US2271657A - Luminous sign electrode - Google Patents

Description

` Feb 3,'1942-- s. c, MILLER i LUMINoUs SIGN ELECTRODE Filed Feb. 12, 1958 2 Sheets-Sheet 2 INVENTOR. SAMUU. C. MAL/ ER /A ATTORNEY Psa-'nad Feb, 3, `1942 UNITED STATE sf PATENT OFFICE 8 Claims.

This invention relates toelectrodes; more particularly to electrodes for'luminous signs, such as neon sign construction, and to methods of making the same; more particularly, to a metal-toglass sealed electrode employed in luminous tubes operating, with an ionizable inert gas filling, to obtain a gaseous discharge producing a luminous effect under high potential electrical exciting force. f

Electrodes employed in electrical discharge devices of the character mentioned, as known to me, have attendant problems in their manufacture and operation in addition to the cost of their production. Such construction usually involves an electrode shell to which there are affixed leads and sealed within a glass. envelope. Electrode devices of this character are more particularly illustrated inthe patent to Lohman No. 1,739,513 and my Patent No. 2,'o64,485. The specic features of these described electrodes have been devised to cure problems in operating conditions and in manufacturing operations particularly due to the exposure of the interior and exterior surfaces of the shell electrode within the zone of activity within the sealed glass envelope,

As desirable as these constructions may be, they offer additional problems in cost and construction in order to introduce these assemblies in the final sign in the electrical connections th'at may be required to conduct the electrical current to the electrodes.

I have discovered that the full benefits of a cup-shaped electrode, scalable directly to glass,

may be made available and provide an electrode from metaltoglass sealing competitively priced with sealed-in glass electrode shells by the employment of h'eat resisting stainless steels which are characterzed'by their resistance to oxidation at elevated temperatures necessary for processing the luminous tube assembly and which metal is further characterized by the formation of oxidized scale with great difficulty at high temperatures but which, nevertheless, provides scale of such adherence as not to fiake off and interfere with a metal-to-glass seal joint;

that sfurther characterized by a coefficient of expansion suitable for joining to glass of thc character employed in neon discharge devices.

Such metal which' I have discovered is suiti able for the production of cup-shaped metalto-glass scalable electrodes is exemplified in a h eat, resisting chromiumv steel, more particularly a chromium steel having the characteristics identified as Allegheny 55, the typical analysis for which'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%; .025%, silicon .50% and th'e balance iron.

This metal, I have further discovered, is readily wetted by fused glass at temperatures necessary for working glass of the character employed in neon discharge tube signs and has sufficient resistance to deformation at temperat es necessary for processing by bombarding he completed and sealed discharge tube assembly.

Apart froml the discovery hereinabove mentioned, my invention resides in the provision of a cup-shaped electrode of a `configuration amenable to eiecting a seal of glass-to-metal by commercial quantity productive methods. to provide a competitive item with the sealed-in glass shell electrodes. I

A still further object of my invention resides in the provision of a luminous or gaseous discharge tube electrode assembly comprising a deep draw cup-shaped electrode of metal sealed to glass, which makes for compactness and economy in construction, while not diminishing the surface area of the electrode, thereby to give long life, as required in the trade, and further to minimize sputtering, which interferes with refinements in working conditions, particularly in connection with fluorescent tubes, where the sputtering effect would defeat and destroy or reduce the life of tubes of such character.

Other objects of my invention reside in the provision of an electrode assembly and a method of assembly which eects material economies by simplification of construction while achieving long life and 4extended performance in operpointed out, I make reference to the accompanying drawings, forming a part hereof, in which- Figure 1 is a fragmentary, longitudinal sectional view of the partsifor making the electrode, in accordance with one embodiment of my invention;

Figure 2 is a fragmentary longitudinal sectional view, with th'e parts connected and sealed together; v

Figure 3 is a section taken on the Figure 2;

Figure 4 is' a fragmentary longitudinal sectional view of another embodiment `of my inline 3-3 of sulphur vention, showing the parts'immediately before assembly;

Figure 5 is a fragmentary longitudinal sectional view of the parts illustrated in Figure 4,

brought together and assembled;

Figure 6 is a fragmentary longitudinal sectional view of the embodiment illustrated in Figures i, 2 and 3, assembled in position with an electrode insulator housing;

Figure 7 is a fragmentary longitudinal -sectional view of .another embodiment of my invention;

Figures 8, 9 and 11 are fragmentary longitudinal sectional views of three additional embodiments of my invention;

- as illustrated in Figure 2 and the joining of the A section of the glass I0 at its open end'to a glass In this construction, the proportions of the s .parts are shown for Joining approximately a 15 mm. diameter glass tubing II). to a shell electrode II.' The shell electrode is cup-shaped andhas cylindrical walls I2 and a bottom Il of integral construction, `joined to each other bythe rounded edge I4, during the drawing operation, employing a metal more specically hereinafter described.

