GB421050A - Improvements in or relating to cathode ray tubes - Google Patents

Abstract

421,050. Cathode-ray tubes. RADIOAKT.-GES. D. S. LOEWE, 10, Wiesenweg, Steglitz, and SCHLESINGER, K., 39, Friedrichstrasse, Friedrichshagen, both in Berlin. May 12, 1933, Nos. 13842 and 13843. Convention dates, May 14, 1932 and July 15, 1932. [Class 39 (i)] In a cathode - ray tube of the gas-filled or high-vacuum type and with a cathode, an anode, a fluorescent screen and deflecting devices for scanning the screen, a non-uniform electrostatic field concentrating the electrons between the cathode and the screen is produced by an electrode spaced from the wall of the tube and of semiconductive material with a potential difference applied across its extremities. A semi-conductive coating on the side of an apertured mica disc 1, Fig. 2, facing the anode 7 may be connected at its inner circumference to the preliminary anode 11 and at its outer circumference to a more negative variable potential to produce between the disc 1 and the anode 7 an inwardly directed field of intensity increasing away from the axis of the tube. The coating on the disc 1 may be non-uniform. Metal screens 6, 8 have the same potential as the anode 11. Further concentrating means may be provided. A Wehnelt cylinder 9 may concentrate and control the electrons leaving the cathode 10. In a modification, Fig. 3, the concentrating electrode 15 between the cathode 10 and anode 7 is tubular with apertured end plates and is of diameter decreasing along its axis in the direction of motion of the electrons. A converging accelerating field is produced inside the electrode 15 by applying a potential difference across the semi-conductive material on its surface. The concentrating electrode may be a carbon coating on insulating material or a mass of aluminium or other insulating oxide mixed with carbon.