Electric heating – Heating devices – With power supply and voltage or current regulation or...
Patent
1992-02-28
1994-06-28
Paschall, Mark H.
Electric heating
Heating devices
With power supply and voltage or current regulation or...
219492, 219518, 340589, 99327, 99332, H05B 102
Patent
active
053249178
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates principally to a device and to a method for regulation especially of the temperature and/or of the power of a cooking apparatus.
2. Discussion of the Background
It is known for electrical cooking apparatuses to associate a device for measurement of temperature with a device for regulation.
These apparatuses have the aim, after an initial period of pre-heating, of maintaining substantially constant the temperature of a heating receptacle. However, the temperature of the sensor or, preferably, of the recipient is regulated, and not its contents. In fact, in order to deduce the temperature of the contents from the temperature of the sensor, it would be necessary to know the development of the temperature. Now, the correlations between temperature of the sensor and that of the contents of the cooking receptacle vary (sic) from one cooking operation to the next and sometimes even in the course of a single cooking operation. This relation varies, for example, between a frying pan with one liter of oil and a shallow cast-iron saucepan with 3 liter of oil or a cast-iron grill pan. The addition, of, for example, 800 grams of chips in the course of cooking completely modifies the temperature of the contents of the receptacle and influence only after a certain delay and in a damped fashion the variation of the temperature of the sensor.
SUMMARY OF THE INVENTION
The device according to the present invention has the aim of limiting the temperature of the receptacle in order:
Moreover, the invention also has the aim of bringing the contents of a receptacle as quickly as possible to a desired temperature, for example 180.degree. C. in the case of oil, without ever exceeding a maximum temperature of for example 400.degree. C. in the case of a film of oil.
In the device according to the present invention, servocontrol is performed by derivation of a servocontrol curve in the plane (temperature, variation of the temperature with time). The servocontrol curve shears the plane into two distinct surfaces. As long as the curve is not reached, heating is performed at full power. As soon as the curve is crossed the heating power is reduced or stopped. When the temperature sensor has detected in the phase diagram the passing from the other side of the servocontrol curve, heating is again performed at full power or the power is increased.
The subject of the invention is mainly a monitor apparatus, a heating element and a temperature sensor characterized by the fact that the monitor device incorporates means of evaluating the variation in time t of the temperature .theta..
The subject of the invention is also a heating apparatus incorporating a monitor device, a heating element and a temperature sensor, characterized by the fact that the monitor device incorporates means of calculating the derivative of the temperature .theta. with respect to time t.
The subject of the invention is also an apparatus characterized by the fact that the monitor device provides a servocontrol curverbose points have as the abscissa the temperature .theta. and as the ordinate the derivative with respect to time of the temperature d.theta./dt and that it incorporates means which make it possible to stop or to reduce the electrical supply to the heating element every time the value of d.theta./dt exceeds the value of the ordinate of the curve for an abscissa corresponding to the temperature reached.
The subject of the invention is also an apparatus characterized by the fact that the monitor device provides a curve whose points have as the abscissa the temperature .theta. and as the ordinate the derivative d.theta./dt with respect to time t of the temperature .theta., the crossing of which indicates that an empty cooking receptacle is present or that no cooking receptacle is present on the heating element and the means for cutting off the electrical supply to the heating element if the curve is crossed.
The subject of the invention is also an apparatus characterized by the fact t
REFERENCES:
patent: 4587406 (1986-05-01), Andre
Boyer Serge
Gouardo Didier
Pitot Pierre
Compagnie Europeenne pour l'Equipement Menager-Cepem
Paschall Mark H.
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