GB746911A - Improvements in or relating to electric surface-heating units adapted to support cooking vessels or the like - Google Patents

Abstract

746,911. Electric hot plates. WESTING- HOUSE ELECTRIC INTERNATIONAL CO. Feb. 1, 1954 [Feb. 4, 1953], No. 2892/54. Class 39(3). An electric heater for cooking vessels comprises a tubular sheathed element 14 supported on a spider and wound in a spiral having at its centre a metal disc member 44. A thermistor 42 is mounted beneath and in good thermal relation with the disc 44, and, with control means (not shown), serves to regulate heating of the element 14. A cup shaped member 38, which may be of copper, aluminium or one of their alloys, forms a heat shield between the element 14 and the thermistor. With no vessel on the heater, the disc member 44 and the cup heat shield are urged upwardly above the upper surface of the element 14 by springs 57, 59. Placing a vessel on the heater causes the disc 44, the flange 41 of the heat shield and the upper surface of the element 14 to make good thermal contact with the bottom of the vessel, slight fitting of the disc and shield being possible to allow for any unevenness of the bottom of the vessel. Stray heat from the element 14 in the direction of the thermistor is absorbed through the outer edge of the flange 41 and the surface of the tubular wall 40 of the shield and is conducted to the vessel through the top surface of the flange. A drip sleeve 66 and an annular membrane 61 of heat insulating material, e.g. polymerized silicone rubber, protect the thermistor from spillage. A reflector is provided, Fig. 2 (not shown). In a modification, Fig. 6 (not shown), the annular membrane is dispensed with, the metal disc member sliding in a vertical bore of an insulating annular member with a minimum of side play. Specification 746,796, [Group XXXV], is referred to.