Heating device

Abstract

A heating device has a support and a heating element arranged on it, the heating element having two electrical terminals and a multiplicity of heating conductors that are electrically connected to one another. Starting from the one terminal, the heating element is divided into a number of heating conductors parallel to one another and in series one behind the other toward the second terminal. In this case, at least three heating conductors are connected in parallel next to one another and at least three heating conductors are connected in series one behind the other. Series-connected heating conductor groups can be formed, heating conductors being parallel within a heating conductor group.

Claims

1. A heating device comprising: a support and a heating element arranged on said support; said heating element comprising a first electrical terminal and a second electrical terminal; and said heating element comprising a multiplicity of heating conductors that are electrically connected to one another, and wherein starting from said first terminal, said heating element is divided into a number of heating conductor groups in series one behind the other, wherein at least three said heating conductor groups are connected in series to one another between said first terminal and said second terminal, wherein in at least one said heating conductor group, at least three said heating conductors are provided, connected in parallel to one another, and wherein said heating element is divided into a number of said heating conductor groups with different cross-sectional areas of said respective heating conductors, so that within one said heating conductor group all of said heating conductors have the same cross-sectional area.

2. The heating device according to claim 1, wherein an electrical current density at each point of said heating element differs by a maximum of 25%.

3. The heating device according to claim 2, wherein said electrical current density at each point of said heating element is the same.

4. The heating device according to claim 1, wherein said support has a surface area and said heating conductors cover or enclose between 80% and 90% of said surface area of said support, free regions of said support without heating conductors being provided between said heating conductors.

5. The heating device according to claim 4, wherein adjacent of said free regions are separated from one another by heating conductors.

6. The heating device according to claim 1, wherein near an outer edge of said support, an edge region is free from heating conductors.

7. The heating device according to claim 6, wherein near said outer edge of said support, an edge region with a width between 1 cm and a maximum of 3 cm is free from heating conductors.

8. The heating device according to claim 6, wherein near said outer edge of said support, an edge region with a width of at least 5% of a maximum width of said support is free from heating conductors.

9. The heating device according to claim 1, wherein said heating element is divided into a number of said heating conductor groups of different widths of said heating conductors, so that within one said heating conductor group all of said heating conductors have the same width.

10. The heating device according to claim 9, wherein said heating element is divided into three said heating conductor groups to six said heating conductor groups of different widths of said heating conductors, so that within one said heating conductor group all of said heating conductors have the same width.

11. The heating device according to claim 9, wherein said heating conductors of said heating conductor group have a width that is an integral multiple of a width of a next-narrower heating conductor group.

12. The heating device according to claim 11, wherein said heating conductors of said heating conductor group have a width that is two or three times a width of said next-narrower heating conductor group.

13. The heating device according to claim 1, wherein said heating element is divided into three said heating conductor groups to six said heating conductor groups with different cross-sectional areas of said respective heating conductors, so that within one said heating conductor group all of said heating conductors have the same cross-sectional area.

14. The heating device according to claim 1, wherein said heating conductors of said heating conductor group have a cross-sectional area that is an integral multiple of a cross-sectional area of a next-narrower heating conductor group.

15. The heating device according to claim 14, wherein said heating conductors of said heating conductor group have a cross-sectional area that is two or three times the cross-sectional area of said next-narrower heating conductor group.

16. The heating device according to claim 1, wherein an arrangement of said heating conductors from said first terminal to said branching into a heating conductor group with the most heating conductors is mirror-symmetrical to an arrangement of said heating conductors towards said second terminal.

17. The heating device according to claim 1, wherein an arrangement of said heating conductors from said first terminal to said branching into a heating conductor group with the most heating conductors is point-symmetrical to an arrangement of said heating conductors towards said second terminal.

18. The heating device according to claim 1, wherein heating conductors of a number of said heating conductor groups run parallel to one another within said heating conductor group.

19. The heating device according to claim 18, wherein all of said heating conductors of all of said heating conductor groups run parallel to one another.

20. The heating device according to claim 1, wherein a thickness of all said heating conductors is the same and said heating conductors have a flat rectangular cross-section.

