| 摘要 |
PROBLEM TO BE SOLVED: To fit a bit without retreat operation of an operation sleeve by engaging a key with a key groove of the bit with the bit in the fitted condition, and advancing a regulating sleeve to prevent the displacement outwardly in the radial direction of the key and to keep the engaged condition of the key to the key groove. SOLUTION: In the condition in which a bit is fitted, a key 5 is engaged with a key groove Ba of a bit B, and a key regulating part 8a of a regulating sleeve 8 is positioned on the outer circumferential side of the key 5. When the bit B is drawn in the bit fitting condition, the operation sleeve 12 is retreatively operated against a compression spring 13. Then, the regulating sleeve 8 is also retracted against the compression spring 13, and in this retreating process, a rear part 6b of a leaf spring 6 is pressed by a rear end part of the regulating sleeve 8. When the regulating sleeve 8 is further retreated, a key relief part 8b is positioned on the outer circumferential side of the key 5, and the displacement outwardly in the rear direction of the key 5 is permitted to allow the bit B to be drawn out. |
