GB575578A - Improvements in screw fan impellers - Google Patents

Abstract

575,578. Screw fans. COLLIERY ENGINEERING, Ltd., and REEVES, H. C. March 21, 1944, No. 5259. [Class 110 (i)] In order that the root b, Fig. 1, of an angularlyadjustable impeller blade a may be made of substantial size and strength without being unduly heavy it is dished so as to be hollow, the hollow being crossed by a stout rib d lying approximately under the blade. The hub of the impeller preferably has a part-spherical periphery and the heel of the blade is correspondingly curved so as to fit it closely at any pitch angle. In the form shown in Fig. 4 the hub is formed of two discs g formed with halfsockets h to receive the blade roots and clamped together, to hold the blades in any position, by bolts passing through bores m, m in the spaces between the sockets; the sockets are formed with grooves j to receive flanges c, Fig. 1, on the blade roots, and have stiffening ribs i. The two discs g are mounted on a metal bush o formed with flats tapering towards its ends to lock and wedge the discs against displacement. The webs k connecting the sockets may be provided in the planes of the outer faces of the discs instead of at the meeting faces. The hub may be provided with a fairing at each end, so that it need not be the full width of the blades. In a modified form, Fig. 5 (not shown), one set of half-sockets is formed on a central. web integral with the nave of the hub and the other set of half-sockets is formed in a removable ring clamped to it. The blade or its root may be formed of thermo-setting synthetic resin; the hub may be of similar material, in which case the half-sockets are provided with metal linings. According to the Provisional Specification, the rib d in the hollow blade root may be intersected by other ribs, and if the hub is formed of synthetic resin it may be provided with a longitudinal radial slot so that it can be clamped on to the metal bush.