GB700091A - Improvements in or relating to ventilating fans - Google Patents

Abstract

700,091. Centrifugal and screw fans. BARKER, D. R., and BARKER, W. H. April 17, 1951 (Feb. 16, 1950], No. 3998/50. Class 110 (1) In a ventilating fan, a closure plate 7, Fig. 1, slidably mounted on the impeller shaft 2, is pressed by spring means in a closing direction to interrupt the passage of air through the impeller 1 and is slidable into the open position shown dotted mainly or solely by the force of the air passing through the impeller, the spring means being caused to yield when the fan is running. Each spring means is made of spring wire shaped to provide a loop 13, Fig. 3, which engages in a groove in the periphery of a governor weight 10. Legs 15, which are inclined to the plane of the loop 13, fit into slightly inclined holes in the periphery of the impeller hub 12. When the fan is running, the weights 10 take up the positions shown dotted in Fig. 1 under centrifugal force, and the legs 15 are constrained into a different angular position relative to the spring arms 11. The resultant twist applied to the arms 11 causes the spring means to flex back to their original positions when the fan is stopped. The plate 7 is then held against a cork wasner 8 so as to seal the impeller inlet opening. The hub 12 may have a conical seating which engages a conical face on the hub 16 of the plate 7 so as to centralize the latter in the fully open position. The hub 16 'is of rubber, felt or graphite-impregnated plastic. The plate 7 may be of conical shape. In a modification, the impeller is of the axial-flow type, with radial blades attached at their tips to a shroud ring. In this case, the plate 7 is situated at the outlet side of the impeller.