COOKING APPLIANCE WITH A COOKING PLATE AND WITH A HEATING DEVICE THEREUNDER

Abstract

A cooking appliance has a cooking plate for the direct preparation of food products thereon and has a heating device thereunder, wherein the heating device runs parallel to the cooking plate and bears at least partially against the bottom side of the cooking plate. The heating device has a flat carrier disc running parallel to the cooking plate, on the bottom side and top side of which carrier disc there are arranged in each case heating means which in each case substantially cover the carrier disc. Both heating means have in each case a multiplicity of heating conductors to cover the bottom side and top side of the carrier disc. The carrier disc may be composed of micanite, and the heating conductors may be thick-film heating conductors.

Claims

1. A cooking appliance comprising: a cooking plate; and a heating device thereunder, wherein: said heating device runs parallel to said cooking plate and bears at least partially against a bottom side of said cooking plate; said heating device comprises a flat carrier disc running parallel to said cooking plate; on a bottom side and on a top side of said carrier disc, there are arranged in each case heating means which in each case substantially cover said carrier disc; and both said heating means comprise in each case at least one heating conductor.

2. The cooking appliance according to claim 1, wherein said cooking plate is designed for a direct preparation of food products thereon.

3. The cooking appliance according to claim 1, wherein said heating device bears over said full area against said bottom side of said cooking plate.

4. The cooking appliance according to claim 1, wherein said cooking plate is composed of an electrically insulating material.

5. The cooking appliance according to claim 4, wherein said electrically insulating material is from the group: hard glass, glass ceramic, ceramic, and natural stone.

6. The cooking appliance according to claim 1, wherein said cooking appliance comprises a single cooking plate and/or comprises a single heating device.

7. The cooking appliance according to claim 1, wherein said carrier disc is provided with an electrical insulation at least in a region of said heating means or of said heating conductor, and wherein said carrier disc is metallic and composed of a material from the group: steel, high-grade steel, composite materials with aluminum, copper and high-grade steel.

8. The cooking appliance according to claim 1, wherein said carrier disc is composed substantially of micanite.

9. The cooking appliance according to claim 1, wherein said carrier disc is surface-treated or has a surface coating in order to form a smooth and closed surface for an application of said heating conductor.

10. The cooking appliance according to claim 1, wherein said heating means comprises thick-film heating conductors as heating conductors, or are applied in a thick-film process to said carrier disc.

11. The cooking appliance according to claim 10, wherein: connection conductors are provided being applied to said carrier disc; said connection conductors are composed of conductor material with very good electrical conductivity; for each heating means, two electrical connection panels are provided being connected to said connection conductors; and said heating conductors, at their two opposite ends defined by a current flow direction, make contact with said connection conductors.

12. The cooking appliance according to claim 10, wherein: a central region on at least one side of said carrier disc is free from heating conductors; and in said central region, a connection conductor with a small width and large length in relation to said heating conductors is provided in spiral form or in meandering form and forms a heating element.

13. The cooking appliance according to claim 12, wherein a central region of said carrier disc is free on both sides of said carrier disc from heating conductors.

14. The cooking appliance according to claim 1, wherein a surface power density per side of said heating device lies between 0.5 W/cm.sup.2 and 15 W/cm.sup.2.

15. The cooking appliance according to claim 1, wherein said heating means on said top side of said carrier disc are designed for an electrical surface power density that is up to 20% higher than an electrical surface power density of said heating means on said bottom side of said carrier disc.

16. The cooking appliance according to claim 1, wherein said carrier disc comprises, at an outer edge, slots with an extent from said outer edge toward a central region or a central point of said carrier disc.

17. The cooking appliance according to claim 1, wherein a temperature sensor on said heating device is provided.

18. The cooking appliance according to claim 17, wherein said temperature sensor is arranged between said heating device and a bottom side of said cooking plate, or bears directly and immediately against said bottom side of said cooking plate.

19. The cooking appliance according to claim 17, wherein a spacing of said temperature sensor to one said heating conductor is greater than a combined thickness of said cooking plate and of said carrier.

20. The cooking appliance according to claim 1, wherein: said heating device comprises, above said carrier disc or above said heating means on said top side of said carrier disc, an areal cover; and said areal cover bears directly and immediately against a bottom side of said cooking plate.

