EP3451791B1 - Heater and method for manufacturing same - Google Patents

Description

The invention relates to a heating device, in particular as a radiation heating device for a hob, and to a method for producing such a heating device.

From the DE 195 22 798 A1 as well as the DE 42 29 375 A1 It is known to provide a radiant heating device for a hob with a flat support made of heat-insulating and electrically insulating material, on the top of which a heating element in the form of a tape runs in strips in a laying pattern. The heating element consists of a heating conductor strip and is pressed to a small extent with a lower edge of the heating conductor strip into the upper side of the carrier for holding purposes. Furthermore, the heating conductor tape has integrally formed holding members which stand down over the lower edge and are slightly below the height of the heating conductor tape. These holding members contribute a large part to the attachment of the heating conductor tape or the heating element to the carrier. The two lateral sides of the heating conductor strip radiate heat during operation at a little over 1000 ° C, which then radiates upwards.

From the US 6,498,325 B1 an induction hob with a variety of induction heating coils emerges. Each of the induction heating coils is wound from a conductor, the cross section of which is narrow and high compared to a winding plane.

From the WO 99/09791 A1 shows a hob with radiation heating devices, each of the radiation heating devices having a heating conductor which runs on a ceramic carrier substrate. A radiation heating device can have a multilayer heating conductor, the individual layers being separated by insulating layers and lying completely on top of one another with the stacking direction away from a surface of the carrier.

Due to an electrical resistance of the heating conductor tape or heating element, maximum heating powers for such a radiant heating device are currently limited to approximately 3600W or 3700W when operated in the household. Higher heating outputs are currently not achievable with this technology.

Task and solution

The invention has for its object to provide a heating device mentioned above and a method for producing such a heating device with which problems of the prior art can be solved and in particular it is possible to generate a higher heating power compared to the prior art and to train a heating device in a new way.

This object is achieved by a heating device with the features of claim 1 and by a method for producing such a heating device with the features of claim 13. Advantageous and preferred embodiments of the invention are contained in the further claims and are described in more detail below. Some of the features are only described for the heating device or only for the method for its production. However, regardless of this, they should be able to apply independently and independently of one another both for the heating device and for the method for its production. The wording of the claims is made the content of the description by express reference.

It is provided that the heating device has a flat carrier. This can advantageously consist of heat-insulating and electrically insulating material, as is known per se from the prior art for radiant heating devices for hobs. This carrier has a carrier top, which is advantageously flat or even. A heating element is provided on this upper side of the carrier, which runs in webs in a specific laying pattern. This laying pattern can be spiral and / or meandering, as is also known per se from the prior art. For the most part, the heating element advantageously runs in parallel or almost parallel or concentric tracks.

It is provided that the heating element has at least two heating conductor strips. Each of these heating conductor strips has lateral sides and an upper edge and a lower edge. The at least two heating conductor strips are collapsed according to the invention or are placed one on top of the other or folded onto one another with their mutually facing lateral sides, wherein they touch at least partially with the mutually facing lateral sides but do not run completely against one another. Under certain circumstances, they can lie together point by point or in sections. According to the invention, the at least two heating conductor strips are firmly and permanently connected to one another, at least in the state in which they are arranged or fastened to the carrier, that is to say as a finished heating device. Are advantageous the at least two heating conductor strips of the heating element are already firmly connected to one another before being fastened to the carrier.

Due to this, so to speak, doubling of the heating element with two heating conductor strips instead of with a single heating conductor strip according to the prior art, the conductor cross section can be enlarged and thus the maximum possible current and thus the heating power generated by the heating element also increase. A duplication or multiplication of the heating conductor tape for the heating element has the great advantage over an integral and correspondingly thick heating conductor tape, which would form the heating element as the only heating conductor tape, that it is easier to manufacture, especially if the heating element is corrugated or is to be corrugated . A corrugation can take place with a wavelength between 2mm and 8mm and / or with a wave amplitude between 0.5mm and 5mm, as is known from the State of the art is known. This not only increases the radiation area of the lateral sides of the heating element, but it is also possible to accommodate a heating conductor tape or a heating element with a very long length for a specific value of the electrical resistance on the carrier with predetermined dimensions.

