HEATING DEVICE, COOKING APPLIANCE WITH A HEATING DEVICE, AND METHOD FOR PRODUCING A HEATING ELEMENT

Abstract

A heating device has a sheet-like heating element and a holding device for the heating element, wherein the heating element is held along an outer edge on the holding device and, by way of at least 70% of its surface area, runs freely within the holding device. The heating element has a weave which at least partially contains heating conductor material. Therefore, warp threads can advantageously be composed of electrically conductive heating conductor material, and weft threads can be composed of carbon fibre or ceramic fibres. The heating element can be centrally supported or be provided with a structuring over its surface area, which structuring stabilizes the heating element, for example can be corrugated.

Claims

1. A heating device comprising: a sheet-like heating element comprising an outer edge and with a holding device for said heating element, wherein: said heating element is held along said outer edge on said holding device and, by way of at least 70% of a surface area of said heating element, runs freely between said holding device or within said holding device; said heating element comprises a lattice or a weave; and said lattice or said weave at least partially comprises a heating conductor material.

2. The heating device according to claim 1, wherein said heating element is held at least at holding points of said holding device.

3. The heating device according to claim 2, wherein said holding points are along a holding line.

4. The heating device according to claim 1, wherein said heating element is three-dimensionally structured for mechanical stabilization in a perpendicular direction or in a direction perpendicular and parallel to opposite outer edges of said heating element.

5. The heating device according to claim 1, wherein said heating element has a corrugated, sinusoidal or sawtooth-like structure or trench-like or crater-like stabilizing embossed portions.

6. The heating device according to claim 5, wherein said embossed portions are not directed or do not have an orientation.

7. The heating device according to claim 1, wherein a sheet-like reflector is provided in a direction away from a heating direction of said heating element.

8. The heating device according to claim 7, wherein said reflector is held on said holding device beneath said heating element.

9. The heating device according to claim 1, wherein said holding device is formed in an annularly circumferential manner and substantially bounds a lateral extent of said heating device, wherein said heating element is arranged and runs within said lateral extent of said heating device.

10. The heating device according to claim 1, wherein said heating element, as viewed from a heating direction, has a rectangular shape with two connection contact-making arrangements on opposite outer sides.

11. The heating device according to claim 1, wherein: two opposite outer edges of said heating element comprising said lattice or said weave are connected to contact strips; and said contact strips are composed of electrically conductive strip material.

12. The heating device according to claim 11, wherein said contact strips are mechanically and electrically connected to said heating element as a composite in a continuous process.

13. The heating device according to claim 12, wherein said contact strips are mechanically and electrically connected to said heating element by a welding process.

14. The heating device according to claim 1, wherein said lattice or said weave of said heating element comprises warp wires or warp threads and weft wires or weft threads.

15. The heating device according to claim 14, wherein only said warp wires or said warp threads are electrically conductive for said heating element function.

16. The heating device according to claim 1, wherein said heating element is in the form of a lattice with wires or threads, wherein said wires or said threads run substantially at right angles.

17. The heating device according to claim 1, wherein said heating element comprises heating element sections and intermediate areas which run between said heating element sections.

18. The heating device according to claim 17, wherein a surface area proportion of said intermediate areas is greater than a surface area proportion of said heating element sections.

19. The heating device according to claim 18, wherein a surface area proportion of said intermediate areas is greater than a surface area proportion of said heating element sections by a factor of 2 to 20.

20. The heating device according to claim 1, wherein said heating element is at least partially coated with a catalytically active material.

21. The heating device according to claim 20, wherein said electrically conductive heating element sections, are at least partially coated with said catalytically active material.

22. The heating device according to claim 17, wherein said wires or said heating element sections are directly composed of catalyst material.

23. A cooking appliance in the form of a hob, comprising a hob plate and at least one heating device according to claim 1, wherein at least one said heating device is arranged beneath said hob plate.

