US1814270A - Glow discharge device - Google Patents

Description

July 14, 1931. c. TRAVIS GLOW DISCHARGE DEVICE Filed Jan. 17, 1928 4 Sheets-Sheet. 1

July 14, 1931. TRAVIS 1,814,270

GLOW'DISC-HARGE DEVICE Filed Jan. 17, 1928 4 Sheets-Sheet, 2

JuTy 14, 1931.

c. TRAVIS 1,814,270

GLOW DIS CHARGE DEVI CE Filed Jan.. 17, 1928 4 Sheets-Sheet, 3

July 14, 1931. c. TRAVIS GLOW DISCHARGE DEVICE Filed Jan. 17, 1928 4 Sheets-Sheet, 4

Patented July 14, 1931 UNITED STATES PATENT OFFICE CHARLES TRAVIS, OF PHILADELPHIA, PENNSYLVANIA, ASSIGNOR TO ATWATER KENT MANUFACTURING COMPANY, OF PHILADELPHIA, PENNSYLVANIA, A CORPORATION GLOW DISCHARGE DEVICE My invention relates to asymmetrical conductors of the gaseous discharge type utilizable for any suitable purpose and particularly for procuring from an alternating our- 5 rent a substantially uni-directional current a suitable to be employed for any suitable purpose including that of energizing the electrode and particularly the anode or plate circuits of thermionic tubes.

In accordance with my invention, electrodes of a rectifier tube of the point-plane type are comprised of elements of such form and disposition that the rectified voltage supplied by the tube and its power output per unit of active anode surface attain orders of .magnitude not hithertofore realized, more particularly the cathode structure comprises two foraminous tubular members. disposed one within the other about an anode and" more specifically, either and. preferably'both cathode members are formed by a helix of wire of small cross-sectional diameter or radius of curvature.

Also in accordance with my invention, within a tube of the character above described, there are disposed members, as for example, electrodes, or parts of electrodes, and specifically cathodes, of metals, pref erably molybdenum and tantalum, having different gas-occludent properties cont1nually to maintain gas within the tube in a state of high purity. More specifically, the

cathode is comprised of a molybdenum member heated in hydrogen substantially at atmospheric pressure, and to which is subsequently afiixed a member, as a loopor ring, of tantalum; preferably, the cathode after assembly is disposed within the envelope of the tube and heated in a high vacuum.

bodying my invention.

My iiivention further'resides in features.

Fig. 1a is a horizontal sectional view, parts in plan, taken on the line la-1a of Fig. 1.

Fig. 2 is a vertical elevational view, partly in section, of a modified structure.

Fig. 2a is a horizontal sectional view, parts 5: 111 plan, taken on the line Qua-2a of F ig; 2.

Fig. 2b is a horizontal sectional view, parts in plan, of a modified cathode-structure support.' i

Fig. 3 to 8 inclusive are fragmentary elevational views, partly in section, of modified electrode structures.

Figs. 3a to So are plan views of the structurcs shown in Figs. 3 to 8 respectively.

ig. 9 is a diagram of one of the various electric circuit arrangements in which a form of my gaseous discharge tube is utilizable.

Referring to Figs. 1 and 1a, 1 isthe base of "a tube or bulb Bof glass or the like having the usual tubular stem 2 and press 3, of glass l or equivalent.

Secured to or sealed in the press 3 are upstanding supports, wires or rods 4,. at least one of which isconnected as by a conductor 5 to a contact tip 6 disposed exteriorly of the 7! bulb B and preferably, as shown, secured to the bottom face of the base 1 to engage a contact memberof a suitable receptacle or socket, not shown. The cathode member C comprises numerous elementsof fine wire 7 of molybdenum, tantalum, tungsten, nickel or other suitable material, but preferably molybdenum, rangin in diameter from about .006 to .015 inch, e 'ecting small radius of curvature of its surface for effecting high electron emission.

The wire 7 is disposed, in the example il-. lustrated, in the form of a. helix, all or any suitable number of convolutions of which are s r s y e ng, 17 supports, Semi-ice are secured I at one; end; preferably-thelower end, to main support members 4, and "a the other end.