Within the scope of the invention it has been found that it is not a problem for the operation of such a heating device if the heating element, as it were, consisting of several layers of heating conductor strips, has points or areas at which these layers do not lie directly on top of one another or do not touch. Furthermore, it is also the case that such contact of the individual heating conductor strips with their lateral sides does not play a role in the current flow. On the one hand, a material from the prior art can advantageously be selected which oxidizes on its surface at least after several operating hours at operating temperature in such a way that it has a high contact resistance. So even adjacent areas of the lateral sides of the heating conductor strips are electrically insulated from one another, so to speak. On the other hand, the respective heat radiation from the individual heating conductor strips is not a problem, as has been found in tests. However, the better producibility of a corrugation for the heating conductor tape and the possible use of previously conventional heating conductor tape thicknesses clearly outweigh the advantages. Above all, one would have to reckon with problems with overbending in the case of relatively narrow corrugations with a thick heating conductor tape and this then get cracks or at least weak points. These could then lead to damage and failures during later operation at high temperatures in the visibly glowing area and the associated thermal expansion due to frequent switching on and off.

In an embodiment of the invention, the heating conductor tapes can advantageously extend over the full length of the heating element. A heating element then consistently consist of two or always three or possibly even more heating conductor strips from start to finish, which are folded together or placed one on top of the other with their lateral sides.

In a further embodiment of the invention, it can be provided that a ratio of the thickness of a heating conductor strip to its height, that is to say from the upper edge to the lower edge, is between 1:20 and 1: 500. It is particularly advantageously between 1:60 and 1: 200. A thickness of the heating conductor tape can be in the range from 0.03 mm to 0.1 mm, advantageously in the range from 0.05 mm to 0.07 mm. A height can be between 2mm and 8mm, advantageously between 3mm and 5mm.

The heating conductor strips are advantageously welded to one another, in particular this can be done by means of welding spots. Such welding spots are advantageously at a distance from one another along a longitudinal direction of the heating conductor strips, which can be, for example, twice to twenty times the height of a heating conductor strip. Alternatively, the distance can be between 5mm and 100mm, advantageously between 9mm and 20mm. Even if it is not absolutely necessary that the heating conductor strips lie completely or largely closely together or lie against one another over their length, which results from an increasing number of welding spots and the resulting smaller distance from one another, the heating element must be processed, in particular to produce the aforementioned Corrugation, as well as a possible pressing of the heating element into the upper side of the carrier, is more possible, especially if the layers of heating conductor strips lie close together.

A connection or welding of the heating conductor strips to one another is preferably arranged or carried out below half the height of the heating conductor strip, that is to say rather in a lower region of the heating element or the heating conductor strips. Such a connection or welding is advantageously provided below a quarter of the height of the heating conductor strip, particularly advantageously on a lower edge. The reason for this is that the heating element is in direct contact with the upper side of the support or by a certain, albeit slight, embedding in the upper side of the support, cooling the heating element directly and, on the other hand, heat radiation is reduced. Thus, a deterioration of the heat radiation can have a less negative effect at these connection points, particularly if it is a weld. Then it is possible under certain circumstances that the heating conductor strips move away from each other somewhat towards the top or towards their upper edges, as a result of which the radiation of the respective heating output is improved.

In principle, it is possible for a heating element to consist of a plurality or a plurality of heating conductor strips which are placed one on top of the other and are connected to one another, for example four heating conductor strips or more. The heating element is advantageously constructed in two or three layers with two heating conductor strips or three heating conductor strips on top of one another. The heating element is particularly advantageously constructed in two layers with two heating conductor strips on top of one another.

In general, it can be provided that the heating conductor strips are of identical or identical design. This can apply to their contour and / or their thickness. This can simplify production if only one type of heating conductor has to be produced. In a modification of the invention it can be provided that two heating conductor strips with the same contour and different thickness can be connected to form a heating element, the thickness difference being between 5% and 100% of the thinner heating conductor tape.

As is known per se from the prior art, the heating conductor tapes are advantageously held or arranged as a heating element upright on the upper side of the carrier. This is advantageously done at an angle of 90 °, that is to say at right angles to the top of the carrier. The upper edge of the heating element or the heating conductor strips points upwards and the respective lower edge lies against the carrier or the top side of the carrier or is even embedded or pressed in a bit in the top side of the carrier or in the carrier. This is known per se from the prior art and brings about a particularly advantageous mounting and arrangement of the heating element on the carrier. This is particularly advantageous in the case of such a multilayer heating element comprising a plurality of heating conductor tapes.

