GB758466A - Improvements in fan impellers - Google Patents

Abstract

758,466. Screw fans. KEITH BLACKMAN, Ltd., and WOODLEY, D. S. Jan. 12, 1955 [Jan. 14, 1954], No. 1104/54. Class 110(1) In a fan impeller having three blades, the chord pitch angle of each blade decreases from root to tip to give a substantially constant geometric pitch, and the blade surfaces in contact with the air are compoundly curved. 'In the fan impeller shown in Fig. 3, the blades 26 are attached to cast or fabricated supports 25 which are positioned at the required angle on flat surfaces 24 of the impeller hub 23. Each blade is pressed or fabricated of sheet metal, plastic or other material, or cast, and is of fully curved profile, and the working surfaces are of anticlastic curvature. The chord pitch angle decreases from root to tip to provide a substantially constant geometric pitch, and the root diameter is about 27 per cent of the tip diameter. The leading edge 30 of each blade is heavily curved forwardly from root to tip in the direction of rotation, while the trailing edge is lightly curved backwardly. Both edges 30, 31 are inclined slightly forwardly in an axial direction. In a modification, the blades are flanged at the roots for attachment to the hub. In a further modification, the blades are formed integral with one another and are attached to a flanged hub. According to the Provisional Specification, there may be four blades.