US2379025A - Electrode and method of making the same - Google Patents

Description

June 26, 1945. a C MILLER 2,379,025

ELECTRODE AND METHOD OF MAKING THE SAME I Filed Feb. 2, 1942 2 Sheets-Sheet 1 IN V EN TOR. .9/1 MUEL C. MIL A 59.

- A TTOEIVEY June 26, 1945. s, c. MILLER ELECTRODE AND METHOD OF MAKING THE SAME Filed Feb. 2, 1942 2' Sheets-Shet 2 fyflj v INVENTOR.

4 7' Tok/vEY m M M Q L w M on Patented June 26, 1945 UNITED STATES PATENT OFFICE ELECTRODE AND METHOD OF MAKING THE SAME Samuel C. Miller, New York, N. Y. Application February 2, 1942, Serial No. 429,319 Claims. (01.29-25.15)

This invention relates to electrodes; more particularly, to electrodes for gaseous discharge tubing generally referred to as neon lights; and more particularly to methods of making electrodes therefor.

My invention is a continuation in part of my application Serial No. 190,230, filed February 12, 1938, entitled Luminoussign electrode, now Patent No. 2,271,657, Feb. 3, 1942, and my application Serial No. 243,308, filed December 1, 1938, entitled Luminous sign electrode construction, now Patent No. 2,271,658, Feb. 3, 1942.

In my applications aforementioned, there is described the production of an electrode employing a generally cup-shaped electrode shell for forming a metal to glass seal. Specifically, there is mentioned the employment of a heat resisting steel-that is, a chromium steel having the characteristics of being scalable directly to glass of the character generally employed in luminous signs, and I have referred specifically to a chromium steel identified as Alleghany 55, a product made by the Alleghany Steel Company, described in Bulletin No. 55 for 1934, the general composition of which includes from 23 to 30% of chrome; carbon '.25%; manganese 1.00%; phosphorus 025%; sulphur 025%; silica .50%; and balance iron.

In the aforesaid applications I have described the methods for sealing an electrode shell sealable by metal to glass under various conditions whereby an efiective metal to glass joint is secured, which will withstand the processing to a which electrodes of this character are submitted.

The preferred method involves the formation of a lap-joint as secured by a' wiping action, with the shell tapered inwardly or outwardly to securing the wiping lap-joint, even though there is likewise disclosed a metal to glass seal secured by a butt-joint or edge embedding of the metal into the edge of the glass.

Still further in said application Serial No. 243,308,.a method and mechanism are described whereby a wiping lap-joint may be secured by axially aligning the electrode and the glass tubing, and applying the heat to the electrode which is transmitted to the glass, whilepressing the electrode and glass to each other, relying upon the heat transmittedfrom the metal to the glass to fuse the glass, during the step of pressing the glass and metal together.

The characteristics of 'the'electrode shell as discovered by me havemade possible the achievement of a metal to glass seal in which strains in the glass are minimized, if not completely overcome, by the wiping action in forming the lap-joint. I attribute a large measure of success to the application of the heat to the metal and,

in turn, the transmission of the heat from the metal to the glass while in contact with each other, to provide the wetting action.

The present application has as its objective the specific phases of the method for sealing the glass to the metal electrode, as specifically shown in said prior applications, as well as difierent embodiments thereof for securing the effective wetting action of the metal by the glass, minimizing, if not entirely eliminating, the strains otherwise experienced in endeavoring to join glass to metal.

Still further objects of my invention reside in the provision of a method for sealing metal electrodes to glass without interference due to the processing involved in the treatment of the metal surfaces, among which is the processing involved to reduce the cathode fall by applying electron-emitting substances to the interior sur-' faces of the electrode, and my invention coordinately resides in a procedure for the production of the union of the electrode of metal to the glass and the treatment with the coating l'or the electrode, without deleteriously afl'ecting the metal to glass union.

