GB789078A - Improvements in or relating to colour modified incandescent electric lamps - Google Patents

Abstract

789,078. Luminescent materials: discharge apparatus. WESTINGHOUSE ELECTRIC INTERNATIONAL CO. Oct. 19, 1954, No. 30032/54. Class 39(1). An incandescent electric lamp 12f Fig. 2, comprises an incandescible source 25f, consisting of a filament or Welsbach mixture or Nerust glower comprising a rod-like filament formed of metal oxides such as thoria with 1 per cent ceria, giving rise to visible and U.V. radiations and thermionic electrons, a translucent envelope 22f of quartz or hard glass surrounding the source, an electrically conductive coating 34f on the inner surface of the envelope constituted by or including a phosphor for which production of light in the green region of the spectrum is high upon impingement thereon by U.V. radiation and electrons from the source 25f, and means, such as a resilient extension 37 from the lead 18f to the coating 34f, whereby a potential is applied between the coating 34f and the source 25f to aid electron flow therebetween. The visible light from the source forms a substantial proportion of the total visible light from the source and phosphor. The lamp can be used on A.C. or D.C. and the filament can be of tungsten or thoriated tungsten. The coating 34f can comprise a conductive glass or glaze containing tin oxide or a conductive tin and antimony compound to which a phosphor coating is applied or the phosphor coating can be mixed with conductive material if not naturally conducting. Phosphors referred to are manganeseactivated zinc orthogermanate, zinc-activated zinc oxide and manganese-activated zinc fluoride which can be evaporated as a thin clear film. The envelope 22f can be either evacuated or contain an inert or rare gas such as nitrogen, argon, neon, krypton or xenon or mixtures thereof. In a modification of the construction shown in Fig. 2, the phosphor coating is electrically connected to the mid-point of the filament for use on A.C. or D.C. In the construction shown in Fig. 4 for use on A.C., the mid-point 38h of the filament 25h is connected to the negative pole of a battery 39 through the ring contact 41 of the base 21h, the positive pole of the battery being connected to the phosphor coating 34h by a lead 42 through the envelope 22h. In the construction shown in Fig. 5 for use on A.C., the negative pole of the battery 39k is connected to one end of the filament 25k through the shell of the base 21k, the positive pole being connected to the phosphor coating 34k by an auxiliary lead 42k from the ring contact 41k of the base and a resilient contact member 37k. In the construction shown in Fig. 6 for use on A.C. or D.C. the source 25m is enclosed in a quartz bulb 43 supported by leads 17m, 18m within an outer envelope 22m. The phosphor coating 34m is applied to the inner surface of the bulb 43 and a contact 37m extends between the source 25m and the coating 34m. The size of the phosphorcarrying envelope in each embodiment is preferably such that during operation the envelope is maintained substantially at the optimum temperature for the generation of visible light by the phosphor coating. Current limitation of the discharge may be effected by a separate series resistance, by the semi-conductive property of the phosphor coating, by a choke or another ballasting device.