Patent US2448649A successfully refreshed from Google Patents.
US2448649A
Expired / Lapsed
US
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Duplex four-way valve
Assignee: Douglas Aircraft Co Inc
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Filing: 1944-04-17
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Granted: 1948-09-07
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Expires: 1964-04-17
Abstract
No abstract record available.
Inventors
- 👤 Harold W Adams
- 👤 Orville A Wheelon
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 06:49
CPC Classifications
F; F15; F15B; F15B13/00; F15B13/02; F15B13/06; Y; Y10; Y10T; Y10T137/00; Y10T137/8593; Y10T137/86493; Y10T137/86574; Y10T137/86831
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) | 1951-09-07 | 1952-03-08 | 1952-09-07 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1955-09-07 | 1956-03-08 | 1956-09-07 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1959-09-07 | 1960-03-08 | 1960-09-07 | $7700.00 | Window Closed / Lapsed |