To attainthe foregoing objects and such furtherobjects as may appear herein or be hereinafter apparent as this description proceeds, I

' make reference to the accompanying drawings forming a part hereof, in which-- Figure 1 is a longitudinal sectional view illustrating the elements entering into. my-assembly for practicing the method; I

Figure 2 is a longitudinal sectional view of the electrode and glass section formed into a seal;

Figure 3 is the. electrode shell at the completion of the application of the electron-emitting coating; Figure 4 is a longitudinal sectional view; of the electrode and glass seal, and glass tubing attached thereto;

Figure 5 is a longitudinal sectional view of another embodiment of my invention;

Figure 6 is a longitudinal sectional view showing an embodiment or the apparatus for eflecting'the glass to metal seal;

Figure 7 is a transverse sectional view oi. an-

other embodiment of apparatus for etlectin'g the metal to glass seal.

Figure 8 is a fragmentary section taken on the line 8-0 of Figure 7; g

Figure 9 is. a still further embodiment illustrating apparatus for effecting the metal to glass seal.

Making reference to the drawings, there is illustrated in Figure l, the electrode shell ID, in accordance with the preferred embodiment of my invention in the application Serial No. 190,230, wherein a cup-shaped electrode shell is employed, made of heat resisting, chromium steel, preferably from that identified as Alleghany 55. This shell is provided with a flared mouth II, the character and extensiveness of which flare compensates for a wide tolerance in the glass tubing and makes feasible, in one form, a wiping lapjoint contact. In this embodiment, however, I employ a small glass collar or ring I2, which is of a length sufficient to provide a strong lapjoint, leaving an excess beyond the mouth of the electrode I I for purposes which will appear more clearly as this description proceeds. The collar I2, as thus provided, is then brought into union with the electrode shell, as more specifically illustrated in Figure 2, forming the metal to glass seal I3 and providing a free edge I4. After thus assembling the electrode shell I and the collar or short section I2 of glass together, the electrode shell is then coated by spraying, tumbling or other coating procedure, preferably to provide on the interior surface I5, the coating I6 of electron emitting substance.

Whatever coating procedure is involved, it will be' observed that the metal to glass sealing surface is duly protected and that the coating of material which, in the preferred form provides the electron emitting surface, is deflected away from the joint between the glass and the metal.

After thus applying the coating I6, a product is afforded which may, at any subsequent time, be sealed to the tubing "by joining the edges I4 and I8 to each other, using the usual glass blowing technique to effect the butt-joint contact seal IS.

The sequence of procedure of protecting the surface which is to form the metal to glass seal the metal to glass and then coating with the electron-emitting surface and then finally applying an extended section of glass tubing does not in any way devitrify, strain, or weaken the metal to glass contact. Furthermore, great economies are efiected in the simplification of the procedure for applying the electron-emitting coating with 'maximum efficiency.

In the embodiment illustrated in Figure 5. I employ a shell Illa, of chrome-iron, as in the previous example, in which the mouth IIa is unaltered and is a rectilinear continuation of the shell itself. In this embodiment, I provide a collar or short section of glass I20. and effect a wiping but joint seal I30, leaving a free edge Ila.

With the assembly thus provided, the electrode shell may be coated with the electron-emitting substance, after which the edge Ila is available for sealing to an extended section 'of glass tubing by the usual glass blowers technique, as described in connection with the embodiment illustrated in Figure 4.

I will now refer to the methods of effecting the metal to glass seal to secure the wiping joint contact employing, preferably, heat resisting steel of chrome-iron composition.

Referring to Figure 6, the electrode I0 is supported upon an insulator of glass, porcelain or other refractory material and is then brought within the heating zone 20 of the coil 2I of a high frequency induction heating unit. A watercooled, single coil made of flattened tubing is a unit which I have found suitable. The leads 22, 23 are connected to the high frequency generator, the capacity of which is dependent upon the size of the cup-shaped electrode I0, and the fusion characteristics of the glass, the joining whereof will be hereinafter described. I

It is understood, however, that the shell is of a size to accommodate present-day neon sign glass tubing.

