SK282405B6 - Clip of thermally weldable material - Google Patents

Abstract

Clamp made of heat-sealable material for repair of a weldable material of a pipe pipe (10) made, consisting of at least two pipes (10) surrounding segments (11, 12), at least one of which has a pipe outlet (13), with on the segments (11, 12) facing limiting edges (16, 17) for fastening to each other under pressure, with limiting edges (16, 17) projecting wedge-shaped curved extensions on one segment (11, 12), which lie on the clamp between the inner part of the adjacent segment (11 , 12) and a pipe (10) of pipes, and with heating mats (20) of wound electrically heated conductors (61), which are fixed on the inner surfaces (14) of the segments (11, 12). On each of the two limiting edges (16, 17) of each segment (11, 12), the extensions and clamps are arranged alternately and in addition to the respective adjacent segment (11, 12) and form teeth of either narrow rails (30) or wide rails (30). 36) locally projecting limiting edges (16, 17) and on the one hand pockets (40, 46) lying between them, which are formed below the limiting edges (16, 17) for accommodating slats (30, 36), the heating mats (20) having toothed conforming step profile from the forwardly projecting flaps (24, 26) in the region of the rails (30, 36) and from the gaps (25, 29) lying between them in the region of the flaps (40, 46).

Description

Technical field

The invention relates to a caliper made of thermally weldable material for a pipe of the same weldable material as a repair caliper, of at least two tubes, if necessary surrounding segments, at least one of which has a tube outlet and, if necessary, boundary edges on the segments which are Adapted to each other for attachment with limiting edges overlapping the wedge-shaped extensions on one segment, which, if necessary, are in the clamp between the inner surface of the adjacent segment and the pipe and with heating mats of wound electrically heated conductors fixed on the inner surfaces of the segments;

BACKGROUND OF THE INVENTION

It is known that such calipers are used, for example, for already installed, pressurized pipelines, where branching is required. For this purpose, yokes are used which have at least one outlet on at least one of the cylindrical segments arranged around the pipe. This outlet serves first to drill the pipe, but then also to guide the environment into the branch connected to the pipe. In other cases where there is a breakage point on the pipeline, a yoke from segments without a pipeline outlet is placed around the pipeline for repair purposes.

In the known caliper described in DE 295 12 309 U1, two segments are arranged around the duct, one segment being formed with two arms. Both arms extend over the entire axial length of the yoke at the boundary edges without interruption, and there are two wedge-shaped opposites, which serve to attach the boundary edges of this segment and overlap in the direction of another segment. In use, these passing extensions are located in the clamp between the inner surface of the adjacent segment and the pipe. In order to provide a sufficient sealing of the environment at the weld site, two positions of the heating mats are used, namely the first heating mat on the inner surface of the extensions and the second heating mat in the clamp on the inner surface of the adjacent segment. This requires high construction costs and higher heating energy as a result of the two-position welds.

In order to connect the shrink sleeve between the two jacket tubes of the tubular connection, the band heating mat is placed in the gap between the jacket tube and the sleeves displaceable thereon, as described in DE 37 20 577 A1, where the contact ends are at the end of the heating mat strip they are staggered to one another and, if necessary, interfere with one another. The heating mat is a separate component which is arranged as a loose strip in the form of a circle around the jacket tube and forms a two-layer welded joint, mainly with the peripheral surface of the jacket tube and further with the inner surface of the impacted sleeve. There are no problems with sealing any one of the at least two cylindrical segments of the assembled caliper.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a caliper of the above type which achieves high sealing of welded joints at very low production costs and low heating energy consumption.

SUMMARY OF THE INVENTION

SUMMARY OF THE INVENTION The invention solves the problem by providing a caliper of thermally weldable material for repairing the weldable material of a manufactured pipe tube, comprising at least two tube surrounding segments, at least one of which has a tube outlet, with limiting edges facing each other for fastening under pressure , with limiting edges protruding from the wedge-shaped curved extensions on one segment that lie on the clamp between the inner part of the adjacent segment and the pipe, and with heating mats of wound electrically heated conductors which are fixed on the inner surfaces of the segments. It is an object of the invention that at each of the two limiting edges of each segment, the extensions and clamps are arranged mutually aligned and complementary to the respective adjacent segment and form a toothing made of narrow or wide strips of locally projecting limiting edges and below the limiting edges for accommodating the strips, the heating mats having a toothed conformal step profile from the projecting flaps in the region of the strips and the gaps lying between them in the region of the pockets.

