PURPOSE: To easily find breakage or the like of a main support part visually from an outer apperance by providing on inter-blade spacers the main support part which supports the inter-blade spacers to circular bodies, and a positioning pin for positioning to the circular body, and a sub-support part between the main support part and the positioning pin, and forming a gap between an outer periphery of the sub-support part and the circular body.

CONSTITUTION: A plurality of blades are arranged between inter-blade spacers 2. Both ends of the inter-blade spacers 2 are provided on a circular body 7, and the blades are rotated around an axis of the circular body 7. A main support part 4 which supports the inter-blade spacer 2 to the circular body 7 is projected outward from both ends of the inter-blade spacer, and a positioning pin 5 is projected to one end. A sub-support part 6, made of a bolt for instance, is arranged between the main support part 4 and the positioning pin 5, and a gap is formed between the outer periphery thereof and the circular body 7. When the main support part 4 is broken by the centrifugal force, the inter-blade spacers 2 are rotated around the positioning pin 5. The rotation is regulated by the gap of the sub-support part 6. Breakage or the like is easily found by the inclination.