US1590352A - Electron-discharge device - Google Patents

Description

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J. M. EGLIN ELECTRON DI S CHARGE DEVIE Fild June 20, 1924 .121! J9 ,l in.

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UNITED STATES 1,s9o,asz

PATENT oFFlcE- JAIEB H. EGLIN, Ol' EAST ORANGE,l NEW JERSEY', ABSIGNOR TO WESTERN ELEJIBIIIC COHPANY, INCORPORATED, OI NEW YORK, N. Y., A CORPORATION Ol' NEW YORK.

Emerson-DISCHARGE DEvIcn.

Application med :une 2e, 1924. serial no. 721,343.

This invention lrelates to electron discharge devices and more particularly to the evacuation of such devices.

In the evacuation of electron discharge devices there is always a small amount of residual gas that is not carried away by the usual pumping medium. It has been the practice to clean up these gases by Vaporizing av reducing medium or getter, such as magnesium or calcium, to absorb them. The vapor emitted by the reducing medium has the tendency to spread and deposit on the surfaces of the electrodes. This deposit mal the electrode surfaces. i

Another object is to insure a high degree of vacuum throughout the life of the device .by preventing the release of the absorbed gases.

ln accordance with this invention, a wire is formed into a closed ring with one end of the wire bent right angles to the lane of the ring, to provide a supporting s ank for the ring. A reducing medium or getter, in the form of tape, is entwined around the 'ring and the shank of the ring is fastened to an electrode assembly of an electron discharge device. rThe ring support is remotely situated from the electrode surfaces to prevent the vaporizing medium attacking the filament which is coated with thermionic active metals or the grid and plate electrodes, which in some instances, may be coated with an oxidized hlm. The getter is vaporized by alternating currents induced in the ring support from a high frequency coil surrounding the electron discharge device. y

Magnesium or calcium have been found to work satisfactorily as reducing agents, in low power electron discharge devices. ln view of its low melting point, magnesium is unstable at the high temperature prevailin in discharge devices operated on high vo tage currents. Aluminum has been found to have equally as good getter roperties as ma esium or calcium and can be vaporized by i h frequency induced currents to effect the c eaning up process. This high vaporizing point metal has the additional advantage of retaining its position on the walls of the vessel and will not react during the operation of high volta' e discharge devices.

In the drawings, ig. 1. is an elevation of an electron discharge device with parts of the vessel broken away to illustrate the invention,

Figr. 2 is a side View of the ring with the reduclng medium thereon showing the method of supporting the ring from the plate electrode, l

Fig. 3 is a top view of the closed ring.

Referring to the drawing, Fig. 1 illustrates an electron discharge device which consists of an enclosing vessel 10 having a reentrant stem 11. A base 12 is cemented to the glass vessel, whereby the electron discharge device may be `.inserted in the socket in the well known manner. Surrounding 'the stem ll is a metallic collar 13, which supports the electrode assembly by means of arms 14. rlihe free end of each arm 1d is attached to a plate electrode 15, which is provided with metallic extensionsl, which carry the upper and lower insulatin plates 17 and 18, respectively. Awire grid 19 is positioned within the plate electrode and is supported by the insulating plates 17 and 18. Resilient springs 20, support a filament (not shown) within the grid and plate electrodes. Lead wires are brought through the stem of the vessel and connected to the terminal pins 21 in the base 12.

A wire, preferably of nickel, is formed into a closed ring portion 22 and `a shank 'portion 23, which is attached to the'plate electrode 14 at 24, preferably by spot welding. The ring portion 22 is bent at right angles to the shank portion 23, whereby the reducing medium, when flashed, is induced to deposit the vapor on the interior glass wall of the vessel adjacent the exhausting tabulation instead of on the coated electrode surfaces. The reducing medium 25, which may be magnesium, is preferably in the form of tape and is entwined around the closed ring portion 22.