According to a preferred embodiment of the present invention, the toothing at the limiting edges of the segment divides the heating mat into three different axial sections, two of which are end sections having a circular closed heating collar around the pipe tube where the wound conductors extend in the form of a ring from the bottom of the pocket; from the end of the bar on one edge to the end of the bar or the bottom of the pocket on the opposite edge and one or more offset sections which form a heating strip in the region of one edge of the segment and extend at least partially into the extended wide bars winding conductors extending only between the two end sections.

According to a further preferred embodiment of the present invention, the cross-sectional thickness of the wedge-shaped narrow strip or the wide strip in the limiting edge of the leg rest segment is greater than the thickness of the material softening zone which occurs when the electric conductor is heated in the strip.

According to a further preferred embodiment of the present invention, the electric conductor is arranged in an unheated condition at an axial distance to the side surfaces of the narrow strip or the wide strip which is greater than the thickness of the material softening zone during heating.

According to a further preferred embodiment of the present invention, the segment heating mat is formed in its segmented contour profile by the threads of a single running electrical conductor.

According to a further preferred embodiment of the present invention, the wires of the mats of all segments are electrically connected to each other in series and connected to the welding machine for uniform heating.

According to a further preferred embodiment of the present invention, the threads of the conductor consist of parallel arms with the arches therebetween, the arms extending in the region of the two ring of the closed heating sleeve forming the end sections of the heating mat in the circumferential direction of the cylinder. It extends in the direction of the axis of the cylinder of the segment, while the arches lie on the line of the step contour profile of the flaps or the gaps of the heating mat.

SK28B405 Β6

According to a further preferred embodiment of the present invention, the electric conductor consists of one meander wire in the form of a wavy line of the running wire and the meander wire is embedded in the threads forming a heating mat.

According to a further preferred embodiment of the present invention, the meandering wire on its both of the heating strand of the projecting ends comprises further running end pieces of the wire which are connected to the electrical contacts of the segment.

According to a further preferred embodiment of the present invention, the steps in the outline profile of the heating mat are rectangular.

According to a further preferred embodiment of the present invention, the segments on at least one of their two axes of parallel limiting edges comprise a radial edge flange, with fastening means extending between the edge flanges of adjacent segments.

According to a further preferred embodiment of the present invention, the edge flange of the segment on its inner surface has a longitudinal rib in which a heating strip parallel to the axis of the heating mat is fixedly inserted, a longitudinal groove formed from the opposite edge flange of the segment and / or the adjacent segment. for accommodating a longitudinal rib having a clear width and a depth corresponding to the shape of the longitudinal rib.

According to a further preferred embodiment of the present invention, the narrow strip or the wide strip forms a passageway for the softened material.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is illustrated in the drawings, in which: FIG. 1 shows, in cross-section and cut-out, both segments of the repair caliper according to the invention before being fixed to the pipe; FIG. 2 shows the segments of FIG. 1 after their attachment to the pipe; FIG. 3 is a perspective view of the lower segment of FIG. 1 for a concave inner surface, FIG. 4 shows the lower segment shown in FIG. 3, also in a perspective view, but viewed from the opposite side, FIG. 5 is a perspective view analogous to FIG. 3 shows the upper segment of the caliper shown in FIG. 1 or FIG. 2, FIG. 6 shows the planar deployment of the heating mat segment on the concave inner surface of the segments shown in FIG. 3 or 5, which show both their particular contour profile and the winding sequence for their embodiment of a serving electric conductor, FIG. 7 is a view analogous to FIG. 6 is a plane deployment of the heating mats of the segments of FIG. 3 and 5 after having been fixed together with their limiting edges, FIG. 8 and 9 show schematically, but FIG. 7, two alternative shapes of the heating mat outline, FIG. 10 is a view analogous to FIG. 2 shows a cross-section of an alternative embodiment of a caliper according to the invention, FIG. Fig. 11 shows a front view of parts of a used electric conductor in the form of a meander with double-sided for the purpose of connecting the arranged elongated pieces of wire; 12 is an enlarged front elevation view of a heating cord in which the electrical conductor of FIG. 11 and who can also be used in other pipe-to-pipe welding fixtures such as welded sleeves; FIG. 13 is a cross-sectional view of the heating strand of FIG. 12 along the section line XIII-XIII taken there; and FIG. 14 shows an enlarged view but FIG. 12 and 13 are a reduced, longitudinal sectional view of the wall of the mold used for the injection molding of the segment of FIG. 3 to 5.

