GB399317A - Improvements relating to metal vapour lamps - Google Patents

Abstract

399,317. Discharge lamps. QUARZLAMPEN-GES., Hanau, Germany. Oct. 8, 1932, No. 28109. Convention date, Oct. 10, 1931. [Class 39 (i).] In a high-pressure metalvapour arc lamp with solid electrodes, i.e. a lamp in which the arc moves away from the envelope and becomes constricted and intensely luminous, the metal forming the arc is present in the working condition of the lamp only in the form of vapour. In such a lamp the temperature is always above the condensation, temperature of the metal, so that at the coolest part of the tube, the vapour is superheated, or, at least, dry saturated ; the static characteristic is such that the increase in voltage with increasing load is small while the increase in current is larger. As shown, the electrodes 2, 3 consist of basinshaped members piled within one another, or of a closely-wound spiral strip of metal. Barium oxide is inserted in the spaces between the basins or turns. The tube contains argon and a small quantity of mercury or cadmium or a mixture of these metals. Starting is effected by means of an auxiliary electrode or by means of a strip of material known by the registered Trade Mark "Aquadag," applied on the outside of the envelope in two parts separated by a gap. Heat insulation 6 is provided on the ends of the envelope, so that when the lamp is switched off, metal is condensed on a part of the wall traversed by the discharge.