US2473833A - Gaseous discharge device - Google Patents

Description

June 21, 1949. P. w. STUTS MAN GASEOIjS DISCHARGE DEVICE 7 Filed Jan. 9, 1946 am 5 a 5 Patented June 21, 1949 OFFICE GASEOUS DISCHARGE DEVICE Paul W. Stutsman, Needham, Mass., assignor to Raytheon Manufacturing Company, Newton,

Mass., a corporation of Delaware Application January 9, 1946, Serial No. 639,974

3 Claims. (Cl. 176-122) The present invention relates to gaseous discharge devices. and more particularly to such devices employing a hot cathode and a control electrode.

The main object of the present invention is to provide a device of the character described having an electrode'arrangement presenting such a discharge path that will permit the use of rela- 2 trode l5. This arrangement serves to isolate the support l6 from the other electrode supports.

The surface 1 of said starting electrode I may be activated or deactivated and the reasons for such treatment will be discussed hereinafter. A

second shield l1, electrically conductive but of tively high gas pressure and as a result provide high current-handling capacity.

These and other objects of the invention will become more apparent as the detailed description thereof progresses, and are obtained, briefly, in the following manner:

-In apreferred embodiment of this invention there is provided an envelopecontaining an ionizable atmosphere at a relatively high pressure, for example, between 1 mm. and 1 atmosphere.

' Disposed in said envelope is a plurality of electrodes, at least a cathode, a starting electrode, and an anode. The cathode is so shielded from the anode, and the path therebetween is of such configuration that, in the absence of ionization of the atmosphere over an appreciable length of said path, no discharge can take place. However, the anode is so disposed with respect to the starting electrode that upon initiation of a discharge between these elements, the above mentioned cathode-anode. path becomes appreciably ionized, whereby a main discharge between said lastnamed electrodes can take place.

' The single figure of ,he drawing illustrates the structural aspects in partial cross-section of one embodiment of the invention and the space relation of the elements therein together with a circuit employing this invention.

Referring now more in detail to the drawing, there is illustrated an evacuated glass envelope 9 containing therein a shield l0, preferably of dielectric material, supported on a press l2 by means, which may be a metallic band ll, encirsmaller dimension than the control electrode l5 and electrically insulated therefrom, is positioned within the lower portion of saidfirst shield member III. This secondshielding member I! is so positioned within said first shielding member l0 that said'second shielding member I! extends an appreciable distance within thestarting electrode l5. supported by a metallic member l'la, said member being embedded in the press-l2. Anode ill,

for example a metallic rod, is disposed within said second shielding member I'L'the upper end of said anode l8 extending an appreciable distance. above the upper portion of shielding member IT. The assembly comprising second shieldcling the lower portion of said shield l0 and being attached to supporting member l3, said member being attached to cathode support 2 I. Positioned within said shielding member l0, and being substantially flush with the top thereof, is an electrically conductive starting electrode I5 extending a predetermined distance downwardly into said shielding member l0. Starting'electrode i5 is supported by an electrically conductive member t5, the lower end of said member being embedded in the press l2 and then threaded.longitudinally, through the wall of member l0 to extend an appreciable distance thereabove, the extended end 8 being attached to theupper'rim of elecing member II -support l'la and .anode' I8 is enclosed within aglass cylinder l I, and made a part of the press I2 in this particular mlg odi ment. This arrangement serves to isolatflo mentioned elements from the electrode supports i6, 2| and 22. The upper rim of said glass cylinder II is substantially flush with the top of second shielding member l1. Positioned within envelope 9, and exteriorly of shielding member I0, is a thermionic cathode l9 supported on conducting members 2i and 22, said members being embedded in thepress l2.

To assure more stable operation of this device it is desirable to activate the'inner surfac 1 of starting electrode l5 by depositing thereon an electron-emissive material, or said electrode may be thoroughly deactivated, for example, by car,- bonizing the surface thereof. In either case, the proper preparation of the electrode l5 produces a stable operation when said electrode functions as a cathode as will-be explained below.

Referring to the drawing, wherein is illustrated ing electrode l5. Controlling the amount of potential-to be impressed on said star-ting elec-. trodelS, andinterposed between said potential source 20 and said electrode I5, is a potentiometer 22, the movable contact 22a of said potentiometer being connected through a high impedance 23 thence through conductor 24 and support It to electrode ii; A positive potential, supu plied for example by battery 2b, is applied to Said second shielding member I! is I other source of potential, through conductors 29 and 30 which are connected to the cathode supports 2| and 22. Connected in series between the anode conductor 21 and the ground 3| are a condenser 32 and load 23. The purpose of these two components will be explained hereinafter.

A potential is impressed on shielding member H from the battery 25 and interposed between said source of potential 25 and the member I! is a potentiometer 35 for controlling the value of said applied potential, the current being conducted to the shielding member I! through conductor 34.

