GB856668A - Improvements in or relating to axial-flow rotary impellers - Google Patents

Abstract

856,668. Axial-flow fans. AIR CONTROL INSTALLATIONS Ltd., and REEVES, H. C. July 10, 1959 [July 10, 1958], No. 22149/58. Class 110 (1). An axial-flow fan impeller comprises a hub from which extend outwardly a number of fixed blades having associated therewith on their leading or trailing edges, or both, adjustable blade extensions which can be clamped in selected positions of adjustment relative to the fixed blades for the purpose of adjusting the chord length of the blades. Fixed blade portions 10a extend radially from the periphery of an impeller hub 11, and diminish slightly in thickness towards their trailing edges. An extension for the trailing edge of each fixed blade portion 10a comprises two plates 15a which can be attached to the portion 10a in three alternative positions by means of screws 16a and nuts 17 passing through one or more radial rows of holes 16 in the plates 15a and corresponding rows of holes 14 in the portion 10a, thereby providing three different blade chord lengths. Those holes 16 not overlapping the portion 10a may also be provided with screws, as shown. The nuts 17 may be welded in place as shown or may be eliminated by the provision of tapped holes. The holes 14 or 16, or both, may be replaced by arcuate slots concentric with the axis of rotation. The blade extension may comprise one plate only, bolted to one side of the fixed portion 10a. The fixed portion may alternatively be of U-shaped crosssection, with the bend of the U at the leading edge 10b and the two limbs of the U embracing a single extension-plate. Or, the extension instead is of U-shaped cross-section. The extension-plates may have flanges which can be bolted to the periphery of the hub 11.