Method for manufacturing an electric tubular heating element

Abstract

Method for manufacturing an electric tubular heating element (10,20,30,40,50,60,70,80,90) comprising the steps - Including at least one opening (16, 26, 36, 46, 56, 66, 76, 86, 96) through a resistance wire and / or contouring the circumferential surface of a resistance wire (110, 120, 130, 140) to provide an electrical heating element (14, 24, 34, 44, 54, 64, 74, 84, 94, 114, 124, 134, 144, 154, 164, 174, 184), - Arranging the electric heating element (14, 24, 34, 44, 54, 64, 74, 84, 94, 114, 124, 134, 144, 154, 164, 174, 184) inside a tubular metal sheath (11, 21, 31, 41, 51, 61, 71, 81, 91), and - Electrical insulation of at least sections of the electric heating element (14, 24, 34, 44, 54, 64, 74, 84, 94, 114, 124, 134, 144, 154, 164, 174, 184) relative to the tubular metal sheath (11, 21, 31, 41, 51, 61, 71, 81, 91), wherein at least one opening (16, 26, 36, 46, 56, 66, 76, 86, 96) passing through the resistance wire is filled with an electrically insulating material (12, 22, 32, 42, 52, 62, 72, 82, 92, 158, 168, 178) after the electric heating element (14, 24, 34, 44, 54, 64, 74, 84, 94, 114,124,134,144,154,164,174,184) the filling of the opening (16,26,36,46,56,66,76,86,96) through which the resistance wire passes with an electrically insulating material by inserting a rod (158,168,178,188) made of the electrically insulating material into the opening (16,26,36,46,56,66,76,86,96) through which the resistance wire passes, and in which the electrical heating element (14,24,34,44,54,64,74,84,94,114,124,134,154,164,174,184) with at least one connecting wire or connecting bolt (15, 25, 27, 35, 37, 45, 55, 57, 65, 67, 75, 77, 85, 87, 95, 97, 155, 157, 165, 167) at least one unheated area of ​​the electric tubular heating element (10, 20, 30, 40, 50, 60, 70, 80, 90) is generated, , characterized in that the rod (158, 168, 178, 188) made of electrically insulating material is inserted into a through or blind opening in the connecting wire or connecting bolt (15, 25, 27, 35, 37, 45, 55, 57, 65, 67, 75, 77, 85, 87, 95, 97, 155, 157, 165, 167), the cross-section of which is adapted to the cross-section of the opening (16, 26, 36, 46, 56, 66, 76, 86, 96) provided in the resistance wire, until the opposing end faces of the connecting wire or connecting bolt (15, 25, 27, 35, 37, 45, 55, 57, 65, 67, 75, 77, 85, 87, 95, 97, 155, 157, 165, 167) and of the electric heating element (14,24, 34,44,54,64,74,84,94,114,124,134,144,154,164,174,184) are in contact with each other.

Description

[0001] The invention relates to a method for manufacturing an electric tubular heating element.

[0002] Electric tubular heating elements are a type of electric heating device that has been known for many years. They are characterized by the fact that the electric heating element is arranged inside a tubular metal casing, where it is electrically insulated in the radial direction from the tubular metal casing by being embedded in an electrically insulating but thermally conductive material, in many cases magnesium oxide, to prevent an unwanted short circuit.

[0003] Such electrical heating elements and methods for their manufacture are known, for example, from US 9 468 041 B2, DE 19 17 256 A and DE 10 2019 107 144 A1.

[0004] Especially in applications where the available installation space is very small and relatively low voltages, e.g., a 12V or 48V vehicle electrical system, must be used, meaning that high currents must flow to provide the desired heating power, the question always arises as to how to accommodate the low resistance and thus the large wire cross-section in such a confined space so that it can withstand thermal cycling over a long period of time, and how to ensure a reliable connection with a small cross-section between the unheated and heated zones for such high current loads.

[0005] This problem is solved by a method for manufacturing such an electric tubular heating element with the features of claim 1. Advantageous further developments of the invention are the subject of the respective dependent claims.

[0006] The term "electric tubular heating element" is used extensively in this patent specification and specifically includes heating cartridges.

[0007] An electric tubular heating element producible according to the invention has a tubular metal jacket in the interior of which an electric heating element is arranged. This element is formed from a resistance wire and is at least partially electrically insulated from the tubular metal jacket by an electrically insulating material. The resistance wire forming the electric heating element has at least one opening and may have a contoured circumferential surface.