Adjacent the mouth or opening I5, `the walls I2 are provided with a fiare portion I6. The extensiveness of the flare is calculated to have the smallest diameter adjacent the throat I1 slightly smaller than the outer diameter of the tubing III. 'I'he diameter of the mouth I5 is slightly larger than the outer diameter" of the tubing Il, with such tolerance as to take care of the variation in size encountered in connection with the tubing I0, and such variations in roundness as may be encountered in the trade in connection with glass tubing used for luminous sign constructions. With these parts so provided, and the shell II mounted upon a. glass workers lathe, a section of tubing Iii may also be mounted upon a chuck of a glass worker's lathe equipped with blowing means, and while'the shell II and the tubing Il .are heated adjacent the mouth I5 and the edge I8 by the glass workers flame, the parts are brought together until the edge Il, nests within the flare I6. A Joint I9, as illustrated in Figure 2, will thereby be obtained, of intimate and secure contact. 'Ihe flare ln relation to the edge I8 of the tubing provides for a wiping action between the glass and the flared portion of the.

shell, to give the requisite wetting action of the glass upon the metal. The minimum` amount of attention isrequired by the glass blower or the minimum amount of accuracy is required in aligning the parts of the glass workers lathe where automatic machinery may be employed, as any variation in size of the glassin its diameter, as may be encountered in its production or by reason of its fusion during operation will be accommodated by the flare I6 in bringing these parts together in the Joining of the twoat the fusion or melting temperature. An emcient and effective seal is thereby provided, par- 75 is tubing sign assembly, the sign is processed by evacuating the air and heated to the point where al1 the impurities are driven out of the inside of the tubing. The electrodes are connected to a high voltage transformer while drawing out the air, until a discharge takes place between the electrodes. brought to a bright red heat, approximately 900 C., and the juncture of the glass to metal must be sufficient to prevent collapsing of the glass as well as the metal. The employment by me of the tapered or flared glass to metal juncture and the cup-shaped electrode of the metal hereinafter to be more specifically described, assures a maintenance of the seal during this rigid processing operation. This I attribute not only to the formation of the seal `as already described, but also to the characteristics of the cup-shaped metal electrode which I have provided.

When so assembled as part of a sign and associated with the sign frame 20, the electrode housing insulator 2I and pressed against the contact spring 22 of anassembly more specifically described and illustrated in my Patent No. 2,046,960, July 7, 1936, an exceedingly compact arrangement is provided in that the shell I I may be brought into immediate contact with the contasting spring 22 without any further provision iorbringlng these members into electrical conducting and contacting connection.

The depth of the cup-shaped electrode provides all of the requisite surface area on the interior surface of the assembly, to give the long life and requisite discharge for maintaining operating conditions for luminosity. The. likelihood for sputtering is minimized and where the sign assembly is used in connection with fluorescent glass tubing or glass tubing coated with nuorescentvcompositlons, the elimination of sputtering in conjunction with any mercury vapor yet further insures long life of fluorescent signs.

While I have described and illustrated in Figures 1, 2 and 3, my preferred construction which is most amenable for quantity production meth` ods in the` formation of the sea] joints of glass to metal and for other purposes hereinbefore described, an important contributing factor of my invention lies in the discovery of a commercially practical metal from which the cup-shaped electrodes may be formed. Accordingly, where quantity production methods for forming the juncture or seal between the glass and metal are not of vital Vmoment and where it may be desired to obtain some of the features of my invention. a simple cylindrical shell 23 may be provided. This shell diners from that heretofore described in that no flare need be provided at the mouth or adjacent the edges 2l. The metal throughout may be of uniform thickness where I employ a shell made from Allegheny-55 metal, hereinbefore described, and which, for purposes of reference, I will designate as chromium steel.

The preferred alloy constitution of Alleghenyhas already been given and while this metal heat resisting, drawn.

During this operation, the metal is known to resist high heat. it has never been employed for the purposes discovered by me in that this metal has-been regarded as not suited for deep drawing. Any contour which involves difficult fabrication steps, such as deep drawing operations, has not been regarded as-the field for the employment of Allegheny-55 or similar heat resisting chromium steel. However, extended efforts involving more or less minute progressive changes in forming this metal have led to the discovery of the successful adaptation of this metal for deep draw, cup-shaped electrodes in which the full rigidity of the metal may be emi ployed without resorting to the need for tapering the metal itself in order to provide what is generally referred to as a Housekeeper seal.

