Patent ID: 7455502

Claim:
An axial fan in which an impeller ( 1 ) comprises a hub ( 2 ), motor-powered so that it rotates about its own central axis ( 3 ) in a predetermined direction of rotation (V), and a plurality of blades ( 5 ) extending from the hub ( 2 ) in directions transversal to the axis ( 3 ); the hub ( 2 ) having a cup shape and being formed by a bottom wall ( 6 ) and a ring-shaped side-wall ( 7 ); the bottom wall ( 6 ) having a plurality of long ribs ( 20 ) arranged in a radial direction and extending in height towards the hub ( 2 ) cavity, each of the ribs ( 20 ) abutting on an internal face of the ring-shaped side wall ( 7 ) and delimiting, together with said ring-shaped side wall ( 7 ), a corner area of the bottom wall ( 6 ) positioned in front of the rib ( 20 ) with reference to the direction of rotation (V); the fan being characterized in that each corner area has a through-hole ( 9 ) for discharging any debris, in particular water, sand, soil or sludge, from the hub ( 2 ) cavity to the outside of the hub ( 2 ); in each of said corner areas the through-hole ( 9 ) is delimited by at least three walls ( 10 - 15 ), of which a first wall ( 10 ) substantially acts as an extension of the ring-shaped side wall ( 7 ) and of which a second wall ( 11 ) substantially acts as an extension of the rib ( 20 ); each of the said through-holes ( 9 ) being positioned between two circumferentially adjacent ribs ( 20 ) and substantially closer to one adjacent rib ( 20 ) than the other.