GB729127A - Improvements in or relating to cathode-ray tubes and apparatus embodying cathode-raytubes - Google Patents

Abstract

729,127. Cathode-ray tubes. PHILIPS ELECTRICAL INDUSTRIES, Ltd. Nov. 27, 1951 [Nov. 30, 1950], No. 27779/51. Class 39 (1). In a cathode-ray tube of the kind in which a ribbon beam can be deflected into a plurality of stable positions where it is held by current division between two electrodes 4 and 6, the electrons of the beam after being deflected by plates 2 are brought to a plurality of line foci which lie in the plane of the slotted collector 4 and overlap the edges of the slots therein, by means of two aligned grids 3, 5 which are composed of wires lying parallel to the direction of deflection and which are held at or near cathode potential, and then diverge from the line foci to overlap as indicated so that the portion of the beam which passes through the perforated anode 6 gives substantially uniform illumination on the luminescent screen 9. In Fig. 1, the device has deflection plates 2, grid 3 at zero (cathode) or low potential which collects secondaries from slotted screen 4 and, after screen 4, grid 5 at cathode or low potential whose wires are in the shadow of those of grid 3, both sets of wires extending parallel to the direction of deflection. This is followed by multi-apertured output anode 6 the apertures of which are covered by gauze 7 to allow less than 20 par cent, e.g. 8-10 per cent, of the beam current to pass, post-acceleration anode 8, fluorescent screen 9 and a transparent conductive layer 10 of tin oxide between 9 and the tube wall 11 which is connected by spring or other conductor 13 to 8. A mask 12 of photographically blackened celluloid with transparent numerals or other symbols thereon is attached to the tube wall. Grid 3 splits up the beam into a number of strips which are individually focused to line foci 1 in the vicinity of slotted screen 4 and then diverge so as to overlap, so that the image on the fluorescent screen is uniformly bright and free from shadows. Stray and excessively deflected edge electrons are collected by gauze 7. Postacceleration anode 8, whose slots are in register with those in anode 6, collects secondary electrons from screen 9 which tends to go more positive. If tin oxide layer 10 and the screen 9 are sufficiently conductive, anode 8 may be dispensed with. Dimensions and potentials of an example are given. The slots in anode 6 and in post-acceleration anode 8 may be staggered as described in Specification 669,236. The devices are used for counting pulses. Specification 684,552 [Group XL(c)] also is referred to..