US2479193A

US2479193A - Articulated cathode

Info

Publication number: US2479193A
Application number: US681809A
Authority: US
Inventors: William P Zabel
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1946-07-08
Filing date: 1946-07-08
Publication date: 1949-08-16
Anticipated expiration: 1966-08-16

Description

W. P. ZABEL AHTICULAIED CATHODE Filed July 8, 194

lnven bor WiLLiam P. ZaJoe L 3 WMW His A t' lrovneg,

Patented Aug. 16, 1949 a ARTIooLAi'rED ca'rnomr William-7 121 zeta; antenna-newsprint; as; J signor' to GneraIElectric (lompanx a cor ora tio'n ofNew York" Applicatibm Jun s, 1946, swat N'd. sexism 1 invention relates to electric discharge de vices; andmore' particularly to cathodes for such devices.

Among the objects and advantagesof my in- 10. claims; (c1. 250 215) of a o'falkalirie earth carh'onates which i vention are the'provi-sion or. a oathodeewhichis -by'a-- trough-shapeet applicator similar to-that disinexpensive to manufacture-is adaptable to high speedeautomatic production and" to; automatic I machine mounting-of the cathode omits supports,- ease ofappl-ication oi electron emissive ma.-

terialthereto and uniformityof the'coating of:

emissive material on the cathode, and fasterandpeasier-ptarting of an: electrical-discharge frommthe cathode, Further objects and: advan tagesof m invention: will: appear from UI'iQ'fQI- coil: 1

The stemt is -therr-sealed to the endof-a bulb- 1; therebeing -one such-stem at each end of a tubular butb in tho case of-the well-known fluo lowingvdescription of species .thereofand-from '15 toheat the coiland eause theralkaline-earth. carthe drawing.

In the drawing Fig. l is a: greatly enlargedside view showinguthe coiling-of a cathode'onamandrel in: .aceordance with my-inv ention; Fig. 2' is greatlyenlarged. side View of' a finished and; mounted cathode; and Fig 4 is an elevationob QueencLofa 'gaseous electric dischargedevice" containing such a cathode.

bQnatesto -be-bmken down to the corresponding oxidespaftenwhieh-the bulb is: filled. with-a suitablegaseous-atmosphere such as a few mill-moo ters-of argon andra few drops; of: mercury. Such an endrview ofthe coil'an'd mandrel Fig, 3' is'a 2 .fluorescentw-l ampsvare operated at -a'current' ofthe-order oiloom-illiamperes to 1 /z amperes with the-order of i0 micronss When-the lamp isto be operated inyaninstantstartinacircuit, thatis The cathode comprising my invention-maybe lwithout-preheatinythe--cathodes,- the-- cathodes referred to as an articulatedcathode composedofia jointed: or "chain-like series of spaced helically coiled segments or bodyv'section-s connected togetherby open pitch windings of 'the' material being; coiled. The segments and spaces or gaps-- are -usually short in relation-to total cathode length. r I

Referring to Fig, Y 1, i the species illustrated therein comprises three parallelv tungsten- Wires l-. continuously coiledraroundaa: pair of parallel steel mandrels 2 in short segments-3 which are spaced apart. by spaces or gaps 4 -consistingiofan open pitch turn of the Wires 1. The continuous coil isthenvheat-treated to setthewires l; after-which it severed through certain of: the-gaps 4 to fo rm individual-cathodes composed of a desired numberof segments 4 which is at least four but preferably six or eight or more.

The mandrels 2 are-then dissolved in asuitablei-acid-isolution, whereupon there is a recoil of the turns/to a sortof corkscrew or-spiral fluted-= I outl-ineasr illustrated in-Figs. 3 and 4. After another heat treatment tocompletely: removestrains and (clean the iwire, ;the coil :is mounted in lead-inwires 5 extending fromva eonventionat stem 6, after which. the said leads-Sareseparated to-stretchethe-coilato provide a spacing of about one milrbetween adjacentrturns oithe outer wires.- 1 lathe group; wires may be-shuntedin -any suitable manner, as by twisting-the leads-togethenoutsiderthe loulb 1.

3 w wt ei le-s he se 9 hi' theitypedescribedpbove "for a; 40 watt fluorescent lamp each oi the segments 3 consisted of'ten turns of-threeparallek-13 {nil tungsten wires in= atband continuously coiled close-;together over two: paraliel -1, 5 :milesteel;mandrels the segments being- -about 1 urin. Eight of theses'eg- :ments separated-by 3/ mmi. gap 4, constituted a cathode; I-hesuspension of emissive material was applied to the sixe segments; between the-- 1eads=5 and didnotyflewbyecapillaryaction past the end gaps-4; adiacentthe clamped segments, 40 "This highly desirable becausa any emissive materiaLdeposited/on the leads cannot be pr operly activated upcn subsequent passages of c-ur-' I rent through-the cathodes.

