US2179310A - Vapor electric device - Google Patents

Description

Nov. 7, 1939. A, H. ToEF-FER" VAPORELECTRIC DEVICE Filed April 14, 1938 nNvENTQR WITNESSES:

' .ATTORNEY Patented Nov. 7, 1939 iJNiTED STATES Edwin@ VAPOR ELECTRIC DEVICE Adolph Iii. Toepier, Wilkinsburg', Pa., assigner tc Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation o Pennsylvania Application April 14,

7 Claims.

My invention relates to a make-alive electrode for a vapor electric device and more particularly to electrodes of the high resistance type and the method of making the same.

In the operation of vapor electric discharge devices, it has been found advantageous to employmake-alive electrodes of some high resistance material such as boron carbide, carborundum, graphite, etc., to initiate an arc at the beginning of each conducting period in the rectifier. Recently, engineers have been designing and constructing electrodes to minimize the operating currents and voltages required to start an arc in such rectifiers. Tests have been made using irregularly shaped pieces of some high resistance material as make-alive electrodes, but considerable difficulty has been experienced with such electrodes which may heretofore have been unusable due to the fragile nature of the material and the difficulties of mounting the same.

In the male-alive electrode according to my invention, I utilize a quartz tube or some similar refractory material capable of withstanding high temperatures and heat shock. A narrow slit in the order of one-sixteenth of an inch is made in the side of the tube and then lled with irregular shaped pieces of boron carbide, carborundum or graphite. I select the pieces of the resistance material large enough not to pass through the slit, yet capable of projecting out through the slit. A suitable conductor for carrying current to the high resistance particles is extended down into the quartz tube so as to be in contact with the broken pieces of resistance material. Due to the buoyancy effect of mercury when such make-alive electrodes are immersed therein, a good contact between the conductor and the resistance material is maintained.

It is, therefore, an object of my invention to provide a make-alive electrode requiring a low operating current to initiate the arc discharge.

Another object of my invention is to provide scription taken in conjunction with the accompanying drawing, in which:

Figure l represents diagrammatically a vapor discharge device of a type with which my im- 55 proved make-alive electrode may be utilized;

1938, Serial No. h95?? (Cl. Z50-27.5)

of my invention comprises an evacuated container 3 of glass or other suitable material having an anode 5 sealed therein. Disposed with re* spect to the anode 5 and adapted to cooperate with it in conducting an arc discharge through the container 3, I show a cathode l of vaporizable material such as mercury. Suspended above' the cathode 'l and having a portion permanently projecting below the surface of the cathode "l is mounted a make-alive electrode il of the type which I shall fully explain. The anode 5 and the cathode 'l are externally connected with a load Il and some suitable source of supply potential i3. Likewise, the make-alive electrode 9 is connected externally through a suitable unidirectional device !5, such as half-wave rectier, with a grid control adapted to pass current to the make-alive electrode Si at a predetermined time with respect to the anode potential.

In constructing a make-alive electrod-e ii acn cording to Fig. 2 of my invention, I employ a quartz tubing l1 opened at one end. Substantially near the closed portion of the tube il, I bore a narrow slit i9 having a width in the neighborhood of one-sixteenth of an inch. The slit lil need not be of any particular length, but I prefer one having such a length that a portion of the slit i9 remains below the cathode surface l as well as an approximately equalv portion above .the surface to compensate for variation in the mercury level. It is to be understood, however, that I do not wish to limit my construction to one slit lg for it may be desirable to have several slits i9. Suitable size particles is of some high resistance material such as boron carbide are inserted into the tube ll to such a depth as to cover the slit portion it of the quartz tube il, It is a necessary property of a satisfactory make-alive material iii that it shall not react chemically with the mercury in the presence of an arc discharge, nor should the make-alive material i8 become wet by the mercury.

In preparing the make-alive material l@ contemplated by my invention, I take a rod of boron carbide and break it up into pices of a suitable size and screen the broken pieces to free the nely pulverized particles from those I intend using. The quartz tubing I1 is lled with many irregular shaped pieces of the starting material I8, so that the slit I9 is substantially covered. It may be desirable to shape the tubing i1 at this point so as to cause a portion of the boron carbideparticles I8 to protrude out from the slit I9, thereby having an active portion exposed to the mercury cathode 'I when the makealive electrode S is mounted in place. A suitable rod ZI of conducting material is extended into the open end of the tubing I1 and is brought into contact with the starting material I8. The rod 2| in Fig. 3 of my invention likewise may have a slit in line with the slit I9 of the quartz tubing I1.