DETAILED DESCRIPTION OF THE INVENTION

The repair caliper shown in FIG. 1 and 2 consists of two cylindrical segments 11, 12 which, if necessary, are intended to be fixed at a desired location on the pipe 10 by welding. The cylindrical segments 11, 12 will be hereinafter referred to as "segments". The pipe 10 and also the two segments 11, 12 are made of a material suitable for thermal welding. Both segments 11, 12 are, as shown in FIG. 3 and 5 of the same shape, but they differ in that only the upper segment 12 is provided with a tubular outlet 13. The tubular outlet 13 has a front opening 15 shown in FIG. 1 and 5 and a partially cylindrical concave inner surface 14. Since the two segments 11, 12 are of the same construction, it is sufficient to describe only one, namely the lower segment 11.

The segment 11 has limiting edges 16, 17 to which radial edge flanges 18, 19 are attached for fixing. The fastening means in this case consist of pins 58, shown in FIG. 2, which are shown in FIG. 3, the visible bores 57 of the edge flanges 18, 19 are screwed together by nuts 59. In each case the concave inner surfaces 14 of the two segments 11, 12 each have a heating mat 20 having a special shape, best seen in FIG. 6. The heating mat 20 is also in this case also profiled in both segments 11, 12, so that in FIG. 6 follow the planar deployment of the heating mat 20 of the upper segment 12 of FIG. Third

In FIG. 6, the contours of the upper segment 12 were also bent at an angle to the plane and indicated by a dashed line. The two limiting edges 16, 17 of the segment 12 are advanced. A special feature of the heating mat 20 is that along its two limiting edges 16, 17, there are different contour profiles whose contour lines 26, 27 are shown in FIG. 6 marked with dashed lines. These contour lines 26, 27 are complementary to each other in the present case. There are narrow flaps 24 and wide flaps 28, with which both contour lines 26, 27 overlap both limiting edges 16, 17 and between them narrow gaps 25 and wide gaps 29, which extend below both limiting edges 16, 17. This articulated contour the profile acts on the partially cylindrical concave inner surface visible in FIG. 5 naturally such that, as shown along section line I-I in FIG. 5, the derived cross-section through the wide flap 28, the heating mat 20, the partial cylindrical shape of the concave inner surfaces 14 continues outwardly through the respective limiting edge 17. This shape is naturally reinforced respectively by the material of the segment 12 or 11, which fills the flaps 24, 29 on the rear side 34 facing away from the inner surface 14 of the segment, thereby forming respective narrow strips 30 overlapping limiting edges 17 and wide strips 36. or narrow strips 30 are also formed integrally with the respective segment 12 and have in FIG. 1, the curved cross-section 33 is highlighted by hatching. This curved cross-section 33 is not merely a continuation of the concave cylindrical portion of the inner surface

SK28B405 Β6

14, but also in that the rear side 34 of the wide strip 36 or narrow strip 30 is curved, albeit with a flatter shape compared to the concave inner surface 14. Thus, the wide strip 36 or narrow strip 30 has a free end 31 of the strip a tapered cross-section having a wedge shape. In the foot region 32, the wide strip 36 or the narrow strip 30 has a larger cross-section 35 than in the region of the head 31 where the wedge top is located.

In the region of the intermediate gaps 25, the ratios are reversed. Indeed, these gaps 25 are used to provide, with suitable recesses in the concave interior surface 14 of the pocket segment 40 with the described peak shape 31 to 34, an additional clearance distance 41a of depth 42 having a corresponding curvature 43. This is explained in FIG. 1 by means of a depression 46 having the shape of the pocket 41 to 43 described in FIG. 4, it only distinguishes the pocket 40 as shown in that it is formed on the wide gap 23 of the heating mat 20 indicated in FIG. 6. In FIG. 6, the dimensions and length of the recess 46 and, in the present case, the five pockets 40 are indicated by the dot hatching of the limiting edge of the segment 16.17.

