US2271658A - Luminous sign electrode construction - Google Patents

Description

Feb. 3, 1942. s, c. MILLER LUMINOUS SIGN ELECTRODE CONSTRUCTION Filed Dec. l, 1938 2 Sheets-Sheet l INVENTOR. Saw/ C. M/L 5e /AA ATTORNEY.

Feb. 3, 1942. s. c. MILLER LUMINOUS SIGN ELECTRODE CONSTRUCTION 2 Sheets-Sheet 2 Filed Deo. l, 193B INVENTOR. 5 ,mw/EA C. MM L v2 Il" @si Patented Feb. 3, 1942 LUMINOUS SIGN ELECTRODE CONSTRUCTION Samuel C. Miller, New York, N. Y.

Application December 1, 1938, Serial No. 243,308 v Claims.

This invention relates to electrodes; more partieularly to electrodes for luminous signs, such as neon tube signs; more particularly to a metalto-glass sealed electrode employed in luminous tubes depending for their luminescence on the effect of high potential electric currents on an ionizable inert gas lling. Co'ordinately therewith it relates to a method of making such electrodes.

For the sake of simplicity, I will hereinafter employ the term neon tube to designate luminous gaseous discharge tube to designate all tubes of the character mentioned, that is tubes having an inert ionizable gaseous filling that are excited by high potential electrical currents, and it is to be understood that when I employ the term neon tube I do not intend to restrict myself to such tubes in which the gaseous filling is neon. y

One of the greatest problems=met with in the manufacture of neon tubes is the difliculty of sealing the electrodes into the glass of the tube so as to secure a seal that will be leak-proof under conditions of use and will withstand the bombarding treatment to which the tubes are subjected during the process of manufacture.

While the well known Housekeeper. joint provides a leak-proof seal for large electrodes, it is not commercially practical. As a consequence, although large electrodes are preferable, they have not until recently been much used and small electrodes which are more readily sealed have been used in place thereof.

In my copending application S. N. 190,230 filed February 12, 1938, of which this is a continuationin-part, I have taught the use of specied chromium steel uniformly deep drawn into cup shaped electrodes, specifically referring to Allegheny 55 metal as the material of which electrodes are made, and have also disclosed a construction and a method adapted for the commercial production of large electrodes. As stated in my application aforesaid, the typical analysis for Allegheny 55 is more specifically described in Bulletin 55 Allegheny Steel Co. 1934 and includes from 23 to 30% of chromium with carbon .25%, manganese 1.00%, phosphorus .025%, sulphur .025%, silicon .50% and the balance iron. However, while a leakproof seal may be obtained by following the teachings of my aforementioned copending application, and the electrodes disclosed therein operate satisfactorily in connection with inert carrier gases such as red gas neon tubes, they do not operate properly with glass tubing known as fluorescent tubing or with glass tubing in which in addition to carrier gases, mercury vapor is used. With uorescent tubing using other than inert gases Where electrodes of alloys are used to provide low coecient of expansion compatible to form glass seals such as Allegheny 55 metal, the tube would darken. This I attribute to the alloying with iron of materials which provide it with the appropriate coefficient of expansion of the nature corresponding to glass, the exact nature of the defect of which is not to be taken as controlling but which practical experience has taught causes failure.

It is therefore among the objects of my invention to provide a commercially practical electrode that may be readily joined to glass ina leak-proof manner and at the same time be capable of satisfactory use with neon tubes containing thel inert gases such as helium, neon, argon, xenon, krypton or mixtures thereof as well as with tubes containing gases other than inert vapors or gases, and particularly with fluorescent tubes and with tubes containing the carrier gases together with active gases or vapors, for example, mercury vapor.

A further object of my invention is the provision of an electrode having a portion of its surface that is sealed to the glass of a low coeflicient of expansion base metal alloysuch as Allegheny 55 metal, while its active electrode surface is of a metal capable of satisfactory use with neon tubes containing inert gases or vapors as well as with tubes containing active gases or vapors, and particularly with fluorescent tubes and with tubes containing mercury vapor.

It is also an object of my invention to provide an improved method of assembling electrodes to glass tubes.

Among the more particular objects of my invention is further the provision of an electrode for neon tubes employing active gases or vapors of low coefllcient of expansion alloys amenable to be sealed to glass such as for example of Allegheny 55 metal, with a lining of a metal which is not adversely affected by active vapors or gases such as mercury vapor but of itself incapable of sealing to glass' such as for example purified iron. Swedish iron-known as 'Svea metal and other electrode metals `found satisfactory heretofore with active gases particularly in the relationship with fluorescent coatings of neon sign tubing.

