GB805146A - Improvements in cold cathode discharge tubes - Google Patents

Abstract

805,146. Cold cathode tubes. SIEMENS EDISON SWAN Ltd. June 6, 1957 [June 12, 1956], No. 18123/56]. Class 39(1). A cold-cathode trigger tube comprises a cathode in the form of a perforated disc 1 through which extends a rod 2 forming an anode, the rod being enclosed except for its active end in a glass sleeve 6 upon which, in the neighbourhood of the cathode, is deposited a metal band 9 which constitutes a trigger electrode. The cathode disc 1 is preferably of nickel and has a flange 10 and is coated on the side facing the anode with a layer of activating material and on the underside with a layer of aluminium. A lead 3 supporting the cathode is sealed through a glass-bead 5 and may also be enclosed in a glass sleeve. The anode 2 is connected to a lead 4 and the trigger electrode 9 is connected through a metal film 7 to a lead 8. In addition, a wire 13 may be wound around the sleeve 6 so as to contact the film 7, the ends of the wire being welded to the trigger-lead 8. The band 9 and film 7 may be of aluminium, platinum, graphite or silicon, painted or sprayed in a suspension on to the glass sleeve 6 with the aid of masks, and may be sintered into position before assembly of the discharge tube. A nickel-covered barium wire getter 12 is supported on a lead 11. The glass bead 5 is sealed to a glass envelope and forms a pinch external to the envelope which is evacuated though a tubulation and then filled with a mixture of 94 per cent. neon and 6 per cent. argon at a pressure of about 40 mm. mercury. The tube may contain more than three electrodes. Two or more three-electrode systems may be mounted in a single envelope.