Issued Patents All Time
Showing 1–4 of 4 patents
| Patent # | Title | Co-Inventors | Date |
|---|---|---|---|
| 4851162 | Evaporative cooler | Douglas C. Sperr | 1989-07-25 |
| 4752419 | Evaporative cooler | Douglas C. Sperr | 1988-06-21 |
| 4576013 | Evaporative cooling | Douglas C. Sperr, Thad J. Genrich | 1986-03-18 |
| 4379712 | Evaporative cooler | Douglas C. Sperr | 1983-04-12 |