US 4,065,694 AGranted

Regenerative-cycle incandescent lamp containing SnI.sub.4 additive

AssigneeWestinghouse Electric Corp.

InventorAvinash D. Kulkarni

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Abstract

The quality and useful life of regenerative-cycle type incandescent lamps that employ iodine as the halogen are enhanced by dosing the lamps with a carefully controlled amount of SnI.sub.4 which decomposes when the lamp filament is energized and provides from about 0.05 to 0.20 micromole of vaporized elemental iodine per ml. of bulb volume within the lamp during operation. The resulting increase in the amount of iodine that is converted into atomic rather than molecular form within the energized lamp permits elongated iodine-cycle lamps having singly-coiled filaments to be operated in any position in contrast to conventional iodine-cycle lamps of the same configuration and construction that exhibit early blackening of the top portion of the envelope when the lamp is operated in a vertical position. The undesirable light-absorption and color distortion effects characteristic of conventional iodine-dosed lamps are also reduced, thus increasing the lamp efficiency.

Claims6

Dependent claims

A regenerative-cycle incandescent lamp of elongated configuration that is adapted to be operated at a selected wattage and have a nominal design life in excess of 1000 hours when operated at said wattage, said lamp comprising;

a sealed envelope of light-transmitting material that contains a coiled filament which is composed essentially of tungsten and is supported in longitudinally-extending position within said envelope,
a pair of spaced conductor means extending through said envelope and connected to said filament,
an inert gas within said envelope at a pressure of at least 1000 torr, and
means in said envelope for initiating and sustaining a tungsten-iodine cycle within the lamp during the operation thereof which inhibits discoloration of the envelope by vaporized tungsten even when the lamp is operated in a non-horizontal or vertical position at said selected wattage, said means consisting essentially of SnI.sub.4 in an amount sufficient to provide from about 0.05 to 0.21 micromole per ml. of lamp volume of elemental iodine within the envelope when the lamp is operated at said selected wattage and the SnI.sub.4 is subjected to the heat and radiant energy generated by the energized incandescent filament.

1 more element

Dependencies are inferred from the claim text.