| 摘要 |
<p>A control damper for controlling the flow of air or other gaseous fluid through a duct, comprising a line of blades each of which is so supported for rotation in a surrounding frame that the blades are swingable about parallel axes to open or close an opening in the frame and to be movable at will to intermediate positions between their fully-open and fully-closed positions, in which the blades are of aerofoil shape.</p> |
