阅读说明：本技术 制造电加热装置和/或负载电阻器的电加热元件的方法 (Method for producing an electric heating element of an electric heating device and/or load resistor ) 是由 A·施利普夫 于 2020-10-15 设计创作，主要内容包括：本发明提供一种用于制造电加热元件的方法,所述方法特别地用于电加热装置和负载电阻器,所述方法具有如下步骤：-设定至少一个加热导体径迹,-提供具有几何尺寸的加热元件坯件,所述几何尺寸选择成使得所设定的加热导体径迹可以布置在加热元件坯件材料所占据空间的部分体积中,以及-加工加热元件坯件,以通过从加热元件坯件中去除材料来产生经设定的加热导体径迹。(The invention provides a method for producing an electric heating element, in particular for an electric heating device and a load resistor, having the following steps: -setting at least one heating conductor track, -providing a heating element blank having a geometry selected such that the set heating conductor track can be arranged in a partial volume of the space occupied by the heating element blank material, and-machining the heating element blank to produce the set heating conductor track by removing material from the heating element blank.)

1. A method for manufacturing an electric heating element (10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 210, 220), in particular for an electric heating device and a load resistor, the method having the steps of:

-setting at least one heating conductor track (64, 84, 94, 104, 134, 154, 164, 174, 184, 194, 204, 214),

-providing a heating element blank (11, 21, 31, 41, 51, 61, 71, 81, 91, 101, 111, 121, 131, 141, 151, 161, 171, 181, 191, 201, 211, 221) with geometrical dimensions selected such that a set heating conductor track (64, 84, 94, 104, 134, 154, 164, 174, 184, 194, 204, 214, 204, 214) can be arranged in a partial volume of the space occupied by the heating element blank material (11, 21, 31, 41, 51, 61, 71, 81, 91, 101, 111, 121, 131, 141, 151, 161, 171, 181, 191, 201, 211, 221), and

-processing the heating element blank (11, 21, 31, 41, 51, 61, 71, 81, 91, 101, 111, 121, 131, 141, 151, 161, 171, 181, 191, 201, 211, 221, 221) to produce a set heating conductor track (64, 84, 94, 104, 134, 154, 164, 174, 184, 194, 204, 214) by removing material from the heating element blank (11, 21, 21, 31, 41, 51, 61, 71, 81, 91, 101, 111, 121, 131, 141, 151, 161, 171, 181, 191, 201, 211, 221).

2. Method according to claim 1, characterized in that the machining is carried out in a cutting manner by laser machining, by waterjet cutting, by stamping, by fine stamping or by etching, wherein the laser machining can in particular be realized by fine laser cutting, wherein the waterjet cutting can in particular be realized by fine waterjet cutting.

3. Method according to any one of claims 1 or 2, characterized in that a heating element blank (11, 21, 31, 41, 51, 61, 71, 81, 91, 101, 111, 121, 131, 141, 151, 161, 171, 181, 191, 201, 211, 221, 221) is provided, which is plate-shaped, cuboid, cylindrical or tubular.

4. A method according to any one of claims 1 to 3, characterized by providing a heating element blank (11, 21, 31, 41, 51, 61, 71, 81, 91, 101, 111, 121, 131, 141, 151, 161, 171, 181, 191, 201, 211, 221, 221) having portions and/or layers made of or comprising different materials.

5. Method according to any one of claims 1 to 4, characterized in that a heating element blank (11, 21, 31, 41, 51, 61, 71, 81, 91, 101, 111, 121, 131, 141, 151, 161, 171, 181, 191, 201, 211, 221, 221) is provided having the at least one portion, at least one region or at least one layer made of a resistive alloy, the temperature coefficient of the at least one portion, at least one region or at least one layer being >300ppm, preferably >1000ppm, particularly preferably >3000 ppm.

6. Method according to any one of claims 1 to 5, characterized in that a heating element blank (11, 21, 31, 41, 51, 61, 71, 81, 91, 101, 111, 121, 131, 141, 151, 161, 171, 181, 191, 201, 211, 221) is provided, which heating element blank has portions of different thickness.

