ELECTRIC WELDING FITTING

Description

[0001] The invention relates to an electro-welding fitting made of plastic for welding plastic pipelines according to the preamble of claim 1.

[0002] Such an electrofusion fitting is known from JP 2005 331051 A.

[0003] Primarily in recent years, the use of thermoplastic piping has increased in pipeline construction, mainly due to weight and corrosion resistance. This is especially true for the construction of pipeline networks for gas and water supply, as well as for conveying air, wastewater, or chemicals. The pipes used are usually made of pressure-resistant plastic. For efficiency reasons, electrofusion fittings are often used to join such pipelines. These fittings have a heating wire winding inside to weld the pipes to the fitting.

[0004] To ensure the pipe ends are inserted deeply enough into the electrofusion fitting during installation, the fitting has an internal stop. This stop allows the installer to verify that the pipe end has been inserted to the desired position. A disadvantage arises when such an electrofusion fitting is used as a slip-on fitting. This means the fitting is first pushed almost completely over one pipe end and then in the opposite direction over the other. To perform this type of installation, the stop must always be removed first. This is a time-consuming and often difficult process, as the fitting is prone to damage to its inner diameter.Manufacturing two different fittings, i.e., one with a stop and one without, is not economically justified because injection molding tools are expensive to purchase and maintain, especially since this would also have to be applied to different diameters.

[0005] GB 2137026A shows an electrofusion fitting with four fixed stops on the inner diameter of the fitting. This allows it to be determined during installation whether the pipe ends are inserted deep enough into the fitting.

[0006] The disadvantage here is that if the stops in the fitting have to be removed due to assembly as a slip-on fitting and the stable design of the stops, this is a complex process in which the inner surface of the casing may be damaged and wire may protrude.

[0007] The object of the invention is to propose an electro-welding fitting that can be reliably used for the different types of assembly without high additional effort.

[0008] CH 5533 / 68, DE 2 311 279, WO 2010 / 071589 A1, DE 10 2013 009 687 A1 and EP 0 919 761 A1 disclose alternative embodiments of an electrofusion fitting.

[0009] This problem is solved according to the invention with an electro-welding fitting according to claim 1.

[0010] The inventive electrofusion fitting made of plastic for welding plastic pipes has a cylindrical body. In addition to fittings with a constant diameter, reducing fittings are also included under the category of electrofusion fittings according to the invention. The body of the electrofusion fitting is preferably made of a thermoplastic material. The electrofusion fitting has a longitudinal axis, a heating wire winding, and contacts for supplying the electric current. The inventive electrofusion fitting has a pipe stop, which is arranged on the inner surface of the body. This serves to detect and limit the insertion depth of the pipe ends into the electrofusion fitting. The pipe stop is flexible or elastic.This means that when the pipe end is inserted along the longitudinal axis on one side of the body until it reaches the pipe stop, the pipe stop tilts to the other side due to the pressure exerted by the pipe end against it, until it rests against the inner surface of the body, thus ensuring a stable pipe stop. The elastic design of the pipe stop allows it to be attached to the inner surface of the body via a slight, unstable connection, enabling easy removal if necessary. Nevertheless, the pipe stop provides a stable stop for the pipe ends. Therefore, the stop must be both stable and easily removable.

[0011] It is advantageous if the pipe stop is elastically deformable along its longitudinal axis. This ensures easy attachment of the pipe stop to the inner surface while still forming a stable stop when the pipe stop is tilted into an end position.

[0012] It has proven advantageous if the pipe stop can be tilted until a rigid position is reached; preferably, the rigid position is formed by the inner surface.

[0013] Preferably, the pipe stop extends at least along a portion of the circumference of the inner surface. The pipe stop preferably extends along the inner circumference of the electrical fitting or body over at least a defined arc, thus not extending over the entire inner circumference. The pipe stop ensures that the pipe end is inserted only as far as the pipe stop.

[0014] The pipe stop has at least one recess along its circumference on the inner surface. This ensures that the heating wire can be plowed into the body in a single operation. The heating wire is plowed into a heating zone on one side of the electrofusion fitting with several turns, and the same process is repeated on the other side. To allow both heating zones to be plowed in with the same heating wire in one operation, the pipe stop has a recess along its circumference on the inner surface. This recess allows the heating wire to be guided to the other side of the fitting by plowing, where the second heating zone is created.

[0015] A preferred design has proven to be one in which the pipe stop is positioned in the center of the body, along the longitudinal axis. This allows both pipe ends to be inserted to the center. Of course, asymmetrical bodies are also conceivable.

[0016] It has proven advantageous to arrange the pipe stop on an electrofusion fitting designed as a reducing fitting, with the pipe stop positioned at the end of the heating zone of the smaller inner diameter of the reducing fitting. This means the pipe stop lies between the two heating zones of the different inner diameters and is located at the end of the heating zone of the smaller inner diameter. This also allows for a stop to be provided for the smaller pipe end inserted from one side.

[0017] The pipe stop has a base and a head; in the cross-section of the pipe stop, the head and base are clearly visible. The cross-section showing the head and base of the pipe stop then extends along its length.

