Sheet processing apparatus and sheet processing method

A sheet processing apparatus comprising:

• a first detector configured to detect a leading edge of a sheet conveyed in a conveying direction;
• a second detector provided on a downstream side of the first detector in the sheet conveying direction to detect the leading edge of the sheet conveyed;
• a punching portion, in the downstream side of the first detector in the sheet conveying direction, configured to move in a sheet width direction crossing the sheet conveying direction and perform a punching process for the sheet;
• an edge detector configured to move in the width direction together with the punching portion and detect the edge of the sheet in the width direction;
• a third detector provided on an upstream side of the first detector in the sheet conveying direction to detect the leading edge of the sheet conveyed;
• and
• a controller selecting the detector positioned on the most downstream side in the conveying direction among the first, second, and third detectors that meet the following formula:
• X
• +
• L
• V
• >
• X
• 1
• V
• 1
• where
• V:
• conveying speed of the sheet [m/s],
• L:
• sheet length in the conveying direction [m],
• X:
• distance from a standard judgment position (the upstream side of the standard judgment position in the conveying direction is positive and the downstream side of the standard judgment position is negative)[m],
• X1:
• distance after the edge detector starts movement until the edge detector detects the sheet edge [m], and
• V1:
• moving speed of the edge detector [m], and
• permitting the edge detector to start movement to detect the edge of the sheet in the width direction when the selected first, second, and third detectors detects the leading edge of the sheet conveyed.

A processing method of a sheet processing apparatus including a first detector configured to detect a leading edge of a sheet conveyed in a conveying direction, a second detector provided on a downstream side of the first detector in the sheet conveying direction to detect the leading edge of the sheet conveyed, a third detector provided on an upstream side of the first detector in the sheet conveying direction to detect the leading edge of the sheet conveyed, a punching portion, on the downstream side of the first detector in the sheet conveying direction, configured to move in a sheet width direction crossing the sheet conveying direction and perform a punching process for the sheet, and an edge detector configured to move in the width direction together with the punching portion and detect the edge of the sheet in the width direction, comprising:

• judging that the edge detector can detect the edge of the sheet on the basis of at least one of information of a conveying speed of the sheet and a sheet length in the conveying direction, when the edge detector starts movement in the width direction after one of the first, second, and third detectors detects the leading edge of the sheet;
• selecting among the first, second, and third detectors, the detector positioned on the most downstream side in the conveying direction on the basis of a result of the judging;
• and
• permitting the edge detector to start movement and to detect the edge of the sheet when the selected one of the first, second, and third detectors detects the leading edge of the sheet conveyed.