| 摘要 |
PROBLEM TO BE SOLVED: To reduce a pressure loss caused by a fold at bending. ! SOLUTION: An air conditioning flexible duct D has a cylindrical inner coat material 1, a cylindrical heat insulation material 3 and a cylindrical outer coat material 4 on a cylindrical entire peripheral face of a strip reinforcing body 2 which is spirally and cylindrically wound. Fold promotion means 10 along a spiral direction of the reinforcing body is arranged at the inner coat material. The fold promotion means is constituted by pasting reinforcing tapes 11 or the like (Fig. (a), (b) and (c)), or providing folded lines 13 (Fig. (c), (d)). By arranging the fold promotion means, the number of folds a along the spiral direction in the inner coat material of a center portion between the opposing reinforcing bodies is increased, and when the number of the folds is increased, a diameter difference of internal/external peripheries at bending and elongation/contraction is absorbed by the protrusion of the folds, and a degree of the |
