Device for detecting the presence of a food container, such as a saucepan, dish or the like, on a glass ceramic cooking hob

• US 5,491,423 A
• Filed: 03/11/1994
• Issued: 02/13/1996
• Est. Priority Date: 03/15/1993
• Status: Expired due to Fees

• Current Assignee: Whirlpool Europe BV (Whirlpool Corporation)
• Original Assignee: Whirlpool Europe BV (Whirlpool Corporation)
• Inventors: Turetta, Daniele
• Primary Examiner(s): Wieder, Kenneth A.
• Assistant Examiner(s): BROWN, GLENN WARNER
• Application Number:
  US08/212,525
• Time in Patent Office: 704 Days
• Field of Search: 324/658, 324/663, 324/671, 324/686, 324/687, 324/688, 324/690, 340/825.06, 219/448, 219/451, 219/452, 99/331, 99/326, 126/39 BA
• US Class Current: 324/663
• CPC Class Codes: G01V 3/088 operating with electric fields G01V3/082 takes precedence
• CPC Class Codes: H05B 2213/05 Heating plates with pan detection means
• CPC Class Codes: H05B 2213/07 Heating plates with temperature control means
• CPC Class Codes: H05B 3/746 Protection, e.g. overheat cutoff, hot plate indicator

Abstract

A device for detecting the presence of a food container such as a saucepan dish or the like, placed on a heating element of a glass ceramic cooking hob comprising electrical conductor rings fed with signals which are identical but of opposite phase, between the conductor rings there being interposed a detector ring traversed by electrical signals, the conductor and detector rings being positioned in correspondence with that cooking region of the glass ceramic hob where the heating element is positioned, the signals from the detector ring varying on the basis of the presence or absence of the food container on the hob, a control being provided to measure the variation in the electrical signals and to intervene in the operation of the heating element.

Claims

1. A device for detecting the presence of a food container, placed on a cooking region of a hob of glass ceramic, below which there is positioned in correspondence with this region at least one heating element, said device comprising detection means positioned in correspondence with said cooking region below the glass ceramic hob and interposed between conductor means through which first electrical signals flow, said detection means generating second electrical signals at least one characteristic of which varies on the basis of the presence or absence of the container on said region, said second electrical signals being fed to heating element control means which, on the basis of the variation in the aforesaid characteristic, at least partly modify the state of activation of said heating element;

the detection means and conductors are elements arranged side by side on a support member positioned below the cooking region;

the elements on the support member are concentric annular elements, the most outer and most inner element being fed electrically by feed means, the detection means including an intermediate ring acting as a sensor member, said outer and inner annular elements defining a flat capacitor; and

the feed means are an oscillating voltage generator member, which is connected to a transformer member having two secondary windings connected at a common end to earth and at each other end to electrical means of high output impedance, said electrical means being connected to the outer annular element and to the inner annular element respectively, said outer and inner annular elements being fed with electrical signals which are identical except for one characteristic.

2. A device as claimed in claim 1, wherein the signals fed to the outer and inner annular elements are of different amplitude.

3. A device as claimed in claim 1, wherein the detection means are connected to electrical means having high input impedance, said electrical means being connected to rectifier means for generating a continuous signal transmitted to the control means.

4. A device as claimed in claim 3, wherein the rectifier means are an alternating current rectifier.

5. A device for detecting the presence of a food container, placed on a cooking region of a hob of glass ceramic, below which there is positioned in correspondence with this region at least one heating element, said device comprising detection means positioned in correspondence with said cooking region below the glass ceramic hob and interposed between conductor means through which first electrical signals flow, said detection means generating second electrical signals at least one characteristic of which varies on the basis of the presence or absence of the container on said region, said second electrical signals being fed to heating element control means which, on the basis of the variation in the aforesaid characteristic, at least partly modify the state of activation of said heating element;

a second conductor means arranged to provide reference signals for comparison with the second electrical signals originating from the detection means;

the second conductor means is an annular element interposed between the detection means and the most outer element of the first conductor means;

the second conductor means for generating reference signals are connected to a feedback branch provided in an electrical means having high input impedance to which the detection means are connected.