GB2114829A

GB2114829A - Control means for heating elements in a cooker hob

Info

Publication number: GB2114829A
Application number: GB08302911A
Authority: GB
Inventors: Dieter Schweig; Walter Bredel; Norbert Schenetin; Helmut Waigand
Original assignee: Individual
Current assignee: Individual
Priority date: 1982-02-10
Filing date: 1983-02-03
Publication date: 1983-08-24
Also published as: IT1161564B; GB2114829B; CH666154A5; NL8300507A; IT8319466A1; SE8300599L; ATA13583A; IT8319466A0; SE456962B; FR2521384B1; FR2521384A1; SE8300599D0; GB8302911D0; AT399976B

Abstract

A circuit arrangement for heating elements in a cooker hob with at least two individual cooking regions (Ha, Hb, H'b, Hz) with a respective input for an electronic control device for the production of variable heating power, comprises control means whereby the individual cooking regions are usable together by being connected together, in particular for elongate cooking vessels. The current paths for the heating elements associated with the individual cooking regions are switchable through a switching element (SK) (Fig. 5) in such a manner that the heating elements of the individual cooking regions are selectably switched in a first switching position of SK to a respective heating power control device (S3, P3; S4, P4, Fig. 5) or in a second switch position together to one of these heating power control devices (S3, R3) while the further heating power control devices (S4, P4) are separated from their associated heating element. The microprocessor (???P) provides duty cycle regulation of the heating elements via relays (K3-K8, Fig. 5). <IMAGE>

Description

SPECIFICATION Control means for heating elements in a cooker hob The present invention relates to control means for heating elements in a cooker hob, and has particular reference to a hob with at least two individual cooking regions with a respective input point for an electronic control device for the production of variable heating powers, wherein the individual cooking regions are usable together by being connected together, in particular for elongate cooking vessels.

In cooker hobs, it is usual to arrange a plurality of cooking regions which as a rule each have a heating element effective in one heating region.

For different pot sizes, cooking regions of different areas are provided. It is, however, also known to equip the cooking regions with appropriately structured heating elements for specially shaped cooking pots, for example for fish or poultry pots of elongate or oval shape, wherein an additional zone heating region is preferably switched additionally to a central heating region (DE-OS 30 04 181). It is, of course, also possible to utilize two neighbouring individual cooking regions at the same time for a cooking container covering both cooking regions, in which case the heating power regulation for both individual cooking regions takes place individually. With a mode of operation of that kind, it is disadvantageous that an unheated area is present between the individual cooking regions.It is also known to solve this problem by arranging an additional heating element between the individual cooking regions so that an elongate heated cooking region is formed by the two individual cooking regions and the additional cooking region therebetween (DE-PS 26 53 389). It has been suggested to switch in common the individual heating regions to be utilized together and to drive them with appropriate dimensioning of the heating powers.

The present invention has as a general object the provision of means for the control of the heating elements for individual cooking region use and for combined use of the cooking regions, with a low effort in terms of manufacturing technique and a course of operation and utilization secure against erroneous operations.

Such control means can be based on circuit measures with the use of electronic circuit elements, wherein the input of the heating power control criteria can take place selectably through, for example, rotary switches or touch switches such as touch-sensitive switches. An indication can be provided appropriately through, for example, the respective setting position of input switches, through mechanical indicating means or through an electronically drivable electronic display.

According to the present invention there is provided control means for heating elements in a cooker hob having at least two individual cooking regions with a respective electronic control device for the production of variable heating power, wherein the individual cooking regions are usable together by being connected together, the control means comprising switching means operable to switch the current paths for the heating elements associated with the individual cooking regions in such a manner that the heating elements of the individual cooking regions are each seiectably connected in a first switching state of the switching means to the respective heating power control device and in a second switching state of the switching means the heating elements are connected in common to one of the control devices and the or each other control device is separated from its associated heating element.

Control means embodying the present invention may offer substantial advantages for cooker hobs in terms of both manufacturing technique and operating technique. In the operating panel for the operating hob, apart from the input and indicating elements associated with the individual cooking regions, merely an additional element for switching-on and switching-off with appropriate indication need be arranged. In terms of switching technique, only change-over switch functions are required.