With the shell electrode positioned within the heating zone, a collar I2 is loosely set into the shell mouth, where this form of shell is employed. A section of 4; to /4" has been found suitable, with the range of sizes of glass tubing employed in neon signs.

Where a cylindrical shell electrode is employed. as exemplified in Figure 5, the collar may be selected to make a butt-joint with the edge of the shell adjacent the mouth thereof. Longer sections of tubing may be employed, as shownat 2| in dotted lines in Figurefi, indicatingan optional employment of an extended section of tubing where the coating procedure described in connection with Figures 1 to 5 is'not directly employed.

In the event that an extended section of tubing is employed, centering means 25 (diagrammatically illustrated) are used to hold the tubing upright in the mouth of the shell, or upon its edge. as in the case of a Housekeeper seal, or in the form illustrated in Figure 5. Thereupon, the current is applied, inducing the generation of heat in the metal electrode. The heat generated is chosen to be sufficiently high to melt the glass collar or tubing resting on the flange or rim thereof. As the glass melts it will, by its own weight, flow down into the flare, where this form of construction is used, until the proper depth has been reached, as ascertained by trial as to the time required for the same so that the current may be turned on and off by an automatic timing device.

In the event that a butt-joint contact is desired, as exemplified in Figure 5, 'the glass will be caused to flow exteriorly as well as interiorly of the mouth of the cup-shaped electrode, leavin a free edge I4 for further sealing to an extended section of tubing, as already explained.

Where an extended section is employed, as optionally illustrated in Figure 6, using a flared mouth, cup-shaped electrode, the weight of the tubing upon the electrode will cause the forma tion of the wiping lap-joint metal to glass seal quickly.

The alternative method of sealing employing the transmission of the heat to the glass through that induced into the metal shell electrode produces a highly superior seal since every particle of the metal electrode making contact with the glass is uniformly heated to the same temperature. This causes a uniform adhesion between the glass and the. metal. When the contact is made by the mere weight of the collar or tubing, due to the wetting action of theglass, and with little preliminary heating of the glass until the metal has reached the fusion temperatures of the glass, where adhesion begins, strains in the glass are avoided and devitrification of the glass is prevented. Furthermore, since the heat generated by induction in the metal electrode is conducted to the glass only at that portion which comes in contact with the heated electrode, distortion of the glass by reason of difliculty of control of fused glass is avoided.

In this mode of operation for heating by induction, particularly when a tapered mouth, cupshaped electrode is employed, itis only necessary in order to secure to the electrode a glass collar or tubing to employ such material whose outer diameter over-rides, in part, the taper. In instances where an unflared or untapered electrode is employed, as exemplified in Figure 5, the glass collar or tubing abuts the edge of the electrode.

The transmission of the heat from the metal electrode to the glass is further made possible in the preferred form of my invention where the chrome-iron alloy steel h'ereinabove described is utilized. This method of sealing metal to glass, involving the heating of the metal uniformly wherever it may be in contact with the glass, assures uniform adhesion, elimination of strains, avoidance of devitrification and deformation of the glass, assuring an axial position of the glass and shell to a high degree.

Another method of sealing the cup-shaped electrode to the glass tubing, involving the application of heat to the cup-shaped electrode and the transmission of the heat generated in this electrode to the glass, to secure sealing of the glass and the production of a wiping lap-joint seal, will now be described, using gas flame.

Inthe construction embodied in Figure 7, a sheet 26 of refractory material, such as mica, asbestos, is provided, suitably supported in a horizontal position. Mica is preferred by me. Oriflces 21, having inwardly directed prongs 28, serve as the support for the electrode 29. The points of the prongs 28 are calculated to center the minimum outside diameter of the shell 29, while engaging the fiared mouth II to hold the flared mouth above the upper surface 30 of the sheet 26. In this position, burners 3| apply heat to the bottom wall 32 of the shell electrodes. In this position, glass tubing of an oversize to fit within the flared mouth I I is positioned in the electrodes. The glass may be in the form of the collars or short sections previously described, where there is mentioned the procedure of coating with the electron-emitting coating on the interior surface of the shell electrode before effecting the metal to glass seal.

