Issued Patents 1997
Showing 1–2 of 2 patents
| Patent # | Title | Co-Inventors | Date |
|---|---|---|---|
| 5645158 | Extensible continuous haulage system | Alan R. Polka, James J. Szalankiewicz | 1997-07-08 |
| 5590757 | Extensible continuous haulage system | Alan R. Polka, James J. Szalankiewicz | 1997-01-07 |