US3021928A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Stair structure
Assignee: Individual
•
Filing: 1957-05-22
•
Granted: 1962-02-20
•
Expires: 1977-05-22
Abstract
No abstract record available.
Inventors
- 👤 Francis J Blair
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 03:22
CPC Classifications
E; E04; E04F; E04F11/00; E04F11/02; E04F11/022; E04F11/025
Claims Analysis
Total Claims: 0
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References Cited (Backward Citations)
US290878A
Cited
US340263A
Cited
US705794A
Cited
US1547254A
Cited
US2292046A
Cited
US2471352A
Cited
US2767959A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1965-02-19 | 1965-08-21 | 1966-02-20 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1969-02-19 | 1969-08-21 | 1970-02-20 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1973-02-19 | 1973-08-21 | 1974-02-20 | $7700.00 | Window Closed / Lapsed |