[0018] The base is positioned on the inner surface of the body and is narrower along its longitudinal axis than the head. The pipe stop and the body are formed as a single piece and are produced in the same injection molding process; the pipe stop is directly molded onto the inner surface. Preferably, the cross-section of the pipe stop extends consistently along a portion of the circumference of the inner surface. Because the base is designed as a narrow rib, the pipe stop can be easily removed, allowing the electrofusion fitting to also be used as a slip-on fitting. The more robust head ensures that the pipe end rests against the pipe stop as soon as the pipe stop is tilted towards the inner surface of the electrofusion fitting or body.

[0019] It is advantageous if a predetermined breaking point is arranged at the base of the pipe stop, the predetermined breaking point preferably being located at both the beginning and end of the pipe stop, which extends at least along a portion of the circumference of the inner surface. The predetermined breaking point facilitates even easier removal of the pipe stop by providing a cross-sectional reduction of the base at both the beginning and end of its length, this reduction extending only over a short section of the pipe stop's length.

[0020] The width of the head tapers towards the base. This gives the stop the necessary elasticity while still ensuring a stable stop.

[0021] It has proven advantageous if the tapering at the head is formed by an angle between the foot and the head, wherein the angle α is preferably > 90°.

[0022] This ensures that the pipe stop can tilt towards the inner surface of the casing and rest against it, thus forming a stop for the inserted pipe ends.

[0023] It has proven advantageous to have the angle bracket on both sides of the head. This eliminates the need to consider which side the first pipe end is inserted from during pipe end assembly.

[0024] Preferably, the heating wire winding has two heating zones, each with several turns, and the two heating zones are connected to each other. Both heating zones are arranged to the right and left of the pipe stop, respectively. To allow one heating wire to be used for both heating zones and to enable the wire to be plowed in a single step, the plowed-in wire runs between the two heating zones in the area of ​​the pipe stop recess or crosses the center of the fittings in the area of ​​the recess.

[0025] An embodiment of the invention is described with reference to the figures, although the invention is not limited to this embodiment. The figures show: Fig. 1 a three-dimensional view of an electro-welding fitting according to the invention, Fig. 2 a longitudinal section through an electrofusion fitting according to the invention, Fig. 3 a sectional view through a pipe stop Fig. 4 two longitudinal sections with the pipe end inserted, Fig. 5 a longitudinal section through an electrofusion fitting in which the course of the heating wire is shown and Fig. 6 Various forms of tolerance bridging between pipe end and electrofusion fitting.

[0026] The in Fig. 1The drawing shows a three-dimensional view of an electrofusion fitting 1 according to the invention. The electrofusion fitting 1 has a body 2, which is preferably made of a weldable plastic. The body 2 has a cylindrical shape extending about a longitudinal axis 3, whereby in a reducing fitting the cylindrical shape may be stepped. A heating wire winding for heating the plastic and welding the body 2 to the inserted pipe ends 14 is arranged in the body 2, as can be seen in Fig. 4A pipe stop 6 is arranged on the inner surface 7 of the electrofusion fitting 1 according to the invention. This stop ensures that the pipe ends 14 are inserted up to the pipe stop 6 in order to achieve a good weld over the maximum surface area. Since the electrofusion fitting 1 according to the invention is also intended to be used as a slip-on fitting, the pipe stop 6 must be easily removable without causing damage to the inner surface 7. This is achieved by making the pipe stop 6 flexible and elastic. This allows the pipe stop 6 to be easily removed without leaving hard, rigid residue on the inner surface 7 or requiring the use of a tool to remove it, which could damage the inner surface 7.

[0027] In Fig. 1It is also clearly visible that a recess 8 is present in the pipe stop 6 running along the inner circumference. This allows the heating wire 13 to be driven continuously into the body 2. That is, the driving of the heating wire 13 to form the first heating zone 12 can begin at one end of the body 2. In the middle, the heating wire 13 passes through the recess 8 by driving its way in, and the second heating zone 12 can be driven in on the opposite side of the first heating zone 12. This is well in Fig. 5 The diagram shows the path of the heating wire 13, although the heating wire itself is not visible since it is embedded in the plastic material of the fitting and its path is only shown schematically. This allows the heating wire winding 4, which is formed from a continuous wire 13, to be embedded in the electrofusion fitting 1 according to the invention in a single step. Fig. 2The two heating zones are clearly shown in section 12. It is advantageous if the pipe stop 6 is as shown in the diagram. Fig. 3 The pipe stop 6 is shown to have a cross-section 9, comprising a foot 10 and a head 11. The foot 10 is located on the inner surface 7 of the body 2. The body 2 and the pipe stop 6 are formed as a single injection-molded part, and the contacts 5 are also integrated within this part. The foot 10 has a narrower width in the direction of the longitudinal axis 3 than the head 11 of the pipe stop 6. This ensures that the pipe stop is flexible and elastic, allowing it to be easily removed from the inner surface 7 while also forming a fixed stop 6. Fig. 4Figure 1 shows an inserted pipe end 14 and the function of the pipe stop 6. The pipe end 14 is inserted, as shown in the upper figure, up to the pipe stop 6 and then a little further until the pipe stop 6 has inclined, as shown in the lower figure, so that the stop 6 or the head 11 rests firmly against the inner surface 7 and thus forms a fixed stop 6 for the insertion depth of the pipes.