7. Method according to any of claims 1 to 6, characterized in that the heating conductor tracks (64, 84, 94, 104, 134, 154, 164, 174, 184, 194, 204, 214) are set such that they extend in a plane.

8. Method according to one of claims 1 to 7, characterized in that the heating conductor tracks (64, 84, 94, 104, 134, 154, 164, 174, 184, 194, 204, 214) are set to emerge from the final heating conductor track (64, 84, 94, 104, 134, 154, 164, 174, 184, 194, 204, 214) by means of a global geometric deformation, in particular by being rolled or unrolled, and the processed heating element blank (11, 21, 31, 41, 51, 61, 71, 81, 91, 101, 111, 121, 131, 141, 151, 161, 171, 181, 191, 201, 211, 221) is subjected to a reverse geometric deformation, in particular by rolling or folding the electric heating element (10, 20, 30, 40, 5060, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 210, 220) to be converted into a heating conductor track with the final heating conductor track (64, 84, 94, 104, 134, 154, 164, 174, 184, 194, 204, 214, 214).

9. Method according to any of claims 1 to 8, characterized in that the heating conductor tracks (64, 84, 94, 104, 134, 154, 164, 174, 184, 194, 204, 214) are set with sections of different widths, so that they widen or narrow locally.

10. Method according to any of claims 1 to 9, characterized in that the heating conductor tracks (64, 84, 94, 104, 134, 154, 164, 174, 184, 194, 204, 214) are set to sections with different thicknesses.

11. Method according to one of claims 1 to 10, characterized in that the heating conductor tracks (64, 84, 94, 104, 134, 154, 164, 174, 184, 194, 204, 214) are set to extend in a segmented spiral, wherein the pitch varies.

12. Method according to one of claims 1 to 11, characterized in that the heating conductor tracks (64, 84, 94, 104, 134, 154, 164, 174, 184, 194, 204, 214) are set to extend in a segmented spiral, wherein the direction of rotation of the spiral changes.

13. Method according to any of claims 1 to 12, characterized in that the heating conductor tracks (64, 84, 94, 104, 134, 154, 164, 174, 184, 194, 204, 214) are set with contact surfaces for electrical contacting or connecting.

14. Method according to any of claims 1 to 13, characterized in that the heating conductor track is configured with at least one series-connected local heating conductor track (34, 35, 44, 45, 54, 55, 56, 214) and/or at least one parallel-connected local heating conductor track (34, 35, 44, 45, 54, 55, 56, 214).

15. Method according to one of claims 1 to 14, characterized in that the heating conductor track (64, 84, 94, 104, 134, 154, 164, 174, 184, 194, 204, 214) is configured with at least two mutually separated heating circuits.

16. Method according to any of claims 1 to 15, characterized in that the heating conductor tracks (64, 84, 94, 104, 134, 154, 164, 174, 184, 194, 204, 214) are set with sections that can be switched separately from each other.

17. Method according to any of claims 1 to 15, characterized in that the heating conductor track (64, 84, 94, 104, 134, 154, 164, 174, 184, 194, 204, 214) is set to have at least one double-line section.

18. The method according to any of claims 1 to 17, characterized in that the heating conductor tracks (64, 84, 94, 104, 134, 154, 164, 174, 184, 194, 204, 214) are set to counteract the mechanical effect of thermal load variations.

Technical Field

The present invention relates to a method of manufacturing an electric heating element of an electric heating device and/or a load resistor.

Background

Up to now, electrical heating elements (in particular cartridge heaters, tubular heaters, hollow boxes, planar heaters and surface heaters) and/or load resistors for electrical heating devices, with which electrical energy is converted into heat, are usually made by providing heating conductor material in the form of wires, which are then (as long as the wires are not stretched in use) bent, wound or coiled freely on a support or in a space curve to produce the desired heating conductor tracks, by means of which the desired heat distribution can be achieved, or by means of which heat dissipation can be achieved.

In addition to the problem of not being able to generate all the envisaged or required spatial profiles in this way, there is a particular problem in the construction in which it is necessary to install smaller heating conductor resistors with a higher heating conductor cross section in a narrow space, so that, on the one hand, in particular long heat exchange loads can be withstood and, on the other hand, in particular the process reliably connects the unheated and heated regions of the electric heating device to one another, which is necessary, in particular, at very high current loads.

