Patent GB-544601-A (GB)
Title: Improvements in and relating to electric register control systems
IPC: H01J40/14
Filed: 1941-03-14
Abstract: 544,601. Automatic register control systems. BRITISH THOMSON-HOUSTON CO., Ltd. March 14, 1941, No. 3540. Convention date, March 14, 1940. [Class 38 (iv)] [Also in Groups XL and XXXVII]  In systems for controlling correct registration of multi-colour printing rollers 12, 14, Fig. 4, and like devices, two sets of electrical pulses are produced, one by lines 32 marked on the travelling sheet 11  by the rollers 12 and the other by slots in a disc 42 driven by the rollers 14 ; in one of these sets of pulses the terminations are abrupt ; and means are provided to respond in one direction or the other according to the relative amounts of the other pulses occurring before and after the abrupt terminations of the first pulses. As shown, the rollers 12, 14 are driven through suitable gearing by an electric motor 15 the speed of which can be adjusted. A differential gear 17 is inserted in the drive of the rollers 14, and the ring 17a of this gear is driven through a worm 17b by a small direct current motor 18 to correct the registration. The lines 32 marked on the travelling sheet by the roller 12 are say 0.02 inches wide and produce pulses photo-electrically by means of a lamp 28a and a cell 28b ; and the slots in the disc 42 are say “-inch wide and also produce pulses photoelectrically by means of a lamp 40a and a cell 40b. The pulses from the cell 28a are amplified by valves 30, 31, Fig. 1, and passed to the grids 54c, 55c of valves 54, 55. The pulses from the cell 40b are amplified by valve 41 and passed to grid 50c of double valve 50. The corresponding pulse from anode 50a is passed to grid 546 of valve 54. This pulse on the grid 54b is as shown at 62 in Fig. 2. The pulse from the anode 50a is also transmitted to the other grid 50d through a delay circuit 50e, 50f, 50g, and this causes a delayed pulse 64, Fig. 2, to pass from anode 50b to grid 55b of valve 55. The pulses 62, 64 have sharp trailing and leading edges respectively timed to coincide in phase with the trailing edges of the slots in the disc 42. The effect of these pulses on the valves 54, 55 is to prepare them in succession for operation by their respective grids 54c, 55c, which receive the pulses originating from the pulses 32, Fig. 3 produced by the cell 28b. If these pulses 32 are ahead of the trailing edges of the slots in the disc 42, the valve 54 is set in operation ; whereas if the pulses 32 are behind the trailing edges of the slots, the other valve 55 operates. If the pulses 32 are evenly astride the trailing edges of the slots, both valves act equally in quick succession. The pulses thus produced at the anodes 54a, 55a of valves 54, 55 are passed through diodes 26, 29 to integrating circuits including condensers 67, 74 to control the potential of grids 27c, 27d of a double valve 27 and also the potential of the grids of a twin amplifier 76. The output from the anodes 27a, 27b of the double valve 27 serves to control a reversing circuit for the motor 18 ; and the twin amplifier 76 serves to control an indicator 77. The circuit controlling the direct current motor 18 comprises an alternating current source 19 and a pair of gas discharge valves 20, 21 associated with phase shifting networks 23, 25 having direct current saturating windings 23b, 25b connected to the anodes 27a, 27b of double valve 27. When equal currents with balanced pulsations occur in these anode circuits, i.e. when the rollers 12, 14 are in phase, the motor 18 remains stationary but vibrates at the mains frequency thus reducing starting friction and providing sensitive response. When the rollers fall out of phase and the anode currents of double valve 27 become unbalanced, the gas discharge valves 20, 21 also become unbalanced, and the motor 18 is driven in one direction or the other to apply the necessary correction to the motor 14 to restore the phase relationship. The output of the twin-amplifier 76 controls the voltage of a pair of electrodes in the indicator valve 77 which has a pair of indicating sectors in front of the pair of electrodes. When the rollers 12, 14 are in phase, the pulsations on the electrodes are balanced, both sectors are evenly illuminated but a slight characteristic fluttering pattern is observed. When the rollers fall out of phase, one sector only is illuminated and the other is darkened.