An apparatus for changing operational plate cylinders during rotary press operation in a rotary press, said rotary press including at least two or more plate cylinders, drive means for driving said plate cylinders and switching means for selectively switching said plate cylinders in a printable state and in an unprintable state, said apparatus comprising:
- input console means available for designating an earlier operational plate cylinder that is switched from the printable state to the unprintable state by said switching means and a later operational plate cylinder that is switched from the unprintable state to the printable state by said switching means among said two or more plate cylinders, setting at least a print count before change of operational plate cylinders, and inputting a print operation command to said rotary press;
- drive control means for performing a normal control for controlling said drive means to rotate said plate cylinder with a match in terms of a reference rotational speed and phase, and performing a special control for controlling said drive means to accelerate said later operational plate cylinder in a halt state up to a rotational speed in coincident with the same rotational speed as that of another plate cylinder normally controlled;
- drive signal output means for providing said drive control means with a normal control signal indicative of executing said normal control and a special control signal indicative of executing said special control;
- print count management means for always checking a print operation speed of said rotary press and an actual print count of a print operation;
- and
- switching signal output means for providing said switching means with a switching signal indicative of switching said earlier operational plate cylinder and a switching signal indicative of switching said later operational plate cylinder, wherein
- said print count management means is configured to compute a print count printed at said print operation speed by said plate cylinder in printing operation under said normal control during a preset time period to specially control said drive means for said later operational plate cylinder;
- said drive signal output means is configured to output said normal control signal indicative of executing said normal control for other plate cylinders than said later operational plate cylinder based on said print operation command, to output said special control signal indicative of executing said special control for said later operational plate cylinder when said actual print count checked at said print count management means reaches a value obtained by subscribing a sum of said computed value and a preset constant from said print count before change of operational plate cylinders set by said input console means, and to output said normal control signal indicative of executing said normal control for said later operational plate cylinder when said later operational plate cylinder has a rotational speed matched to that of said another plate cylinder normally controlled after said later operational plate cylinder is specially controlled for said preset time period;
- and
- said drive signal output means is configured to provide said switching means with said switching signal when said later operational plate cylinder has a rotational phase matched to said reference rotational phase under said normal control and said actual print count checked by said print count management means reaches said print count before change of operational plate cylinders set by said input console means.