<；P>；PROBLEM TO BE SOLVED: To solve problems in a conventional agricultural ventilation fan that the fan needs large loading and storing spaces since it has a large bore diameter of about 1 m, and an impeller of a conventional constitution must be assembled once in a factory, and needs pitch balance adjustment. <；P>；SOLUTION: A disc-shaped rotating plate 7 is fitted to a shaft of a motor 1, and two sheets of rotary vanes 3 and two sheets of balance plates 4 are mounted to the rotating plate 7. The balance plates 4 are rotatable at a mounting position with the rotating plate 7. The rotary vanes 3 and the balance plates 4 are disposed on a roughly straight line by fixing the balance plates 4 in a state of overlapping to the rotary vanes 3. <；P>；COPYRIGHT: (C)2009,JPO&INPIT
