Patent GB-666854-A (GB)
Title: Improvements in or relating to cathode ray tubes
IPC: H01J29/46
Filed: 1948-02-19
Abstract: 666,854. Cathode-ray tubes. MARCONI'S WIRELESS TELEGRAPH CO., Ltd. Feb. 19, 1948 [Feb. 19, 1947], No. 4966/48. Class 39 (i). In a television pick-up tube having a low velocity scanning beam and external electromagnetic focusing and deflecting means, parts of the tube outside the deflecting area are screened therefrom by a low - reluctance ferromagnetic path for the fringe flux from the deflecting means. The deflecting coils 43, 60, Fig. 1, for an image orthicon are mounted through electrostatic screens and fish paper wrappings on an insulating cylinder 40, the leads theretor passing through holes in a cylindrical shell 65 to a terminal strip 67. The ends of the screens are clamped between members 45, 46, 49, 50. An alignment coil 70 is housed between copper cylinders 71, 72 closed by copper rings and the leads therefor are connected to terminals 74. Focusing coils 15, 16, 17, separately energized, are mounted on an insulating cylinder 10 through a wound electrostatic screen 13, clamped at its ends by members 11, 12, and are separated by insulating rings 18, 19, 21. The coils are covered with alternate layers of steel screens 27, separated by waxed twine, and fish paper and a final layer of acetate cloth. A further focusing coil 83 is housed between flanges 81, 82 on the cylinder 80 which is fitted within the cylinder 10 and fastened to the deflecting arrangement. A ring 84 of magnetic material is arranged within the end of the cylinder 80 so that it is coplanar with the mamber 20, which is of similar magnetic material, and, with a further ring 95, of magnetic metal, forms a path for the fringe flux of the deflecting coils. The low-velocity beam in the enlarged section of the tube which contains the target is screened thereby. Tube contact pins may engage with sockets on a holder 92, mounted within an insulating cylinder 90, a flange 91 on which carries terminals 94 which are connected to the holder 92 by copper strips 93. The coil assembly may be secured between aluminium end-plates (Fig. 2, not shown) to one, 111, Fig. 3, of which is bolted brackets 116, 117 carrying gear-wheels 121, 122 for rotating the deflecting, focusing and alignment coils. The tube neck is secured through a bronze spring winding 125 and by a set-screw within a rotatable yoke 118. In a modification, Fig. 4 (not shown), the ring 84, Fig. 1, is pinned to two other rings of magnetic material, one of which surrounds the inner end of the enlarged tube section containing the target. The housing for the focusing coils may consist of an iron cylinder instead of the steel strips. In a further form, that end of the coil assembly which surrounds the tube section containing the multiplier 150 Fig. 6, is fitted with coplanar rings 142, 143 of magnetic material arranged between insulating rings 140, 141, 144, 145. The extension of the cylinder 80, Fig. 1, supporting the focusing coil 83, may be cut away to leave two intermediate strips, Fig. 7 (not shown), which support the end ring 85, or alternatively, may be cut to provide a number of longitudinal strips 156, Fig. 8, the free ends of which are secured to an insulating ring 160 and is riveted to the end ring 151. The free ends of the strips may extend in opposite directions.