GB2114828A

GB2114828A - Control means for the heating means of a baking oven

Info

Publication number: GB2114828A
Application number: GB08300830A
Authority: GB
Inventors: Julius Husslein; Helmut Waigand
Original assignee: Individual
Current assignee: Individual
Priority date: 1982-02-10
Filing date: 1983-01-13
Publication date: 1983-08-24
Also published as: IT8319465A1; GB2114828B; IT8319465A0; GB8300830D0; DE3204518C2; DE3204518A1; BE895870A; NL8300200A; FR2521383A1; IT1193666B; FR2521383B1

Abstract

Control means in a baking oven for controlling the heating energy required for the cooking process comprises an input element (ST) for presetting the value of such energy. In particular, an indication of the heating energy to be supplied continuously is delivered to a microprocessor (???P) in correspondence with an input value preset by the input element (ST), and a timer is set in dependence on the setting value of the input element at the beginning of a cooking process. The full heating power current is fed to the heating elements for an initial time interval set by the timer and thus dependent on the setting of the input element (ST). The setting of the input element is displayed by a display unit (SSA) and the initial heating interval is indicated by D. <IMAGE>

Description

SPECIFICATION Control means for heating means of a baking oven The present invention relates to control means for heating means of a baking oven, and has particular reference to control means for setting ready the heat energy which is required for the cooking process and the value of which is presettable.

It is known for the generation of the heat t in electrical baking ovens to set temperature regulators through setting devices to a desired value, whereafter, through this temperature regulator, the supply of heating current to the heating elements takes place while the tempeature is below the set value and is interrupted when this value is exceeded. It is advantageous in this mode of operation that the full heating power is available and is utilized immediately at the beginning of the cooking process. When the set temperature value is reached, then this entire heating power is switched off until the temperature falls to a lower value at which the full heating power is again switched on. This operation repeats during the entire cooking process.For the performance of these switching operations, thermostats are used, which have a certain hysteresis in their switching behaviour. This hysteresis acts in such a manner that extended phases of different temperature fluctuations occur in the baking oven. These phases are relatively long for the reason that the baking oven is as well insulated as possible outwardly. For a continuous cooking process, however, it would be desirable to provide as constant as possible a temperature behaviour in the oven.

There is accordingly a need for control means through which it is possible to peform an as optimum as possible cooking process within the baking oven, especially with the use of advantageous circuit measures, for example digital switching means or microprocessor means.

According to the present invention there is provided control means for heating means of a baking oven, comprising selecting means for selecting a value representing a desired level of heat to be continuously supplied by the heating means, means for determining a value of operating energy for the heating means in dependence on the selected value, timing means settable to operate for a period dependent on the selected value, and means for supplying a maximum value of operating energy to the heating means for an initial operating period thereof dependent on the set operating period of the timing means.

In a preferred embodiment, a criterion of the heating power to be supplied continuously is delivered in correspondence with an input value preset through an input device, a timing member is set in dependence on the setting value of the setting device at the beginning of the cooking process, and, in dependence on the run-down of this timing member, the full heating power current is fed to the heating means of elements for a time interval preset in dependence on the further heat energy.

The heating power control is, for example, varied in that a pulse-pause ratio is produced control-technically, in which the heating current is fed through power amplifiers, for example relays, to the respective heating elements. Through variation of this pulse-pause ratio, almost as many power stages as desired can be provided.

Corresponding measures are known for the operation of heating plates in cooking hobs. The conditions for heating plates in cooking hobs are different from the manner of operation of a baking oven insofar as the foodstuffs to be warmed or heated on cooking plates is hardly insulated from the environment. due to this, the conditions change very little during the entire cooking process. A relatively large amount of energy must be supplied to the foodstuff to be treated. Baking ovens by contrast are relatively well thermally insulated from the environment. This means that actually relatively little energy need be supplied during the cooking process. When such a low energy supply is fixedly set from the start, then a relatively long heating-up time interval results.

Through the use, however, of a heating-up phase with fully energy supply before the actual, heat energy-controlled further heating phase, a short heating-up time is attained and the reduced, predetermined heating power is supplied to the cooking stock following this heating-up time.

Preferably, the time run-down is additionally presettable in respect of the time interval effective for the heating-up phase through the setting, corresponding to the respective further cooking power, of the heating power input element. The consequence of this measure is that the automatic heating-up system is switched on automatically on the attainment of the highest heating power stage setting through the input element. The timing stage for determination of the heating-up phase is preselected through resetting of the input element back to the setting value corresponding to the heat energy finally to be provided.

For preference, a respective electronic comparison value, which is made available through the switch settings associated with the individual further heating power stages, for the heating-up phase to be performed is logically interlinked with the output value of the time rundown control equipment, and a switching criterion for the termination of the heating-up phase is delivered to the heating power control circuit when the output value of the time run-down control is attained or exceeded by the comparison value. As a result, it is achieved that a correction in the dimensioning of the final further heating power is also drawn upon during the heating-up phase for the correction of the effective time interval thereof.This measure can however, also be realised through other kinds of electronic circuit measures, for example through the use of storage elements and addition or comparison stages.