The priliminary step in the evacuation process consists of denuding the electrodes titi of the loccluded gases by bombardment in any well -known manner, 4the gases beingcarried away by the pumping means. The heat generated by the bombardment of the electrodes is not sufficient `to vaporize the reducing medium. Therefore, it is found preferable, to Hash the reducing medium by inducing current in the ring 22 by h1 h frequenc alternating current supplied rom a high requency thermionic oscil ator, .such as described in M. J. Kell U. S. appllcation, Serial No. 481,610, file June 30, 1921, entitled Vacuum tube manufacture, since by this method the vaporization is accomplished in a very short period. Furthermore, the high frequenc method can be very easily controlled. he particular arrangement of providing a closed ring for the vaporizing medium, the positioning of the ring remote from the electrode structure and bending the ring support in such a way that its plane is perpendicular to the lines of force of the high frequency current, greatly facilitates the vaporization by induction and furthermore prevents the vapor attackin the electrode surfaces.

The vaporization of the reducing medium is preferably erformed before the denuding process o the electrodes is completed, since this method affords very active cathodes and it is possible to obtain better gas readings. However, other methods may be employed, since it is possible to obtain the same results at other stages of the evacuation process.

Magnesium and calcium have been found to be satisfactory reducing agents for low power vacuum tubes, such as is used in telephonic communications. However, these media have a tendency to Wander in vacuum tubes used in hi h power radio transmitting stations, that is, the high operating voltages, tend to boil the vapor coating on the interior of the vessel wall and the coating diduses over a considerable area on the interior of the vessel thereby liberating the gases absorbed in t e evacuation process. This reaction materially reduces the hi h degree of vacuo and is detrimental to t e efficient operation of the device.

For vacuum tubes o erated at comparatively high voltages it as 'been found that aluminum, which has a high boiling point, (1800 C.) can be vaporized b high freuency induced currents and w11 not react uring the o eration of the device. Since a very high egree of heating is required to vaporize the aluminum getter during the evacuation period, it is preferable to support the aluminum tape on a highly refracto metal wire ring, such as molybdenum.

lthough the invention has been disclosed with the ring supported from one of the electrodes, it is of course, understood, that other structural arrangements may be used without departing from the scopeA of the invention as covered in the appended claims.

What is claimed is:

1. An electron discharge device having an electrode, a wire ring supported from said electrode and a reducing medium in contact with said ring.

2. An electron discharge device comprising a vessel containing an electrode structure comprising filament, grid and plate electrodes, a metal ring having a 'shank attached to said electrode structure, said ring being positioned remote from the innermost ends of said electrode, and a vaporizable metal in contact with said ring.

3. In an electron discharge device, a vessel containing an electrode assembly comprising filament, grid and plate electrodes, a metal ring having a shank attached to one of said electrodes, said ring being positioned remote from the end of said electrode, and a vaporizable metal in contact with said ring.

4. An electron discharge device comprising an enclosing vessel aving a stem, an electrode structure supported from said stem, a nickel ring supported from said structure, and a vaporiza e metal tape surrounding said ring.

5,. An electron dischar e device comprising an enclosing vessel aving a stern, an electrode structure including a cylindrical plate extending from -said stem, a wire attached to said plate and having its free end formed into a closed ring, saidring being bent at right angles to the plane of said wire, and a reducing medium surrounding said ring. Y

6. An electron discharge device comprising an enclosing vessel havin a stem, an electrode structure supporte from said stem, an annular wire supported from said structure, and a tape entwined around said wire.

7. An electron discharge device comprising an enclosing vessel aving a stem, an electrode structure supported from said stem, a wire ring, a vaporizable metal in contact with said ring, said metal being adapted to bevaporized to clean u residual gases in said device, said ring ing positioned in said device whereby the vapor of said metal is prevented from depositing on said electrodes.

8. An electron discharge device comprisin an enclosin vessel having a stem, a plura ity of coated electrodes supported from said stein, a metallic rin sup orted from one of said electrodes, an a re ucing agent wound around said ring, said reducing agent being adapted to be va orized to absorb residual gases, said ring ein located in said device whereby the vapor rom said reducing agent does not attack the coated electrodes.

9. In an electron discharge device, an

10. In an electron discharge device, an

I aluminum ribbon, a refractory metal ring v support for said ribbon, and means for vaporizing said ribbon by high frequency induction heating.

11. In an electron discharge device, an electrode assembly, a reducing medium comprising aluminum, a closed ring for supportmg said aluminum from said electrode assembl and means to vaporize said aluminum y high frequency induction heating.

In witness whereof, I hereunto subscribe my name this 19th day of June A. D., 1924.

JAMES M. EGLIN.

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