GB1102110A - Improvements in or relating to impellers for axial flow fans - Google Patents

Abstract

1,102,110. Axial-flow fans. KœHNLE, KOPP & KAUSCH A. G. Jan. 18, 1967 [Feb. 1, 1966], No.2747/67. Heading F1C. In order to reduce the natural frequencies of oscillation of the impeller blades of a large axial-flow fan, e.g. for cooling towers, the stub shaft 7, Fig. 1, of each blade 8 is supported by spring elements 14, 23, 16 and 15, 24, 17 and has a part-spherical portion 9 movably seated in a bearing 10, 11. Each spring element may be entirely of steel or, as shown, comprises a rubber or other elastic member 23 or 24 sandwiched between a pair of metal plates 14, 16 or 15, 17. The spring elements are of greater dimension in the peripheral direction of the impeller than in the axial direction thereof to provide softer springing in the axial direction. Deflection of the blade in the peripheral direction may be limited by stop bars (32, 33), Fig. 2 (not shown). The axis Y of the blade is inclined by angle # to radial axis Z, to produce an equilibrium of moments due to the centrifugal and axial aerodynamic forces exerted on the blade. The portion 10 of bearing 10, 11 is welded to a pair of channel-section carriers, one of which is shown at 4. The carriers are welded to a pair of annular plates 2, 3 connected to a shaft receiving sleeve 1. The plates may be star-shaped with the cut-outs intermediate the blade stubs. The spring elements are connected to a plate 12 welded to the carriers, by bolts 13 which pass through arcuate slots 22 in the plate to permit some angular adjustment of the spring elements and blade. The blade can be angularly adjusted independently of the spring elements after loosening of bolts 21 of a split clamping ring 18, 19 bolted at 20 to the spring elements.