21. The heating device according to claim 1, wherein a width of said heating conductors is 10 times to 30 times greater than their thickness, said heating conductors being divided into a number of different ones of said heating conductor groups of the same widths or cross-sectional areas respectively within said heating conductor group.

22. The heating device according to claim 21, wherein one said heating conductor group has a width or cross-sectional area that is an integral multiple of that of a heating conductor group with a next-narrower width or cross-sectional area.

23. The heating device according to claim 22, wherein said heating conductor group has a width or cross-sectional area that is two or three times said width or said cross-sectional area of said heating conductor group with said next-narrower width or said next-narrower cross-sectional area.

24. The heating device according to claim 1, wherein said heating element is applied to a support of metal or ceramic by a thick-film technique.

25. The heating device according to claim 1, wherein said support has a geometrical basic form being round or rectangular.

26. The heating device according to claim 1, wherein said support is flat or planar.

27. The heating device according to claim 1, wherein said support is curved or convex with said heating element being arranged on its outer side.

28. The heating device according to claim 1, wherein at least one said terminal is arranged near an outer edge of said support.

29. The heating device according to claim 28, wherein both said terminals are arranged next to one another and near said outer edge of said support.

30. A heating device comprising: a support and a heating element arranged on said support; said heating element comprising a first electrical terminal and a second electrical terminal; and said heating element comprising a multiplicity of heating conductors that are electrically connected to one another, and wherein: starting from said first terminal, said heating element is divided into a number of heating conductor groups in series one behind the other, at least three said heating conductor groups are connected in series to one another between said first terminal and said second terminal, in at least one said heating conductor group, at least three said heating conductors are provided, connected in parallel to one another, and starting from said first terminal, said heating element at first branches step by step increasingly into more of said heating conductors, said heating conductors then are made to merge again step by step towards said second terminal.

31. The heating device according to claim 30, wherein said support has a geometrical basic form being round or rectangular.

32. The heating device according to claim 30, wherein heating conductors of a number of said heating conductor groups run parallel to one another within said heating conductor group.

33. A heating device comprising: a support and a heating element arranged on said support; said heating element comprising a first electrical terminal and a second electrical terminal; and said heating element comprising a multiplicity of heating conductors that are electrically connected to one another, and wherein: starting from said first terminal, said heating element is divided into a number of heating conductor groups in series one behind the other, at least three said heating conductor groups are connected in series to one another between said first terminal and said second terminal, in at least one said heating conductor group, at least three said heating conductors are provided, connected in parallel to one another, and two or three said heating conductors are always connected to one another in a branching region, at least one said heating conductor running into said branching region and at least two said heating conductors running out of said branching region with a smaller width or smaller cross-sectional area.

34. The heating device according to claim 33, wherein said width of said heating conductor running into said branching region is the same as a summated width of said heating conductors running out of said branching region.

35. The heating device according to claim 33, wherein said cross-sectional area of said heating conductor running into said branching region corresponds to a summated cross-sectional area of said heating conductors running out of said branching region.

36. The heating device according to claim 33, wherein, in said branching region, a sheet-like electrically conducting material is applied under said running-in and said running-out heating conductors or on said running-in or said running-out heating conductors in such a way that said branching itself lies in said region of said conducting material and, outside said conducting material, said heating conductors, each considered on their own, have a constant width or cross-sectional area or have no change in their width or cross-sectional area.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

(1) Exemplary embodiments of the invention are illustrated schematically in the drawings and are explained in greater detail below. In the drawings:

(2) FIG. 1 shows a plan view of a schematically represented heating device according to the invention with a round support and a multiply branched heating element;

(3) FIG. 2 shows an alternative heating device with an elongated rectangular support and a multiply branched heating element;

(4) FIG. 3 shows a modification of a heating device similar to FIG. 1 with a round support, on which a symmetrical heating conductor structure is applied, with terminals lying directly next to one another;

(5) FIG. 4 shows a further alternative configuration of a heating device with a central terminal in a middle region and an annular terminal running around the outside;

(6) FIG. 5 shows a schematically simplified representation, illustrating how in a way similar to FIG. 1 the heating conductors of a heating element geometrically split into various heating conductor groups; and

(7) FIG. 6 shows a further alternative configuration of a heating device.

