US930723A - Process of forming electric-incandescent-lamp filaments. - Google Patents

Description

V To all whom it may concern.

, dilute hydrochloric acid. There then remains on the *r %TATE% Parana rrron.

WERNER VON BOLTON, OF CHARLOTTENBURG, AND FELIX HARTMANN, OF BERLIN, GER- MANY, ASSIGNORS TO SIEMENS & OF GERMANY.

PROCESS OF FOR MNG ELECTRIC-TNCANEESGENT-L ...i

HALSKE A. G., OF BERLIN, GERMANY, A CORPORATION k Specification of Letters Patent.

PatentedAug. 1'0, 1909.

Application med. February 3,1909. sextant. e'ie,1c7.

Be it known that We, WERNER VON BoL- TON and FELIX HARTMANN, subjects of the Czar of Russia and the German Emperor, respectively, andres'iding at Oharlottenburg an Berlin, Germany, res ectively, have invented certain new an useful Improvements in'Processes of Forming Electric-Incandescent-Lamp Filaments, of which the following is a specification.

Our invention relates to electric incandescent lamps and is more articularly concerned wlth the filaments f dr such lamps.

It has already been proposed in the United States patent application Serial N 0. 337,122 filed October 2, 1906 to press tungsten powder into a tube composed of ductile metal and to then draw out or roll this ductile tube together'with the metallic powder which it contains into filamentary form.

Now in accordance with the present invention, before the tungsten powder is placed into the tube we place into the latter another tube which also consists of a very ductile metal, as, for example, copper, silver or nickel. The powdered tungsten is then inserted uniformly into this inner tube, the ends of the tube are sealed, for example by screwing or wedging copper plugs into them, and the tube is thereupon rolled or drawn out, or first rolled and then rolled out still further.

A steel tube is preferabl employed as the outer tube. After the d iawing o eration the outer tube is removed, for examp e, when a steel tube is employed, by dissolving it in or sulfuric acid. drawn wire a thin coating or shell consisting of the material of the inner. tube. This considerably facilitates the manipulation of the core of tun sten, so that it can be brought more readi y into the desired shapes and the remaining manipulations necessary for completing the manufacture of the lamp can be carrie out more easil Lastly, the thin coating of the tungsten ament. can then be removed by heating it highly in a vacuum or in a rarefied atmosphere, for exam le in a rarefied atmosphere of hydrogen. Torthis purpose,after the body has been placed into a suitable receiver and the gas contained in the latter has been rarefied, an electric current is sent through the filament. When the temperature has risen suificientl the metal forming the casing or shell begins to vaporize at one place. In a short time it will be found that the vaporizing process has extended along the entire length of the filament and the finished incandescent filament is obtained.

A drawn steel tubemm. long, of 8 mm. exterior, and 4 mm. interior, diameter can be em loyed for example, a copper, silver or nic el tube of having a wall 0.2 mm. thick being fitted exact y into it. Fine, sifted, powdered tungsten is now shaken loosely into the inner tube. I It is preferable not'to press this powder too firmly, but'onl to settle it uniformly inthe tube which can be done by lightly, taping the tube on a hard surface. Particuarly uniform results are then obtained, and

simultaneously a certain degree ofporosityis obtained Which has advantages in many respects. The tube is now closed with plugs of copper or silver about 5 mm. long and is then rolled or drawn.

drawn out to the very finest Wires and after the outer shell has been removed a very,

usable incandescent filament is obtained.

During the vaporization of the shell of cop er, silver, and the like, Which is directly on t e tungsten filament an alloy of tungsten with the incasing metal can be formed under certain circumstances. Such an alloy can readily be obtained articularly when the temperature of the fi ament is driven very rapidly too close to the point at which the incasing metal va orizes. These allo shave a more or less high degree of ducti i-ty, so t at .it is possible'to. subject the filaments alloyed in this manner to an additional rolling or drawing process.

be driven ofi later. The formation of such alloys is particularly facilitated b thetungsten bein-pressed1i0t too firm yinto the tube in which it is to be drawn. In exactly the same manner asis here described with reference to tungsten, other highly refractory metals, erwise, can also process. 4

What we claim as our inventionand desire besubjected to a drawing to secure by Letters Patent is:

1. The hereindescribed process for produc- I V By heating the fila ment highly the additional metal can then 4 mm. exterior diameter and Such a tube'can be 100 which are difficult to draw othl working the "powder into filamentary form.

ing a tube of ductile .metal a tube of another ductile metal, inserting refractory metal powder into the inner tube, and. subsequently tubes Band the refractory metal 2, The hereindescribed process for iroducin filaments which consists in fittin into a 'tu e of ductile metal a tube of a dlfl'erent,

very ductile metal, inserting tungsten powder into the latter tube, subsequently working the tubes and the tungsten powder into filaments which consists in inserting into filamentary form, removing the outer tube, 1

names to this specification in the presence of two witnesses.

WERNER VON BOLTON. I FELIX HARTMANN.

Witnesses:

HENRY HASPER, WoLDEMAR HAUPT,