GB818075A - Improvements in infrared lamp device - Google Patents

Abstract

818,075. Electric lamps. GENERAL ELECTRIC CO. March 14, 1956 [March 29, 1955], No. 7985/56. Class 39(2) An infra-red generating lamp comprising a sealed envelope of vitreous material containing a coiled tungsten filament designed for operation at a temperature of about 2400‹K. to 2500‹K. is characterized by the pitch of the coil being between 140 per cent and 220 per cent, preferably in the range of 180-200 per cent, and by the wire diameter and length of the coil being proportioned to dissipate in excess of 0.5 watts per square millimeter of wire surface area at a current density in excess of 0.029 amperes per milligram weight of the wire. The term "per, cent pitch" is defined as the ratio, in per cent, of the distance between centres of adjacent coil turns and the diameter of the coil wire. The coils are preferably prepared at a pitch of about 180 per cent and ultimately stretched to 196 per cent pitch during assembly into the lamp envelope. In the example the lamp comprises an elongated tubular envelope 1 consisting essentially of fused silica, such as clear crystal quartz, transluscent sand quartz, or a quartz-like glass, containing approximately 96 per cent silica, and containing a filling of rare gas such as argon, krypton, xenon, or mixtures thereof, preferably at a pressure of about one atmosphere. The opposite ends of the filament 2 are connected to leading-in conductors 3 by means of short coils of tungsten wire 5 fitting tightly around the prospective leading-in conductors and screwed into the ends of the filament. The intermediate portions 7 of the leading-in conductors within the flattened press or sealed portions 4 of the envelope are flattened to a thickness of between 0.01 and 0.025 mm. by a longitudinal rolling operation which produces a longitudinal crystal orientation therein. Intermediate supports for the filament are provided by centrally perforated spaced discs 6, preferably made of a refractory metal such as tantalum which also functions as a getter.