[0028] Preferably, the cross-section 9 has an angle α between the head 11 and the base 10, ensuring optimal contact of the pipe stop 6 and forming a stable stop 6. Preferably, the angle is greater than 90°.

[0029] The illustrations in the Fig. 6Figure 1 shows possible embodiments for bridging the gap 15 that forms between the inserted pipe ends 14 and an electrofusion fitting 1 due to tolerances. The figure on the left shows the electrofusion fitting 1 without the pipe end inserted, and the figure on the right shows it with the pipe end inserted. The upper variant A shows one or more grooves 16 arranged sequentially around the end face. At the level of the grooves 16, opposite each other, knob-like protrusions 17 are formed on the inner surface. When the pipe end 14 is inserted, its outer diameter presses against the protrusions 17. The grooves 16 allow the protrusions to elastically accommodate the diameter or be pressed outwards, thus enabling the pipe end 14 to be inserted into the electrofusion fitting 1 and also securing it slightly.

[0030] Alternatively, as shown in Figures B below, a type of lip 18 is arranged on the end face of the electrofusion fitting 1. This is also intended to bridge the gap 15 between the pipe outer diameter and the fitting inner diameter. Reference symbol list

[0031] 1 Electrofusion fitting 2 Body 3 Longitudinal axis 4 Heating wire winding 5 Contact Power supply 6 Pipe stop 7 Inner surface 8 Recess 9 Pipe stop cross-section 10 Foot 11 Head 12 Heating zone 13 Heating wire 14 Pipe end 15 Gap 16 Groove 17 Knob 18 Lip

Claims

1. Electroweld fitting (1) made of plastic for welding plastic pipelines, containing a cylindrical body (2), a longitudinal axis (3), a heating wire winding (4), contacts (5) for supplying the electric current and a pipe stop (6), wherein the pipe stop (6) is arranged on the inner lateral surface (7) of the body (2), wherein the pipe stop (6) is designed to be flexible and resilient, wherein the cylindrical body (2) and the pipe stop (6) arranged thereon are produced in one piece in the same injection moulding method, wherein the cross section (9) of the pipe stop has a foot (10) and a head (11), wherein the foot (10) is arranged on the inner lateral surface (7) of the body (2) and has a narrower width in the direction of the longitudinal axis (3) than the head (11), wherein the width of the head (11) tapers in the direction of the foot (10), wherein the pipe stop (6) has at least one slot (8) along its course on the circumference of the inner lateral surface (7), characterized in that the heating wire winding is incorporated by embedding a wire in the inner lateral surface of the cylindrical body (2), wherein the embedded wire crosses through the centre of the fitting in the direction of the longitudinal axis in the region of the slot.

2. Electroweld fitting (1) according to Claim 1, characterized in that the pipe stop (6) is resiliently deformable in the direction of the longitudinal axis (3).

3. Electroweld fitting (1) according to either of Claims 1 and 2, characterized in that the pipe stop (6) can be tilted until a rigid position is achieved, the rigid position is preferably established as a result of the inner lateral surface (7).

4. Electroweld fitting (1) according to one of Claims 1 to 3, characterized in that the pipe stop (6) extends at least along a region of the circumference of the inner lateral surface (7).

5. Electroweld fitting (1) according to one of Claims 1 to 4, characterized in that the pipe stop (6) is arranged in the centre of the body (2) in the direction of the longitudinal axis (3).

6. Electroweld fitting according to one of Claims 1 to 5, characterized in that the pipe stop (6) on an electroweld fitting (1) which is designed as a reduction fitting is arranged at the end of the heating zone (12) of the narrower or smaller inner diameter of the reduction fitting.

7. Electroweld fitting (1) according to one of Claims 1 to 6, characterized in that the cross section (9) of the pipe stop (6) extends in a constant manner over the course along the circumference of the inner lateral surface (7) over a sub-region of the circumference.

8. Electroweld fitting (1) according to Claim 7, characterized in that a predetermined breaking point is arranged at the foot (10) of the pipe stop (6), wherein the predetermined breaking point is preferably arranged in each case at the end and at the start of the pipe stop (6).

9. Electroweld fitting (1) according to Claim 8, characterized in that the taper at the head (10) is formed by an angle between the foot (10) and the head (11), wherein the angle α is preferably > 90°.

10. Electroweld fitting (1) according to Claim 9, characterized in that the angle α is arranged on both sides of the head (11).

11. Electroweld fitting (1) according to one of Claims 1 to 10, characterized in that the heating wire winding (4) forms two heating zones (12), wherein the heating zones (12) each have a plurality of windings, wherein the two heating zones are connected to one another.