GB402607A - Improvements in or relating to television and like systems - Google Patents

Abstract

402,607. Cathode-ray tubes; television. MARCONI'S WIRELESS TELEGRAPH CO., Ltd., Marconi House, Strand, London.- (Assignees of Batchelor, J. C. ; Edgewater Park, New Jersey, U.S.A.) Jan. 3, 1933, No. 205. Convention date, Jan. 6, 1932. [Classes 39 (i) and 40 (iii).] In a cathode-ray tube of a television receiver &c. in which the picture is reproduced by a ray of electrons scanning a fluorescent screen maintained at a high potential relatively to the electron gun at the other end of the tube, the distance from the screen to the adjacent tip of the gun does not exceed 4 inches and is not less than the largest dimension of the scanned surface, the area of this surface not exceeding 2 sq. ins. The short length of the ray reduces the spreading of the electrons with the result that a picture of good detail and brilliance and of area of, say, 1 sq. in., is obtained and may be projected by a lens system on to a large screen. The tube may be evacuated or filled with argon or other noble gas at a pressure of the order of 2.10<-4> mm. The gas does not focus the ray, but neutralizes space-charges without introducing velocity modulation of the ray. The electron gun is formed by the indirectly heated cathode 22, the electrode 26 and a first anode 32 mounted on the electrode 26 by wires 40 and glass beads 38 and by a recessed, insulating, spacing ring 42. The high-voltage anode comprises a coating 16 on the wall of the tube and extends from the fluorescent screen nearly to the gun. The electrodes 26, 32 include apertured discs 28, 34, 36. A skirt 44 on the electrode 26 extends from the disc 28 nearly to the disc 34 to concentrate electrons passing the disc 28 on to the aperture in the disc 34. Specification 395,499 is referred to.