US2491990A - Cathode spot control - Google Patents

Description

Dec. 20, 1949 R I, L NGIN. 2,491,990

CATHODE SIOT CONTROL Filed Aug. 19, 1948' Insulation INVENTOR Richard L.Longini.

ATTORNEY Patented Dec. 20, 1949 CATHODE SPOT CONTROL Richard L. Longini, Pittsburgh, Pa., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application August 19, 1948, Serial No. 45,010

4 Claims. 1

My invention relates to a vapor-electric device and particularly to an excitation arrangement for maintaining the cathode spot within a predetermined area on the liquid cathode.

In the operation of metal tank vapor-electric devices, it is necessary to prevent the attachment of the cathode spot to any portion of the metal container. Heretofore, this has been accomplished mainly by brute force methods at great expense and inconvenience. Usually the attachment of a cathode spot to the metallic container is prevented either by complicated shields or by insulating devices interposed between the cathode surface and the metallic container.

I have found that if a conductor is extended upwardly through the surface of the cathode pool adjacent to the desired position of the cathode spot, and the keep-alive electrode is placed in the vicinity of this vertical conductor and a current flows within the vertically-extending conductor (that is, a current flows in the conductor parallel to the keep-alive arc and in the reverse direction), a field will be established about the conductor which will draw the cathode spot into the vicinity of the conductor and prevents its wandering over the surface of the pool so that it might become attached to the metallic container.

It is an object of my invention to provide an excitation system having inherent means for restricting the motion of the cathode spot away from a predetermined surface area on the oathode pool.

It is a further object of my invention to provide means for restricting the cathode spot to a predetermined portion of a cathode pool.

It is a further object of my invention to provide an improved excitation system for a vaporelectric device.

It is a further object of my invention to provide a conductor for establishing a spot control field in a vapor-electric device.

Other objects and advantages of my invention will be apparent from the following detailed description taken in conjunction with the accompanying drawing in which the figure is an elevation partially in section of a vapor-electric device containing an excitation system according to my invention.

In the exemplary embodiment of my invention, the vapor-electric device has a metallic container I in which is a cathode 2 of vaporizable reconstructing material such as mercury, gallium, cesium, potassium or sodium. Cooperating with this cathode 2 is an anode 3 maintained in spaced insulated relation to the container l by means of a suitable insulator 4, current being conducted to the anode 3 by means of a suitable lead-in connection 5.

The excitation system according to my invention comprises a make-alive electrode in or igniter having a resistance material in contact with a portion of the cathode material 2 and having suitable means such as an impulsing transformer II to produce impulses for initiating a cathode spot on the normally liquid cathode 2.

In order to maintain the cathode spot, a keepalive electrode I 2 of suitable material is placed above the cathode surface in the vicinity where it is desired to maintain the cathode spot. Also in the vicinity where it is desired to maintain the cathode spot is a vertically-extending conductor l3 preferably insulated from the cathode material by suitable high-temperature insulators I 4.

When a single keep-alive electrode I2 is utilized, it is usually desirable to impress a substantially direct-current, keep-alive potential on the keepalive electrode l0. Also, it is desirable to maintain a substantially uni-directional current in the vertically-extending conductor i3.

The current connection to the keep-alive electrode l2 may be completely separate and distinct from the conductor l3 and such connections may be at times most desirable. When separate supply connections are provided for the keep-alive electrode [2 and for the conductor l3, the current in the upward direction in the conductor I3 is adjusted to attract the cathode spot into the vicinity of the conductor I3.

I have found very satisfactory results may be obtained by mounting the keep-alive electrode I2 on the vertical conductor I 3 and providing means for maintaining two substantially inde pendent currents in the vertical conductor I3.

I prefer to maintain these separate currents by providing current-limiting means l8 in the return connection Hi from the keep-alive electrode I2 and in a return connection H from the vertically-extending conductor I3. Preferably, these current-limiting devices l8 are impedances connected in series with the various currents.

As a specific example of a supply system, I have shown a transformer 2|] energized from an alternating-current source (not shown), supplying potential through a full-wave rectifying device 21, the positive connection 22 of which is connected to the vertically-extending conductor l3. Mounted on this conductor I3 is the keep-alive electrode l2 and also connected to this conductor is a separate return connection IT.

