GB552622A - Improvements in cathode ray tubes - Google Patents

Abstract

552,622. Cathode-ray tubes. STANDARD TELEPHONES & CABLES, Ltd. Jan. 23, 1942, No. 975. Convention date, Nov. 12, 1940. [Class 39 (i)] In a television tube a wall coating 58 between the electrostatic deflecting system and the fluorescent screen acts as an accelerator and has potential applied through a coaxial cable 58f which passes inside the tube to a lead in the press 15 on which the electron gun is mounted. The cable comprises a wire within a glass sheath 58g with a silver coating thereon ; it occupies a position as shown in Fig. 1 during manufacture and is finally swung until its upper end bears on a silver band 58b forming a terminal for the carbon coating 58. At its lower end the cable has a projecting wire 58j, Fig. 1A, which continues the connection to the press lead. The electron gun comprises the indirectly heated cathode 16, Fig. 11, arranged within the modulating electrode 20, accelerator electrodes 22, 30 at the same potential separated by the focusing electrode 29, diaphragms being arranged within the electrode 30. A plate 61 is welded to the top of the electrode 30 and there is a fixed relation between (i) the distance of this plate from the edge 48 of the deflecting system, (ii) the diameter of the fluorescent screen and (iii) the distance of the screen from the edge 49 of the deflecting system. A further silver coating 59 also acts as an accelerator at the same potential as the electrode 30. Potentials and dimensions of specific examples are given. The plate 61 collects stray electrons ; it has a number of holes in its face, has a mica disc 32 on its underside and is connected by a whisker 61a with the electrode 59. Four ceramic rods 1 but against the mica disc and are secured to the electrode 30 by straps. These rods are also connected by straps to the parts 29, 29a of the focusing electrode, the accelerator 22, the modulator 20 and the cathode 16. Each deflecting plate 33 has two support wires one of which stops at the mica plate 32 but the other passes on down to the press ; with regard to the wires for the deflecting plates 36, one extends down to a lower mica plate 24 and one to a lead in the press the other two stopping at the disc 32. All electric connections to the parts within the tube are brought out through the press. The deflecting plates are attached to the support wires by welding to straps with gaps for the wires to ensure correct spacing ; where these wires pass through the mica disc 32 attaching eyelets 32a, Fig. 4b, are used.