GB679348A - Improvements in or relating to cathode ray tubes - Google Patents

Abstract

679,348. Cathode-ray tubes. RAULAND CORPORATION. April 18, 1951 [April 19, 1950], No. 9056/51. Class 39 (i). Cathode - ray receiving apparatus comprises an ion trap consisting of two cylindrical electrodes 18, 21, Fig. 1, offset with respect to one another so the electric field between them has a transverse component to deflect the beam away from the aperture 24 in diaphragm 23, and magnetic deflecting means are provided to deflect the electrons back to the axis of electrode 21, the ions being trapped inside the latter electrode. The magnetic means is preferably a permanently magnetized ring 27 mounted on a tubular member 26 surrounding the tube neck, and a second permanently magnetized ring 28 provides a final centring adjustment of the beam. The magnets have diametrically opposite pole pieces. The tubular member 26 may be rotated or moved longitudinally to vary the strength of the magnetic fields. In an alternative construction, Fig. 2 (not shown), the electrodes as well as being offset with respect to one another are also inclined to the tube axis, e.g. by about 6 degrees, in which case the centring magnet 28 may be dispensed with. The various gun electrodes are supported by lugs 16, 19, 22 from glass rods 13; 14 is a control electrode. The final anode 21 is electrically connected by members 25 to an internal conductive coating and the other gun electrodes by leads 12a to terminal pins 12. Electrode 18 may be dispensed with and electrodes 14, 21 used to set up the electrostatic deflecting field.