Further measures for the heating power regulation in combination operation of otherwise individually drivable heating surfaces are thus not required. This is also advantageous in terms of operating technique. Normally, individual cooking regions lying one behind the other are operated together for the combination operation. For the operator, it is then sensible to operate that regulating device for the individual heating current operation which is otherwise associated with the forward one, thus the individual cooking place closer to the operator. For switching-on of the combination operation, merely a single input device need be actuated at the beginning, and the fact that this combination operation is switched on is signalled either through the setting of this input device or preferably through a luminous indication or an indicating display.It is also ensured that the effect of the second heating power control device on the heating elements associated in the individual operation is reiiably interrupted.

An erroneous operation is thereby excluded.

In the case of control means for the control of the cooking regions in a cooker hob in which an additional heating region is arranged at least between two individual cooking regions, this additional heating region is additionally switched to a heating power control device through switching elements in one of their switching positions. As a result, a substantially continuous heating region is supplied with the selectably desired heating energy through the heating power control device present in any case.It is known and customary for the individual cooking regions of a hob to be of different sizes, i.e. with different diameters; it can be expedient to use generally like heating elements which are matched to the size of the smaller cooking region and for larger heating regions to associate an additional heating element, for example in annular shape, with this individual heating element. It would, however, be unfavourable to combine differently sized, individually drivable heating regions for the individual operation, since different heating powers would act in different regions on the stock to be cooked.

To eliminate this, the control means is advantageously modifiable in the sense that in the case of at least one individual cooking region with a central zone heating element and a further additional zone heating element drivable together with this from one heating power control device, the additional zone heating element is separated from the heating power supply in the switching position of the presetting switching element for the common association of both individual cooking regions with one heating power control device. Care is also taken in this connection that this additional zone heating element cannot also be driven through the heating power control device used in individual operation with the central zone heating element, while the central zone heating element is switched over for the combination heating operation.

Preferably, switching contacts, which are arranged individually in series with the heating elements and which are associated with sensors arranged in the region of the individual cooking regions for temperature limitation, are switched in series with the respectively associated heating elements on common switching of the heating elements of the heating elements of the individual cooking regions to one of the heating power control devices. No additional effort for the overheat protection results through this preferred feature; the temperature-limiting sensors and switches are used equally well unchanged in their function and in their effective range during the individual driving and mode of operation of the individual cooking regions as well as also in the combination operation.

In cooking regions with heating elements without respective temperature-limiting equipment, such equipment often being absent in the case of the intermediate heating elements, these heating elements are, on switching-on to one of the heating power control devices, switched to the switching element associated with this other heating element for the temperature limitation.

Within the scope of the use of electronic circuit measures for the driving of the heating elements in cooker hobs, the control means may comprise a power switching device connected in front of each individual heating element, a switchon/power-control input element arranged for each individual cooking region and an input element arranged for the combined driving of a plurality of heating elements, and an electronic logic interlinking circuit functionally connected between the input switching elements and the power switches in such a manner that with the input element actuated for the combined driving of the plurality of heating elements, the powerswitching devices for the heating elements to be driven together for a combined heating operation are switched through to a predetermined switchon/power-control input element, and that the further switch-on/power-input elements for the individual driving of these heating elements are put out of operation. This measure has a very positive effect in that the respective power amplifier, which controls the heating power through to the individual heating elements of the cooking regions in individual operation, is unrestrictedly used in combination operation and that a further heating power switch to switch the entire heating power is not needed. It is also not necessary to design one of the present heating power switches so that the increased power during combination heating operation would have to be switchable by it. The electronic circuit measures can be confined to simple digital change-over switchings.

It is advantageous in this connection to structure the control means so that the logical interlinking circuit is formed by a micro-processor circuit, that the switch-on input elements for the individual cooking regions are switched together, by way of a multiplex circuit switchable through by the microprocessor, and the input element for the combined driving of a plurality of heating elements is switched to inputs of the microprocessor and that the power-switching equipment is switched through switching amplifiers to a respective one of the parallel outputs of the microprocessor circuits. In a modification of this measure, mechanical switches with voltage divider circuits, which are formed by ohmic resistors and connected to the analog input of the microprocessor circuit, are arranged as the switch-on/power-control input element.Thus, rotary switches can be used, the operation of which corresponds to the operation of conventional heating input regulators.

