| CPC F04D 29/668 (2013.01) [F04D 29/547 (2013.01); F04D 19/002 (2013.01)] | 7 Claims |

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1. A damper for fan comprising:
a frame defining a passage for an airflow, having an inlet and an outlet; and
a pair of flaps hinged to the frame about respective rotation axes which are parallel to each other, said flaps being rotatable between an open and a closed position, for the opening and the closing of said passage, respectively,
wherein each of said flaps comprises a concave portion and a convex portion arranged on opposite axial halves of said respective flap, wherein in the closed position said concave portion has a concavity facing the inlet of said passage and a convexity facing the outlet of said passage, and said convex portion has a convexity facing the inlet of said passage and a concavity facing the outlet of said passage, and wherein the concave portion and the convex portion of one of said flaps have an inverted axial arrangement with respect to said concave portion and said convex portion of the other of said flaps.
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