21. The cooking appliance according to claim 1, wherein: said cooking appliance is, at its top side, formed substantially, by said cooking plate; and said cooking appliance comprises, below said cooking plate, a flat housing which surrounds and accommodates said heating device laterally outwardly and downwardly.

22. The cooking appliance according to claim 21, wherein said housing comprises, at an inside, a thermal insulation which surrounds said heating device laterally outwardly and/or downwardly.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0026] Further advantages and aspects of the invention will emerge from the claims and from the following description of preferred exemplary embodiments of the invention, which are discussed below on the basis of the figures. In the figures:

[0027] FIG. 1 is a sectional illustration through a cooking appliance according to the invention with a cooking plate and with a heating device thereunder;

[0028] FIG. 2 shows a detail of an enlarged sectional illustration of the heating device of the cooking appliance from FIG. 1; and

[0029] FIG. 3 shows a plan view of the top side of the heating device of the cooking appliance from FIG. 1.

DETAILED DESCRIPTION

[0030] FIG. 1 illustrates, in section, a cooking appliance 11 according to the invention, which has a flat form. In plan view, it may be round, in particular circular. Alternatively, in a plan view, it may also have a rectangular or square shape, in particular owing to a simpler and less expensive manufacturing process.

[0031] The cooking appliance 11 has a cooking plate 13 composed of glass ceramic. It may have a thickness of a few millimetres, for example 3 mm to 5 mm. For easier production of a cooking plate 13 of the type composed of glass ceramic, an above-described rectangular or square basic shape may be provided for the cooking appliance 11. A top side 14 of the cooking plate 13 is as smooth as possible, such that, for example, food products as described in the introduction, such as cakes 41, can be prepared or baked directly thereon. A bottom side 15 of the cooking plate 13 may also be smooth, or may alternatively have studs, such as is known for glass ceramic plates for hob plates of hobs.

[0032] Below the cooking plate 13, there is arranged a flat and areal heating device 17, specifically advantageously with a small spacing to the bottom side 15, wherein the heating device bears partially or substantially against the bottom side. A temperature sensor 35 lies on the top of the heating device 17 or on heating means 21 provided on the top side of the heating device 17. The temperature sensor is advantageously a thermocouple as described in the introduction, with connections not illustrated here. The connections are however easy for a person skilled in the art to implement.

[0033] In one embodiment of the invention, it would also be possible for a further intermediate layer, for example with an electrically insulating action, to be provided between the heating device 17 and bottom side 15 of the cooking plate 13. An intermediate layer of the type may for example be composed of a thin micanite disc.

[0034] A thermal insulation 37 is provided below the heating device 17. It may have a thickness from a few millimetres to 1 cm or 2 cm, and may advantageously be composed of fibre-containing or fibre-free insulation material, such as is also known for radiation heating devices in hobs. Alternatively, the thermal insulation may be composed of vermiculite. The thermal insulation 37 is, as can be seen, turned upward at the outer edge, and altogether forms a type of plate or shallow bowl. The top sides of the outer edges advantageously bear against the bottom side 15 of the cooking plate 13, such that good thermal insulation is realized even to the side. Furthermore, the mechanical stability that is required can thereby be achieved.

[0035] In turn, below the thermal insulation 37, there is provided a housing 39, advantageously composed of metal, in particular sheet metal. The housing 39, by means of a housing rim 40 running in encircling fashion at the outside, not only engages over the edge of the thermal insulation 37 but also extends upward beyond an outer edge of the cooking plate 13, and bears with a small projecting length against the top side 14 of the cooking plate 13. By means of this embracing action, the entire cooking appliance 11 can be easily closed and also easily opened for repair purposes.

[0036] Not illustrated in FIG. 1 is an electrical mains connection for the heating device 17 and possibly a controller, in particular an on/off switch and possibly a power adjustment means for the heating device 17. These are however easy for a person skilled in the art to implement, and may have a switch mounted for example on the outside on the housing 39 or the housing rim 40. This may be a so-called energy regulator, such as is known for example from U.S. Pat. No. 6,211,582. Alternatively, it would be necessary, by means of a particular distribution of the heating means on the heating device 17, to create the possibility of activating the heating means in different power stages by means of different parallel connection and/or series connection configurations. The outlay would however then greatly increase.

