US3570291A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method of manufacturing extension springs
Assignee: NHK Spring Co Ltd
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Filing: 1968-10-07
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Granted: 1971-03-16
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Expires: 1988-10-07
Abstract
Abstract A CIRCULAR SECTION SPRING STEEL WIRE IS WOUND AROUND A MANDREL IN SUCH A WAY THAT ADJACENT TURNS OF THE SPRING STEEL WIRE ON THE PERIPHERY OF THE MANDREL ARE IN CLOSE CONTACT WITH EACH OTHER AND ARE SIMULTANEOUSLY TWISTED IN SUCH A DIRECTION OF ROTATION THAT THE SPRING STEEL WIRE TURNS ON THE MANDREL WHEN IT IS WOUND ON THE MANDREL, THE RESULT OF A GREAT AMOUNT OF INITIAL TENSION BEING IMPARTED TO THE EXTENSION SPRING.
Inventors
- 👤 Heijiro Shiguma
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 07:45
CPC Classifications
B; B21; B21F; B21F23/00; B21F3/00; B21F3/02; B21F3/04; B21F35/00; B21F35/02
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) | 1974-03-15 | 1974-09-14 | 1975-03-16 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-03-15 | 1978-09-14 | 1979-03-16 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-03-15 | 1982-09-14 | 1983-03-16 | $7700.00 | Window Closed / Lapsed |