GB698421A - Improvements in or relating to electric discharge lamps - Google Patents

Abstract

698,421. Discharge lamps. GENERAL ELECTRIC CO.; Ltd., and BOWTELL, J. N. Sept. 4, 1951 [Sept, 4, 1950], No. 21804/50. Class 39(i) A flash lamp for photographic or stroboscopic work is provided with a filling of one or more rare gases and with electrodes having metallic surfaces which can be activated by alkali metal contained in an amalgam in contact with, or adapted to be brought into contact with, the electrodes. An amalgam which is liquid at room temperature is preferable and may contain potassium and mercury in the ratio of between 1 to 20 and 1 to 40. The lamp may attain a temperature during operation of 100‹C and the mercury pressure may be 0.5 to 1 mm. The rare gas filling may be xenon, argon, neon or krypton at low or high pressure. Lamp dimensions and the amount of amalgam in the lamp are specified. U-shaped lamps 1 are connected by side tubes 3 and 4 to a manifold 5 the ends 6, 7 of which are connected respectively to a vacuum pump and a supply of rare gas. A U-tube 8 contains specified quantities of mercury 10 and potassium 11 and has its open end sealed off. The lamps and manifold are evacuated, the lamp baked without heating the mercury or the potassium, and the mercury is then warmed to remove air bubbles whilst the manifold is still connected to the pump The potassium is distilled over to combine with the mercury, the lamps filled with neon at 10-20 mms. and the cathodes bombarded by a discharge current for a few seconds; the lamps are again evacuated, allowed to cool and a mixture of neon and argon in the volumetric proportions of 10 to 1 and at a pressure of 1-10 mm. is introduced. The manifold is sealed at the end 7 and the assembly tilted so that the specified quantity of amalgam runs into each lamp which is then sealed off. The activation of the electrodes may be effected before or during the ageing process.