Patent US2804839A successfully refreshed from Google Patents.
US2804839A
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US
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Air filter alarm systems and air filter alarm units
Assignee: Individual
•
Filing: 1954-12-14
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Granted: 1957-09-03
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Expires: 1974-12-14
Abstract
No abstract record available.
Inventors
- 👤 William W Hallinan
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 20:31
CPC Classifications
B; B01; B01D; B01D46/00; B01D46/10; B01D46/0084; B01D46/0086; B01D46/56; B01D46/58; F; F24; F24F; F24F13/00; F24F13/28; B01D2279/00; B01D2279/50; Y; Y10; Y10S; Y10S116/00; Y10S116/42; Y10S55/00; Y10S55/34
Claims Analysis
Total Claims: 0
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References Cited (Backward Citations)
US2682250A
Cited
US2750915A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1960-09-02 | 1961-03-04 | 1961-09-03 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1964-09-02 | 1965-03-04 | 1965-09-03 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1968-09-02 | 1969-03-04 | 1969-09-03 | $7700.00 | Window Closed / Lapsed |