摘要 |
A ventilation fan assembly ( 10 ) having a fan ( 22 ) mounted in a housing ( 12 ) and a shutter assembly ( 60 ). The housing has a square inlet portion ( 12 C), a circular center portion ( 12 E) and a conical outlet portion ( 12 D) having rifling grooves ( 20 ). The shoulder ( 16 ) formed between the inlet portion and the center portion is radiused to reduce disruption of air flowing from the inlet portion to the center portion. The shape of the blades ( 32 ) of the propeller ( 28 ) is such that the axial velocity produced as the propeller rotates is essentially constant along the length of the blades. The shutter assembly has a large, radiused entrance and airfoil shaped blades which reduce air disruption. The blades have a flexible flap ( 68 ) along the trailing edges ( 64 D) which form a seal between adjacent blades to prevent air from leaking from the housing through the shutter assembly.
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