US2421997A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Core barrel
Assignee: Shell Development Co
•
Filing: 1945-06-21
•
Granted: 1947-06-10
•
Expires: 1965-06-21
Abstract
No abstract record available.
Inventors
- 👤 Wilfred S Crake
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 23:04
CPC Classifications
E; E21; E21B; E21B10/00; E21B10/02; E21B10/04
Claims Analysis
Total Claims: 0
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References Cited (Backward Citations)
US1071199A
Cited
US1378056A
Cited
US1482397A
Cited
US1785405A
Cited
AT119296B
Cited
US1785120A
Cited
US1867024A
Cited
US1896469A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1950-06-09 | 1950-12-09 | 1951-06-10 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1954-06-09 | 1954-12-09 | 1955-06-10 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1958-06-09 | 1958-12-09 | 1959-06-10 | $7700.00 | Window Closed / Lapsed |