GB474907A - Improvements in lighting by gas and vapour discharge tubes with fluorescence - Google Patents

Abstract

474,907. Discharge lamps. TENNANT, W. J. (Soc. Anon. pour les Applications de l'ElectricitÚ et des Gaz Rares Etablissements Claude-Paz & Silva) May 9, 1936, No. 13125. [Class 39 (i)] [Also in Groups XI and XX] Radiation from a gas or vapour filled discharge tube is allowed to fall on a first layer of fluorescent material which transforms ultraviolet radiation of short and medium wavelength into visible and long wavelength ultraviolet radiation; the transformed radiation passes through a transparent wall or space and falls on a second layer of fluorescent material which transforms ultra-violet radiation of long wavelength into visible radiation, while allowing the visible radiation to pass. The ultraviolet radiation of the lamp is transformed into resultant light, the spectrum of which is sensibly similar in energy distribution to that of the sun. The first material may be calcium tungstate, benzene or calcium sulphide with gadolinium phosphorogen ; the second material may be zinc or cadmium sulphide or mixtures of these. A third layer of a fluorescent substance may be provided for further correction of the spectrum. Both layers may be inside the tube, and separated by a thin layer of boric acid, or the first layer may be inside the tube and the second layer on the outside of the tube or on an external screen or envelope surrounding the tube. When both layers are outside the tube, they may be on detachable cylindrical screens surrounding it or, as shown in Fig. 2, the second material may be coated on the inside of a jacket 6, preferably evacuated, which surrounds the tube 1, the first material being on a hood 4 within the jacket. The first material may be placed on the inside of the jacket, when the second material is on a removable bulb surrounding it or, as shown in Fig. 4, on the front glass 5 of a reflector 9 within which the double-walled lamp is situated. Those parts of the envelopes or screens which are to pass short ultra-violet radiation may be of quartz and those which are to pass long ultraviolet radiation may be of glass known under the Registered Trade Mark " Pyrex." The discharge tube may be filled with argon, krypton, or xenon.