Issued Patents All Time
Showing 1–4 of 4 patents
| Patent # | Title | Co-Inventors | Date |
|---|---|---|---|
| 8561730 | Foot valve assembly for a down hole drill | Jing James Yao, Paul Campbell, William H. Dell, II, Dale R. Wolfer | 2013-10-22 |
| 8215419 | Variable frequency control for down hole drill and method | Dale R. Wolfer, Paul Campbell | 2012-07-10 |
| 7992652 | Fluid distributor cylinder for percussive drills | — | 2011-08-09 |
| 7832504 | Exhaust valve and bit assembly for down-hole percussive drills | Dale R. Wolfer, Leland H. Lyon | 2010-11-16 |