The contour profile of the heating mat 20 shown in FIG. 6 of one segment 11 or 12 can be divided into three sections 21 to 23 which extend along the two contour lines of the profile 26, 27 and are differently profiled. Of the two end regions 37, 38 shown in FIG. 2 of the respective segment, two sections 21, 22 are designated as " heating collars " as these sections, as seen from the case of use in FIG. 7 in plan view, it is evident that they surround the tube 10 provided with the yoke of FIG.

2. FIG. 7 the two segments 11, 12 with their limiting edges 16,17 are in contact, it can be seen that the flaps 24 of one segment 11 fill the gaps 25 of the adjacent segment 12, which in turn is five for the flaps 24 of segment 12 and the gaps 25 of segment 11.

Between the two abutting limiting edges 16, 17, FIG. 7, the movement slots 39 of the two segments 11, 12 shown in an arrow. The two contour lines 26, 27 adjacent to each other are also shown in dotted lines. It can be seen that the lines 26,27 have a step profile which crosses the contact gap 39 between the two segments 11, 12 several times. There is a kind of "toothing" between the gapless heater collars 21 of the two segments 11, 12. The circular closed shape results from FIG. 7, when the planar position of the two heating mats 20 shown therein is cylindrical, in a manner corresponding to the two concave inner surfaces 14 of the segments 11, 12 where the heating mats 20 are fixedly mounted. Also, both of FIG. 7, the boundary edges 17, 16 of the two segments 11, 12, which are shown at the top and at the bottom of the line, are in contact with each other.

As already seen in FIG. 6, the length of the flaps 24 and the gaps 25 in the region of the heating collars 21 is complementary to both lines of the contour profile 26, 27. The flaps 24 and the gaps 25 are in opposing pairs. A similar arrangement is also provided for the two opposite ends 38 of the segments in FIG. 2, of the heating sleeves 22 shown. However, in the sleeve 22, the flaps 24 and the gaps 25 are interchanged with respect to the heating sleeve 21. As in FIG. 6 in the heating collar 22 indicated by the dashed contour profiles 26, 27, the shape of the collar 22 results from a double mirror image around two perpendicular axes of symmetry from the corresponding profile of said heating collar 21. Mathematically speaking, the heating collar 22 has centrally aligned to the heating collar 21. outline. As shown in FIG. 2 and FIG. 4, this symmetrical shape also applies to the spatially curved narrow strips 30 in the region of the flaps 24 and to the pockets 25 arranged at the gaps 40.

Said third section of the heating mats 20 is shown in FIG. 6, the heating strip 23, which is substantially parallel to the axis of the heating mat 20 and arranged between the two heating collars 21, 22, is visible. This heating strip 23 forms a flap 24 on the heating collar 22 and can thus be as shown in FIG. 6, connected to said wide flap 28. According to FIG. 6, one half 44 of the heating strip 23 is disposed above the limiting edge 17 of the segment and is thus, together with the adjacent flap 24 of the second heating sleeve 22, fixedly embedded in the concave inner surface of the curved wide strip 36 described above. 3. The second half 45 of the heating strip 23 is disposed below the limiting edge 17 on the concave inner surface 14 of the segment 11 and 12, respectively. It is significant, as best seen in FIG. 6, the heating strip 23 lies off-center, so that the adjacent inner storage surface 47 of the segment is outside the heating mat 20. In this space, FIG. 6, the through hole 15 shown on the segment 12 of the seated outlet 13 of the pipe 10 is shown in dashed lines. As shown in FIG. 2, the outlet 13 of the pipe 10 has a diameter of the opening 48, which may be equal to the diameter 49 of the pipe 10. If necessary, they could also be shown in FIG. 6, outside the through hole 15 in the inner receptacle 47, arranged terminals 56 filled with threads of the electrical conductor, thereby contributing to the formation of the heating mat 20.

