Fecha de publicación: 27/11/1919 Fuente: WIPO "bee" 129,288. Bee, H. L. Sept. 29, 1916, [Convention date]. Impeller blades. - A fan used for creating suction in a dust-collecting apparatus is provided with curved blades 43 on spoke arms 47 extending radially from its shaft 28, the blades projecting from the arms 47 towards one side of the casing.