| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a manufacturing method for a duct by which bending of a bent-back portion can be carried out easily in a Pittsburgh lock joint process, and a roll molding machine for the duct used for the lock joint process. <P>SOLUTION: According to the manufacturing method for the duct by which a plate member 10 having an L-shaped joint 12 and a plate member 20 having a U-shaped fitting portion 22 and a bent-back portion 23 are joined together by Pittsburgh lock joint, a recession 24 where the plate member 20 is locally reduced in thickness is formed at a bending position of the bent-back portion 23 of the plate member 20 at least before bending of the bent-back portion 23. This allows the bent-back portion 23 of the plate member 20 to be bent easily at the position of the recession 24. <P>COPYRIGHT: (C)2012,JPO&INPIT |
