GB671607A - Improvements in or relating to multi-stage fans, pumps and the like - Google Patents

Abstract

671,607. Centrifugal and screw fans &c. DAVIDSON & CO., Ltd., and MACFARLANE, D. May 5, 1950, No. 11244/50. Class 110 (i) In a multistage fan, pump or the like, comprising, in a common casing, a centrifug a 1 impeller preceded by at least one axial flow impeller, the centrifugal impeller and the adjacent axial flow impeller being mounted to rotate synchronously in the same direction, means are provided to vary the ratio between output and rotational speed. An axialflow impeller 19 and a centrifugal impeller 15 are mounted on a common hub 16, as shown, or on separate hubs secured together. Their blades are of aerofoil form, but those of impeller 15 may instead be of laminar form. The pivot pins 20 of the blades of impeller 19 carry arms 22 which are mounted in spherical bearings 23 in a control ring 24 which is rotatable to vary the pitch of the blades in unison. Locknuts 21 permit separate adjustment of each blade. Inlet guide blades 25 are pivotally mounted on pins 50 which carry cranks 30 linked to a ring 32 mounted on the outside of an inlet flare 12. To adjust the guide blade pitch, the ring 32 is rotated by a handle 33 through linkage 34, or by hydraulic or automatic control mechanism. In a modification, additional guide blades are provided between the impellers 19 and 15. Their pitch may be adjusted separately from or simultaneously with that of the blades 25. In a further embodiment, an additional adjustablepitch axial-flow impeller is mounted in front of the impeller 19 and driven by a separate motor in the opposite direction.