US2118000A - Gaseous electric discharge system - Google Patents

Description

May 17, 1938.

H, WOJTKOWIAK- GASEOUS ELECTRIC DISCHARGE SYSTEM Original Filed Jan/'7, 1936 IN'VENTOR Ha s Wojtkowz'ale TORNEY.

am, it f ensuous aisc'rmc m scnaaoa srs'ram wousowiaawechswkm, n. 1.. ulignor to lamina-Electric,

January I,- 1938.

This invention relatesto gaseous electric dis- I tion is concerned is one including electrode means 7 in the form of letters or other indicia. for examp1e--entire words, about which the glow-light is maintained to produce the eflect oi'glow of the indicia themselves. I

This application is filed in substitution .for my co-pending application Serial No. 57,885, illed January 7, I936, andherewith abandoned.

It is an object of" my invention to provide a v 15 device'and system of the class described which will produce bright glow-light about the electrodes without'distracting light in the positive column between'the electrodes.

and device satisfactorily operable with reasonable 4 supply voltages.

It is another object to maintain the glow-light essentially uniform over the entire indicia surface. 2.5 f

trode disintegration in such a device, particularly withoutimpeding the fulfilment of other objects I ing comprising a monatomic gas component and of the invention.

It is another object of my invention to provide such a device wherein electrode meanadistributedin the form oi entire words or the like,

are arranged in animproved manner to provide uniform'glow-light, and at the same time unimpeded visibility and absence of electrode struc- 35 ture in positions wherein its glow would distra'ct' attention from .the words or the like It is still another object to provide rugged and otherwise satisfactory spacing and rangements for the electrodes.

It is a general object to provide an improved device-cf the character abovedescribed' Other and allied objects will more fully appear from the lollowing pended'clairns- In the description reference is had companying drawing, 01 which I Figure l =is a. view generally elevational but partly in'lon'gitudinal vertical section, of a disaccording to my incharge device and system vention;

55 spacing member of the device of Figure 1;

N. 3., a corporation of New-Jo Continuation of application Serial No. 51,885,

rm, sum No. cons:

- -z'o claim, retire-124) It is a veryimportant object to mlnimizeelecs pporti a description and apto the ac-' Figure 2a is a transverse vertical cross-sec Union City,

"Russet;

Figure 3 is a cross-sectional view taken along line 8! of Figure 2a; A Figures 4a and 4b are detail elevational views or two alternative forms of spacing members-tor the electrodes; v v i Figure 5 is-a'partial elevational view of an alternative electrode arrangement, and

Figure-6 is a partial elevational and partly schematic view of a device and system illustrat-' ing still further alternative electrode arrange- 10 ments, and an associated circuit for causing intermittence of glow-light about some of the indicia. g

It will be understood that throughout the spec-. iflcation the term gaseous has been employed broadly as the adjective appropriate to one or more gases and/or one or more vapors. the term fgas to denote one or more gases; and the termvapor to denote one or more vapors;

'The various features of my invention, with their functions and advantages, are best described after an initial brief description of the general structureof' a typical discharge device in which they are co-operatively employed; such a device is illustrated in Figure 1. Herein the numeral 6 designates a transparent envelope or glass tube evacuated of air and containing a filla second component which for example may be a source of metal vapor. The monatomic gas '3 may desirably be neon with or without the ad- ;dition of helium up to say 20% of'the amount of the neon? but no particular limitationas to the rare gas is intended. As hereinafter ap-.

pears, the rare gas component preferably has a, 3

substantial pressure-e. g,., 15 to mm. Hg and preferably more than 18 mm. Hg. The second ucomponent of the'illling'may be provided by a small quantity of mercury, or of mercury with a small percentage of alkali and/or alkaline earth metal, and has been designated in Figure 1. as

8]. It will-be understood that while the source it may cling to the wall of the envelope I when cold, itis adapted to vaporize to a degree depending onthe temperature of the device, and

to develop a vapor pressure independently of the -gas pressure abovementicned.

Sealed in the'respective ends of the envelope are the stems 2 and}, respectively provided with the lead-in wires 2b and 3b, to which respec o tively are connected the electrode systems I and I hereinafter described. The lead-in .wires are externally connected to the terminals 9 of a voltage source to, which may be either alternating or direct, through appropriate current limiting .been structurally illustrated the. resistance 8!);

the structure, which has been found desirable, is hereinafter described. Also sealed in the-respective stems 2 and 3 are the respective wires 32 and I a commercially satisfactory device are many,

33; these, however, are supporting wires only, and

need not be extended or connected to exteriorly of the seal or envelope. 1' q The electrode system 4 comprises a straight wire lb welded or otherwise connected at its left extremity to the lead-in wire 2b, and extending longitudinally. ofth'e envelope lnear its wall; letters or other indicia lc disposed generally jso that their plane'includes the wire lb, and extending from near: that' wire substantially diametrically of .-the tubular envelope; and short wires'la welded both to the wire 4b and to the individual letters 40, and serving to support the latter. The electrode systenf comprises a straight wire 51; ,weldedbr otherwise connected at its'right extremity'to the lead-in wire 3b, and

extending longitudinally ofthe envelope l near i its wall and in slight spaced relation to the wire' lb; both wires 5b and 4b may extend substantially the entire length of the envelope, parallel to each' other and preferably jointly lying in a plane at right angles-to that. of the letters lc., While it may be either-in front or behind, the .Wire 5b has been shown,';by'-way of example only,

