Incandescent lamps
AssigneeThorn EMI plc
InventorsAlex L. Halberstadt, Roger A. Hume
Life of this patent
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Abstract
An incandescent lamp, which emits infra-red radiation, comprises a tubular quartz envelope, within which a tungsten filament is supported. To reflect radiation, which is emitted in a downward direction from the filament, back in an upward direction to an item to be heated, a substantially pure aluminum oxide coating is bonded in a substantially permanent manner to the surface of the envelope. The coating extends subtantially along the length of the lamp and around approximately half of the cross-sectional circumference thereof. The coating is applied to the envelope by a spray gun technique, wherein finely divided aluminum powder is blown through an oxygenated flame, which is directed towards an area of the envelope to be coated.
Claims6
An incandescent lamp comprising:
- an envelope having an exterior surface and being formed from a material having a substantially high silica content;
- a filament enclosed within said envelope;
- and
- a coating reflective of radiation emitted by said filament and consisting of a layer of a substantially pure metallic oxide containing no binding agent, said layer having been applied whilst in a molten state to an area of said exterior surface, thereby causing said layer to be fused in a substantially permanent manner to said exterior surface without a binding agent, so that, when heated by radiation from said filament, said coating undergoes substantially no discoloration, and wherein said coating possesses a variable thickness which is a maximum in a central region of said area of said exterior surface and a minimum in a peripheral region of said area.
Dependencies are inferred from the claim text.