Heating devices and electric furnace equipment

Abstract

The heating device for an electric cooktop has at least one long heat conductor, a base, on the upper side of which the heat conductor is arranged and fixed, and a support device for the base. The heat conductor is designed as a curled flat strip, which has fastening elements arranged at a distance from each other on its lower side, which extend downward in one piece and are pressed into the base. The support device supports the base downward at least in the outer area of ​​the base along the outer edge. The base is made of a pressed and / or glued mica material, for example bonded mica, as a thin plate and is therefore electrically insulating and sufficiently stable.

Description

Technical Field

[0001] The invention relates to a heating device, such as can be used in particular for or in an electric stove, for example as a cooktop, a warming plate or as an oven. The invention also relates to a corresponding electric stove having at least one such heating device. Background Art

[0002] US Pat. No. 4,161,648 A and US Pat. No. 5,498,853 A each disclose a heating device that can be embedded in a cooktop below a cooktop plate. A plurality of long or elongated heat conductors are fixed to a flat base made of an electrically and thermally insulating material. From the heat conductors stand fastening elements that are pressed into the base and thus hold the heat conductors upright. In this case, the heat conductors can be heated red-hot in the visible range at temperatures of up to approximately over 1000° C. during operation. Summary of the invention

[0003] The object of the invention is to provide a heating device of the type mentioned at the outset and a corresponding electric furnace installation with which the problems of the prior art can be solved and in particular it is possible to use stable, inexpensive and advantageous materials for the base.

[0004] This object is achieved by a heating device according to the invention and by an electric furnace device according to the invention. Advantageous and preferred embodiments of the invention are the subject of the following description and are further explained below. Some of these features are described here only for the heating device or only for the electric furnace device. However, regardless of this, these features should be independent of each other and independently applicable not only to the heating device but also to the electric furnace device. The terms of the claims are made by explicit reference to the contents of the description.

[0005] The heating device has at least one long heat conductor, which can be manufactured in a slender manner, but is advantageously shortened in an assembled state. For this reason, the heat conductor is configured as a curled flat belt, which has at least on its lower side fastening elements arranged at intervals from each other. These fastening elements extend downward or stand up downward. The heating device has the previously mentioned base, on which the heat conductor is arranged and fixed on the upper side, in a manner that these fastening elements are pressed into the base. In particular, in the case where a recessed portion, a blank portion or the like has not been manufactured or prepared for the fastening element in advance, the fastening element is pressed into the base, wherein such a recessed portion, a blank portion or the like alternatively can also be manufactured or prepared in advance. The heat conductor with the fastening element is simply pressed into the base or the upper side of the base with a corresponding force. Here, the heat conductor should be stabilized or fastened so that the heat conductor does not tilt, which is known from the prior art for the so-called radiation heating device mentioned above. This will have a negative impact on the arrangement of the heat conductor on the base. A supporting device is also provided for the base. The support device supports the base at least in its outer region and / or along the outer edge. It is then possible to use a relatively thin base which, although stable per se, could already bend too strongly due to the load of the heat conductor arranged thereon. Preferably, the support device can also support the base in the middle region or in at least one location in the middle.

[0006] According to the invention, it is provided that the base is made of a pressed and / or glued mica material. Thus, an insulating material is used which is different from the insulating materials known in the prior art, in particular known and used for radiant heating devices. Such a mica material is sufficiently electrically insulating and has sufficiently good thermal insulation properties. Furthermore, the mica material is sufficiently stable to fasten the fastening element pressed into it and thus also the heat conductor.

[0007] In an advantageous embodiment of the invention, the mica material preferably has a coefficient of expansion similar to that of the heat conductor up to about 250° C. Advantageously, the heat conductor is a FeCrAl alloy, as is known from the prior art for such heat conductors, in particular even if the FeCrAl alloy is to glow red in the visible range during heating operation. With these adapted coefficients of expansion, mechanical stability or a permanently stable structure of the heating device can be achieved more easily. The coefficient of expansion of such a heat conductor can be slightly increased above the previously mentioned temperature of 250° C., but this should not be a problem in an advantageous embodiment due to the curled shape of the heat conductor. In addition, at higher temperatures, the fastening element can therefore better grip in the base due to the more intense expansion.

