Patent GB-1183590-A (GB)
Title: Apparatus for Displaying and Printing Information
Inventor: BREWSTER ARTHUR EDWARD
IPC: G03G19/00
Filed: 1967-09-28
Abstract: 1,183,590. Selective printing; developing magnetic images. STANDARD TELEPHONES & CABLES Ltd. 28 Sept., 1967, No. 44222/67. Headings B6C and B6F. [Also in Division G5] Electrographic printing apparatus comprises a recording head 3 applying a latent magnetic or electrostatic image to a temporary carrier 1, developing apparatus 5, displaying means for viewing the developed image in positive, and printing means 9 whereby the developed image is wholly transferred to a permanent carrier 10 in positive. The image on the temporary carrier 1 may be in negative and viewed through a mirror 6 as shown or through a translucent temporary carrier (Fig. 36, not shown), or may be in positive and viewed direct, in which case the image is transferred to a second temporary carrier (111), Fig. 29 (not shown), before being printed on the permanent carrier (10). The temporary carrier may be an endless band as shown, a strip (1b Fig. 36) or a drum (1a), Figs. 30, 31 (not shown). A negative image may be obtained with a negative recording charge pattern by locating the recording head on the opposite side of a strip to a recording medium 4, or with a positive recording charge pattern on a recording head adjacent the recording medium on a drum, (Fig. 30) or a strip (Fig. 36). The signal to the recording head may derive from data processing apparatus. Whole character electromagnetic printing.-A magnetic recording head (Figs. 2, 3, not shown) comprises a block of ferrite material bearing a pattern of intersecting slots 19, and having signal windings 20 arranged along the bases of the slots. A plurality of such heads may be arranged in a line across the temporary carrier 1 to print a line of text simultaneously or sequentially, or arranged in a two-dimensional array to print a frame of text simultaneously. Long feeds.-Simultaneous printing of a frame of text enables a preceding frame to be viewed as a whole at the display position. Registration of successive frames in the display position is achieved by providing monitoring heads (not shown) which detect positioning recordings on the edges of the temporary carrier. Character synthesis electromagnetic printing.- Characters may be built up of selectively recorded dots in lines across the temporary carrier, impressed in a recording medium by magnetic fields generated in recording gaps between pole-pieces transversed or arranged across the carrier. A single recording gap (Figs. 10A, 10B, not shown) may be mechanically transversed across the carrier. Alternatively, a line of recording gaps are arranged across the carrier and actuated simultaneously or sequentially. Each recording gap may be formed between opposite ends of a signal winding bent into horseshoe shape (Figs. 5-7, not shown), or between the ends of adjacent windings in a line of windings extending across the carrier, adjacent windings having opposite polarities. The signal windings are set in epoxy resin. In a preferred embodiment, a single recording gap extends across the carrier, and electrical scanning means are provided. In one form, Fig. 11B, the pole pieces 45 defining the gap taper across the carrier, and a coil 41 is connected between the pole pieces. A high frequency A.C. signal of diminishing intensity is applied to the coil 41. Because of the tapering pole pieces, the magnetic reluctance of the pole pieces varies across the carrier, and at any instant, two regions are defined: in one region, the magnetic field generated at the gap is insufficient to saturate the recording medium on the carrier 49, so that no image is recorded, whereas in the other region the field is sufficient to saturate the medium but because of the A.C. input the image recorded is immediately erased. At the junction between the regions, a balance is obtained whereby a signal in a signal winding 48 is sufficient to record an image at that point. Because of the diminishing A.C. signal intensity and the varying magnetic reluctance across the carrier, the junction between the two regions traverses the carrier. In a second form, the gap between the pole pieces varies in width across the carrier. Developing magnetic imagesinking arrangements.-A latent magnetic image recorded on the carrier 1 is developed by applying a magnetic powder such as magnesium-nickel ferrite or nickel-zinc ferrite to the recording surface of the carrier 1 in a powder dispenser 5, Fig. 1. The dispenser comprises a chamber 91, Fig. 26 divided into two by a permeable membrane 92 through which air is blown to fluidize the powder 94 which lies above the membrane 92. The temporary carrier 1 is fed through the fluidized bed of powder and the magnetic images thereon are developed. Excess powder leaking out of the chamber 91 enters a surrounding vacuum chamber 100 and may be recirculated. The developed carrier is fed past the display position to the printing means 9 where the powder developer is transferred to a paper web 10. The powder is fixed to the web 10 by a radio-frequency electrical field or by infra-red or microwave radiation in fixing means 12. The developing powder may include a thermal fixing agent such as polyamide resin or wax, a colouring pigment and an agent to improve the heating properties of the powder such as dielectric material, carbon or metal dust. The temporary carrier preferably has a white, matt silver or reflecting coating to increase the contrast between the powder developer and the carrier surface. Electrostatic printing.-The apparatus as described may be applied to electrostatic printing by suitable choice of a recording head. The developing powder may be barium titanate. Rendering writing visible.-The developed image at 4, Fig. 1, may be illuminated by a lamp 6a and viewed through a window 8 by means of a mirror 6. A negative image may alternatively be viewed through a translucent temporary carrier (Fig. 36, not shown) by back illumination.