GB400764A - Improvements in electric discharge tubes - Google Patents

Abstract

400,764. Discharge lamps. NAAMLOOZE VENNOOTSCHAP PHILIPS' GLOEILAMPENFABRIEKEN, 13D, Emmasingel, Eindhoven, Holland. Sept. 20, 1932, No. 26164. Convention date, Nov. 28, 1931. [Class 39 (i).] An electric discharge tube; with a gaseous filling and electrodes so spaced that the discharge has the characteristic of an arc discharge without a positive column, is provided with two incandescent cathodes 3 4, respectively connected to anodes 9, 10 adjacent thereto. The cathodes 3, 4 are helically wound and coated with an electronemitting layer, such as an alkaline earth oxide, the anodes 9, 10 being in the form of nickel cylinders surrounding the cathodes. The distance between the anodes is less than that between the cathodes, and the supply conductors of the electrodes are taken out at one end of the tube, through the stem 2. The cathodes 3, 4 are respectively connected to pole wires 5, 6 and 7, 8 preferably coated with a layer of insulating material such as magnesium oxide or surrounded by a tube of that material, the anode 9 being connected to the wire 6 by a supporting-wire 11, and anode 10 connected to the pole wire 7 by a supporting-wire 12. Alternatively the anodes may be connected outside the tube to the cathode supply conductors. In the example the discharge tube is operated by a transformer 13 with a primary winding 14 and a secondary winding 15 which comprises a few turns 16 supplying current to the cathode 4, and turns 17 supplying current to the cathode 3. With this arrangement, when the anode 9 has a positive potential with respect to the cathode 4 it is also positive with respect to the cathode 3, so that during the discharge the proportion of current passing from the anode 9 is greater than that from cathode 3. The filling may consist of one or more gases or vapours, or a mixture of a rare gas and a vapour such as sodium vapour may be used to produce an intensive light source.