GB459250A - Improvements in electric discharge devices - Google Patents

Abstract

459,250. Discharge lamps. GENERAL ELECTRIC CO., Ltd., Magnet House, Kingsway, London.-(Patent Treuhand-Ges. f³r Elektrische Gl³hlampen; 11, Ehrenbergstrasse, Berlin) Oct. 15, 1935, No. 28503. [Class 39 (i)] In a high-pressure metal-vapour electric discharge lamp wherein the vapour pressure during operation is 8 atmospheres or more, the electrodes 4 are in the form of a thickwalled tungsten, perforated container 7, in which is packed a mixture of a refractory oxide, a refractory metal and a thermionically emitting material. One composition consists of 90 per cent alumina, 9 per cent tungsten powder, and 1 per cent barium oxide ; another consists of 80 per cent alumina, 10 per cent tungsten and 10 per cent barium oxide. The least distance between the electrodes is less than the distance between either electrode, and the wall of the envelope. The interior of the envelope has heat reflecting coatings 12 ; the coatings may be of asbestos. The gap 11 may be replaced by a window for the light to issue, the whole of the envelope apart from the window having a coating. Heat shields 8, 10 protect the walls and seal of the leads. The lamp is particularly adapted for use with impulsive discharges for cinematography, but the form shown in Fig. 2 is for use when the pressure is above 20 atmospheres, and the lamp is operated continuously and not by impulsive discharges.