A further difflcultyexperienced with neon tubes is that due to the phenomenon of "sputtering," that is a disintegration of the metal of the electrode on the walls of the tube, and which phenomenon is particularly objectionable because it causes rapid deterioration of the tube by reason of the occlusion o f the gases in the tube in the deposited electrode metal.

It is a further object of my invention to provide a cathode in which sputtering is greatly reduced, if not eliminated. f

It is a more particularobiect of my invention to provide in a neon tube meansl to prevent bombardment of the walls of the tubeadjacent the electrode and to centralize it along the length of the tube.

'Still more specifically, it is an object of ,my invention to provide a ceramic collar in adiacency to the electrode oi' a neon tube, in order to conne the electric discharge into the tube through the opening in the collar. Y

' application. Briefly, they may be summarized i It is further among the more particular objects of my invention to provide means for preventing contact of mercury contained in a neon tube with the electrode thereof. y

It is the general object of my invention to provide a simple, economical and eillcient electrode for neon tubes and a simple, economical and eiiicient method of eifecting a seal between an electrode and the glass tubing for a neon sign tube. l

To attain these objects and such further objects as may appear herein or be hereinafter pointed out, I make reference to the accompanying drawings, forming a part hereof, in which Figure 1 is a longitudinal sectional view through one embodiment of my improved electrode construction, together with a sectional view through an end portion of a glass tube adapted to have the electrode applied thereto;

Figure 2 is a transverse lsectional vievvthrough Vthis-is accomplished by making the inner lining -v '24 of-Svea metal. whichV is a puriiled iron-'oi the electrode of Figure 1 taken substantially on i the line 2-2 of Figure 1, looking in the direction of the arrows;

Figure 3 is a view partly in section, 'showing` the electrode of Figure 1 sealed in place on the glass tube portion of Figure 1;

Figure 4 is a view similar to ing a modied form of electrode;

Figure 5 vis a view similar to Figure 3 showing an electrode including a ceramic collar: Figures is a view similar to Figure 5 showing a modified form of ceramic collar;

Figure 7 is a sectional view on the line 1-1 of Figure 6,'1ooking in the direction of the arrows;

Figure 8 is a view in perspective of the ceramic collar'of Figures 6 and 7;

Figure 9 is a fragmentary longitudinal sectional view kthrough an electrode insulator housing showing a luminous gaseous discharge tube provided with an electrode of the' type shown in Figures 1, 5 or 6 assembled in place therein;

Figure 10 is a fragmentary elevational view, partly in section, illustrating apparatus for Derforming the process of sealing my improved electrode in place on a glass tube, and also indicat- Figure 11 is a sectionalview on the line Il-II of Figure 10 looking in the direction of the arrows; 1

Figure l2 is a section on'the line I2-i2 of Figure 10 looking in the direction of the arrows.

Reference will now be made to Figures 1, 2 and 3 for a detailed disclosure of an illustrative embodiment of my improved electrode construction.

In these figures the numeral designates the Figure 3 but show-v outershell 22 with a driving nt.

as resistance to heat, resistance to oxidation, the property of being readily wetted by fused glass at the temperatures necessary for working the glass customarily employed for neon tubes, and sumcient resistance to deformation atthe'temperatures to which it is subjected duringl the process of bombardment.

However, while this metal is satisfactoryv for a neon tube electrode, even to the extent of forin-` using Allegheny metal or its equivalent as a'l carrier therefor. In the illustrative embodimentA of my invention disclosed in Figures 1, 2 and 3.

Swedish iron. Other lining metals found by experience to be suitable in the presence of active gases or vapors though not suitable for a metal to glass seal may be employed. 'I'his lining 24 is preferably forced The'end of the tube 2| is adapted to seat within the mouth portion 2l of the electrode, and during the sealing operation, which will be described hereinafter in connection with Figures 10, 1l and 12, its end portion assumes the conelectrode as a whole, and the numeral 2| designates an end portion of the glass tube of a luminous gaseous discharge tube, such as a neon tube. In Figure 1 these are shown prior to astour shown in Figure 3, lfrom which it appears that the tapered end 2l of the tube 2l extends into contact with the end 26 of the Svea metal lining 24, so that the entire active surface of the electrode consists oi' the lining metal. A slight bulge, 21, in the walls of the glass tube is also shown; thisusually results from the method employed for the sealing operation, as will appear hereinafter. v

Attention may here be called to the centering effect of the mouth portion 23 on the glass tube, whereby on relative axial movement of the electrode and the tube, the latter'will automatically tend to align itself axially with the electrode.

