Under reamer
US4141421A · kind A · utility
Inventor
Key dates
| Filing date | Aug 17, 1977 |
| Grant date | Feb 27, 1979 |
| Priority date | — |
| Expiry date | Aug 17, 1997 |
Classification
- Technology area (CPC E)Fixed Constructions
- CPC primaryE21B10/34
- WIPO fieldCivil engineering
- WIPO sectorOther fields
Abstract
The present invention consists of an under reamer tool for enlarging, scraping or smoothing a well bore. The tool is attached to a conventional drill string above a conventional bit and involves cutting elements that have retractable cutters arranged for extension from the tool to engage the well bore wall, each cutter, when the drill string is turned, being urged outwardly by centrifugal force until it engages the well bore wall, continued turning thereafter, pulling that cutter into its extended cutting attitude, reaming the wall to the desired diameter, cutter retraction involving ceasing turning the drill string and the pulling of the drill string and connected tool from the well bore. During that pulling should the cutter contact a shoe or first reduction of the well bore casing or the wall thereof, it will be urged into a stowed attitude recessed within the tool body, the under reamer tool of the present invention also incorporating scouring openings provided in the tool body opposite to the cutter storage areas to pass liquid or air therethrough from the drill string to purge and clean that area within the tool body, allowing the cutter to travel freely therein.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.