Patent ID: 8105011

Claim:
A fan adapted for cooling a circuit board ( 26 ), comprising a fan wheel ( 10 , 10 ′) configured for rotation about a rotation axis ( 11 ) and in a predetermined rotation direction ( 14 ) and formed with an outer guidance wall ( 18 ) that is rigidly joined to an inner guidance wall ( 16 ), a plurality of curved air-directing conduits ( 39 ) being defined between the two walls ( 16 , 18 ), which conduits each extend in helical fashion from an axial entrance opening ( 40 ) to a radial exit opening ( 42 ), each axial entrance opening ( 40 ) furthermore being at a lesser distance from the rotation axis ( 11 ) than a corresponding radial exit opening ( 42 ), the air-directing conduits ( 39 ) being separated from one another by air-directing blades ( 30 , 32 , 34 , 36 , 38 ) that each extend, oppositely to said predetermined rotation direction ( 14 ), from a point between two entrance openings ( 40 ) to a point between two exit openings ( 42 ), in order to convert a flow direction of entrained air from an axial flow direction at the entrance opening ( 40 ) to a flow direction at the exit opening ( 42 ) that is substantially normal to said rotation axis ( 11 ), and wherein the inner guidance wall ( 16 ) is formed with at least one orifice ( 80 ′) that enables a cooling air flow from an air-directing conduit ( 39 ) through said inner wall ( 16 ) of the fan wheel ( 10 ), wherein said cooling air flow cools said circuit board ( 26 ); an electronically commutated motor having an external rotor ( 50 ), said inner air guidance wall ( 16 ) of the fan wheel being coupled, in a central region thereof, to said external rotor ( 50 ) via a joining element ( 52 ) so that the external rotor ( 50 ), in operation, drives the fan wheel ( 10 ) in the predetermined rotation direction.