[0008] In general terms, a resistance wire used to form an electrical heating element can be described as a general cylinder in the mathematical sense, created by shifting a closed plane curve that defines the cylinder's cross-section. Typically, but not necessarily, this closed plane curve is a circle, and the shift is linear and perpendicular to the plane when the resistance wire is stretched.

[0009] An opening penetrating the resistance wire from which the electrical heating element is formed extends from a point on one side of the resistance wire, through the wire, to the other side. However, it does not necessarily have to pass through the center of a cross-section of the resistance wire, but can also run asymmetrically, e.g., laterally offset from its center or central axis, or be arranged in such a way that it encloses an edge region, thus altering the cross-sectional contour of the resistance wire.

[0010] A resistance wire has a contoured circumferential surface within the meaning of this description if its cross-sectional area is locally reduced, with this reduction preferably originating from the outer edge of the cross-sectional area. It can be designed as an annular groove or a local recess extending in the direction of the resistance wire, or it can be formed by a continuous contour, for example, a groove extending spirally along the outer surface of the resistance wire.

[0011] For the sake of completeness, it should be emphasized that such contoured circumferential surfaces can be produced in particular using machining techniques, but also by punching, laser treatment, or waterjet cutting. However, depending on the specific geometry desired, in some embodiments they can also be produced by a global deformation of the heating conductor, in particular by coiling, folding, or bending along a longitudinal axis or the direction of extension of the heating conductor (preferably while it is extended).

[0012] Providing such an opening can solve a number of the problems mentioned above. Depending on its specific design, it can significantly contribute to the electrical heating element's ability to better withstand mechanical stresses during thermal load changes, increase the available contact area for making the electrical connection and thereby reduce the relevance of local contact resistances, and / or allow a given cross-sectional area to be realized with a larger surface area, which can noticeably reduce the surface load on the electrical heating element.

[0013] It should also be noted that such a surface modification – possibly supplemented by further measures – can be designed in such a way as to effect a local adjustment of the heating power in a section of the electric heating element and thus of the electric tubular heater, for example if a copper tube is pressed onto the resistance wire in the area of ​​an annular groove, which then results in a local reduction of the heat generated in this area, whereas the corresponding configuration with only the annular groove would result in a local increase of the heat generated in this area.

[0014] The electric tubular heating element, in particular the electrically insulating material, can preferably be compacted at least in sections.

[0015] For the stability and longevity of the electric tubular heater, it is advantageous that the openings through which the electric heating element passes are filled with electrically insulating material. Magnesium oxide is a material well-suited for many applications.

[0016] It is particularly preferred if the opening extends lengthwise through the electric heating element, so that the electric heating element has the shape of a tube. This is especially the case if the cross-section of the opening is smaller than the cross-section of the electric heating element and completely overlaps the electric heating element.

[0017] In particular, if the cross-section of the opening exceeds the cross-section of the electric heating element before the opening is created at exactly one point, the creation of the opening results in a tube with a side wall that is open along its entire length. This can be useful, for example, to provide an electric heating element with a given cross-section (namely, that of the "heating element blank" before the opening minus the cross-section of the opening), but to allocate a larger surface area to this cross-section, which is relevant for the resulting heating power, and thus reduce the load on it.

[0018] However, it is also possible that the cross-section of the opening exceeds the cross-section of the electrical heating element at more than one point before the opening is introduced, so that the electrical heating element is divided into several segments by the introduction of the opening.

[0019] The variety of achievable configurations and properties of the electric heating element is further increased by having the resistance wire from which the element is formed perforated by at least one second opening, oriented in a different direction than the first opening. On the one hand, such a second opening can facilitate filling the openings with electrically insulating material. On the other hand, it can also be used for other purposes, for example, to provide a means of better absorbing mechanical stresses during load changes.

[0020] Another preferred embodiment of the second opening consists in the fact that, in the case of a tubular resistance wire, it is inserted at least partially in a helical pattern through the wall of this tubular resistance wire. In this way, thermally induced changes in length of the electrical heating element during temperature changes can be particularly well compensated.

[0021] At least after the openings in the electric heating element have been filled, the opening is completely or at least partially closed by a connecting wire or bolt that is in electrical contact with the electric heating element. In this way, an electrical connection can be provided that simultaneously defines a substantially unheated section of the electric tubular heater. A turned copper part can be used particularly advantageously for this purpose.

