Foods and beverages: apparatus – Cooking – Automatic control
Reexamination Certificate
2000-12-11
2001-07-24
Simone, Timothy F. (Department: 1761)
Foods and beverages: apparatus
Cooking
Automatic control
C099S337000, C099S403000, C219S449100, C219S481000, C219S494000
Reexamination Certificate
active
06263782
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a device for sensing the presence of at least one at least partly metal cooking utensil (pan, pot, casserole etc.) positioned on a preferably electrical heat source of a cooking appliance (hot-plate, cooking hob, cooker etc.) in accordance with the introduction to the accompanying claim
1
.
2. Description of the Related Art
EP-A1-0553425 describes a method and device for sensing the presence of a cooking utensil positioned on a glass ceramic cooking hob above a usual heat source, for example electrical. Between this source and the glass ceramic surface there is positioned a wire resistor of open ring configuration.
After positioning the cooking utensil a variation occurs in the characteristics of the wire resistor of open ring configuration and hence of the electrical signal flowing through the resistor.
The known device has not proved sufficiently reliable in the sense that under certain operating conditions spurious signals occur which give a false indication of the presence and/or absence of the cooking utensil.
SUMMARY OF THE INVENTION
The main object of this invention is to provide a device for sensing the presence of cooking utensils which is based on different concepts and which besides being reliable is also more advantageous cost-wise.
According to the present invention, the foregoing and other objects are attained by a device for sensing the presence of cooking utensils on a cooking hob comprising at least one heat source. The device includes an electrically conductive coil turn fed by the signal generated by an oscillator. The oscillator is preferably a voltage-controlled oscillator generating square wave signals. The coil turn operates, when utensil sensing occurs, to modify the cut-off frequency of a low pass filter (L/R) fed by said oscillator (VCO).
This and further objects which will be more apparent from the detailed description given hereinafter are attained by a sensing device in accordance with the teachings of the accompanying claims.
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patent: 4671250 (1987-06-01), Hurley et al.
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patent: 4913038 (1990-04-01), Burkett et al.
patent: 5310110 (1994-05-01), Akamatsu et al.
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patent: 5856654 (1999-01-01), Frasnetti et al.
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patent: 19700753 A (1998-07-01), None
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European Search Report EP 00 12 2404 Dated Jan. 30, 2001.
Brindani Franco
Frasnetti Luca
Rice Robert O.
Roth Thomas J.
Simone Timothy F.
Van Winkle Joel M.
Whirlpool Corporation
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