In an advantageous embodiment of the invention, the heating element has downwardly projecting holding members which are pressed into the top of the carrier in order to hold or fasten the heating element to the carrier. These holding members protrude over a line that runs for more than 80% of the length of the heating element along the lower edge and parallel to the upper edge. In particular, the holding members protrude over this line between 30% and 200% of the height of the heating conductor tape. In one embodiment of the invention, this line can be the lower edge of the heating conductor strips themselves. This is especially true when the holding members are separate components that are placed in a U-shaped or bow-like manner with two legs from above over the upper edge of the heating element, so that they protrude downward beyond the lower edge. Then the lower edge continues straight. The holding members or the two legs of the holding members enclose all layers of heating conductor strips between them. This can already be a kind of fixed connection of the heating conductor strips to one another and to the heating element. However, the holding members are advantageously additionally fastened to the heating element by means of a welded connection or by twisting the two legs which lie one on top of the other, below the lower edge. The holding members are preferably fastened to the lower edge in such a way that the two legs, which project downward beyond the lower edge, are connected to one another and at the same time to the heating element or to the heating conductor strips in the lower region, and are particularly preferably all welded to one another here. It is sufficient if the main weld connection takes place between the two legs of the holding members, as long as a small part of the weld connection is also integrally connected to the lower edges.

Thus, the holding members themselves and by means of their connection to the heating element can cause the heating conductor strips to be connected to one another in addition to their function for holding the heating element on the carrier.

In an alternative embodiment of the invention, the holding members can be provided integrally on at least one heating conductor strip as projections projecting downwards. They therefore protrude beyond the aforementioned line, which largely coincides with the lower edge, this line being interrupted only by holding members projecting downward from the lower edge. The shape of these projections can be square or rectangular, it can also advantageously be trapezoidal with a certain taper downwards in order to make it easier to insert or press into the top of the carrier.

If at least two heating conductor strips are provided for the heating element, which lie one on top of the other and are connected to one another, advantageously by the aforementioned welding points, each heating conductor strip can have holding members. The respective holding members of the respective heating conductor tapes are then not arranged to overlap, so that the heating conductor tapes lie congruently on one another, but are offset from one another. The heating conductor strips are advantageously offset from one another by the same spacing of the holding members, so that one of the heating conductor strips is alternately provided in the sequence of the holding members. For the holding effect, it is considered sufficient if a holding member is, so to speak, pressed into the upper side of the carrier only in one layer. It may even be possible to achieve a better mounting, since there can be no disadvantages if a two-layer holding member is not connected flat to one another or moves or changes due to thermal reasons. Furthermore, less integrally formed holding members can then be provided on the heating conductor strips, so that material can be saved, so to speak. In any case, integrally protruding holding members hardly or not at all take part in the heating function, since current flows through them only slightly during operation of the heating device.

On the other hand, it can also be advantageously provided in the case of integrally formed holding members that they are connected to one another for connecting the heating conductor strips to one another to form the heating element. The reason for this also lies in the fact that, as has been explained above, these holding members projecting integrally downward are not or only slightly flowed through by current. There is, so to speak, damage to the structure and, in particular, to the surfaces of the heating conductor strips by a welded connection at a location which is less stressed by the current flow and, in particular, by the heat generation, which in turn can improve the durability of the heating device.

In order to be able to manufacture a previously described heating device, two steps are carried out first. On the one hand, at least two heating conductor strips are placed on one another with their lateral sides in order to form a heating element. Furthermore, the heating element or the heating conductor strips are corrugated, with deflections of such a corrugation out of its flat lateral sides. The order of these two steps can be arbitrary or interchanged. The heating element can thus either first be formed from at least two heating conductor strips which are connected to one another in a lying manner. The corrugation can then take place in a subsequent step, so that the interconnected heating conductor strips are corrugated, so to speak. Alternatively, the individual heating conductor strips can first be corrugated, which of course takes place with an identical corrugation. They are then placed on top of one another in a subsequent step and advantageously firmly connected to one another.

If a corrugated multilayer heating element is then present, it is applied in a subsequent step in a specific laying pattern, as was mentioned at the beginning, in strips to a top of a flat carrier and fastened by pressing. In this case, either a lower edge of the heating element can be pressed into the upper side of the carrier, alternatively or additionally with holding elements of the heating element projecting downward. This application of the heating element to the carrier top of the flat carrier is advantageously carried out in accordance with the aforementioned DE 19522798 A1 , that is, by inserting the entire heating element into a kind of special assembly form with milled groove-like depressions. The heating element then protrudes a little above the top of this mounting form, so that the mounting form together with the heating element is then placed on the top of the carrier and pressed on. As a result, the heating element, in particular with the above-mentioned projecting holding members, presses into the top of the carrier for its fastening.

