GB1270943A - Improvements relating to deflection coils - Google Patents

Abstract

1,270,943. Electron beam magnetic deflecting systems. EMI Ltd. 20 June, 1969 [28 June, 1968], No. 31168/68. Heading H1D. A deflection coil for a cathode-ray tube is formed by a film of insulating material bearing a pattern of printed conductors, the film being folded and wound to follow the surface of a cone, and the exposed surface of the pattern of conductors being covered by an insulating layer. In the simplest case, a conductive path 2, Fig. 1, is formed around the periphery of the insulating film 1, which is folded along lines 3, 4, 5, and 6 to give the structure of Fig. 2, which is then coiled up, Fig. 3, to give a conical insulating surface with, at diametrically opposed positions on its surface, the coils 7 and 9 superposed and the coils 8 and 10 superposed in such a manner that, in each pair, the magnetic fields reinforce one another. In more elaborate arrangements, instead of a single current path 2, a spiral path, e.g. of 50 turns, may be formed on the film (Fig. 8, not shown), which is of sufficient length, and folded a sufficient number of times, to provide 10 overlying layers, for example, whereby each deflection coil consists of 500 turns. Uniformity of the deflection field may be improved by modifying the shape of the conductive spiral (Figs. 9, 10, 11 and 12, not shown); a cone of any desired angle may be produced by suitably choosing the angle of the folds with respect to the median line of the strip; cones of elliptical or rectangular rather than circular cross-section may be produced; and the spacing between the folds may increase from one end of the strip to the other to allow for the increasing radius of curvature produced by the coiling process. A combined line and field deflection coil system may be produced by forming on the same insulating film suitable conductive patterns together with conductive areas between them to serve as electrostatic shields (Fig. 26, not shown). The insulating film may be of flexible polyester resin 0À001 to 0À002 inch thick, and the conductive patterns may be produced by a printed circuit technique, by etching, or by sticking conductive strip to the film.