However, in order to save heating energy, relatively narrow heating strips 23 are formed, since these are, as shown in FIG. 7, with their two heating steam halves 44,45 mounted on both sides of the separating slot 39, and thus form a very effective, environmentally impermeable welded connection. These ratios are particularly well observable in FIG. 2, wherein the two segments 11, 12 are joined together in a caliper on the pipe 10. In FIG. 2, a curved wide strip 36 provided with a heating strip 23 extends into an additionally curved recess 46. In these regions 36, 46, a yoke wall is formed to which both segments 11, 12 with their weldable material contribute. Thus, the most important areas of the concave inner surface 14 of the caliper are covered with a heating mat 20, as is evident in FIG. 2, a heating strip 23 is shown. As already mentioned, at the location of the end regions 37, 38 of the segment 11 or 12 defining the heating collars 21, 22 there is an overall arrangement of the described parts of the heating mat on the inner surface 14 of the caliper.

The fastening means 57, 59 previously described are the two segments 11, 12 in FIG. 2 visible flanges pressed together. A stop 35 arranged on the radial flange 19 makes it possible to determine the external dimension of the relative compression of the two segments 11, 12. Thereby, by means of the curved depression 46, the wide strip 36 will be pressed against the skirt surface 54. This naturally applies in the same sense to the narrow stripes 30 and pockets 40 of approximately the same shape. As a result, a good radial pressure of the assembled segments 11, 12 is also created on these stirrups on the tube surface 54. When the heating mat 20 is heated, the material capable of welding at the contact areas between the concave segment surface 14 and the convex casing surface 54 of the conduit will liquefy. Here, the softened material zone 50, as shown in FIG. 2 shown by dot hatching.

This softened material 50 could be pushed out through the contact gap 39 between the two segments 11, 12 due to pressure. In many cases, this is even required, because by this way of expelling the material outwards, an indicator of good welding completion is provided at the intended location. In other cases, however, this does

SK28B405 Β6 does not require what can be equally easily accomplished by the invention. Indeed, only FIG. 1 in the leg region 23, the slight cross-sectional thickness 35 of the wide strip therein 36 or a similar narrow strip 30 can be made slightly larger than that shown in FIG. 2, the thickness 51 of this softened material zone 50 is shown in the form of a wedge-shaped wide strip 36 or a narrow strip 30.

Fig. 8 and 9 show schematically alternative ratios for the contour profiles of the heating mats 20 for both the segments 11, 12 indicated by the dashed lines in FIG. 7 a comparable representation. The position of the two heating mats 20 ', 20 is shown by opposite hatching and shows only the complementary profile lines 26', the IT contour, respectively 26 ', 27 of the two longitudinal sides, also the broken edges 16', 17 'and 16', respectively. 17. FIG. 8, a trapezoidal or jagged profile 26 ', 267' is used instead of the rectangular graduated profile described. In FIG. 9, the contour profiles 26, 27 have the shape of wines. These contour profiles can be formed by suitable threading of the strand 60 comprising the electric conductor without further measures, as will be described in more detail below.

As mentioned and as shown in FIG. 1, the tubular spout 13 has a through hole 15 formed in the concave inner surface 14 on the front side. After heating the heating mat 20 installed in both segments 11, 12 and cooling the melt, it is easy to determine by pressure test whether the welded connection is truly flawless. It is only necessary to connect a pressure source and a pressure gauge to the pipe outlet 13. The pipe 10 at the location of the segments 11, 12 is not yet drilled and is below an arbitrarily high inner such. Only when the pressure test has been satisfactorily carried out, the pipe 10 is returned, which can also be carried out through this pipe outlet 13 or through the opposite segment 11 provided with a similar pipe outlet. Then, as shown in FIG. 2, inside the tubular outlet 13, a bore 77 in the tubular pipe 10, thereby creating an environmental flow in the tubular outlet 13.

Fig. 10 shows a cross-section similar to FIG. 2 shows an alternative embodiment of a segment 11 'comprising a heating strip 23' to FIG. 6 of an analogous heating mat 20 '. In FIG. The segments 11 ', 12' shown in FIG. 10, one of which may also carry a tubular outlet 13 ', have a longitudinal rib 52 arranged vertically on the inner surface 68 of the edge flange 18', while a longitudinal groove 53 is formed on the opposite inner surface 59 of the edge flange 19 '. which is complementary to the shape of the longitudinal rib 52 in the shape and size. In the central region of the heating mat 20 therein where the heating strip 23 'lies, the contact gap between the flange 18', 19 'is also sealed by welding. With the heating collar 21, 22 also in this case formed in the end bands of the segments 11 'and 12', the shape-fitting narrow strips 30 and the pockets 40 are naturally described again. These heating collars develop welding areas which also surround the entire surface and on all sides, the duct surface 54.

