Patent US4675570A successfully refreshed from Google Patents.
US4675570A
Expired / Lapsed
US
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Tungsten-iridium impregnated cathode
Assignee: Varian Medical Systems Inc
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Filing: 1986-04-11
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Granted: 1987-06-23
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Expires: 2006-04-11
Abstract
Abstract Porous agglomerates are made from pure tungsten by sintering fine particles together and mechanically breaking down the mass to form some agglomerates considerably larger than the particles. These agglomerates are mixed with fine iridium powder and sintered to form a porous mass. The mass is machined to the cathode shapes and impregnated with an alkaline earth aluminate. The large agglomerates alloy with the iridium only on their outer surface. Their pure tungsten interior provides the surfaces to reduce the alkaline earth oxide to the metal which activates the cathode.
Inventors
- 👤 Michael C. Green
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 09:29
CPC Classifications
H; H01; H01J; H01J1/00; H01J1/02; H01J1/13; H01J1/20; H01J1/28; H01J9/00; H01J9/02; H01J9/04
Claims Analysis
Total Claims: 17
Claim 1
Independent Claim
83 words
A thermionic cathode comprising: a porous matrix of an alloy of at least one noble metal of the platinum group with a refractory metal of the group consisting of tungsten, molybdenum and alloys of these, porous agglomerates dispersed in said matrix having dimensions large compared to the components of said matrix, said agglomerates being composed of one of said refractory metals, and the pores of said matrix and said agglomerates being filled with an active material comprising at least one alkaline earth oxide.
Claim 2
Dependent Claim
83 words
A thermionic cathode comprising: a porous matrix of an alloy of at least one noble metal of the platinum group with a refractory metal of the group consisting of tungsten, molybdenum and alloys of these, porous agglomerates dispersed in said matrix having dimensions large compared to the components of said matrix, said agglomerates being composed of one of said refractory metals, and the pores of said matrix and said agglomerates being filled with an active material comprising at least one alkaline earth oxide.
Claim 3
Dependent Claim
13 words
The cathode of claim 1 wherein said active material further comprises aluminum oxide.
Claim 4
Dependent Claim
12 words
The cathode of claim 1 wherein said platinum group metal is iridium.
Claim 5
Dependent Claim
11 words
The cathode of claim 1 wherein said refractory metal is tungsten.
Claim 6
Dependent Claim
14 words
The cathode of claim 1 further comprising a smooth surface adapted for electron emission.
Claim 7
Dependent Claim
25 words
The cathode of claim 5 further comprising a uniform, homogeneous layer on said smooth surface, said layer comprising said noble metal and said refractory metal.
Claim 8
Dependent Claim
19 words
The cathode of claim 6 wherein the composition of said layer is approximately the average composition of said matrix.
Claim 9
Dependent Claim
12 words
The cathode of claim 1 further comprising means for supporting said cathode.
Claim 10
Dependent Claim
22 words
The cathode of claim 1 further comprising means for heating said cathode to a temperature of about 1000° C. to 1100° C.
Claim 11
Dependent Claim
111 words
A process for manufacturing a thermionic cathode comprising the steps of: forming a porous body by sintering together particles of a refractory metal of the group consisting of tungsten, molybdenum and alloys of these, mechanically breaking down said porous body into fines and agglomerates, said agglomerates being large compared to said particles, mixing said agglomerates with particles, of dimensions small compared to said agglomerates, said particles containing at least one noble metal of the group consisting of iridium, rhenium, ruthenium and osmium, compressing said mixture, sintering said mixture to adhere said particles and said agglomerates into a porous mass, impregnating said mass with a molten oxide comprising an alkaline earth oxide.
Claim 12
Dependent Claim
111 words
A process for manufacturing a thermionic cathode comprising the steps of: forming a porous body by sintering together particles of a refractory metal of the group consisting of tungsten, molybdenum and alloys of these, mechanically breaking down said porous body into fines and agglomerates, said agglomerates being large compared to said particles, mixing said agglomerates with particles, of dimensions small compared to said agglomerates, said particles containing at least one noble metal of the group consisting of iridium, rhenium, ruthenium and osmium, compressing said mixture, sintering said mixture to adhere said particles and said agglomerates into a porous mass, impregnating said mass with a molten oxide comprising an alkaline earth oxide.
Claim 13
Dependent Claim
45 words
The process of claim 10 further comprising the steps, after sintering said mixture, of: impregnating said porous mass with a liquid, converting said liquid to a solid to support said porous mass, machining said mass to the shape of a desired cathode, removing said solid.
Claim 14
Dependent Claim
39 words
The process of claim 11 further comprising the steps of: machining on said cathode shape a smooth surface adapted for electron emission, depositing on said smooth surface a uniform, homogeneous layer comprising said noble metal and said refractory metal.
Claim 15
Dependent Claim
23 words
The process of claim 12 wherein the composition of said layer is approximately the average composition of said particles containing said noble metal.
Claim 16
Dependent Claim
16 words
The process of claim 11 further comprising the step of affixing said cathode to support means.
Claim 17
Dependent Claim
32 words
The process of claim 14 further comprising the step of attaching to said support means a heater near said cathode capable of heating said cathode to about 1000 to 1100 degrees Celsius.
References Cited (Backward Citations)
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| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
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| 3.5 Years (Year 4) | 1990-06-22 | 1990-12-22 | 1991-06-23 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1994-06-22 | 1994-12-22 | 1995-06-23 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1998-06-22 | 1998-12-22 | 1999-06-23 | $7700.00 | Window Closed / Lapsed |