In an advantageous embodiment of the invention, in the method, the heating conductor strips are firmly connected to one another to form the heating element, so that the heating element is securely attached to the carrier, in particular when it is thermally moving. The heating conductor strips are advantageously connected to one another before they are corrugated, so that there is therefore a corrugation in the multilayer heating element. Then it is also easier and more precise to connect the heating conductor strips to one another according to a specific specification than if the heating conductor strips were first individually corrugated and then firmly connected to one another.

In a likewise advantageous alternative embodiment of the invention, the heating device has exactly two heating conductor strips which are formed in one piece and in one piece with one another. In particular, they are worked out from a single band, for example punched, but this is also regarded as consisting of two heating conductor bands within the scope of the invention should. The two heating conductor strips are then placed one on top of the other in the production of the heating element or the heating device by bending or folding along a bending line. As previously explained, this bending line runs parallel to the longitudinal extension of the heating element and / or parallel to the upper edge. The two heating conductor strips are thus, so to speak, only one, or are already integrally connected to one another, so that they no longer necessarily have to be connected to one another after bending or folding. This can advantageously already take place, in particular after bending or folding along the bending line with one another. Through such a connection, the shape placed on top of one another can be kept even better, advantageously by welding. The two heating conductor strips are first folded onto one another in a first step, and then in a subsequent second step the doubled heating element is corrugated. The other way around, it would hardly be possible due to the one-piece design of the heating element.

As already explained above, the two heating conductor strips can also have holding members protruding from the lower edge in this embodiment for pressing into the upper side of the carrier for holding the heating element on the carrier, these holding members advantageously projecting equally far beyond the lower edge. Particularly advantageous here are the holding members, as described above, integrally molded out of the heating conductor strips or protruding therefrom, and are therefore not separate parts. In the unfolded state, the bending edge or bending line can run centrally between the two lower edges of the two heating conductor strips, that is to say form a mirror axis, so to speak. The bending edge or bending line advantageously runs through the end edges of the aforementioned holding members, so that the two heating conductor strips are connected to one another in one piece and in one piece at the end edges or ends of the holding members. This makes bending and folding easier. Alternatively, it would also be possible to subsequently attach separate holding members to the double heating element, as previously explained.

These and other features emerge from the claims and also from the description and the drawings, the individual features being implemented individually or in groups in the form of sub-combinations in one embodiment of the invention and in other fields, and being advantageous and capable of being protected by themselves Can represent versions for which protection is claimed here. The division of the application into individual sections and sub-headings does not limit the general validity of the statements made under these.

Brief description of the drawings

Fig. 1

eine Seitenansicht eines Heizelements gemäß der Erfindung in länglicher Bandform mit integral nach unten ausgebildeten Haltegliedern,

Fig. 2

eine Draufsicht von oben auf das Heizelement aus Fig. 1 mit einer Punktschweißeinrichtung zur Verbindung von zwei Heizleiterbändern,

Fig. 3

eine Vergrößerung der Draufsicht auf das Heizelement 11 aus Fig. 2 mit einer Verschweißung und Luftspalten zwischen den beiden Heizleiterbändern,

Fig. 4

ein alternatives Heizelement in einer Darstellung ähnlich Fig. 1 bestehend aus zwei aneinander anliegenden Heizleiterbändern, deren integral ausgebildete Halteglieder versetzt zueinander sind,

Fig. 5

eine Draufsicht auf ein fertig gewelltes Heizelement bestehend aus zwei verbundenen Heizleiterbändern, die vor der Wellung miteinander verschweißt worden sind,

Fig. 6

eine alternative Ausbildung zu Fig. 5 mit zwei separat gewellten Heizleiterbändern, die zuerst zusammengelegt werden und danach verschweißt werden,

Fig. 7

eine Seitenansicht eines Ausschnitts aus einem Kochfeld mit Kochfeldplatte und darunter angeordneter Strahlungsheizeinrichtung, die auf einem Träger ein teilweise eingebettetes Heizelement aufweist,

Fig. 8

eine Draufsicht auf ein einziges durchgehendes einteiliges Band, das symmetrisch ist zu einer Mittelachse zum Aufeinanderlegen und

Fig. 9

das aufeinander gefaltete Band aus Fig. 98 in zweilagiger Form mit nach unten abstehenden Haltegliedern.

