GB677884A - Improvements in or relating to electric discharge tubes - Google Patents

Abstract

677,884. Discharge apparatus. STANDARD TELEPHONES & CABLES, Ltd. April 29, 1949 [May 6, .1948], No. 12489/48. Class 39 (i). A cold cathode gas. filled electric discharge tube comprises two electrode assemblies, each comprising two main gap discharge electrodes in the form of metal plates 5 having flat portions riveted to a mica plate 4 and mounted by means of lead-out rods 3 sealed in a glass press 2 and upturned channel section edges forming opposed rectangular discharge surfaces 6. The outer edges of the plates may be bent around the edges of the plate 4 to maintain accurate gap dimensions. A third rod 3 in each assembly protrudes through an aperture in the plate 4 and forms either an anode or a cathode trigger. In the latter case the plate 4 is spaced from the trigger by a distance less than the length of the cathode fall and functions as a field control plate to restrict the cathode glow as described in Specification 677,883, but if the trigger electrode is only to be used as an anode, clearance is not necessary. A sheet 8 of insulating material such as mica, supported by rods 9 prevents ionization coupling between the two assemblies. Gap dimensions are given which are suitable with a filling comprising a mixture containing hydrogen at a partial pressure of 35 mm. of mercury, and neon (with 1 per cent argon) at a partial pressure of 5 mm. of mercury.