The conductor 61 used in the heating mat 20 has a special shape and represents only one component of one, in FIG. 11 to 14 of the illustrated heating heater 60 shown. The wire of the conductor 61, consisting of an electrically conductive material, is transformed into a 63 meander shape. This meander shape 63 is used because the wire is guided by two interlocking gears whose tooth shape forms the arcs of the meander 63. The stretched sections of the wire 64 are formed simply by having the gears spaced apart at these points of automatic wire feed 61 so distant that their inner teeth no longer work in me. Meander 63 is a straight-running wave line. As shown in FIG. 11, the meander 63 is provided with elongated, extending end portions of the wire 64 that serve to connect to the electrical contacts that are disposed on the segments 11, 12. These contacts serve to connect the welding machine. The connected contacts connected to one end of the heating mat 20 are connected to each other by cable, whereby the two heating mats 20 of the segments 11, 12 are heated simultaneously and thus lead to a uniform weld at all points of the finished caliper.

The Meander 63 will now be as shown in the enlarged view of FIG. 12, fixedly embedded in a flat sheet 62 of thermally weldable material, which now constitutes the second component of said heating strand 60. This flat sheet 62 has, as shown in FIG. 13, a cross-section of a flat rectangle whose width 65 is only slightly greater than that of FIG. 11 an observable length of 67 wire. The strip thickness 66 is also only slightly greater than that shown in FIG. 13, a visible diameter of 71 wire.

Fig. 14 shows a longitudinal section through the wall of the injection molding tool 76 in which the segment 11 or 12 is to be produced. Around the concave interior surface 14 of the segment 11, 12 there is a convex interior surface 88 of the mold with grooves 70 into which the heating elements are pressed. the strand 60 before the segment material is injected. Separation bridges 61 may be formed between the grooves 70, which converge so sharply that they are adjacent, already in FIG. 14, the threads 73 of the heating strand 60 may touch. The threads 73 of the heating strand 60, disposed in the inner mold surface 78, will be firmly seated in the grooves 70. By introducing the segment material into the mold, the heating strand 60 with its threads 73 is firmly seated in the segment 11,12 to be formed.

One possible course of the threads 63 of the heating strand 60 is shown in FIG. 6. According to FIG. 6, the threads 73 consist of parallel arms 74 and arcs 75 disposed therebetween. The threads of the heating strand 60 are in this case accommodated in the heating collars 21, 22 as opposed to the threads housed in the intermediate heating strip 23. In FIG. 5 is a heating strand 60 which, for the sake of simple illustration, is drawn in a round profile and only its parallel arms 74 are shown. In FIG. 5 shows the visible ends of the parallel arms 74 in FIG. 6, the arcs 75 shown in FIG. 5 and 6, the parallel arms 74 of the heating strand 60 extend in the region of the heating collars 21, 22 in the circumferential direction, but in the region of the heating strip 23 in the axial direction of the cylinder segment 11. The arcs 75 are then mounted. 6, on the dashed lines 26, 27 of the profile contour.

Such mounting of the electrical conductor 61 in the heating strand 60 in the form of flat, juxtaposed threads 73 is particularly effective for the welding process. The use of such a heating wire 60 is therefore not limited to the segments 11, 12 of the described caliper. Other welded fittings could also be equipped with electric conductors in this way. For example, Welded sleeves that bluntly seal the airtight tubes. Another possibility of using such heating strands 60 is on the seat surfaces of bore fittings or valve bore fittings to be welded to the pipe tubes 10 in an analogous manner. Thus, the manufacture and use of the heating strand 60 has a separate meaning within the meaning of the invention.