[0022] The inventive method for manufacturing such an electric tubular heating element comprises the steps - Creating at least one opening through a resistance wire and / or contouring the circumferential surface of a resistance wire to provide an electrical heating element, - Arranging the electric heating element inside a tubular metal sheath, - Electrical insulation of at least sections of the electrical heating element relative to the outer sheath.

[0023] Unlike before, the resistance wire is not only locally reshaped, particularly along its direction of extension in different directions to generate a desired trajectory or curve in space, for example by coiling or deforming its cross-section during a pressing step in the manufacturing process of an electric heater while installed in the heater, but it is provided in a processed state, in particular by either removing material at least locally or by carrying out a global reshaping process, in particular by, for example, coiling, folding or bending along a longitudinal axis or the direction of extension of the heating conductor or a heating conductor blank (preferably while it is stretched) or an axis parallel to it.

[0024] According to the invention, at least one opening passing through the resistance wire is filled with an electrically insulating material.

[0025] According to the invention, after the electrical heating element is provided, the opening through which the resistance wire passes is filled with an electrically insulating material by inserting a rod made of the insulating material into the opening. The material can be, for example, magnesium oxide. This method makes filling the opening particularly easy.

[0026] In the method according to the invention, at least one unheated area of ​​the electric tubular heater is created by connecting the electric heating element to at least one connecting wire or connecting bolt. This connection is made at the end face, which makes it possible that, with matching outer diameters of the electric heating element and connecting wire or connecting bolt, the installation space requirements are determined solely by the required dimensions of the electric heating element.

[0027] According to the invention, by inserting the rod made of electrically insulating material into a through or blind opening in the connecting wire or connecting bolt, the cross-section of which is adapted to the cross-section of the opening provided in the resistance wire, until the opposing end faces of the connecting wire or connecting bolt and the electrical heating element are in contact, a very easy-to-handle assembly is obtained, in which, in particular, the existence of good electrical contact between the connecting wire or connecting bolt on the one hand and the electrical heating element on the other hand can be verified and / or ensured, for example by welding or soldering.

[0028] A pre-configured assembly of this type can then be used to arrange the electrical heating element inside a tubular metal jacket. The assembly, consisting of an electrical heating element, an electrically insulating rod, and connecting wires or bolts, can be inserted into the tubular metal jacket, in particular allowing sections of the connecting wires or bolts to protrude from the tubular metal jacket or to be electrically connected to the tubular metal jacket on one side.

[0029] The invention is explained in more detail below with reference to figures illustrating exemplary embodiments. These show: Fig. 1a: A longitudinal section through a first electric tubular heating element that cannot be manufactured according to the invention, Fig. 1b: a cross-section through the first electric tubular heating element which cannot be produced according to the invention Fig. 1a, Fig. 2a: a longitudinal section through a second electric tubular heating element not producible according to the invention, Fig. 2b: a cross-section through the second electric tubular heating element which cannot be manufactured according to the invention Fig. 2a, Fig. 3a: a longitudinal section through a third electric tubular heating element not producible according to the invention, Fig. 3b: a cross-section through the third electric tubular heating element which cannot be manufactured according to the invention Fig. 3a, Fig. 4a: a longitudinal section through a fourth electric tubular heating element not producible according to the invention, and Fig. 4b: a cross-section through the fourth electric tubular heating element not producible according to the invention made of Fig. 4a, Fig. 5a: the components of an assembly for the manufacture of an electric tubular heating element, Fig. 5b an intermediate stage in the assembly of the component Fig. 5a, Fig. 5c: a cross-sectional view of the assembled component made of Fig. 5a, Fig. 6a: a variant of an assembly for the production of an electric tubular heating element in an intermediate stage analogous to Fig. 5b, Fig. 6b: a cross-sectional view of an end section of the assembled component made of Fig. 6a, Fig. 7a: an illustration of another variant of an electric heating element, Fig. 7b: a cross-sectional view of the variant from Fig. 7a, Fig. 8a: an illustration of another variant of an electric heating element, Fig. 8b: a cross-sectional view of the variant from Fig. 8a, Fig. 9a: a first example of an electric heating element with a contoured circumferential surface, Fig. 9b a longitudinal section through the electric heating element Fig. 9a, Fig. 10a: a second example of an electric heating element with a contoured circumferential surface, Fig. 10b a longitudinal section through the electric heating element made of Fig. 10a, Fig. 11: a third example of an electric heating element with a contoured circumferential surface, Fig. 12 a fourth example of an electric heating element with a contoured circumferential surface, Fig. 13: A fifth example of an electric heating element with a contoured circumferential surface, integrated into an electric tubular heating element not producible according to the invention, shown in longitudinal section, Fig. 14a: an exploded view of a fifth electric tubular heating element, Fig. 14b: a first variant for the connecting wires or connecting bolts of the electric tubular heating element made of Fig. 14a, Fig. 14c: a second variant for the connecting wires or connecting bolts of the electric tubular heater made of Fig. 14a, Fig. 15a: a longitudinal section through the electric tubular heating element made of Fig. 14a, Fig. 15b: a longitudinal section through the electric tubular heating element made of Fig. 14a, however with connecting wires or connecting bolts according to Fig. 14b, Fig. 16a: an exploded view of a sixth electric tubular heating element, Fig. 16b: the electric tubular heater Fig. 16a in longitudinal section, Fig. 16c: a variant for the connecting wires or connecting bolts of the electric tubular heating element made of Fig. 16a, Fig. 16d: a variant of the electric tubular heater made of Fig. 16a with connecting wires or connecting bolts according to Fig. 16c, Fig. 16e: a representation of the heating element assembly from Fig. 16c, Fig. 16f: a schematic representation of the manufacture of an electric heating element, as it is in Fig. 16a is used, Fig. 17a: a first variant of a cross-section through an electric tubular heating element, Fig. 17b: a second variant of a cross-section through an electric tubular heating element, Fig. 17c: a third variant of a cross-section through an electric tubular heating element, Fig. 17d: a fourth variant of a cross-section through an electric tubular heater, Fig. 17e: a fifth variant of a cross-section through an electric tubular heating element, Fig. 17f: a sixth variant of a cross-section through an electric tubular heating element, and Fig. 17g: a seventh variant of a cross-section through an electric tubular heating element.

