Patent US2621631A successfully refreshed from Google Patents.
US2621631A
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US
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Telescopic hydraulic mine roof support
Assignee: Dowty Equipment Ltd
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Filing: 1948-11-08
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Granted: 1952-12-16
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Expires: 1968-11-08
Abstract
No abstract record available.
Inventors
- 👤 George H Dowty
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 09:54
CPC Classifications
E; E21; E21D; E21D15/00; E21D15/60; E21D15/14; E21D15/44; E21D15/45
Claims Analysis
Total Claims: 0
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References Cited (Backward Citations)
US151670A
Cited
US1133270A
Cited
US1598426A
Cited
US1805588A
Cited
US1706309A
Cited
US2284228A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1955-12-16 | 1956-06-16 | 1956-12-16 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1959-12-16 | 1960-06-16 | 1960-12-16 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1963-12-16 | 1964-06-16 | 1964-12-16 | $7700.00 | Window Closed / Lapsed |