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

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.