[0030] Fig. 1a and Fig. Figure 1b shows a first electric tubular heating element 10 with a tubular metal jacket 11, in the interior of which an electric heating element 14 is arranged. In this embodiment, the electric heating element 14 is in electrical contact with the tubular metal jacket 11, which serves as a return conductor, via the electrically conductive base plate 13, but is partially – namely in its other sections – electrically insulated from the tubular metal jacket 11 by the electrically insulating but thermally conductive material 12, e.g., magnesium oxide.

[0031] A special feature of the electric heating element 14 is that it is not, or no longer, made of a solid resistance wire. Rather, the resistance wire has an opening 16 extending lengthwise from the terminal end face to the bottom end face, giving it a tubular shape. The opening 16 is also filled with electrically insulating material. This material can be the same as the electrically insulating material 12 or a different electrically insulating material.

[0032] The electrical heating element 14 is powered via a solid connecting wire or connecting bolt 15, which can be made of copper, for example. It is worth noting that the connecting wire or connecting bolt 15 is inserted into the opening 16 to establish electrical contact with the electrical heating element 14, thereby minimizing the space required in the radial direction while simultaneously providing a large contact area.

[0033] Fig. 2a and Fig. Figure 2b shows a second electric tubular heating element 20 with a tubular metal jacket 21, in the interior of which an electric heating element 24 is electrically insulated from the tubular metal jacket 21 by the electrically insulating but thermally conductive material 22, e.g. magnesium oxide.

[0034] The electrical heating element 24 is also not, or no longer, made of solid resistance wire. In addition to the opening 26 extending lengthwise from one terminal end face to the opposite terminal end face, it has a plurality of further openings 28, each extending radially through it. This results, on the one hand, in a local additional increase in resistance, and on the other hand, facilitates the filling of the opening 16 with electrically insulating material if this is filled in a free-flowing state.

[0035] The electrical heating element 24 is supplied with power analogously to the embodiment described above via a solid connecting wire or connecting bolt 25, which can be made of copper, for example; however, since the tubular metal sheath 21 does not serve as a return conductor here, a second, identically designed connecting wire or connecting bolt 27 is provided on the opposite side of the electrical heating element 24.

[0036] Fig. 3a and Fig. Figure 3b shows a third electric tubular heating element 30 with a tubular metal jacket 31, in the interior of which an electric heating element 34 is arranged electrically insulated from the tubular metal jacket 31 by the electrically insulating but thermally conductive material 32, e.g. magnesium oxide.

