Patent ID: 8651814

Claim:
An axial flow fan comprising: a hub rotatable about a central axis, the hub including a front face and a cylindrical portion; a plurality of blades extending radially outwardly from the cylindrical portion of the hub; a plurality of apertures through the front face of the hub, each aperture at least partially defined by a first surface oriented non-parallel with the front face; a plurality of ribs, each rib extending radially along an interior surface of the front face of the hub and aligned with one of the plurality of apertures such that a free edge of the rib at least partially overlaps the respective one of the plurality of apertures and provides a tortuous passageway through the respective aperture; and a plurality of lips, each lip coupled to the front face of the hub and aligned with one of the plurality of apertures that is not aligned with one of the plurality of ribs, each lip having a second surface, adjacent the first surface of a respective aperture, that at least partially overlaps the respective aperture and provides a tortuous passageway through the aperture.