[0008] Preferably, the mica material is bonded mica. Such bonded mica or mica materials in general are also known, for example, from toasters, in which a heating coil is wound around a flat plate for mechanical fastening. However, the heat conductor is not pressed into the plate itself here, but at most drawn into a prefabricated cutout. Bonded mica can have muscovite as a main component, alternatively phlogopite for even higher temperatures.

[0009] In the design of the present invention, it can be provided that the base is constructed as a plate. The base can have a flat upper side in particular. However, the upper side can also be slightly arched, or arched in a groove-shaped or convex or concave manner. At least one heat conductor is arranged on the upper side and then heated upwards. Particularly preferably, the base is a thin plane-parallel plate. A thickness between 0.1 mm and 2 mm, in particular 0.2 mm to 0.6 mm, is considered to be advantageous. In the lower thickness range, the thickness is just stable enough so that the pressed-in fastening elements of the heat conductor do not fall off again on their own. At the same time, for a very thin base, not so much mica material is needed.

[0010] If the base is made thicker, it stabilizes itself better. The electrical and thermal insulation properties of the base then also become better. The base may also be stabilized itself so that the support means only need to be arranged in the outer area or along the outer edge. The base can also be so thick that the correspondingly short fastening elements do not re-emerge on the underside. Preferably, however, the fastening elements re-emerge from the underside of the base or stand on it.

[0011] In other embodiments of the invention, spacers can be arranged in the region of the outer edge of the base, in particular together with the support device. These spacers can rise upward from the upper side of the base. Advantageously, these spacers lie flat on the upper side of the base. Particularly advantageously, these spacers can be designed as a substantially continuous surrounding ring, which makes it possible to maintain the spacing of the heating device and in particular also the base with the heat conductor thereon from the cooktop plate or other covering arranged thereon of the cooktop. If, however, the heating device is used in an oven, in particular as a top or bottom heating element, and if it is even exposed to the outside, spacers may not be required on the upper side.

[0012] Advantageously, it can be provided that the fastening elements are manufactured as a bracket independently of the heat conductor and then covered on the heat conductor. Then, these bracket-like fastening elements are fixed together with the heat conductor on the upper side of the base, especially by being pressed into the base.

[0013] However, it is particularly advantageous if the fastening elements are integrally formed from the thermal conductor or molded onto the thermal conductor, i.e. they are connected to the thermal conductor in one piece and in a single-piece configuration. The fastening elements are thus formed from the same continuous flat strip material and extend downwardly in one piece and in a single-piece configuration from the lower edge of the thermal conductor. This means that the fastening elements are integrally formed from the thermal conductor. For this purpose, the thermal conductor can be stamped out of the flat strip material as a strip, wherein the fastening elements are formed at the lower edge. However, in principle, this is also known from US Pat. No. 5,498,853 A mentioned at the outset.

[0014] The length of the fastening element may be between 50% and 200% of the height of the thermal conductor. In other words, the length of the fastening element may be between 1 mm and 6 mm, wherein the height of the thermal conductor may typically be a few millimeters, for example 1.4 mm to 7 mm.

[0015] According to the invention, the heat conductor is curled, preferably uniformly over its entire length. The curling can also include fastening elements integrally formed thereon. The fastening elements are arched away from the heat conductor in their longitudinal extension so that they are arched like a spade or the like, which can help to significantly improve the stability when the fastening elements are inserted or pressed into the mica material of the base. In this way, when these fastening elements, which are thus more stably constructed, are pressed into the mica material, they cannot be easily bent.

