PURPOSE: To improve transportability With compactness introduced while reducing cost for transportation, to enlarge the scope of adaptability on installation, and to eliminate the need for heat insulating works while improving efficiencies in erection.
CONSTITUTION: On constructing an air duct using a flexible duct 1 that is composed of a flexible and heat-insulating cylindrical duct main body 2 and an expandable/contractile coil spring 3 to be detachably inserted into the duct main body 2 for keeping the duct main body 2 in cylindrical shape, the duct main body 2 is brought into a construction site, being folded up or wound up, while the coil spring 3 is also brought into the construction site, being kept in the contracted state. The duct main body 2 is unfolded on the construction site, and the coil spring 3 is expanded and inserted into the unfolded duct main body 2, and thereby the flexible duct 1 is erected, and the erected flexible duct 1 is installed on a place where the duct is to be installed.
KUMANO NAOTO
FUJIWARA HIROYUKI
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