MC1468A1 - ELECTROSOLDABLE BYPASS SOCKET FOR PLASTIC PIPES - Google Patents

Description

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1580 -83-1468

No. 1 10 Has 16 4o,g

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PATENT FOR INVENTION

Title: ELECTROSOLED BRANCH FITTING FOR PLASTIC PIPES Applicant: INNOVATION TECHNIQUE S.A.M., abbreviated "INNOTEC"

The present invention relates to branch outlets fixed on fluid distribution pipes, such as gas, water, liquid or gaseous chemicals, when these pipes are made of thermoplastic material and, most often, polyethylene.

Such branch fittings are used on these pipelines to install a branch line, an operation that can be carried out on the pipeline while it is under pressure. They are generally made of the same plastic material as the pipeline and consist of a collar that fits around the main pipeline. A shaft extending from this collar contains the outlet pipe, onto which the branch pipeline is installed. This shaft also incorporates the necessary means for drilling through the main pipeline to pressurize the branch pipeline. The seal between the main pipeline and the shaft is achieved by welding a portion of the branch fitting collar to the main pipeline. This welding is accomplished using a heating element positioned on the inner surface of the collar and coaxial with the branch shaft. An electric current passes through this heating element during welding to heat the surfaces of the main pipeline and the collar to the melting and welding temperature.

No. 2

Modern branch connections always have a collar whose inner diameter matches the outer diameter of the pipe for which they are designed, with the collar encircling the entire pipe. For installation, this collar typically consists of two roughly semi-cylindrical half-collars that remain permanently attached to the pipe after installation.

Although it gives good results, this system becomes very expensive in practice when dealing with outlets or branches that are small in diameter compared to the main pipe; indeed:

- The outlets must go all the way around the main pipe, requiring a large volume of material compared to that required for the branch itself, and therefore a high cost price and weight.

- Furthermore, it is necessary to have a socket model for each main pipe diameter, reducing the possibilities of mass production, considerably increasing investment costs by increasing the number of plastic injection molds, increasing the stock of different parts at the user.

The present invention describes a branch connection in which the clamp is eliminated; the connection is welded to the main pipeline by a weld base proportioned to the branch being installed, rather than to the main pipeline. This weld base is clamped onto the main pipeline for welding by a clamp adapted to the branch connection, but removable and reusable as many times as required. Furthermore, the weld base is flexible enough to adapt to pipelines of different diameters; in this way, several branch connection models have been replaced by a single model, facilitating mass production, reducing specific investments, and also simplifying inspection.

No. 3

and the reduction of the user's inventory.

The invention will be better understood from the following description, given by way of example, and whose understanding is facilitated by the accompanying drawings, where:

Figure 1 represents a branch connection according to the invention, placed on a pipe, cut along the plane perpendicular to the axis of the pipe.

Figure 2 is the same connection socket seen from above. Figure 3 is a connection socket like Figure 1, but with a clamp according to another version. Figure 4 is the connection socket of Figure 3, seen from above.

In all these figures, the removable clamps used for the implementation of the branch sockets, according to the invention, have also been schematically represented.

The branch fitting 1, shown in figures 1 and 2, with its clamp, is ready to be welded onto the main pipeline 2. It consists of a shaft 3, a welding base 4, an outlet tube 5 for receiving the branch pipeline, and a drill 6 which screws into the shaft 3 and can, by tightening, cut a circular core in the section 7 of the main pipeline 2, in order to pressurize the branch. A cap 8 screws onto the top of the shaft 3 to close the fitting after it has been installed;

Pipe 2 is made of plastic, usually polyethylene, a flexible and deformable material that is also highly resistant to impact, corrosion, and pressure. The pipe's thickness is significant, approximately one-tenth of its diameter, to withstand internal pressure.

The branch connection 1 is made of the same material, so that the weld of the welding base 4 onto the pipe is homogeneous and

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This weld is solid. It is achieved using an electrical resistor 9 wound in a spiral within the welding plate 4 of the socket, around its hole 10. The resistor is positioned very close to the inner face of the welding plate. The ends of this resistor protrude at points 11 and 12, allowing them to be connected to an electrical voltage source. When the welding plate is pressed against the outer surface of the pipe 2, and an electric current is passed through the resistor 9, the resistor and the polyethylene surrounding it heat up and expand. This creates a fused volume of material around the resistor, this volume being formed partly by the inner part of the welding plate and partly by the outer part of the pipe. This volume is under pressure due to volumetric expansion, ensuring the interpenetration of the materials of the two parts, thus forming a weld. After the electrical current has been switched off and cooling, the welding base is welded onto the pipe, over the entire surface of 1 electrical resistance.

To ensure the mechanical strength of the assembly thus created, the welding surface must be proportional to the dimensions of the socket 3 and the outlet tube 5, which are directly linked, since the socket must ensure a passage approximately identical to that of the outlet tube 5. It is easy to understand that, when the branch fixed to the outlet tube 5 is of a much smaller diameter than that of the main pipe, a welding surface occupying only a small part of that of the main pipe 2 is sufficient, as shown in figures 1 and 2.

Furthermore, the thickness of the welding base is proportional to that

No. 5

of the other parts of the bypass which, being of much smaller diameters than that of pipe 2, are of much smaller thickness for the same resistance to internal pressure.

