Patent US2581223A successfully refreshed from Google Patents.
US2581223A
Expired / Lapsed
US
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Permanent magnet system for loudspeakers
Assignee: Individual
•
Filing: 1948-03-04
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Granted: 1952-01-01
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Expires: 1968-03-04
Abstract
No abstract record available.
Inventors
- 👤 Voigt Paul Gustavus Ad Helmuth
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 11:07
CPC Classifications
H; H04; H04R; H04R9/00; H04R9/02; H04R9/025
Claims Analysis
Total Claims: 0
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References Cited (Backward Citations)
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US2174355A
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US2141595A
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US2501032A
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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) | 1954-12-31 | 1955-07-02 | 1956-01-01 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1958-12-31 | 1959-07-02 | 1960-01-01 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1962-12-31 | 1963-07-02 | 1964-01-01 | $7700.00 | Window Closed / Lapsed |