Patent ID: 8864133

Claim:
A method for correcting an edge portion of a sheet material, comprising: passing the sheet material through an edge correcting device, wherein the edge correcting device comprises: a first roller provided in a sheet material conveying path; a second roller including a center shaft and side rollers provided at both sides thereof, the center shaft having an outer diameter less than a minimum diameter of the side rollers, each of the side rollers having an outer diameter increasing from a center side to an outer side thereof; and a pressing unit configured to bend the second roller toward the first roller to press the side rollers of the second roller against the first roller, wherein a difference between a maximum radius and a minimum radius of each of the side rollers is less than or equal to a thickness of the sheet material, wherein a difference between a radius of the center shaft and a minimum radius of each of the side rollers is greater than the thickness of the sheet material, and wherein when a sheet material having a length largest in a direction orthogonal to a sheet material conveying direction is sandwiched between the first roller and the second roller, a pressure is applied by the pressing unit in such a manner that an amount of deflection of the center portion of the second roller is less than the thickness of the sheet material.