together. Since the so-called cross-linked polyethylene normally still contains approximately 30% non-cross-linked material, attempts have already been made to connect pipes made from such a plastic by means of a welding sleeve made from uncross-linked plastic. Although this leads to a welded connection due to the non-cross-linked material content of the pipes, this must not be exposed to large tensile and temperature loads due to the low fatigue strength of the inevitably uncross-linked socket material. The pipe system would therefore have an irresponsible weak point in the connection area, the mechanical strength and hot water resistance of which would lag far behind that of the pipes made of cross-linked polyethylene.

It is the object of the present invention to propose a welding sleeve for creating a welded joint on pipes made of cross-linked polyethylene, as described in the preamble of independent claim 1. Despite the use of uncrosslinked polyethylene, which is characterized by lower mechanical strength compared to the crosslinked version, the new welding socket should have a perfect seal with high pressure and tensile strength, so that the high creep rupture strength and temperature resistance known for crosslinked polyethylene pipes are now achieved also apply to the connection area.

This object is achieved by the combination of features defined in the characterizing part of independent patent claim 1.

An exemplary embodiment and several variants are described below with reference to the accompanying drawing. 1 to 5 of the accompanying drawings are sectional views of various embodiments of the subject matter of the invention.

Fig. 1 shows two pipes 1 and 2 made of cross-linked polyethylene, which for the sake of simplicity is referred to as VPE, while the uncross-linked polyethylene is to be referred to as PE. A welding sleeve, designated as a whole by 3, is constructed in two parts: an inner sleeve 4 made of PE is arranged between the circumferential surface of the two pipe ends and an outer sleeve 5 made of XLPE. The inner sleeve 4 provided with heating wires 6 is divided in its central region and the end sections of both sleeve parts are angled in such a way that they overlap the edge parts of the outer sleeve 5 on the one hand, and a central annular bead 7 which projects inwards from the outer sleeve 5.

The liquid-tight connection of the two pipes 1 and 2 can be achieved by pushing the welding sleeve over the pipe ends and heating it. The melting material of the inner sleeve 4 expands and connects to the neighboring parts of the outer sleeve 5 and the pipe ends, which are also heated by contact.

The total axial length of the welding socket can be adapted to the expected longitudinal stresses of the pipe system.

2, a likewise two-part welding sleeve 7 is pushed over the XLPE pipes 1 and 2. This consists of an inner sleeve 8 made of polyethylene with embedded heating wire 8a and a sheathing 9 surrounding the same on all sides

5

10th

15

20th

25th

30th

35

40

45

50

55

60

65

2nd

3rd

CH 683 026 A5

4th

a mechanically loadable plastic (e.g. POM) or metal (e.g. chrome steel). Depending on the material, the inner sleeve 8 can be extrusion-coated or the polyethylene that forms the inner sleeve 8 can be injected into the outer sleeve 9. The circumferential ribs 10 or annular grooves 11 formed on the outer surface of the inner sleeve 8 also enable the transmission of considerable compressive and tensile forces in the longitudinal direction.

The variant shown in FIG. 3 shows a one-piece welding sleeve 12 made of polyethylene that spans both XLPE tubes 1 and 2 and in which a reinforcing mesh 13 made of steel wire is embedded. Instead of the latter, for example, a perforated steel tube could also be embedded. The heating wire is omitted here, since the system is also suitable for socket welding, in which the inside and outside of the pipe surfaces are heated using a heating tool.

The embodiment shown in FIG. 4 also shows a one-piece welding sleeve made of polyethylene. However, the cross-linking of this material decreases from the outside area A to the inside, so that the inside area I of the welding sleeve 14 to be welded with the XLPE pipes 1 and 2 no longer has any cross-linking. In this way, too, the desired goal is achieved of obtaining a weldable butt weldable but nevertheless mechanically and thermally stressable, wherein the networked outer area A of the welded sleeve serves as reinforcement and the tensile and compressive forces that occur are transmitted through this outer area.

The variant according to FIG. 5 shows a welding sleeve 15 made of XLPE with two molded-in cavities 16 and 17, which are T-shaped in cross section and accordingly each have an annular welding section V and a radial channel K. After the welding sleeve has been placed on the XLPE pipes 1 and 2, polyethylene is injected into the cavities 16 and 17 via the channels K under pressure. The liquid material is intended to melt and weld the sleeve surface delimiting the cavities 16 and 17 and the pipes.

Claims (12)

Claims 1.Welding sleeve for the inseparable connection of two pipes made of cross-linked polyethylene, the same having an inside diameter which is equal to or larger than the outside diameter of the pipe ends to be connected and with regard to the intended welding, at least on the inside to be welded, and at least over a portion of its total length, has a layer of uncrosslinked polyethylene, characterized in that it is provided with a reinforcement which takes over the mechanical stresses occurring in the socket area. 2. Welding sleeve according to claim 1, characterized in that it consists of two concentric sleeves (4, 5), the inner (4) of which is made of uncrosslinked polyethylene (Fig. 1 and 2). 3. Welding sleeve according to claim 2, characterized in that the outer (5) of the two concentric sleeves (4, 5) consists of cross-linked polyethylene (Fig. 1). 4. welding sleeve according to claim 3, characterized in that the inner (4) of the two concentric sleeves is divided and the two parts with their angled end portions both the edge parts and an inwardly projecting central annular bead (7) of the outer sleeve (5) reach around (Fig. 1). 5. Welding sleeve according to claim 2, characterized in that the outer sleeve (9) made of a mechanically stronger plastic than the inner sleeve (8) or a corresponding metal, e.g. Chrome steel, and overlaps the inner sleeve (8) in the form of a casing (Fig. 2). 6. Welding sleeve according to claim 5, characterized in that in the connection area between the inner (8) and the outer sleeve (9) peripheral ribs or grooves (10, 11) are formed for better transmission of occurring longitudinal forces (Fig. 2). 7. welding sleeve according to claim 1, characterized in that the same (12) made in one piece from non-cross-linked polyethylene and is provided with a reinforcing mesh (13) embedded in the same or a perforated metal tube (FIG. 3). 8. Welding sleeve according to claim 1, characterized in that the same (14) is made in one piece from polyethylene, the cross-linking of which decreases from the outside (A) of the welding sleeve to the inside, so that the sleeve material (I) facing the pipe ends to be connected no longer cross-links has (Fig. 4). 9. welding sleeve according to claim 1, characterized in that it has in its base made of cross-linked polyethylene cavities (16, 17) which expand on the inside of the welding sleeve (15) and with outwardly directed channels (K) for injection liquid , uncrosslinked polyethylene are provided (Fig. 5). 10. Welding sleeve according to one of claims 1 to 9, characterized in that an electrical heating coil is embedded in the part thereof consisting of uncrosslinked polyethylene. 11. Welding sleeve according to claim 7, characterized in that the reinforcing mesh or metal tube serves as an electrical heating element. 12. Use of the welding sleeve according to claim 7 for welding pipes made of cross-linked polyethylene, characterized in that a heater that can be pushed onto the welding sleeve is used for heating the reinforcing mesh or the perforated metal pipe. 5 10th 15 20th 25th 30th 35 40 45 50 55 60 65 3rd