Abstract: A heating assembly is disclosed in which infra-red energy generated by one or more tungsten halogen lamps is transmitted through a glass ceramic layer covering the lamp or lamps. The operating temperature of the glass ceramic layer is monitored by a thermal limiter in the form of a rod of thermally expansive material which, upon expansion by a predetermined amount, actuates a cut-out switch which de-energizes the lamp or lamps. The rod is shielded from incident energy from the lamp or lamps to render it primarily responsive to the operating temperature of the glass ceramic layer.

Abstract: A heating assembly including at least one infra-red emissive tungsten halogen lamp supported beneath a glass ceramic cooktop which allows useful quantities of the infra-red radiation, as emitted by the lamp (or lamps) and directly incident on the undersurface of the cooktop, to emerge from the assembly and above non-metallic, thermally insulating material contained as a layer in the base of a shallow tray. The layer contains, or supports at its surface, material which efficiently reflects the infra-red radiation emitted from the lamp (or lamps) substantially unchanged in spectral content so that useful quantities of the radiation so reflected and then incident on the undersurface of the cooktop emerge from the assembly to supplement the directly incident radiation.

Abstract: A heating unit includes two tubular tungsten-halogen lamps, each having a tungsten filament. The lamps are supported within a ring of ceramic fibre material and the unit is preferably mounted beneath an infra-red-transmissive cooktop to define a hotplate area of a cooking hob. A control circuit provides a range of discrete power outputs of the lamps, each power output corresponding to a power control setting set by a user of the cooking hob. The circuit includes a phase control circuit for switching power to the lamps at a predetermined phase angle to achieve one or more of the lower power outputs.

Abstract: Heating apparatus consists of a shallow circular tray having a layer of thermally insulative material disposed therewithin and supporting four infra-red-emitting, tunsten-halogen lamps on flanges. A moulding of ceramic fibre material is press-fitted around the ends of the lamps and a thermal limiter is provided to limit the operating temperature of the apparatus. Each lamp is provided with a reflective coating along the lower part thereof, so as to reflect upwardly infra-red radiation emitted in a downward direction. A number, preferably four, of the heating apparatuses are disposed beneath a layer of glass ceramic to provide a cooking hob.

Abstract: A thermal limiting device for controlling one or more sources of infra-red radiation, preferably tungsten-halogen lamps, mounted in heating apparatus, consists of a metallic wire arranged to de-energize the sources when it is subjected to a predetermined temperature. The wire is accommodated within a quartz tube, which selectively transmits and absorbs infra-red radiation of different wavelengths. An infra-red reflective coating is applied either to the wire or to the inner surface of the quartz tube to prevent infra-red radiation transmitted through the quartz tube from reaching the wire, while infra-red radiation of a particular wavelength, which is absorbed by the quartz tube, heats the wire by thermal conduction and convection, so that the limiter is primarily responsive to radiation only of that particular wavelength.