Patent ID: 8740562

Claim:
A fan comprising: an impeller including a plurality of blades centered about a central axis and projecting radially outward from the central axis in such a way as to be arranged circumferentially about the impeller; a motor that rotates the impeller about the central axis; a base supporting the motor; an air channel portion enclosing the impeller from a radially outer side to provide an air passage; and a plurality of supports projecting radially outward from the base and fixedly coupled to the air channel portion; wherein the air channel portion includes an upper opening at a first end and a lower opening at a second end, in a direction of the central axis, the air channel portion further including a plurality of outer peripheral surfaces with ones of the plurality of outer peripheral surfaces being perpendicular to other ones of the plurality of outer peripheral surfaces; each of the upper and lower openings includes a sloping region in which the air passage is increased in cross-sectional area toward each open end in a direction substantially normal to the central axis; a straight portion is provided between the upper and lower openings along which the air passage is substantially constant in cross-sectional area in the direction substantially normal to the central axis direction; the straight portion includes a plurality of slits defined by substantially straight channels penetrating radially and arranged circumferentially with respect to the central axis to allow flow of air between a radially inner side and a radially outer side of the air channel portion; the slits are provided in each of the plurality of outer peripheral surfaces, a penetrating direction of each of the slits is inclined from a straight line that is normal or substantially normal to each of the plurality of outer peripheral surfaces in a direction opposite to a rotation direction of the impeller; and the penetrating directions of the slits are parallel or substantially parallel to one another in each respective one of the plurality of outer peripheral surfaces.