GB378333A - Improvements in electric lamps - Google Patents

Abstract

378,333. Discharge lamps. GENERAL ELECTRIC CO., Ltd., Magnet House, Kingsway, London.-(Assignees of Patent-Treuhand - G e s. fur Elektrische, Gl³hlampen; 11, Ehrenbergstrasse, Berlin.) Feb. 9, 1932, No. 3864. Convention date, Feb. 23, 1931. [Class 39 (i).] In arc lamps or other discharge lamps with the leads 9, Fig. 1, to the solid electrodes 10 bridged bv a filament 11 emitting electrons to start the discharge, the filament is loosely attached to the leads. Contact resistances thus set up at the point of attachment do not affect the flow of current through the filament at starting but prevent heavy current flow after the arc has started and so prevent the arc forming on the filament and damaging it. A helical filament may have its ends threaded over hooks or loops 12 on the leads 9 and its centre supported at 13. The blockshaped or spherical electrodes may be of tungsten or a mixture of electron-emitting substance and tungsten or other refractory metal. The bulb 1 may be of quartz or borosilicate glass transparent to ultra-violet rays and may contain a pod 18 of mercury and argon or nitrogen. In a modification, a circular filament is threaded through the loops 12. In a further modification, Fig. 3, headed pins 20 rest in apertures in flat parts 19 of the leads 9 and are welded or clamped to the filament 11. The loosely attached filament may be applied to glow-discharge tubes with electrodes heated by the discharge or by auxiliary means and with gas or vapour fillings.