GB400368A - Improvements in devices comprising a gasfilled electric discharge tube having one ormore incandescent electrodes - Google Patents

Abstract

400,368. Discharge apparatus. NAAMLOOZE VENNOOTSCHAP PHILIPS' GLOEILAMPENFABRIEKEN, 13D, Emmasingel, Eindhoven. Holland. July 20. 1932, No. 20515. Convention date, July 25, 1931. [Class 39 (i).] Heating current for one or more incandescent electrodes of a gas- or vapour-filled, luminous, positive-column discharge tube such as an advertising sign is supplied by secondary windings of a transformer having its primary between and in series with the discharge path and the current source supplying the discharge. The primary of the heating-current transformer thus acts as a series impedance, but a resistance, inductance or capcaity may be used as an additional impedance. A long tube 1, Fig. 1, filled with argon at 2 mm. and mercury and provided with oxide-coated helical electrodes 2, 3 has these electrodes heated by secondaries 4, 5. When the tube is connected to the A.C. supply 7, a glow-discharge causes alternating current through the primary 6, the electrodes heating up and an arc accompanied by a positive-column forming. If no or an insufficient glow-discharge is produced, the tube 1 may be shorted at 9 until the electrodes 2, 3 are hot, the switch 9 being opened by hand.or by a bimetallic strip. In a modification, one of the electrodes 3 may be replaced by a cold anode so that the tube operates on pulsating current. In another modification, the electrodes may be indirectly heated by heaters in series with each other and with a secondary winding. To facilitate starting, the electrodes may be covered with sharp points formed, for example, by an oxide layer. In a further modification, two tubes similar to the tube 1 are operated in parallel, one electrode of each tube being operated from a transformer with its primary in series with the discharge path and the other electrodes being heated from a transformer across the supply. In supplying a tube with one hot electrode and two cold electrodes, the heating current for the hot electrode may be derived from a winding 28, Fig. 4, on the centre limb of a core having on its outer limbs primary windings 26, 27 in series with the discharge. The Specification as open to inspection under Sect. 91 comprises also a circuit in which the primary 44, Fig. 6 (Cancelled), of the heating current transformer is in series with the primary of a transformer 41 supplying the discharge and refers to the application of the invention to other discharge tubes such as rectifiers. This subject-matter does not appear in the Specification as accepted.