Exemplary embodiments of the invention are shown in the drawings and are explained in more detail below. The drawings show:

Fig. 1

3 shows a side view of a heating element according to the invention in an elongated band shape with integrally formed holding members,

Fig. 2

a top view of the heating element Fig. 1 with a spot welding device for connecting two heating conductor strips,

Fig. 3

an enlargement of the top view of the heating element 11 Fig. 2 with a weld and air gaps between the two heating conductor strips,

Fig. 4

an alternative heating element in a representation similar Fig. 1 consisting of two adjacent heating conductor strips, the integrally formed holding members of which are offset from one another,

Fig. 5

1 shows a plan view of a completely corrugated heating element consisting of two connected heating conductor tapes which have been welded together before the corrugation,

Fig. 6

an alternative education too Fig. 5 with two separately corrugated heating conductor strips, which are first folded together and then welded,

Fig. 7

2 shows a side view of a detail from a hob with a hob plate and a radiant heater arranged underneath, which has a partially embedded heating element on a carrier,

Fig. 8

a plan view of a single continuous one-piece band, which is symmetrical to a central axis for stacking and

Fig. 9

the band folded from one another from FIG. 98 in a two-layer form with holding members projecting downward.

Detailed description of the exemplary embodiments

In the Fig. 1 a heating element 11 is shown from the side, which, like the 2 and 3 show, consists of two heating conductor strips 13a and 13b. These are laid flat against one another and, according to the invention, run partially, but not completely, on one another. This is according to the enlargement of the top view from above Fig. 3 can be seen where isolated narrow air gaps 28 can be seen between the heating conductor strips 13a and 13b. Weldings 26 represented by crosses hold the two heating conductor strips 13a and 13b together, as a result of which they are firmly and permanently connected to one another. From Fig. 3 Air gaps 28 to be recognized can be very narrow and lie in the range from 10% to 500% of the thickness of the heating conductor strips 13.

The heating conductor strip 13a has one in Fig. 1 lateral side 15a to be recognized, a straight upper edge 17a and a lower edge 19a. The lower edge 19a runs largely straight, but is interrupted at the bottom by holding members 21a integrally projecting downward therefrom. The height of the heating conductor strip 13a can be the few millimeters mentioned at the outset, and the spacing of the holding members 21a from one another can be approximately 15 mm to 25 mm. The second heating conductor strip 13b is of exactly the same design and also has the same thickness as that Fig. 3 shows.

As the Fig. 2 Shows from above, the heating conductor strips 13a and 13b are flat together or put together and are connected by a spot welding device 23 with two welding tips 25a and 25b by means of the spot welds 26. In the embodiment of the 1 to 3 the spot welds 26 are provided at a distance from one another so that they are each provided on the holding members 21a. Essentially, they lie on the intended continued line of the lower edge 19a, but they could also lie somewhat lower below this line, that is to say fully or only in the area of the holding members 21. The reasons for this have been explained above, in particular the structure the mainly active part of the heating conductor strips 13 or of the heating element 11, which corresponds to the height of the heating conductor strips 13 between the upper edge 17 and the lower edge 19, is not adversely affected or harmful.

An alternative embodiment of a heating element 111 is shown in FIG Fig. 4 to see. There, in turn, two heating conductor tapes 113a and 113b are also put together or placed one on top of the other with their lateral sides facing one another, so that they largely touch one another. The heating conductor strips 113a and 113b are each also identical and essentially similar to the heating conductor strips 13a and 13b of the previous exemplary embodiment. They therefore have lateral sides 115, as can be seen here the lateral side 115a of the heating conductor strip 113a. Furthermore, they have upper edges 117a and 117b, and the lower edge 119a can also be seen from the heat conductor strip 113a. Both heating conductor strips 113a and 113b have integrally formed holding members 121a and 121b at the bottom. However, these are offset from one another in such a way that they follow one another alternately and are in each case not overlapping or congruent, as is the case with the heating element 11 in FIG 1 to 3 the case is. The distance between the holding members 121a and 121b to one another is therefore twice as large. Nevertheless, it is also possible to securely attach the heating element 111 to a carrier by inserting the individual holding members 121a and 121b, which are only constructed in one layer.

The two heating conductor strips 113a and 113b are in turn connected by welds 126, which are illustrated by crosses. The distance between the welds 126 corresponds also to those of Fig. 1 , only that the welds 126 cannot be carried out here on the holding members 121a and 121b. Finally, these holding members 121a and 121b do not abut each other because they are offset from one another. For this reason, the welds 126 are provided in the lower region of the heating conductor strips 113a and 113b, that is to say closer to the lower edge 119 than to the upper edge 117, in each case exactly in the middle between adjacent holding members 121. According to yet another embodiment of the invention, the welds 126 could also be so be made that they directly connect a lower edge 119 of a heating conductor strip 113 with a holding member 121 of the other heating conductor strip 113.

