Patent ID: 7762769

Claim:
An axial fan assembly comprising: a motor including an output shaft rotatable about a central axis; a shroud coupled to the motor, the shroud including a substantially annular outlet bell centered on the central axis; an axial fan including a hub coupled to the output shaft for rotation about the central axis; a plurality of blades extending radially outwardly from the hub and arranged about the central axis; a substantially circular band coupled to the tips of the blades; and a plurality of leakage stators positioned radially outwardly from the band and adjacent the outlet bell, the leakage stators arranged about the central axis; wherein the outlet bell includes a radially-innermost surface, a radially-outermost surface, and an end surface adjacent the radially-innermost surface, wherein the leakage stators are positioned between the radially-innermost surface and the radially-outermost surface, wherein the band includes an axially-extending, radially-innermost surface, an axially-extending, radially-outermost surface, and an end surface adjacent the axially-extending, radially-innermost surface and the axially-extending, radially-outermost surface, wherein the respective end surfaces of the band and the outlet bell are spaced by an axial gap, and wherein a ratio of the axial gap to a maximum blade diameter is about 0 to about 0.01, wherein the axially-extending, radially-outermost surface of the band is spaced radially inwardly of the radially-innermost surface of the outlet bell by a radial gap, and wherein a ratio of the radial gap to the maximum blade diameter is about 0.01 to about 0.02.