Disclosure of Invention

It is therefore an object of the present invention to provide a low cost method for producing an electric heating element, which method is suitable for at least reducing the above mentioned problems. This object is achieved by a method for producing an electric heating element having the features of claim 1. Advantageous developments of the invention are the subject matter of the respective dependent claims.

The method according to the invention for producing an electric heating element is particularly suitable for an electric heating device and a heating element of a load resistor, having the following steps

-setting at least one heating conductor track;

-providing a heating element blank of a geometry selected such that the heating conductor tracks set can be arranged in a partial volume of the space occupied by the material of the heating element blank, and

-machining the heating element blank so as to produce the set heating conductor track by removing material from the heating element blank.

By these means, it is possible to mould the heating conductor tracks from the heating element blank (which does not exclude the possibility of their later overall deformation), instead of producing the conductors by deforming the heating conductors, which are usually provided in the form of wires or strips, as is currently usual. The method according to the invention has a number of important advantages:

firstly, the invention can be easily carried out in full automation, which brings cost advantages, but also brings higher process reliability and repeatability, and reduces the rejection rate, thereby having a positive impact on mass production. These effects also compensate for the increase in the amount of material used, particularly because the material removed during the manufacturing process can be easily recycled, although a process with an increased amount of material may initially appear unsuitable.

Secondly, for various reasons, the method exploits the geometry of the heating conductor tracks that was previously difficult to achieve for various reasons. For example, it has proven practically impossible to wind a strip-shaped heating conductor with a large cross-section into a structure with a small radius and a large curvature, so that the resulting electric heating element has a small diameter. It is also not possible to wind wide strips with a large pitch or to achieve complex heating conductor track geometries, e.g. nested one within the other.

Possible machining techniques that can be used are in particular cutting machining, laser machining (in particular fine laser cutting), water jet cutting (in particular fine water jet cutting), stamping and (in particular for relatively fine (filigranen) heating element blanks) fine stamping or etching.

The heating element blank provided may have essentially any shape, as long as the heating element tracks provided can be written (eingeschrieben) into the volume defined by the shape, which is a prerequisite for the ability of the heating element tracks to be fashioned from such a heating element blank, in particular the heating conductor tracks provided can be arranged in a partial volume of the space occupied by the material of the heating element blank.

In practice, however, in most cases the heating element blank has a simple basic geometry, in particular a rectangular parallelepiped, (full) cylindrical or tubular basic geometry, and can also be provided by separating a section of suitable length from a strip of material having a corresponding cross-section. In many cases, these simple basic geometries of heating element blanks are preferred because they are easy to handle and are available at low cost.

However, the easy and inexpensive availability of heating element blanks is not the only valid standard for using heating element blanks. For example, it may be advantageous if a heating element blank is provided having portions and/or layers composed of or comprising different materials. For example, it is expedient in an advantageous variant for the heating element blank to have a layer made of a heating element alloy and a layer made of copper, for example in the form of a composite tube or a two-layer plate, in order to realize a heating conductor track with unheated portions. When the copper layer is removed in the heated portion in the processing step, the copper layer remains in the unheated portion, which then greatly reduces the electrical resistance in the unheated portion, so that there is little heat output. In particular in the case of complex heating conductor tracks, it is possible to arrange unheated zones which were not possible before.

In an advantageous development of the invention, the electric heating element can be controlled and/or temperature-monitored if a heating element blank is provided which has at least one section, at least one region or at least one layer made of an electrically resistive alloy with a temperature coefficient of >300ppm, preferably >1000ppm, particularly preferably >3000 ppm.

Another criterion that may influence the selection of heating element blanks for a given heating conductor track is that subsequent processing steps may be carried out significantly faster and/or easier, if necessary, by selecting a suitable geometry for the blanks. For example, if heating element blanks with sections of different thicknesses are provided, it is possible in some cases to realize heating conductor tracks with heating conductors of different cross-sections by means of a simple stamping step, which otherwise have to be produced by selective thinning of the heating conductor (ausdunen) in order to adjust the cross-section. Heating element blanks having portions of different thicknesses may also be manufactured from heating element blanks having a simpler basic geometry, for example by grinding or milling in specific areas.

