Issued Patents 1989
Showing 1–3 of 3 patents
| Patent # | Title | Co-Inventors | Date |
|---|---|---|---|
| 4880058 | Stage cementing valve | Richard Adams | 1989-11-14 |
| 4862966 | Liner hanger with collapsible ball valve seat | Roger P. Allwin, Richard Adams | 1989-09-05 |
| 4828037 | Liner hanger with retrievable ball valve seat | Roger P. Allwin, Richard Adams | 1989-05-09 |