GB1356697A - Web payout velocity control apparatus for use with a web fed mechanism - Google Patents

Abstract

1356697 Automatic control of web feed HARRIS - INTERTYPE CORP 22 Nov 1971 [7 Dec 1970] 54108/71 Heading G3R In an arrangement for feeding a web to a machine, the motion of a guide roller is automatically controlled to equalize the rate of payout from a web supply with a constant rate of feed to the machine. As shown, a printing press or corrugating machine P includes a mechanism 10 which pulls in web Wat a predetermined rate. The web is supplied from a roll A over a fixed guide roller 20 and a movable roller 22, which is normally in position 22a. When it is required to replace the roll A by a new roll B, a brake 12, 14 is applied to halt the rotation of rollA. As a result, the mechanism 10 pulls the roller 22 towards the machine P, and a chain and sprocket arrangement 24, Fig. 2 (not shown) to which the roller 22 is secured, drives a D.C. tachogenerator 27 and the output shaft of a D. C. motor 26. While the roll A is stationary, splicing is carried out. Subsequently, a relay 50 is energized to actuate a control circuit CC which receives a tachogenerator signal from a roller 56 indicating the actual web speed. This signal is used together with the signal from tachogenerator 27 to compute a continuously varying speed reference signal which is used to retard the motor 26 by dynamic braking so that the roller 22 decelerates at a constant rate under minimum tension until it stops at a predetermined position 22b. The rate of supply of web from the new roll B is now equal to the feed rate to the machine P and normal operation continues, during which the motor 26 returns the roller 22 to position 22a where it is locked until a further splicing operation is required. The control circuit CC, Fig. 4, includes contacts 86, 100 operated by the relay 50, and an integrator 80 which receives the signal from tachogenerator 27 and converts it into a measure of the distance moved by the roller 22 for comparison with a potentiometer 84 setting representing the distance L between positions 22a and 22b. The distance to the position 22b at the time of operation of relay 50 is stored in sample and hold circuitry 88, and combined with the signal from tachogenerator 54 in a multiplier 94, divider 96, integrator 102 and comparator 104 to produce a time-dependent velocity command signal for the motor 26. This is compared with the actual speed signal in a circuit 108 to provide a braking control signal for the motor.