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US2444756A
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Apparatus for progressively heating oil sands surrounding oil wells
Assignee: NAT SECONDARY RECOVERY CORP
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Filing: 1946-01-04
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Granted: 1948-07-06
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Expires: 1966-01-04
Abstract
No abstract record available.
Inventors
- 👤 Ralph M Steffen
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 12:22
CPC Classifications
E; E21; E21B; E21B36/00; E21B36/005
Claims Analysis
Total Claims: 0
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References Cited (Backward Citations)
US200393A
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US1309721A
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US956058A
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US1152392A
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US1626940A
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US2173556A
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US2335961A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1951-07-06 | 1952-01-05 | 1952-07-06 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1955-07-06 | 1956-01-05 | 1956-07-06 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1959-07-06 | 1960-01-05 | 1960-07-06 | $7700.00 | Window Closed / Lapsed |