GB1068904A - Register indicator device - Google Patents

Abstract

1,068,904. Photo-electric registration of multi colour printing. TIMSONS Ltd. June 8, 1964 [March 8, 1963], No. 9424/63. Heading G1A. [Also in Division H3] Register errors between a moving web and a machine performing operations on the web are detected by generating trains of pulses corresponding to the movement of the web and the machine, the frequency of said pulses differing by a small integral factor, prolonging the pulses of the higher frequency train to a repetition interval equal to the interval between the pulses at the lower frequency, prolonging the lower frequency pulses to a duration somewhat less than the repetition interval of the other series of prolonged pulses, and applying the two series of prolonged pulses to gate and amplifier circuits the output of which indicates the phase relationship between the prolonged pulses and hence the register condition of the web and the machine. Photo-cells 10, 10' detect marks on the web and a machine member respectively to produce trains of pulses which are shaped to a standard amplitude regardless of the machine speed by Schmidt trigger circuits. The pulses from photo-cell 10' are at twice the frequency of those from 10 and are fed to a bi-stable multivibrator divide by two circuit, 3, to produce a train of square wave pulses of length equal to the interval between the original pulses. Circuit 3 also includes a monostable multivibrator which resets the divide by two circuit after a predetermined time should a random pulse make it out of step. The pulses from photocell 10 are lengthened by a flip-flop 4 to a length between one and two times the length of pulses from circuit 3. Two outputs of opposite polarity are taken from flip-flop 4 and fed to coincidence gates 5a and 5b. The other input to gates 5a and 5b is the square wave train from circuit 3. Gates 5a and 5b give output pulses of length equal to the overlap of the input pulses, and these outputs after amplification at 5c and 5d are fed to a meter 5e which indicates the difference in mean currents from the gates 5a and 5b which depends on the phase of pulse trains from flip-flop 4 relative to the pulse train from circuit 3. The current difference is indicative in magnitude and sense of the register error between the moving web and the machine, and an output may be taken at x, y for automatic register correction.