GB518925A - Improvements in high-pressure metal-vapour electric discharge lamps - Google Patents

Abstract

518,925. Metal-vapour lamps. GENERAL ELECTRIC CO., Ltd., FRANCIS, V. J., PEARCE, A. G., RYDE, J. W., and STEVENS, W. R. Aug. 29, 1938, Nos. 25283 and 37285. [Class 39 (i)] A high-pressure metal-vapour electric discharge lamp working at a pressure greater than 3 atmospheres, has the discharge envelope surrounded by a stout opaque casing, preferably of metal, forming an integral part of the lamp and pierced by one or more apertures for the emergent light, the area of these apertures not being sufficient to diminish substantially the protection which the casing gives against the effect of a burst of the lamp. The apertures may be closed by glass, which may take the form of a lens, and the leads may be taken out through one or more extensions of the casing so formed and located as to remain much cooler than the part of the casing immediately surrounding the lamp. In the form shown, the nickel-iron casing 6 has an opening 7 closed by inner and outer glass plates. The leads pass through strip seals, 3, 5 and tubes 4, to a chamber formed by a partition 10 and having air holes 16 for cooling the bare part of the leads. One lead may be connected to the casing or they may be brought out through insulating bushes at opposite ends of the lamp or a single bush at one end. In a further form the envelope is surrounded by a sealed vitreous jacket which may be either inside or outside the casing, and may be evacuated or filled with a gas which does not attack the leads. The casing may be fitted with a cap with contacts to which both leads are connected. The corresponding socket may be part of a second opaque casing also provided with an aperture which is preferably glazed, to give double protection.