GB399961A - Improvements in and relating to cathode ray tube apparatus - Google Patents

Abstract

399,961. Television etc.; cathoderay tubes. MARCONI'S WIRELESS TELEGRAPH CO., Ltd., Marconi House, Strand, London.-(Assignees of Batchelor, J. C. ; Edgewater Park, New Jersey, U.S.A.) Aug. 15, 1932, No. 22866. Convention date, Aug. 15, 1931. [Classes 39 (i) and 40 (iii).] In a television, picture - telegraph, or like receiver, a cathode-ray tube 1, Fig. 2, is provided with a luminescent screen 5 maintained at a high potential relatively to the cathode 7, coils 33 or plates deflecting the ray to explore the screen 5, and, between the coils 33 and the cathode 7, a ray-focussing and modulating electrode 17 and an apertured accelerating anode 11. The electrode 17 varies the area of the anode 11 on which the ray is focussed and so the intensity of the ray passing through the aperture 13. This modulating action may be supplemented by a control grid 10 varying the number of electrons in the original ray. The electrodes 10, 17 are biassed negatively and positively, and are connected to a resistance or transformer circuit 25 forming a push-pull signal input so that they operate cumulatively. The anode 11 may comprise also a tube 15 with further diaphragms 12, 14. A coating 29 inside the tube 1 is connected to the screen 5. Particular voltages of the electrodes are specified. In a modification, the anode 11 is a single apertured diaphragm extending across the tube 1 and having a tubular extension, and a space-charge electrode or anode is mounted between the electrodes 7, 17, the grid 10 being omitted. In another arrangement, Fig. 3, the electrode 17 is replaced by an electrode 39 at a fixed positive bias focussing the electrons on the aperture 13 and modulation is effected by an electrode 38 robbing a varying number of electrons from the ray. The electrode 38 is so biassed positively that the tube operates on a steep negativelysloped part of the curve connecting the current to the screen 5 with the voltage on the electrode 38. The Specification as open to inspection under Sect. 91 comprises also the replacement of the electrode 17 by a solenoid coaxial with the ray. This subject-matter does not appear in the Specification as accepted.