24. A cooking appliance in the form of an oven, comprising an oven muffle and at least one heating device according to claim 1, wherein at least one said heating device is arranged in said oven muffle.

25. The cooking appliance according to claim 24, wherein said heating device is arranged in said oven muffle as a heating body providing heat from a bottom said oven muffle.

26. The cooking appliance according to claim 24, wherein said heating device is arranged in said oven muffle as a heating body providing heat from an upper side of said oven muffle.

27. The cooking appliance according to claim 24, wherein one said heating element is provided with catalytically active material and is provided on an oven muffle.

28. The cooking appliance according to claim 27, wherein said heating element being provided with catalytically active material is provided close to a fan of a hot air oven.

29. A method for producing one said heating element for said heating device according to claim 1, comprising: forming a strip from said lattice or said weave comprising heating element sections and a heating element function being of sheet-like design; folding two opposite outer edges of said strip composed of said lattice or said weave into contact strips composed of electrically conductive strip material in a continuous process; mechanically and electrically connecting said contact strips to said strip comprising said lattice or said weave as composite in a continuous process; and cutting said composite, as heating element, to a specific length.

30. The method according to claim 29, wherein solid or braided electrical connection lines are attached to one said contact strip in each case.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0034] Exemplary embodiments of the invention are schematically illustrated in the drawings and will be explained in greater detail in the text which follows. In the drawing:

[0035] FIG. 1 shows a greatly enlarged view of a weave with warp threads which are composed of heating conductor material and with weft threads which are composed of electrically insulating fibres;

[0036] FIG. 2 shows one possible refinement of a hob having a heating device with a heating element according to the invention;

[0037] FIG. 3 shows a schematic apparatus for producing a heating element according to the invention from a weave according to FIG. 1;

[0038] FIG. 4 shows a refinement of a heating element according to the invention comprising a weave according to FIG. 1 with a corrugated structure;

[0039] FIGS. 5 and 6 show different plan views of lattice-like heating elements with wide contact strips at the sides;

[0040] FIG. 7 shows a schematically illustrated possible tensioned arrangement of a heating element according to the invention in a heating device;

[0041] FIG. 8 is a simplified illustration of an oven having heating devices according to the invention as a heating body providing heat from the bottom and a heating body providing heat from the top; and

[0042] FIG. 9 is a schematic illustration of a further oven having a heating device according to the invention together with a catalyst function on a fan for a hot-air function.

DETAILED DESCRIPTION

[0043] FIG. 1 illustrates a greatly enlarged view of a weave 10 which consists of warp threads and weft threads 14. Here, neither thread is designed to run in a completely rectilinear manner, this providing good structural cohesion of the weave 10. The warp threads 13 are composed of heating conductor material, for example of alloys containing nickel and chromium or containing iron, chromium and aluminium, as mentioned at the outset. The warp threads 13 are advantageously in the form of fine wires.

[0044] The weft threads 14 can, in principle, also have a heating element function, but they are advantageously electrically insulating and primarily intended to provide support and mechanical strength for the weave 10. The weft threads are composed of electrically insulating and accordingly mechanically strong and also primarily temperature-resistant material, advantageously ceramic fibres, basalt fibres, carbon fibres or aramid fibres, depending on the maximum temperature and the field of use of a heating element. In this case, the fibres are particularly advantageously multifilaments.

[0045] A thickness or a diameter of the warp threads and/or of the weft threads can be dimensioned depending on the application, for example can lie between 0.05 mm and 1 mm, advantageously between 0.1 mm and 0.5 mm.

