| 摘要 |
PCT No. PCT/SE89/00720 Sec. 371 Date Jun. 6, 1991 Sec. 102(e) Date Jun. 6, 1991 PCT Filed Dec. 8, 1989 PCT Pub. No. WO90/06416 PCT Pub. Date Jun. 14, 1990.A telescopically extensible drill comprises a drill barrel, a drill bit connected to the barrel, and a drill rod which can be displaced between two longitudinally spaced positions in relation to the drill barrel, and secured in either of those positions. The drill can thus be extended in length without having to splice additional barrels or rods to the drill. |
