GB923294A - Improvements in bent end incandescent lamp - Google Patents

Abstract

923,294. Electric incandescent lamps. GENERAL ELECTRIC CO. Nov. 30, 1960 [Dec. 11, 1959], No. 41170/60. Class 39 (2). A double-ended elongated incandescent lamp, which may be an infra-red lamp, comprises a sealed gas-filled tubular envelope of vitreous material, elongated lead-in wires extending a substantial distance inwards at each end of the envelope and an incandescible filament extending between the inner ends of the lead-in wires, the envelope being punch sealed onto the lead-in wires adjacent their inner ends and compressed and sealed on to the lead-in wires at the ends of the envelope, the parts of the envelope between the ends and the inner pinches extending laterally of the main body. The envelope may be of quartz and the lead-in wires of molybdenum with foliated portions within the end seals. The filament 3, Fig. 4, may be a coiled tungsten wire supported at intervals by tantalum discs 3 and joined to lead-in wires 4 having flattened portions 5 for sealing into the envelope. The envelope is bent at 14 and collapsed on to the inner ends of the lead-in wires. In one method of making the lamps, the filament 2, supports 3 and lead-in wires 4 are supported within a vertically arranged tube 1 the upper end of which is closed by a plug 7, Fig. 1, above which is a cap 6 having a spring-urged pivoted jaw 9 and clamping screw 8 to hold the end of the lead-in wire. The end of the other lead in wire is held in a chuck 12. Inert gas, e.g. argon, is introduced into the envelope through a side tube 13. The envelope is first heated and collapsed around the lower lead-in wire to an I-section as shown in Fig. 6 leaving passages 15 and the lower end of the tube is sealed off. The tube is then inverted and the process repeated. The tube is finally bent at the collapsed portions and the side tube 13 sealed and tipped off. In a modification for making tipless lamps, the inert gas is introduced by means of a hollow needle inserted into the lower end of the tube and removed after the lower end has been heated but before it is sealed. In a further modification, the formation of the collapsed areas at the inner ends of the lead-in wires is carried out after the ends of the envelope have been sealed and the envelope is bent to the desired angles while the collapsed areas are still soft.