Patent GB-735050-A (GB)
Abstract: 735,050. Automatic registration control 'systems. WIGGINS, TEAPE, & CO. (1919), Ltd. Aug. 10, 1953 [Aug. 5, 1952; Dec. 4, 1952], Nos. 19733/52 and 30833/52. Class 38 (4). [Also in Groups XXXVIII; XL (b) and XL (c)] Pulses derived photo-electrically from marks on a paper web are used to maintain registration in a cutting, folding or printing-machine. Pulse deriving circuit, Fig. 1.-Pulses detected by the photo-cell and amplified by V2 are fed to a further amplifier V3 (through a high-pass filter C2, T1, C3 which removes 100 c/s. background due to A.C. lamp energization). The amplified pulses from V3 are fed through transformer T2 to a full-wave rectifier so that the apparatus will be responsive to either increase or decrease in light; (an adjustable back bias is applied to the diode from potentiometer P3 to remove background noise). The. output from the diode is fed through a cathode follower V5 to a thyratron V7 which is fired by a pulse to discharge a capacitor C14 which provides a predetermined pulse through the rotor windings AT of a Selsyn transmitter, which for indicating purposes is connected in series with the receiver rotor AR, Fig. 3 (not shown). The capacitor is recharged to H.T. positive supply valve from the A.C. supply through a series valve V9 having its grid connected to the H.T. supply line. The cathode follower V5 is incidentally connected in a "boot-strap" circuit to provide the necessary delay for the thyratron to warm up initially before relay RELW operates to complete the thyratron anode circuit. Circuit checking indicators.-(i) A meter M in the anode circuit of V2 indicates a steady mean brightness valve. (ii) A "magic eye" V6 connected to the cathode follower V5 indicates the arrival of pulses and by fluttering, the presence of unwanted background. (iii) A mean lamp connected across the thyratron V7 may be used for remote indication that the apparatus is working. Control circuit, Fig. 2.-For automatic control purposes, pulses are passed through only the Selsyn transmitter rotor AT, which is driven by the, e.g., cutting-machine, and the receiver rotor AR is coupled to a transformer T7, Fig. 2, whereby pulses varying in magnitude and phase sense with the error are supplied to cathode follower V53 or V54 to apply a negative charge to capacitor C41 or C42 through diode V55 or V56. (Circuits 103, 104 serve to suppress the negative "tails" which may accompany positive pulses.) A negative charge applied to capacitor C41 or C42 results in a positive pulse at the anode of amplifier V57, V58, which fires thyratrons V59 or V60 to energize the fields of a reversible-correction-servomotor (not shown). The thyratrons V59, V60 are extinguished by a timing circuit, V61 ... V66 (see Group XL (c)), after a time dependent on the magnitude of the error signal. While the error is increasing, each error signal-pulse will be of greater magnitude than the last, causing a further small negative charge to be applied to capacitor C41 or C42 and consequent firing of the thyratrons V59 or V60 which will burn for progressively shorter times. When the error is steady or decreasing, no further charge will be applied to the capacitor and the correction servomotor is not energized. Relays W3, W4 connected in series with the field F11, F12, operate contacts RC3, RC4 to short the capacitor C42, C41 in the opposite circuit whenever V59 or V60 fires so that when the error signal changes sense the capacitor associated with that sense will be fully discharged. Instead of applying the derived pulses to the control circuit, they may be applied to a Selsyn. indicator system. In an alternative control system, Fig. 2 (Prov.) 19733/52, the correcting motor runs for a predetermined number of revolutions each time a correction is initiated, irrespective of the magnitude of the error. Pulses varying in phase sense and magnitude with the displacement error are applied to valves V17 to trigger thyratron V19, or V20 which, when one fires, applies a positive bias from the common cathode resistor R31 to valves V18 (normally biased to cut-off through resistor R32); the valves V18 then conduct and prevent further positive trigger pulses being developed by either.valve V17 while one of the thyratrons is burning. Firing of thyratron V19 or V20 energizes field F1 or F2 of a reversible correction-servomotor which, once each revolution, closes a contact CB in the grid circuit of V24 to charge a small capacitor C27 connected in a " cup and bucket " circuit with capacitors C25, C26. After a certain number of revolutions, C25 acquires such a charge that cathode follower V23 conducts sufficiently to cause " suppressor " thyratron V22 to fire and extinguish thyratron V19. or V20 by means of the anode circuit coupling. Backlash, compensation, Fig 2 (Prov.) 19733/52. When the motor is running light, before taking up the drive, a high voltage across the armature and operates relay 2RELW to apply a blocking bias to the second grid of V23. This is stated to stop the operation of the counting circuit. Alarm circuit.-When the error reaches a certain magnitude thyratron V21 (connected to potentiometers P4 in the grid circuit of V19, V20) is fired to operate alarm relay 3RELW.