GB443730A - Improvements in or relating to cathode ray tubes suitable for use for television and similar oscillograph purposes - Google Patents

Abstract

443,730. Cathode-ray tubes. MARCONI'S WIRELESS TELEGRAPH CO., Ltd., Electra House, Victoria Embankment, and YOUNG, A. J., 61, Galveston Road, Putney, both in London. Aug. 30, 1934, No. 25023. [Class 39 (i)] The cathode 1 of a tube for television &c. is held accurately in position by passing through an aperture in a transverse in sulator disc or shee 3 which is screened by an aperture( focusing electrode 6 surrounding the cath ode 1 at a point between the disc 3 and the electron emissive area of the cathode. As shown, the electrode 6 is mounted on a mica disc 9 in a groove in the Wehnelt cylinder 7, and the dished anode 8, and disc 3 of mica or steatite are carried by rods 4. The electrode 6 may be positively or negatively biassed but is preferably connected directly to the cathode inside the tube. The cylinder 7 may be positively or negatively biassed and a lowpressure gas filling may be used. Ratios of the distance a of the cathode within the cylinder 7 to the diameter b of the cylinder are specified and the distance a may be as high as ¥b. In a modification, the disc 9 is omitted and the electrode 6 is on the disc 3 ; the cylinder 7 may be omitted and several disc anodes provided. In another modification using a filament instead of the indirectly heated cathode 1, the filament is centred by the disc 9 and not by the disc 3. In a further modification suitable for a hard tube, Fig. 3 (not shown), an electron gun structure of specified dimensions is supported by additional insulator discs from the rods 4. Specification 435,566 is referred to.