Thus in the embodiment illustrated in Figure '7, the walls of the shell 23 may be maintained of uniform thickness to the edges 24 where heat resisting, drawn chromium steel of the character herein described is employed. With such shell, the tubing Illa may be brought together with the shell 23 to form the seal IBa, in which the glass is fused on the exterior and interior surfaces. The uniform depth D of the metal throughout its length, to and including the edges 24, provides a rigid joint of requisite strength which has heretofore rendered the tapered metal employed-in Housekeeper seals impractical.

During the processing step or bombarding step in making the complete sign wherein the metal is almost brought to a bright red temperature, the thickness D of the metal, at the point where it is embedded in the glass at the joint Isa, will prevent collapsing of the metal to glass juncture.

Thus, where speeds of operation and production for making the seal of glass to metal are not of vital moment, the employment of the heat resisting drawn chromium steel of the character herein described, especially using the uniform thickness of metal D to and including the edges 24, makes possible the employment of this metal for a metal to glass seal while utilizing the extended area as obtained by a deepdraw shell.

For other embodiments of my invention particularlyl conducive to quantity production methods, I have illustrated other forms of deep draw shell electrodes for the formation of metal to glass sea'iable electrodes.

In Figures 4 and 5 there is described a shell electrode IIb, in which a tapered section I6b is formed from the throat Hb.

In joining a tubing |013 with the cup-shaped electrode I Ib of the character described, during.

the sealing operation involving the heating of the glass and metal adjacent the edge I8b and the mouth I5b, the shellelectrode is nested to contact with the interior surface of the tube Ib to provide a joint I9b, more speciflcallyillustrated in Figure 5.

Here again, wide tolerance in sizes is permissible to make possible speeds of production practical for, economical operation, and a thorough wetting of the glass to the metal, to give the desired weld due to the wiping action encountered in the tapered joint I 6b and the flare given to the glass in joining the glass tubing Ilib to the shell IIb.

Where employing tubing of about 15 mm. dil interior wall of the glass tubing Inc.

through the tubing, during the processing or bombarding operation, is around 300 milliamperes, it may be desirable, especially where the joint is of the type Where the metal is on the interior of the glass, to provide a surface configuration of the shell to minimize the attack of the discharge upon the glass at the point of contact of the metal.

For this purpose, reference is made to the embodiments illustrated in Figures 8 to 12, the constructions whereof have 'been devised to use the high currents specified, or longer durations ofY time of treatment, and to minimize anisr adverse effect upon the juncture of the metal to glass.

In the vembodiment illustrated in Figure 8, a shell electrode IIc is employed, of the general character illustrated in Figures 4 and 5. In this construction, however, the tapered portion I6c is extended to leave a lip I5c, spaced from the This constricted mouth, spaced from the juncture of the glass to metal Isc, allows the discharge during the processing or bombarding operation to go-inside the shell and minimize the temperature at the juncture Isc.

Another form of construction to minimize the temperature at the glass juncture is illustrated in Figure 9 wherein an electrode shelli Id is provided at its mouth with a flange IBd,v substantially at right angles to the wall of the shell I Id. Here the metal t0 glassjoint iSd may be formed by a pressing operation of the edge of the glass I8 to the flange ISd, to obtain a lap joint and a butt joint instead of the tapered lap joint of the embodiments illustrated in Figures 1 to 5 and 8.

In Figures l1 and 12 I have illustrated a shell electrode of the same general character as described in connection with Figures 1, 2 and 3. For purposes of minimizing the discharge and increase in temperature adjacent the juncture I9, I provide a deilecting member 25, in the form of a rod, extending axially in the shell electrode I Ie so that its end 26 is adjacent the mouth of the shell and its opposite end 21 contacts the bottom I3e. I may aflix the rod 25 in any suitable manner, preferably by spot welding the end thereof 21 to the bottom I3e, as shown at the point 28.

In operation, during processing or bombarding, especially employing the current through the tubing around or in excess of 300 milliamperes, the heat of the discharge will be absorbed first by the rod 25, to minimize the high temperature adjacent the juncture I9, made by metal to glass by the gradual conduction of the heat incident to the bombardment from the rod and then through the shell.

It will thus be observed that I have provided a new and novel electrode of simple and compact construction incident to the discovery of the employment of the cup-shaped heat resisting drawn chromium steel electrode, and its rigidity during process, where employing this metal for glass to metal sealing, especially'where I am enabled to eliminate thin sections of metal at the juncture of the seal. It will further be observed that I have provided a form of electrode amenable to quantity production methods and which embodies compactness of construction, effecting material economies in the manufacture of this form of device.

It will also be observed that by the construction herein provided,rdifiiculties which are involved in sealed-in-glass shell electrodes, such as sputtering effects, are overcome, and that my construction avoids the need for special considto prolong their useful life.