[0037] The sectional illustration of FIG. 2 illustrates an enlarged detail of the heating device 17. The carrier disc 19 is advantageously composed of the micanite discussed in the introduction. The micanite is particularly advantageously treated, at least on its outer side, in order to permit the subsequent application of heating means 21 to the top side and heating means 23 to the bottom side. The micanite may however also be untreated. The heating means 21 and 23 are advantageously applied by means of thick-film processes, as discussed in the introduction. This means that they are thick-film heating conductors composed of a suitable material, in particular a material as described above. Not illustrated in FIG. 2, but easily conceivable, are electrical connections for the heating means 21 and 23, as will be discussed in somewhat more detail below.

[0038] FIG. 3 illustrates a plan view of the heating means 21 on the top side of the carrier disc 19 of the heating device 17. For the heating means 21, connections 24 are provided on opposite outer sides of the carrier disc 19, that is to say in this case two connections to the left and to the right. From the connections 24, conductor tracks 25 extend toward one another or toward the central region. In turn, further conductor tracks extend in a circumferential direction from the specific conductor tracks 25, forming a total of six encircling conductor tracks 25. The encircling conductor tracks 25 are overlapped by heating conductors 28 of the heating means 21, wherein all of the heating conductors 28 have a circular segment shape with equal length in a radial direction, merely different widths in the circumferential direction and different curvature. This means that the heating conductors 28 each form circular ring segments, which partially or possibly even completely overlap the conductor tracks 25 running in a circumferential direction, or are covered by the conductor tracks.

[0039] Furthermore, separating troughs 30 are provided which run in a radial direction and over which no material of the heating conductors 28 extends. The separating troughs are also overlapped in the circumferential direction by only every second conductor track 25. The separating troughs 30 begin at an innermost ring of the conductor track 25. The conductor tracks 25 and the heating conductors 28 may be produced in a thick-film process, in particular produced in a screen printing process from respectively suitable conductor pastes, which are then fired.

[0040] It important that the radial spacing of the circular encircling conductor tracks 25 is equal in each case. The current flow direction thus runs along the radial direction. Here, the width of the heating conductors 28 in the direction perpendicular to the current flow direction varies somewhat, in particular in the case of the radially inner heating conductors 28. This however can either be compensated by means of a special geometry or width of the separating troughs 30, or alternatively one accepts a somewhat uneven current density and thus heat distribution.

[0041] The special interconnection of the heating conductors 28 by means of the conductor tracks 25 is easy to see and can be easily understood from FIG. 3.

[0042] In a central region of the heating device 17 or of the carrier disc 19, there is provided a central heating element 26. This is formed by a section of the conductor track 25 with a meandering profile, in order to utilize the circular central area as effectively as possible. Even if the material of the conductor track 25, as has been described in the introduction, normally and advantageously exhibits such good electrical conductivity that it is indeed highly suitable as a conductor track in the case of a normal length, it is possible by means of the visibly very large length of the central heating element 26 for heat generation to be achieved here too.

[0043] The heating means 23 on the bottom side of the carrier disc 19 are advantageously of similar form to the heating means 21 on the top side as per FIG. 3, in particular of identical form. It is however particularly advantageous for the arrangement there to be rotationally offset slightly in relation to that of the heating means 21 on the top side, for example by 90. The connections thereof would thus be in each case between the connections 24 corresponding to FIG. 3. The circular-ring-shaped conductor tracks 25 running in the circumferential direction may, on the bottom side, be provided at exactly the same locations. The separating troughs could also be offset, by half of one spacing, between two separating troughs on the top side, such that a gap in the heat generation for the cooking plate 13 is avoided. Accordingly, the heating means would be rotationally offset with respect to one another in each case by approximately 78.75. The heating conductors could similarly also be rotationally offset with respect to one another slightly in the radial direction.

[0044] By means of a substantially symmetrical and identical design of the heating means 21 on the top side and the heating means 23 on the bottom side, including the respective central heating elements 26, a heating power on the top side of the heating device 17 and on the bottom side 17 can be achieved which is identical in each case. However, should a somewhat different heating power be desired, in particular a greater heating power for the heating means 21 on the top side of the carrier disc 19, in order to allow for the greater release of heat upward to the cooking plate 13, for the temperature conditions that ultimately take effect at the heating device 17, the heating means 21 on the top side may generate 5% to 20% or even 30% more power. Then, an above-described bending of the heating device owing to different heating at one of the sides, in particular at the bottom side, can be reduced or prevented entirely. This however does not have to be provided, and must be implemented substantially in a manner dependent on the type of construction.