Patent US3397515A successfully refreshed from Google Patents.
US3397515A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Hopper valve for filter bag installation
Assignee: Research Cottrell Inc
•
Filing: 1965-10-23
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Granted: 1968-08-20
•
Expires: 1985-10-23
Abstract
No abstract record available.
Inventors
- 👤 Robert R Johnson
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 10:28
CPC Classifications
B; B01; B01D; B01D46/00; B01D46/02; B01D46/04; B01D46/66; B01D46/70; B01D46/42; B01D46/4272; B01D46/48; F; F16; F16K; F16K1/00; F16K1/16; F16K1/18; F16K1/22
Claims Analysis
Total Claims: 0
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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) | 1971-08-20 | 1972-02-19 | 1972-08-20 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1975-08-20 | 1976-02-19 | 1976-08-20 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1979-08-20 | 1980-02-19 | 1980-08-20 | $7700.00 | Window Closed / Lapsed |