GB406009A - Improvements in braun tubes, more particularly for television purposes - Google Patents

Abstract

406,009. Cathode - ray tubes. FERNSEH AKT.-GES., Goorzallee, Zehlendorf, Berlin. July 13, 1932, No. 19856. Convention date, July 31, 1931. [Class 39 (i).] Braun tubes with hot cathodes acting as image-producing devices in television &c. are provided with metal electrodes applied to the glass wall of the tube and interengaging thereon without mutual overlap, part of these electrodes being electrically connected to the fluorescent screen. The electrodes may be metal coatings 6, 7 chemically deposited on the wall, separated by a zig-zag gap as shown, and connected respectively to the fluorescent screen 4 and the anode 1. The potential gradient of the electric field along the tube is thus made constant and all points corresponding to possible deflections of the ray are kept at the same potential in the same transverse cross-section. The coatings may be replaced by wire apices. The Specification as open to inspection under Sect. 91 comprises also circular-ring electrodes spaced apart and at successively increasing potentials to produce the increasing potential along the tube, also arrangements of rayfocussing devices and electrodes. The electrons may be variably focused electrostatically or electromagnetically on to a diaphragm to control the number of electrons passing through a small aperture therein, and so to modulate the intensity of the ray according to the picture intensity, the ray being then brought to a sharp point on the fluorescent screen by focusing the aperture on to the screen electrostatically or electromagnetically. Electrons from a hot cathode 1, Fig. 1 (Cancelled), are variably focussed on to the positive apertured diaphragm 3 by a Wehnelt cylinder 2 positive or negative with respect to the cathode 1, the diaphragm 3 being very close to the cathode 1 or at a distance. The cylinder 2 may have lateral apertures or be of gauge to equalize gas pressure inside and outside. The electrons issuing from the diaphragm 3 are concentrated by a cylinder 5 negative with respect to the diaphragm 3 or by an electromagnetic coil. When a highvoltage anode 6 connected to the fluorescent screen is used, the focussing coil surrounds this anode 6 and the distances of this anode 6 from the diaphragm 3 and from the fluorescent screen 9 are in the ratio 1 : 2. If the anode 6 is omitted, the coil is midway between the diaphragm and the screen. A thin metal coating is provided between the fluorescent screen and the glass wall or on top of the screen. The production of varying intensities in the light spot on the screen by modulating the velocity of the ray, the deflecting potentials being correspondingly modulated, is also referred to. This subject-matter does not appear in the Specification as accepted.