Issued Patents All Time
Showing 1–4 of 4 patents
| Patent # | Title | Co-Inventors | Date |
|---|---|---|---|
| 4751799 | Method and apparatus for lining manhole assemblies and the like | Jack Ditcher, James R. Westhoff | 1988-06-21 |
| 4737220 | Method of making a manhole riser having integral flexible waterlock for manhole covers and having a water tight seal for sealed manhole covers | Jack Ditcher, James A. Westhoff | 1988-04-12 |
| 4621941 | Manhole riser having integral flexible waterlock for manhole covers and having a water tight seal for sealed manhole covers | Jack Ditcher, James A. Westhoff | 1986-11-11 |
| 4540310 | Manhole riser and cooperating sleeve to provide a waterlock for manhole structures | Jack Ditcher | 1985-09-10 |