Control device for cut-off apparatus

A cut off control device for a corrugated fiberboard web, wherein said control device controls a preceding knife driving motor for rotationally driving a preceding knife cylinder on whose peripheral surface a preceding helical knife is provided and also a following knife driving motor for rotationally driving a following knife cylinder on whose peripheral surface a following helical knife is provided, said control device comprising:

• a speed pattern generator, to which a feeding speed of the corrugated fiberboard web and a sheet length to be cut off is input, for generating rotational speed patterns of the preceding knife driving motor and the following knife driving motor based on the input feeding speed and the input sheet length to be cut off and for outputting a speed instruction value;
• a comparator which compares the speed instruction value from said speed pattern generator with a detected speed of the preceding knife driving motor or the following knife driving motor;
• an instruction torque computing unit which computes rotational torque instruction values for the preceding knife driving motor and the following knife driving motor based on a signal from said comparator;
• a cutting torque computing unit which computes cutting torque of the preceding knife driving motor and the following knife driving motor;
• a to-be-given torque pattern generator which distributes the cutting torque sent from said cutting torque computing unit, and generates a to-be-given torque pattern based on the feeding speed of the corrugated fiberboard web and the sheet length to be cut off, and outputs a to-be-given torque instruction value;
• an instruction torque subtractor unit which subtracts the to-be-given torque instruction value, output from said to-be-given torque pattern generator, from the rotational torque instruction value computed by said instruction torque computing unit;
• a preceding power amplifier which controls the preceding knife driving motor based on a computation result obtained by said instruction torque subtractor;
• an instruction torque adder which adds the rotational torque instruction value, computed by said instruction torque computing unit, to the to-be-given torque instruction value computed by said to-be-given torque pattern generator;
• and
• a following power amplifier which controls the following knife driving motor based on a computation result obtained by said instruction torque adder.