Control device for heating sources of cooking appratus

Claim 1

Control device for heating sources of cooking apparatus having a cooking surface, comprising a continuous smooth sheet of vitroceramic glass of generally uniform thickness and having upper and lower major plane surfaces, a set of neighbouring radiant heating sources mounted next to said lower surface of said glass, a plurality of sensitive keys disposed adjacent to the lower surface of the glass being actuated by an approach of a user's finger into contact or into immediate proximity with the upper surface of the sheet opposite each key, each of the plurality of the keys being connectively associated with a specific one of the set of sources and said each of the plurality of keys consisting of a first and a second of two metal armatures being disposed substantially in the same plane, the two metal armatures generally comprising a single capacitor carried by and formed as part of a printed circuit board attached to the lower surface of the sheet, the capacitor having the first of the two armatures connected to a pulse generator and the second of the two armatures connected to a differential comparator having an output, and the first of the two armatures having profile means which encompasses and surrounds the second of the two armatures in a manner such that the approach of the finger directly over the capacitor but on another side of the sheet, towards or against its upper surface, modifies a value of the capacitance and causes a change of state at the output of the differential comparator to effect varying of electrical power supplied to one of the set of sources, and said printed circuit board carrying the capacitor, the pulse generator and the differential comparator is embedded in a layer providing insulation and protection against moisture, and is adjacent the lower sheet of vitroceramic glass and in close contact therewith.