Load cells for sensing weight and torque on a drill bit while drilling a well bore
US5386724A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Aug 31, 1993 |
| Grant date | Feb 7, 1995 |
| Priority date | — |
| Expiry date | Aug 31, 2013 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01L5/1627
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A load cell for sensing weight and torque on a drill bit during a drilling operation includes a cylindrical load cell made from a material with minimum residual stress. A plurality of strain gages are arranged symmetrically on each load cell and electrically coupled to form two Wheatstone bridges. The load cells are mounted 180 degrees apart in radial pockets drilled in a drill collar wall. A half Wheatstone bridge from one load cell is electrically coupled with a half Wheatstone bridge from the other load cell to form a Wheatstone bridge for measuring WOB and a similar coupling is made to form another Wheatstone bridge for measuring TOB. In another embodiment, additional strain gages in another Wheatstone bridge measure differential pressure. The output of the pressure and weight bridges are electrically combined to provide a weight signal unaffected by differential pressure fluctuations. The load cells are force fit in the radial pockets in the drill collar and a cap is installed on each pocket housing a load cell to protect the load cell from drilling fluid. The strain gages in each load cell are placed to minimize the effects of bending, hydrostatic pressure, temperature, diffe…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.