Patent ID: 6491499
Filing Date: 2002-12-10
Classification: F04D

Abstract:
An axial flow fan of unitary molded plastic construction comprising: a cent hub rotatable on an axis; and a plurality of radial blades extending from the hub periphery, each of the blades comprising a root portion adjacent the hub and a curving mid portion terminating in a tip portion remote from the hub, and each of the blades having a substantially identical curved longitudinal centerline and being configured to perform a major part of its air moving function at its tip portion but with a substantial part of its air moving function at its mid piont portion, the root potions of the blades being substantially evenly spaced from each other circumferentially at their junctions with the hub, and at least some of the blades being substantially unevenly spaced circumferentially from each at both their mid portions and tip portions due to the blades being skewed with their center lines pivoted through unequal angles about selected points along the junction lines between the hub and the blade root portions, major sound attenuation improvement and lesser but nevertheless substantial sound attenuation improvement thus being achieved respectively at tip and mid portions of the blades.