GB801486A - Improvements in or relating to high-voltage electron guns - Google Patents

Abstract

801,486. Cathode-ray tubes. RANK CINTEL, Ltd. Aug. 10, 1956 [Aug. 10, 1955], No. 23038/55. Class 39(1). In an electron gun structure for use in a cathode ray tube a modulator electrode 2 is held in a predetermined spatial relation to a proximate anode 4 by means of a re-entrant tubular glass member 5 independent of the tube envelope 6 and carrying the modulator anc the anode at its extremities Such an arrangement pro vides a long leakage patl between the modulator cathode assembly and the proximate anode while maintaining these elements in accurate alignment anc spacing and also avoids field emission from conventiona support clips. The anode 4 is electrically connected to a conductive coating 9 on the tube envelope by means o the conductive coating ' and a springy lead 11 whicl urges a contact pad 1( against the coating 9. A beam limiting diaphragn may be introduced into the re-entrant portion 8 of the member 5 and held by peening it into a shallow groove in portion 8. The tubular extension 3 of the modulator electrode may be replaced by a separate guard-ring sealed circumferentially into the tube 5. The tube may be evacuated through the holes 13 in member 5. In an alternative arrangement the modulator cathode assembly is carried on a second reentrant portion of the member 5. The anode 4 and the member 12 which carries the modulator and cathode assembly may be mounted upon separate glass portions of appropriate form which are each machined to concentricity with the electrode carried thereby, the glass portions afterwards being sealed together. These glass portions may be provided with narrow circumferential ribs ground to form lands lying on a cylindrical surface thus reducing the amount of glass machining required.