, preferably to a cross support or brace member 9 secured, as by welding, to the upper, or free ends'of the main support ro s 4. 1

" The wires or-main supportrods L ars'pr f of the order of .025 inch. Preferably, and as shown, the main support or sustaining wires or rods 1, at their lower ends have a portion extending at a substantial angle intermediate the vertically upstanding portion of the rod and the point at which it is sealed in the press 3 to permit longitudinal expansion of the support and thus prevent appreciable distortion or displacement of the cathode elements 7 which would otherwise occur due to the high and varying temperatures to which the structures are subjected during construction and operation of the tube. Similarly and for like purpose the supports 8 to which the cathode member is directly secured is bent at its lower end for attachment, as by welding, to the main support rods at and at its upper end is secured to the support 9 at a point spaced from that at which the latter is secured to the main support Also secured to the press 3 are the upstanding rods or wires 10, at least one of which is connected as by a conductor 11 to av contact tip 12 suitably secured in the base 1 and extending exteriorly thereof for engagement by contact structure of a suitable socket, not shown. The electrode or cathode member C1 comprises numerous elements of fine wire 13 of tantalum, tungsten, molybdenum, nickle or other suitable material, but preferably molybdenum, ranging in diameter from about .003 to .010 inch, effecting small radius of curvature of its surface for effecting high electron emission.

To facilitate manufacture, the portion of the support 10 to which the elements are fastened, as by welding, is welded or otheiwvise intimately secured to the lower portion sealed in press 3.

The wire 13 is disposed, in the example illustrated, in the form of a helix, all or any suitable number of convolutions of which are secured, as by welding, to the supports 10. the support being essential or at least practically desirable because of the fineness of wire 13.

Preferably, and as shown, the diameter of wire 13 is less than that of wire 7 and the turns of helical cathode member C1 are more closely spaced than those comprising the electrode member C.

Adjacent the press or seal 3 the anode 14 is surrounded by a tube 15 of refractory insulating material, as lava, lavite, soapstone, or equivalent. emerging from the press 3 and having a coefficient of thermal expansion substantially equal to or differin but slightly from that of the material 0 the press 3. WVithin the tube 15 and exteriorly of the press 3 the anode 14 is welded at 1V to a conductor 16 extending to and in electrical engagement with a contact tip 17 which may be secured to the base 1. The lead-in conductor or wire 16 is of ordinarily such diameter and ductility that it would not suitably the form of a ring such as the loop support anode 14. As shown. the bore of the refractory tube 15 is sufficiently small to permit the anode to be supported at least in part and maintained in proper position by the tube. By securing and supporting the anode in the manner described. there is little or no danger of cracking the press 3 by expansion and contraction of the anode 14.

The anode may be of tantalum wire having a diameter of from about .015 to .03 inch, but preferably .02 inch. It may project roughly about fi inch above the top of the refractory sleeve 15, in which case the inner cathode member C1 may be roughly 1 inch long and disposed to extend above and below the exposed portion of the cathode, and the outer cathode member C may be. roughly 7;, inch long. It is to be understood that the length of either or both electrode cathode members C andCl can be increased, although but little additional output is gained thereby. The length may-be decreased with, however, appreciable decrease in efliciency of the tube. For the dimensions given, the diameter of the inner cathode member may be approximately .2 inch and that of the outer cathode member about .3 inch. It is understood that the dimensions given above and throughout the specification are used in an illustrative and not a. restricted sense, and that when suitable or desirable may be modified.

