GB1417185A - Cathode ray tube construction - Google Patents

Abstract

1417185 Colour television tubes A W STANDAART 17 Nov 1972 [23 Nov 1971 18 July 1972] 53080/72 Heading H1D A multi-beam colour television tube which dispenses with a shadow mask and includes a screen with parallel stripes of the different colour phosphors, has a single gun producing at least three non-crossing electron beams arranged in a substantially vertical plane and maintained spaced from each other throughout their length, the gun including a single sheet cathode having a channel formation projecting towards the screen and defining a vertically elongated emission panel, and parallel, spaced, control grid and first anode elements each having three vertically spaced holes for controlling and shaping the three beams, the holes in the control grid and anode being aligned substantially perpendicularly to the emissive panel, and provided with electrically conductive material to permit the application of selected potentials to the individual holes. As shown for the threebeam gun of Fig. 7, the emissive material of the cathode is coated on one surface 34B, Fig. 6, of a hollow hexagonal tube formed by a pair of channel members, the heater therefor consisting of a pair of windings 35, coated with ceramic, interlocking to provide a maximum temperature at the centre of the cathode area, and oppositely wound to cancel inductive effects. The cathode is mounted in an angled recess in the ceramic slab 36 of the control electrode, which recess is shaped to maintain the emissive surface spaced from its base, in which beam defining apertures 38R, 38B and 38G, each with a separate lead 39, are provided. The first anode 29 is generally similar to the control grid, and may be of identical form, but with the recess facing forwardly. The focus anode 30 is formed by three cylinders 47R, 47B, and 47G each with a corresponding entrance aperture 46R, 46B, and 46G, respectively, giving a lens action. The accelerating anode assembly 31 includes tubes 52R, 52B, and 52G extending rearwardly from, and semicircular members 55 extending forwardly from, an apertured metal disc 51 having a forwardly extending screening cylinder 50, to which getter ring 56 is secured, and which, with the additional nickel screening cylinders 40, 43, 45, and 54 is secured by pins to the support rods 26 to form a unitary assembly which is conductively connected to a conductive coating on the envelope by the spring fingers 57. The three beams are simultaneously scanned, either magnetically or electrostatically, along adjacent triplets of horizontal red, blue, and green phosphor stripes (Fig. 10, not shown), the beams being converged thereon by a pair of adjustably mounted magnets disposed outside the tube envelope above and below the accelerating anode (64a and 64b, Fig. 2, not shown). Many numerical examples of dimensions and voltages are provided.