According to another modification, a pair of touch-sensitive switching elements can be arranged as the switch-on/power-control input element of a respective heating-power control input point associated with an individual cooking place, wherein the switching elements of a switching element pair are switched on connected in parallel in like sense with the switching elements of the digital inputs, associated with functions of opposite sense, of the microprocessor circuit. This measure is particularly advantageous in the context of electronic digital circuit measures for the control of operations, since touch-sensitive switching elements for the input of control operations of that kind are less expensive and moreover require less maintenance and are more amenable to maintenance.

It is advantageous in this connection if indicating displays are connected to the parallel outputs of the microprocessor circuit and a respective storing gate circuit openable by the microprocessor circuit is arranged between the outputs of the microprocessor circuit on the one hand and the indicating displays and the switching amplifiers driving the power switching devices.

Preferably, a blinking generator is arranged for the driving of the display indicating device which is associated with the switch-on/power-control input element separated in terms of drive technique from the associated individual heating region in the combined heating operation, on actuation of the input element for the combined driving of the plurality of heating elements and on superimposed actuation of the separated switch on/power-control input element.

With a view to a functionally reliable manner of operation, it is advantageous that a blinking generator for the driving of the display indicating device, which is associated with the switchon/power-control equipment separated from the associated heating region during the combined heating operation, is switched to a storage stage which is set during the switching-on operation of the blinking generator and reset back through an appropriate switching input on or after termination of the combined heating operation at the "off" position of the switch-off/power-control device separated during the combined heating operation.

Preferably, the change-over switching elements, which are switchabie over together between the individual current supply paths of both the heating elements, are connected in series with the heating element to be separated from a respective heating power control device and switchable to the heating power control device of a further heating element.For preference, one of two heating zones of one cooking region is switched to the heating power control device of the further cooking region, so that one of the two change-over switch elements is connected in series with both the zone heating elements and the other one of the two changeover switch elements merely in series with the zone heating element to be switched on additionally and with this in parallel to the other zone heating element and that the change-over switch elements are on the switching side associated on the one hand with the current feed line pair of the individual current supply path associated with the heating element to be switched over and on the other hand with the current feed line pair of the current supply path associated with the other heating element in such a manner that at least the one current feed lines of the current feed pair with a common phase potential are switchable over selectably with the current feed lines of other phase potentials through the switch-over elements switchable together.

For reasons of switching-contact technique, it can be expedient if the change-over switch elements are formed by a combination of a switch-on element and a switch-off element.

In the case of an additional heating element arranged between the individual cooking regions, this additional heating element may be connected in parallel with a further switching element switchable in series with the switching elements of the heating element-to be connected additionally--of the second individual cooking region, with the heating element of the first individual cooking region.

An embodiment of the present invention will now be more particularly described by way of example with reference to the accompanying drawings, in which: Figs. 1 to 4 are schematic views of possible operating situations with the use of two individual cooking regions and an intermediate cooking region in a cooker hob; Fig. 5 is an overall plan of a driving device with inclusion of a microprocessor; Fig. 6 is a diagram of part of this circuit arrangement in the region of input devices; Fig. 7 is a diagram of part of the circuit arrangement according to Fig. 5 with touchsensitive input devices; Fig. 8 is a diagram of a relay arrangement through which the heating power current is fed to the individual heating elements; Fig. 9 is a diagram of a circuit arrangement with mechanical contact switches for heating energy control in the rest state;; Fig. 10 is a diagram similar to Fig. 9, showing the operational state for the first cooking region according to Fig. 2; Fig. 11 is a diagram similar to Fig. 9, showing the operational state for the second cooking region according to Fig. 3; and Fig. 12 is a diagram similar to Fig. 9, showing an operational state in which the first cooking region and the second cooking region as well as a heating region lying therebetween are usable together according to Fig. 4.

Referring now to the drawings, Figs. 1 to 4 show a first individual cooking region Ha, a second individual cooking region Hb with H'b structured to be separated in terms of heating technique into two zones, and an intermediate cooking region Hz arranged between these individual cooking regions. With the aid of control means embodying the present invention, it shall be possible to drive either one of both the heating regions Ha or Hb and H'b individually on their own or individually together. The hatched area of the heating region Ha in Fig. 2-symbolises its manner of operation, while the hatched area in Fig. 3 characterises the operation of the heating region which is formed by a circular inner heating region Hb and an outer heating region H'b arranged annularly therearound.Both heating regions are influenced by a common control member and are aiways in operation together during the individual heating operation mode.

