Issued Patents All Time
Showing 1–3 of 3 patents
| Patent # | Title | Co-Inventors | Date |
|---|---|---|---|
| 5853441 | Portable modular vacuum system | Douglas D. Groen | 1998-12-29 |
| 5369834 | Rotary duct cleaning brush device | Douglas D. Groen | 1994-12-06 |
| 4968333 | Apparatus for cleaning heating, ventilation, and air conditioning systems | James D. Ellis, II, Douglas D. Groen | 1990-11-06 |