| 摘要 |
A fire damper for a section of a duct (1) comprises one or more cranked doors (3) pivotally mounted on shafts (4). When the doors are moved to the closed position, panel sections (5) of the door mate against channel sections (6) projecting inwardly of the walls of the duct (1) and angled flaps (7) also mate against angled flanges (8) projecting from the duct. Symmetrical pivoting of the doors allows them to be swung freely from the open to closed positions and the cranking of the doors provides better rigidity.
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