| 摘要 |
PROBLEM TO BE SOLVED: To provide a corner-piece-less duct having a rational construction, which can significantly reduce the number of parts by effectively utilizing scraps conventionally discarded. SOLUTION: In this corner-piece-less duct, plate-like members are joined to each other at side end portions by a seam joint to form a duct 10 having a tubular and cross-sectionally rectangular shape as a whole; a starting end portion and a terminal end portion of the plate-like members are bent in a direction substantially perpendicular to a longitudinal direction Za of the plate-like members to form flange forming portions 3 integrally with the plate-like members; and corner forming portions 4 are formed integrally to protrude from side ends of the flange forming portions in a width direction to form corner portions at the starting and terminal end portions of the duct. In an expanded shape of plate-like materials 1A or 1B, a cut portion 2 is provided closer to a center in the longitudinal direction Za than a starting end 1s or a terminal end 1e of the plate-like member such that the cut portion extends in a width direction Ya of the plate-like member and has a depth substantially equal to an overlapping portion W1 of the corner forming portion 4. COPYRIGHT: (C)2007,JPO&INPIT
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