In the form of. electrode shown in Figure 4 I attain the same result in a diuerent manner.

in this ligure the electrode is designated in geninto the..

overlies the extreme end of the tapered portion 33 o! the outer Allegheny metal shell.. l.

The glass tube 8|. when it assumes its inal position, with the electrode sealed in place thereon, comprises an outwardly flaring mouth portion I5, the inner surface of which is fused to the outer surface of the tapered portion 83 oi' the electrode, and is further shown as engaging the rib 81 oi' the Svea metal lining, so that the surface of the Allegheny 55 metal lining is at no point exposed to the gases within the tube. An inward bulge 3l in the walls of the'glass tube that slightly overlies the flange 31 further assures this result.

In order to prevent bombardment of the walls of the electrode adjacent the seal between the cup shape electrode and glass, I may provide means to centralize the electric discharge along the longitudinal axis of the tube. Such meansare shown in Figure applied to an electrode of the type shown in Figure 3.

'I'he 'numeral 40 in Figure 5 designates generally the electrodeand the numeral y4| the glass tube to which it is sealed. The router yAllegheny metal shell 42 of the electrode :is :provided :with an inner lining 44, on the end :'26 which :seats a collar A48 df a material adapted to .intercept the electric Vdischarge from the electrode, 'itheip'assage of whichiis therebyconned 'Ito -.the Lripening 48 centrally positioned in the @collar .48. I have found fceramic materials, :such yas gporcelain. a suitablefsubstance for the-collar. The tapered end portion 45 of the glass tube :11| sseats within the outwardly flaring mouth portion 43 of the Allegheny metal shell 42 and iis sealed thereto while its extreme end portioni Eis also sealed -to the ccollar 48. As before, the -Allegheny metal is :kept out of contact with the ugases with which the 'tube is illled.

.Injthe form of Figures 6, 'l :and 18, :which also includes a ceramic collar, vthe electrode iconstruction sof Figure 5 is used. 'but the :ceramic collar l has :a flange thereon surrounding its central opening and extending outwardly vfroxnk'the cofllarv in -ia direction away from the electrode, Jrwhereby globules of mercury collecting in the 'tube and running along the walls thereof and the vWall .of the collar, will be prevented from running into the electrode and` affecting the surface thereoi.

vIn these figures 60 designates the electrode, 6I 'the glass tube and 68 the ceramic collar. lThe electrode 60 like the electrode 40 of Figure i5 is `provided with an outer Allegheny 55 metal shell l62 provided with an outwardly daring mouth portion 63 and an inner lining of Svea metal, the end portion 66 of which abuts against the collar 58. The glass tube 8|, like the tube 4l of Figure 5, is shownzas having a tapered end vportion 65 seating within and sealed to the mouth portion 63 of the electrode and also sealed to the collar 68 at its extremefend portion 10.

The collar E88 is shown provided with a ilange 12 surrounding/the restricted opening 1I therein, and extending outwardly from the electrode and into vthe tube, and having the desired function 'of preventing the entrance of metallic mercury into the :electrode chamber. Means may also be provided nor the purpose of strengthening or bracing the collar and its flange. Such means is shown in the fform of ribs 13 extending outwardly from the `iiarige 12.

In Figure 9 I have illustrated the manner of installing a neon tube provided with electrodes of the type herein disclosed. and which electrode, by way of example, has been shown as the form of Hgure 1. The mounting shown is of the type more specifically described and illustrated in my Patent -No. 2,046,960;5Ju1y 7; 1936.

It will be observed that an electrode housing 5 insulator lll is shown as mounted on the sign frame 8|. A contact spring 82 is mounted within the .hous 980 and presses against the electrode 2l sealed the end of the tube 2|. The many advantages of this eilicient'and compact mount- 10 ing need not be amplied upon here, since they will be found fully set forth in the aforementioned patent. In addition, it may be noted that my cup shaped electrode provides great compactness with appropriate electrode surface not l5 attainable by a lead-in-sealed electrode.

Th method phase Iof my invention will now be explained with thesaid of Figures l0, 1l and 12 in reference to sealing a glass tube into an electrode of the form shown in Figure 5.

