US976527A - Manufacture of electric filaments. - Google Patents

Description

UNITED STATES PATENT OFFICE.

CARL AUEB VON WELSBAGH, OF VIENNA, AUSTRIA-HUNGARY, ASSIGNOB, TO WELS- BACH LIGHT COMPANY, OF GLOUCESTER CITY, NEW JERSEY, A CORPORATIQN-QF 4 7 NEW JERSEY.

MANUFACTURE OF ELECTRIC FILAMENTS.

'No Drawing;

To all whom it may concern:

Be it known that I, Dr. CARL AUER VON WELSBACH, a subject of the Emperor of Austria-Hungary, residing at Vienna, Austria-Hungary, have invented or discovered a certain new and useful Improvement in the Manufacture of Electric Filaments, of which the following is a specification.

My invention relates to the production of a dense, coherent metallic filament for i11- candescent electric lamps, consisting of metallic particles fritted together, and which incandesces at a temperature above that at which platinum volatilizes.

It had been known that osmium possessed several of the rerequisites for this purpose but owing to its utter lack of ductility it has heretofore been impossible to. form it into incandescent filaments. It is exceedingly brittle, and therefore its-particles cannot be depended upon for mutual adhesion (as can the particles of other metals; latinum, for instance,) to permit of the forming of a wire by ordinary processes. Moreover, while it has been recognized that osmium is a good conductor of electricity, yet it was not known that it was non-volatile in wacuo or certain protective gases-at temperatures far above the temperatures at which platinum volatilize's.

I have discovered that, at very high temperatures, in an atmosphere of certain protective gases, or in 'vacuo, it is possible to obtain a commercial osmium filament composed of the metal in a partially fused or cinder-like condition and wherein the particles are in' intimate contact sufiicient to obtain perfect electric conductivity and the requisite flexibility and elasticity for the uses intended, while at the same time the filament 'resists liquefaction even at such high temperatures. This maintaining of its solid form, when the heating is efi'ected in the presence of certain gases or in a vacuum such as that of the ordinary electric lamp, and the refusal to liquefy or volatilize, continue up to temperatures much higher than that at which the volatilization of-platinum pccurs; a fact which is utilized as one of the bases of the present invention.

To fiflly understand my-invention, it must be remembered that the metal osmium (among those of its group of highly infu- Specification of Letters'Patent.

sible metals) is peculiar in that it oxidizes with great readiness, when in the presence of free oxygen.

According to my present method, I employ an inner carrier or fillet upon which osmium 1s deposited, after which I remove V the inner carrier or fillet by the heat of an electric current, in the presence of suitable gases, and cause the particles of osmium to Patented Nov. 22, 1910. Application filed August 9, 1898. Serial No. 688,202. a

and capable of withstanding shocks and jars to which it is subjected when in use. The crosssection of the filament is also dependent upon other conditions present, such as its length and the purity of the osmium employed.

I will now describe a method which may be followed in making filaments of the kind to which this invention relates, although it will be understood that'I do not restrict myself to the precise steps or materials, inasmuch as equivalents for both can be readily substituted by those acquainted with this art.

I first procure an organic thread or threads (I prefer vegetable threads) of fine fibers, which should notbe too strongly twisted together, inasmuch as the pores or interstices should be as open as possible for the reception of the coating or impregnating mass.

I make a mixture'of any of the sulfids of osmium (which although more or less insoluble in water can be suspended therein in an exceedingly fine state of subdivision) with a sinall quantity of suitable binding material, such as sugar. The whole is brought to a cream-like consistency by the addition of a suitable "quantity ofwater.

The ingredients are thoroughly incorporated so that the osmium sulfid may be umformly distributed throughout the mass. I then immerse the thread or threads or coat them with this composition until they are thorpossibility of thorough impregnation) twov or more thereof can be to advantage twisted,

woven or interlaced together so as to form a com osite thread or fabric which shall be of su cient cross section to result in a fila- 'ment of the required dimensions.

This

weaving, lacing or twisting should occur after the threads have been impregnated orcoated with the composition, and to render the thread or threads more uniform they may be drawn while moist, through a die orsubjected to the action of a suitable mold,

to give a uniform cross section and consequently a uniform resistance throughout. After being sufiiciently impregnated or coated and shaped as desired, the threads.

are dried, and are then subjected to dry distillation The threads thus prepared are thereafter placed in an .electric circuit and heated to a point at which the carbon is eliminated and the reduction of the osmium Azompound occurs. To assist in such reduction and preserve the metallic osmium, use is made of a suitable reducing atmos here, as for instance the gases from a ashed back Bunsen burner, which contain hydrogen, carbon-dioxid, carbon monoxid, hydrocarbons and water vapor. The function of the water vapor is to remove the carbon by oxidation and to'form with it an inert gas. After the removal of the carbon I then carry the heat to a point at or beyond that at which platinum volatilizes to complete the cementation or cohesion of the particles of metallic osmium.