[0037] The electrical heating element 34 is also not, or no longer, made of a solid resistance wire. Here, the resistance wire is penetrated lengthwise from one end face of the connection to the opposite end face of the connection by an opening 36, which has a central circular cross-sectional area arranged coaxially to the resistance wire, so that a tube remains after the central cross-sectional area has been inserted.

[0038] To supply this structure of the electric heating element 34 with current, as can be seen particularly well when considering the Fig. 3b recognizes that connecting wires or connecting bolts 35, 37 are used on both sides, which have a substantially rectangular cross-section, with the electrical contact to the electric heating element 34 being established via the narrow sides of the rectangle. In this way, which is also transferable to other embodiments of the electric heating element, an opening remains at the end face through which the electrically insulating material can be easily introduced into the openings in the electric heating element.

[0039] The one in the Fig. 4a and Fig. The electric tubular heating element 40 shown in Figure 4b, with tubular metal sheath 41, electrically insulating material 42, base 43, electric heating element 44 with opening 46 and connecting wire or connecting bolt 45, is largely analogous to the one shown above based on the Fig. 1a and Fig. The electric tubular heating element 10 described in 1b is constructed, which is why reference can be made to its description, whereby the aforementioned reference symbols apply to the Fig. 4a and Fig. 4b by adding thirty from the corresponding reference symbols of the Fig. 1a and Fig. 1b.

[0040] The essential difference is that here the connecting wire or connecting bolt 45 is designed as a turned copper part, through which the opening 47 is pierced to facilitate the insertion of electrically insulating material 42 into the opening 46. The connecting wire or connecting bolt 45 engages in the opening 46 only with an end section 45a, in which its cross-section is reduced; its outer diameter is adapted to the outer diameter of the electrical heating element 44.

[0041] The description of the preceding embodiments should have made it clear that the insertion of electrically insulating material into the opening in the resistance wire forming the electric heating element is not easily and reliably implemented. These problems can be solved, in particular, by pre-configuring an assembly before inserting the electric heating element into the interior of the tubular metal sheath, as described in the Fig. 5a to 5c are shown.

[0042] Fig. Figure 5a shows the components of the assembly 150, namely the electric heating element 154, which is again tubular with an opening 56 passing through the resistance wire from which the electric heating element 154 is formed from end face to end face, a rod 158 made of electrically insulating, thermally conductive material, which can be made of magnesium oxide, for example, and whose outer diameter is adapted to the cross-section of the opening 56, as well as two tubular connecting wires or connecting bolts 155, 157 made of electrically conductive material, for example nickel or copper, which are also each passed through from end face to end face by an opening whose cross-section is adapted to the cross-section of the opening 56 of the electric heating element 154.

[0043] The electric heating element 154 can now simply be threaded onto the rod 158, as shown in Fig. 5b is shown and then assembly 150, which is in Fig. The assembly, which is fully illustrated in section 5c, is completed by threading the connecting bolts 155 and 157 onto the rod 158 from different sides and bringing them into end-face contact with the electric heating element 154. This contact can also be secured, for example by soldering or welding.

[0044] The assembly 150 then only needs to be positioned inside the tubular metal casing, insulated by surrounding it with electrically insulating material and optionally compacted to produce the electric tubular heater.

[0045] Fig. 6a and Fig. Figure 6b shows how this procedure can be advantageously applied to electric tubular heating elements whose tubular metal sheath forms the return conductor. The connecting wire or connecting bolt 157 made of Fig. 5a to 5c is replaced by a connecting wire or connecting bolt 167 with a blind hole bore, the cross-section of which is adapted to the cross-section of the rod 168, the rod 168 with an electrical heating element 164 arranged on it is inserted into the blind hole bore and the end-face electrical contact between connecting wire or connecting bolt 167 and electrical heating element 164 is established.

[0046] The Fig. 7a and Fig. 7b or 8a and Fig. Figure 8b further illustrates that the openings introduced into the electrical heating elements can also separate them, as in the case of electrical heating element 174, in which the tube has a side wall that is open throughout in the direction of extension, or divide them, as in the case of electrical heating element 184, which is composed of segments 184a and 184b. The embodiment according to Fig. 7a, Fig. 7b can also be obtained by rolling up a (flat) strip-shaped heating element blank.

