Issued Patents All Time
| Patent # | Title | Co-Inventors | Date |
|---|---|---|---|
| 7409849 | Oil filtration system for plural phase power equipment tanks | David M. Butler | 2008-08-12 |
| 6476723 | Insulating oil leak containment | David C. Campbell, David McMahan Butler | 2002-11-05 |
| 6052060 | Temperature monitor for electrical switchgear | David McMahan Butler | 2000-04-18 |
| 5691706 | Transformer leak alarm | David McMahan Butler | 1997-11-25 |