Issued Patents All Time
Showing 1–2 of 2 patents
| Patent # | Title | Co-Inventors | Date |
|---|---|---|---|
| 4889259 | Apparatus for injecting balls into a well | Donald L. Douglas, David W. Merryfield | 1989-12-26 |
| 4759469 | Apparatus and method for injecting balls into a well | Donald L. Douglas, David W. Merryfield | 1988-07-26 |