Expediently, the time run-down control circuit is connected to a signal transmitter and in parallel with the heating power control circuit. By this means it can be signalled that, and for how long the heating-up operation is switched on and effective. In this connection, a blinker unit is advantageously associated with the run-down control circuit. Such a blinker unit can, for example, deliver a pulse to a light-emitting diode lamp or, in the case of numerical representation of the set further heating value, be associated by way of a seven-segment indicator with the entire indicator field or merely with the decimal point of this indicator field.

It is also possible for the time run-down control to be integrated into a microprocessor control circuit of the heating power control circuit. As a result, a low cost for the circuitry may be achieved.

An embodiment of the present invention will now be more particularly described by way of example with reference to the accompanying drawings, in which: Fig. 1 is a circuit diagram of control means embodying the invention, the control means incorporating a microprocessor module; and Fig. 2 is a time-power diagram for the control provided by the control means.

Referring now to the drawings, the circuit shown in Fig. 1 comprises an input element, which is symbolized by a voltage divider ST and by which an input signal corresponding to a selected further heating energy value is provided. In a microprocessor module ,uP, the value of this input signal present at an analog input is converted into values for the power control of baking oven heating elements. In the illustrated embodiment, this takes place through delivery of pulses and pulse pauses at the output of the microprocessor module, wherein the pulse-pause ratio represents the control value for the heating power. The pulsepause signal is drawn upon through power amplifiers RV for the control of the current supply for the heating elements of the baking oven. A seven-segment indicator display unit SSA indicates the set value.

When the setting stage for the maximum input value is assumed'at the input element ST at the start of the setting operation, the microprocessor module available evaluates this value as a criterion for the performance of a heating-up phase. During the resetting of the input element ST back to the value for the final further heat energy dimensioning, a criterion for the duration of the initial cooking phase is also derived from this final setting value by the microprocessor module.

During this initial cooking phase, in place of the pulse-pause ratio for the control of the respective power amplifier RV, a continuous pulse arises, which thus drives this amplifier continuously. As a result, the maximum usable operating current is supplied to the corresponding heating element during the initial cooking phase. The initial cooking phase is signalled by a blinking of the decimal point D in the seven-segment indicator display SSA. This indication extinguishes when the initial heating phase is terminated. If the setting value for the further heating power at the input element ST is varied after the start of the initial heating phase, then this value is also processed in the microprocessor module for variation of the heating up interval.The initial heating phase can also be terminated prematurely through resetting of the input element, whereafter the value for the further heating power can be reset by the input element.

The relationship of the time for the initial heating phase to be set heating power for the further cooking phase is represented in Fig. 2. The input element can provide switch settings 0 to 9.

The heating powers which are attainable lie on a continuous curve P, the maximum heating power being delivered at the setting 9. The time values for the initial heating phase associated with the individual setting positions 1 to 9 lie on the curve T represented in dashed lines. It is evident from this diagram that the time values for the initial heating phase rise up to the setting value 6, whilst lower time values are chosen for the setting values 7 and 8. The maximum heating value is generated in any case in the setting 9, so there is no distinction between an initial heating phase and a further heating phase.

Claims

1. Control means for heating means of a baking oven, comprising selecting means for selecting a value representing a desired level of heat to be continuously supplied by the heating means, means for determining a value of operating energy for the heating means in dependence on the selected value, timing means settable to operate for a period dependent on the selected value, and means for supplying a maximum value of operating energy to the heating means for an initial operating period thereof dependent on the set operating period of the timing means.

2. Control means as claimed in claim 1, the selecting means being operable to additionally preset the timing means with respect to said initial operating period of the heating means.

3. Control means as claimed in either claim 1 or claim 2, the selecting means comprising a switch having a plurality of settings each associated with a respective one of a pluraiity of different values representing respectively different levels of heat, and the timing means having a setting input operatively associated with the switch setting for the value indicative of the highest one of the heat levels.

4. Control means as claimed in claim 3, comprising means for providing a first comparison signal having a magnitude respective to the selected switch setting and indicative of a parameter of said initial operating period of the heating means, means for providing a second comparison signal having a magnitude indicative of a parameter of the set operating period of the timing means, means for logically interlinking the comparison signals, and means operable to provide, when the magnitude of the first comparison signal reaches or exceeds that of the second comparison signal, a signal having a magnitude indicative of a switching criterion for termination of said initial operating period by a control circuit controlling the heating means.

5. Control means as claimed in claim 4, the timing means being connected to indicating means and in parallel with the control circuit.

6. Control means as claimed in either claim 4 or claim 5, the timing means being connected to a blinker to indicate said initial operating period.

7. Control means as claimed in any one of the preceding claims, the timing means being integrated in microprocessor circuit means of a control circuit controlling the heating means.

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