Patent US3700951A successfully refreshed from Google Patents.
US3700951A
Expired / Lapsed
US
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Discharge lamps having improved thermionic cathodes
Assignee: Thorn Lighting Ltd
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Filing: 1971-02-09
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Granted: 1972-10-24
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Expires: 1991-02-09
Abstract
Abstract A thermionic cathode for discharge lamps is a two part structure consisting of a wire stem bearing a cup at its end, the cup being a receptacle for an electron-emitting composition and ensuring that electrons can only issue from the mouth of the cup and not by passage through the side of the cup. In one form, a foil is rolled around the end region of the stem, the rolled foil projecting beyond the end of the stem and thereby forming the cup. Instead of foil, a welded-coil may be used in a similar way to define the cup.
Inventors
- 👤 Maurice George Clarke
- 👤 Norman Burgess
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 03:33
CPC Classifications
H; H01; H01J; H01J61/00; H01J61/02; H01J61/04; H01J61/06; H01J61/073; H01J61/0735; H01J61/0737
Claims Analysis
Total Claims: 4
Claim 1
Independent Claim
155 words
A discharge lamp having an improved thermionic cathode, said cathode comprising: a refractory metal stem; a refractory metal tubular member secured on one end of said stem, said tubular member extending beyond the end of said stem to form a continuous walled cup; an electron-emitter composition contained within said cup; the extensional direction of said cup being substantially longitudinal with said discharge lamp, so that evaporated constituents of said electron-emitter composition do not deposit on the envelope of said discharge lamp during normal lamp operation; said electron-emitting composition containing: i. a refractory metal selected from the group consisting of tungsten, molybdenum and tantalum; ii. a second metal selected from the lanthanide series of elements and thorium in Group IIIa of the periodic classification, and iii. a third metal that is at least partly soluble in the second metal to form an alloy therewith, said alloy being capable of wetting said refractory metal in said composition.
Claim 2
Dependent Claim
155 words
A discharge lamp having an improved thermionic cathode, said cathode comprising: a refractory metal stem; a refractory metal tubular member secured on one end of said stem, said tubular member extending beyond the end of said stem to form a continuous walled cup; an electron-emitter composition contained within said cup; the extensional direction of said cup being substantially longitudinal with said discharge lamp, so that evaporated constituents of said electron-emitter composition do not deposit on the envelope of said discharge lamp during normal lamp operation; said electron-emitting composition containing: i. a refractory metal selected from the group consisting of tungsten, molybdenum and tantalum; ii. a second metal selected from the lanthanide series of elements and thorium in Group IIIa of the periodic classification, and iii. a third metal that is at least partly soluble in the second metal to form an alloy therewith, said alloy being capable of wetting said refractory metal in said composition.
Claim 3
Dependent Claim
47 words
The combination according to claim 1, wherein said tubular member is a helically-wound wire-coil, turns of said coil contacting one another and at least those turns thereof which extend beyond the end of said stem to define said cup being welded together thereby forming a continuous wall.
Claim 4
Dependent Claim
20 words
The combination according to claim 1, wherein a foil wrapped around the end of said stem forms said tubular member.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1975-10-24 | 1976-04-24 | 1976-10-24 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-10-24 | 1980-04-24 | 1980-10-24 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-10-24 | 1984-04-24 | 1984-10-24 | $7700.00 | Window Closed / Lapsed |