Patent ID: 7213437

Claim:
A bent-forming method for bent-forming a metal plate into a Z-shaped member, or a hat-channel shaped member, having a horizontal flat portion, an inclined flat portion with one end thereof coupled to one end of the horizontal flat portion via a first bend of not greater than about 90°, and a flange portion coupled to the other end of the inclined flat portion via a second bend of not greater than about 90°, said bent-forming method comprising: a first forming step for bent-forming the metal plate into a provisional formed member having a provisional inclined flat portion with one end thereof coupled to one end of a provisional horizontal flat portion via a provisional bend having an obtuse angle, the other end of the provisional inclined flat portion being coupled to a flange portion in the first forming step via the second bend of not greater than about 90°, wherein the provisional inclined flat portion undergoes deformation so as to form two arch parts thereof having respective protuberances oriented in directions opposite from each other between respective provisional inclined flat forming portions of forming die parts in pairs; and a second forming step for forming the horizontal flat portion, first bend of not greater than about 90° and inclined flat portion so as to be continuously coupled with each other, out of the provisional horizontal flat portion, provisional bend, and provisional inclined flat portion of the provisional formed member, respectively, wherein the provisional horizontal flat portion of the provisional formed member is bent-formed while bending back the provisional bend.