The support wires 4, 8, 9 and 10 may be of suitable material, such as that of wire 6. but preferably of nickel. hen the cathode members are of molybdenum, as above described, it is in some instances desirable that one of the support members be of tantalum, since the presence of these two metals having different occludent properties by. selective clean-up action continually maintains a state of high purity of the gas within the bulb B, which is or may be a pure monatomic gas or vapor as neon, argon, but preferably helium at an absolute pressure from about 5 to 50 mm. of mercury, preferably about 24 mm. of mercury. It is more convenient, however, to make the tantalum member in or ring 18 disposed at one end, preferably the upper end of a cathode member, as, for example, the outer cathode C of Fig. 1, and secured to the supports thereof. as rods 8, in any suitable manner. as by welding, after de-gassing ofthe molybdenum cathode by heating in hydrogen, which may be substantially at atmospheric pressure. The assembled cathode with the tantalum attached thereto is disposed within the tube envelope B and heated, as by induction, in a substantially high vacuum.

There may be provided a stem member 19, as of glass, projecting upwardly from the press 3 whose exterior diameter is sufficientwelding to the top cross support or anode member '14 ly. greatto' position .and support the inner electrodemember CL.

ber C posit' and-a-resistance, of desirable sta-ntially limits the notwithstanding variations of load and fluctuation ofthe source. of supply-.1; Aisystem utilizing a-gaseous discharge tube construct ed in accordance with my invention and havmg a resistance whose disposition identified is disclosed and-described in co-' pending application Serial 0. 225,469,v filed.

October l1,v 1927.

-,By effecting direct electrical contact be? tween contact tips 12'an'd'l7, as by use of a common socket contact spring, not shown, and by connecting the discharge tube in the usual manner, i. e., in series in a circuit including a source of alternating or fluctuating current and devices adapted to be operated by direct current, the device operates as a half-wave rectifierwhereby unidirectional current impulses flow in the circuit. Due to the construction of the cathode, as above described, the efliciency of the rectifier is increased without decrease of life and in addition the potential, at which there occurs ionization o: gas Within the tube necessary to effect starting thereof, is lowered. Furthermore, and contributing to the increase of efficiency, the drop of potential within the tube is substantially decreased.

Fig.2 of the drawing illustrates a Wave rectifier having features of constriictibnin common with the gaseous discharge tube of Fig. 1. In this modification the lower ends of the support wires 8'- holding the outer cathode member C aresecured as by weldin to inwardly extending supports ably of reduced cross section,

g 8", preferand welded to .the verticalportion of the main support rods he supporting rods or wires 10 for the inner cathode member C1 are seemed as by brace member 9 at points substantially distant from those at which the brace member is welded to the main ends of the inner cathode member supports "10 are bent outwardly at a substantial angle and welded at or near their'en'ds to main support rods or wires As in Fig. 1 the supporting frame work for the cathode members is constructed to permit relative longitudinal expansion of the separate elements compris-.

mg the frame work without appreciable distortion or displacement of the cathode elements carried thereby. To permit of full wave rectification there is provided a second constructed, supported,

sitlon and constant Within unusually narrow .voltage between the conductors as abovev supports 4. The lower and arranged spbstantially as above described with respect to anode 14 of Fig. l. The upwardly extending glass stein members 19 and 19''. disposed, respectively, about the refractory lavite tubes 15 and 15 may be of such diameter and'so' .disposed as to posupportthe inner electrode memberCl which may be, as is most clearly shown in Figs. 2 and 2a, a single conductorwound in the form of a helix and whose individual convolutions, when viewed in plan, are in the form oftwo substantially completed circles j oined at j'acent discoi'itinuities of their respectiveperipheries. The outer, cathode member (.1 may also be a single conductor wound in theform of a. helix whose individual convolutions, as shown in Fig. 2a, are, in eli'ect, two semi-circles, the opposite and adjacent ends of whichare joined by parallel and integral members the centers of curvature of the curved portions of both cathode members (J andlOl is preferably atthc anodes 1i and 1 4 whereby the cathode members or a substantial portion of them aresynnuetricallydisposed about the anode struct uresto efi'ect more even" distribution of the glow discharge.-

In Fig. 2b, .the tubes 15 lavite,,or the like, are each provided with a stiffening shoulder engaging the press 3 and a portion of. .enlarged diameter and support inner electrode Cll street-ion is particularly of advantage when caesium is utilized as an ionizing agent, as the presence of heated glass, as stems l9- and l9 stroys itseificacy. I H v. V

