Issued Patents All Time
Showing 1–2 of 2 patents
| Patent # | Title | Co-Inventors | Date |
|---|---|---|---|
| 4278137 | Apparatus for extracting minerals through a borehole | — | 1981-07-14 |
| 4191266 | Process and installation for drilling holes in the earth's crust under freezing conditions | Arnold W. J. Grupping | 1980-03-04 |