[0016] In other advantageous designs of the present invention, the fastening elements can be constructed in a tapered manner away from the heat conductor or in a direction transverse to the heat conductor in its longitudinal extension in order to facilitate insertion into the base. That is, these fastening elements can have a tapered free tip at the free end. The free tip can be directly pointed or slightly rounded. In addition, the fastening elements can have a base area connected to the lower edge of the heat conductor. It is important in this area that the fastening elements are well connected to the heat conductor. In the base area, the fastening elements have a constant width, that is, the sides of the fastening elements are parallel. Then, the tapered free tip is connected to the base area of ​​constant width, advantageously directly connected to the base area of ​​constant width. This base area can have a length between 0.1mm and 2mm. The base area is used for: when the heat conductor is pressed into the base with the fastening elements, so that the lower edge of the heat conductor is completely or almost flat on the upper side, these fastening elements are in the base with this base area. The tapering free tip of the fastening element, which already greatly simplifies insertion, then stands out on the underside of the base. If the fastening element is inserted into the base only with the base region or thus has only direct contact with the base, and this base region has an exactly identical width, the fastening element is not pressed out of the relatively hard mica material so easily. The structure is therefore more stable and more durable.

[0017] In an advantageous design of the present invention, the previously described tapering free tip can be connected to the mentioned base area. Here, the tapering free tip can be narrower than the minimum width of the base area in the area above it or the position where the tapering free tip is directly connected to the base area or extends from the base area. Particularly advantageously, the tapering free tip not only stands up or extends in the direction of the longitudinal extension of the thermal conductor on the base area, but also stands up or extends on the base area on both sides. In particular, the tapering free tip can be approximately or just stand down from the middle of the width of the base area. It is considered preferred that the base area is composed of only one part and extends from the thermal conductor in an integrated manner or is constructed using the thermal conductor, for example, molded from a flat strip material as a part of a fastening element according to the previously mentioned method. Similarly, the tapering free tip can be advantageously molded together with the base area as other parts of the fastening element.

[0018] Such a base region can have a width or, to some extent, a length in the longitudinal direction of the heat conductor, which is between 2 mm and 10 mm or between 2 mm and 15 mm. In other words, the width of the base region can be between 100% and 400% of the height of the heat conductor. For this purpose, the details are also explained later.

[0019] Advantageously, the base area is not pressed into the base or is not in it. The base is preferably made of a fairly strong material, such as the bonded mica mentioned at the beginning or the like, so that there is no need to make an effort to press the fastening element into the base with the base area. It is enough to press the fastening element in. At the same time, the base is thus mechanically weakened to a lesser extent. The base area can be located on the base or on the surface of the base, alternatively, the base area can be laid flat on it or even pressed on it due to the fastening element being pressed in with a tapering free tip. In this way, the base area can be said to form a support for the heat conductor on the base to a certain extent, and because the base area has a length of about 0.1mm to 2mm mentioned above away from the heat conductor, the heat conductor extends about this extent with its lower edge on the surface of the base. This has the following advantages: on the one hand, the base area is then not cooled by the base on its lower side and can thus achieve better heat release, especially also including upward heat radiation. On the other hand, less heat enters the base, which would otherwise be subjected to greater thermal and mechanical stresses and would require greater thermal insulation. By widening the cross section of the heat conductor in the region of the fastening element or the base, the heat release or heating power is somewhat lower here. However, this negative effect is more than compensated by the higher radiation. In addition, a defined extension of the heat conductor on or above the base can be achieved in this way.

[0020] It is preferably provided that exactly one base region is provided for each fastening element, or that all fastening elements each have a single base region. It is particularly advantageous if all fastening elements are designed identically, which results in a planar distribution of the thermal power that is as uniform as possible. In yet another advantageous embodiment of the invention, the thermal conductor with its fastening elements, in particular the tapering free tip, is pressed uniformly and far into the base or the surface of the base at all locations. This uniform production then also results in a heat generation that is as uniform as possible.