' infront of' the latter,plane-'-i. e., spaced therefrom'in the directionifrom which the letters are viewed. For mechanical support of the right extremity'ofthe wire lb and of the left extremity of wire 5b, these'respective extremities maybe 4 seal of the'respective two wires (e. g., 2b and 32) for'most complete illustrationFigure 1 has been we lded orotherwise secured to the" supporting wires 33' and 32, abovementioned. It will be understood that in a view of the'device taken pre-' 'cisely normal to the plane of the letters or indicia. 4cand wires 46 and 5b would merge into one, as-would likewise the points of passage into each taken from a" direction slightly displaced from the normal, as indicated by' the arrow in Figure 2a. The primary function of the/device is to pro-L duce about the letters or other indicia 40 a cathodic-glow-light close to the electrode surface so that the surface proper appears-to glow. The

wires 4a being short and the wire lb being preferably disposed slightly underneath the letters or indicia 4c in such a manner as' to form an underlining therefon, it is considered permissible that these wires too be surrounded by glow-light. Particularly when the device isoperated on alternating current, a glow-light will be produced about theopposite electrode systeme. g., wire 5b; one reason for the positioning of this wire as shown is to avoid its glow distracting attention from theglowing letters or indicia, its glow then simply tending to merge with the letter-,under-- lining glowabout the wire 46. Thus I have-so arranged the electrodes that the glow thereabout comprises thedesired glow together with entirely permissible glow-so avoiding the trouble of covering portions of the electrodes with glass or other'refractory material to prevent theirglowing: There will be appreciated, however, thedefinite undesirability of the production of ma- 't8ll8 1 glow orother light in the space generally within the envelope-'-i. e., positive column lightf as such light seriously detracts from the promias of ionic losses and potential gradient). also be,noted that for minimization of these losses Insofaras I am aware, a device of this general characterwell adapted for example to advertising and display purposeshas never before been produced to operate with useful commercial life and uniform glow-light intensityon the various letter or indicia surfaces, or otherwise in a satisfactory manner and with commercial supply voltages of 220 volts and less. The requirements for and must of course be satisfied jointlyin the single product; among them may be mentioned (a)-the minimization of positive column light,

I both absolutely and relatively tocathode glowlight, abovementioned; (b) the minimization of the required voltage drop across the system, so that it may properly operate on commercially available voltages; -(c) the maintenance of even light distribution during operation both between different portions of the same letter, and between the several letters; (drwthe minimization of elec-' -trode disintegration, during initial manufacture and duringafter-operati'on, in order toconserve electrode life and to minimize envelope wall discoloration; and (e) the arrangement of electrodes and their supporting-and'spacing means within the device to'insure proper'visibility of the letters or'indicia, freedom from glow in distracting positions, mechanical ruggedness and other de- -sirable characteristics, without impairing the ordinarily contributing to the creation of ionic losses, of potential gradient, and of light in a. positive columni. e., constriction of the dis,

charge column by the walls, low atomic weight of the gaseous atmosphere active in the positive column, and-high pressure and density of that atmosphere.

In my device I make negligible the constriction of'the positive column by the walls. This I am ableto do, while spreading the electrodes well throughout'the envelope interior and thus avoiding wastefully large envelopes, by the described generally parallel arrangement of the two electrodes, resulting in the positive column path beadvantages I first call attention to certain factors ing transverse rather than longitudinal of the elongated envelope. As is illustrated in Figure 1, the maximum positive column path length (or longest of the most direct paths to the electrode system 5' from points on the electrode system 4).

is shorter than the transverse envelope dimension (e. g., diameter), while the width of the positive column path is preferably many times that dimension (e. g., is substantially the length'of the envelope). Obviously as to this short, wide positive column path the walls are substantially removed. 'So I'provide a first significant factor in the minimization of positive column light (as well I It will suiiiclent current to the cathode surface to cause it to be fully surrounded by glow at normal cathode fall; at the same time it is undesirable that mental eil'ect thereof on electrode life. The nor- I pass suiliclent current to create an abnormal fall to any marked degree, became of the detrimal cathode fall is known to increase with decreasing atomic weight of the here active gaseous atmosphere (as well as with increasing work -i'unction of the cathode) while the value of ourrent appropriate tocomplete glow coverage oi the cathode'with substantially normal cathode iall increases with increasing gaseous'density. Thus, to maintain brilliant glow-light about the electrodes, it is desirable that I employ a gaseous atmosphere of relatively small atomic weight and of substantial pressure or density.