[0046] FIG. 2 shows, by way of example, a possible refinement of a heating device 20 according to the invention having a completed heating element 11 in which a weave 10 is processed, as will be discussed further below. The sheet-like heating element 11 is arranged on a preferably rectangular holding edge which runs on the outside, advantageously clamped in or inserted into slots and held therein. The holding edge 21 can, just like a central holder 23 in the centre for the heating element 11, be composed of correspondingly temperature-resistant and highly thermally-insulating material, for example pressed vermiculite or a similar material, as is customarily used for radiant heating devices in hobs. The holding edge 21 and the central holder 23 stand on an insulating substrate 24 which is composed of the same material. Under certain circumstances, the parts can even be at least partially integrally produced with one another. A reflector 26, which can also be held by the central holder 23 and the holding edge 21, runs beneath the heating element 11. The reflector can run in a planar manner or can respectively be slightly curved by means of a sagging portion in order to possibly achieve a better reflection effect.

[0047] The heating device 20 according to the invention is installed into a hob 30 according to the invention as a heating arrangement, as is illustrated in FIG. 2. The hob 30 has a hob plate 32 beneath which or pressed against the bottom side of which the heating device 20 is arranged. As in the case of glass-ceramic hobs with radiant heating which are known per se, the heat which is generated by the heating device 20 or the heating element 11 is emitted upwards through the hob plate 32 into a pot which is positioned on the hob plate. However, this substantially corresponds to an analogous equivalent of a, for example, abovementioned radiant heating device and for this reason does not need to be explained any further.

[0048] FIG. 3 shows how a completed heating element 11 according to the invention is produced from a weave 10 according to FIG. 1 in an apparatus 34. The weave 10 is cut into elongate strips and is present in this form and is inserted into the apparatus 34. In the process, the electrically insulating weft threads run in the passage direction and the warp threads with the heating element function run in a direction transverse to the passage direction. Contact strips 15a and 15b which have already been partially folded are then possibly guided to the outer sides and folded one onto the other by folding means, not illustrated, wherein the side edges of the weave 10 are folded into the folded contact strips 15a and 15b. Here, the overlap can be between 2 mm and 20 mm, advantageously 5 mm to 15 mm.

[0049] After the folding-in operation, a roll seam welding device 17a is provided on the left-hand side and a roll seam welding device 17b is provided on the right-hand side. These roll seam welding devices weld the weave 10 or the warp threads 13 which are composed of metal to the contact strips 15a and 15b, wherein, under certain circumstances, they can also take over the folding-in operation. Firstly a secure and stabilizing mechanical connection and secondly an electrical connection are established owing to the welding.

[0050] The completed desired heating elements 11 are then cut to the appropriate length by means of a cutting device 18. In this case, the warp threads with the heating element function run from one contact strip 15a to the other contact strip 15b.

[0051] The FIG. 3 further schematically illustrates how electrical connections 27 can be attached to the contact strips 15a and 15b, for example as short connection wires. To this end, they can be welded on. As an alternative, fixed contact plugs could also be attached or welded on as contact shoes or flat insertion lugs.

[0052] It is easily conceivable that the heating element 11 according to FIG. 3 has a rectangular shape, for example a square shape. The shape of a parallelogram would also be possible in principle, but practical applications for this are rather rare.

[0053] FIG. 4 shows, by way of example, a further possible refinement of a heating element 11 according to the invention similar to that which is obtained at the end of the method according to FIG. 3. Here, a corrugated or trench-like structure is inserted into the heating element 11 or into the weave 10 comprising warp threads 13 and weft threads 14, and primarily into the lateral contact strips 15a and 15b. The structure serves to stabilize the heating element 11 overall, specifically primarily the weave 10. Instead of the trenches which run transverse to the contact strips 15a and 15b, obliquely running or longitudinally running trenches or similar structures could also be inserted, for example also crossed-over structures in the manner of a known diamond pattern. Similarly, more trenches which are arranged closer together could be provided, so that an abovementioned corrugated structure is produced. The trenches 10 could also be modified such that they are almost pointed or bent as a kind of abovementioned sawtooth. In a yet further modification, the structures could be inserted in both directions, for example alternately.

[0054] In a yet further modification, individual relatively small regions could be impressed in a distributed manner, for example as craters or raised portions.

