Patent GB-799737-A (GB)
Title: Improvements relating to the register control of moving webs
Inventor: CROSFIELD JOHN FOTHERGILL
IPC: B65H23/188
Filed: 1955-04-01
Abstract: 799,737. Automatic registration control systems. CROSFIELD, Ltd., J. F. March 27, 1956 [April 1, 1955], No. 9582/55. Class 38 (4). In a system for automatically controlling the registration of moving webs there is periodic correction in accordance with the magnitude of error and the change of error during a short period prior to correction. In Fig. 1, printed paper web 243 is fed from a reel 240 through rolls 244, 246, 248 to rolls 249 of a folding machine. Further freshly printed webs 250, 252 are also fed to the folding machine through common rolls 248. To maintain correct registration of web 243, marks printed on the web influence a photo-electric head 262 the timing of signals from which is compared in a control unit 264 with the timing of signals from an inductive device 266 operated in synchronism with the folding machine so that any phase displacement operates a servomotor 258 in the appropriate direction to correct registration by adjusting the ratio of gearing 254 between a motor 256 and rolls 246 which control the tension in and longitudinal stretching of the web. In Fig. 2 unit 262 represents the photo-electric head with cathode-follower output which produces signals in response to registration marks and other printed matter on the web. To eliminate the signals due to the printed matter, inductive device 266 operated in synchronism with the folding machine produces pairs of pulses the interval between which is less than that required for the passage of the spaces in which the registration marks are printed. These pairs of pulses are transformed by a flip-flop circuit 274 into gating pulses which render an amplifier 270 operative only during the passage of the spaces so that signals corresponding to registration marks only are applied to a double flip-flop circuit 276 which compares their timing with further signals from inductive device 266 to produce pulses the width of which corresponds to the displacement of the web relative to the folding machine. According to the sense of the displacement one or other of the two channels of flip-flop circuit 276 produces an output which is integrated in a two-channel unit 286 to produce a voltage corresponding to the error. A resistance-capacity timing circuit associated with a flip-flop circuit in a unit 294 periodically initiates the charging of one condenser in a further two-channel unit 292 to a voltage corresponding to the error signal obtained from flip-flop circuit 276 and connects it in series opposition to another condenser charged by the preceding operation of the timing circuit so that voltages are obtained representative of the change of error during successive periods. These change of error voltages and the error voltage from unit 286 are periodically applied by timing circuit 294 to condensers in a control unit 302, these condensers being then connected in parallel to derive difference voltages which, through thermionic valve relays in unit 302 produce corresponding periods of operation of motor 258. Specifications 641,830 and 750,256 are referred to.