I solve the problem created by this repugnancc v of requirements between positivecolumn light and electrode glow-light by employingollch a gaseous envelope filling that under operating conditions the activelyeiiective gaseous atmosphere close to the cathode is of high density and pref-- erably lowatomic weight, while the actively effective gaseous atmosphere in the positive column is of low density andpreierably oi relatively higher atomic weight. This filling consists of a If rare gas component of approximately the desired spectrum (for example neon) at a substantial pressure; and a gaseous component lower ionization potential, and preferably of greater Just referred to the vapor pressure in the sense of the pressure during normal operation. The desired limitation of pressure may be eii'ected bv limiting the amount 01' vaporizable mercury inserted in the device.

Because of its lower ionization potential-the va or will be preferredly ionized in any s ace portion so long as a suillcient amount of the vapor there exists to enable the faster electrons,

by ionizing the vapor,.to develop ions at the required rate for that space portion. I preferably employ only suflicient or slightly more than sufflcient,'vapor pressure and density to meet the relatively low requirements for ionizahle atmosphere in the very wide path of the positive column, so that only or substantially only vapor will be there ionized, and the effective gaseous atmosphere oi. the positive column may be consldered a vapor one. The requirement for'ionizable atmosphere close to'the cathode. however. is relatively high and accordingly the limited density vapor can at best supply only a small fraction of that ionization which produces the cathodic glow light; this ionization is therefore almost entirely oi the rare gas, and the cathode glow-light characteristics are accordingly principally determined by that component. Because.

'however, of the relatively high average electronic velocity in producing the cathode glow-light this light is somewhat more' predominate in higher frequency lines of the rare gas than is the positive column light of a similar rare gas in a tube of the conventional neon sign type.

I obtain then, assuming the use of neon as a rare gas, a striking pinkish-red glow-light about the cathode, including the indicia 4c, and an ordinarily practically unobservable background,

or positive column. It is to he understood that. 75 this desirable result springs most essentially mm the joint rectors or short, wide path with removedwalls, and of extremely low v vaporpressure. I employa vapor pressure usually of the order of or less than .001 mm. Hg, and at the most of only a few thousandths mm. Hg, so that'the ratio of gas to vapor pressure is maintained well in excess 01 1,000 times, and in typical cases in excess-of 10,000.tim'es., A

Thus my device ,well meets the requirement (a) above; at the same time the very low positive column potential gradient and total drop resulting from theactively effective low density vapor atmosphere-is a large contribution to the meeting of requirement (b). v

Ihavethus far described-the desired cathode glow-light, and thegenerally undesired positive When the device is operated on alternatlng current, however, the glow-lights appear essentially similar oneach electrode system, each such light dynamically comprising an alternation of the prominent cathode glow-light and relatively faint or unobservable anode glow-light.

'With whichever current be employed, I prefer ,of course so to adjust the value of the resistances mal operation, is facilitated by maintaining the normal cathode fall at a moderate value (though of course not excessively low, otherwise the brilli'ance of the cathode glow-light will be unduly sacrificed). And while the presence of the vapor in my gaseous filllngdoes not seem strikingly to afiect'the color of the'cathode glow-light, I have found that it does have some significant action in moderating the normal cathode fall.

It is very desirable, for starting facilitation and for the obtainment of long, glow periods each half cycle without impairment of electrode life, to have. portions of the respectively opposite electrodes mutually very near each other-in the order of a few mm. apartas the wire db and the bottom portions of the letters 40 preferably are to the wire 5b. Therefore a device of this charactenwill involve great differences in discharge path length from one electrode to various portions of the other and will, so long as simple rare gas is employed, involve relatively significant potential gradient in the positive column; the positive column drop. as to different portions of the same electrode, will be very different, not merely in ratio but in absolute value. But for uniformity of glow-light development on the electrode the absolute difierences in positive column drops should be maintained at a very small fraction of the normal cathode fall, and desirably at a fraction of the anode fall (whichmight typically in a device of this character be of the, ordcr of 12 volts), .If this condition be seriously violated therewill result uneven glow-light development-or even actual absence of glow-light over large portions of the letters unless there positive column lightand voltage drop minimibe employed abnormally high current through the device and a significantly abnormal cathode fall therein. The high current density per unit electrode surface, which goes hand in hand with high total current and abnormal cathode fall, leads to rapid electrode disintegration and bad impairment of electrode life and wall discolora-.

tion, besides requiring higher supply voltages. By the introduction of just sufficient vapor density to render the positive column discharge a low pressure vapor discharge, I not only obtain the advantages above discussed in connection with zation; but also vastly reduce the difference in positive column drop asto different electrode portions. In view of the width and shortness of even the longest discharge path involved, the

absolute value of the maximum difference in positive column drop is, rendered almost negligible, and it becomes possible to obtain excellentlight uniformity without involving appreciably abnormal cathode fall, or increased current and voltage drop across the system. Thus I meet" requirement (0) without impairing compliance .with requirements (2)) and (d).

