Issued Patents All Time
Showing 1–5 of 5 patents
| Patent # | Title | Co-Inventors | Date |
|---|---|---|---|
| 4553876 | Method and apparatus for laying drains in frost-susceptible ground, and drains laid in such ground | Thord I. Engstrom | 1985-11-19 |
| 4486122 | Method and device for reducing the risk of freezing of surface-water pipe-line systems | Thord I. Engstrom | 1984-12-04 |
| 4475844 | Method and apparatus for restricting local variations in ground level in the vicinity of surface water drains and manholes | Thord I. Engstrom | 1984-10-09 |
| 4419232 | Filtering and collecting device for water drains | Thord I. Engstrom | 1983-12-06 |
| 4325572 | Arrangement in rain-water drains or manholes | Thord I. Engstrom | 1982-04-20 |