The Fig. 4 symbolises the combination heating operation. In this case, the heating region Ha, the inner heating region Hb and the intermediate heating region Hz are in operation. The heating region H'b is switched off. An elongate, substantially homogeneous heating region is thus provided for elongate or oval cooking or roasting vessels.

Normally, four individual cooking regions are arranged in a cooker hob, of which two individual cooking regions are connectible together with an intermediate heating region for a combination operation. However, two pairs of individual cooking regions with or without intermediate cooking regions or other desired configurations can be formed in the cooker hob.

Circuit measures for the driving of four individual cooking regions and one intermediate heating region will now be described with reference to Figs. 5 to 8.

The core of this circuit arrangement is a microprocessor yP, to which the switching means of the input elements are connected at the input side and operating indicating elements and relays K1 to K8 for the switching-through of the heating currents for the individual heating regions are connected at the output side.

According to Fig. 6, four input switches, which on rotary displacement connect further switching contacts S1, S2, S3 and S4 to resistance cascades P1, P2, P3 and P4, are arranged for the four individual heating regions in the cooker hob.

These resistance cascades in conjunction with the switching element act as variable voltage dividers, to which different voltage potentials are delivered according to the setting of these switching elements. The outputs of these switching elements are conducted to a multiplex state MP. The multiplex stage MP is driven to the outputs AO, Al, A2 and A3 so that the input values of the input switches are interrogated in cyclic sequence and conducted one after the other to the analog inputs EO and El of the microprocessor. Within the microprocessor, the input values are individually translated into power control values for the individual heating regions.

In the input circuit arrangement according to Fig. 7, capacitive touch switches are illustrated as touch-sensitive input devices for the power control, of which two units KBS 1 -KBS8 lying one beside the other are each associated with a respective one of the four individual cooking regions. According to the multiplex stage of Fig. 6, the capacitive input switches are driven through the outputs AO--A3 of the microprocessor and in accordance with the touching of one of the input fields at the instant of the interrogation, a value is delivered through one of the inputs E2 or E3.

which value corresponds to an increase or a decrease of the setting value.

The outputs AO--A3, which are associated with the individual input devices of the four cooking regions on the cooker hob, are additionally also associated with the corresponding 7-segment fields of an indicating display AD. Each of these conductors drives one of these fields of the indicating display. These have 7 segments and a decimal point as numerical indicating fields. The selection of these 7 segments and of the decimal point takes place through the parallel outputs PAO--PA7.

The inputs of a latching stage are also connected to the outputs PAO--PA-/. This latching stage LS takes over the signal present at the outputs PAO--PA7 through a further output A7 of the microprocessor and makes it available at the output side for the driving of the relay stage K1--K8. Through appropriate cycling, generated by the microprocessor, of these signals, a duty ratio is generated for the corresponding relays, which corresponds to the current power to be exerted for the individual heating regions.

A relay stage of that kind is shown in Fig. 8.

This relay stage consists of eight individual relays, of which two relays K1 and K2 switch through the phase lines Ll, L2 and L3 and the neutral conductor N. The remaining relays K3-K8 are associated with the heating elements Rl-R6 arranged in the cooker hob. As has been already described, four individual cooking regions are provided in the cooker hob. Of these, two cooking regions respectively contain a heating element R1 and R2. Moreover, a heating region arrangement is provided in the cooker hob, as is evident from the Figs. 1 to 4. It is evident from this that four further individual heating elements R3-R6 must be arranged.The heating resistor R3 is associated with the heating surface Hb, the heating resistor R4 with the heating surface Ha, the heating resistor R4 with the heating surface Ha, the heating resistor R5 with the intermediate heating region Hz and the heating resistor R6 with the heating region H'b.

The microprocessor control u is selectably influenced through the input elements described with reference to the Figs. 6 and 7 in such a manner that the associated relays K3, K4, K5, K7 and K8 are acted on by control pulses in the individual cooking operation so that the desired heating power through the heating resistors R1, R2, R3 and R6 is generated in the individual cooking regions through the respectively set pulse-pause ratio. In individual cooking operation, both the relays K7 and K8 are always driven in common, since they are together associated with one cooking region.