The last requirement in a device of the character under consideration is an extremely im- ,portant one,'not merely in respect of electrode life, but even more in respect of cleanliness of the envelope walls, which at almost all points are near enough to the electrodes to receive serious blackening therefrom should the latter either during normal operation or during original manufacture seriously disintegrate. important to minimize this, disintegration not only in normal use but in original manufacture and preparation for use. in my. device a conventional electrode material of pure iron or of iron alloyed with a few' per cent of nickel, these tend to require overloading with considerably abnormal cathode fall, thereby causing excessive disintegration, in these initial ing for the electrode material an'alloy of pure stages. I have found, however, that by employiron with a higher percentage than usual of nickel-say between 10% and 35%. and preferably in the range from 15% to 20%the alloy permissibly containing a few per cent of some alloying agent such as manganese and having preferably been prepared or melted in'vacuum and drawn or otherwise formed into wire or the I like within a reasonable time'thereafter, and by using mercury ions to bombard the electrode surface, I am able after a short bombardment to "cause the electrode surface to'glow evenly without having caused appreciable blackening, and thereby to put the device in condition for several thousand hours of operation free of trouble some effects.

Preferably I perform this bombardment in the following manner: After' the device has been structurally completed excepting for the introduction of the filling and final sealing off from outside air, I pump the device to a high vacuum, and introduce a little rare gas to permit'starting of a discharge, together with an appreciable quantity of mercury; I then apply voltage to the system to start some discharge, preferably having warmed the device by exposure (e. g., in a suitable oven) to an ambient temperature of 300 to 350 degrees C. to cause high vapor pressure; thus mercury ions are formed and are the principally active ions in the electrode bombardment. Somewhat-more than normal voltage is used in this procedure, in view of the now high vapor pressure.

It is obviously- While ,I may employ This bombardment may be permitted to continue for a while to insure substantial completion of effect on the electrode surface, above mentioned.

Finally, the bombardment is stopped; the device is cleared of rare gas, oxygen and other occluded gases, and of mercury; then before sealing of! there is inserted the'n'ormal rare gas filling component and mercury for normal vaporization (or sufficient of the latter may be left in at the con- Y clusion of the clearing operation). It is to be understood that the mercury vapor in the normal filling co-operates with the alloy electrodes to effect in the first several hours of normal operation a final completion of the electrode surface preparation which the special bombardment above-mentioned may not utterly complete.

It appears that the alloy surface though sufiiciently oxidized to prevent initially .a proper glow discharge, will under normal mercury ion bombardment rapidly change the structure of its defective sections and 'comeouickly to a condition of even glow. The'surfaceof the electrode ma- .terial contains a large amount of nickel, with which the mercury vapor forms an amalgam hav-' ing acathode fall distinctly lower than that of iron and of'course much lower than that of oxi-r' dized.iron. This amalgam seems to form inat least small particles closely spaced over the whole oxidizedsurface, so that glow rapidly appears over the entire electrode area; good distributionis thus obtained almost immediately and without the necessity for abnormally high cathode fall. In the course of a short time the con- .tinued' bombardment with substantially normal cathodefall will remove the oxygen 'or oxidized of serious magnitude. j g I Too much nickel in the alloy would undoubtedly raise the disintegration to a serious value,

while not enough will prevent the quick spread of the-"glow' over the whole electrode. areaprobably by rendering too great the average separation of the amalgam particles. Of course,

at least part; of the 'nickel in' the alloy might be replaced 'with some other metal adapted to form an amalgam with the mercury. It may further be mentioned that in cases wherein ex-v ceptionally low cathode fall-is desired for jpur poses of facilitating starting with very low voltages (although'ln general not otherwise) it maybe desirable ;to use one. of the alkaline earth metals, such as barium; as the amalgam-forming metal with which to replace the nickel to the extent of 1- or 2% of the total alloy.

I have thus shown the more important practices in my invention. which in co-operation cause thedevice to meet the requirements (a) (b), (c)

and (d) hereinabove mentioned. I shall -now proceed ,to a description of the further features .of my invention and of the illustrated embodi- 4b and 5b. This arrangement aids in guarding against twisting of the electrode structure, and otherwise in rendering the same rigid. Further 35 iron of the 'surfacemolecular layer, leaving the ,pure' iron and nickel: and such disintegration of the latter as occurs has not been found'at all i sum rigidness is imparted .by the central 4 ber 34, preferably of mica or other thin insulating material, which may be formed as a crescent having an outer periphery of about 225 degrees fitting the interior cross-section of the envelope 1;

the main body of the crescentis preferably dis-v posed behind the plane of the letters '40 so as to maintain visibility; the wires b and 5b pass through and are held in apertures provided in the crescent as' hereinafter more par- .ticularly described. Still further rigidness is imparted by holding the two wires 4b and Ib in their proper fixed spaced relationship at a pin tionedbelow. Rigidness of the wire 5b is further rality of intermediate points, as by .aplurality'of transverse ceramic spacers, for example of mag-. nesium oxide, aluminum oxide and/or magnesium silicate illustrated as 6 and 1 and further menaided by welding thereto andparallel therewith reinforcing wires 5a, which may be shorter pieces of wiresimilar to 5b; these are preferably welded onto the wire 511 along sections which include the points at which it is to pass through one of, the positioning members--e. g., 8, I, ll.