Having completed the foregoing treatment, it will be found that the metallic osmium has assumed a thread-like form and is coherent throughout and of su-ificient flexibility and elasticity to adapt it for use as an incandescent electric filament. The fi1aments thus produced are readily distinguishable in that they are devoid of carbon,-have the necessary flexibility and resiliency or elasticity, and depend upon metallic osmium not only for their conductivity, but for the incandescence which is produced at a tem perzture at which platinum would be volatilize I have mentioned sulfid of osmium as one of the compounds which I can employ, but

I wish it to be understood that substitutions can be made therefor of any suitable com pounds of this metal, as, for instance, the tetroxide or the metal itself in afinely divided condition, can be used.

Now while I have set forth one method and certain materials which can be employed, I wish it to be understoodthat I do not limit myself to that precise method or to the materials specified, as my invention includes the use of both ruthenium and rhodium in the place of osmium, and

permeated or coated thereby; When i osmium tetroxid.

methods which are substantially the equivalent of that herein set forth.

"While ruthenium and rhodium can be substituted for osmium, and. treated in the same manner for the production of an incandescent filament, yet such filaments are by no A means as effective as those of osmium,.since both ruthenium and rhodium although melting at temperatures higher than platinum melt at tem eratures much below that of osmium. All oys of osmium, ruthenium, and rhodium may also be used. The efliciency of the filament however, depends upon its withstanding extremely high temperatures and temperatures above that at which plat inum volatilizes. v

To the composition. to be used, may be addedcertain of the refractory rare earths, such as 'thoria, zirconia, and the ytterite earths. If, at the termination of the treatment of the filament in the reducing atmosphere, it is found that it is not of uniform resistance throughout its entire length, the requisite equal conductibility may be obtained by surrounding it again with an atmosphere of the same reducing gases and vapor, and again highly heating the filament by he electric currents and from time to time introducing small quantities of volatile osmium compounds, as for instance, The filaments are now ready for mounting in the ordinary incandescent bulbs which should be thoroughly exhausted or filled with inert gases when ready for use.

In the course of my experiments, I have devised other methods for the manufacture of my osmium filament which are set forth in an application for Letters Patent filed herewith, Serial No. 688,201, and whereinI have made claim s ecifically to my within described, dense, co erent, compact osmium filament which incandesces at a temperature at which platinum would volatilize.

What I claimherein is: 1. The herein described method of manufacturing incandescent electric filaments, consisting in "associat' organic thread with osmium; then, sub ecting the thread to dry distillation; and then, by the action of the electric current, in a suitable atmosphere eliminating the carbon and uniting the metallic particles into a coherent filament of metallic osmium; substantially as set forth.

2. The herein described method of manufacturing incandescent electric filaments, consisting in associating organic thread with'osmium chemically combined with another substance to form a reducible coni pound and thereafter subjecting the same to dry distillation; then, by the action-of the electric current in a suitable atmosphere eliminating the carbon and reducing the said compound to the metallic state; and then,

the thread to dry distillation; and thenv placing the same in a suitable atmosphere wherein, by the action of the electric current the carbon is eliminated, whereby the metallic particles of osmium are united into a coherent filament of metallic osmium, substantially as set forth.

4. The herein described method of manufacturing a metallic electric filament, consisting in associating organic thread with metal having a higher point of fusion than that of platlnum, and, subjecting the same to dry distillation, and placing the same in a suitable atmosphere wherein the carbon is eliminated, and by the action of the electric current at a temperature at which platinum would volatilize, causing the metallic particles to unite'into a dense, compact, coherent'filament suitable for electric'incandescence; substantially as set forth. I

5. A dense, coherent metallic filament for incandescent electric lamps, consisting of metallic particles fritted together and which incandesces at a temperature above that at which platinum volatilizes; substantially as set forth.

Signed this 27th day of July 1898.

CARL AUER VON l/VELSBAOH. Witnesses:

LUDWIG HAITINGE, ADOLF GALLIA.