Thorn Emi Plc

Thorn Emi Domestic Appliances Limited

John A Letchford

Alex L Halberstadt

Kenneth S Frost

A tungsten halogen lamp producing infra red radiation, for example for cooking or heating, has an envelope of high silica content material sealed at each end by a pinch seal. A gas fill is at a room temperature pressure of 250-750 mm Hg. A portion of the envelope at each end is clear and the rest contains an opacifier which reduces transmission of visible light. A suitable opacifier is red, being produced by the reduction of copper oxide dispersed in the high silica content material. The envelope is produced by butt joining clear end sections and a tube of material containing opacifier.

Tungsten halogen lamp

Filter holder

An infra-red lamp consists of a quartz tubular envelope sealed at each end with a respective pinch seal. A tungsten filament supported within the envelope is electrically connected, via a molybdenum foil strip and lead wires within the pinch seal to a connector for connection to a power supply. Each pinch seal is substantially wholly enclosed within a ceramic housing, which is preferably provided with a locating flange, to protect the pinch seal in part from heat emitted by the filament and to assist in location of the lamp in an operating environment.

Quartz infra-red lamps

Heating apparatus includes a tray having a layer of insulative material disposed therewithin, above which a number of infra-red lamps are supported. The ends of each lamp are provided with a pinch seal having an amp tag connector, which is connected to the respective end of a filament within the lamp, sealed therein. Each pinch seal is enclosed within a ceramic housing and the heating apparatus is mounted beneath a layer of glass ceramic. A heat-conductive stud is intimately disposed between the layer and the pinch seal, via an aperture in the housing, so as to provide a good heat-conductive path from the pinch seal to the relatively cool glass ceramic.

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Enfield, United Kingdom

John A Letchford