In order to make possible the mode of operation, indicated in Fig. 4, in which the heating region Ha, the heating region Hb and the heating region Hz are used together, it is necessary to put in an appropriate input criterion. For this purpose, an input key SK is arranged on the control field according to Fig. 6 and an input field KPK is arranged according to Fig. 7. The state in which the combination heating is switched on is signalled either through the switch setting or through a special indicating element, for example an LED indication.

When the input device for the combination operation is actuated, then the input device for the individual cooking region Ha is made effective through the microprocessor control for the common driving of the relays K5, K6 and K8 so that the associated heating elements R3, R4 and R5 are acted on in common by heating current in the same pulse-pause ratio according to the value set through the input device. The relay K7 remains unaffected in this mode of operation.

Moreover, it is ensured that an actuation of the input device associated with the individual heating region Hb and H'b has no effect on the associated heating region. An actuation of that kind is, however, signalled by an indication and until the combination heating operation as well as also the actuation of this input device have been reversed. The combination heating operation is terminated when the setting of the relevant input device for the heating power control is set back.

For a repeated combination heating operation, the relevant selecting device must thus be actuated again each time.

The circuit shown in Fig. 9 includes switch-on and switch-off elements, heating power control elements, temperature-limiting elements and the heating elements R, which are associated with the heating regions H according to Fig. 1.

Elements for the first heating region are designated by the reference component a, while the reference component b designates the elements of the second individual cooking region.

Mechanical change-over switches ul to u5 are switchable only together and serve for the switching-over from individual cooking region operation to the combination operation.

The switch setting required for the operation of the individual cooking region Ha is evident from Fig. 10. For this purpose, both switch contacts al and a2 to be switched in common are closed and the energy regulator a3 is switched on. Since the switch chain u is disposed in the rest position and the switch contact ul is thereby opened, merely the heating element Ra is acted on by current for heat energy generation. In the case of overheating, a temperature sensor device Ta comes into operation and opens the associated switch contact so that the current path to the heating element Ra is interrupted on overheating.

The switch setting for the operation of the second individual cooking region is shown in Fig. 11. In this case, the switching contacts bl and b2 are closed and the energy regulator b3 is switched in.

The switching contacts u2 and u5 are closed in the rest setting of the operation selection changeover switch so that the heating element Rb as well as the heating element R'b are acted on by regulated heating current. To prevent overheating, there is provided a temperature-sensing device Tb, through which the associated switching contact is opened when a predetermined highest temperature value is exceeded, so that the supply current for the heating elements Rb and R'b is interrupted.

If an elongate heating region is to be made available, as illustrated in Fig. 4, then the changeover contact combination u is actuated so that the switching contacts u 1, u3 and u4 are closed and the switching contacts u2 and u5 opened. The heating elements Rb and Rz are now connected in parallel with the heating element Ra and can be acted on with this regulated heating current through the switching contacts al and a2 and the energy regulator a3.

Since the switching contacts u2 and u5 are opened in the change-over switch setting of the switching contact combination u and in consequence of the illustrated line conduction, the heating element R'b is not drivable. The current path to the respective energy regulator device is entirely interrupted through the switching contact u2 and, due to the opened switch contact u5 and the appropriate line conduction, a current flow through the heating element R'b cannot take place either by way of the closed switching contact a2 or by way of the closed switching contact b2. Through such a circuit arrangement, the same phase potential is present at the heating element R'b in this case with simultaneously closed switching contacts a2 and b2.

Claims

1. Control means for heating elements in a cooker hob having at least two individual cooking regions with a respective electronic control device for the production of variable heating power, wherein the individual cooking regions are usable together by being connected together, the control means comprising switching means operable to switch the current paths for the heating elements associated with the individual cooking regions in such a manner that the heating elements of the individual cooking regions are each selectably connected in a first switching state of the switching means to the respective heating power control device and in a second switching state of the switching means the heating elements are connected in common to one of the control devices and the or each other control device is separated from its associated heating element.

2. Control means as claimed in claim 1, wherein an additional heating region is arranged between the individual cooking regions, the switching means being operable to connect the additional heating region to said one heating power control device in the switching state of the switching means in which both the individual cooking regions are connected together.

3. Control means as claimed in either claim 1 or claim 2, wherein at least one of the individual cooking regions is associated with a central zone heating element and with an edge zone heating element both controllable by one heating power control device, and wherein the switching means is operable to separate the edge zone heating element from the heating power feed in the switching state of the switching means for the common association of both individual cooking regions with one of the heating power control devices.