In the top view of the Fig. 5 on a heating element 11 it can be seen what the state is after the corrugation, that is to say when the heating element 11 is completely corrugated. The two-layer heating element 11 produced as prescribed from the two heating conductor strips 13a and 13b has passed through a device for corrugation, as is also already used in the prior art for producing corrugated heating elements known from the documents mentioned at the beginning. Where the holding elements 21 or the welds 26 lie in the course of the corrugation, that is to say whether in apexes or in inflection points of the wave course, does not matter for the finished heating element 11.

In an alternative method for producing a heating device or a heating element for a heating device, according to Fig. 6 first the individual heating conductor strips 13a and 13b are corrugated. Basically, a shape of this curl can be that of Fig. 5 correspond and take place as known in the prior art. Then the two heating conductor strips 13a and 13b are placed one on top of the other, advantageously in such a way that their holding members, not shown here, either lie exactly on top of one another accordingly Fig. 1 or offset from one another are corresponding Fig. 4 . The welds are then carried out by means of the welding tips 25a and 25b in the previously described manner in order to firmly and permanently connect the two heating conductor strips 13a and 13b to one another. The locations for the welds can be selected as described above.

At the in Fig. 6 The methods shown are therefore first the individual heating conductor strips 13 are corrugated and then folded or placed on top of one another and then firmly and permanently connected to one another. This has the advantage that a corrugation of the heating conductor tapes is certainly easier, since it corresponds exactly to the procedure according to the prior art or as it is currently carried out. However, the disadvantage is that the subsequent welding is difficult to carry out, even with relatively thin welding tips. After all, they actually have to be welded to the shaft crests, i.e. to the Vertices, because here it is easiest to compress the heating conductor strips. However, this is probably not always easy to do. Furthermore, it is not foreseeable that welding will then always correspond to the surfaces of the holding members Fig. 1 can be made if so desired.

In the simplified representation of the Fig. 7 A hob 30 with a hob plate 31 and a heating device 33 according to the invention is shown underneath. The heating device 33 is applied to the underside of the hob 31, as is known in the prior art. The heating device 33 itself is designed as a so-called radiation heating device and has a flat and flat support 35 with an outer circumferential support edge 36. A heating element 11 is applied to a large part of the surface of the support 35 within the support edge 36, specifically in a circumferential manner not shown here or meandering form as a laying pattern, possibly also concentric. However, this can also be found in the prior art. Above all, the pressing in of a heating element 11 is advantageous Fig. 5 , which is therefore two layers and is not continuously connected or welded together over its length, can be carried out well. In from the prior art in the form of the aforementioned DE 19522798 A1 Known press-in molds can also be used to insert such a double-layer heating element, which is then pressed in as is known in the prior art. In the Fig. 7 Dotted holding members 21 are then pressed into the carrier 35, possibly also the lower edge of the heating conductor strips a bit.

With such a heating device 33 accordingly Fig. 7 together with a heating element 11 according to the invention, which is two-layer or three-layer and consists of superimposed and non-detachably connected heating conductor strips, a significantly higher heating output can be achieved with a simple and easy to carry out manufacturing process which is ensured at the same time.

In the Fig. 8 For a further embodiment of the invention it is shown how two heating conductor strips 213a and 213b are already produced in one piece and in one piece from the beginning. The two heating conductor strips 213a and 213b run mirror-symmetrically to a bending line B shown in dash-dotted lines. In this case, recesses 220 are punched out in an elongated form from a single originally wide strip of corresponding heating conductor material, which in turn are symmetrical with respect to their longitudinal direction to a bending line B.

As a result of these punched-out recesses 220, the heating conductor strips 213a and 213b have not only the upper edges 217a and 217b as outer edges of the previously continuous wide strip, but also lower edges 219a and 219b. From these lower edges 219a and 219b are holding members 221a and 221b from or above, the two heating conductor strips merging into one another on the holding members 221a and 221b. The shape of the recesses 220 accordingly determines the shape of the holding members 221a and 221b and the height of the heating element in the finished state Fig. 7 .

