GB806946A - Improvements in or relating to gas-filled electric discharge devices - Google Patents

Abstract

806,946. Discharge tubes. GENERAL ELECTRIC CO. Ltd. May 28, 1956 [May 26, 1955], No. 15292/55. Class 39(1). A gas filled electric discharge device, preferably a hydrogen filled lamp for D.C. operation, has a gas reservoir in the form of a container 14 of electrically resistive material substantially filled with a substance (Ti in the case of a hydrogen filling) which evolves gas on heating and reabsorbs it on cooling, the container 14 having apertures of such size that the substance cannot escape but gas can pass freely in or out, the container 14 having leads 18, 19 for passage of heating current through the material of the container along the walls of the container so as to heat the container, the arrangements being such that when the container is unheated the gas pressure is small compared with the desired operating pressure. In the form shown the gas reservoir contained inside tube 13 comprises four similar tubes 14 of 28 per cent. Ni, 18 per cent. Co and 54 per cent. Fe having helically arranged apertures and having Ti chips therewithin. The tubes 14 are connected by three lengths 15 of nickel wire which are inserted in and seal the ends of the tubes 14 to which they are spot welded, the current leads 18, 19 being similarly secured to the free ends of tubes 14. Two annular ceramic spacers 16, 17 strengthen the assembly and bent nickel spring strips 20 keep it centrally in the side tube. After assembly and processing but before sealing off the hydrogen is introduced and absorbed in the titanium until there are 60 ccs hydrogen at normal temperature and pressure contained in the titanium. The heating current through 18, 14, 19 is 8 amps. at 4 volts which heats 14 to 550‹C., and an operating equilibrium pressure of 5 mm. Hg is reached in 45 seconds from the time of application of the heating current. For no heating current substantially all the hydrogen is reabsorbed by the titanium, the residual hydrogen pressure being less than 0À005 mm. Hg. The cathode 1 is a helix of W-Mo alloy and is surrounded by a nickel cylinder 2 closed at each end followed by a semicylindrical nickel anode 3. The anode 3 is supported at one end from cylinder 2 by an insulating glass bead 9 and at the other end by current lead 10. Electrodes 2, 3 have slits for light to emerge through quartz window 5 which is cemented by wax to side tube 6. The cemented wax seal is cooled by water circulation through tubes 7, 8. The invention can also be applied to other forms of gas filled electric discharge device including devices with mixtures of gases in which case the resevoir keeps the pressure of one gas constant. Specification 806,945 is referred to.