Abstract: This invention relates to a fan suction chamber having front, back, and bottom walls. The front wall defines a suction inlet; and the back wall has an upper section, which is parallel to the front wall, and a lower section, which slants downward and forward toward the front wall of the suction chamber at an angle of 67.degree. to 78.degree. with the horizontal. The bottom wall of the suction chamber connects the front wall and the lower section of the back wall. The depth of the chamber at the upper section of the back wall is 0.35 to 0.38 times the width of the suction chamber, and the depth of the chamber at a lower end of the lower section of the back wall is 0.14 to 0.18 times the width of the suction chamber. The diameter of the suction inlet is 0.42 to 0.50 times the width of the suction chamber.

Abstract: Disclosed is a centrifugal-blower impeller, which consists of a center part and radially outer part, which has a smaller thickness of material than the center part. The outer part consists of ring segments attached by welding to the periphery of the center part. The ring segments are first welded to the center part and thereafter radially to each other so that the ring segments are subject to tensile stress and the center part to compressive stress.