| 摘要 |
The present invention relates to a drill string element adapted to be coupled to other similar drill string elements by thread connections (19) thus forming a drill string for top hammer drilling. Each drill string element includes at least one rod (15;15 min ;15 sec ) for transferring impact energy to a drill bit (11) provided at the lower end of the drill string (10) and a tube assembly (21;21 min ;21 sec ) for transferring rotation to the drill bit (11), said tube assembly surrounding the rod. When handling drill string elements of the above-mentioned type it is extremely important that this handling can take place in a safe way without any risk for accidents during operation working site. Previously known drill string elements of the type in question have the disadvantage that the rod can fall out of the tube assembly in one direction. Also the accessibility to the interior of the drill string element in connection with repairs/service must be considered and the drill string elements must stay intact during operation, especially when they are unscrewed from each other. The invention is characterized by that the tube assembly (21;21 min ;21 sec ) in the area of the two ends of the rod (15;15 min ;15 sec ) is provided with an internal diameter reducing (27;27 min ,27 sec ;27'''), and that the rod (15;15 min ;15 sec ) is provided with cooperating radial projections (28;28 min ) or shoulder means (28 sec ). Also the tube assembly (21;21 min ;21 sec ) includes at least two tubular members (18;18 min ;18 sec ) that are coupled to each other by a thread connection that is harder to unscrew than the thread connection (19) for coupling together the drill string elements. |