Where the bending line B runs through these holding members or runs through opposite holding members 221a and 221b, bending edges 222 are provided, specifically along this bending line B. These bending edges 222 can be formed as continuous bending edges by embossing or grooving or, so to speak, prefabricated. You can use it to specify the point at which the two heating conductor strips are then bent and folded onto one another along the bending line B. Similar to in Fig. 1 it can be clearly seen here how large the distance of the holding members 221a and 221b is along the longitudinal direction of the heating conductor strips in the non-corrugated state. Of course, the holding members could also be made shorter or longer, narrower or wider, closer to each other or further apart.

If the two heating conductor strips 213a and 213b have been folded onto one another along the bending line B, and they overlap exactly, the structure of FIG Fig. 9 . This shows a heating element 211 from the side in front of the waves, again in accordance with or similar to that in FIG Fig. 1 . Here you can see that at the Fig. 8 the lower heating conductor strip 213b was folded along the bending line B into the plane of the drawing by 180 ° so that it was as flat as possible or in plan view in accordance with FIGS 2 and 3 to lie on the other heating conductor strip 213a, in each case with the inside. Then the two lateral sides 215a and 215b each point outwards, as is provided according to the invention. From the Fig. 9 it can also be seen that the lower edge of the holding members 221a is formed by the bending edges 222. This closed lower edge can even possibly be similar to an indentation into a carrier 35 Fig. 7 facilitate.

Right in the Fig. 9 shows how two possible spot welds 26 can be provided. The left punctiform weld 226 is located approximately halfway up the heating conductor strip 213. However, it could also be provided higher or lower or somewhere between the upper edge 217a and lower edge 217b, possibly directly on one of these edges. The right option is a spot weld 226 on a holding member 221a or approximately in the center of the surface of this holding member. This weld 226 is then only a very small distance from the lower bending edge 222, so that the holding action against bending the heating element 211 or bending the two heating conductor strips 213a and 213b away from one another is not very good. However, since the heating element 211 is still to be corrugated, in particular with a final shape corresponding to the top view of FIG Fig. 5 , such a bending or spreading apart is hardly possible or probable here. As a result, the spot welds 226 can be dispensed with altogether, which significantly reduces the assembly effort and increases the service life.

As a great advantage in the embodiment of the 8 and 9 viewed that the original one-piece and integral production of the two heating conductor strips in such a way that they are connected and then bent or folded onto one another, their position relative to one another is predetermined and unchangeable. The position of the two heating conductor strips in the folded state with respect to one another is thus precisely predetermined and cannot be changed. In addition, punching waste can be reduced, and it is not absolutely necessary that spot welding is carried out.

In itself you can from the 8 and 9 see that the two heating conductor tapes do not necessarily have the same shape and must be completely congruent with each other after folding or bending. Other constellations are also conceivable. For reasons of an even distribution of the heating power and especially the surface heating power, this is highly recommended.

Claims (13)

1. Radiant heating device (33) for a hob (30), comprising:

   - a sheet-like support (35) with a support top side,

   - at least one heating element (11, 111, 211) on the support top side, which heating element runs in tracks in a laying pattern,

   - wherein the heating element has at least two heating conductor strips (13a, 13b, 113a, 113b, 213a, 213b) which each have lateral sides (15a, 15b, 215a, 215b) and a top edge (17a, 17b, 117a, 117b, 217a, 217b) and a bottom edge (19a, 19b, 119a, 119b, 219a, 219b),

   - wherein the at least two heating conductor strips (13a, 13b, 113a, 113b, 213a, 213b) are connected to one another in a fixed and non-detachable manner,

   characterized in that:

