Issued Patents All Time
Showing 1–5 of 5 patents
| Patent # | Title | Co-Inventors | Date |
|---|---|---|---|
| 8627854 | Pressure cast concrete or mortar lined steel pipes and methods of making the same | Ralph Friedrich, Qizhong Sheng | 2014-01-14 |
| 8069880 | Pressure cast concrete or mortar lined steel pipes and methods of making the same | Ralph Friedrich, Qizhong Sheng | 2011-12-06 |
| 5934712 | Double containment pipe mechanical joints | Ralph Friedrich | 1999-08-10 |
| 5716077 | Fire resistant sprinkler coupling | Ralph Friedrich | 1998-02-10 |
| 5714080 | Self-actuating molds for vertically casting concrete pipe | Ming-Che Kuo | 1998-02-03 |