GB469631A - Improvements in gas or vapour-filled electric discharge tubes and in devices comprising such tubes - Google Patents

Abstract

469,631. Discharge apparatus. NAAMLOOZE VENNOOTSCHAP PHILIPS' GLOEILAMPENFABRIEKEN. July 23, 1936. No. 20441. Convention date, Sept. 24, 1935. [Class 39 (i)] [Also in Group XXXVI] A gas- or vapour-filled discharge tube has at least one incandescent electrode heated solely by the discharge, and there is connected in parallel with the discharge path at least one branch circuit comprising a resistance and an auxiliary discharge path which starts from the incandescent electrode, the resistance having such a positive temperature coefficient that during normal operation its value is at least 1À5 times, and preferably two or three times, its value at the ignition of the discharge tube. The low resistance at starting decreases the ignition voltage, while the high resistance in operation reduces the current in the branch circuit and consequent losses and instability. In the sodium lamp shown, a U-shaped discharge tube 1 is supported within an outer evacuated jacket 8 by a spring 11 bearing on an inner sheath 9, as described in Specification 457,266. Discharge-heated incandescent electrodes 3 at each end of the tube are surrounded by auxiliary electrodes 5 each connected to the opposite main electrode through resistances 14 having a positive temperature coefficient. These may be iron wire wound on a mica strip 16 or on enamelled copper rod and placed so as to be heated by the discharge tube. The starting gas is neon at 10 mms. pressure. The resistance may be enclosed in a glass tube and placed within the discharge tube so that its ends constitute the auxiliary electrodes.