   - the at least two heating conductor strips (13a, 13b, 113a, 113b, 213a, 213b) are placed together or placed on one another by way of their mutually facing lateral sides (15a, 15b, 215a, 215b) and are partially in contact, but do not completely run against one another.
2. Heating device according to claim 1, characterized in that the ratio of thickness of a heating conductor strip (13a, 13b, 113a, 113b, 213a, 213b) to its height in a direction away from the support top side lies between 1:20 and 1:500, preferably between 1:60 and 1:200.
3. Heating device according to claim 1 or 2, characterized in that the heating conductor strips (13a, 13b, 113a, 113b, 213a, 213b) are welded to one another, in particular by welding points (26, 126, 226), preferably at a distance along a longitudinal direction of the heating conductor strips from one another which is 2-times to 20-times the height of a heating conductor strip.
4. Heating device according to any of the preceding claims, characterized in that a connection (26, 126, 226), preferably by welding according to claim 3, is arranged below half the height of the heating conductor strip (13a, 13b, 113a, 113b, 213a, 213b), preferably below a quarter of the height of the heating conductor strip.
5. Heating device according to any of the preceding claims, characterized in that it has precisely two heating conductor strips (213a, 213b) which are designed in one part and integrally with one another, in particular are machined out of a single strip, and are placed on one another by bending or folding along a bending line (222) which runs parallel in relation to the longitudinal extent of the heating element (211) or parallel in relation to the top edge (217a, 217b), wherein preferably the two heating conductor strips have holding elements (221a, 221b) which protrude from the bottom edge and are to be pushed into the support top side for the purpose of holding the heating element on the support (35), wherein preferably the holding elements each protrude beyond the bottom edge (219a, 219b) to the same extent, and in particular the bending edge or bending line runs through the end edges of the holding elements in such a way that the two heating conductor strips are connected to one another at the end edges of the holding elements.
6. Heating device according to any of the preceding claims, characterized in that the heating element (11, 111, 211) is of two-layer or three-layer design with two heating conductor strips (13a, 13b, 113a, 113b, 213a, 213b) on one another or three heating conductor strips on one another, preferably identical heating conductor strips.
7. Heating device according to any of the preceding claims, characterized in that the heating conductor strips (13a, 13b, 113a, 113b, 213a, 213b) are held upright on the support top side, in particular at an angle of 90°, wherein preferably the top edge (17a, 17b, 117a, 117b, 217a, 217b) is at the top and the bottom edge (19a, 19b, 119a, 119b, 219a, 219b) is on or in the support (35).
8. Heating device according to any of the preceding claims, characterized in that the heating element (11, 111, 211) has downwardly protruding holding elements (21a, 21b, 121a, 121b, 221a, 221b) which are to be pushed into the support top side for the purpose of holding the heating element on the support (35), wherein preferably the holding elements protrude beyond a line which runs by more than 80% of the length along the bottom edge (19a, 19b, 119a, 119b, 219a, 219b) and in parallel to the top edge (17a, 17b, 117a, 117b, 217a, 217b), wherein the holding elements in particular protrude beyond this line by between 30% and 200% of the height of the heating conductor strip (13a, 13b, 113a, 113b, 213a, 213b).
9. Heating device according to claim 8, characterized in that the holding elements are separate components which are placed over the top edge of the heating element by way of two limbs in a U-shape or bow-shape and protrude downwards beyond the bottom edge, wherein they enclose all of the layers of heating conductor strips between them here, wherein preferably the holding elements are fastened to the heating element by means of a weld connection, in particular fastened to the bottom edge, in such a way that the two limbs which protrude downwards beyond the bottom edge are connected to one another and, at the same time, to the heating element in the lower region, wherein preferably holding elements are integrally formed on at least one heating conductor strip as projections which protrude downwards and protrude beyond the line.
10. Heating device according to claim 6 and according to any of the claims 8 or 9, characterized in that at least two heating conductor strips (13a, 13b, 113a, 113b) are provided and lie on one another and are connected to one another, wherein each heating conductor strip has its own holding elements (21a, 21b, 121a, 121b), wherein respective holding elements of the respective heating conductor strips are not arranged in an overlapping manner, but are offset in relation to one another, in particular are alternatingly offset in relation to one another by the same distance.
11. Heating device according to any of the preceding claims, characterized in that the heating element (11, 111, 211) is corrugated, preferably with a wavelength of between 2 mm and 8 mm and/or with a wave amplitude of between 0.5 mm and 5 mm.
12. Heating device according to any of the preceding claims, characterized in that all of the heating conductor strips (13a, 13b, 113a, 113b, 213a, 213b) of the heating element (11, 111, 121) are identical.
13. Method for producing a radiant heating device (33) according to any of the preceding claims, characterized by the following steps:

    - at least two heating conductor strips (13a, 13b, 113a, 113b, 213a, 213b) are placed on one another in order to form a heating element (11, 111, 121),

    - the heating conductor strips (13a, 13b, 113a, 113b, 213a, 213b) are fixedly connected to one another to form the heating element (11, 111, 121), wherein they partially contact, but do not completely run against one another,

    - the heating element (11, 111, 121) is corrugated with deflections of a corrugation out of its flat lateral sides (15a, 15b, 215a, 215b),

    wherein the order of the first two steps can be arbitrary,

    - the heating element (11, 111, 121) is then applied to the support top side of the flat support (35) in a laying pattern in tracks and fastened by being pushed in.

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