The thickness of the welding base is therefore much less than that of the main pipeline 2.

It follows, as can be seen in Figure 1 in particular, that the thickness of the weld base is very small compared to its radius of curvature, which is also the radius of the main pipe 2.

The branch fitting 1 is injection molded from the same plastic material as the pipe 2, which in this example is polyethylene. The weld flange is shaped like a portion of a cylinder, with a radius of curvature identical to that of the main pipe 2.

For welding branch fitting 1 onto pipe 2, it is necessary that the internal surface of its welding base 4 be kept in contact with the facing surface of pipe 2. For this purpose, a removable clamp is used, pressing the welding base onto the pipe by going around it. We have represented such a clamping collar in figures 1 and 2. It consists of 2 flexible straps 13 and 14, passing over the welding base 4 on either side of the central barrel 3, and whose ends 15 are fixed on 2 rigid pieces 16 and 17 which meet under the pipe, and which have a clamping means consisting of a screw 18 fixed to the piece 15, and a nut 19 which can be screwed manually onto the screw 18, and which drives the rigid piece 17 to obtain the tightening of the straps 13 and 14 by bringing the pieces 16 and 17 together.

With its welding base 4 held against the pipe, the branch fitting can be welded onto it. After welding and cooling, the removable clamp can be removed.

unscrewing nut 19.

The welding base 4 has a small thickness compared to its radius

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of curvature. In addition, the polyethylene used is a material flexible enough to accept slight permanent deformations without loss of its mechanical strength.

Therefore, the branch connection 1 shown can be used for welding onto pipes whose radius differs from the initial radius of curvature of its weld flange. Figure 1 shows, in dashed lines, a pipe 20 with a radius 0.66 times that of pipe 2, and a pipe 21 with a radius 1.5 times that of pipe 2. Provided that the flange clamp is properly fitted, the weld flange 4 can be sufficiently deformed so that,

When it is clamped onto pipe 20, for example, its inner surface comes into contact with the outer surface of that pipe. The same is true for a larger pipe, such as pipe 21.

To accommodate these different pipe types, each of the straps 13 and 14 of the hose clamp has a length adjustment device. These devices are visible in Figures 1 and 2, at points 22 and 23.

It should be noted that the forced deformation of the weld base 4, on the pipes 20 or 21, induces internal stresses in this weld base; but these stresses largely disappear during the heating of the material during welding; in any case, the material used can very well accept such stresses, since, for example, the pipes made of this material have the property of being able to be wound onto reels for storage, then unwound and straightened for installation.

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It is clear that the hose clamp of the bypass socket on the

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The piping may be different from the collar described above without, however, departing from the object of the invention.

Thus, a variant of this hose clamp is shown in figures 3 and 4.

The welding flange 26 of the branch connection 27, which contains the resistance wire 28, is fixed to the pipe 38 by a clamp 29 which, instead of passing over the welding flange as in Figure 1, hooks into recesses provided for this purpose on the welding flange. The recesses 30 and 31 are formed by molding onto the reinforced edges 32 and 33 of the welding flange 26.

Rigid pieces 34 and 35, in the form of hooks, are placed in the housings 30 and 31. These pieces 34 and 35, constituting the ends of the clamping collar, are connected together by straps 36 and 37, flexible or rigid, which meet under the pipe 38 by means of a clamping device which may be identical to that already shown in figures 1 and 2, and not shown here.

This method also has the advantage of ensuring the weld flange is firmly pressed against the pipe, even if the pipe's outer radius differs from the initial inner radius of curvature of the weld flange. Therefore, the same branch fitting can be used for several pipes of different diameters.

It goes without saying that the present invention has been described above only for explanatory purposes and is in no way limiting, and that all useful variations may be made to it, without going out of its scope.

No. 8

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Claims (1)

DEMANDS 1°/ Electroweldable branch fitting made of plastic material, intended to be welded onto a main pipe made of the same material, comprising a welding base containing the electric heating resistance and welded onto the pipe, a shaft extending from the center of the welding base and carrying the outlet tube on which the branch pipe will be placed, characterized by the fact that this branch fitting does not go around the pipe, but only covers a part less than half a pipe diameter, this fitting being, moreover, held by a clamping device during its welding onto the main pipe. 2°/ Branch connection according to claim 1, wherein the welding base is flexible enough to be able to adapt to different pipe diameters. 3°/ Branch outlet according to claim 1, wherein the clamping device of the outlet on the main pipeline is removable. 4°/ Branch connection according to claims 1 and 3, wherein the clamping device consists of 2 or more flexible straps going around the main pipeline passing over the welding base, and comprising a clamping system for these flexible straps. 5°/ Branch connection according to the preceding claims, in which the flexible straps include a means of length adjustment, in order to be able to adapt to different diameters of main pipes. 6°/ Branch outlets according to claims 1 and 3, wherein the welding base comprises recesses or ridges, in which No. 9 Rigid hooks are attached, linked to flexible straps passing under the main pipe and incorporating a tightening system, in order to secure the branch connection to the pipe. 7°/ Branch connection according to claims 1, 2, 3, 6, wherein the flexible straps further comprise a means for adjusting in length, to adapt to different diameters of main pipes. (T'X.'tZ-^5 ^