[0047] In the embodiment described in the Fig. 8a and Fig. In contrast, as shown in Figure 8b, the resistance wire forming the electrical heating element 184 is penetrated lengthwise from one terminal end face to the opposite terminal end face by an opening. This opening, in addition to a central circular cross-sectional area arranged coaxially with the resistance wire and having a smaller diameter than the resistance wire, has two opposing, annular sector-like cross-sectional areas. These areas divide the remaining tube after the insertion of the central cross-sectional area lengthwise into the two hemispherical segments 184a and 184b. This makes the insertion of electrically insulating material particularly easy and results in a further desired increase in resistance. For contacting or pre-configuring an assembly, for example, an electrical welding contact can be connected to the narrow sides of a terminal bolt with a rectangular cross-section, as shown in Figure 8b. Fig. 3a and Fig. 3b is dough, produce.

[0048] While the electrical heating element 174 is still pushed onto a rod 178 to form a stable arrangement, when configuring an assembly, the segments 184a and 184b are held by making a mechanically supporting contact to the connecting wire or connecting bolt (not shown).

[0049] The Fig. 9a, Fig. 9b, Fig. 10a, Fig. 10b, Fig. 11 and Fig. Figure 12 shows electrical heating elements 114, 124, 134, 144, in which a local adjustment of the resistance is achieved—partially additionally—by incorporating a contoured surface 110, 120, 130, 140 into the resistance wire that forms the electrical heating element. In the Fig. 9a and Fig. In the electrical heating element 114 shown in 9b, two grooves 118 are milled to form the contoured surface 110, thereby causing a local increase in resistance.

[0050] The electric heating element 124, which is located in the Fig. 10a and Fig. As shown in Figure 10b, a tapered section 128 is incorporated to form the contoured surface 120. A tube 126 is pressed onto the contoured surface 120. If a highly conductive material such as copper is selected for the tube 126, a local reduction in resistance can be achieved in this way.

[0051] The electric heating element 134, which is located in the Fig. As shown in Figure 11, the power matching is achieved by cutouts in the resistance wire, which can be made into the material, for example, by laser, by punching or by water jet cutting, to form the contoured surface 130.

[0052] For the electric heating element 144 according to Fig. 12 a helix 148 is introduced into the surface of the resistance wire with a laser to form the contoured surface 140.

[0053] The in Fig. Figure 13 shows an electric tubular heating element 50 with a tubular metal jacket 51, electrically insulating material 52, an electric heating element 54 with an opening 56 and connecting wires or connecting bolts 55, 57 with openings 55a, 57a passing through the connecting bolts 55, 57, which differs from the one shown in Fig. 4a and Fig. The electric tubular heating element 40 shown in Figure 4b is distinguished not only by the fact that it is designed for electrical connection at both ends and therefore does not use the tubular metal sheath 51 as a return conductor, but primarily by the fact that the electric heating element 54, with its longitudinally penetrating opening 56, has a contoured circumferential surface. This is achieved here by giving the resistance wire a corrugated shape. This measure results in an electric heating element that can compensate for changes in length during temperature fluctuations significantly better than is the case with straight electric heating elements.

[0054] Two further embodiments of electric tubular heating elements 60, 70 are now described using the Fig. 14a, Fig. 14b, Fig. 14c, Fig. 15a and Fig. 15b presented.

[0055] Fig. Figure 14a shows an exploded view (in which, however, the electrically insulating material 62 is not shown) of an electric tubular heating element 60 and Fig. 15a a longitudinal section through this electric tubular heater 60. The construction of the electric tubular heater 60 with tubular metal sheath 61, electrically insulating material 62, electric heating element 64 with opening 66 and connecting wires or connecting bolts 65, 67 with openings 65a, 67a passing through the connecting bolts 65, 67 is essentially identical to that of the electric tubular heater 50 made of Fig. 13 with the difference that here the electric heating element 64 is a tubular, preferably self-supporting, i.e., non-deforming resistance wire under its own weight. This embodiment illustrates in particular that an assembly of connecting wires or connecting bolts 65, 67 and electric heating element 64 can also be pre-configured and inserted into the interior of the tubular metal sheath 61 even if one decides against the use of a rod made of electrically insulating material, as described above, for example, in connection with the Fig. 5a and Fig. 5b was explained, I would like to decide.