If the heating conductor track is set to extend in a plane (eben)) It is then particularly easy to carry out various treatment methods for realizing the set heating conductor tracks by machining the heating element blank.

One possibility (not limited to a planar heating conductor track as target geometry) for achieving this is to set the heating conductor track such that it is produced by geometric deformation of the whole, in particular by unrolling or unrolling of the final heating conductor track, and the finished heating element blank is subjected to a reverse geometric deformation, in particular by rolling or folding, in order to form the electric heating element into the shape of the final heating conductor track.

An advantageous variant of the defined heating conductor track provides that the heating conductor track is defined as having portions of different widths, so as to be locally widened or narrowed. This results in a cross-sectional variation which causes a local resistance variation in the respective section and thus a local variation in the temperature profile of the respective electrical heating element. Alternatively or additionally, this effect can also be achieved by setting the heating conductor tracks to have portions of different thickness.

Another possibility for influencing the temperature profile of the electric heating element is to set the heating conductor track to extend in a segmented spiral, wherein the pitch changes.

The heating conductor tracks can also be configured to extend in a segmented spiral, the direction of rotation of the spiral changing.

A further great advantage of the electric heating element produced by the method according to the invention is that a highly process-reliable contacting can be achieved. This is especially true when the heating conductor tracks are set with contact surfaces for electrical contacts or connections. These contact surfaces or connections are thus part of the electrical heating element itself, not an intermediate element through which contact is made.

In the first mentioned variant, the problem of local contact can be eliminated by providing an enlarged contact surface, while in the second mentioned variant the connection creates a defined contact condition so that no additional contact points between the connection and the electric heating element occur compared to previous connection applications.

In an advantageous development, the method according to the invention can also be used to configure the heating conductor tracks with at least one series-connected partial heating conductor track and/or at least one parallel-connected partial heating conductor track. Such local heating conductor tracks can also be configured to be switchable, i.e. can be controlled or operated separately from one another. The heating conductor can also be advantageously configured with at least two heating circuits separated from each other.

All this clearly shows that the manufacturing method according to the invention results in a greatly improved complex functionality of the electric heating element.

In a further advantageous embodiment of the method, the heating conductor track is configured with at least one bifilar (bifilaren) section. In this way, in particular, inductive effects can be reduced.

Furthermore, the mechanical effect of the thermal load variation can be prevented by appropriately setting the heating conductor tracks.

Drawings

The invention is explained in more detail below with reference to the drawings showing embodiments. It shows that:

FIG. 1 a: an external view of a first example of an electric heating element,

FIG. 1 b: the view of figure 1a with the electric heating element in a partially open state,

FIG. 2 a: an external view of a second example of an electric heating element,

FIG. 2 b: the view of figure 2a shows the electric heating element in a partially open state,

FIG. 3 a: an external view of a fourth example of an electric heating element,

FIG. 3 b: a plan view of the electric heating element in figure 3a,

FIG. 3 c: the external view of the electric heating element in figure 3a is in a rolled-up state,

FIG. 3 d: the side view of the electric heating element in figure 3a in the rolled-up state in figure 3,

FIG. 3 e: schematic representation of the overall geometrical deformation, which transforms the heating conductor tracks of figures 3a and 3b into the heating conductor tracks of figures 3c and 3d,

FIG. 4 a: an external view of a fourth example of an electric heating element,

FIG. 4 b: the plan view of the electric heating element in figure 4a,

FIG. 4 c: an external view of the electric heating element in figure 4a in a rolled-up state,

FIG. 5 a: an external view of a fifth example of an electric heating element,

FIG. 5 b: the side view of the electric heating element in figure 5a,

FIG. 5 c: in the mounted condition of the electric heating element of figure 5a,

FIG. 6 a: an external view of a sixth example of an electric heating element,

FIG. 6 b: the electric heating element in figure 6a in the mounted condition,

FIG. 7 a: an external view of a seventh example of an electric heating element,

FIG. 7 b: the deformed electric heating element in figure 7a in the mounted state,

