Patent GB-853477-A (GB)
Title: Improvements in or relating to a device comprising a cathode ray picture display tube and a gate tube
IPC: H04N9/26
Filed: 1956-12-20
Abstract: 853,477. Television. PHILIPS ELECTRICAL INDUSTRIES Ltd. Dec. 20, 1956 [Dec, 23, 1955], No. 38836/56. Class 40(3). [Also in Group XL(a)] A colour television receiver arrangement comprises a picture display tube 15, Fig. 1, having a single electron gun 14 and two interleaved. colour switching grids 17 and a gating electric discharge tube having means for generating a plurality of electron beams, a plurality of intensity control electrodes 5 energized by respective input signals, deflector plates 7, 8 for deflecting all the beams, the plates 7, 8 and colour switching grids being fed in operation with synchronous alternating potentials from source 19, the gate tube having anode surfaces 9, 10, 11 for the respective beams which are staggered so they are struck at different times in the deflection sweep and connected to a common output circuit feeding the intensity control electrode of the picture display tube. Output electrodes 9, 10, 11, Fig. 1, are arranged along a diagonal of and in front of collector 12 so as to be struck by one of the three beams respectively, at successive moments in time, and are connected to a common output circuit feeding the video grid of single gun colour receiver 15 which has a conventional focusing and colour switching grid adjacent to the screen. The grid 17, 18 is energized by A.C. from circuit 19 to give colour control deflections as the beam scans each line of the colour receiver screen, and the A.C. from 19 is also applied to deflecting plates 7, 8 of the gating tube to synchronize the operation of the two tubes. The frequency of repetition of the green signal portions is twice that of the red and blue since the green target 10 is struck twice as often by the beam. The line scan may be along the colour lines or perpendicular to them and the sequence of colour lines in the latter case can be RGBG, RGBG, but since the beam in the gating tube passes twice as often over the green target as over the red and blue targets the double green frequency is supplied directly to the picture display tube. To make the grids of Fig. 1, wire can be wound on metallized areas of two ceramic rods 37, Fig. 5, and soldered to the metallized parts thereof. A few turns 35, 36 are now removed leaving three mutually insulated grids. The grid wires may be entirely removed at one side or the wires at one side pressed into the plane of the other side. In Fig. 6, the cathode 38 is surrounded by a metal cylinder 39 closed at one end by a ceramic disc 40 having three apertures, the apertures being surrounded by metallized areas 41, 42, 43 on the ceramic serving as separate control electrodes. After deflection by plates 47, 48 the beams pass at different parts of the deflection cycle, through apertures 49, 50, 51 in electrodes 53, 54, 55 and strike common collector 52. In modifications, the cathode may have three separate emissive areas, auxiliary screen or suppressor grids may be provided between the deflecting electrodes and collecting electrode system, and the beams can be separated by screens. In a further modification, Fig. 3 (not shown), the beams may be deflected over an apertured anode, the anode apertures being staggered as in Fig. 3 to fall on a collector behind it and in a further form, Fig. 4 (not shown), also having staggered apertures there are two beams emitted from opposite sides of a common cathode. A prior art colour receiver with a single gun wherein the screen lines are R-G-B-G-R-G- is referred to the colour switching being effected by two sets of grid wires lying in a single plane adjacent to the screen. Since there are twice as many green lines as red or blue, the green gate must be controlled at twice the frequency of the red and blue gates.