GB307424A - Electric discharge tubes - Google Patents

Abstract

307,424. Wedel, C. J. R. H. von. March 7, 1928, [Convention date]'.. Vacuum tubes; low-pressure metallicvapour apparatus.-A glow-discharge tube for the emission of ultraviolet or luminous rays comprises an elongated discharge path extending in two directions from a single stem 5 which carries the two electrodes 2, 3 and a partition 4 between them to compel the discharge to take the long path around the tube. In the construction shown in Fig. 1, both electrodes are of the incandescent type to enable alternating current to be used. The filaments are of thoriated tungsten or are coated with emissive material, preferably amphoteric compounds to withstand ionic bombardment. The shield 4 may be of metal or have a metal coating and may be connected to a source of potential, e.g. the primary winding 8 of a transformer which is mounted in the base 11 of the lamp to feed the filaments 2, 3. Resistances 9, 10 in series with the main discharge path are also mounted in the base, which is' provided with a plug 12 for insertion in a lamp-holder. The wall of the base may be double and the resistances wound within it, as shown in Fig. 3. Cooling-fins 24 may be provided. In the construction shown in Fig. 3, the electrodes 17, 18 are of the cold type and auxiliary electrodes 19 facilitate starting the discharge. In addition to the resistances 9, 10 for the main discharge path, resistances 15, 16 are provided for the auxiliary discharge path, these being arranged as described in Specification 306,413. Mercury or other metal vapour may be added to the gas filling for the emission of ultra-violet rays.