GB796696A - Improvements in or relating to centrifugal fans - Google Patents

Abstract

796,696. Centrifugal fans. DAVIDSON & CO., Ltd. July 19, 1956 [July 19, 1955], No. 20879/55. Class 110 (1). In a centrifugal fan adapted for entry of air in an axial direction, the impeller back-plate is conical whereby its face on which the air impinges is disposed at an angle greater than 90 degrees to the impeller axis, and a conical ring is secured to the rear face of the fan casing, the ring being of similar conicity to the backplate and so positioned that its front face is substantially a radial continuation of the front face of the back-plate. In the fan shown, the impeller back-plate 14 is of conical form, at an angle to the axis 15 of, preferably, not less than 105 degrees, say 110 degrees. A stationary ring 19, of similar conicity to that of the backplate 14, forms a continuation of the backplate. The impeller shroud 13 is also conical, at an angle of about 140 degrees to the axis 15. The leading edge 17 of the impeller blades is substantially perpendicular to the surface of the back-plate 14. The trailing edge 18 is parallel to the axis 15. The blades are of aerofoil section and each comprise a hollow part 23 joined to a solid triangular part 25 along a line 24 parallel to the leading edge 17. The blades may be at a slight angle to the axis 15 or may be helically curved. The fan may be of double inlet type, with two single-inlet impellers placed back-to-back, the casing having a central division plate carrying a conical ring 19 on either side.