GB409235A - Improvements in electric lamps - Google Patents

Abstract

409,235. Electric lamps. GENERAL ELECTRIC CO., Ltd., Magnet House, Kingsway, London.-(Assignees of Patent Treuhand Ges. fur Elektrische Gl³hlampen; 11, Ehrenbergstrasse, Berlin.) Nov. 20, 1933, No. 32329. Convention date, Dec. 21, 1932. [Class 39 (ii).] In gas-filled electric lamps of the kind wherein illumination is provided by a helical incandescent filament in addition to an arc discharge which takes place between the ends of the filament, the filament 15, Fig. 1, is wound in the form of double helices 13, 14 near the leading-in wires, to constitute the electrodes of the arc discharge. The leading-in wires may be formed by helices 9, 10, Fig. 1, of stout tungsten wire which are welded at one end to metal rods 7, 8 and bent at right-angles along their length, the ends 11, 12 of the helical filaments being slid through the helices 9, 10 and welded to the rods 7, 8. To increase the cross-section of the coils acting as leading-in wires and electrodes a mandrel 19 of tungsten wire is inserted into each of the end portions 11, 12 and their associated coiled helices 13, 14, so that only the portion 15 is without a core. This latter portion is disposed substantially at right-angles to the helices 13, 14 and may be bent into S-shape, with additional supports 16, 17 of thin molybdenum wire fastened to an insulating body 18 mounted between the rods 7, 8. The single turns of the double coils 13, 14 may be spaced uniformly, as shown in Fig. 2, but are preferably in contact at the upper portions of the coils to provide a larger surface for the arc discharge. In a modification the end portions 12, Fig. 4, of the double coils are welded directly to a bent rod 20 mounted on the metal rod 8. Preferably the bulb 1 contains a quantity 21 of mercury or an amalgam.