Issued Patents All Time
| Patent # | Title | Co-Inventors | Date |
|---|---|---|---|
| 4674167 | Method of converting a single chambered conduit to a multi-chambered conduit | Donald E. Berkemeier | 1987-06-23 |
| D285192 | Underground conduit | Donald E. Berkemeier | 1986-08-19 |
| 4585034 | Apparatus for converting a single chambered conduit to a multi-chambered conduit | Donald E. Berkemeier | 1986-04-29 |
| 4582093 | Fiber optic duct insert | Donald E. Berkemeier | 1986-04-15 |