Alternatively, an extended length of glass tubing may be positioned within the flared mouth of the electrode. Heat is uniformly transmitted by conduction through the metal electrode to the glass. The sheet 26 actsas a protective shield, preventing direct contact of the flame with the glass and assuring the heating of the glass through the heat conducted to it by the metal that is being heated.

The formation of the prongs 28 within the orifices 21 serves to provide a passage 33 between the wall of the orifice and the exterior wall of the electrode conducting heat adjacent the sealing point of the flared mouth of the elec trode, without undue dissipation of the same to the refractory sheet which supports the electrode.

The above method and apparatus, exemplify the production of a metal to. glass seal by a wiping lap-joint contact since the wiping action, wetting the surface of the metal with the fused glass as it is formed.

I The method described, with the apparatus illustrated, is particularly conducive to mass production in that-a large number of shells may be conveniently mounted and heated simultaneously.

The reliance upon the wiping action of the glass to the metal that is heated eliminatesthe necessity for blowing, and avoids the consequent deformation or axial disalignment in effecting the seal orv the labor and care for re-establishing axial alignment between the glass section and theshell. All of these factors minimize the production of strains in the glass, or the prolongation of the treatment which may be accompaniedby devitrification of the glass. I

In a still further embodiment of my invention. more particularly shown in my application Serial No. 243,308 now Patent No. 2,271,658, the electrode shell ID is held in a glass turners lathe. It is held in axial alignment with the glass tubing or collar I2 and while heat is applied to the outer periphery of the shell, the end of the glass tubing or collar. is introduced within the flare of the mouth of said electrode.

The glass and the shell electrode are then pressed towards each other as the electrode .reaches the temperature fusing the glass in'contact with it, thereby securing a wiping lap-joint seal. As in the prior embodiment, heat is transmitted to the electrode 'and this; in turn, is transmitted to the glass in contact with the electrode, to effect the requisite fusion of the glass.

Where the shell is held in a glass worker's lathe, the axis of which is horizontally disposed, air under pressure may be admitted to the tube as the glass and electrode are moved axially toward each other, while heat is being applied to the electrode. A vertical arrangement of the axis of the electrode with its mouth upwardly directed, may be utilized, in which event the weight of the glass upon the surface of the elec trode will serve to secure the wiping lap-joint seal as heat is transmitted to the electrode sufficient to fuse the glass.

- It will be understood that while the method or sirable on the interior surface of the electrode,

as this procedure not only ensures completely protecting the interior of the metal electrode with the coating, preventing darkening of the tube and assuring an active electron-emitting surface, but deleterious effects upon the metal to glass seal are avoided.

While I have described a procedure wherein I first produce a short section or collar of glass and attach this to the mouth of a shell electrode, in that by this, procedure there is left a straight edge exposed for sealing to thetubing to which it is to be eventually sealed, it is understood that the mouth of the shell may be provided with a coating of glass by dipping the mouth of the shell in molten glass, preferably localized to one face of the taper or flare to secure, to some extent, the desired result.

The electrode shell so coated by any one of the procedures described and provided with the proweight of the glass resting upon the electrode serves to produce the on the surface of the edge It or Ma may be readily wiped away before effecting the seal I9. The procedure wherein the coating material I6 is applied to the electrode after the protective collar has been applied, assures a continuous or complete coating on the electrode surface, minimizing the darkening effects on the glass tubings coated with fluorescent material as used in this field. Exposure of metal without the coating tends also to localize heating effects and where uncoated material is adjacent the glass, devitrification may be experienced.

By the method described, I am not only enabled to efl'ect economies in production and make practical the utilization of cup-shaped electrodes for high voltage gaseous illuminants, but I am also enabled to provide these cup-shaped electrodes directly to carry the electron-emitting coating or like protective coating, without an deleterious effect upon the metal to glass seal in the subsequent bombarding processes or the like processing, to which the electrode is subjected as an incident to the complete manufacture of the gaseous discharge illuminant.