The cathode structure of Figs. 3 and 3a and 15 reduces or deto the disclo- 4, as in the modificationof Fig. 2-. W ithsuch' to position This conglass, especially leadupper ends to the cross support rod 9 and at their lower ends bent... ,o'utwardly to the mam support rods or wires of lava,

construction thesupport wi res 10 for; the in;

ner cathode n'u ybe of the same or approxi mately the same'diameter as that of the rods 8 whichsupport the outer cathode member C.

eferr ng to Fig. 4, the outer cathode C. is comprised'of two separate helixes whose individual convolutioiis are circular andsynu metrically l4 and 14.

The, support rodent? are secured 12') disposed with respect totheanodes v as bywelding to all or. suite. {number of the convolutimis of each hell-X at opposite {sides of thehelixcs and preferably intheir t l1je.sup-- secured to the croj's. strip.

line of centers. The ports are suitably 9 and at theiri lower .ends to the main su port rods 4. The auxiliary support rods 20, 20 for the cathode assembly C. are securedto.

upper ends. of

60 ode member the respective helixcs at of closest approach and jacent ends as disclo"ed. structure C1 consists of two helixes disposed about the'anodes and within the corresponding helix of the outer cathode-member C Each i nerhelix is supported by a rod or wire 2 or near theirpoint to each other at adsuitably secured thereto and whoseupper and lower ends are welded to the ore s support 9 and the outer cathode support 8,- respectively. further braced and supported by the depending'rods or wires 22 Welded at their upper endsto the cross support 9 and intermediate 'f- 'i-u circles .havingtheir centers in the same of which are of strai ht line, the outer two relatively large diameter and symmetrically disposed with respect to the anodes 14 and 1e and the inner. one of whichis formed by 30 bending the, wire comprising the turn about the central 'main support rod sealed at its lower end within the press 3 and at its upper end suitably secure to the cross sup ort rod 9. The inner cathode i lilmemben as in ig. 4, consists-of two separate coils or helixes. The depending members 23 of rod or wire are secure to the cross brace 9,-their loweriree end en gaging the inner-peripheries of the lass Lgdstems as above explained. H

- The constructionshown in Figs. 6 and 6a is generally similar to that disclosed omitted. I g i In the construction shown 7 a the inner 'cathodeinember similarto the construction of The inner cathode The inner cathode helixes are their length to the. convolutions of the rewithin the range of from 4a which s. is

p in Figs; 5and 5a except that-'theauxiliary main-supwas and h fie e e swam s in Figs. Tand Cl is generally 1 v the outer cath- C of Fig; 4; In this modification suitable cross s'ectionis comprehended by the" term wire, and may be polygonal, including such cross sections as-areafiorded strips or ribbons whose edges-or flat sides" may be presented to What Iclaim is: a 1. A gaseous discharge device comprising anode structure, and a cathode comprising a wire-likehelix of molybdenum and a closed loop-ottantalum.

J2. A gaseous anode structure, ing a wire-like helix whose= surfaces have radii of curvature lying within the range of from about .003 to .007 5 inch, andan electrode positioned between said anode and cathode structures and comprising a'wire-like helix whose "surfaces have radii of curvaturelying the c -acting anode.

inch;

at their upper ends 19, 19 to properly position the he 'xes i the outer cathode stru'ctureG-yis similar to ,that oftheiinner'cathode member 0 s indicated in Figs. Sand 80, the cathode 55 members C and C1 may'each comprise lar member of screening, the mesh atubuy of theinner cathode member preferably being finer than'that of the outer cathode member; 1 It is to be understood that the number, v.5 and shape of the cathode elements or their equivalent. may be varied without departing 4 from't'he spirit of my invention. Further-g n" while cathode elements are 11 be understood that any other shown and de scribed aswire of substantially circular cross; section, sh

; CHARLES TRAVIS.

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7t discharge device comprising cathode structure compris- I about .0015 to .005

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