Control device for cut-off apparatus
Torque necessary for cutting band-like paper is properly distributed to both of the preceding motor and the following motor, thereby making it possible to accurately cut the band-like paper. The cut off method for a cut off apparatus including: a preceding knife cylinder on whose peripheral surface a preceding helical knife is provided; a following knife cylinder on whose peripheral surface a following helical knife, which cuts off band-like paper D in cooperation with the preceding knife, is provided; a preceding knife driving motor which rotationally drives the preceding knife cylinder; a following knife driving motor which rotationally drives the following knife cylinder; and a cut off control device which individually controls the preceding knife driving motor and the following knife driving motor, is characterized in that the method comprises: giving, when the band-like paper D is cut, the preceding knife and the following knife a specified amount of torque in the direction in which the preceding knife and the following knife are pressed against each other, by means of the preceding knife driving motor and the following knife driving motor.
1. 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.
2. A cut off control device as set forth in claim 1 , wherein said cutting torque computed by said cutting torque computing unit has a cutting torque value necessary for cutting off the corrugated fiberboard web, said cutting torque value being based on a basis weight of the corrugated fiberboard web and the input feeding speed.
3. A cut off control device as set forth in claim 1 , wherein said cutting torque computed by said cutting torque computing unit is large enough to resist a cut-off reactive force added from the corrugated fiberboard web to the preceding and following knives, and also to give an appropriate contact force to the preceding and following knives.
4. A cut off control device as set forth in claim 1 , wherein said to-be-given torque pattern generated by said to-be-given torque pattern generator is a pattern having a rectangular shape, a trapezoidal shape, or a polygonal shape.
5. A cut off control device as set forth in claim 1 , wherein said to-be-given torque pattern generator changes the pattern of the to-be-given torque depending on the feeding speed.
6. A cut off control device as set forth in claim 1 , wherein said to-be-given torque pattern generator generates an identical to-be-given torque pattern for the preceding knife driving motor and the following knife driving motor.
7. A cut off control device as set forth in claim 1 , said cut off control device being connected to a production management device including an input unit for inputting thereto a basis weight of the corrugated fiberboard web and the sheet length to be cut off, which production management system (i) outputs the basis weight of the corrugated fiberboard web to said cutting torque computing unit, and (ii) computes the rotation speeds of the preceding and following knife cylinders based on the basis weight of the corrugated fiberboard web and the sheet length to be cut off, and (iii) outputs the resultantly obtained rotation speed to said speed pattern generator.