US1363162A - Filament for incandescent electric lamps - Google Patents

Description

citizen of the United States," I of East Orange in the county of Essex and State ofNew j tural changes resulting from the electric current through the filaments.

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UNITED; stares "PATENT RALPH E. MYERS AND ROY D. HALL. EAST ORANGE, NEW JERSEY, .AS S IGNORS TO WESTINGHOUSE ILA MP COMPANY, A CORPORATION OF PENNSYLVANIA FILAMENT roa INCANDESGENT ELECTRIC LAMPS.

No Drawing."

ToaZZ'zchbmit inag I Be it known'thatwe, RALPH E. MYERS, a

and a resident ersey, and Roy D. HALL, a citizen of the United States, and a resident of East Orange in the county of Essex and State of New jersey, have invented a new and useful Im rovement in Filaments for Incandescent Jlectric Lamps, of which the following is a specification.

ur invention relates to the manufacture of filamentary material, and it has special reference to such filaments as constitute in: candescent bodies for electric lamps.

The ob ect of ourinvention is to provide filaments of the above-indicated character which shall and which sistant to possess good electrical properties mechanical shocks and to strucg passage of 'More particularly, the object of our invention is to provide metallic filaments, composed largely or; mainly of metals of the tungsten type, which shall be highly resistant to the structural alterations known as l offsetting or faulting that tend to develop in this class of filaments during their use. r v .r

Certain materials. which are'suitable for use as filaments for incandescent-electric lamps have considerable mechanical strength when first formed into filaments but become exceedingly fra ile er they have been traver'sed 'by electric c i fents. 'This phenomenon is a characteristic oftufigsten filaments,

.whether such filaments are, prepared by squirting'or drawing processes, and it is have considerable initial strength and which,

' in the'case'of drawn tungsten wire, may even havea tensile, strength many times exceed- .they are found to have undergone marke structural alterations, .The outline of such a filament shows lateral displacement of sections of the filament relativejto. one another,

and this displaced condition, which is known in the art as offsetting,.or faulting, ap-

' pears to be caused by the development and,

Spectfieation of Letters Patent.

Application filed May 14,

shall. likewise be' durable and refound that pure tungsten filaments which ITIOZ.

Patented Dec. 21, 1920, 1915. Serial No: 28,163. w

growth of crystals within the body of the filament Such crystals seem to increase in size in"much the same manner as crystals formed -in liquid solutions, and, if the crystals become large enough to extend almost or entirely'across the filament, adjacent crystals tend to slip along their cleavage planes, thereby giving the'filament the ofi set of faulted appearance above referred to.

It therefore appears that internal crystal- .lization produces offsetting and that ofisetting imparts brittleness. to the filaments.

The phenomenon described above becomes .-a particularly serious problem. in the manufacture of slender metallic filaments which are used in the smaller types of incadescent o i-"i'cs.

lamps such as'25-watt, LO-wattand similar 7 lamps.

An eflicient method of resisting offsetting in lam filaments was proposed, b Dr. A nton ederer and describel. in nited States Patent, #1,180,264 an the Westinghouse Lamp Company.

According. to Dr. Lederers method, and according to the .technicalpractice heretofore Tprevailing, the preferred addition materials are the oxids of the rear earth metals, particularly thorium'oxid. a We have discovered that the oifsetting'of lamp 'filaments may be effectively prevented by the addition of small amounts of other assigned to refractory substances'which neither volatiliz nor decompose under the conditions existingsin glowing incandescent filaments.

The u tances whlch' we have discovered to be particularly suitable for this purpose are the oxids of the alkali metals, the alkaline earths, and also certainoxids belonging to such as berylllum I neither of these classes, oxid, aluminum oxid and, titanium oxid,

For the present purpose, we include magnesium ogzid' amo'ngthe alkaline: earths, as well as. calcium oxid, barium o'xid and strontium oxid. Of the alkali metal oxids,

we have found lithium oxid to be particu larly effective, and, of the alkaline earth .above, or mixtures of one or more of these substances with one"or more o'xids of rare earth metals, 1nclud1 ng thorium, oxid. Very '100 ogzids, calcium oxid and magnesium oxid are found also that excellent results reason why such improved results, are obtained with mixtures is not clear.

()ur invention 1s of special importance 1n the manufacture of tungsten filaments, but

itmay also be applied to filaments composed of other metals, such as molybdenum, tantalu'mand the like.

Very small amounts of ofiset resisting materials are sufficient to greatly retard the development of offsetting. A few hundredths of'one per cent. are sometimes sut'-= ficient, and it is usually unnecessary to add to the filaments more than 5% of their Weight of the offset-resisting additions in order to obtain the maximum offset-resist- -making drawn tungsten filaments, We ordinarily find it convenient to add the offsetresisting materials to the powdered oxid before it is reduced to metal. The precise steps of the process of forming filaments by 'drawing, squirting or otherwise form no part of our presentinvention. It is also to be understood that other limitationsare not to be imposed thereon except as indicated in the ap ended claims.

k Ve claim as our invention: 1. A filament comprising drawn tungsten wire that tends to offset When utilized as a conductor of electricity and also containing calcium oxid and magnesium oxid.

2. A filament comprising tungsten that tends to offsetwhen utilized as a conductor of electricity and also containing at least two'of a group of substances including the alkali metal ()XldS, the alkaline earths,

beryllium (mid aluminum oxid, and tilanrum dloxid.

In testimony whereof We have hereunto subscribed our name this th day of April,

RALPH E. MYERS. ROY D. HALL.

Witnesses ALFRED H. EDGERLEY, FREDERICK A. BET'rs.