US1623351A - Getter and the application thereof - Google Patents

Description

Patented Apr. 5, 1927. 1

- UNITED STATES iPA TE NT oFFicE.

DUNCAN MACRAE, 0F EAsToEANGE, AND HENRY KNEELAND RICHARDSON, OF NEW- ARK, NEW JERSEY, ASSIGNORS T0 WESTINGHOUSE LAMP COMPANY, A coEPoEa- TION OF PENNSYLVANIA.

GETTER AND THE APPLICQTIQN. THEREOF.

No Drawing. Application filed June 8,

This invention relates to electrical devices comprising filaments adapted to be heated to incandescence and more particularly to substances to be applied to such filaments to increase the efficiency thereof.

An object of our invention is the provision of a method for causing getter-s or other beneficial substances to adhere to the filaments for electrical, devices in a proper and efficient manner without using-an organic binder.

Another object of our invention is the provision of an improved substance for increasing the efficiency of incandescent lamps and other electricaldevices comprising incandescent filaments."

A'further object of our invention is the provision of a fusible getter or the like con: tainingan infusible or refractory admixture thereto, for the purposeof causing an even distribution of the getter on a filament and.

preventing the formation of fused beads of the getter substance on the filament.

A still further object of our invention is thepreparation of a getter or the like comprising a refractor or infusible substance admixed with a fusi le substance adapted to cause the refractory portion of the getter to adhere closely to an incandescent filament when the same is heated after the getter is applied thereto. Other objects and advantages willbe apparent as the description proceeds.

In the copending application Serial No. I'TQLG'PZ. MmRae, filed May 18'. 1921, a getterand method of applying the same, and

assignedto the Westinghouse Lamp Com- 7 pany, thereis described a method of applying a getter consisting of cryolite which comprises fusing it to a filament for an incandescent lamp or the like. This method would be inapplicable to substance'ssuch as thoria, alumina, or other refractory materials which it might be desired to apply to a filament, be-

cause such substances cannot be fused conveniently in practice and, therefore, if used alone cannot b'e'made. to adhere to'thefilament. 1 4 I I Our invention obviates the above noted difficulty by providing a getter composed primarily of twoconstituents or classes of constituents. One constituent or class of constituent-s is'rcfractory or infusible and may comprise thoria, CGIIUID'QXldG, yttrium oxide, alumlna, silica ora mlxture of two or more of 1922. Serial No.-566,847.

not be rubbed off during any of the usual.

manufacturing operations.

Our invention also contemplates a method of firmly affixing the getter to one or more of the parts of a lamp without the use of an organic binding material. It also aims to provide a method of introducing a getter .into a lamp in a manner whereby the same is substant ally free from adsorbed gases. By

eliminating organic material and adsorbed gases, the prese'ntinvention removes the necessity of providing a substance, such as phosphorus, to combine with such gases. v

It has been found that the small amount of residual gas in a lamp after exhaustion may be efficiently disposed of by our getter which is also introduced to off-set the obscuring effect of volat-ilized filamentary material. Many kinds of material'may be used in preparing a getter according to our inven-. tion, the requirements of our getter being that the materials used shall be beneficial to the lamp. and that part of the getter shall be refractory or infusible and another part shall be more or less fusible. Although we have mentioned certain substances which we prefer to use in preparing our getter, it is to be understood that the same are merely illustr'ative and we are not restricted to their use.

thoria and cr'yolite in desired proportions,

such, for example, as two parts of tho'ria and one part of cryolite, is preferably powdered and mixedwith a liquid medium, such as water, to form' a solution or suspension mixture, and is preferably applied to the filamentary material before the latter is mounted on the stem of a lamp. The filamentary material is furnace and-there the coating becomes heated a amount of getter applied is a'predeterminedto a temperature high enough'to dry'fdehydrate and melt the fusible constituent or constituents, in this instance, cryolite. If the filament is composed of tungsten or other substance which readily oxidizes when heated, the coating should be fused thereon in an atmosphere of hydrogen or other non-oxidizing gas. This process causes the getter to become firmly affixed to the filamentary ma terial and atthe same time, expels adsorbed gases and reduces the surface area of the getter material to render it less adsorbent to gases. s

It has been found'that a fused coating of getter strengthens a filament, such as tungsten, so that the latter may be more readily handled without breaking. This additional strength is especially valuable in filaments of r very small diameter, as such break very easily.

The filamentary material or wire when it has fused thereon a coating of getter, may be mounted on a spider for an incandescent lamp in the usual manner. After sealing the mountso formed in a. bulb and the evacuation and tipping off of the same, the lamp may be lighted at its designed potential or normal voltage without the necessity of auxiliary apparatus. to guard against short circuits therein, inasmuch as there is not present a sufiicient quantity of gases to ermit gaseous conduction on lamp voltages. lVhen the lamp is lighted, the incandescent filament serves to vaporize a portion of the getter which, in such state, combines withthe small amount of residual gas, chemically or physically, and, reaching the comparatively cool surfaces of the bulb, is condensed as an invisible deposit and there serves the purpose of adsorbing the ordinarily obscuring deposit of filamentary material which otherwise would cause blackening of the bulb.

The thoria, in the getter previously described in detail, may be replaced, in whole or in part, by cerium oxide, yttrium oxide, alumina or other similar refractory substances. The cryolite in the getter may be replaced, wholly or partly, by lithium.

fluoride, boric oxide, orsimilar fusible substances. Experience has shown, that a filament coated according to the present invention will resist the ordinary abrasion which may occur in manufacturing manipulations and retain such coating on the wire in substantially the full quantity applied. This is a distinct advantage, inasmuch as the quantity calculated for the greatest efliciency of the lamp.

The present invention is also applicable to the manufacture of vacuum or gas-filled tubes, which employ an electronemitting element. Such elements of electron tubes may consist ofan electrode coated with materials, such as oxides, which function as the primary electron-emitting element. ,It is desirable that the electron emission from such coated electrodes be constant in quantity, which requires that the coating he retained on the electrode'without loss therefrom. The method disclosed in the present invention of firmly affixing such a refractory coating to an electrode will, therefore, be valuable in the manufacture of electron tubes.

WVhile we have described what we now consider preferred means of practicing our invention, itis to be understood that man changes may be made therein within the spirit and scope of the appended claims.

What is claimed is: v 1. The method of treating incandescent lamp filaments comprising applying a refractory getter thereto by means of an inorganic binder fused to the filament, introducing the filament into a bulb, exhausting the bulb, vaporizing the binder and thereafter vaporizing the refractory getter.

2. A filament for an incandescent lamp or the like evenly coated with a firmly adherent film comprising a refractory getter substance and an inorganic fusible substance the latter of which is fused onto the filament.

3. In an electric device comprising an evacuated sealed envelope, a filament having a firmly adherent coating consisting of a mixture of an infusible getter substance and a. fusible substance the latter of which is fused onto the filament.

4. In an electric device a metallic filament comprising a firmly adherent coating of a mixture ofthoria and cryolite adapted to be raised to incandescence by the initial application of normal voltage.

5. In an electric device comprising an evacuated sealed envelope, a metallic filament having fused thereon a uniform coatingof a powdered mixture of thoria and cryolite.

In testimony whereof, we have hereunto subscribed our names this 7th day of June,

DUNCAN MacRAE.

HENRY KNEELAND RICHARDSON.