| 摘要 |
The device includes a chuck designed to be secured to a working tool and which has a front cavity for receiving an end of a drilling rod and a gripping device for fastening the end of the rod in this cavity. The gripping device is actuated by pneumatic or hydraulic pistons, sliding in a cylindrical chamber closed at the rear by a plug. In order to avoid rapid wear of this plug, a spring is arranged between the said plug and the adjacent face of the piston, the spring being strong enough to keep the piston away from the plug. |
