Issued Patents 1989
Showing 1–6 of 6 patents
| Patent # | Title | Co-Inventors | Date |
|---|---|---|---|
| 4886394 | Shield tunneling machine | — | 1989-12-12 |
| 4886396 | Existing pipeline renewing method and apparatus therefor | — | 1989-12-12 |
| 4874268 | Method and apparatus for building pipeline and shield tunnelling machine | — | 1989-10-17 |
| 4869619 | Method for excavating hole and apparatus therefor | — | 1989-09-26 |
| 4830539 | Pipe propelling apparatus | — | 1989-05-16 |
| 4815695 | Pipe propelling device | — | 1989-03-28 |