GB495757A - Improvements in or relating to cathode ray tubes - Google Patents

Abstract

495,757. Television; cathode-ray tubes. RADIOAKT.-GES. D. S. LOEWE. Feb. 15, 1937, No. 4454. Convention date, Feb. 19, 1936. [Classes 39 (i) and 40 (iii)] In cathode-ray tubes provided with ferromagnetic plates which serve at once as electrostatic deflection plates and the polepieces of a deflecting electromagnet, as described in Specification 440,560, the windings of the deflecting magnet are so arranged in two portions that the direct current from a relaxation amplifier in one portion opposes that in the other while the oscillation currents pass through only one portion ; a construction of tubes suitable for such operation is also described. Fig. 3 shows a circuit according to the invention. A relaxation oscillation circuit feeds the grid of a pentode 14 the current from which passes through coils 13a exciting the magnetic cores referred to. From the coils 13a the oscillation current leaks off to earth through a condenser 15, the direct current passing through coils 13 opposed to the coils 13a. A resistance 16 prevents disturbances by currents induced by the coils 13a in the coils 13. The coils 13, 13a, are wound on inwardly projecting polepieces 12, Fig. 1, on a sheet metal ring 11 surrounding the tube 7. The flux passes through magnetic filling pieces 8, 9, pressed against the wall of the tube by magnetic springs 70, to sheet-iron deflecting plates 5, 6 formed as a closed surface of the shape shown. Betweenthe deflecting plates 5, 6 and the screen 21 is an accelerating arrangement consisting of a conducting coating 22a, adjacent to the deflecting plates 5, 6 and connected to the anode 3 of the tube, and a coating 22b surrounding the screen 21. The coatings are maintained at different potentials by the circuit 1 shown and connected by a highresistance helix 23 on the surface of the tube.