Claims (13)

PATENT CLAIMS A caliper of thermally weldable material for repairing a weldable material of a manufactured pipe (10) comprising at least two pipe (10) surrounding segments (11, 12), at least one of which has a pipe outlet (13), with segments ( 11, 12) facing each other with limiting edges (16, 17) for fastening under pressure, with limiting edges (16, 17) overlapping wedge-shaped curved extensions on one segment (11, 12), which lie on the clamp between the inner part of the adjacent segment (11, 12) and a pipe (10), and with heating mats (20) of wound electrically heated conductors (61) mounted on inner surfaces (14) of the segments (11, 12), characterized in that on each of of both limiting edges (16, 17) of each segment (11, 12), the extensions and clamps are arranged alternately and complementary to the respective adjacent segment (11, 12) and form a toothing on the one hand of narrow strips (30) or wide strips (36) locally overlapping the boundary edges (16, 17) and, on the other hand, interposed pockets (40, 46) formed below the boundary edges (16, 17) for receiving the strips (30, 36), wherein the heating mats (20) have a toothed conformal step contour profile from the forwardly projecting flaps (24, 26) in the region of the strips (30, 36) and the interstices (25, 29) lying between them in the region of the pockets (40,46). The caliper according to claim 1, characterized in that the toothing at the limiting edges (16, 17) of the segment (11, 12) divides the heating mat (20) into three different axial sections (21, 22, 28), two of which are end sections (21, 22) having an annular closed heating collar around the pipe (10) where the wound conductors (61) extend in the form of a portion of the ring from the bottom of the pocket or from the end of the strip at one limiting edge (16) to the end the strips, optionally to the bottom of the pocket, on the opposing limiting edge (17), and one or more offset sections (28), which form a heating strip (23) in the region of one limiting edge (17) of the segment (11, 12) and extend at least partially to extended wide strips (36) where the wound conductors (61) are guided only between the two end sections (21, 22). Caliper according to claim 1 or 2, characterized in that the cross-sectional thickness (35) of the wedge-shaped curved narrow strip (30) or the wide strip (36) in the limiting edge (16, 17) of the upstream segment (11, 12). the legs (32) is greater than the thickness (51) of the material softening zone when the electrical conductor (61) is heated in the bar (30, 36). Caliper according to at least one of Claims 1 to 3, characterized in that the electric conductor (61) is arranged in an unheated state at an axial distance to the side surfaces of the narrow strip (30) or the wide strip (36) which is greater than the thickness. (51) material softening areas during heating. Caliper according to at least one of Claims 1 to 4, characterized in that the heating mat (20) of the segment (11, 12) is formed in its articulated contour profile (26, 27) by the threads (73) of a single running electrical conductor (61). ). The yoke according to claim 5, characterized in that the conductor (61) of the heating mat (20) of all the segments (11, 12) are electrically connected to each other in series and connected to the welding machine for uniform heating. Caliper according to at least one of Claims 1 to 6, characterized in that the threads (73) of the conductor (61) consist of parallel arms (74) and bends (75) lying between them, the arms (74) running in the region of both. , the partial ring of the closed heating sleeve forming the end sections (21, 22) of the heating mat (20) in the circumferential direction of the cylinder, and in the region of the intermediate heating section (28) the heating band (23) extends (11, 12), while the arches (75) lie on the line of the step contour profile (26, 27) of the flaps (24, 28) or the gaps (26, 29) of the heating mat (20). The yoke according to at least one of claims 1 to 7, characterized in that the electric conductor (61) consists of one meander wire (63) in the form of a wavy line of the running wire and that the meander wire (63) is embedded in the threads (73). ) forming a heating mat (20). The yoke according to claim 8, characterized in that the meandering wire (63) on both of the protruding end heating wire (60) comprises further extending wire end pieces (64) which are connected to the electrical contacts of the segment (11, 12). ). Caliper according to at least one of Claims 1 to 9, characterized in that the steps in the contour profile (26, 27) of the heating mat (20) are rectangular. Caliper according to at least one of Claims 1 to 10, characterized in that the segments (11, 12) on at least one of their two axes of parallel limiting edges (16, 17) have a radial edge flange (18, 19) and fastening means (57 to 59) extend between the edge flanges (18, 19) of adjacent segments (11, 12). Caliper according to at least one of Claims 1 to 11, characterized in that the edge flange (18 ') of the segment (11) has on its inner surface a longitudinal rib (52) in which the heating strip (23') is fixedly mounted, parallel to it. with the axis of the heating mat (20), a longitudinal groove (53) for receiving the longitudinal rib is formed on the inner surface (69) of the flange from the opposite edge flange (19 ') of this segment (11') and / or the adjacent segment (12 ') (52) having a clear width and a depth corresponding to the shape of the longitudinal rib (52). Caliper according to at least one of Claims 1 to 12, characterized in that the narrow strip (30) or the wide strip (36) form an outflow passage for the softened material (50).