Patent US2213631A successfully refreshed from Google Patents.
US2213631A
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US
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Method of and apparatus for magnetically recording sound
Assignee: Heller
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Filing: 1937-10-25
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Granted: 1940-09-03
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Expires: 1957-10-25
Abstract
No abstract record available.
Inventors
- 👤 Herman S Heller
- 👤 Leo G Butler
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-22 19:31
CPC Classifications
G; G11; G11B; G11B15/00; G11B15/70; G11B5/00; G11B5/48; G11B5/49; G11B5/4969
Claims Analysis
Total Claims: 0
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References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1943-09-03 | 1944-03-04 | 1944-09-03 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1947-09-03 | 1948-03-04 | 1948-09-03 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1951-09-03 | 1952-03-04 | 1952-09-03 | $7700.00 | Window Closed / Lapsed |