[0055] FIG. 5 illustrates a plan view of a refinement of a further heating element 111 which is in the form of a lattice or is lattice-like. A centrally arranged lattice structure 110 replaces, as it were, the weave 10 of FIGS. 1 and 3. A strip of corresponding width is folded in between two contact strips 115a and 115b, welded and therefore mechanically and electrically connected to the contact strips, just like the weave 10 as has been described above. Here, the lattice 110 has been produced by etching from a thin foil of a heating conductor material. As an alternative, it could be stamped or lasered. Current flows from one contact strip 115a to the other contact strip 115b here too. To this end, the pattern of the structure in the direction of the longitudinal direction of the contact strips 115 is advantageously regular, it being possible for this to apply particularly advantageously very generally for a heating element according to the invention.

[0056] FIG. 6 illustrates a further refinement of a heating element 211 according to the invention. This heating element is also of lattice-like design, but with a different lattice to that according to FIG. 5. Elongate heating element sections are formed in the manner of waves which are connected to one another by webs. A lattice 210 of this kind is produced advantageously in the manner described above for the lattice 110 of FIG. 5. Furthermore, this lattice 210 is also folded into two contact strips 215a and 215b in the described manner for the purpose of mechanical and electrical connection.

[0057] FIG. 7 shows a modification of the illustration of FIG. 2 with a heating device 320 which is permanently tensioned in a special way. In the left-hand region of a holding edge 321, an electrical connection 327 runs downwards from the left-hand edge of the heating element 311, the electrical connection also effecting fastening, possibly in addition to holding at the holding edge 321. In the right-hand region, an electrical connection 327 likewise runs downwards. However, a tensioning weight 329 is, as it were, symbolically arranged at this electrical connection, the tensioning weight pulling the right-hand-side connection 327 downwards as it were. Owing to a spring 328 which is arranged to the left of the connection 327, a certain mechanical stress is additionally generated as tension which pulls the heating element 311 smooth as far as possible. A form of the heating element 311 which is as flat and planar as possible can be achieved in this way.

[0058] FIG. 8 illustrates, as a further exemplary cooking appliance according to the invention in addition to a hob, an oven 36 with an oven muffle 37 and an oven door 38. A heating element 11 is provided, by way of example integrally, beneath the oven muffle 37 as a heating body providing heat from the bottom, specifically beneath a glass-ceramic plate 39 which, once again, is particularly transmissive to thermal radiation as in the case of the hob 30 of FIG. 2. The exact holding device for the heating element 11 is not illustrated here, but can correspond to FIG. 1 or 7 for example. It can also be seen that this lower heating element 11 can be relatively large.

[0059] The heating body providing heating from the top is provided in the upper region of the oven muffle 37 or below a muffle ceiling, by way of example by combining two narrow heating elements 11.

[0060] Both the heating body for providing heat from the top and the heating body for providing heat from the bottom can be of integral design or comprise an arrangement of rectangular heating elements which have identical or different lateral and longitudinal dimensions. Therefore, it is possible to set both the heat from the top and the heat from the bottom partially differently for the purpose of uniformly heating or browning the item being cooked, roasted or grilled.

[0061] FIG. 8 illustrates a hot-air function for the oven 36 from FIG. 8, in a separate manner merely for the purpose of better understanding. A fan 41 which is provided for this purpose is arranged in the rear region of the oven muffle 37. A heating element 11 is arranged in the air path, advantageously behind the fan for thermal reasons, the heating element heating up the air blown through or conveyed through for the hot-air function of the oven 36. In addition, the heating element 11 can be at least partially coated with a catalytically active material, advantageously completely coated, here. Therefore, a novel directly heated catalyst heating element for an oven can be provided, as a result of which, for example, the ambient air in an oven 36 of this kind can be purified for the purpose of reducing impurities and unpleasant odors.

[0062] A holding device for the heating element 11 is not illustrated in any detail here either, but is easily conceivable. For example, the two contact strips 15 on the sides are, in turn, primarily also suitable for fastening the heating element 11.