[0021] Advantageously, it is possible that the tapering free tip first has a uniform width in the region where it connects to the base region for the advantages mentioned above, and that the tapering free tip is then pressed or embedded into the base with this region of approximately uniform width. This region of uniform width can form an additional base region, wherein the additional base region can directly connect to the base region at the top and can directly transform into the tapering free tip at the bottom. In fact, the tapering region or tip region then protrudes downward from the underside of the base. This makes it possible that the tapering tip cannot be pressed out of the base so easily due to its tapering. That is, the additional base region of uniform width is here.

[0022] The base region can extend straight to the heat conductor at both ends, i.e. at an angle of 90° to the other lower edge of the heat conductor, or obliquely or also with one or more roundings. This does not work because the base region is not to be pressed into the base in any broad design. Here, the production advantages of the straight, oblique or rounded shape can be used as desired.

[0023] In the design of the present invention, the power per unit area of ​​the heating device in the area of ​​the heat conductor or at the position where the heat conductor extends can be a maximum of 4 W / cm 2 In particular, the power per unit area can be even lower, for example, lower than 2.5 W / cm 2 In the case of such low power densities, it is possible, based on safety regulations, to operate a heating device under the cooktop similar to the above-mentioned radiant heating device, wherein the heating device does not require temperature monitoring for this purpose according to the VDE. This means that the heating device can be operated in a somewhat unprotected manner. Such protection or temperature monitoring would be a so-called safety temperature limiter or a benchmark controller, as is also shown, for example, in US Pat. No. 5,498,853 A mentioned at the outset.

[0024] Advantageously, at least one heat conductor covers a large part of the surface of the heating device, for which purpose the tracks of the heat conductor can extend on the base at intervals of between 5 mm and 20 mm from one another. These tracks can extend parallel to one another to a large extent or more than 80%, for example in a meandering manner or in a spiral.

[0025] In one embodiment, the electric cooking device according to the invention can be an electric cooktop having a cooktop plate and a plurality of heating devices arranged thereunder, which are designed according to the invention. An operating device is arranged on the cooktop in a manner known per se, by means of which the operation of the cooktop can be controlled.

[0026] In an alternative design, the electric stove device according to the invention can be an oven, wherein it is advantageously conceivable that the heating device is built as the top and / or bottom in the oven. That is, in the case of the invention, a relatively cheap heating device can be provided for this purpose.

[0027] These and other features are apparent not only from the claims but also from the description and the drawings, wherein each feature can be realized in its own right or in the form of several subcombinations in embodiments of the invention and in other fields and are advantageous and protectable embodiments in their own right, for which protection is claimed. The division of the application into individual parts and also into intermediate headings does not restrict the statements made thereunder in terms of their generality. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Embodiments of the present invention are schematically shown in the drawings and are explained in more detail below. In the drawings:

[0029] Figure 1 shows a side section through an electric cooktop according to the invention having a heating device according to the invention arranged on a cooktop plate;

[0030] Figure 2 Shows that only Figure 1 Enlargement of the middle area of ​​the heating device;

[0031] Figure 3 Shows something like Figure 2 A diagram of a first design of a heat conductor;

[0032] Figure 4 Shows a similar Figure 1 A top view of a portion of a thermal conductor arranged in a manner as shown in FIG.

[0033] Figure 5 An alternative embodiment of a heating conductor according to the invention with a differently designed fastening element is shown;

[0034] Figure 6 Shows something like Figure 2 According to an alternative design of the heating device of the present invention, there is no spacing between the supporting device and the base; and

[0035] Figure 7 A further alternative embodiment of the heating conductor according to the invention is shown with a fastening element which is again designed differently. DETAILED DESCRIPTION