In these gures the'glass tube is shown at '4I and the electrode at". The former is shown as mounted `on a spindle of one of the stocks of a glass blowers Ilathe of a conventional type adapted to carry out fthe desired operation, and the electrode is mounted on the spindle of the other stock. For holding the glass tube. I I have shown a chuck 285 mounted on the .right spindle 86 of the lathe and provided with a mandrel 81 extending `into the bore of the tube 4I, and `iaws `88 pressing .against the outer walls of the tube. t 'Ihe electrode 4;I may 'bexmounted on the other spindle 88 in any :suitable for preferred manner, as byvclampingl in fthe A.chuck 90.

The spindles 88 and 18,8 :are shown as rotatable similarly by means fof suitable gearing indicated at 9 I which is actuated `lfromta common source of power, such as the rotating shaft 92.

Air under pressure may he admitted to the '40 inside of the tube 41|, while it is :rotating by means of a central duct 93 the chuck 85, that comlatter being in communication through pipes 95 anda valve86 with a source .o'f compressed air. The mounting of the chuck I@lill is such that it may move axially on the spindle 89, for which purpose it is shown carried hn :a -head 81 slidable con the spindle 89 but rotatable therewith, and -movable axially by an arrangement comprising a 50 unember 98-shown as movable in an axial direction by an arrangement comprising a rack 99 and a pinion |00.

'Batteries of blow pipes HH are shawn so posiitioxred that they concentrate their ,dames on the i515 point at which the seal is to be Two such :batteries of blowpipes are shown; while they are shown in the drawings as operating in a ver- ;tical Ailane, `it is to be remarked that `they are preferably positioned so as to operate in a horiuo iaontal plane.

In rcarrying out my improved process the electnode 4II is mounted in the chuck 90 and the tube 4l in the chuck 85, and the chuck 80 is then moved 'by means of the rack and pinion arrangement 99, lll) until they assume the position of Figure 10. The blow pipes lill are then played on the exterior of the mouth portion 43 of the electrode, while at the same time the lathe is rotated and axial pressure is maintained on the 10 electrode bythe aforementioned rack and pinion adjustment. At the same time air pressure is maintained within the tube 4| by the air pressure system heretofore described.

When the requisite temperature has been 0 reached the glass of the tube 4| becomes plastic,

municates with a duct -84 -in the spindle, the

and, as a result of .the axial pressure on the electo effect proper annealing. It will be observedl that as the glass seats itself in the electrode there is a wiping action that tends to effect proper wetting of the electrode surface, and to dislodge any impurities thereon that might interfere with the proper formation of a lap Joint between the glass tube and the electrode. Simultaneously with the formation of this lap joint, a butt joint is formed between the end of the glass tube and the ceramic collar 48.

It will further be noted that the blow torches play primarily on the metal of the electrode and not exclusively' on the glass, which, where it is underneath the metal, thereby receives its heat through the wall of the metal. Consequently the former is more intensely lheated than the latter, which is of advantage in securing a good seal. since the metal canV be heated to a higher temperature without deformation, than can the glass.

This procedure also serves to have the electrode support the glass as it reaches plasticity.

It is to be understood that where the other forms of electrodes herein disclosed are used, that the process outlined herein for the, form of Figure 5. will be modified as needed to suit the particular requirements.

It will thus be observed that I have provided an improved electrode of novel and simple oonstruction adapted for use with neon tubes employing red gases or gases other than red gases, and in particular fluorescent tubes and tubes containing mercury, an electrode that can be readily and securely sealed to/a glass tube, and an electrode in which sputtering is reduced.

It will further be observed that I have provided an improved process for readily and effectively performing the operation of sealing the electrode and the glass of a tube together.

While I have speciiicallyexempliiied as the metal for forming the outer shell as made of Allegheny metal No. 55 as specifically described in my copending application aforesaid, it will be understood that any base metal alloy electrode may be utilized which has the desired compatibility for fusion to glass and the necessary coefficient of expansion but which may be deleterious in its action in the presence Vof an active gas such as mercury vapor particularly where fluorescent coatings are applied to the glass tubing.

It will also be observed that while I have specifically exemplified purified iron or Svea metal as the liner metals which may be used and which are not deleterious in the presence of activevapors such as mercury vapor particularly, it will be understood that those metals which may be used in the presence of mercury vapor and fiuorescent coatings on glass tubings of neon signs or similar illuminating units, may also be used, from experience gained in using electrodes housed within the glass and sealed by a lead-in-wire connected with the shell electrode.