FIG. 7 c: schematic representation of the overall geometrical deformation transforming the electric heating element, in particular the heating conductor track, of fig. 7a into the electric heating element, in particular the heating conductor track, of fig. 7b,

FIG. 8 a: an exterior view of an eighth example of an electric heating element,

FIG. 8 b: figure 8a is a plan view of the electric heating element,

FIG. 8 c: figure 8a is an external view of the state in which the electric heating element is rolled into a circle,

FIG. 8 d: an external view of the electric heating element of figure 8a in a square folded state,

FIG. 8 e: an external view of the electric heating element of figure 8a rolled into a spiral,

FIG. 8 f: an external view of the electric heating element of figure 8a rolled into a semi-circular shape,

FIG. 9: an external view of a ninth example of an electric heating element,

FIG. 10: an external view of a tenth example of an electric heating element,

FIG. 11 a: an exterior view of an eleventh example of an electric heating element,

FIG. 11 b: the longitudinal cross-section of the electric heating element in figure 11a,

FIG. 12 a: an exterior view of a twelfth example of an electrical heating element,

FIG. 12 b: figure 12a is a side view of the electric heating element,

FIG. 13 a: an exploded view of the components of an electric heating device with a tubular metal sheath as return conductor,

FIG. 13 b: a view of a partially opened electric heating device assembled from the parts shown in figure 13a,

FIG. 14: a fourteenth example of an electric heating element with an integrated connection portion,

FIG. 15 a: a fifteenth example of an electrical heating element,

FIG. 15 b: a machined heating element blank, from which the electric heating element of figure 15a is produced,

FIG. 16 a: a sixteenth example of an electrical heating element,

FIG. 16 b: a machined heating element blank, from which the electric heating element of figure 16a is produced,

FIG. 17: a seventeenth example of an electric heating element,

FIG. 18: an eighteenth example of an electric heating element,

FIG. 19 a: an external view of a nineteenth example of an electric heating element,

FIG. 19 b: figure 19a is a side view of the electric heating element,

FIG. 19 c: figure 19a is a schematic representation of the reaction of an electric heating element to a tensile load,

FIG. 19 d: FIG. 19a is a schematic illustration of the reaction of an electric heating element to a pressure load;

FIG. 20 a: a twentieth example of an electric heating element,

FIG. 20 b: a machined heating element blank from which the electrical heating element in figure 20a is produced,

FIG. 21: a twenty-first example of an electric heating element in the mounted condition,

FIG. 22: a twenty-second example of an electric heating element in the first installation situation,

FIG. 23: a twenty-second example of an electric heating element in a second installation situation,

FIG. 24: a variant of the twenty-second example of an electric heating element in the installed condition, and

FIG. 25: another variant of the twenty-second example of the electric heating element in the mounted condition.

Detailed Description

The electric heating element 10 shown in fig. 1a and 1b is made from a tubular heating element blank 11, but may also be made from a cylindrical heating element blank in which a central hole is subsequently formed.

Thus, the space initially occupied by the material of tubular heating element blank 11 is defined by the space occupied by its sleeve. An electric heating element 10 is obtained from the tubular heating element blank 11, in which sleeve a recess 12 is formed through the sleeve by removing material from the sleeve. Thus, heating conductor tracks are formed in a partial volume of the space initially occupied by the material of the heating element blank 11.

The introduced grooves 12 have the shape of a helix, which in the embodiment described has a different pitch in their middle portion 12b than in their end portions 12a, 12 c. By means of the groove 12 through the jacket tube, a heating conductor track is formed with a spiral 13, the cross section 14b of which, because of its greater width, is greater in the middle part 12b of the groove 12 than in the end parts 12a, 12c of the groove 12. The region of the middle portion 12b of the groove 12 therefore emits a lower heating power.

It should also be noted that the tubular shape of the heating element blank 11 at both ends of the heating element 10 is held such that the heating element tracks on these ends of the heating element 10 have large-area contact surfaces 15a, 15b formed by the inner wall of the tube, by means of which contact surfaces contact can be made with the connecting bolts (not shown) in a technically reliable manner, for example as a pressure contact. Obviously, such contact surfaces 15a, 15b of the heating element 10 can be found in a similar manner in the embodiments described below, even if not always explicitly mentioned.

