GB485476A - Improvements in and relating to electric incandescent lamps - Google Patents

Abstract

485,476. Discharge lamps. GENERAL ELECTRIC CO., Ltd. (Patent Treuhand Ges. f³r Electrische Gl³hlampen) Nov. 25, 1936, No. 32274. [Class 39 (i)] [Also in Group XI] In an electric lamp in which at least a substantial part of the light comes from a filament heated to incandescence by the passage of current through it, the envelope enclosing the filament contains an amount of mercury which is limited so that it is all evaporated when the lamp is in its normal operating condition and thereby generates a pressure of not less than half an atmosphere. The amount of mercury may be so adjusted that it is all evaporated when the lamp is consuming steadily substantially 90 per cent of the power that it consumes in normal operation, and the pressure of the vapour during normal operation may lie between 0À5 and 20 atmospheres. A rare gas such as the usual argon-nitrogen mixture is preferably mixed with the mercury vapour to prevent evaporation of the electrodes while the lamp is heating up. Alternatively krypton or xenon, or a mixture thereof may be added. An incandescent lamp and a high-pressure metal vapour lamp may be combined in the same envelope. The lamp may be in the form of a quartz or hard glass tube with a longitudinally arranged coiled-coil filament or a rod of tantalum carbide or the like provided with leading- in wires sealed in at opposite ends of the tube. Fig. 3 shows a filament 2 in series with a discharge path 11 between electrodes 9, 10, there being a porous partition 8 between the discharge space and filament space. A starting electrode 12 is connected to the electrode 10 through a resistance 13. In a modification the discharge space is located at the central portion of the tube, with a filament at each end. Fig. 5 shows an inverted-U-shaped tube with a horizontal portion providing the discharge space 11 and filaments 2, 2<1> in the vertical limbs. The filament and discharge paths may be located within separate envelopes both enclosed in a common bulb or jacket adapted to transmit ultra-violet light; it may also be frosted on its interior surface and may carry luminescent material adapted to be excited by the radiation. Specification 398,840 is referred to.