GB638805A - Improvements in and relating to electric incandescent lamps - Google Patents

Abstract

638,805. Electric incandescent lamps. BRITISH THOMSON-HOUSTON CO., Ltd. July 9, 1948, No. 18548. Convention date, July 12, 1947. [Class 39 (ii)] In an electric lamp, particularly of the high wattage type, the leading-in conductors to the two ends of the filament 11 each comprise a spud or inserted plug portion 26 of metal such as molybdenum or tungsten over which a helical compression coil 31 and the coiled end portion 30 of the filament are fitted, these two coils being screwed together throughout a portion only of the length of the compression coil and compressed between opposed shoulders 27, 29 provided on the spud. The shoulder 27 is formed by flattening the end 28 of the spud, and shoulder 29 may be provided by a clip or lug 25 the ends of which are pinched tightly around the spud 26 and a supporting conductor 10. Alternatively, the upper end of the conductor 10 may be bent inwardly at right-angles and the upper end of the spud welded thereto, or a flat plate may be welded across the upper ends of the members 10 and 26. In forming the joint with the filament the compression coil 31 and filament end coil 30 are first screwed together for an overall length less than the designed distance between the shoulders 27, 29, and the unflattened end of the spud is then inserted through the inter-threaded coils and either clamped in the lug 25, or welded in the manner stated, after which the two coils 30, 31 are partially unscrewed until their respective outer ends abut against the shoulders 27, 29. This contact between the shoulders and the ends of the coils short circuits the filament end-coil 30 and ensures a uniform effective length of filament.