US2526559A - Electric discharge lamp and circuit therefor - Google Patents

Description

1950 F. a. A. HAEGELE 5 5 ELECTRIC DISCHARGE LAMP AND CIRCUIT THEREFOR Filed Jan. 20, 1948 Inventor A llorneys A invention, relates charge-lamps-cf the type comprising a pair'oi main operating electrodes thermionically acti- .vated 'andmeans for initiatinga discharge between them; as or-example in -a low pressure discharge, lamp of 1 the. type containing-a fluores- ..centsuhstance excited-by the radiation from the jdischarge. When; such lamps arez'adapte'd for use in circuit with the mains voltages in common use 'in thiscountry, viz. 200/250 'v.; at 50 cycles per second. it-.is usualwtoprovide special switching {arrangements which enable a starting circuit to function until the cathodes have -reachedeinissive temperature whereupon a circuit interruption causes the lamp-tofstrikefi;

w l mo the following description Ioif one embodiment- 4 om n-:1 I

2,526,559 H H c ELECTRIC DISCHARGE-LAMP Auucmcurr ..rnnnrzron I 1 Frederick G. A. Haegelc, Westclifl-on-Sca, Eng

'. land,.assignor to Ekco-Ensign Electric Limited,

,fSouthcnd-on-Sca, England Application January 20, 1948, Serial No. 3,316 I In GrcatBritain November 23, 1945 v v I It has heretobefore: been proposedtodispense with such starting arrangementsby theemploymerit of cathodes which are self-starting."

' "A'fea'ture' of the present invention. is a discharge lamp. havinga cathode at each: end of. the

cornp rising.a core of electrically conductive refractory material ;-,l;ia vingi incorporatedJIn it :a

j thermionically activematerial, on which core are mounted two spaced apart wires, one;end of each wire beingtaken to a terminal at. that end of the lamp, thearrangement.beingi'suchethat the lampjis adapted tobecpnnected so that one-lamp terminal at [each end -thereof..may be connected to., a' source- 017 electric. supply iniseriesnwith a [suitable impedance ,(e, g. choke) whilst5the other two lamp. terminals araccnnected thl'Ollg'hia cur"- rent limiting-device, the construction of the'cathodes being. such that on connection sto the supply source. small isolated areas on the} cathodes are "broughtftoan'emissive state by current passing betweenleach pair oflthe spaced apart core wires "through .points j r wm n on their respective cores, the circuit of this -=currentbeing shunted by the ielativlyldw resistance dischargepath whnfthe lamp] strikes.

rne terni'flndof. ttias used-in it ordi nary significance 1 when the. lamp; is tubular but the invention. may be used inlampsmf eother sl ape, for; instarig're spherical and in such a case,

as is usual. .l dpf. the lampiyis meant that mnd th i a ti a edmqamnen t r t e dis-: charge'path." I

The above and, other features of the invention adilyuiiderstood by a. perusal: of

" 2' Figure 21sesefspeduve'view aiidri'giir's' mu trates a circuit in which the lamp may be used.

time electric disr GClaims. (cure-12s)" The drawings are diagrammatic, lligures 1 and 2 being to an enlarged scale. In Figuresl and 2 a cathode comprises a core a of. refractory metal.

highly porous with a rough surface having a high electrical conductivity in. the coldlstate and which contains a suitable thermionicallyactive material which is incorporated feither during or after fabrication from coarse refractory metal Powder. For instance, I the refractory powder may be of tungsten and'the thermionically'active I material be'barium oxide. "Ihecomposite, core may be made by compressing a mixture of the tungsten andbarium oxide with or'w'ithout a.

" removable binder, e. g. paraflln wax. The manufacture of cores of this nature is well known in the art and further description is considered unnecessary. This core is held'in two interwound helices b and c each composed of a wire over-' wound with another wire d so that'thissecond wired forms projections on the surface'iof the helices which make contact at isolated points with the core. All the"wiresarepreferably of tung sten. The interwound helices are not in 'electri cal connection, except through the core, andare mounted'rigidly on the lamp-toot so that the core is retained within them'but is not clampedtightly. "one helix, say I), has one end connectedto one wterminal of the lamp and 'theoth'er 'he'lixlc has one end connected to another termin'a'l'di' the lamp at the same 'end there'of'; Wh lst the other :wends of the helices have no electrical connection betweentthem'except'through the core.

