| 摘要 |
PROBLEM TO BE SOLVED: To provide a telescopic duct which is low-cost and capable of reducing transport costs and to prevent an inner tube from slipping off. SOLUTION: In the telescopic duct, the inner tube 2 is inserted into an outer tube 1 in a freely inserting/drawing manner and both the outer and inner tubes are spiral tubes. A spiral tube is low-cost compared to a roll tube, so that the telescopic duct becomes low-cost. Both the outer and inner tubes are formed by winding belt-shaped steel plate in spiral fashion and joints of the tubes are connected by seams, the joint of the outer tube 1 lapped by outer seams 1a and the joint of the inner tube 2 lapped by inner seams 2a. Thus, the outer tube 1 with the outer seams 1a has no projections on the inner surface while the inner tube 2 with the inner seams 2a has no projections on the outer surface. The inner tube 2 can be inserted into the outer tube 1 without a space between them, so that the telescopic duct can be used for an air conditioner or an exhaust duct without any trouble. A lap part L provided with a notch 3 and a protruding line 4 prevents the inner tube 2 from slipping off the outer tube 1. COPYRIGHT: (C)2003,JPO
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