[0036] exist Figure 1, a fragment of an electric stove device 11 according to the invention is shown from the side. The electric cooktop 11 has a cooktop plate 13, against the underside 14 of which the heating device 16 according to the invention is pressed in a manner not shown in detail. This is advantageously done as is generally known from such electric cooktops and does not need to be explained in detail here. The heating device 16 has a flat and thick backing 18 as the aforementioned support device. The surface of the backing is essentially flat, except that a support projection 20 is formed in the middle, which has a height of several centimeters. A surrounding and stepped support edge 22 is formed outside the backing 18. An annular body 24 lies on the support edge 22, which surrounds and is pressed with its upper side against the underside 14. The backing 18 and the annular body 24 are formed of suitable and known heat-insulating materials, which may be different materials. This basic structure is known from the prior art, see US 4161648 A and US 5498853 A mentioned at the beginning.

[0037] The base 26 according to the invention rests on the step of the central support projection 20 and the support edge 22. The base is advantageously a disk or plate made of the aforementioned bonded mica with a thickness of, for example, 0.5 mm. The self-stability of the plate made of bonded mica, which is so thin that it does not bend downwards or only bends downwards insignificantly or without causing any problems, is also sufficient in the base 26 due to the support in the middle by means of the support projection 20. The bonded mica here is ground mica bonded with a synthetic resin.

[0038] In the outer edge region, the base 26 is clearly fastened between the supporting edge 22 from below and the annular body 24 from above or, to a certain extent, clamped between the supporting edge and the annular body. In this way, the arrangement of the base in the heating device 16 is reliable and does not change, both during operation and during transportation.

[0039] The base 26 has a heat conductor 29 on its upper side, as already described at the beginning. The heat conductor 29 is an upright, curled flat strip, which lies flat on the upper side of the base 16 at its lower edge. The heat conductor 29 is fixed to the base 26 by means of fastening elements 31, which are briefly outlined here. For this purpose, these fastening elements, such as can be seen from Figure 2 As can be seen better in the enlarged view of FIG. 2 , it passes through a base 26 made of bonded mica and re-extends from the base 26 at the bottom with a certain amount of excess. Figure 2It can also be seen that the lower edge 30 of the heat conductor 29 lies directly on the upper side of the base 26. This is achieved in that the heat conductor 29 is pressed against the base 26 when the fastening element 31 is pressed in with force and forms a stop, so to speak, by the lower edge 30 hitting or lying on the upper side of the base 26. In the case of other thermal insulation materials, the lower edge can be pressed into them somewhat, but this is not the case here in the case of the bonded mica.

[0040] This pressing in corresponds essentially to the production method as used for the known radiant heating bodies according to the above-mentioned US Pat. No. 4,161,648 A and US Pat. No. 5,498,853 A. In this respect, reference is made here to this prior art.

[0041] from Figure 1 and 2 : Advantageously, the heat conductor 29 is first fixed to the base 26 by pressing in and inserting the fastening element 31. Only then is the base 26 with the heat conductor 29 thereon built into the heating device 16. In other cases, the required stability during pressing in would not be ensured.

[0042] The air chamber 28 between the base 26 or its underside and the backing 18 or its upper side can be a maximum of a few millimeters high, for example a maximum of 5 mm high. This air chamber 28 can serve as additional thermal insulation between the heat conductor 29 or the base 26 heated by the heat conductor and the backing 18. In this way, the fastening elements 31 of the heat conductor 29 protruding from the underside of the base 26 are not yet in the way. However, the air chamber 28 can also be omitted entirely, see Figure 6 .

[0043] As yet another alternative, the backing 18 of heat-insulating material may be completely omitted, so that the base 26 with the heat conductor 29 thereon is only fastened in a metal plate that is common for radiant heating bodies. A spacing of, for example, more than 1 mm to 10 mm can then be provided between the base 26 and the bottom of such a metal plate, which can be used not only for electrical insulation but also, in particular, for thermal insulation.

