GB405605A - Improvements in luminous electric discharge tubes - Google Patents

Abstract

405,605. Discharge lamps. GENERAL ELECTRIC CO., Ltd., Magnet House, Kingsway, London, FRANCIS, V. J., and RYDE, J. W., c/o General Electric Co., Wembley, Middlesex. July 1, 1932, No. 18682. [Class 39 (i).] In a luminous electric discharge tube of the high pressure type, the electrode, from which one or more wires extend to the wall of the tube, is placed so near to the end wall of the tube that this end wall is heated by energy dissipated in the discharge and in the electrode to a temperature not lower than that of the coolest part of the main wall and the length of the wire or at least one of the wires is substantially greater than the shortest distance between the said electrode and the end wall of the tube. The wire or wires may be carried through some part of the wall of the tube which is not an end wall or may be curved or coiled. The internal tube 1 has ends approximately spherical apart from the protuberances at the seals where the lead 3 pass through the glass. The leads 3 are welded to the ends of a tungsten spiral 4 part of which surrounds a short refractory rod 5 composed of mixture of calcium and barium oxides, two turns 6 of the spiral free from the rod being used as the curved leads. The tube 1 is arranged within an outer envelope 7 having a foot-tube 8 and standard cap 12. The leads 9 are welded to supporting rings 13 bearing against the inside of the outer envelope 7. The mercury atmosphere inside the tube 1 may contain a small proportion of argon to facilitate starting. To render the tube self-striking, a wire 10 may be carried from one lead 9 along the outside of the tube 1 and wound round the outside of the tube to form a conductive rung 11 or an auxiliary electrode may be put inside the tube near one of the main electrodes and connected to the other electrode through a high resistance. To promote further the heating of the ends of the tube, the ends may be covered with caps of thin foil.