Cathode ray tube having an improved indirectly heated cathode

摘要

A cathode ray tube includes a phosphor screen and an electron gun. The electron gun includes an indirectly heated cathode structure and plural grid electrodes arranged in axially spaced relationship. The cathode structure includes a base metal having an electron emissive material coating and a heater for heating the base metal. The heater includes a major heating portion having a spirally wound heating wire and a pair of leg portions connected to opposite ends of the major heating portion. The major heating portion and an inner portion of each of the leg portions on a major-heating-portion side thereof are covered with an insulating coating, and the heater is welded to electrical conductors for applying a voltage thereto at an outer portion of each of the leg portions, the outer portion not being covered with the insulating coating. The outer portion of each of the leg portions includes a first multilayer winding portion having heating wires wound spirally in plural layers, and the inner portion of each of the leg portions includes a second multilayer winding portion having heating wires wound spirally in plural layers. The number of turns per unit length in the first multilayer winding portion is smaller than that in the second multilayer winding portion.