GB447428A - Improvements relating to electric lamps - Google Patents

Abstract

447,428. Supply systems for discharge lamps. SIEMENS ELECTRIC LAMPS & SUPPLIES, Ltd., Caxton House, Tothill Street, Westminster, and LE MERECHAL, W. H., and ALDINGTON, J. N., c/o Siemens Electric Lamps & Supplies, Ltd., Dock Road, Preston, Lancashire. Dec. 8, 1934, No. 35343. Drawings to Specification. [Class 38 (iv)] [See also Group XL] An electric lighting unit comprises a highpressure mercury-vapour lamp and in series therewith a resistance having a positive temperature coefficient, some or all of which resistance is light-emitting, arrangements being made to cut out automatically part of the resistance, which part includes always any light-emitting part, when the voltage across the lamp approaches its working valve. The resistance may be a gas-filled metal filament lamp with a tapped filament part of which may be short-circuited, or a number of lamps, some of which may be switched out. An electromagnetic switch responsive to the voltage of the lamp may be used, but preferably a bimetallic switch is actuated by the heat of the discharge lamp. A mercury-vapour lamp is described which is combined with a tapped tungsten filament, a portion of which is adapted to be short-circuited by a bimetallic switch. The discharge lamp contains mercury and additional quantities of metal such as zinc and cadmium which give the lamp a rising voltage - current characteristic more nearly resembling that of the tungsten filament than does the nearly flat characteristic of a pure unsaturated mercury filling. Voltage fluctuations in the supply mains are thus distributed more evenly between the discharge lamp and the filament. Dimensions and details of electrical performance are given for the lamp described. Specification 431,382, [Group XL], is referred to.