GB797828A - Improvements in and relating to electric incandescent projection lamps - Google Patents

Abstract

797,828. Electric incandescent lamp filaments. BRITISH THOMSON-HOUSTON CO., Ltd. June 1. 1955 [June 2, 1954], No. 16340/54. Class 39(2) The coiled filaments of a projection lamp are arranged in sections with the axes of the coils of the sections arranged substantially parallel to one another to lie in three substantially parallel planes A, B, and C, and with the coil sections in the two adjacent planes A and B in staggered relation to one another, and each of the sections a<SP>1</SP> which have their axes lying in the third plane C are located so that their respective axes are positioned on the centre line of a gap b otherwise visible between the sections which have their axes in the two planes A and B. The arrangement shown is a modification of a conventional arrangement comprising the same number of coil sections viz. eight disposed in two parallel rows of four, with the sections of one row staggered relative to those of the other row, thereby resulting in considerable gaps between the sections of the filament when viewed at angles other than perpendicular to the planes containing the axes of the said sections, thereby producing a non- uniform light emission. In the arrangement shown the distance R between the centres of the coils in the adjacent planes is the same as for the conventional two row arrangement referred to. Curves, Fig. 3 (not shown) are furnished illustrating the relative increase of average brightness attained with the modified arrangement of the coils.