The advantage of plurality of shorter pieces over a single long piece is the freedom from permanent twisting tendencies which might'be imparted by slight inaccuracies of positioning of along wire be passed to and from the electrode without i,n-

while welding it to the wire 5b.

v volving abnormal cathode fall at times when that electrode 'acts as cathode-thereby. permitting suflicient discharge current to illuminate ,the in-' dieia 4c in their entirety without at the same time overloading the electrode system 5 with seriously abnormal cathodefall.

If not properly arranged, the positioning members placed along the wires 4b and it) for mechanical reasons (e. g., spacing member 34- and spacers 6 and 1) may render'portions of the dervice inoperative, 'or at least cause badly impaired life of portions of the electrodes and accompanying wall blackening. I The glow, usually starting at one end of, or some one region in, theelectrode systems when voltage is first applied across the' device, will spread only as far as the first such member and them stop. This stoppage results from the fact that the voltage required to start a' discharge is in excess of 'the normal operating voltage; as discharge is established the voltage across the-tube automatically becomes less than the starting voltage; and if the spread of cathode glow-light along immediately adjoining electrode areas (which requires only approximately normal voltage) is interrupted, thealready glowing section must develop sufiiciently abnormal cathode fall to raise .the voltage across the device to-the order oi the original starting voltage. Under some circumstances-for example, relatively large area of already glowing section this section cannot develop a sumciently abnormal cathode fall, and the stoppage of glow travel will persist and only a portion of the device will ever be operative.

Under other circumstances the already glowing section will be able to develop abnormal cathode'falL-but at the expense of serious overloading for a time; this. being a phe-. nomenon which occurs upon each re-starting of the device, cannot be tolerated. To obviate the stoppage in the first place I so form each-of the positioning members, or so arrange them in con- Junction with the electrode wire passing therethrou'gh, that substantial continuity of active suriacealong .the whole electrode wire is preserved; otherwise expressed, so that there exists along the electrode a fully continuous strip of atmosphere of thickness at least a few times 'thelengthoithemeanfreepathofelectronsin the gaseous atmosphere. This may be done in either of two manners. v

In thefirst of these manners. illustrated as to the spacers and I, I provide the positioning member with a' hole (in, ID) substantially fitting the electrode passing therethrough and therefore providing a good mechanical engagement; but I provide in the member, adjoining the holeover a minor portion of the hole periphery, anaperture (lo, "17) illustrated in Figure id as a sectoral one extending outwardly to the periphery.

of-the positioningmember. In Figure 4b the apertures, again sectoral for example, have been alternatively illustrated as it!" and "D", each extending for a finite distance inwardly 'of the positioning member. A similar arrangement has been illustrated inJigures 2a and 2b in connection with member 34 for the wire lb, with the '(whichwould normally nicely pass the double wire) has been provided along .a portion of one side a generally semicircular aperture 34a (preferably or 95. mm. or more radius) which 'maintains continuity of exposed surface along each of, the two wires 6b .and. 5a.

Accordingly to the second manner, I provide about the interrupted surface portion ofthe electrode a bridging member itself capable of glow development-for example a thin wire of iron or preferably of similar material to my preferred electrodes. This has the advantage of permitting a particularly firm holding of the electrode by the positioning .member, and has been illustrated as to the electrode wire lb passing.

through the central spacingmember 34 (Figures 1', 3 and 3, particularly the latter). Thus to the electrode wire at .the point of intended e through member 34 1' weld centrally the bridging wire II. I then slip the member 34, which has,

been provided with asuitable aperture, into place to' surround the weld. I thenslip over the wires,

and into contact with the two sides of the member 34, ceramic or other insulting buttons or beads Illa and lflb which may Wlfi'the form of centrallyapertured hemispheres. Finally I bend back each end of the wire I] and pass the ends in opposite directions through a considerably oversize hole I! (preferably 1 mm. or larger) provided in the'member 34 near the beads, thus bringing the two ends into substantial, though not necessarily perfect, mutual contact. The glow, spreading on the-electrode wire do on either side of the member 34 to the button on that-side, will travel around the portion ofthe bridging wire ll exposed on that side. Jump to the other portionof'the bridging wire, and travel therealong to the wire thou the opposite side of and minimization of cyclic flicker. 75

veniently provided the recessed,

sponding numbershave been used for the com-' the right end with sumx b. In describing these e'ndmember arrangements reference is most conveniently had in Figure l tothe right end of the device where the illustration is largely in central cross-section. A Bakelite or other insulating cap lib, conveniently a moulded one, is cemented to the end of the envelope l, where the envelope diameter is reduced for union with the stem, the cap being long enough to surround the stem. At the bottom of the cap-i. e., at its extremity disposed toward the center of the envelope-is conveniently provided the flange Mb; centrally of the top of the cap is conexternallythreaded bossl lb. Around the main body of the cap is wound the resistance 8b above-mentioned,

