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 09:47
CPC Classifications
E; E21; E21B; E21B36/00; E21B36/04
Claims Analysis
Total Claims: 0
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References Cited (Backward Citations)
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US581170A
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US1457479A
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GB155732A
Cited
US1510655A
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US2208028A
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US2216786A
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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 |