| 摘要 |
<p>A drilling tool intended for percussive rock drilling comprises two drill bits provided with crushing members (29, 30; 29a, 30a), viz.a central pilot bit (2) and a ring bit (3). The same are connectable with each other via a bayonet coupling comprising a number of pockets (47) recessed in one of the bits and in which drivers (24) included in the other bit are insertable for transmitting rotary motions to the ring bit (3). Furthermore, the tool includes a flush duct (33) mouthing in the front end of the pilot bit (2) and a number of internal evacuation channels (50) for the removal of drill cuttings. With the ring bit (3), a casing shoe (4) is connected via a coupling means (5), which, on one hand, guarantees that the casing shoe follows the ring bit axially, but on the other hand allows rotation of the ring bit in relation to the casing shoe. Said casing shoe comprises two internal and axially spaced-apart impact surfaces (58, 59), a rear one (59) of which co-operates with an impact surface (20) on the pilot bit (2) and a front one (58) with an impact surface (52) on the ring bit (3) to transmit impacts from the pilot bit to the ring bit. The invention furthermore relates to an expendable kit, a ring bit and a casing shoe for percussive rock drilling tool.</p> |