the wire being conveniently lightly covered with cement after winding. At the extremities of the resistance may be provided the lugs'flb and 43b. The lead-in wire at the end of the device is connected to the lug 4212, while the lug 43b isconnected to a metallic button b centrally inset into the recessed boss Mb. To the button b is also soldered the insulated wire 45b which connects this end of the device with the terminals 9. Freely surrounding the wire 45b is the .shell assembly 46b which comprises the threaded bushing 46b held in the shell proper 46b", which may be of any convenient material such as metal. The shell may be internally provided with the recessed female-threaded boss 45b" adapted to fit the threaded boss lb; after soldering of wire 45b to button b, the shell assembly may he slipped along the wire toward the device and secured thereto by screwing onto the boss llb". The threaded bushing 46b may extend externally of the shell 46b", may be slipped through a hole provided in any convenient bracket or support 41b, and secured therein by tightening on-the bushing of a nut 48b. Thus the device may be supported at its extremities.

The advantage of arranging the resistances 8a and 8b in the manner just described, is that they maintain the end portions of the envelope, which are removed from the positive column, at least at the temperature of the more central envelope portions. This is desirable in the case of operation in abnormally-low ambient temperatures because the coolest envelope portion will in general determine in normal operation the amount of mercury vaporized and hence the vapor pressure; and, while only a very small pressure is needed, too little might then be developed if the end envelope portions were not warmed by external means. Ventilating holes such as "b may be,

provided in the shell proper lib" to obviate excessive heating of the resistance unit therewithin.

It is very desirable to maintain the spacing between the parallel wires 4b and b at a relatively low value, at least compared with the envelope diameter-with a device of the general characteristics herein set forth as typical, at a value of 3 to 5 mm. for example. This is to insure easy starting of the discharge each time the system is connected with the supply voltage, and, in alternating current operation, early starting in each half-cycle with attendant good light efllciency While I ordinarily prefer the electrode construction which 2,118,000 be similar for the two (ends ofthe device; corre- I,

Ihave already shown-and described, it is fe'asable with alternating current operation, so long as the desirable close spacing of the wires 4b and 5b is retained, to mount the letters or indicia'la alternately to the two wires 4b and 5b as shown by the separate letters- A and B in Figure 5, and/or to provide such letters as may be desired in double formation, as shown by the right-hand letter A in Figure 5. It is'further'possible, as shown by the letters and portions '40" in Figure 6 hereinafter more particularly described, to mount letters or indicia to a longitudinal wire (e. g., 5i) which is spaced widely and not' closely from the electrode of opposite polarity (e. g., 5b)but in this case letters forming a portion of the one electrode system must in places approach the other electrode system in the close spacing abovementioned; preferably the places of such approach will be at least as near to each other as the diameter of the envelope. And in any event the longest path which must be traversed by any section of the discharge is preferably maintained smaller than the diameter of the envelope in the interest of uniformity of glow over the letter portions.

Figure 6 is particularly intended to showan arrangement wherein letters and/or portions thereof (40") are at any desired rate caused to dash on and off, other letters (4c) being provided if desired for continuous illumination. The arrangement is readily carried out by providing the wires 41) and 5b and mounting such letters as are to glow continuously on'the wire 4b as before, and by additionally providing a longitudinal wire such as 5i--for example above the lettersand mounting thereto such letters as are intended to glow intermittently (the spacing cautions abovementioned being desirably observed). The leadin wires 2b and 3b for the respective wires 41) and 5b are externally connected through the respective resistances 8a and 8b across the voltage supply--which in this case by way of example has been shown as the secondary 54 of an autotransformer 54, of which the primary 54' is connected to the line terminals 9'. The lead-in wire 52 for the added wire 5| is shown connected through a resistance 53-for example, of Similar ohmic value to resistance 8b-to the contacts 55 of a thermostatic switch 55, and therethrough tacts will respondby opening and thus cooling the element whereupon the contacts will again close, and so on.

From Figure 6 there has been omitted, only however in the interest of simplification, any showing of the envelope I or of the support of the wires 41) and 5b (and 5|) at their none-lead-in extremities by such supporting wires as 32 and 33 of Figure 1. Subject to this qualification, the structural portion of Figure 6 indicates in general the mechanical method which I prefer to employ in constructing a device according to my invention: In other words, the electrodes wires are connected to the appropriate wires already sealed in the stems 2 and 3, as by welding, to make a diameter at one and only, and the stem at such end-is sealed to the envelope. rinally,.utiliaing an appropriately high amount of heat, the other or full-diameter end oi the envelopeis dfawn inwardly to meet the other stem, and thereto sealed.

. Ino'oncluding the description, I may mention some typical parameters, in addition to such as have already been mentioned, of devices constructed 'in accordance with my inventionthough this I do in an illustrative rather than a iimitative spirit. 'l'heenvelope has been 0! glass tubing of about 6 cm. diameter, 65 to 70 cm. long.

The wires used for electrodes have been of such an alloy as abovementioned, about 1% mm. in

. diametenthe wires to and It being spaced apart 7 about 3 mm. and the letters being formed to a height 0! about 4% cm. The gas component :of the filling been a mixture or 85% neon and helium, at a pressure between 18 and mm."

