Issued Patents All Time
| Patent # | Title | Co-Inventors | Date |
|---|---|---|---|
| 6024422 | Large displacement variable pitch screw-driven system | David Drennen, Gustavus P. Bock | 2000-02-15 |
| 5667283 | Variable screw-driven system | David Drennen | 1997-09-16 |
| 5667284 | Manually backdrivable ball screw assisted braking system | David Drennen | 1997-09-16 |