| 摘要 |
A duct structure ( 50 ) includes lengths of square/rectangular duct ( 52 ) manufactured by pre-forming the duct in round cross-section ( 51 ) and then transforming the round cross-section into square and rectangular cross-sections utilizing expandable die structures ( 58 ). The duct ( 52 ) may be connected together end to end by flanged connectors ( 54 ) formed from strip stock ( 71 ), that is notched at locations that correspond to the corners of the formed flange connector. The cross-sectional profile of the flanged connector is then formed by roll forming and/or bending and/or other techniques. Thereafter, the strip stock is bent at its notched locations to define the corners ( 80 ) of the flange connector ( 54 ) and then the free ends of the strip stock are fixed together.
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