GB1349024A - Surface heating units - Google Patents

Abstract

1349024 Electric heating GENERAL ELECTRIC CO 20 July 1971 [24 July 1970] 33915/71 Heading H5H [Also in Divisions F3-F4] A solid plate surface heating unit mounted in an apertured recess on a cooker top 34 comprises a plate 10 of glass-ceramic material which is supported on top of a heat spreader plate 14 of composite metal material, a metal sheathed electrical heating coil 20 brazed to the underside of the composite plate, a reinforcing member in the form of radial struts 28 which are fastened along one edge to the underside of the plate 14, a reflector pan 30 which supports the whole assembly, and a temperature limiting means comprising a high temperature responsive bulb 62 in thermal contact with the heat spreader plate and connected by a capillary tube 66 to a temperature responder 64 attached to the reflector pan which breaks the heating circuit of the coil 20 when the plate temperature reaches a certain limit, e.g. 1200‹ C. The plate 10 may be of such materials as quartz, high silica glass, high temperature glasses as well as glass-ceramic materials which all have electrically-insulating and thermally-transmissive properties and are all resistant to wear, thermal shock and spillage. The composite plate 14 comprises a thin central core of such high thermal conductivity metals as copper, aluminium and silver sandwiched between skins of oxidation and corrosion resistant metals such as stainless steel, nickel and chromium, furthermore the plate 14 may have a ceramic coating, e.g. of porcelain enamel or silica which also gives increased thermal radiation from the plate. The heating unit is mounted on a downwardly recessed ledge 36 of the cooker top by means of a trim ring 38, circumferentially spaced clips 46 which engage through slots 40 in the ring to releasably hold down the latter and an asbestos gasket 51 to seal the unit from spillage. The temperature sensor has the form of a bulb 62 filled with a fluid such as sodium potassium. In an alternative arrangement the glass-ceramic plate 10 has a central hole through which a spring loaded sensor is put in direct contact with a cooking utensil. A manual selector switch 72 is connected across the power leads L 1 and L 2 to the heating coil. An earthing circuit 73 is provided for the composite plate. Instead of the electrical heating element shown, a gas burner may be used (see Divisions F3-F4).