Patent ID: 8257034

Claim:
A radial fan comprising: a casing having a front wall, an inlet, an outlet, a side portion defining a planar wall, a pot-shaped casing portion and defining a casing scroll, an impeller wheel in the casing including a hub, a cover disc and a plurality of radially extending blades extending between the hub and the cover disc each of the plurality of radially extending blades defining a straight edge disposed parallel to and immediately adjacent the planar wall of the side portion of the casing, the impeller drawing fluid in through the inlet at a radial center portion of the impeller wheel and blowing the fluid out the outlet at a radial outer portion of the impeller wheel, an electric motor at the side portion, a pressure chamber formed by the casing portion and the side portion, and a flow channel for said fluid extending between said inlet and said outlet being defined by said planar wall of said side portion of said casing, adjacent blades of said impeller wheel, said hub and said cover disc, said flow channel extending between the hub and the cover disc to form in a cross-section a nozzle in the manner of a venturi nozzle; wherein a narrowest cross-section of the venturi nozzle is defined by a surface of the impeller wheel at an outer circumferential edge of the impeller wheel and a surface of the planar wall of the side portion of the casing, the narrowest cross-section extending perpendicular to the planar wall of the side portion; the ratio of the greatest blade height H/greatest diameter D of the casing scroll is between H/D=0.08 and H/D=0.3, the casing has a tongue portion extending into said pressure chamber; and said tongue portion is provided on the casing portion in the form of a ramp which rises in the flow direction on the front wall of the casing portion.