System for boring raises having portions of different diameters
US4177866A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | May 30, 1978 |
| Grant date | Dec 11, 1979 |
| Priority date | — |
| Expiry date | May 30, 1998 |
Classification
- Technology area (CPC E)Fixed Constructions
- CPC primaryE21B10/345
- WIPO fieldCivil engineering
- WIPO sectorOther fields
Abstract
A raise boring system is provided for boring raise holes wherein the finished raise holes have portions of different diameters. The system includes a raise head with a central drive stem defining an axis of rotation. Primary cutter means are positioned on the raise head for disintegrating the earth formations out to a first radial distance from said axis of rotation. Expanding secondary cutter means are positioned on the raise head for selectively disintegrating earth formations from said first radial distance out to additional and greater radial distances from said axis of rotation. The expanding secondary cutter means may be selectively located in a first position either beneath or in the same plane as the primary cutter means during boring at said first radial distance from said axis of rotation and selectively located in additional positions for boring at greater radial distances from said axis of rotation. Expansion means are provided for moving said expanding secondary cutter means to said additional positions during the boring operation.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.