GB761872A - Improvements in or relating to fan rotors and blade units therefor - Google Patents

Abstract

761,872. Screw fans. COLLINS, A. L. Sept. 7, 1954 [Sept. 15, 1953], No. 25489/53. Class 110 (1). A fan rotor comprises a boss having an undercut circumferential groove, and a blade unit mounted on the boss, the blade unit being an integral moulding comprising an anchor ring which fits into the circumferential groove and a number of fan blades which extend outwards from the anchor ring and are of soft elastic material. Four fan blades 11, Fig. 2, are moulded integrally with an anchor ring 12, of soft elastic material such as rubber, polyvinyl chloride or a synthetic rubber such as neoprene. The anchor ring 12 is slid over a substantially cylindrical surface 24 on to a conical surface 22 formed in a hub 13, and is held against radial displacement under centrifugal force by an undercut surface 23 and by a hub cap 20 which overlaps the anchor ring 12, the latter being recessed at 26 for this purpose. A screw 19 is threaded into the fan shaft 15 to hold the shaft and the cap 20 in position. A flat 18 on the shaft 15 engages a corresponding projection 17 formed in the bore 16 of the hub. A circumferentially-extending layer of a material such as canvas may be embedded in the ring 12 to reinforce it. In an alternative construction, Fig. 4, the cap 20 is omitted and the ring 12 is stretched over the front wall 24a of the circumferential groove 21 until it springs into place in the groove. The undercut shape of the rear wall 23 of the groove 21 retains the ring 12 in place, but if necessary clips or other retaining means may be used. A circumferentially-extending reinforcing wire may be embedded in the anchor ring near its larger diameter end. The anchor ring may be cylindrical. The hub may be formed in front and rear portions which are secured together by screws extending into the front portion from the hollow interior of the rear portion, the front portion overlapping or interengaging with the anchor ring to hold it in place in a circumferential recess in the rear portion. The Provisional Specification states that the circumferential recess in the hub which accommodates the anchoring may be of rhomboidal cross-section, with the front and rear walls inclined forwards at, say, 45 degrees to the axis. The anchor ring may be replaced by a conical cup with integral blades projecting outwards about midway between its front apex and rear rim and with an inwardly turned lip around its rear rim which engages a rearwardly directed rim on the hub.