According to Fig. 4 of my invention, I provide a make-alive electrode 9 of the type brought in through the mercury pool 1. A rod 23 of Kovar or molybdenum, having a stem portion 25 and a cup portion 21, is brought up through the mercury pool 1, so that the cup portion 21 protrudes slightly above the mercury surface 1. An insulating covering 29 of glass separates the rod 23 from the mercury in all but a slit portion I9 of the cup 21 which I maintain exposed to the cathode 1. The insulating covering 29 serves in addition as a vacuum seal for the make-alive electrode 9. Disposed in the base of the cup portion 21 of the make-alive electrode 9 is some insulating material 3l, preferably glass. The glass insulator 3l may cover a side portion of the cup 21, but should be maintained below the mercury level. Particles of boron carbide I8 ll the cup portion 21, which I maintain closed at the projected end. A Kovar flange 33 sealed to the insulating covering 29 may be welded or copper soldered to the metal container 35 at the bottom thereof.

In the operation of the arc discharge device 2, an exciting potential is applied to the make-alive electrode 9 and an aro is struck between the mercury cathode 1 and an active portion of the boron carbide particles I8 which protrude out through the slit I9. Upon proper conditions of potential,l the arc immediately expands into a greater arc which will transfer quickly to the anode 5 if the latter is sufliciently positive. Several of the make-alive electrodes 9 tested operated on lO amperes peak current with a peak potential of 35 volts.

While I have shown and described specific embodiments of my invention, it will be apparent to those skilled in the art that many changes and modioations can be made therein without departing from the true spirit of my invention or the scope or the appended claims.

I claim as my invention:

1. A make-alive electrode comprising a container of insulating material, a slitted opening in a lower portion thereof and a plurality of independent loose particles of high resistance material in said container, the size of said particles being such that only a portion of several protrude out from said slitted opening and a conductor in Contact With only a portion of said particles.

2. A make-alive electrode for an electric arc discharge device comprising a container of insulating material, a mass of loose particles of resistance material in said container, a slitted opening in said container adjacent said particles, the width of said slit being less than the size of said resistance particles and a conductor extending into said container and being in contact with some of said particles.

3. A make-alive electrode for an electric arc discharge device comprising a hollow cylindrical body of non-conducting material closed at one end, a slitted aperture near the closed portion oi' said body, a quantity of loose particles of high resistance material lling a substantial portion of said body and a conducting body extending into the open end of said non-conducting body and in contact with said resistance particles.

4. In combination with a mercury-pool discharge device, a make-alive electrode comprising a` quartz container substantially lled with loose particles of boron carbide, a vertical slit in a lower portion of said container, said boron carbide particles capable of protruding from said slit and a conductor extending into said container, said conductor being in contact with at least some of said boron carbide particles but out of contact with said mercury-pool.

5. A vapor-electric device comprising an evacuated container, a pool-type cathode therein, an

anode cooperating with said cathode, a makealive electrode dipping into said cathode, said make-alive electrode comprising a container of non-conducting material, a plurality of loose particles of resistance material in a lower portion of said container, a slitted opening in that portion of said container dipping into said mercurypool, an active portion of said resistance particles extending through said slit and a conductor in contact with part of said particles.

6. In an electric arc discharge device comprising an evacuated container, an anode and a mercury cathode therein, a make-alive electrode extending upwardly through said cathode, said make-alive electrode comprising a stem portion and a cup portion, said cup portion partially projecting above the surface of said cathode, an insulator disposed in the base of said cup portion of said make-alive electrode, a slit in said cup portion, an insulating covering separating said Q make-alive electrode from said cathode in all but said slit portion and providing a vacuum-tight seal for said make-alive electrode and a plurality of loose particles of high resistance material in said cup portion, an active portion of said resistance particles being exposed to said cathode by way of said slit.

'7. A make-alive electrode for a vapor-electric device comprising a container of insulating material, a narrow longitudinal opening along one side of said container, a plurality of loose particles of resistance material in said container and partially extending through said opening, and a conductor extending into said container and making contact with at least one of said particles.

ADOLPH H. TOEPFER.

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