DETAILED DESCRIPTION

(8) In FIG. 1, a heating device 11 in a first configuration is shown in a simplified form in plan view. The heating device 11 has an elongatedly oval support 13, for example of ceramic or insulating material, and is in particular flat or planar. The support 13 has a support edge 14 and a peripheral edge region 15, which is largely free.

(9) Provided on the support, on top and underneath, are terminals 17a and 17b, from which there extends in each case a supply lead 18a and 18b. This may be a cable or some other conductor.

(10) Between the terminals 17a and 17b, a heating element 20 runs on the support 13 as a resistance heating element, advantageously applied by the thick-film technique or as a thick-film heating element. This is known to a person skilled in the art and need not be explained in any more detail here.

(11) The heating element 20 is multiply branched into a multiplicity of heating conductors 21, which are then connected in parallel with one another and in series one behind the other. With each branching in a branching region, the heating conductors 21 become thinner, in particular the width of a heating conductor at the branching dividing as it were into the outgoing narrower heating conductors. Consequently, the summated width of the heating conductors in one heating conductor group, in which all of the heating conductors have the same width, may as it were be the same as that of the heating conductors of another heating conductor group. From the terminals 17a and 17b there respectively extend four heating conductors 21, or here the heating element 20 in each case branches into four. These four heating conductors 21 are then in turn respectively branched twice, with then subsequent renewed double branching. Altogether, there are then sixteen heating conductors in parallel in the heating conductor group with the smallest width of the heating conductors. Towards the other heating conductor 17b, the heating conductors 21 merge again, so that altogether a symmetrical structure is obtained in relation to an axis of symmetry exactly between the terminals 17a and 17b.

(12) It can be well imagined on the basis of FIG. 1 that, with heating conductors 21, the main surface area of the support 13 is covered for uniform heating, without every part of the area of the support 13 being covered. Between the heating conductors 21 there are in each case free regions 22, which are elongated and, depending on the number of branchings delimiting them, multiply form irregular quadrangles. The branching regions 23 are in each case differently formed; in particular, they in fact comprise double, triple or even quadruple branches.

(13) In FIG. 2, an alternative heating device 111 is represented, comprising a support 113, which in particular is formed as elongated, in particular elongatedly rectangular. Two terminals 117a and 117b are provided at the most remote end regions of the support 113. From the terminals 117a and 117b there respectively extends a heating element 120 of a single width, and then in three successive branching regions 123 it in each case branches twice. In a middle region of the heating device 111, eight parallel and relatively narrow heating conductors 121 are then provided. They form a heating conductor group. The next and next-wider heating conductor group has respectively to the left and right thereof four parallel heating conductors; the next-wider heating conductor group in turn has respectively to the left and right thereof two parallel-connected heating conductors.

(14) It can be seen particularly well from FIG. 2 that here, depending on which portion is considered, altogether a number of heating conductors are connected in series and in each case also a number of heating conductors are connected in parallel. It is akin to a series connection of seven heating conductors each time and a parallel connection of a maximum of eight heating conductors, that is in the middle region. Here, too, it can be seen that, on the way from the left terminal 117b to the right terminal 117a, the summated width of the heating conductors remains substantially constant.

(15) In FIG. 3, a further alternative heating device 211 is represented, comprising in turn an approximately round support 213. Two terminals 217a and 217b are provided here as zones and are very close to one another in the edge region 215. From the terminals 217a and 217b, first there extend in each case two heating conductors, which then very quickly branch in each case into two further heating conductors. These then branch once again into two heating conductors, so that here, too, in the narrowest heating conductor group there are sixteen heating conductors. As a result of the merging of all of the heating conductors at the end of the support 213 remote from the terminals 217a and 217b, here there is as it were a series connection of two split regions similar to FIG. 2, just on a differently formed support 213. In the case of this configuration of FIG. 3, it can also be easily imagined how the two terminals 217a and 217b could be electrically connected together and, at the uppermost branching region 223, altogether a further electrical connection could then take place in a way similar to in the case of FIG. 1.

