Issued Patents All Time
Showing 1–4 of 4 patents
| Patent # | Title | Co-Inventors | Date |
|---|---|---|---|
| 4643206 | Cigarette filter | Dorothy M. Frank, Tilford F. Riehl | 1987-02-17 |
| 4611607 | Cigarette filter | Dorothy M. Frank, Tilford F. Riehl, Andrew McMurtrie | 1986-09-16 |
| 4580584 | Cigarette filter | Dorothy M. Frank, Tilford F. Riehl | 1986-04-08 |
| 4387728 | Cigarette filter | Robert R. Johnson | 1983-06-14 |