[0044] exist Figure 3 , in order to illustrate the thermal conductor 29, the thermal conductor 29 in a flatly elongated state is shown. The thermal conductor 29 has a substantially straight, continuous lower edge 30, from which the fastening elements 31 extend downward in one piece at intervals. As can be seen here, the fastening elements 31 are constructed to taper over their entire length. These fastening elements do not taper downward at the lower end 34, and are not even rounded, but are cut straight off. However, other possibilities can also be realized. The thermal conductor 29 is preferably stamped out of a wide strip or a flat flat strip material.

[0045] exist Figure 4 2 shows a top view of the heat conductor 29, which is curled here. This should be explained: the heat conductor 29 is not fixed to the base 26 in a slender or elongated state, but this is also possible in principle. Figure 4 The view cannot be seen according to Figure 3 However, according to this diagram, it can be easily seen that at least according to Figure 4 Those fastening elements 31 that rise from the lower edge of the heat conductor 29 in the region of the strong bend or curling are bent accordingly. This results in the aforementioned bulge of the fastening element. On the one hand, this is almost mandatory by Figure 4 On the other hand, this has the great advantage that by means of this curling, the fastening elements 31 become more stable or more rigid, provided that they are reshaped in this way, and can thus be pressed more easily into the base 26.

[0046] exist Figure 5 1 shows an alternative heat conductor 129 of the heating device 116. Fastening elements 131 again stand up from the lower edge 130 at intervals. However, the fastening elements 131 are designed differently here. These fastening elements directly connect to the lower edge 130 and have a base area 133, which has a uniform width and can be, for example, 2 mm long. A tapering tip 134 connects to the base area 133. This tapering tip is similar to Figure 3 To construct.

[0047] The advantages of this design of the fastening element 131 can be clearly seen if the base 126 shown in dashed lines or the embedded state thereon is observed. The fastening elements 134 are located in the base 126 with the base area 133, and since they do not taper or bevel here, they are better fastened therein or cannot be pressed out so easily. Parallel outer edges are neutral with respect to pressing out. This was explained at the beginning.

[0048] The design of the tip 134 can vary in various ways; on the one hand, it can be substantially pointed, or alternatively it can also be slightly rounded, which likewise facilitates insertion into the base 126 .

[0049] Generally, recesses or cutouts which are intended to facilitate insertion may already be prefabricated or stamped out in the base 126. However, these recesses or cutouts must then be precisely matched to the position of the fastening element to be inserted.

[0050] exist Figure 6 In a similar way Figure 2The fragment of FIG. 1 shows an alternative heating device 216. Here, there is a Figure 3 The heat conductor 229 of the fastening element 231 shown in a dotted manner is not only inserted into the base 226, but also inserted into the flat backing pad 218 extending directly below it. The order should also be exactly this order. Although it is possible in principle to press the heat conductor 229 with the fastening element 231 directly onto the layer composite consisting of the base 226 and the backing pad 218 and to press the fastening element 231 into both. This is considered to be difficult, so that the two-stage pressing can be considered as preferred. The base 226 with the fastening element 231 is then placed and pressed onto the backing pad 218, so that the lower tip of the fastening element 231 is also pressed into it.

[0051] In accordance with Figure 6 In the heating device 216, Figure 2 As already acknowledged, the air chamber 28 described is omitted, and the thermal insulation is thus significantly worse. However, if the heating device is not to be operated at very high temperatures of up to 350° C. or briefly up to 700° C., then in this way an improvement of the thermal insulation can be omitted and a simpler and more mechanically stable design can be preferred for this purpose.

[0052] according to Figure 1 The power per unit area of ​​the heating device 16 is advantageously the aforementioned maximum of 4 W / cm 2 Particularly advantageously, the power per unit area is less than 2.5 W / cm 2 , the heating device 16 can then be used as a warming zone or the like in the electric cooktop 11, and temperature monitoring by the reference controller mentioned at the beginning, as is present in the above-mentioned documents of the prior art, is not required. The operating temperature of the heat conductor 29 itself can then be, for example, between 100° C. and 250° C. The base 26 made of bonded mica can withstand temperatures of about 500° C. for a long time, and even slightly higher temperatures depending on the adhesive of the base or mica material. It can be up to 700° C. in less than a minute. In principle, however, such a heating device should not be designed for such high temperatures at the limit, but should be designed just for a maximum of 350° C. or only a maximum of 150° C. In the cooktop mentioned at the beginning, this is then a so-called warming cooking location.

