| 摘要 |
At the front, the handpiece ( 1 ) has a clamp ( 10 ) fitted to tightly grip the shank of removable tool housed in the guide holes ( 23, 25 ). The clamp has two or more levers ( 26 ) attached to an annular section ( 22 ) of the clamp by elastic joints ( 27 ), each of which has a gripping jaw ( 20 ) to grip the tool shank. On each lever, the gripping jaw ( 20 ) is located much closer to the joint ( 27 ) than to a supporting surface, on which a tightening mechanism ( 17 ) exerts a centripetal force so that the lever multiplies this force. The tightening mechanism preferably has a sliding sleeve ( 40 ) having a conical inside surface ( 44 ), which produces said force at the levers of the clamp by means of balls ( 45 ) housed in the holes of the hollow rotatable shaft ( 11 ). Such an arrangement allows a weaker clamping spring ( 42 ) to be used, or even allows such a spring to be omitted. This allows some axial stresses on the ball bearings to be reduced.
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