| 摘要 |
A release piece for a drill string is adapted to disengage upon activation in connection with a bit stuck in the lower portion of the bore hole during drilling. An elongated tubular release piece (10a, 10b) is, at the ends (12a, 12b) thereof, formed to be coupled into the drill string, upstream the bit. The drill string release piece comprises two substantially coaxial sleeve parts (10a, 10b) disposed in the continuation of each other and screwable together, said sleeve parts (10a, 10b) internally being provided with axially directed locking means (16a, 16a', 16b, 16b'). An internal, axially displaceable locking device (18) has locking means (28', 28") capable of cooperating lockingly with said locking means (16a, 16a', 16b, 16b') of both sleeve parts (10a, 10b), the locking position being maintained by means of a spring (22). In a drill string release situation, the spring action is neutralized, the drill string, thereafter, being rotated in order to unscrew the two sleeve parts (10a, 10b) from each other, whereafter the drill string can be hauled up. |