[0056] The Fig. 14b and Fig. Figure 14c shows variants of connecting wires or connecting bolts 75, 77, which can be used as an alternative to the connecting wires or connecting bolts 65, 67. Fig. Figure 15b shows an electric tubular heater 70 with such connecting bolts 75, 77. Otherwise, the construction of the electric tubular heater 70 with tubular metal sheath 71, electrically insulating material 72, electric heating element 74 with opening 76 and connecting wires or connecting bolts 75, 77 is essentially identical to that of the electric tubular heater 60 made of Fig. 15a.

[0057] Fig. Figure 16a shows an exploded view (in which, however, the electrically insulating material 82 is not shown) of an electric tubular heating element 80 and Fig. 16b a longitudinal section through this electric tubular heater 80. The construction of the electric tubular heater 80 with tubular metal sheath 81, electrically insulating material 82, electric heating element 84 with opening 86 and connecting wires or connecting bolts 85, 87 with opening 87a passing through the connecting bolts 85, 87 is similar to that of the electric tubular heater 60 made of Fig. 14a and Fig. 15a.

[0058] A very important difference, however, lies in the fact that here the electrical heating element 84 is a tubular, preferably self-supporting, i.e., non-deforming resistance wire, into which a helical groove 88 has been additionally cut section by section. Besides local resistance modification, this provides a means of compensating for changes in length due to temperature fluctuations, which is particularly easier to implement in small designs than the embodiment according to [reference to embodiment]. Fig. 13. As in Fig. As shown schematically in 16f, the helical groove 88, which penetrates the tube wall, is simply cut into a tubular resistance wire, for example with a laser 89.

[0059] Even in this embodiment, it is possible that, as in Fig. As shown in Figure 16e, an assembly consisting of connecting wires or connecting bolts 85, 87 and an electrical heating element 84 can be pre-configured and inserted into the interior of the tubular metal sheath 81, even if connecting bolts 85, 87 and electrical heating element 84 are not to be soldered or welded together, but rather the electrical contact is to be made by press contact.

[0060] The Fig. Figure 16c shows a variant of a connecting wire or connecting bolt 95, which can be used as an alternative to the connecting wires or connecting bolts 85, 87. The connecting bolt 95 is characterized by the fact that its opening 95a is supported from the inside by cross-shaped reinforcing ribs 99. This can be crucial, especially in small designs, when a press connection is to be made, in preventing unwanted deformation of this area.

[0061] Fig. Figure 16d shows an electric tubular heating element 90 with tubular metal and connecting bolts 95, 97. Otherwise, the construction of the electric tubular heating element 90, with tubular metal sheath 91, electrically insulating material 92, electric heating element 94 with opening 96 and connecting wires or connecting bolts 95, 97, is essentially identical to that of the electric tubular heating element 80. Fig. 16b.

[0062] The Fig. Figures 17a to 17g further illustrate the multitude of design freedoms regarding the form and arrangement of the tubular metal casing 211, 221, 231, 241, 251, 261, 271 and of an opening running lengthwise, which is shown in the cross-sectional representations of the Fig. 17a to 17e is not recognizable because it is filled with electrically insulating material 212,222,232,242,252,262,272 and an electrical heating element (214,224,234,244,254,264,274) which provides the assembly principle according to the invention.

[0063] Firstly, it can be seen that the cross-section of the tubular metal casing 211,221,231,241, 251,261,271 can be selected as round, rectangular, square or rectangular with rounded corners, of course oval or elliptical cross-sections can be selected just as well.

[0064] Secondly, it can be seen that, depending on the cross-section of the opening passing lengthwise through the resistance wire through which the electric heating element 214,224, 234,244,254,264,274 is formed, in addition to tubular electric heating elements 214, segment-like electric heating elements 224,234, electric heating elements with a split tube wall 242,252 or even self-overlapping electric heating elements 264,274 can be formed.