The electric heating element 20 shown in fig. 2a and 2b is also made of a tubular heating element blank 21. The electric heating element 20 can also be obtained from the tubular heating element blank 21 by removing material from the tube sleeve to form a recess 22 in the tube sleeve through the tube sleeve.

The introduced grooves 22 have the shape of a helix, however in the embodiment described the grooves have a different pitch and width in their middle portion 22b than in their end portions 22a, 22 c. By passing through the groove 22 of the sleeve, a heating conductor 23 is formed with a spiral, the spiral pitch W in the middle part 22b of the groove 22 being greater than in the ends 22a, 22c of the groove 12 due to the greater width. The intermediate portion 22b of the groove 22 emits a lower thermal power, but the resulting temperature profile is different from the embodiment of fig. 1a, 1 b.

In principle, the electric heating element 30 shown in fig. 3c and 3d can also be machined from a tubular heating element blank, but is much easier to manufacture from a plate-shaped heating element blank 31, which is then rolled up according to the overall deformation sketched in fig. 3 e. In this case, the heating conductor tracks can be introduced into the plate-shaped heating element blank 31, in particular by stamping. In this way a first local heating conductor track 34 and a second local heating conductor track 35 are formed in the heating conductor, which are connected in series with each other. The first local heating conductor 34 first runs in a curved manner on the jacket tube of the heating element blank 31, leaving a space between the respective reversal sections 34a, 34b of the curved circuit, through which the connecting section 35d of the second local heating conductor 35 is guided in a straight line. In addition, the tortuous circuit in section 34c is designed to have a larger cross-section.

The first local heating conductor 34 merges into a connecting portion 34d at approximately half the length of the heating element blank 31. In this region, the second partial heating conductor track 35 extends in a curved manner on the jacket of the heating element blank 31, whereas the position of the curved loop of the second partial heating conductor track 35 on the jacket is offset by 90 degrees compared to the position of the curved loop of the first partial heating conductor track 34 on the jacket, the connecting portion 34d of the first partial heating conductor 34 being located in the space between the respective reversal portions 35a, 35b of the curved loop. Furthermore, there is a section 35c, in which the cross section of the bending loop is enlarged.

Since the amount of heat generated in the straight connecting portions 34c, 35c is less than that generated in the bent loops, the electric heating element 30 has two portions over its entire length, each portion having anisotropic heat dissipation characteristics with respect to the tube axis, which characteristics also vary over the entire length, with directions offset or rotated by 90 ° with respect to each other. Such a relatively complex heating conductor track can thus be produced in a relatively simple manner.

The embodiment in fig. 4a to 4c shows an electric heating element 40, which may be obtained by rolling a heating element blank 41 from a sheet. The heating conductor track is formed from a plate-shaped heating element blank 41, consists of two partial heating conductors 44, 45 extending parallel with the same bending geometry, and is produced by rolling up the electric heating element 40.

The electric heating element 50 shown in fig. 5a to 5c is machined from a cylindrical tubular heating element blank 51. The heating conductor track is composed of three local heating conductor tracks 54, 55, 56 connected in series, and the pitch and the direction of the spiral rotation of each adjacent local heating conductor track 54, 55 or 55, 56 are different. Tubular connecting portions 57 are provided at both ends of the heating conductor, respectively, by whose inner surfaces a large contact surface of the contact portion 58a of the connecting bolt 58 can be engaged. Fig. 5c shows an electric heating element 50, said electric heating element 50 being a component of an electric heating device in the interior of a tubular metal sleeve 52 and being embedded in a preferably compressed electrically insulating material 53.

A twin wire heating conductor track is of interest for a variety of applications. Fig. 6a shows an electric heating element 60 in the form of a twin wire heating conductor track 64, the twin wire heating conductor track 64 being machined from a cylindrical heating element blank; fig. 6b shows an electric heating device with a tubular metal jacket 62, inside which the electric heating element 60 is embedded in an electrically insulating material 63.