@In1Figure 3 onehelix ofeach cathode .is joined Kw one'helix' ofthe cathode at the fother endof --thex discharge tube; byway of a. resistance e"'or =1 other-impedance of a few thousand ohms in value.

Theremalningtwo helices are connectedtothe 1 mains supply AC in series with a stabilizing linpedancef for thearc in the customary mann'er.

' ducting metallic strip 'depositedonthe tube wall An auxiliary electrode 'g in the'i'ormof a conand-rieither connected to one electrode heliir di- :rectly, or arranged in close spatial relationship therewith, may be used for thed ssipation of random wall icharges'whichimpede startingl zwhen current is suppliedto this circuit a 1 1ml.

tiplicity of small'arcs occur "between" the rough .1 metallic core. and the surrounding 'helices'which serve to produce" highly'activated' hot spotswhich :act:as ithe cathode spots forthe main .htion'otadischarg'ei and their-size and number can 2; 1

primary helices and, if necessary, by shaping the primary helices to present more isolated points of contact to the core, thereby raising the current density at each spot.

Due to the-means of formation of incandescent, highly emissive spots independent of the main discharge, the restarting peak at each half cycle of an A. C. discharge device will be markedly reduced, whereby an improvement in its power factor results.

The symmetrical structure of the cathode is an advantage in that the lamp may be inserted in an ordinary type of fitting without the possibility of its being connected incorrectly, e, g. the wrong way round, since the spaced apart wires of the cathodes are obviously interchangeable in function.

Various modifications may be made in the specific arrangements described without exceeding the invention.

What is claimed is:

1. In a discharge lamp a cathode at each end of the discharge path each cathode comprising a core of electrically conductive refractory material incorporating a thermionically active material, two spaced apart wires mounted on each core, one end of each wire connected to a terminal at the corresponding end of the lamp and the other end of each said wire being free and each wire making electrical connection at isolated points with the respective core.

2. In a discharge lamp a cathode at each end of the discharge path each cathode comprising a core of electrically conductive refractory material incorporating a thermionically active material, two helical wires interwound on each core, one end of each wire connected to a terminal at the corresponding end of the lamp and the other end of each said wire being free and each of said wires being separately overwound with a conducting wire making isolated points of contact with the respective core.

3. In a. discharge lamp a cathode at each end of the discharge path each cathode comprising a refractory core of high porosity with a rough surface and of high electrical conductivity in a cold state and incorporating thermionically active material, two helical wires interwound on each core, one end of each wire connected to a terminal at the corresponding end of the lamp and the other end of each said wire being free and each of said wires being separately overwound with a conductin wire making isolated points of contact with the respective core.

4. In a discharge lamp a cathode at each end of the discharge path, each cathode comprising a core of cylindrical shape with protuberances formed upon it and consisting of electrically conductive refractory material incorporating a thermionically active material, two spaced apart wires wound on each core making contact with said protuberances, one end of each wire being connected to a terminal at the corresponding end of the lamp and the other end of each said wire being free.

5. In a discharge lamp a cathode at each end of the discharge path, said cathode comprising a circular cylindrical core of electrically conductive refractory material incorporating a thermionically active material, two separate and intermeshcd wire coils non-clrcular in cross-section mounted on each core and makin isolated points of contact therewith, one end of each wire being connected to a terminal at the corresponding end of the lamp and the other end of each said wire being free.

6. In a discharge lamp a cathode at each end of the discharge path, each cathode comprising a core of cylindrical shape non-circular in cross section and consistin of electrically conductive refractory material incorporating a thermlonically active material, two separate and intermeshed wire coils circular in cross-section mounted on each core and making isolated points of contact therewith, one end of each wire being connected to a terminal at the corresponding end of the lamp and the other end of each said wire being free.

F. G. A. HAEGELE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS.

Francis Oct. 8,

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