Patent GB-797527-A (GB)
Title: Improvements relating to the register control of moving webs
Inventor: CROSFIELD JOHN FOTHERGILL
IPC: B65H21/02
Filed: 1955-03-16
Abstract: 797,527. Automatic registration control systems. CROSFIELD, Ltd., J. F. March 13, 1956 [March 16, 1955; July 22, 1955], Nos. 7708/55 and 21291/55. Class 38 (4). [Also in Groups XL (b) and XL (c)] Apparatus for automatically sticking a moving web of preprinted paper to a rotating reel of preprinted paper is so controlled in accordance with a register error as to reduce it, mechanism sticking the web to the reel when the error is a predetermined small value, the register error being the interval between electrical impulses generated corresponding to the passage of integral numbers of preprinted units on the web and on the reel. General arrangement.-(see Figs. 1, 2). The embodiment described in the Specification includes a new reel 11 whose periphery equals two preprinted units and carrying a single mark 21, and web 4 carrying marks 19 in its margin. Co-operating photo-cell assemblies 20, 18 produce corresponding series of electrical pulses, and those assemblies are so placed that when the pulses coincide the preprinted units on the web and the reel are in register. Control unit 22 feeds a signal derived from the interval between the corresponding pulses in the two trains to correction motor 23 connected to differential gear 13, so that the reel speed is automatically adjusted to reduce register error; motor 23 contributes only a small proportion to the total speed. When the error is reduced to a predetermined small value control unit 22 energizes brush and knife coils 24, 29 for the sticking of the web to the reel and subsequent cutting of the web. Resolver 36 provides an A.C. voltage whose amplitude represents tension error, correct tension leading to zero resolver output. At times other than when a new reel is to be pasted to the old web, this output is used to control the speed of motor 23 for maintaining correct tension in web 4, the motor rotation being made to add to reel speed; when the system changes to register control it must run at maximum speed in reverse to achieve maximum correction, the error being reduced by this rate until it is below a critical value after which correction rate is proportional to error, the motor speed reducing to zero and then increasing in the original direction so that it approaches its original speed as the error approaches zero. The pasting operation then begins and the system changes over to tension control without a jerk on the web. Panel 17 carries two push-buttons (see below). The Specification mentions other methods of producing the trains of impulses, one including the use of magnetic switches. Electrical circuits.-(see Figs. 3, 8). Trigger circuit 41 generates a pulse whose length equals the time interval between a pulse from amplifier 40 and the next pulse from amplifier 39, units 37, 38 being the photo-cell heads. To convert this time interval to a corresponding length and to allow for the eventual error correction achieved being inversely proportional to the frequency of the pulses a D.C. tachometergenerator 59 is driven at the speed of rollers 7 and its output is fed to squaring and integrating circuit 60 in addition to a trigger circuit 41 'output. Circuit 60 feeds via relay contact C1 a stage 61 whose output, in series with the output of D.C. tacho-generator 93 coupled to motor 23 produces in association with modulator 88 an A.C. voltage, amplified by stage 89, to a winding of the two-phase correction motor whose other winding is connected to A.C. of constant amplitude and quadrature phase. C Relay - is operated by negative pulses from 2 trigger circuit 41 via rectifying and differentiating circuit 95 and relay-operating circuit 96. The positive pulses from circuit 41 make relay D -, initiating operation of the cutting and 3 pasting mechanism via differentiating and rectifying circuit 104 and trigger circuit 105, the relay resetting itself shortly after it operates. When motor 23 is not in use for registration it can be used for controlling web tension by signals derived from tension resolver 36 via amplifier 115 whose gain is varied as a function of the speed of rollers 7 by tachogenerator 59, rectifier 116, closed contact A2, storage capacitor 117 and cathode follower 62. Panel 17 (see Fig. 1), includes push-buttons PB1 and PB2 (see Fig. 8). Button PB1 is pressed when the arms of the reelstand are rotated to bring a fresh reel into the uppermost position and the system is to be changed over to A register control, thus operating relay - and 2 contact A2 (see Fig. 3), disconnects the tension resolver circuit. Button PB2 is pressed when the new reel is in its correct position, ener- B gizing relay - to prepare circuit 61 (see Fig 3) 2 to respond to registration error correction signals.