GB426138A - Braun tube - Google Patents

Abstract

426,138. Cathode - ray tubes. RADIOAKT.-GES. D. S. LOEWE, 10, Wiesenweg, Steglitz, and SCHLESINGER, K., 39, Friedrichstrasse, Friedrichshagen, both in Berlin. Sept. 29, 1933, Nos. 26800 and 26801. Convention dates, Oct. 1, 1932 and Sept. 8, 1933. [Classes 39 (i) and 40 (iii)] [See also Group XXXVI] Braun tubes for use in television or as oscillographs have two or more cathode rays which are produced by a corresponding number of cathodes, are parallel to the axis of the tube between the cathodes and the deflecting devices, and are predeflected on entry into the deflecting devices so that they produce independent images on different parts of the picture-receiving screen of the tube and cannot be deflected outside these parts. The electrode systems for the separate rays have corresponding parts connected together or structurally united. Two rays may be produced by cathodes 2, 2<1>, Wehnelt cylinders 7, 71, a low-voltage anode 9 with apertures 11, 111 and preferably with concentrating cylinders 10, 10<1> and a high-voltage anode 13 with apertures 19, 19<1>. One plate 20, 201 of the first pair of deflecting plates for each ray is negatively biassed so that the rays are predeflected to scan the separate areas a, b of the screen. The other plates 22, 23 of this first pair are inclined at 20-60‹ to the axis of the tube. The second pair of plates 26, 27 are common to the rays and curved as shown. Current and potential curves of the same operation may thus be produced simultaneously on the areas a, b. In colour television, separate images in basic colours produced on the different parts of the screen are superimposed on a viewing screen by inclined reflectors, the deflecting systems for the different rays being connected to the same oscillation generators. Mutual repulsion of the rays when they are moving slowly before passing the anode 9 is compensated by the attraction of auxiliary electrodes such as one or more knife-edges 33 on the anode 9. Semi-cylinders 32, 32<1> screen the rays from the high-voltage leads 31. The cathodes may each have an indirectly-heated equipotential surface of hollow reflector form with the emissive area at the centre. Wehnelt cylinders may be arranged between the anodes 9, 13 and maintained slightly negative relatively to the anode 9. The predeflection of the ray avoids the " ion-cross " effect in gas-filled tubes and may be produced before entry into the plates 20, 20<1>, 22, 23. A ring-shaped auxiliary electrode at or above the potential of the anode 13 may be placed above the plates 26, 27 and part of the wall of the tube between the auxiliary electrode and the screen may be metallized and made slightly negative with respect to the auxiliary electrode. A coating on the wall of the tube at constant or earth potential prevents disturbances due to the action on one ray of wall charges produced by the other ray. The Specification as open to inspection under Sect. 91 comprises also a modification in which the rays are screened by cylindrical elements below the anode 9. This subjectmatter does not appear in the Specification as accepted.