Patent ID: 6907806

Claim:
A sheet processing apparatus comprising: conveying means for conveying a sheet having a side edge extending in a conveying direction of the sheet; driving means for driving said conveying means; sheet processing means for processing the sheet, said sheet processing means being movable in a width direction, which is perpendicular to the conveying direction; first detecting means for detecting the side edge of the sheet, said first detecting means being movable in the width direction together with said sheet processing means; first moving means for moving said sheet processing means and said first detecting means in the width direction; second detecting means provided upstream of said sheet processing means in the conveying direction, for detecting a leading edge of the sheet; third detecting means for detecting a conveying amount by said conveying means in accordance with a signal synchronized with operation of said driving means after said second detecting means detects the leading edge of the sheet; determining means for determining a length of the sheet in the conveying direction; and control means for controlling said first moving means to move said sheet processing means and said first detecting means in predetermined timing and to stop said sheet processing means and said first detecting means from moving in the width direction in response to said first detecting means detecting the side edge of the sheet, wherein said control means controls the predetermined timing in accordance with the conveying amount detected by said third detecting means and the length determined by said determining means so that said first detecting means detects the side edge of the sheet at a vicinity of a sheet processing position of the sheet at which said sheet processing means processes the sheet.