As shown in fig. 7a to 7c, it is also possible to produce a two-wire weighting starting from a plate-shaped heating element blank 71, which can then be deformed integrally into an electric heating element 70 by rolling it up, which is then embedded in a tubular metal sheath 72 arranged in an electrically insulating material 73 and electrically connected to the connecting leads 78.

In fig. 8a and 8b, two views of a simple electric heating element 80 with substantially curved heating conductor tracks 84 machined from a plate-shaped heating element blank are shown. Fig. 8c to 8f show different electric heating elements 80 ', 80 "', 80", which are obtained by overall geometrical deformation, i.e. rolling up with a constant radius, folding into a square, rolling up with a variable radius into an overlapping spiral structure and bending the plate-shaped heating element blank, as is shown in the schematic view of the respective rotational deformation.

The electric heating element 90 or 100 according to fig. 9 and 10 shows a further possibility of manufacturing an electric heating element based on a plate-shaped heating element blank. If such a blank is milled in sections, the heating conductor tracks 94, 104 can be produced in a simple manner, having portions 94a, 104a of larger cross section and portions 94b, 104b of smaller cross section.

By machining the electric heating elements from the heating element blank, as shown by the electric heating elements 110 and 120 according to fig. 11a, 11b and 12a, 12b, respectively, previously inaccessible structures can be produced. As can be seen from fig. 11a and 11B, the heating element 110, which has a very high ratio of width B to height H of the spiral cross-section, can be made from a tube with a narrow tube inner diameter D1 and only a slightly larger tube outer diameter D2 by cutting a spiral groove, or as shown in fig. 12a and 12B, a "concave" heating element 120, which cannot be wound, is created.

The electric heating element 130 shown in fig. 13a and 13b is part of an electric heating device having a tubular metal sheath 132 serving as a return conductor, an electrically insulating material 133, a contact pin 135, a base washer 137 and a connecting wire 138. The heating conductor tracks 134 are formed by milling recesses in the heating area from the tubular heating element blank 131, leaving a tubular section at each end in order to form, on the one hand, a large contact surface for making electrical contact with the contact pins 135 which, via the base washers 137, make electrical contact with the tubular metal sheaths 132 serving as return conductors and, on the other hand, ensure connection with the connecting leads 138.

As shown in the example of the electric heating element 140 shown in fig. 14, for example, a connection portion for crimping with the connection wire 148 may be formed directly as an end portion of the heating element 140.

The electric heating elements based on plate-shaped heating element blanks shown so far have a high complexity of the heating conductor tracks, which is associated with, but not necessarily required for, removing a large amount of material. In practice, a large number of technically relevant conductor track arrangements can also be realized extremely economically in production by simply introducing a linearly extending slot in such a plate-shaped heating element blank and then deforming it in its entirety.

Fig. 15a and 16a are plate-shaped heating element blanks 151, 161, whose heating conductor tracks 154, 164 can be realized by arranging one or two slots 155, 165 extending substantially parallel to each other and can be rolled up to form electric heating elements 150, 160 as shown in fig. 15b or 16b, respectively.

Fig. 17 shows an electric heating element 170 which can be produced according to this principle and whose heating conductor tracks 174, as is known per se, have a substantially curved course but have to be realized at considerable expense in comparison with cutting and subsequent rolling on a plate-shaped heating element blank.

However, according to this simple principle, a new and innovative heating conductor track can also be realized. One such example is an electric heating element 180 according to fig. 18, whose heating conductor track 184 is formed by a curved path 184a, extending helically in one direction on an imaginary cylinder liner, and the return conductor portion 184b of the heating conductor 184 extending between the individual spirals.

Fig. 19a to 19d serve again to illustrate the fact that an electrical heating element which can withstand mechanical loads in an excellent manner when subjected to temperature cycling can be manufactured by means of the manufacturing principle according to the invention. The electric heating element 190 shown in fig. 19a has heating conductor tracks 194 which extend substantially through slots 196 running parallel to one another and can be introduced into a plate-shaped heating element blank or a cylindrical tubular heating element blank. The side view of fig. 19b, 19c or 19d shows the electric heating element 190 in a relaxed state, in tension or in pressure, which shows how easily the electric heating element 190 can absorb such a load.

