GB871195A - Improvements in or relating to electrostatic printing tubes - Google Patents

Abstract

871,195. Cathode-ray tubes. DICK CO., A. B. May 13, 1958 [May 13, 1957], No. 15345/58. Class 39(1). In an electrostatic printing tube of the kind comprising electron-beam generating means and a target formed by an array of wires insulated from one -another, a portion of each wire being within the tube envelope whilst one end of each wire extends to the exterior of the envelope, these ends forming an array of spaced wire points, each adjacent pair of wire in the target array is interspersed by a shield electrode, the shield electrodes being adapted, when connected to a suitable source of potential, electrostatically to shield the wires from one another. As shown, alternate ones of wires 32, Fig. 1, constitute the shield electrodes and are connected by means of lead 38 to a suitable potential whereby discharges take place to the external anode 36 in preference to an adjacent shielding wire. Thus each wire may be altered electrically by the electron beam without an appreciable effect on its neighbours. Each wire may be clamped between glass rods 40, 42, 46, 48, Fig. 3, with one end 33 extending to the flat printing surface 44. Alternate wires 38 are connected to lead 38 by means of printed-circuit conductors 52 on insulating member 50. The glass rods are mounted in a slot in metal plate 30. An alternative form of target may be made by winding a shield wire 64, Fig. 5, around glass rod 60 and conducting strip 62, winding writing wire 68 around rod 60, strip 62 and glass strip 66 so that its turns fall between the turns of the shield wire and grinding away the wires at two sides. This assembly is sealed to a glass rod 70 and mounted in the metal faceplate 30. Since the shield wires 64 are bent away from the writing tips 68 the chances of discharge to the shield wire instead of through the dielectric medium 34 to the external anode 36 are reduced. Specification 871,194 is referred to.