| 摘要 |
PURPOSE:To preclude progress of crack and prevent danger by a method wherein two small holes for precluding the progress of crack are formed on the root sections of the runner for a fan or the like, which consists of blade supports and blade pieces attached to the blade supports so as to be extended radially from the blade supports. CONSTITUTION:Two small holes 18, 18 are formed on the root sections 16a of respective blade pieces 16 so as to be positioned at the obliquely upper and obliquely lower positions of a rivet which is located at the side of the rotating direction of the runner among three rivets 17. When the blade piece 16 vibrates, high repeated stress acts near the rivet and the crack D is generated, the small holes 18, 18 exist and, therefore, the stress, concentrated at both ends of the crack D, is distributed to the whole peripheral rims of the openings of the small holes 18, 18. According to this constitution, the progress of the crack D may be precluded and the danger of breakage and fly-off of the blade pieces 16 may be prevented.
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