An electric heating element with a heating conductor track having a return conductor portion can also be realized by a simple linear cut-out configuration, for example an embodiment of an electric heating element 200 with a heating conductor track 204 consisting of a bent portion 204a and a return conductor portion 204b is shown in fig. 20a and 20 b. The electric heating element 200 may be formed simply by rolling up a plate-shaped heating element blank 201, wherein on the one hand there is no comb-like cutting line 206 that completely penetrates the heating element blank in the direction of extension, and a row of incisions 207 that extend centrally in the middle of the "racks" of combs defined by the comb-like cutting lines 206, the incisions 207 emanating from the longitudinal side of the plate-shaped heating element blank 201 further away from the "rear" of the combs defined by the comb-like cutting lines 206.

Fig. 21 shows a further electric heating element 210 with a heating conductor track 214 which in its installed state has an output conductor section 214a and a return conductor section 214b as components of an electric heating device in a tubular metal sheath 212, which tubular metal sheath 212 has a base 212a embedded in an electrically insulating material 213. The heating conductor track 214 is embodied in such a way that the tubular heating element blank 211 is almost completely cut along one of its center planes to form two half-shells which are connected to one another only by a ring, and then, for example, slots 216 are cut out circumferentially from the ring, adjacent slots 216 extending over different regions in the circumferential direction in order to realize curved portions of the heating conductor track 214 in the output conductor section 214a and the return conductor section 214 b. However, these slots do not extend over the entire half shell, so that an unheated or slightly heated region of the half shell is formed on the connection side, which at the same time provides a large contact surface for the connection of the connection lines 218a, 218b, which lead through the connection-side cover 219.

Fig. 22 to 25 show that, on the basis of the very simple basic shape of the electric heating element 220, the electric heating device can be constructed in a modular manner, which allows a very inexpensive mass production of such an electric heating device. The basic shape of the electric heating element 220 may be simply obtained from a plate-like heating element blank 221, wherein parallel cuts 226 are formed alternately from the two long sides, and said parallel cuts 226 do not penetrate completely through the heating element blank. This results in a curved local heating conductor track 224 which can be used in different configurations as an integral part of the most varied heating conductor track. The electrical heating elements 220 are electrically contacted by connecting bolts 228.

Fig. 22 shows a simple variant in which such contacting electrical heating elements 220 are arranged within a tubular metal sheath 222 in an electrically insulating material 223.

Fig. 23 shows a variant in which a stack of two such electric heating elements 220 connected in parallel is arranged in electrical contact within a tubular metal sheath 222 in an electrically insulating material 223. As is readily conceivable, such a stack may also comprise further electric heating elements 220, which are held in recesses in the connecting bolts 228 and are electrically contacted, as shown in fig. 22.

In addition to a parallel connection, if the insulating elements 220 are alternately insulated on both sides, for example by inserting the electric heating elements 220 into insulating elements mounted in recesses of the connecting bolts, it is also possible to realize a series connection with an odd number of the electric heating elements 220, so that two adjacent electric heating elements 220 are in electrical contact with one another on the side of one connecting bolt 228 and are electrically insulated from one another on the side of the other connecting bolt 228, so that no direct electrical contact is made and an electric current can only flow through the respective electric heating elements.

Fig. 24 and 25 each show an embodiment of an electric heating device in which the electric heating element is bent into a U-shape, although an angled arrangement embedded in the electrically insulating material 223 and in electrical contact with the connecting bolt 228 in the metal sheath 222, 222' is also conceivable. Except that the housing 222 is a cylindrical tubular housing, while the housing 222' defines a flat heating body.

List of reference numerals

10. 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 210, 220 electrical heating element

11. 21, 31, 41, 51, 61, 71, 81, 91, 101, 111, 121, 131, 141, 151, 161, 171, 181, 191, 201, 211, 221 heating the blank

34. 35, 44, 45, 54, 55, 56, 224 locally heat the conductor tracks

64、84、94、104、134、154、164、174、184、194、204、214

The conductor tracks are heated.