Hg, and a quantity of mercury of size notgreater than a pin-head has provided the vapor component of the filling. The resistance 80 'andtb have each of the order or 50 ohms. There has been applied across the system as illustrated in Figure 1 a voltage of about 160 volts A. 0. pro-.- ducing an R.- M. 8. discharge current of about 120 to 150 ma. (which may be seen from the electrode dimensioning set forth above-to represent a current density on the electrode system 4 well in excess of 5 ma., and more specifically oi. the order ofl5 to'20 ma., per squarecentimeter), or

a voltage of about 125. volts D. C. The power."

consumption has been 20to30 watts (principally of course in resistances 8s and 8b), and the device has operated with materially less than'a 20 degree centig'rade rise above ambient temperawill depend materially on the area 0! the electure. v

It will be understood that the valuegoi resistar'rces' 8a and 8b, and of that operating current,

trodes-particularly of the indicia lc, which may vary between'devices otherwise similar. It" is therefore convenient; in finishing the manufacture of one of'these devices, to .equip it temporarily with arbitrarily low-valued end resistshoes (or with none, but otherwise maintaining the ends as warm as the central portions) and by test to determine the total external resistance.

appropriate to su bs tantially the minimum current which produces good glow all over the indicia to. Permanent resistances 8aand 8b may then be prepared and installed, having a total resistance equal to that determined experimentally as abovementloned.

n will a spice-imam that while r have shown and described my invention .interms of. preferred embodiments thereof, .I-do intend not to be limited by all the details of those embodiments, but rather to express the scope of my invention-in the appended claims, broadly 1 as thestate oi the art will permit, 1 -I claim:

' least of the order of 15 mm. Hg and two electrode systems each extending longitudinally substan 1. In a gaseous discharge system, the combination with an elongated envelope, a filling therefor including a rare gas component at pressure at tially throughout said envelope, various portions oione system having widely diti'erentdi'rect separations *irom the other system: of means for maintaining, between said: electrode systems a discharge'havinga density on each. system 0! at least -5 ma. per square centimeter; and a ifirther \mitotstemsandelectrodes. -'1hisunitisslipped into the envelope i, which is initially of reducedcomponent said filling havinga lower mam tion' potential than said gas, atrpressure limited to lessthau suiilcient for appreciable luminous excitation of said'iurther component but 'suificient to luminous eigcitatlon'of said gas tothe immediate vicinity of said electrodes; 4

"tion with an elongatedenvelope, a 'filling'thereior including a rare gas component at pressureat.

least oi theorder of 15 mm. Hg, and two electrode systems each extending longitudinally substan: tially throughout said envelope, .various portions of one system having widely different direct sep maintaining between said electrodesystems a discharge having a, density on eachsystem of at least 5 ma. per square centimeter; and a further. component in said filling --'comprising mercury vaporat t pressure limited to at'most. a few .20 combinaarations =irom the'other sys'tempoilmeans ior 2.1m a gaseous discharge system, the co'mbinarect separations ,Irom the other system: of means for'maintaining between said electrodesystems a discharge havingfa densityion each; system of at least 5 ma.'per' square centimeter; and a fur-- the: component-in said filling comprising a metal vapor'at pressurelimited to 'the order of the minimum required to render-the positive column portion of said. discharge substantially a pure vapor discharge.- I i I 4. In a gaseous discharge system, the combination with an elongatedenvelope, 'a filling there'- for including a' rare gas component at pressure at least 'oi'the orderoi 15 mm. Hg," and two electrode systems each. extending longitudinally sub- I stantially throughout saidv envelope, various portions of onesystem having widely diflerent'direct separations from the other system; 01 means for- .maintaining between said electrode systems adischarge having a density on each system oi at least 5.ma. per square centimeter; and'means,

comprising a further envelope filling of lower ionization potentialthan said gas limitedtowelstively minute pressure, for maintaining between said electrodes a substantially dark positive column.

5.- Ina gaseousdischarge system, the combination fwithan elongated envelope andaflllins there= 'iorincludingja rare gas component at;a pressure wires extending in close spaced relationship to each other and to the wall oi said .envelope'longitudinally through said envelope, and furtherincludlng a plurality of indicia extending from one of said wires for amajor fraction of theenvelope diameter substantially in aplane containing the envelope-axis; means. tor maintaining between I said-electrode means an alternating discharge,

atleast of-the order of 15 mm. Hg, of electrode means including two mutually insulated-straight having-a density, on each electrode means of at) 7 least 5 ma. per square centimeter; and a'further vapor at pressure limited to at most a iew'thousandthsot'onemm. Hg.

6. In agaseous discharge system: an elongated envelope; a filling therefor" includinsa rare gas component; two electrode systems each extending longitudinally 1 substantially throughout said env velope; means Ior maintaining between said eleccomponent in said. filling comprising mercury i0:

- trode systems a normal discharge having adensity on each system of at least ma. per square centimeter; and mercury .within said envelope in sufiiciently smallquantity to limit-the mercury vapor pressureduring said normal discharge'to a maximum of. few thousandths of onemm. Hg,

metal of the iron group with which mercury amalgamates.