[0065] Thirdly, this group of figures illustrates that the electrical heating elements with openings shown can each be obtained by rolling, bending or folding, in particular of (flat) strip-like or plate-shaped heating element blanks, i.e. by global forming. Reference symbol list 10, 20, 30, 40, 50, 60, 70, 80, 90 Electric tubular heating element 11, 21, 31, 41, 51, 61, 71, 81, 91 tubular metal casing 12, 22, 32, 42, 52, 62, 72, 82, 92 electrically insulating material 13.43 floor 14, 24, 34, 44, 54, 64, 74, 84, 94, 114, 124, 134, 144, 154, 164, 174, 184 electric heating element 15, 25, 27, 35, 37, 45, 55, 57, 65, 67, 75, 77, 85, 87, 95, 97, 155, 157, 165, 167 Connecting wire or connecting bolt 16, 26, 36, 46, 56, 66, 76, 86, 96 Opening 28 more openings 34a,34b Half-shell 47, 55a, 57a, 65a, 67a Opening 77a,118 Nut 88.98 helical groove 89 Laser 99 cross-shaped reinforcing ribs 110, 120, 130, 140 contoured perimeter area 126 Ring 128 In-depth study 138 Exclusion 148 helix 150,160 assembly 158, 168, 178, 188 Rod made of electrically insulating material 184a,184b Segment 211, 221, 231, 241, 251, 261, 271 tubular metal casing 212,222,223,242,252,262,272 electrically insulating material 214,224,234,244,254,264,274 electric heating element

Claims

[1] Method for manufacturing an electric tubular heating element (10,20,30,40,50,60,70,80,90) comprising the steps - Including at least one opening (16, 26, 36, 46, 56, 66, 76, 86, 96) through a resistance wire and / or contouring the circumferential surface of a resistance wire (110, 120, 130, 140) to provide an electrical heating element (14, 24, 34, 44, 54, 64, 74, 84, 94, 114, 124, 134, 144, 154, 164, 174, 184), - Arranging the electric heating element (14, 24, 34, 44, 54, 64, 74, 84, 94, 114, 124, 134, 144, 154, 164, 174, 184) inside a tubular metal sheath (11, 21, 31, 41, 51, 61, 71, 81, 91), and - Electrical insulation of at least sections of the electric heating element (14, 24, 34, 44, 54, 64, 74, 84, 94, 114, 124, 134, 144, 154, 164, 174, 184) relative to the tubular metal sheath (11, 21, 31, 41, 51, 61, 71, 81, 91), wherein at least one opening (16, 26, 36, 46, 56, 66, 76, 86, 96) passing through the resistance wire is filled with an electrically insulating material (12, 22, 32, 42, 52, 62, 72, 82, 92, 158, 168, 178) after the electric heating element (14, 24, 34, 44, 54, 64, 74, 84, 94, 114,124,134,144,154,164,174,184) the filling of the opening (16,26,36,46,56,66,76,86,96) through which the resistance wire passes with an electrically insulating material by inserting a rod (158,168,178,188) made of the electrically insulating material into the opening (16,26,36,46,56,66,76,86,96) through which the resistance wire passes, and in which the electrical heating element (14,24,34,44,54,64,74,84,94,114,124,134,154,164,174,184) with at least one connecting wire or connecting bolt (15,25,27,35,37,45,55,57,65,67,75,77,85,87, 95,97,155,157,165,167) at least one unheated area of ​​the electric tubular heater (10,20,30,40,50,60,70,80, 90) is generated, characterized by , that the rod (158, 168, 178, 188) made of electrically insulating material is inserted into a through or blind opening in the connecting wire or connecting bolt (15, 25, 27, 35, 37, 45, 55, 57, 65, 67, 75, 77, 85, 87, 95, 97, 155, 157, 165, 167), the cross-section of which is adapted to the cross-section of the opening (16, 26, 36, 46, 56, 66, 76, 86, 96) provided in the resistance wire, until the opposing end faces of the connecting wire or connecting bolt (15, 25, 27, 35, 37, 45, 55, 57, 65, 67, 75, 77, 85, 87, 95, 97, 155, 157, 165, 167) and the electrical heating elements (14,24, 34,44,54,64,74,84,94,114,124,134,144,154,164,174,184) are in contact with each other. [2] Method according to claim 1, wherein the assembly (150, 160) consisting of an electric heating element (14, 24, 34, 44, 54, 64, 74, 84, 94, 114, 124, 134, 144, 154, 164, 174, 184) is arranged in the interior of a tubular metal sheath (11, 21, 31, 41, 51, 61, 71, 81, 91), an electrically insulating rod (158, 168, 178, 188) and connecting wires or connecting bolts (15, 25, 27, 35, 37, 45) is used to arrange the electric heating element (14, 24, 34, 44, 54, 64, 74, 84, 94, 114, 124, 134, 144, 154, 164, 174, 184) in the interior of a tubular metal sheath (11, 21, 31, 41, 51, 61, 71, 81, 91). 55,57,65,67,75,77,85,87,95,97,155,157,165,167) is inserted into the tubular metal sheath (11,21,31,41,51,61,71,81,91).

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