PURPOSE: To permit saving of energy and changing of characteristics by a method wherein fixed blade impellers are divided into a plurality of sets and they are constituted so that these divided impellers can be driven individually and an arbitrary number of impellers can be selected to drive at any time.

CONSTITUTION: When one of the divided impeller 1A of the fixed blade impeller 1, which is fixed to a main driving shaft 2 connected directly to a driving machine (not shown in the diagram), is desired to be driven, the clutch handle 4A of a clutch device 4 is pivoted counterclockwise to a position shown by a two- dot chain line in the diagram, then, an internal gear 4C is displaced to a position shown by the two-dot chain line in the diagram. As a result, the internal gear 4C is released from an external gear 4D fixed to a sub driving shaft 3, to which the other divided impeller 1B is fixed, and the connection of the main driving shaft 2 with the sub driving shaft 3 is released, therefore, the divided impeller 1B does not move. Thus, any of the divided impellers 1A, 1B may be selected to drive at any time, therefore, saving of energy and changing of characteristics may be permitted.