[0053] Particularly advantageously, the base consists of a plate made of bonded mica and muscovite, alternatively phlogopite. This is synthetic mica, which is made from cracked, broken or ground mica of the corresponding material. For this purpose, these mica fragments are compressed with a synthetic resin as a binder and baked, for example, to form a very thick mica foil or to form mica blocks or mica plates as just described above. However, its production is known to those skilled in the art.

[0054] exist Figure 7 3 shows another alternative heat conductor 329 of the heating device 316. At intervals, fastening elements 331a to 331d stand downward from the lower edge 330 of the heat conductor 329. However, the fastening elements 331 are constructed differently here, which is only shown in this way for the sake of clarity. In practice, advantageously, all fastening elements 331 are constructed identically. However, these fastening elements all have base areas 333a to d directly connected to the lower edge 330, which can have different widths, advantageously between 5mm and 15mm. Tapered tips 334 are connected to the corresponding base areas 333 respectively. The tapered tips 334 can be constructed similarly to the previous figures.

[0055] In the case of the leftmost fastening element 331a, the base area 333a is obliquely disengaged from the lower edge 330. The base area 333a lies flat on the upper side of the base 326. The tapering tip 334a is disengaged from the center of the base area 333a, which is configured to be gradually pointed. The tapering tip 334a passes through the base 326 and is therefore the fixation of the thermal conductor 329 on the base 326, wherein the tapering tip 334a itself is fastened in the base 326. Stable fastening is possible by the obvious wide support area of ​​the lower edge of the base area 333a on the left and right sides of the tapering tip 334a on the base 326. Further pressing into the base 396 is almost impossible and is not intended to be so. It can also be seen here that the lower edge 330 of the thermal conductor 329 extends clearly on the upper side of the base 326 on the left and right sides of the fastening element 331a.

[0056] In the case of the second fastening element 331b, a similarly constructed base area 333b is provided. An additional base area 335b is directly connected to the base area 333b from the middle, with a tapering tip 334b ​​that rises from the middle. The additional base area 335b has a uniform width. The additional base area is in the base 326, and the lower edge of the base area 333b is on the upper side of the additional base area. The additional base area 335b has a small piece extending downward from the base 326, wherein the tapering tip 334b ​​is then connected to the additional base area. The tapering tip 334b ​​is mainly used to press the entire fastening element 331b into the base 326 more easily.

[0057] In the case of the third fastening element 331c, a base area 333c is also provided, which rises from the lower edge 330 of the heat conductor 329. However, the base area is not inclined, but rather is as right-angled as possible. An additional base area 335c of uniform width rises downward from the middle of its lower edge, which leads to a rounded, tapering tip 334c. The area of ​​the lower edge of the base area 333c on the left and right sides of the additional base area 335c is relatively wide again, and can be well supported on the upper side of the base 326 even under force, without being pressed in. Here, the additional base area 335c also passes through the base 326 completely. The rounded tip 334c can have advantages over the oblique tip in terms of pressing in and / or manufacturing as explained at the beginning.

[0058] In the case of the fourth fastening element 331d, a base region 333d with a rounded shape extends downward from the lower edge 330 of the heat conductor 329. Here, too, a transition to an additional base region 335d of the fastening element 331d, that is to say to an additional base region 335d of uniform width, is provided in the middle. A sharp, tapering tip 334d is connected to the additional base region, which is used for insertion into or through the base 326. The rounded shape of the base region 333d may make it easier to manufacture the heat conductor 329 and prevent micro-damage on the lower edge 330 in the transition to the base region 333d.

