Patent GB-674925-A (GB)
Title: Improvements in electronic discharge devices
IPC: G11C11/23
Filed: 1948-02-27
Abstract: 674,925. Cathode-ray tubes. RADIO CORPORATION OF AMERICA. Feb. 27, 1948 [April 26, 1946], No. 6132/48. Class 39 (i). A memory tube for storing information and for giving it up when required without at the same time necessarily destroying the recorded information comprises a cathode, control means, and a target electrode, wherein the control means comprises at least two sets of intersecting wires or strips which define windows for controlling the passage of electrons, the individual wires or strips being out of contact with one another and the arrangement such that each window, independently of the other windows, can be closed to the passage of electrons except when all its framing wires or strips are suitably biased, and means for applying such suitable bias potentials to the wires or strips. The control means may operate by " deflection control," Fig. 1, or by potential barrier control, Fig. 3. In Fig. 1 the cathode 1 is surrounded by individually biased parallel grid wires 3 ... 25; electrons will pass between two positive grid wires but not between two negative ones, or between one positive and one negative if the radial depth of the wires is at least twice their width. Similarly for two sets of wires at right angles, Fig. 2 (not shown), all the four wires bounding an opening must be positive to allow electrons to pass through it. In Fig. 3 the grid wires 43, 45 are smaller or more widely spaced and accelerating grid wires 47, 49 are arranged between the wires 43, 45 and the cathode 41. Hence the " gate " between 43 and 45 is open if for example 43 and 45 are at cathode potential and wires 47, 49 at +100 volts. Here again two sets of control grid wires at right angles are used, Fig. 4 (not shown). The wires 47, 49 are larger than the control grid wires to shield the cathode therefrom. The electrodes may be flat or cylindrical. In one construction, Fig. 5a, a glass envelope 60 has a metal base 62 in which are mounted three concentric rings of terminals 88, 72, 106-108. The cathode 64 is surrounded by a helical first accelerating grid 66, a shield grid or second accelerating grid 68 of parallel wires connected by annular rings 70, vertical control grid wires 58, mounted in mica supports and connected to an equal number of terminals 72 except that the adjacent end wires of the sections are connected together and brought out to a single terminal, horizontal grid wires 74 comprising annular rings mounted by four ceramic rods 78 and spaced by ceramic washers 84, each ring having a tab for connection to a terminal 88, a collector grid 90 of vertical wires or strips connected by annular conductors 92, 94, 96, and a target 98 consisting of aluminium with a secondary emissive dielectric inner surface. The electrodes are all arranged as four segments of a cylinder and the segments may be connected together or used individually to give four tubes in one. The heater, cathode, first and second accelerating grids, collector and target leads are brought out through terminals such as 106, 108. In a further construction, Fig. 6 (not shown), using the " deflection control " grid, the latter is two sets of oppositely wound helical wires the leads to the two sets being brought out at opposite ends of the envelope. The cylindrical secondary emissive target is a sheet of mica with a metal signal plate on its outer surface. It may have a coating of fluorescent material on its inner surface to give a visual indication in which case the signal plate is sufficiently thin to be transparent. In a further construction, Figs. 8, 9 (not shown), a number of control grid networks greater than two is used and the connections are such that only a few leads are required to the exterior of the envelope although a very much larger number of grid wires is used, e.g. 40 leads can control over one million grid apertures; the external leads are grouped in pairs and energized in push-pull. Each individual memory element is identified by two binary numbers one for the horizontal grids and the other for the vertical grids so that individual control is retained over each and every grid aperture. The memory of the device is of the " yes " or " no " type corresponding to the two digit Binary system, i.e. the target areas selected are made to remain at cathode or collector potential. The information may be recorded on the target by (a) closing all the " gates " except one; (b) raising the potential of the signal plate to collector potential, and (c) leaving the gate open or closing it, for a short time, according to whether the target element is to be at collector or cathode potential respectively. The information may be derived by (a) closing all the " gates " except one (b) lowering the potential of the signal plate by a small amount; (c) opening all " gates ". It is shown that if the element of the target is at cathode potential no output is derived but if it is at collector potential a small current pulse is produced in the signal plate circuit. Alternatively information may be stored and derived by varying the cathode potential. In either case the information recorded on the target is not destroyed by deriving it and may be derived as often as desired. The Specification as open to inspection under Sect. 91, states that the memory screen may be replaced by a fluorescent screen. This subject-matter does not appear in the Specification as accepted.