GB419727A - A braun tube for oscillographic and television purposes - Google Patents

Abstract

419,727. Cathode-ray tubes. RADIOAKT.-GES. D. S. LOEWE, 10, Wiesenweg, Steglitz, and SCHLESINGER, K., 39, Friedrichstrasse, Friedrichshagen, both in Berlin. April 18, 1933, No. 11264. Convention date, April 22, 1932. [Class 39 (i).] An aperture 4, Fig. 1, reproduced on the screen of a Braun tube by an electron-optical system is of very small dimensions, of the order of 0.1-1 mm., transversely to the cathode ray, and electrons produced by a cathode 6 having an emissive area much larger than the aperture 4 are concentrated on to the aperture by a curved grid 5 between the cathode and the aperture. The electron-optical system described in Specification 420,667 may be used to focus the aperture 4 on to the screen. The electrodes 5, 6 may be surrounded by a cylinder 2 which may be connected to the grid 5 and to the apertured plate 3. The cathode 6 may be spherically shaped as shown in Fig. 1, or flat, and may be of wire bent as shown in Fig. 5 with the leads 7, 8 brought out close together or crossed so that the field of the heating current is reduced. The cathode may also be indirectly heated or of single or double, flat or conical spiral form. The cathode is oxide-coated or is of oxidized tungsten wire actuated by atomizing light metal, such as barium, in the cylinder 2 by eddy current heating. Alternatively, a wire of light metal may be atomized behind the cathode. The aperture 4 is in the form of a triangle, rectangle, circle, square or rhombus, the image on the screen being correspondingly shaped. The grid 5 is spaced at 1 mm. from the cathode. For oscillography, the grid is biassed positively so that space charge is reduced without ionizing the gas filling and that the grid has the natural potential corresponding to its position. For television, the grid controls the intensity of the ray. The grid potential and the shapes of the electrodes are such that the parts 5, 6 form an electronoptical system with its focus in the aperture 4. The Specification as open to inspection under Sect. 91 comprises also a Braun tube, Fig. 1 (Cancelled), in which the aperture 4 is focused on to the screen 11 by a cylinder 14 and plate 15, an auxiliary electrode 19 being arranged between the deflecting plates 17, 18 and the screen 11. The screen 11 is provided with a metal coating by a wet process or by cathodic atomizaton. A current lead 10 is provided inside the tube for connection of the screen to the anode or as an acceleration anode. The lead 10 may be a thin metal strip produced by allowing a drop of metal solution or lacquer to run along the tube. The tube may be metallized inside or outside, a concentrating electrode on the inside of the tube being shown at 20. To prevent overloading the screen when the spot is moving slowly or is stationary, the intensity of the ray may be varied with the speed of deflection, the potential of the control electrode being varied according to the potential of the deflecting plates by a " double-grid tube." This subject-matter does not appear in the Specification as accepted.