Direct-heated cathode structure

Abstract

There is disclosed a direct-heated cathode structure which comprises an insulating substrate; a pair of conductive supporting rods penetrating the substrate in the direction substantially perpendicular to the surface of the substrate and fixed tightly to the substrate; and a conductive member made of a single metal plate and including a first portion which is arranged in a plane spaced apart from the surface of the substrate by a predetermined distance and substantially parallel to the surface of the substrate and is coated with an electron emissive material, second portions which are extended from the first portion in the above-mentioned parallel plane substantially symmetrically with respect to the first portion, third portions which are extended from the end of extension of each of the second portions in the direction substantially perpendicular to the surface of the substrate toward the substrate, and fourth portions which are extended from the ends of the third portions in the direction substantially parallel to the surface of the substrate in the same plane as the third portions and are fixed to the supporting rods in the neighborhood of the end of extension of the fourth portions. Each of the first, second and third portions has a side wall provided along at least a part of the edges of these portions and extending in the direction substantially perpendicular to the surfaces of these portions.