Patent US4194173A successfully refreshed from Google Patents.
Patent US3765939A successfully refreshed from Google Patents.
US3765939A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method of coating cathode heaters
Assignee: GTE Sylvania Inc
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Filing: 1972-05-10
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Granted: 1973-10-16
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Expires: 1992-05-10
Abstract
Abstract A heater for use in an indirectly heated cathode of a vacuum tube is first coated with an insulating layer of alumina. Metallic tungsten is then vacuum deposited on the alumina in order to darken the color of the coating, thereby increasing its thermal emissivity.
Inventors
- 👤 R Reid
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 03:39
CPC Classifications
H; H01; H01J; H01J9/00; H01J9/02; H01J9/08
Claims Analysis
Total Claims: 2
Claim 1
Independent Claim
15 words
The process of claim 1 wherein said tungsten source comprises a plurality of tungsten wires.
Claim 2
Dependent Claim
26 words
The process of claim 1 wherein the weight of tungsten deposited on a heater is less than 1% of the weight of said aluminum oxide coating.
References Cited (Backward Citations)
US3206329A
Cited
US3504325A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-10-15 | 1977-04-16 | 1977-10-16 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-10-15 | 1981-04-16 | 1981-10-16 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-10-15 | 1985-04-16 | 1985-10-16 | $7700.00 | Window Closed / Lapsed |