Electric lamp and discharge devices – Electrode and shield structures – Filament or resistance heated electrodes
Patent
1981-10-02
1984-04-17
Chatmon, Saxfield
Electric lamp and discharge devices
Electrode and shield structures
Filament or resistance heated electrodes
313341, 313343, H01J 114, H01J 1906, H01K 114
Patent
active
044437358
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to vacuum devices, and more particularly to directly heated meshed cathodes for electronic tubes and to methods of making.
DESCRIPTION OF THE PRIOR ART
Directly heated tubular meshed cathodes provide for a large current capability, due to their extensive working area, as compared to directly heated rod cathodes. The existing meshed cathode designs, however, suffer from a number of disadvantages that limit their practical application. The main problems with these cathodes include difficulties in providing uniform emission over the entire working surface, i.e. high cathode efficiency, a long life and cathode parameter stability, as well as technologically effective designs.
Known in the art is a directly heated meshed cathode with a cylindrical meshed structure of the working surface formed by intersecting helical filaments /cf. FRG Pat. No. 851832, 1950/. In this cathode, all the filaments are welded together at intersection points, the ends of the filaments being welded to current-supplying rings.
The method of making such a cathode resides in winding the wire around the cylindrical surface in two directions, welding the wires together at intersections, and welding the wire ends to the current-supplying rings /cf. USSR Inventor's Certificate No. 24491, of 1929/.
The wire meshed cathodes fail to provide a sufficient mechanical strength because of the large number of welds, and besides, uniform heating temperature distribution cannot be obtained. The filament ends welded to the current-supplying rings are colder than the central region of the filaments due to a considerable heat dissipation. Further, the multiple welds cause discontinuities along each filament thus preventing temperature equalization over the entire working surface of the cathode. Nonuniform distribution of temperature over the working surface of the cathode results in turn in a nonuniform emission current. Moreover, in such a cathode, the mutually intersecting wires are differntly spaced from the cathode axis (in two layers). Therefore, it sets a limit on minimizing the grid-to-cathode spacing. As a result, the possibilities of increasing the tube transconductance are limited for the wire cathodes. The manufacturing process of winding the wire with multiple welds is both complicated and low-efficient. Owing to the nonuniform temperature distribution, the low mechanical strength, and the structural discontinuities induced by welding, such cathodes are not practicable enough and have a short life.
There is also known a directly heated meshed cathode for electronic tubes as disclosed in the USSR Inventor's Certificate No. 260748 published in 1968, which serves as a prototype of the present invention. This cathode is made of one metal piece in the form of a hollow cylinder with current-supplying rings provided at its ends, the working surface being confined between the rings and represented by intersecting helical filaments with holes therebetween.
Such a cathode has a higher mechanical strength and manufacturing efficiency than the wire cathode. The efficiency of this cathode is also superior to that of the welded wire cathode. One-piece configuration of the cathode (made of a single pipe) enables the grid and cathode of such a tube to be more closely spaced and a uniform grid-cathode spacing to be provided throughout the entire working surface of the cathode, resulting in a higher transconductance and a wider frequency band of the tube. The cathode may be formed with a varying size of holes between the filaments, so that the area of the holes of each annular row is less than that of the subsequent annular row going in a direction from the periphery of the cathode to the centre thereof. In this case, the total surface area of the filaments in the central region of the cathode is found to be smaller than the area near the current-supplying rings, this difference resulting in some equalization of the emission current density over the cathode surface.
Despite the aforementioned advantageous
REFERENCES:
patent: 2468736 (1949-05-01), Butler
patent: 2882436 (1959-04-01), Dorgelo
patent: 3449616 (1969-06-01), Sarrois
patent: 3473073 (1969-10-01), Gerlach
patent: 3806753 (1974-04-01), Van Warmerdam
patent: 3875445 (1975-04-01), Bachmann et al.
patent: 3943398 (1976-03-01), Gerlach
patent: 4144473 (1979-03-01), Almer
patent: 4230968 (1980-10-01), Oguro
Alexandrov Vladimir N.
Filatov Oleg V.
Ioffe Vladimir F.
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