GB624004A - Improvements in and relating to cathode ray apparatus - Google Patents

Abstract

624,004. Electric coils. BRITISH THOMSON-HOUSTON CO., Ltd. July 26, 1946, No. 22365. Convention date, July 30, 1945. [Class 35] [Also in Group XL (a)] A combined focusing and centring coil assembly unit 7 for a cathode-ray tube 1 comprises a cylindrical insulating form 27 mounted on the neck 3 of the tube, a pair of centring coils 23, 24 mounted on the form and having axes at 90 degrees to each other and to the axis of the tube, a hollow toroidal core of magnetic material mounted about the centring coils and comprising an inner cylindrical member 28 having an outwardly extending flange 30 engaging an outer cylindrical member 29 having an inwardly extending flange 31 over which the ends of the coils 23, 24 are bent, and a focusing coil 33 arranged in the space between the members 28 and 29. The inner member 28 is shorter than the outer member 29, forming an annular air gap 32. The members 28 and 29 may be locked together by punching in a portion 48 of the member 29 to enter a notch 47 in the member 28. The focusing coil 33 is enclosed in inner and outer insulating sheaths 34 and 35 and is enclosed and sealed in a metallic container 36, the leads 37 for the coil 33 being brought out through sealed connecting posts 38 extending through openings 46 in the flange 30. The centring coils 23 and 24 are located in longitudinal slots 39 milled in the form 27, two of the slots 40 and 41 being widened to provide for the terminal connections to the coils. A layer of insulating material 42 is wound about the coils 23 and 24. The form 27 is provided with outwardly projecting segments 43 forming a ring of stops engaging the end of the cylindrical member 28 and three outwardly projecting segments 44 extending through notches 45 in the cylindrical member 28 to lock the form against rotation. In the arrangement shown in Fig. 2, halves of the centring coils 23 and 24 are arranged at diametrically opposite positions on the neck 3 of the tube 1 and the intensity and direction of the fields produced by the coils 23 and 24 can be adjusted by the potentiometers 25 and 26 respectively. The intensity of the field produced by the focusing coil 21 can be adjusted by the variable resistor 22.