GB479823A - Improvements in and relating to centrifugal fans - Google Patents

Abstract

479,823. Centrifugal fans. BRITISH THOMSON-HOUSTON CO., Ltd. June 1, 1937, No. 15224. Convention date, June 1, 1936. [Class 110 (i)] To reduce the noise of operation of a centrifugal fan with blades extending axially from the hub, sound-deadening material 32, Fig. 4, is located at the outlet in the space between the casing 20 and a perforated cut-off 29. The cut-off consists of a plate 30 extending partly around the impeller within the casing and doubled back to join the outlet edge of the casing parallel to the impeller axis. The blades 34, Fig. 5, are secured to a shroud ring 35 and extend partly through a curved orifice 27 secured to the inlet and extending to the shroud ring. The radial distance R between the outer edges of opposed blades at the shround ring 35 is 1À33 times the distance r at the hub ring 36 ; and the spacing A between the front wall 41 and the front end 42 of the discharge side 43 of the blades is 1À65 times the spacing B between the rear end 44 and the rear wall 45. The blades may be riveted to the hub and shroud rings, or may be cast with an integral part of each, the parts being secured by wire bindings 38, 39, Fig. 6. Each blade. Fig. 3, is raked at its rear end from the hub ring in an axial direction backwards from its direction of movement and at its forward end is curved forwardly, and increases in width from hub ring to shroud ring.