Patent US3522665A successfully refreshed from Google Patents.
US3522665A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Teaching system
Assignee: Sprague Electric Co
•
Filing: 1967-12-12
•
Granted: 1970-08-04
•
Expires: 1987-12-12
Abstract
No abstract record available.
Inventors
- 👤 Charles G Kalt
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 11:06
CPC Classifications
G; G09; G09B; G09B7/00; G09B7/06; G09B7/08
Claims Analysis
Total Claims: 0
No claims parsed yet. Click Sync Now above to re-index claims from Google Patents.
References Cited (Backward Citations)
US2546666A
Cited
US2724910A
Cited
US2953859A
Cited
US3057082A
Cited
US3141244A
Cited
US3177595A
Cited
US3187443A
Cited
US3382588A
Cited
US3316660A
Cited
US3401470A
Cited
US3421231A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1973-08-03 | 1974-02-02 | 1974-08-04 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1977-08-03 | 1978-02-02 | 1978-08-04 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1981-08-03 | 1982-02-02 | 1982-08-04 | $7700.00 | Window Closed / Lapsed |