Patent GB-833724-A (GB)
Title: Electromagnetic printer
IPC: G03G19/00
Filed: 1957-05-13
Abstract: 833,724. Copying telegraphy. NATIONAL CASH REGISTER CO. May 13, 1957 [May 31, 1956], No. 15073/57. Class 40 (3). For converting coded electric data signals, representing in duration and spacing the length and disposition of line segments of an alpha-numeric symbol to be recorded, into a magnetic record of the symbol, a sheet magnetic recording medium is positioned between an electromagnet and a plurality of discrete field concentrators which move sequentially past the electromagnet to produce on the medium a pattern of magnetic line segments corresponding to the data signals and parallel to the direction of movement of the concentrators. The information to be printed is fed from a computer 90, Fig. 2, comprising a programme control circuit 91 and an information register 92 providing signals in a six unit code on outputs L1, L<1>1, L2, L<1>2... L6, L<1>6 from six flip-flops to select an area on the screen 134 of a cathode-ray tube 132. The first three elements of the code passed over conductor 96 control a circuit 136 to generate a voltage controlling the vertical position of a beam 146 on the screen 134 of the cathoderay tube 132. The second three pulses pass to a circuit 131 controlling the horizontal position of the beam and pulses passed to a combination of four outputs B1, B<1>1 ... B4, B<1>4 and converted in the circuit 131 additionally control the beam to produce ten separate, horizontally displaced scanning paths to form a raster 133 on the screen. Adjacent the screen 134 is a mask 135 generally opaque, but provided with openings or translucent portions corresponding to the shape of a letter, numeral or symbol. The light beam varied by the selected area of the mask 135 impinges on a photo-electric device 141 whose output is fed via an amplifying circuit 158 to a circuit 129 controlled to pass the signals to circuits 129a, 129b associated with two magnetizable bars extending across the width of the recording paper 114 which is held stationary during printing, but moved by stepping magnets controlled by a circuit 157 when a line of characters has been printed. The outer surface of the paper is provided with a magnetic coating and the surface of a non- magnetic drum 101 is provided with two turns of helically arranged projections 107 cooperating with the signal bars. Ten projections 107, allocated to each character, correspond to the ten scanning paths, and control or concentrate the magnetization in respect of the signal bars. The output of information from the computer 90 is synchronized with the operation of the printer and of the control circuits of the C.R.T. 132 by pulses derived from clock tracks on the drum associated with pick-up heads 108a, 108b, 108c which operate three circuits 110 to produce pulses Cs, Cc and Cg. To initiate the printing of the information stored in the computer a start pulse S is applied to the circuit 124 which under control of pulses from the clock tracks and from a character counter is effective to operate a circuit 128 to generate a signal R, indicative of the ready condition of the printer, and applied to the programme circuit 91 to initiate operation of the application of the beam-positioning code to the circuits 131, 136. The vertical movement of the beam is controlled by the pulses Cs derived from the head 108a in combination with the first clock track and occurring at approximately the repetition rate of the projections 107. The pulses Cs are also passed to the counter 126 to produce the voltages to produce the ten displaced scanning paths of the raster 133 on the screen 134. The sixty characters forming a line are recorded, thirty by each of the signal bars during two revolutions of the drum 101, the first thirty-five during one revolution, and the remaining twenty-five during the second revolution and the rotational period corresponding to ten characters is utilized for the paper-feed opertion. The various circuits of the printer are under control of the pulses Cc, Cs, Cg provided by the clock tracks on the drum and pulses from the counter circuit 125 in conjunction with appropriate multi-input gates. For each character printed pulses SO ... S59 are generated by the counter 125 and at the end of a line the pulse Sx is produced. The printing circuit 129 is operative only in response to pulses SO ... S59 and is such that the pulse S30 changes over the output of circuit 129 from circuit 129a associated with the first signal bar to circuit 129b associated with the second signal bar. The circuits 131, 136 for providing the horizontal and vertical displacements of the beam 146 comprise, as indicated in Figs. 18, 19 (not shown), a number of flip flop circuits conditioned by the pulses in the lines L1, L<1>1 ... L3, L<1>3, L4, L<1>4 ... L6, L<1>6, B1, B<1>1 ... B4, B<1>4 ... with the respective plate circuits of the vertical and horizontal control arrangements connected in parallel to a circuit having two-fold connection to the two vertical and two horizontal plates respectively of the C.R.T. For the two sets of beampositioning flip-flops, the cathode resistors have values proportional to one, two and four respectively so that the beam can be controlled to have eight selective positions vertically and horizontally to select one of sixty-four areas on the screen 134. The pulses Cs for controlling the vertical traces of the raster are applied to a resistance-capacitor circuit and two connected valves to generate two inversely related sawtooth voltages which are fed in parallel to the anode connections of the flip-flops. The horizontal positioning of the ten traces of the raster is controlled by the four pulses B1, B<1>1 ... B4, B<1>4 applied to four flip-flops operated in combination to generate currents of ten different values, and having their anode circuits connected to the corresponding anode circuits of the flip-flops operated by the positioning pulses L4, L<1>4... L6, L<1>6. Pulses Cs<1> inversely related to the pulses Cs are applied to the C.R.T. 132 to blank the return trace of the beam. Printing arrangement.-The recording sheet 114, Fig. 31, carrying the latent magnetic images is fed via rollers 193, 194, 195 to a chamber 181 in which it is subjected to a low velocity cloud of magnetic particles such as iron oxide, coated with a thermo-setting resin and supplied from a reservoir 198 in conjunction with a blower 200. The return stream passes through a cyclone separator 220 in which the suspended particles return to the reservoir 198. The recording sheet 114 with the magnetic particles concentrated on the magnetized areas is passed in front of a heating arrangement 182 comprising an infra-red lamp 201 so that the resin melts and on cooling forms a permanent bond of the particles to the surface of the sheet. If paper slack occurs, the descent of roller 194 closes a switch 192 effecting energization of a magnetic clutch which connects a feed roller to an electric motor to provide a temporary acceleration of the feed of the sheet 114.