GB1034994A - Improvements in or relating to register control systems for moving webs - Google Patents

Abstract

1,034,994. Automatic registration control. BOBST-CHAMPLAIN S.A. March 17, 1965 [March 31,1964], No. 11247/65. Heading G3R. In a control system for a moving web, errors in registration are automatically corrected through a silicon-controlled rectifier between an A.C. supply and a register correcting motor operating intermittently. In Fig 1 (not shown), a web 32, preprinted with a repeating pattern, Is drawn from a reel 34 by rolls 36, 38 and over-printed, cut or otherwise operated on by a rotary member 42 the drive to which is derived from the drive to rolls 36,38 through a variable speed gear 44 and a differential gear 50. To ensure correct registration between rotary member 42 and the pattern on the web a generator 58 driven with rotary member 42 is arranged to produce a pair of adjacent pulses at each revolution and the timing of these is compared with a narrow pulse produced at each repetition of the web pattern by a photo-electric transistorized scanner 56 of adjustable sensitivity and suitable for light or dark background materials. The pulses are produced through Schmitt-trigger circuits and, if registration is correct, the scanner pulse occurs in the interval between the two other pulses. Coincidence of the scanner pulse with one or other of the other pulses is however detected by coincidence circuits and indicates deviation from correct registration in one sense or the other to operate a corresponding one-shot multivibrator and apply a voltage at double mains frequency for a predetermined period to render a corresponding pair of reversely connected silicon-controlled rectifiers conductive to energize a reversible twophase motor 52 so that it runs in the appropriate direction to correct the register by driving the other input to differential gear 50 for the period. A digital counter associated with generator 58 may be preset so that the registration test is made once every one, two, four, eight or sixteen revolutions to allow sufficient time for any correction to be effective and avoid hunting. One further digital counter is preset to select groups of four, five, six or seven consecutive registration tests and others add up the numbers of errors in each sense. If there are four or more consecutive errors in the same sense in any group, indicating an error trend, a motor 90 is operated by a silicon-controlled rectifier arrangement similar to that for motor 52 so that an incremental adjustment of variable speed gear 50 is made to eliminate the trend. In a modification motor 52 adjusts the length of a loop in the web instead of a differential gear to provide the register correction. Application to intermittently fed webs is referred to.