Patent Application
20170113401
This application claims the benefit and priority of EP Application No. 15 191 594.9, filed Oct. 27, 2015. The entire disclosure of the above application is incorporated herein by reference.
Technical Field
Electric welding coupler for the welding of pipes made of thermoplastic material or other weldable plastics comprising a cylindrical body made of thermoplastic material or other weldable plastics, containing at least one welding element; wherein the welding element is arranged close to the inner diameter of the cylindrical body, wherein the welding element forms at least two weld zones, a contact for feeding the electric current and at least one cavity, wherein the cavity is arranged in the cylindrical body.
Discussion
Mainly in recent years, for weight and corrosion reasons, pipelines made of thermoplastic materials have been increasingly used in pipeline constructions, more specifically for the construction of pipeline networks for gas and water supplies, as well as for the conveyance of air, waste water, or else chemicals. The pipelines used are generally made of pressure-resistant plastic. For reasons of quality and efficiency, electric welding couplers are often used to connect such pipelines. The greater the pipe diameter of the pipelines to be connected, the more effort is required to connect the individual pipeline components. Since, in the case of large pipe cross sections, the gap between pipeline and Electric welding coupler is relatively large, the preconditions for optimal welding are hardly given. In the case of narrow production tolerances, in which a small gap formation between pipe outer diameter and coupler inner diameter is achieved, the problem of introducing the pipe into the Electric welding coupler exists. The greater is the diameter of the pipeline, the more are the pipes inclined to ovality and are hence unable to be introduced into the coupler. Apart from the gap and the ovality of the pipes, there is the further problem of cavitation in the welding zone. In the welding of electric welding couplers, more specifically in the case of large diameters, blowholes arise in the welding zone following cooling, which blowholes can in some circumstances adversely affect the strength of the weld joint. Blowholes are formed by the volume shrinkage of the melt during hardening of the plastic, or else by the irregular expansion of the melt, in that boundary points first connect to the pipe to be welded and the trapped air there between hence no longer has a chance to escape.
Electric welding couplers which try to eliminate the problem of cavitation by applying a high pressure to the weld are known from the prior art.
WO 2010 064 832 discloses a fusion-type connection member for the welding of pipes. The connection member containing a hollow part on the inner circumference of the body into which air is introduced during the welding process. This increases the pressure of the electrothermal wire and reduces the annular gap between the inner circumference of the connection member and the outer circumference of the pipes to be joined.
The drawback of this connection member is that, it is easier for the outer circumference to expand than to bring a high pressure on the inner circumference, therefore the pressure on the electrothermal wire respectively on the warmed plastic is not very high.
The object of the invention is to propose an electric welding coupler which brings an additional pressure on the heating element respectively on the inner circumference of the inner ring and a reducing of the annular gap between the inner diameter of the coupler and the outer diameter of the pipe ends for the welding process to achieve a good welding without blowholes and an optimal strength of the welded joint.
The object is achieved according to the invention by the arrangement of a reinforcing ring around the outer circumference respectively outer diameter of the cylindrical body.
The reinforcing ring forms a rigid cover around the cylindrical body which makes it impossible for the cylindrical body to expand on the outer circumference respectively outer diameter. On this ground acts the pressure on the welding element, respectively on the inner ring of the cylindrical body, wherein the pressure is generated by the liquid in the cavity and will pour in the cavity through the pressure connection before the welding process starts. The preferred liquid pressure in the cavity is at least the dual nominal pressure of the appropriate pipe.
Due to the reducing of the inner diameter respectively the inner circumference of the inner ring contacts the inner ring the pipe ends and eliminates the annular gap. The elimination of the gap brings the advantage of a small amount of melt which is needed for a good welding joint. This small amount of melt has the benefit of a shorter heating time which is needed and due to the small amount of melt it generates less shrinkage during the cooling and solidification of the melt that reduces the shrinking in the welded joint. Because of such a small amount of melt is it possible to reduce the middle cold zone between the two welding zones, wherein the middle cold zone can be half as wide as standardized according to EN ISO 15494:2003 depending on the pipe diameter, wherein the strength of the welded joint is guaranteed. In a smaller cold zone will be stored less eddy water and the flowing through liquid has a smaller area directly on the inner ring of the coupler which is stressed by the liquid.
The arranged reinforcing ring can be also used as carrying aid. Such coupler will be used at large diameters mostly, that means they are very heavy. Due to the reinforcing ring is it possible to fasten the whole electrical welding coupler with the reinforcing ring on a crane and bring them on the right place.