(16) FIG. 3 also shows generally how over the path of the heating element 220 between the terminals 217a and 217b, after a splitting or branching there may be a merging and then again however a branching. In the case of complex formed paths, this may also be multiply repeated.

(17) In the case of the again further alternative configuration of a heating device 311 corresponding to FIG. 4, a number of heating conductors extend from a central terminal 317a outwards in a radial direction onto a circular support 313, to be precise in each case in one of six segments of a circle. They then each branch twice into two. The width of the segments of a circle that are covered by these heating conductors, or the angle covered by them, may vary. Here, there are for example six segments of a circle, so that 48 narrow heating conductors arrive at the terminal 317b.

(18) In FIG. 5 it is shown in a simplified and very schematic form how, coming from the left, at a heating element 420 a very wide heating conductor 421 goes into a first branching region 423. There, it branches into two narrower heating conductors, the summated width of which however corresponds exactly to the width of the wide heating conductor 421. In order however not to have any abruptly changing current densities, pinch effects or shortening effects in the branching region, conducting material 425 with good electrical conduction is in fact provided here in the manner of a zone, preferably rectangular. Advantageously, this conducting material 425 is applied directly to a support 413 lying under it, alternatively to its electrically insulated surface. The electrical conductivity of the conducting material 425 is a number of times greater than that of the material of the heating element 420, for example five to ten times as great. It is thus possible that the very wide heating conductor 421 comes from the left and runs into the first branching region 423. From the branching region 423, and consequently away from the conducting material 425, there extend two narrower heating conductors 421, which on account of the same summated width produce the same heating output, but as it were distributed over a greater surface area, because, that is, they also heat a region respectively to the left and right of the heating conductors. It can also be seen that, as a result of the conducting material 425 used, the path of the heating conductors in the branching region 423 in itself is irrelevant, only the branching or splitting is of importance. The heating conductors 421 should in each case extend away from the conducting material 425 in a straight line, that is to say as it were substantially at right angles to its edge. It can also be seen from FIG. 5 that the zones with conducting material 425 become increasingly smaller, but, for that, a number are as it were in parallel next to one another.

(19) In yet a further alternative configuration of a heating device 511 according to FIG. 6, the support 513 is rectangular. Terminals 517a and 517b lie in opposite corners. Shown here is a form of a heating element 520 in which the heating element is divided into heating conductors 521 in such a way that in each case a heating conductor 521 branches into two further heating conductors or two heating conductors 521 are then made to merge into one heating conductor. Thus, along a strand there are five branchings 523 with dividing and five branchings 523 with merging of the heating conductors 521. For reasons of overall clarity, in FIG. 6 all of the heating conductors are shown with approximately the same widths. However, this should not be so in reality; instead, the width of a heating conductor 521 should half each time it branches into two heating conductors 521. In view of the density of the coverage with heating conductors in the case of the heating device 511 according to FIG. 6, this cannot however be shown. Alternatively, with the width remaining the same, the thickness could half, then FIG. 6 would be exactly correct.

(20) It can be seen well from FIG. 6 that there is not in fact very dense coverage of the surface area of the support 513 in the edge regions, in particular in the vicinity of the terminals 517. Here, the free regions 522 are also relatively wide near the corner regions with the terminals 517, but then become very narrow, in particular in the middle region with the narrowest heating conductors 521. Here there is a very dense coverage with narrow heating conductors 521 and with narrow free regions 522.

(21) Here, all of the supports are formed as flat or planar. It can however easily be imagined that a support also has a curved surface, advantageously convexly curved. The surface may however also be complexly formed and provided with heating conductors. Branchings and mergings also allow a complex three-dimensional surface to be covered.

(22) FIGS. 2 and 3 show mirror-symmetrical configurations of the heating conductors. FIGS. 4 and 6 show point-symmetrical configurations of the heating conductors.