4. Control means as claimed in any one of the preceding claims, comprising switching contacts, which are arranged individually in series with the heating elements and which are switchabie for temperature limitation through sensors arranged in the region of each of the individual cooking regions, the switching contacts being connected in series with the associated heating elements also on connection in common of the heating elements of the individual cooking regions to said one heating power control device.

5. Control means as claimed in any one of the preceding claims, wherein heating elements without respective temperature-limiting means, on being connected to said one heating power control device, are connected for temperature limitation to a switching element associated with the other heating elements connected in common.

6. Control means as claimed in any one of the preceding claims, comprising a power-switching device connected in front of each individual heating element, a switch-on/power-control input element provided for each individual cooking region, an input element arranged for selecting the combined operation of a plurality of heating elements, and an electronic logic interlinking circuit functionally connected between the input switching elements and the power switches in such a manner that, with the input element actuated for the combined operation of the plurality of heating elements, the powerswitching devices for the heating elements to be operated together for a combined heating operation are connected to a predetermined one of the switch-on/power-control input elements and that the other switch-on/power-control input elements for the individual operation of these heating elements are taken out of operation.

7. Control means as claimed in claim 6, wherein the logic interlinking circuit comprises a microprocessor circuit, the switch-on/powercontrol input elements for the individual cooking regions are connected in common by way of a multiplex circuit to inputs of the microprocessor, the multiplex circuit is arranged to be conductive under the control of the microprocessor, the input element for selecting the combined operation of a plurality of heating elements is connected to a further input of the microprocessor, and the power-switching devices are connected through switching amplifiers to respective ones of the parallel outputs of the microprocessor circuits.

8. Control means as claimed in either claim 6 or claim 7, wherein the switch-on/power-control elements comprise mechanical switches with voltage divider circuits comprising resistors and being connected to the analog input of the microprocessor circuit.

9. Control means as claimed in either claim 6 or claim 7, wherein the switch-on/power-control input elements of a respective heating-power control input point associated with an individual cooking region comprises a pair of touch-sensitive switching elements, the switching elements of a switching element pair being switched on connected in parallel in like sense with the switching elements of the digital inputs, associated with functions of opposite sense, of the microprocessor circuit.

10. Control means as claimed in any one of claims 6 to 9, comprising indicating display means arranged at the parallel outputs of the microprocessor circuit, and a respective storing gate circuit openable by the microprocessor circuit and arranged at the switching amplifiers driving the power-switching devices.

11. Control means as claimed in any one of claims 6 to 10, comprising a blinking generator for driving display indicating element associated with the switch-on/power-control device separated from the associated heating region during the combined heating operation, the generator being connected to a storage stage which is set during the switching-on operation of the generator and reset back through a switching input on or after termination of the combined heating operation at an "off" position of the switch-off/power-control device separated during the combined heating operation.

12. Control means as claimed in any one of claims 3 to 5, comprising change-over switching elements, which are switchable together and switchable over between the individual current supply paths of both the heating elements and which are connected in series at both sides with the heating element which is to be separated from a respective heating power control device and to be switchable to the heating power control device of a further heating element.

1 3. Control means as claimed in claim 12, wherein one of two heating zones of a cooking region is connectible to the heating power control device of a further cooking zone, one of the two change-over switch elements is connected in series with both the zone heating elements and the other one of the two change-over switch elements is connected in series merely with the zone heating element to be switched in additionally and together with this in parallel with the other zone heating element, and the changeover switches are at the switch side associated on the one hand and with the current feed line pair of the individual current supply path associated with the heating element to be switched over and on the other hand with the current feed line pair of the individual current supply path associated with the other heating element in such a manner that at least the current feed lines of the current feed pairs with a common phase potential are switchable over selectably with the current feed lines of other phase potentials through the change-over switch elements switchable in common.

14. Control means as claimed in either claim 12 or claim 13, wherein the change-over switch elements are each provided by a combination of a respective switch-on element and a respective switch-off element.

1 5. Control means according to either claim 13 or claim 14, wherein the additional heating element arranged between the individual cooking regions is connected in parallel with a further switching element switch able in series with the switching elements of the heating element, to be switched in additionally, of the second individual cooking region, with the heating element of the first individual cooking region.

1 6. Control means substantially as hereinbefore described with reference to the accompanying drawings.