Having thus described my invention and illustrated its use, what I claim as new and desire to secure by Letters Patent, is-

1. In a luminous discharge device including a glass tubing envelope, drawn adjacent one end section to a substantially uniform diameter, said end section whereof includes sealed thereto a substantially cylindrical,A cup-shaped metal electrode of heat resisting chromium steel drawn to substantially uniform thickness having a portion thereof adjacent the mouth normally displaced and to which displaced portion the glass is sealed in wiping lap-joint contact, the direction and extensiveness of said displaced portion providing a sealed portion making a juncture compensating for a wide tolerance in the glass tubingr by being displaced at an angle in respect of the walls of the electrode, the electrode exposing on the interior surface an effective area for long life maintenance, the diameter of the glass tubing being of a size at least a portion of which is within the minimum displaced portion. of the electrode, whereby the electrode and tubing are coaxially aligned by the said lap joint.

2. In a luminous discharge device including a glass tubing envelope, drawn adjacent one end section to a substantially uniform thicltnese,

end section whereof includes sealed therein a gun stantially cylindrical, cuochi-ined ele s heat resisting chromium steel it i tially to uniform thickness jacent the mouth thereof norme to which flared portion the wiping lap-joint contact the d :tion and ein tensivenessof said flared portici-i providing u sealed portion making a juncture compensating for a wide tolerance in the glass tubing, the oleo trode exposing on the interior surface un elfec tive area for long life maintenance, the outside diameter of said glass tubing, at its entrance end section being at least greater than the inner diameter of the cylindrical portion oi' said elec-- trode, whereby the electrode and tubing are coI axially aligned.

3. In a luminous discharge device including a glass tubing envelope, drawn adjacent onefend section to a substantially uniform diameter, said end section whereof includes sealed thereto a substantially cylindrical, cup-shaped metal electrode of heat resisting chromium steel drawn substan tially to a uniform thickness, having a portion thereof adjacent the mouth normally displaced at an angle to form a taper, to the exterior portion of which taper the glass is sealed by a wiping lap-joint, the direction and extensiveness of said taper providing asealed portion making a Juncture compensating for a wide tolerance in the size of glass tubing, the electrode exposing on the interior surface, an effective area for long' life maintenance, the diameter of the glass tubing being of a size at least a portion of which is within the displaced portion of the electrode.

4. In a luminous discharge device including a glass tubing envelope, drawn adjacent one end` section to a substantially uniform diameter, said end section whereof includes sealed thereto a substantially cylindrical, cup-shaped metal electrode Bill . shaped metal electrode of heat resis eration in connection with such devices, in order lap-joint, the direction and extensiveness of said taper providing a sealed portion making a iuncture compensating for a wide tolerance in the size of the glass tubing, the electrode exposing onthe interior surface, an effective area for long life maintenance, the tapered portion including a lip inwardly of the seal, the diameter of the glass tubing being of a size at least a portion of which is within the displaced portion of the electrode.

5. In a luminous discharge device including a glass tube envelope of substantially uniform diameter and wall thickness, an end section where- `of includesI sealed thereto by a wiping lap-joint a sumtantially cylindrical cup-shaped metal electrode of heat resisting steel drawn substantially to a uniform thickness, the walls of the electrode being substantially uniform throughout, the

mouth of said electrode being normally ilarcd. the glass being sealed to the interior surface of said flare portion of said electrode by a wiping lap-joint, the direction and extensivenesc of the :ance

ilared'portion compemating for a Wide t the outside diameter of the said gli being at least greater than the inner of the cylindrical portion oi said electi'ci d. In a luminous discharge inc glass tubing envelope, an end section wh cludes sealed thereto a substantially cup-shaped metal electrode of het drawn substantially to o. uniform t and to the interior ith-ir the glass by a wiping lapmioint, the extenoiveness oi? .salti ilu inciting' .it compensating for a' Wide .lera'hce in and a heat conducting coaitially the said electrode.

7. In a luminous dlscl'lurge device in glass envelope, an endsection whereo sealed thereto a substantially cylindri .i drawn substantially to a uniform "thic .is .a portion thereof adjacent the mouth being normally displaced outwardly, and to which the glass tubing is sealed by a wiping lapjoint, the direction and extensiveness of said outwardly displaced portlon forming a juncture displaced out of the plane of the interior surfaces of the electrode, the outside' diameter of said glass tubing being at least greater than the minimum internal diameter of the electrode.

8. In a luminous discharge device, a substan- V tially cylindrical cup-shaped metal electrode of heat resisting chromium steel drawn subsi/,am

tially to a uniform thickness, the thickness of the said electrode being normally outwardly flared of extensiveness and direction to provide a contacting surface for sealing to provide a scalable juncture outside the plane of the side walls of said electrode and for forming a wiping lap-joint seal between its surfaces and the glass tubing, and

including a `coaxially disposed heat conducting baille member attached to the bottom of said electrode at its interior face.

SAMUEL C. MILLER`

Images