Rotary punching device

A rotary punching device for punching a hole in a sheet, said device comprising:

• a first rotary shaft having an outer peripheral surface;
• a punch mounted on the outer peripheral surface of the first rotary shaft, the punch having an elongated body and a cutting end which defines, progressing from a forward-most portion of the cutting end to a rearward-most portion of the cutting end relative to a direction of rotation of the second rotary shaft, a forward planar surface sloped away from the elongated body, an intermediate planar surface having a forward edge coincident with a rearward edge of the forward planar surface, and a rearward planar surface sloped toward the elongated body and having a forward edge coincident with a rear edge of the intermediate planar surface;
• a second rotary shaft arranged in parallel with the first rotary shaft, the second rotary shaft having an outer peripheral surface;
• a die mounted on the outer peripheral surface of the second rotary shaft;
• a motor operatively coupled with the first and second rotary shafts to synchronously drive the first and second rotary shafts in opposite directions such that as the first and second rotary shafts are rotated in opposite directions, the punch and die come into hole-punching engagement with each other through a predetermined rotational angle range;
• a sheet feeding mechanism for feeding the sheet between the first and second rotary shafts at a constant sheet feeding speed while the punch and the die punch the hole in the sheet;
• and
• control means for controlling the rotation speed of the motor referring to the sheet feeding speed, the control means comprising:
• a driving pulse frequency modulation circuit for generating a pulse to the motor, the pulse to vary the speed of the motor satisfying the equation:
• V.sub.1 =-V.sub.2 /cos .theta.,
• where V.sub.1 is a circumferential speed of the punch and die, V.sub.2 is a sheet feeding speed, and .theta. is a rotational angle where the punch and die are engaged, wherein the control means controls the motor such that the linear speed of the punch and die in a sheet feeding direction coincides with the sheet feeding speed through at least a portion of the engagement range between the punch and the die.

A rotary punching device for punching a hole in a sheet, said device comprising:

• a first rotary shaft having an outer peripheral surface;
• a punch mounted on the outer peripheral surface of the first rotary shaft, the punch having an elongated body and a cutting end which defines, progressing from a forward-most edge of the cutting end to a rearward-most edge of the cutting end relative to a direction of rotation of the second rotary shaft, a first portion sloping from the forward-most edge of the cutting end toward the elongated body followed by a convex portion sloping first away from the elongated body, then inverting in slope, and then sloping toward the elongated body and terminating at the rearward-most edge of the cutting end;
• a second rotary shaft arranged in parallel with the first rotary shaft, the second rotary shaft having an outer peripheral surface;
• a die mounted on the outer peripheral surface of the second rotary shaft;
• a motor operatively coupled with the first and second rotary shafts to synchronously drive the first and second rotary shafts in opposite directions such that as the first and second rotary shafts are rotated in opposite directions, the punch and die come into hole-punching engagement with each other through a predetermined rotational angle range;
• a sheet feeding mechanism for feeding the sheet between the first and second rotary shafts at a constant sheet feeding speed while the punch and the die punch the hole in the sheet;
• and
• control means for controlling the rotation speed of the motor referring to the sheet feeding speed, the control means comprising:
• a driving pulse frequency modulation circuit for generating a pulse to the motor, the pulse to vary the speed of the motor satisfying the equation:
• V.sub.1 =-V.sub.2 /cos .theta.,
• where V.sub.1 is a circumferential speed of the punch and die, V.sub.2 is a sheet feeding speed, and .theta. is a rotational angle where the punch and die are engaged, wherein the control means controls the motor such that the linear speed of the punch and die in a sheet feeding direction coincides with the sheet feeding speed through at least a portion of the engagement range between the punch and the die.