| 发明名称 |
Well drilling tool - with central pilot bit and upper overlapping follower bits |
| 摘要 |
<p>A well drilling tool has a central pilot bit rigid with the drill string and a set of additional bits mounted on freely rotatable shafts parallel to the drill string so that each additional bit lies above the pilot bit and in overlapping relation thereto.</p> |
| 申请公布号 |
NL7105517(A) |
申请公布日期 |
1972.10.25 |
| 申请号 |
NL19710005517 |
申请日期 |
1971.04.23 |
| 申请人 |
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发明人 |
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| 分类号 |
E21B10/00;E21B10/28;E21B10/30;(IPC1-7):21B9/02;21B9/24;21D1/06 |
主分类号 |
E21B10/00 |
| 代理机构 |
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代理人 |
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| 主权项 |
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| 地址 |
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