The currents flowing in the keep-alive circuit ductor I3 is adjusted to attract the spot closely 1 in the vicinity of the conductor I3. Since they cathode spot is found to move in a direction reverse to the direction in which 'a conductor would tend to move, it is believed that cur'rentsabove that necessary to attract the cathode" spot should be avoided. Also supplied from the source of alternating current is an impulsing transformer 24 for supplying impulses to the make-alive' electrode I0.

When putting a this "system: into operation, the r: impulsingitransformer':24.-will cause the initiation of a cathode spot by passing an impulse through; the make-alive electrode). The keep-alive electrode IZ-then picks up to thecathode spot andcauses current to flow through the'relay 'which opens the connectionnofthe-*impulsing transformer 24zand maintains-it :out of action so long as the'keepgalive electrode 12 is activated. the event the'keepealivei-arc should go out, the

relay 2 5 their will close,-energizing :the impulsing transformer Mandre-initiating the'cathode spot,

Inorderto maintain a cathode. spot-in a desired region adjacent Z t0"the vertically extending con-- ductor -l3-,a current must travel in theupward direction through, the vertically-extending con-- ductor -l 3 in excess of the current fiowing'through the keep-alive electrode -l2.- In practice the im-' pedances [8 are adjusted so that the proper proportion ofcurrent fiows to maintain the cathode spot, and also current flows upwardly through,

the vertically-extending conductor 13 to increase thelmagneticlfield which-drawsthecathode spot into the immediate vicinity of the upwardly-em tending conductor cl 3.

Inpractice, I have found that an independent or controlled current=of the order of 20 to-30 amperes in-the vertically-extending conductor l3 wassample to maintainuthe cathode spotwithin l the-desired region. vvWhen the current became too small therelwas a tendency for the cathode spot to wander out-ofvcontrol distance andfrequently to extend into the region of the-metallic containeril, while currents-'greaterthan 30 amperes were apparently of no material advantage.

While v forpurposeof illustration I have shown a preferred embodiment of my invention and described my invention to the best of my present I understanding, I wish it 'to be understood that i I am not limited tocthe example or explanations herein. given, and it is apparent-"that many changes and modifications can be made herein without departing from the true spirit of my invention or the scope of the appended claims.

I claim as my invention:

1. In a vapor-electric device having a main anode and a pool-type cathode, an exciting system comprising a make-alive electrode, impulsing means for applying potential impulses to said make-alive electrode for initiating an electron emitting spot on' said cathode, a keep-alive electrode, circuit means for applying potential to said-keep-alive electrode for maintaining said electron emitting spot, a conductor extending upward through said pool adjacent said keepalive electrode andcircuit means for causing current flow in said conductor upward from said pool for anchoring said-electron emitting spot adjacent said conductor.

2. In a vapor-electric device having a liquid cathodey'a spot fixing system comprising a keepalive electrode positioned adjacent the desired location of the cathode "spot; a conductor extend-"- ing throughth'e cathode =at-the desired location 1 of the cathode'spou-a cathode spot initiatingelec trode adjacent thedesired location :of the cathode spot, a circuit for deliveringcathode spotinitiat ing potential to said cathodes'pot initiating electrode, a source of unidirectional current connected to said keep-alive'electrodeto' maintain a 1 keep-alive arc between said ke'ep alive electrode and said cathode-andcir'cuit means forproduc-.

ing an (upwardly directed'currentin said conductor in' excess of the current flowing in' said 3. An exciting systeirnt'foria vapor-electric de-"= vice havinga main (anode-and cathode compris---- ingan electrodefor.initiating'an electron emitting condition on said5cathode; a second electrode for maintaining saidelectron emitting condition; connections for impressing a 'potentialfimpulse on said first electrod'eya source of substantially constant potential connected to said second electrode, a conductor extending :throughthe cathode in the vicinity ofthesecond electrode; circuit I means for causing-a current to'flow in saidconductor independent ofthe current for maintain-- ing the emitting-condition ofs'aid-cathodep 4. Ina vapor-electricdevice having a vaporizable cathode, a conductor extendingthrough said cathode at a predetermined-position therein, a keep-alive electrode spaced from the surface of the cathode" in the immediate vicinity of-said-coIh' ductor, a source of unidirectional potential and connections for maintaining an exciting-arc be-" tween said cathode and said keep-alive electrode and connections for maintaining a current in said conductor, said currenthaving a direction oppo site to and of greatermagnitude-thanthe keep-,---

alive arc current.

RICHARD L.-LONGINI.

No references cited.-.

Images