Therefore my invention it will be understood,

has broader application than merely involving the use of Allegheny 55 metal and a liner of purified iron such as Svea metal but that it resides in the combination in a thimble or cup shaped electrode of a low coefficient of expansion metal which is scalable to glass which may be uniformly drawn to sustain the temperatures involved in glass in metal sealing operations, with a liner of electrode metal inert or non deleterious in the presence of active gases or vapors such as mercury vapor where particularly uorescent coatings are used in the illuminating glass tubing, and that the scope of the invention is to be judged by the appended claims.

Having thus described my invention and i1- lustrated its use, what I desire to secure by Letters Patent is:

1. An electrode for a fluorescent neon tube comprising a substantially uniformly drawn shell having a mouth portion defined by angularl'y-directed walls for forming on one surface of said walls a lap joint for a glass-to-metal seal, said shell being made of a metal whose coemcient of expansion is such that it is readily bonded to glass by a lap joint sealing operation, and a liner on the interior of said shell made of a material adapted to serve as the active electrode surface of a neon tube and not deleteriously affecting the fluorescent material embodied in said tube in the presence of active gases or vapors employed to induce a fluorescent effect in operation ofsaid tube, said liner extending in the direction of the walls of said angularly formed mouth portions whereby completion of the seal at the said walls of said mouth portion will also complete a seal below said mouth portion to protect the fluorescent tube from the deleterious eifect of the metal of said shell. l

2. An electrode for a fluorescent neon, tube comprising a substantially uniformly drawn shell having a mouth portion defined by angularly directed outwardly flared walls for forming on one interior surface of said walls a lap Joint for a glass-to-metal seal, said shell being made of a metal whose coeicient of expansion is such that it is readily bonded to glass by a lap Joint sealing operation, and -a liner on the interior of said shellmade of a material adapted 'to serve as the active velectrode surface of a neon tube and not deleteriously affecting the fluorescent material embodied in lsaid tube in the presence of active gases or vapors employed to induce a fluorescent effect in operation of said tube, said liner extending in the direction of the ared portions of the walls of said angularly formed mouth portions whereby completion of the seal at the said walls of said mouth portion will also complete a seal below said mouth portion to protect the fluorescent'tube from the deleterious en'ect of the metal of said shell.

3. An electrode for a fluorescent neon tube comprising a substantially uniformly drawn shell having a mouth portion defined by angularly directed walls for forming on one surface of said walls a lap Joint for a glass-to-metal seal, said shell being made of a metal whose coefficient of expansion is such that it is readily bonded to glass by a lap joint sealing operation, and a liner on the interior of said shell made of a material adapted to serve as the active electrode surface of a neon tube and not deleteriously affecting the fluorescent material embodied in said tube in the presence of active gases or vapors employed to induce a fluorescent effect in operation of said tube, said liner extending in the direction of the walls of said angularly formed mouth portions whereby completion of the seal at the said walls of said mouth portion will also complete a seal with respect to the said liner to protect the fluorescent tube from the deleterious effect of the metal of said shell.

4. An electrode for a iiuorescent neon tube comprising a substantially uniformly drawn shell having a mouth portion deiined by angularly directed outwardly aredwalls for forming on one interior surface of said walls a lap joint for effect in operation of said tube, said liner extending in the direction of the ilared portions of the walls of said angularly formed mouth portions whereby completion of the seal at the said walls of said mouth portion will also complete a seal in respect of the said liner to protect the fluorescent tube from the deleterious eilect oi' the metal of said shell.

5. An electrode in accordance with claim 4.

wherein the metal of said shell comprises a chromium steel.

6. An electrode in accordance with claim 4 wherein the said liner comprises a puried iron electrode metal.

7. An electrode in acordance with claim 1 wherein a vitreous disc formed with an orice is interposed adjacent the mouth of said shell and in which a portion of said liner forms an abutment for said disc.

8.' An electrode in acordance with claim 2 wherein a ceramic disc formed with an orice is interposed adjacent the mouth of said shell and in which a portion vof said liner forms an abutment for said disc, with the disc sealed between the edges of the glass and the abuting portion of said liner.

9. An electrode in accordance with claim l wherein a ceramic disc formed with an orilce abutting' position. t

SAMUEL C. MILLER.

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