GB958709A - Improvements relating to printing - Google Patents

Abstract

958,709. Automatic registration control. EVERSHED & VIGNOLES Ltd. May 9, 1963 [March 14, 1962], No. 9846/62. Heading G3R. In a system for automatically adjusting the register of impressions printed by rolls, a photoelectric cell responding to register marks printed by the rolls controls a gating circuit so that a number of pulses corresponding to the distance between the marks is derived from a generator driven at a speed proportional to that of the printing machine, and passed to a counter which compares them with a desired number and controls the register if there is any error. As shown rolls 2, 3, 4 printing different coloured impressions on a web of paper 1 are driven by an electric motor 6 through differential gears 7, 8, 9. A photoelectric cell 15a responds to register marks printed on the web by rolls 2 and 3 and controls a gating circuit 23 so that pulses from a generator 13 driven by motor 6 are applied to a counter 22 from the time that photo-cell 15e detects a mark made by roll 2 until it detects a corresponding mark made by roll 3. The number of these pulses is thus representative of the relative position of the two marks and if this number differs from a number corresponding to the correct relative position, counter 22 applies a digital error signal to a store 28a. This signal is converted to an analogue signal by stage 31a which determines the speed and direction of a servomotor 12 correcting register by adjusting the speed of roll 3 through differential gear 8. In a similar manner a second photo-electric cell 15b in the same lateral position as photo-cell 15a detects the relative position of marks made by rolls 2 and 4 and controls the register of roll 4 by means of a servomotor 12b. The two detectors and servo-systems are selected in sequence by unit 18 which also clears stores 28a, 28b periodically. Counter 22 resets automatically if the number is unduly high e.g. due to reading the marks in the reverse order. Initial setting of the rolls to approximate register may be effected manually or partially automatically by substituting for the photo-electric detectors, magnetic pick-offs associated with the rolls and appropriately delaying the signals therefrom. The Specification also refers to lateral staggering of photo-cells each of which is associated with and views only marks made by, one roll. Use of a single photo-cell and use of register correcting bars is also possible.