GB722165A - Improvements in or relating to tubular electric discharge lamps - Google Patents

Abstract

722,165. Discharge lamps. PHILIPS ELECTRICAL INDUSTRIES, Ltd. Oct. 10, 1952 [Oct. 13, 1951; Oct. 23, 1951], No. 25431/52. Class 39 (1). A tubular discharge lamp, which may be fluorescent, comprising two activated main electrodes 3, and at least one auxiliary electrode 10, 11 of resistance material arranged on the inner wall of the discharge tube 1 and connected to one of the main electrodes and extending over at least one third of the length of the discharge tube, is characterized in that the discharge. tube 1 is formed in the shape of a ring, and that the or each auxiliary electrode 10, 11 is coincident with or spaced from the smallest internal ring circumference of the discharge tube by a distance which is not more than #, preferably not more than 1/15 of the internal tube circumference. The auxiliary electrodes 10 and 11 are strips of about 3 mms. width made of a mixture of graphite and glazing with a resistance of about 20 ohms per cm. In the construction shown in Figs. 1 and 2, the auxiliary electrode 11 is connected to the main electrode 4 by a metal strip 15 and a short metal wire 16 and ends adjacent the other main electrode 3. The auxiliary electrode 10, Fig. 1, is similarly connected to the main electrode 3. The internal tube diameter is about 30 mms. and the diameter of the central line 12 of the ring is about 37 cms. The tube has a filling of mercury and argon at a pressure of about 3 mms. The electrodes 3, 4 are connected to supply terminals 7, 8 through a stabilizing resistor 9, e.g. an incandescent lamp. In the case of AC supply the resistor 9 may be replaced by an inductor, a capacitor, combinations thereof or other impedances having a positive current voltage characteristic curve. The tube 1 is made from a straight tube on the inner wall of which the fluorescent layer 2 and the auxiliary electrodes 10 and 11 have already been arranged, the straight tube being bent in the plastic condition around a central templet, discontinuities in the material of the auxiliary electrodes being obviated by the spacing of the auxiliary electrodes from the smallest internal ring circumference of the tube being not more than # of the internal tube circumference. In the construction shown in Figs. 3 and 5 the auxiliary electrode 15 is connected to the main electrode 14 by a ferro-chromium strip 16 and a helically wound tungsten wire or spring 17. The axis of the helix 17 and the electrode 14 are perpendicular to the plane of the central line of the auxiliary electrode 15. The helical tungsten wire 17 has a wire diameter of about 250 microns, a helix diameter of about 4 mms., and about 3 turns. The internal tube diameter is about 30 mms and the largest ring diameter of the tube about 40 cms. The pinches 12 of the tube are perpendicular to each other. At least one of the leading-in wires 13 for each electrode 14 is connected' by series impedance 18, e.g. an incandescent lamp, to a terminal of the supply source.