Patent US1548993A successfully refreshed from Google Patents.
US2989952A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Combustion air preheater
Assignee: Individual
•
Filing: 1957-12-23
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Granted: 1961-06-27
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Expires: 1977-12-23
Abstract
No abstract record available.
Inventors
- 👤 Frederick W Richl
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 14:33
CPC Classifications
F; F28; F28F; F28F9/00; F28F9/02; F28F9/026; F28F9/0265; F23; F23M; F23M20/00; F28D; F28D7/00; F28D7/16; F28D7/1607; F28F27/00; F28F27/02
Claims Analysis
Total Claims: 0
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References Cited (Backward Citations)
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US2291872A
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US2386188A
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US2653799A
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US2723651A
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US2744733A
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US2817498A
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US2751037A
Cited
US2801830A
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1964-06-26 | 1964-12-26 | 1965-06-27 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1968-06-26 | 1968-12-26 | 1969-06-27 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1972-06-26 | 1972-12-26 | 1973-06-27 | $7700.00 | Window Closed / Lapsed |