In a preferred embodiment is it possible to remove the reinforcing ring after the montage of the inventive electrical welding coupler and reinstalled on a next electro welding coupler with the same size for the next welding.
The inventive electric welding coupler comprising a cylindrical body made of thermoplastic material or other weldable plastics. The cylindrical body is preferably formed by an outer ring and an inner ring, wherein the inner ring is concentrically arranged to the outer ring. A cavity is formed by the outer circumference of inner ring and the inner circumference of the outer ring, preferably by a recess in the outer circumference of inner ring or in the inner circumference of the outer ring. On both sides of the inner and outer ring are side rings arranged, preferably are the inner, outer and side rings welded and form the cavity between. The cavity extends around the entire circumference between the inner and outer ring.
Before the welding process the cavity will fill up with a liquid, preferably with water. As an alternative embodiment the liquid can also include a chemical reactive system which is able to support the welding process by generation of pressurized gases and heat or by expansion to foam. A further embodiment would be also a liquid which can consist of a resin which supports the mechanical stability of the coupler after curing.
The pressure on the inner ring will be generated by the liquid. The liquid pressure is at least twice of the nominal pressure of the appropriate pipe. The wall thickness of the inner ring is preferably in the middle thicker than at the ends because the pressure acts in the middle respectively in the region of the welding elements and this brings a higher stability of the inner ring where the pressure acts.
The reinforce ring, which hinders an expansion of the outer ring of the ring body, is made of a high strength material, preferably material with at least a modulus of elasticity of 50 GPa, especially preferred composite materials or metals. Steel is also a preferred material for the reinforcing ring. But also other materials which make the ring stable and stiff are possible.
The reinforcing ring is preferably formed by at least two parts preferably two half shells which will brace together. In this preferred embodiment is it possible to remove the reinforcing ring after the installation of the inventive electrical welding coupler and it's possible to reinstall the reinforcing ring on a next electrical welding coupler with the same size for the next welding. Also a chain would be possible as a reinforcing ring because a chain is formed by more than two parts.
Another embodiment of the invention has an integrated reinforcing ring at the electric welding coupler which is not removable and the reinforcing ring is preferably made in one piece.
The inventive electrical welding coupler has at least one welding element which is preferably arranged in the central region on the inner ring of the cylindrical body close to the inner circumference respectively inner diameter of the inner ring and forms at least two welding zones. Preferably are there two weld zones for the welding of each pipe end, naturally there can also be more than two of them. Preferably the welding element or the welding elements, if there are separate elements which are not connected, are formed by heating wire windings, wherein other welding elements like conductive plastic are also possible. It is important that due to the high deformation respectively compression of the inner ring the welding element is flexible.
It has been shown that it is advantageous if the heating wire windings are arranged wavy preferably sinusoidal and the inner ring can be better deformed as a result. As a result of the wavy course, the heating wire windings can be elastically deformed and the inner ring can be compressed as a result and pressed against the pipe ends.
Alternatively thereto, the option exists that the heating wire windings are meander-formed arranged, that brings also the benefit of a flexible heating element.
The illustrative embodiment of the invention is described with reference to the figure, though the invention is not just limited to the illustrative embodiment, wherein:
The feeding of the electric current to the welding element (3) which forms the welding zones (15) will achieve through a contact (13), how it is state of the art. The welding element (3) can be formed through on element which is connected in the middle and forms two welding zones (15) or it is also possibly that the coupler (1) has at least two separate welding elements (3) which have separate contacts (3) for the electric current.
Preferably is the welding element (3) formed by heating wire windings but also other heating elements are possible. Because of deformation of the inner ring (8) is it important that the welding element (3) is flexible. To achieve this effect in a heating wire winding is it to favor if the heating wire winding is wavy arranged preferably sinusoidal. The heating wire winding can be arranged meander-form alternatively.
The effect of the reducing of the inner circumference respectively diameter through the fill up of the cavity (5) will achieve by the restriction of the expansion of the outer circumference (7) respectively diameter of the cylindrical body (2). To achieve this effect is a reinforcing ring (6) arranged on the outer circumference of the cylindrical body (2).
In a preferred embodiment is the reinforcing ring (6) formed by at least two parts preferably two half shells, which will brace together. This embodiment as shown in
| Number | Date | Country | Kind |
|---|---|---|---|
| 15 191 594.9 | Oct 2015 | EP | regional |
