GB704181A - Improvements in and relating to electric incandescent lamps - Google Patents

Abstract

704,181. Electric incandescent lamps. BRITISH THOMSON-HOUSTON CO., Ltd. June 28, 1951 [July 1, 1950], No. 15374/51. Class 39 (2) An electric lamp comprising a sealed envelope having a focusing reflector 6 for producing a long beam of parallel rays, for use, for example, as a high-wattage spotlight connected to a normal mains supply, is provided with a pair of rigid leading-in conductors 21 which are offset inwardly at their inner end portions 24 to form end supports for a coiledcoil filament 25 consisting of three individual segments 27-29 which are interconnected at their ends and arranged substantially in an N or Z-shape in a plane passing through the axis of the reflector, the filament being provided with intermediate supports 33, 34 at the junctions of the segments to hold it centred substantially about the focal point of the reflector, with the centre segment 28 extending axially of the reflector and with its mid-point located substantially at the focal point. In order to concentrate the filament about the focal point F of the reflector the angle of divergence between the adjacent segments is preferably made relatively small, and the outer segments 27 and 29 are made shorter than the centre segment 28, e.g. about half the length. The intermediate supports 33, 34 are mounted in an insulating-bridge comprising a glass rod 35 with pairs of supporting wires 37 sealed within its ends and welded or otherwise secured to the leading-in conductors 21. A limited amount of free movement of the filament is permitted by hooking or looping the filament bights 30, 31, Fig. 2 (not shown), loosely over U-shaped hooks at the extremities of the supporting wires 33, 34, which are preferably arranged to maintain the segments tensioned between their points of support. In a modification, Fig. 3 (not shown), the end portions of the leading-in conductors are bent inwardly at right-angles towards one another, and the ends of the filament, each extending in the same direction as the segment of which it forms part, are clamped beneath the reversely bent extremities of the leading-in conductors. Specifications 515,091 and 682,500, and U.S.A. Specification 2,436,259 are referred to.