'7. Infthe maintenance ofa discharge, in an atmosphere including rare gas ata pressure at least of the'order of 15 mm; Hg. across a wide discharge path of widely difieringshort lengths in its several side-by-side portions, the method of creating brilliant glow throughout theentire terminal portions only of said path while minimizing differences in the potentials across'the several path portions, which comprises'maintaining said discharge at a terminal density of the order of at least 15 ma. per square cm., and maintaining in said atmosphere mercury vapor at a pressure at most of the order of a few thousandths of one mm. Hg; K

8. A gaseous discharge device comprising an elongated envelope; a gaseous atmosphere therewithin comprising rare gas at a pressure at least of the order of 15 mm. Hg; electrode means including two mutually insulated straight wires extending in mutually parallel and .closely spaced relationshiplongitudinally through said envelope. and further including a plurality of indicia secured to at least one of said wires at intermediate points therealong; and a minute source of mercury vapor within said envelope. v w

9. A gaseous discharge. device comprising an elongated envelope; a gaseous atmosphere therewithin comprising rare gas consisting principally of neon, at a pressure at least of the orderof 15 mm. Hg; electrode means including two mutually insulated straight wires extending in 'close spaced relationship to each other and to the wall of said envelope longitudinally through said envelope,

and further including a plurality of indicia extending from one of said wires for a major fraction of the envelope diameter substantially in a plane containing the envelope axis; and a minute source of mercury vapor within saidenvelope.

10. A gaseous discharge device comprising an elongated envelope; a gaseous atmosphere therewithin comprising rare gas at a pressure-at least of the order of 15 mm. Hg; a pair of electrodes extending longitudinally through said envelope, at least one of said electrodes including an intermed lately supported member having a continuous longitudinal exposure to said atmosphere, and including a plurality of indicia secured to said member; and a minute source of mercury vapor within said envelope.

11. A gaseous discharge device comprisingan elongated envelope; a gaseous atmosphere therewithin: and a pair of electrodes extending longitudinally therethrough, at least one of said electrodes including an intermediately supported member having a continuous longitudinal exposure to saidatm'osphere. and including a plurality of indicia secured to said member.

12. In a gaseous discharge device including an elongated envelope and a gaseous atmosphere therewithin: a longitudinally extending electrode; and insulating electrode-positioning 'mea'ris'provided with a hole engaging said electrode intermediately of the extremities thereof, and further provided with an aperture adjoining ,said hole over a; minor fraction-of the hole periphery.

13. In a gaseous discharge device including an elongated envelope and a gaseous atmosphere therewithin: a pair of. longitudinally extending electrodes; electrode positioning means through which at least one of said electrodes passes and which closely surrounds said electrode; and bridg- 'lng electrode means extending around the intersection of said positioning means with said electrode.

14. In a gaseous discharge device including an elongated envelope and a gaseous atmosphere therewithin: a pair of longitudinally extending electrodes ofsmall cross-section, and indicia secured to a first of said electrodes, the other of said electrodes having appreciably smaller surface than thefirst but being provided with longitudinal grooves whereby to increase its operating current density at normal cathode fall.

- 15. A gaseous discharge device comprising an elongated envelope, a gaseous atmosphere there-- within, and electrode means including two mutually insulated straight wires extending in mutually parallel and closely spaced relationship longitudinally substantially throughout said envelope,.and further including indicia secured to at least one of said wires at intermediate points therealong.

16.'A gaseous discharge device comprising an elongated envelope, a gaseous atmosphere therewithin; electrode means including two mutually insulated straight wires extending in mutually parallel and closely spaced relationship longitudinally of said envelope and' indicia secured to at' least one of said wires at intermediate points therealong and disposed substantially in a plane passing longitudinally through said envelope, said wires being relatively near; to the wall of said envelope.

17; The combination according to claim 16 wherein said wires lie in a plane substantially normal to said indicia plane. 118. The combination according to claim 16, further including spacing means engaging both said wires in at least one intermediate region therealong, and supporting and lead-in wire means secured to the extremities of said wires and v passing outwardly of the extremities of said envelope at least approximately in a plane parallel with the plane containing sai'd wires.

19. In combination in a gaseous discharge device: an elongated envelope containing a filling of rare gas and metal vapor and a plurality of electrodes, and having inwardly extending 'stems at its extremities; cap members surrounding the envelope extremities; and resistances wound about said cap members, each of said resistances being connected in series with a said electrode whereby to maintain the extremities of said cn-r, velope'at higher temperatures than the intermediate envelope portions.

20. In combination in a gaseous discharge device: an elongated envelope and electrodes therewithin; atleast one cap member secured to an extremity or said envelope and having externally a threaded portion; a resistance wound about said cap member and terminally connected with one HANS WOJTKOWIAK.

of said electrodes; and a shell member having in-

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