575,909. Centrifugal fans. JENNINGS, H. W. K. (Sturtevant Co., B. F.). April 17, 1944, No. 7073 [Class 110 (i)] The inlet box of a centrifugal fan 5, having the inlet 12 in a plane parallel to the fan shaft and the outlet to the fan centrally around the shaft, is provided with a vane 14 extending from the inlet towards and perpendicular to the shaft, to improve efficiency by ensuring that there is no empty space in the corner of the inlet box opposite to the inlet and outlet. The inlet box may be divided into two by a vane 15, at right-angles to the inlet 12 and the vane 14, which prevents spinning movement of the entering air ; the shaft lies in a gap in the vane 15. The vanes form a bracing for the walls of the inlet box.