Arrangement in printing machines with adjustment means for circumferential, axial and diagonal register

In a printing machine having means for adjusting the circumferential, axial and diagonal register of a plurality of plate cylinders on which printing plates are secured, wherein each plate cylinder is mounted on a shaft for rotation and each printing plate has register markers disposed thereon outside of its respective printing and inking zone, the improvement comprising:

• a register marker detection system comprising at least one illuminating means disposed on one side of each plate for generating and projecting light to illuminate said register markers;
• at least one photo-detecting means disposed on the other side of each plate for periodically detecting said light projecting through the register markers as the cylinder rotates the printing plate and for generating measurement signals in response thereto;
• and circuit means connected to said photo-detecting means for generating signals to control said cylinder register adjustment means;
• said register markers comprising at least first and second accurate-register apertures;
• said illuminating means and said photo-detecting means being positioned such that the light generated by said illuminating means is detected by said photo-detecting means after passing through said apertures;
• and said circuit means being responsive to said measurement signals from said photo-detecting means related to light passing through said apertures.