Patent US4686624A successfully refreshed from Google Patents.
Patent US2721735A successfully refreshed from Google Patents.
US2721735A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Tubular heater with partial flue gas recirculation and heating method
Assignee: Shell Development Co
•
Filing: 1951-10-23
•
Granted: 1955-10-25
•
Expires: 1971-10-23
Abstract
No abstract record available.
Inventors
- 👤 Permann Karl
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 08:16
CPC Classifications
C; C10; C10G; C10G9/00; C10G9/14; C10G9/18; C10G9/20
Claims Analysis
Total Claims: 0
No claims parsed yet. Click Sync Now above to re-index claims from Google Patents.
References Cited (Backward Citations)
US1719684A
Cited
GB190427839A
Cited
US1706360A
Cited
US1642539A
Cited
US1717115A
Cited
US1933020A
Cited
US2441594A
Cited
US2549093A
Cited
US2590712A
Cited
US2555322A
Cited
US2684054A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1958-10-24 | 1959-04-25 | 1959-10-25 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1962-10-24 | 1963-04-25 | 1963-10-25 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1966-10-24 | 1967-04-25 | 1967-10-25 | $7700.00 | Window Closed / Lapsed |