| 摘要 |
PROBLEM TO BE SOLVED: To provide a dart of high durability facilitating connection work of a shaft and a flight and making the flight smoothly rotatable in a circumferential direction. SOLUTION: The front end face of the shaft 4 and the rear end face of a tip include a plurality of locking protrusions provided at equal spaces in a circumferential direction. The shaft 4 is formed in tapered shape, and the rear end is provided with a hollow part 11 opening the rear end. The internal wall surface of the shaft 4 is provided with protrusions 12 projected radially inward at predetermined spaces in positions along the circumferential direction. Blades are mounted to the peripheral surface of a flight shaft 13. An insertion shaft 15 is integrally and continuously provided at the front end of the flight shaft 13 with a level difference. A fitting groove 16 to which the protrusions 12 are fittable is provided recessed in a circumferential direction, and a small diameter part 17 having a predetermined length in an axial direction is provided recessed in a circumferential direction. The outer diameter, excluding the small diameter part 17 and the fitting groove 16, of the insertion shaft 15 is formed to be slightly smaller than the inner diameter of the hollow part 11 of the shaft 4. COPYRIGHT: (C)2011,JPO&INPIT
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