Issued Patents All Time
Showing 1–2 of 2 patents
| Patent # | Title | Co-Inventors | Date |
|---|---|---|---|
| 5253704 | High pressure automatic mud saver valve | Donald J. Barrus, Theodore A. Kritikos, John Owensby | 1993-10-19 |
| 4969513 | High pressure automatic kelly valve | Donald J. Barrus, Theodore A. Kritikos, John Owensby | 1990-11-13 |