OBTAINING ALIGNMENT BETWEEN TWO ROTATABLE DRUMS OF A GRAPHIC REPRODUCING APPARATUS

摘要

1478917 Synchronizing graphic reproduction apparatus RUDOLF HELL GmbH 12 Dec 1974 [13 Dec 1973] 53839/74 Heading H2L An apparatus and method for aligning and running in synchronism two synchronous motor driven drums where each motor is supplied from an individual or a common supply through a frequency changer wherein the amount of misalignment is detected by sensing marks on the drums and a bi-directional counter operated accordingly to add or subtract pulses from a clock pulse signal used as a controlling reference supply to one frequency changer. As shown a scanning cylinder 1 is driven by synchronous motor 2 which is supplied from mains 7 through frequency changer 5 at a frequency f 2 dependent on the frequency of clock signal 9. A printing cylinder 3 is similarly driven by synchronous motor 4 supplied from frequency changer 6. The clock signals are derived from a single oscillator 12 in the system shown but separate oscillators could be used. Each drum is provided with respective marks 17, 21 which co-operate with pulse generators 16, 20 to provide pulses to set and reset coincidence circuit 19. The circuit 19 is conditioned to accept a single pulse from the scanning drum generator 16 which causes an up-down counter to have its up terminal connected to line 24 until a pulse is received from the printing drum generator when the down terminal is connected to line 27 through a reducer circuit which is set to produce an output pulse after a given number of input pulses until the counter reaches zero when the two drums should be aligned. The output pulses from the pulse reducer circuit can be used to either suppress (Fig. 2) or add (Fig. 3) pulses to the clock pulse train on terminal 28 depending on whether motor 2 is to be slowed down or speeded up to attain synchronism. In the case where pulses are added to the frequency of clock pulses from terminal 24 to the pulse reducer and counter is halved. A coincidence checking circuit continuously monitors the pulse generator outputs and indicates when the drums are aligned.