GB709103A - Improvements in or relating to gas-filled electric discharge tubes - Google Patents

Abstract

709,103. Cold-cathode tubes. MULLARD RADIO VALVE CO., Ltd. April 9, 1951 [April 13, 1950], No. 9144/50. Class 39(1) In a cold cathode gasfilled trigger tube comprising a cathode 13 in the form of a rectangular plate or alternatively a rod, a trigger 14 in the form of a wire bent into the shape of a stirrup, and a rod anode 15, the anode is surrounded by an auxiliary electrode 16 in the form of a metal sleeve provided with an external electrical connection, and a priming discharge is produced between the sleeve and the anode. The sleeve is so disposed in relation to the cathode as to lengthen the path of the main discharge. The tube comprises. nine pins sealed through a glass base 1 and each surrounded by a glass bead 11. The cathode 13 is supported on three of the pins and the trigger 14 is supported on two of the pins which are provided with sputter shields in the form of a mica disc 19 resting on a glass bead 11 and held in position by an eyelet 20 having a sleeve portion which is clamped on the pin. The sputter shields protect the glass beads 11 surrounding. the trigger supporting pins from metallic deposits during the conventional operation of cleaning the electrodes, when a metallic film is deposited on the inner surface of the tube envelope. The auxiliary electrode 16 rests on the glass bead 11 surrounding the anode 15 and is supported from two of the pins by metal strips 17 and 18 integral with or securely attached to the electrode 16. The electrodes are preferably all made of molybdenum and the auxiliary electrode 16 together with the supporting strips 17 and 18 may be made from a blank cut from a sheet of the metal. The gas filling comprises 99 per cent helium and 1 per cent argon at a pressure of 35 mm. of mercury. A suitable circuit arrangement for use with the tube comprises a resistor connected between the cathode 13 and the auxiliary electrode 16 so that the anode-cathode voltage gives rise to the priming discharge between the anode 15 and the auxiliary electrode 16.