Patent ID: 7946804

Claim:
An axial fan unit comprising: a first impeller including a plurality of first blades which are disposed about a center axis; a first motor operable to rotate the first impeller about the center axis to create a first flow of air generally flowing along the center axis; a second impeller adjacent to the first impeller and including a plurality of second blades disposed about the center axis; a second motor operable to rotate the second impeller about the center axis to create a second flow of air flowing generally in a direction of the first flow of air; a housing arranged to surround the first impeller and the second impeller; and a plurality of ribs disposed between the first impeller and the second impeller and connected at least to the housing and the first motor; wherein first impeller side edges of the plurality of ribs and second impeller side edges of the plurality of ribs are both inclined with respect to a radial direction that is perpendicular or substantially perpendicular to the center axis; and the second impeller side edges of the plurality of ribs and first impeller side edges of the plurality of second blades are arranged at identical angles such that an axial distance between the second impeller side edges of the plurality of ribs and the first impeller side edges of the plurality of second blades remains constant.