Offset printing machine, printing plate and image position reading-out method for offset printing machine

A printing machine is disclosed in which a sleeve having a tapered side surface is provided movably in an axial direction to a gripper shaft 5 arranged in parallel to a plate cylinder shaft 2. A sleeve member 25 is provided movably in the axial direction of the plate cylinder shaft 2. The sleeve member 25 is connected to the sleeve by a swingable arm. A screw 18 which is brought into contact with the tapered side surface of the sleeve is fixed to a bracket 16 mounted on the gripper shaft 5. Furthermore, a plate 13, a gripper 10 and a front abutment are provided on the gripper shaft 5, the front abutment being moved. An amount of displacement of an image position on the printing plate relative to a regular or normal position is obtained by intersecting two lines 47b and 47c formed at the clamp end portion. Since the method is related to a method of drawing two lines 47b and 47c having any width, it is possible to eliminate an error generated due to a configuration error of a register mark and it is possible to detect the image position width high precision. Accordingly, when the printing plate is automatically fed to the plate cylinder of an offset printing machine, it is possible to feed the printing plate with the image on the printing plate being parallel to the plate cylinder.