To detect the presence or absence of a staple needle in an inexpensive and simple constitution.
An upper gripping plate 204 holds resistors 220, 221 whose resistance values are respectively proportional to the lengths, and the resistors 220, 221 are extended in the width direction of a sheet P. A lower gripping plate 202 holds conductors 222, 223, and the conductors 222, 223 are extended parallel to the resistors 220, 221 and disposed opposite to the resistors 220, 221. The respective both ends of the resistors 220, 221 are put in the connecting state between a voltage V and a ground (GND), and given a potential difference of the voltage V. A sheet bundle Pt stitched at the trailing end part is transported, and the trailing end part is gripped by a needle detection sensor unit 201, so that the trailing end part of the sheet bundle Pt is nipped between the resistors 220, 221 and the conductors 222, 223. In that state, the presence or absence of a staple needle h is determined on the basis of the potentials (voltage V1, V2) of the conductors 222, 223.
KATO HITOSHI
ISHIKAWA NAOKI
SATO TOMOHARU