Other advantages, not specifically mentioned, from the disclosure made, will readily become apparent to those skilled in the art.

By "mass coating operations, as used in the appended claims, it is intended to include the hereinbefore method of application of a coating to the electrode by coating operations which distribute the coating without control as to localization of the coating as by spraying or tumbling operations.

While the mostproflcient results may be secured by practicing the complete sequence of steps described for preferred operation, it will be understood that advantages lie in selected features, as set forth in the appended claims.

Having thus described my invention and illustrated its use, what I claim as new and desire to secure by Letters Patent. is-'- 1. In the method of forming a gaseous type of luminous tubing having a cup-shaped electrode, the mouth of which is joined by a metal-to-glass seal to glass tubing and with said electrode carrying an electron-emitting coating on its interior surface, the steps which include sealing a sectional portion of glass tubing to the mouth of the cup-shaped electrode to leave an unsealed portion extended adjacent the mouth of the electrode providing an opening for the electrode of a magnitude to leave the interior of said electrode accessible for coating by mass coating operations, then applying to the interior surface of the electrode an electron-emitting coating by distributing the coating without control to localization of the coating on the metallic surface of the electrode and thereafter sealing to said unsealed portion another section of glass tubing to form the luminous gaseous type tubing.

2. In the method of forming a neon gas type of luminous tubing in which the glass tubing is provided with a cup-shaped electrode, the mouth of which is sealed to the glass tubing by a metal-toglass seal, and in which the electrode carries an electron-emitting coating on its interior surface, the steps which include sealing a sectional portion of glass tubing to the mouth of the electrode to leave access to the interior of said electrode by mass coating operations and leaving an exposed edge of glass adjacent the mouth of the electrode, and then distributing a coating of electronemitting material to the interior of said electrode by spraying, and thereafter sealing another section of glass tubing to the exposed edge of said sectional portion of the tubing.

3. In the method of forming a neon gas type luminous tubing having a cup-shaped electrode with the mouth thereof sealed to said glass tubing by a metal-to-glass seal with said electrode carrying an electron-emitting coating on its interior surface, the steps which include attaching to the mouth of said electrode by fusing, a collar of glass of a magnitude not to interfere with access to the interior surface of said electrode by mass coating operations, thereby covering the mouth of the electrode and leaving an exposed edge of glass adjacent the mouth of the electrode.

and then applying to the interior surface of the electrode an electron-emitting coating by distributing the coating without control to localization of the coating on the metallic surface of the electrode by tumbling the electrode in the coating forming material and thereafter sealing another section of glass tubing to the collar applied to the mouth of the electrode 4. A cup-shaped electrode for a gaseous type of luminous tubing, having a section of glass sealed to the mouth thereof by a metal-to-glass seal, the other end of which projects beyond the mouth of the tube and of a length, the magnitude of which leaves the mouth of the electrode open and the interior of the electrode accessible for mass coating operations, the section of glass tubing projecting only for a suflicient distance adjacent the mouth of the electrode to permit the form the gaseous type of luminous tubing, and

the interior surface of said electrode carrying a coatingof an electron-emitting material and the glass of said section in contact with the electrode being free from the electron-emitting material.

5. In the method of forming a aseous dis charge type of luminous tubing, the glass tubing envelope whereof having sealed thereto a cupshaped metal electrode of heat resisting steel, the mouth of which is tapered and to which mouth the glass is sealed by a wiping lap-joint contact with said electrode, and said electrode carrying an electron-emitting coating on its interior surface, the steps which include attaching to the electrode by a wiping lap-Joint contact seal, a collar of glass of a magnitude substantiall not to interfere with access to the interior surface of said electrode by mass coating operations, thereby covering the mouth of the electrode and leaving an exposed edge of glass adjacent the mouth of the electrode, and then applying to the interior surface of the electrode an electronemittirig coating by distributing the coating without control to localization of the coating by mass coating operations and thereafter sealing another section of glass to the collar applied to the mouth of the electrode.

SAMUEL C. MILLER.

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