It;-is-to advantage to providea multiplicity of segments 3 In -automatic;machine-mounting it is possible-mat ix} some gases the eon-ma be clamped at the endeapfiinside theend-mostsegment 3-,;butwitlua sufiicient number ofsegments the-electrical characteristics-oithe cathode 'will byelampine. the outermost segments in hooks -5o=:notbetoo greatly afiect ed and the nextto the last-pap l 'willethen-act as- 'a barrier to travel of the emission mixture toward the lead wire" Thus, for example-,ebwdoubli-ng tha-numberoi :spacesand-segmentsedescribed abovesit will be assured that regardless of where the ends of the cathode are clamped (within the limits of accuracy of the ordinary machine) there will be a space of mm. to mm. away from each lead to stop the flow of emission mixture into the lead wire clamps. Intermediate spaces provide easy entrance of the emission material into the segments without plugging them or the spaces therebetween when the consistency of the mixture is correctly adjusted.

In a variation of the structure described above, I have made articulated cathodes with seven tungsten wires of one mil diameter wound side by side simultaneously in bands or segments approximately 1.4 mm. wide separated by /2 mm. spaces. Some of these septet cathodes were wound on two 15 mil steel mandrels, and others on two 21 mil mandrels. In other cases three, four and five multiple wire windings in articulated arrangement were made from 1.5 mil wire wound on two mil mandrels with segments and spaces similar in length to those of the septet cathodes.

Among the advantages to be expected of the articulated cathode structure are faster and easier starting of the electric discharge therefrom than from a single long-body segment. In starting, a glow first appears at the exterior of the cathode and then shifts to the interior of the cathode. It is desirable that the shift be made very rapidly. It is known that ordinary cathodes composed of a single long segment give hard starting when the ends are plugged with emission material because the glow cannot readily enter until that material has been hollowed out at one end or the other. It therefore may be concluded that the greater the number of openings present the better chance the glow has to choose for its entrance the most favorably located and activated segment. For instance, in a sixteen segment articulated cathode at least twenty-four ends will be available on twelve segments as compared With two ends on one long segment.

Other advantages include the following. Faster coiling with increased number of spaces and reduced cost of cathodes due to reduction of the amount of tungsten wire needed and increased machine output. Universal adaptation of the same cathode design to lamps or other discharge devices of difierent rating by simply cutting ofi the desired length for proper number of segments. Good axial alignment of multiple windings because of different reactions or recoil cation on the mounting machine with respect to end segments is unnecessary if segments are very short. Quick drying of emission material and good distribution of the same within short segments. Thorough and fast degassing of the cathode during lamp exhaust because of the many short open end cylinders from which gas may escape without interference. More uniform heating and activation of cathodes during exhaust.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A cathode for electric discharge devices '4 comprising a helical wire coil composed of a multiplicity of relatively short closely coiled segments of at least several turns of wire spaced apart by open pitch sections and a coating of electron emissive material on and within said segments, the spaces between segments being open and unbridged by said coating material.

2. A cathode for electric discharge devices comprising a helical coil of a plurality of parallel wires composed of a multiplicity of relatively short closely coiled segments of at least several turns of wire spaced apart by open pitch sections and a coating of electron emissive material on and within said segments, the spaces between segments being open and unbridged by said coating material.

3. A cathode for electric discharge devices comprising a helical wire coil composed of a multiplicity of relatively short closely coiled segments of at least several turns of wire of oval cross section spaced apart by open pitch sections and having a spiral fluted contour and being coated with electron emissive material.

4. A cathode for electric discharge devices comprising a helical coil of a plurality of parallel f wires composed of a multiplicity of relatively short closely coiled segments of at least several turns of wire of oval cross section spaced apart by open pitch sections and having a spiral fluted contour and being coated with electron emissive material.

5. A cathode for electric discharge devices comprising a singly coiled wire helix composed of a multiplicity of relatively short closely coiled V segments of at least several turns of wire spaced apart by open pitch sections and a coating of electron emissive material on and within said segments, the spaces between segments being sections and a coating of electron emissive material on and within said segments, the spaces between segments being open and unbridged by said coating material.

7. A cathode comprising a helical wire coil composed of a multiplicity of relatively short closely coiled segments of at least several turns ments being open and unbridged by said coating material, the individual turns in said segments being spaced apart a distance of the order of a mil 8. A cathode comprising a helical coil of a plu- 1 rality of parallel wires composed of a multiplicity of relatively short closely coiled segments of at least several turns of wire spaced apart by open pitch sections and a coating of electron emissive material on and within said segments, the spaces between segments being open and unbridged by said coating material, the individual turns in said segments being spaced apart a distance of the order of a mil.

9. A cathode comprising a helical coil of a plurality of parallel wires composed of a multiplicity of relatively short closely coiled segments of at 5 least several turns of wire of oval cross section spaced apart by open pitch sections and a coating of electron emissive material on and within said segments, the spaces between segments beingopen and. unbridged by said coating material, the REFERENCES CITED individual turns m said segments being spaced apartadistance of th rd of i1 The following references are of record in the 10. A cathode for electric discharge devices file of this patent: comprising a linear helical wire coil composed of 5 a multiplicity of relatively short closely coiled UNITED STATES PATENTS segments of at least several turns of Wire spaced Numbal' Name Date apart by open pitch sections and a coating of ,5 5 Lely, Jr. Nov. 3, 1925 electron emissive material on and within said 4 Davies July 9, 1935 segments, the spaces between segments being 10 ,30 ,559 Pearson Dec. 29, 1942 open and unbridged by said coating material. 2, 05 Zabel Mar. 13, 1945 WILLIAM P. ZABEL.