US2804938A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Apparatus for filtering
Assignee: Northrop Grumman Space and Mission Systems Corp
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Filing: 1955-03-30
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Granted: 1957-09-03
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Expires: 1975-03-30
Abstract
No abstract record available.
Inventors
- 👤 Frank L Oppenheimer
- 👤 Donald R Frenk
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 09:30
CPC Classifications
B; B01; B01D; B01D46/00; B01D46/24; B01D46/2403; B01D46/2411
Claims Analysis
Total Claims: 0
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References Cited (Backward Citations)
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 |