[0059] Even in Figure 7 The spacing of the tapered tips 334a to d is similar to that in Figures 3 to 6 In practice, the spacing should also be greater than there. In particular, the length of the exposed lower edge 330 of the heat conductor 329 should be similar to Figures 3 to 6 In. That is, from Figure 7It can be seen that in the case of the dimensioning selected here, the spacing between the fastening elements 331a to d is relatively small, so that the resulting increase or widening of the cross section of the heat conductor may have an excessively strong negative impact on the uniform luminous image or uniform heating effect of the heating device 316.

Claims

1. A heating device for an electric furnace, the heating device comprising: - at least one long thermal conductor; - a base, on the upper side of which the thermal conductor is arranged and fixed; - supporting means for said base, in: the heating conductor is designed as a rolled-up flat strip, wherein the rolled-up flat strip has fastening elements arranged at a distance from one another at least on its underside, - the fastening element projects downwards, - the fastening element is pressed into the seat, - the support means supports the base downwards in its outer region and / or along its outer edge, It is characterized in that - the base consists of pressed and / or glued mica material, the fastening element is designed to taper away from the heating conductor in its longitudinal extension and has a tapering free tip, a base region of the fastening element connected to the lower edge of the thermal conductor is provided, the base region having a length in a direction laterally away from the thermal conductor of between 0.1 mm and 2 mm, and A free, tapering tip of the fastening element adjoins the base region, wherein the tapering tip is narrower in an upper, wider region than the smallest width of the base region.

2. The heating device according to claim 1, characterized in that The coefficient of thermal expansion of the base or of the material of the base may deviate from the coefficient of thermal expansion of the heat conductor by a maximum of 10%.

3. The heating device according to claim 2, characterized in that: The coefficient of thermal expansion of the base or of the material of the base up to a temperature of 250° C. deviates from the coefficient of thermal expansion of the heat conductor by a maximum of 10%.

4. The heating device according to claim 1, characterized in that The mica material is bonded mica.

5. The heating device according to claim 1, characterized in that: The base is designed as a plate having a top side on which the at least one elongate heating conductor is arranged.

6. The heating device according to claim 5, characterized in that: The base is designed as a thin plane-parallel plate having a thickness between 0.1 mm and 2 mm.

7. The heating device according to claim 1, characterized in that: In the region of the outer edge of the base, spacers are arranged upward from the upper side of the base in order to maintain a distance from a cooktop plate arranged on the cooktop.

8. The heating device according to claim 1, characterized in that The fastening element is formed integrally from the thermal conductor or is integrally molded onto the thermal conductor.

9. The heating device according to claim 8, characterized in that: The fastening element is formed integrally from the heating conductor or is integrally molded onto the heating conductor and consists of the same continuous flat strip material and projects downwardly from the lower edge of the heating conductor in only one part and in one piece.

10. The heating device according to claim 1, characterized in that The length of the fastening element is 50% to 200% of the height of the thermal conductor or between 1 mm and 6 mm.

11. The heating device according to claim 1, characterized in that: More than half of all the fastening elements are curved away from the heating conductor within their longitudinal extension.

12. The heating device according to claim 1, characterized in that Each fastening element is formed on precisely one single base region provided for this purpose.

13. The heating device according to claim 12, characterized in that: The base region has a width in the direction along the longitudinal direction of the heating conductor which is between 2 mm and 10 mm or between 100% and 400% of the height of the heating conductor.

14. The heating device according to claim 1, characterized in that The base region extends above the base or lies flat on the base.

15. The heating device according to claim 14, characterized in that The base region is pressed onto the base.

16. The heating device according to claim 1, characterized in that The power per unit area of ​​the heat conductor is less than 2.5 W / cm in the area of ​​the heat conductor. 2 .

17. An electric furnace device, comprising at least one heating device according to claim 1, characterized in that: The electric stove device is configured as an electric stovetop or an electric oven.

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