GB1106390A - Fan impeller - Google Patents

Abstract

1,106,390. Moulding impeller hubs. WOODS OF COLCHESTER Ltd. 3 Dec., 1964 [5 Dec., 1963], No. 48171/63. Heading B5A. [Also in Division F1] In a fan impeller having blades adjustable about axes which are at a substantial inclination but not perpendicular to the axis of rotation of the impeller, each blade root tapers towards its end, the minimum included angle of the root being not less than twice the angle of inclination of the root axis to the direction in which a die part used for moulding the corresponding part of the impeller hub would be withdrawn, and the roots are held in corresponding recesses in the hub by screw members arranged axially of the roots. The impeller hub 12, Fig. 1, which is die-moulded from glassfibre reinforced resin has a steel sleeve 13 to engage the impeller shaft 11, and is held in place by a nut 14. Adjustable impeller blades 16 each have a conical root 18 fitting a corresponding recess 19 in the hub, a clamping bolt 22 being cast or moulded into the root. The head 23 of the bolt tapers similarly to the root 18 so that the material of the root is put in radial compression when the nut 21 is tightened, whereby the clamping forces are not added to the centrifugal forces on the root. The semiangle b of taper of the root 18 is made greater than the angle a between the blade axis 17 and the shaft axis 15 so that the innermost boundary 26 of the recess 19 slopes to the left towards the axis 15. Similarly, the semi-angle of taper of a countersink 27 is not less than a. This allows a die part against which the outer face or the inner face of the hub 12 is cast or moulded to be withdrawn in the direction of the axis 15. The hub surface 29 over which the end 28 of the blade 16 sweeps during adjustment is of spherical or other shape to provide a constant clearance. If a multi-part die is used for the outer face of the hub, having one part for each recess 19, the angle b may further be made not less than 90 degrees-a to allow the die parts to be withdrawn radially from the axis 15. The flat washer 24 may be replaced by a conical washer 24a, Fig. 3, fitting the countersink 27a. As shown, the root 18b and the recess 19b may be spherical, the angle between the tangent 26b at the mouth of the recess and the axis 17 being not less than a, in this example equal to b. Similarly, the washer 24a could be spherical., If a bolt similar to the bolt 22 of Fig. 1 is used, its head is shaped to correspond to the spherical shape of the root 18b to put the material of the root in compression. Alternatively, a stud 22a may be moulded into the root; or a bolt may be screwed into the root from inside the hub. The surface of the root or of the recess, or both, may be cut away to restrict the contact between them to three small circumferentially-spaced areas to ensure rigid location of the root. Any moulding flash on the root may be arranged to lie outside these areas so that it need not be removed.