Patent US2939689A successfully refreshed from Google Patents.
US2939689A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Electrical heater for treating oilshale and the like
Assignee: Svenska Skifferolje AB
•
Filing: 1953-12-18
•
Granted: 1960-06-07
•
Expires: 1973-12-18
Abstract
No abstract record available.
Inventors
- 👤 Ljungstrom Fredrik
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 13:44
CPC Classifications
E; E21; E21B; E21B36/00; E21B36/04
Claims Analysis
Total Claims: 0
No claims parsed yet. Click Sync Now above to re-index claims from Google Patents.
References Cited (Backward Citations)
US547979A
Cited
US581170A
Cited
US2219544A
Cited
US2732195A
Cited
US849524A
Cited
US945321A
Cited
US1457479A
Cited
GB155732A
Cited
US1510655A
Cited
US2208028A
Cited
US2216786A
Cited
US2268978A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1963-06-07 | 1963-12-07 | 1964-06-07 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1967-06-07 | 1967-12-07 | 1968-06-07 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1971-06-07 | 1971-12-07 | 1972-06-07 | $7700.00 | Window Closed / Lapsed |