GB1456788A - Induction heating appliance - Google Patents

Abstract

1456788 Induction cooking appliance MATSUSHITA ELECTRIC INDUSTRIAL CO Ltd 4 Feb 1975 [5 Feb 1974] 4700/75 Heading H2H An induction cooking appliance comprises induction heating means 28, Fig. 6, for generating an alternating magnetic field, an inverter 14-26 coupled to the heating means 28, an A.C. power source 2, a rectifier 8 disposed between the power source and the interior, and an insulating top plate 30 over the heating means 28 for depositing at least one cooking vessel 32 thereon, and further comprises means for detecting a crack in the hot-plate 30 to deenergize the apparatus, and further means for preventing leakage current owing to electrostatic coupling between the cooking vessel and the induction heating means. The means for detecting a crack of hot-plate 30 comprises a loop of conductive film 46, Fig. 6, deposited on the underside of the hot-plate and connected across the secondary 3b of relay transformer 3 via terminals 48, 50. A break in this film will cause the relay to deenergize and open supply terminals 3c, 3d. In a modification, Fig. 7 (not shown), a first relay is deenergized to open a contact to deenergize a second relay to deenergize the circuit. For preventing electrostatic coupling between the utensil 32 and coil 28, a second conductive film 42, Fig. 4, is applied to the underside of plate 30. This is formed so that any conducting loops are not present to prevent looped inductive heating currents from occurring therein, and is coupled via capacitor 43 to the return line 12 of the inverter. A water repellent film 52 may be placed around each of the conductive films to prevent shorting therebetween owing to moisture condensation on the hot-plate 30.