Patent GB-745181-A (GB)
Title: Improvements in or relating to cathode ray tubes
IPC: H01J29/80
Filed: 1953-08-06
Abstract: 745,181. Cathode-ray tubes. CHROMATIC TELEVISION LABORATORIES, Inc. Aug. 6, 1953 [Sept. 2, 1952], No. 21678/53. Class 39 (1). A target structure of a cathode - ray tube comprises a light-transmitting imperforate base-plate 29, Fig. 4, with spacers 55 on one side thereof and wires 51 for holding the base against one face of a rectangular frame 41 on the other side thereof, the wires being strung between opposite frame members but passing over the edges of the base. plate and over the spacers; the spacers are preferably slotted to hold the wires. The target structure comprises translucent baseplate 29 coated with three colour phosphor strips, and spacers 53, 55 cemented to plate 29 by a vitreous cement comprising potassium silicate mixed, if desired, with glass frit. The spacers and plate 29 are of borosilicate glass and the spacers have slots 57 formed by abrasive or photoetching processes to carry grid wires 51. The slots 57 may have graduated spacing to compensate for the differing angles of incidence of the beam. The grid wires 51 serve to focus the beam to a narrow line on a given fluorescent strip. The target structure is mounted in the tube by means of frame 41, Figs. 2, 4, with lugs 43 attached by insulated bolts or rivets 47 to angle-pieces 45 welded to the metal envelope. If the envelope is of glass heavy wire leads are sealed through the envelope and attached directly to 41. Frame 41 is of brass or of the steel alloy having a composition of 18.5 per cent chromium, 0.08 per cent carbon, 0.49 per cent manganese, 0.02 per cent phosphorus, 0.01 per cent sulphur, 0.20 per cent nickel, 0.62 per cent titanium, 0.11 per cent aluminium, 0.29 per cent silicon and the balance iron, and wires 51 of nickel or stainless steel. In manufacture the wire 51 is wound in continuous loops about the target structure, the latter being revolved by a jig, and insulators 61 of glass ribbon or mica sheets or layers having previously been positioned to insulate wires 51 from metal frame 41. Insulating cement 63 is now brushed or daubed on to 51, 41 and the structure baked to set the cement; the portions of the wires between cemented areas 63 are then removed. A conducting bar 65 is provided at each side of the target to contact alternate and intermediate wires 51 respectively, the free wire ends being clipped off short at cemented areas 63; the two sets of wires can thus be used for colour switching. A thin layer of aluminium may be sputtered on to the phosphor strips. After the target structure has been secured to the envelope the viewing end is secured to shell 15. Frame 41 has a thermal expansion coefficient greater than that of wires 51 to prevent sagging of the wires during processing of the tube. In another embodiment, Fig. 7, alternate and intermediate wires are respectively secured to frames 41<SP>1</SP>, 75 by vitreous cement 631, 63<SP>11</SP> with an interposed layer 61<SP>1</SP> of glass ribbon or mica insulation. The edges of plate 291, as well as the spacers 53<SP>1</SP> are slotted to hold the grid wires. Either or both of frames 411, 75 may have lugs similar to 43, Fig. 2, for mounting, and both frames have a higher coefficient of expansion than the wires. In another embodiment,'Fig. 11, alternate and intermediate sets of wires are secured to hooks or posts 42<SP>1</SP>, 76 on strips 42, 75<SP>11</SP> or integral with frames 41<SP>11</SP>, 75<SP>1</SP>. In manufacture the target is oscillated by a jig while the wire is wound about 551, 29<SP>11</SP> and looped over the hooks, each set of wires being a continuous length of wire. Specification 745,180 is referred to.