US2839844A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Mathematical instruction game
Assignee: Individual
•
Filing: 1953-04-20
•
Granted: 1958-06-24
•
Expires: 1973-04-20
Abstract
No abstract record available.
Inventors
- 👤 Carl F Lehnkering
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 03:14
CPC Classifications
G; G09; G09B; G09B19/00; G09B19/02; A; A63; A63F; A63F9/00; A63F9/06; A63F9/12; A63F9/1204
Claims Analysis
Total Claims: 0
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References Cited (Backward Citations)
US239385A
Cited
US777268A
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US1115441A
Cited
FR525040A
Cited
US1696988A
Cited
US1843183A
Cited
AU2207329A
Cited
US2654963A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1961-06-23 | 1961-12-23 | 1962-06-24 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1965-06-23 | 1965-12-23 | 1966-06-24 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1969-06-23 | 1969-12-23 | 1970-06-24 | $7700.00 | Window Closed / Lapsed |