Drill collar connections
USH1329H · kind H · statutory invention registration
Assignee
Inventors
Key dates
| Filing date | — |
| Grant date | Jul 5, 1994 |
| Priority date | — |
| Expiry date | — |
Classification
- Technology area (CPC —)General
Abstract
A threaded connection with improved fatigue-life useful for connecting adjacent sections of a pipe string subject to bending, tensile, and compressive stresses such as a drill collar string is disclosed. The connection comprises a pin member which is threadedly engageable with a corresponding box member. In the preferred embodiment, the inventive connection is designed to have bending strength ratio ("BSR") of about 3.20 or greater, and more preferably, in a range between about 3.20 and about 4.00. The preferred thread form of the connection is a V-type thread form having two flank angles of 30 degrees and a 0.038 inch root radius. Other design features may be used in combination with the threaded connection to further improve the connection's fatigue-life. Such design features include a tapered pin bore, an increased root radius for selected box threads, an internal box stress relief groove, a box bore stress relief groove, an extended pin relief groove, and modification of the API boreback box design to provide an increased number of threads having full threaded engagement.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.