US Patent 10288078 Electrical machine, fan, ventilator

An axial flow fan having an axis of rotation includes a central hub including a base wall and a lateral wall which projects from the base wall to form a cup-shaped structure, a plurality of blades each fixed to the central hub and including a leading edge and a trailing edge, a plurality of extractors of a fluid which are associated with the base wall for conveying air from the inside of the cup-shaped structure to the outside of the cup-shaped structure through the base wall.