| 20110138980 | PUNCHING UNIT - The invention provides a rotary-type punching unit that solves a problem of a prior art rotary-type punching unit that its punching torque is highly peaked in beginning and ending punching, thus disabling to punch a heavy paper or the like and degrading the quality level of punch holes. A blade surface of a punch of the invention is formed as an inclined surface inclined with respect to the outer peripheral surface of a punch shaft or of a die shaft such that a leading edge thereof is higher than a trailing edge with an inclination angle within a range of 5° to 15° (preferably 10°). A die surface of the die is formed into a surface of a circular arc centering on a rotational axis of the shafts. Thereby, the peaks of the punching torque are reduced and the quality level of the punch hole is kept high. | 06-16-2011 |
