GB848278A - Improvements in or relating to impellers - Google Patents

Abstract

848,278. Axial-flow fans. ENSO-GUTZEIT OSAKEYHTIO. April 15, 1958 [April 16, 1957], No. 11903/58. Class 110 (1). An impeller comprises one or more blades extending substantially radially from a shaft, and comprising a substantially flat leading main portion 1a and a roughly triangular trailing extension 1b having its longest side along a straight line a b of transition between the main portion and the extension, the leading edge of the main portion being straight and inclined at an angle of from 3 to 10 degrees (preferably 5 degrees) to a plane normal to the axis of the shaft so as to sweep part of the surface of an imaginary cone having its apex pointing upstream. The extension 1b may be substantially flat or may be of curved cross-section with its pitch gradually approaching zero and has its shortest side nearest to the shaft and at an angle of 30 to 45 degrees to the shaft. The pitch of the main portion 1a may be zero or may be larger, say 24 degrees. To reduce noise, the leading edge may be non-radial as viewed in the axial direction. The blades may be joined at their outer tips by a narrow ring. Two impellers may be mounted on one shaft, with the blades of one, as viewed in the axial direction, lying between the blades of the other.