Assuming the device is in a non-conductin state and condenser 32 is charged with a positive potential from the battery 25, through the resistor 26, the potential represented by the charge on said condenser will, of course, be also impressed on the anode IS. The potential or bias on the starting electrode I5 is adjusted so that, at a predetermined value thereof, a sufficiently high potential between electrodes i5 and IE will be caused to exist. A breakdown will occur between the anode l8 and starting electrode l5, resulting in a' glow discharge within the starting electrode space, said glow discharge causing ionization to take place over an appreciable length of the path between the anode l8 and cathode l9 and an arc struck therebetween. As a result of the conducting state so established, condenser 32 will discharge through the load 33, and the potential on the anode I8 will drop to a value which'will extinguish the are between the anode l8 and cathode I9. Now, the cycle will start all over again, the time of said cycle being determined by the value of resistor 26, condenser 32 and load 33. The resulting pulsing current impressed across the load 33 may be used for many purposes known to those versed in the art. The values of the resistor 26, condenser 32 and load 33 are selected to work with the tube constants and therefore perform the necessary external functions. These constants involve ionization, deionization time, and the voltage drop in the tube.

Referring to the statement hereinbefore made regarding the application of a potential on the shielding member H, the purpose of applying such a potential on said member I! is to circumvent the possibility of said member I! acquiring random potentials by reason of its position in the electrical field present in the anode l8-starting electrode l5 space. Such an arrangement provides more stable operation of the device.

A novel feature of this invention resides in using the glow discharge which takes place between anode and starting electrode to initiate an arc discharge between the anode and cathode in a thyratron type gaseous discharge tube employing a thermionic cathode.

Whereas, it is known that a glow discharge between anode and starting electrode is normally to be avoided because it consumes considerable power, shortens the life of the device and tends to alter the operating characteristics thereof, the present invention advantageously uses this unwanted phenomenon.

If, for example, it is desirable to bring about a glow discharge based on a predetermined potential between two electrodes, it has been determined that. to maintain said predetermined polength of the path therebetween, no discharge can tential constant, the surface of the electrode must be treated so that uniform emissivity occurs over the entire working surface of said electrode.

Failure of any part of said surface to be uniformly emissive results in a change of potential necessary to bring about a glow discharge. Therefore, it has been concluded that coating the inner surface of starting electrode 15 with an electron-emitting material will provide the desired stability of operation necessary in the present device. Furthermore, coating the electrode in the manner described will reduce the required starting potential. If on the other hand it is desirable to increase the forward voltage requirements, the inner surface of said electrode may be deactivated, for example, by carbonizing same uniformly. Either method of treating electrode l5 will provide stability of operation.

The advantage to be gained by the use of this device over the usual thyratron type tube resides in the arrangement of the electrodes which permit operation at much higher internal pressures than are ordinarily practicable. This feature has the added advantage of heavier current capacity without undue wear when used in connection with a thermionic cathode. A further advantage is the use of smaller envelopes made possible by the novel arrangement and spacing of the electrodes and elements of the device.

In actual tests, tubes made according to this invention have operated successfully at relatively high pressures and were capable of handling very high peak currents. Even under these conditions, the cathode surface showed remarkable wearing qualities.

While what has been described is but one embodiment of this invention, it is understood that various changes will suggest themselves to those skilled in the art; for example, the shielding member In may extend an appreciable distance beyond the upper rim of the starting electrode l5 and therefore permit utilization of the device where operating requirements call for a greater forward voltage on the'anode. Therefore, this invention is not limited to the details herein described, and other objects and advantages of the present invention will readily occur to those skilled in the art to which the same relates.

What is claimed is:

1. A gaseous discharge device comprising: an envelope containing an ionizable atmosphere; a cathode, an anode, and a starting electrode disposed in said envelope; a dielectric sleeve surrounding said anode and starting electrode; said starting electrode and said anode being disposed adjacent each other; and a second dielectric sleeve surrounding said anode and disposed intermediate said starting electrode and said anode.

2. A gaseous discharge device comprising: an envelope containing an ionizable atmosphere; a cathode, an anode rod, and a cylindrical starting electrode disposed in said envelope; a dielectric sleeve surrounding said anode rod and starting electrode for so isolating said cathode and anode rod from each other that, in the absence of ionization of the atmosphere over an appreciable take place; a cylindrical shield partially surrounding said anode rod and shielding said anode rod from a portion of said starting electrode, a

second dielectric sleeve partially enclosing said cylindrical shield and anode rod, said anode rod being at least partially disposed within said cylindrical starting electrode whereby, upon initiation of a discharge between said starting electrode and anode rod, the atmosphere over an appreciable length of the path between said cathode and anode becomes ionized and an arc may be struck therebetween.

3. A gaseous discharge device comprising: an envelope containing an ionizable atmosphere at a pressure between about one mm. and about one atmosphere; an anode rod mounted in said envelope; a cylindrical starting electrode surrounding said anode rod and having one of its ends extending to a point appreciably beyond one end of said anode rod; a cylindrical shield surrounding said anode rod and isolating all but said end thereof from said starting electrode; a second cylindrical shield surrounding said starting electrode and having one of its ends terminating fiush with said extended end of said starting electrode and its other end extending in the opposite direction an appreciable distance beyond said anode rod; a cathode disposed exteriorly of 20 the said second cylindrical shield whereby in the absence of ionization of the atmosphere over an l 6 appreciable length of the path between the said cathode and anode, no discharge can take place, but upon the initiation of a discharge between said anode and starting electrode, the atmosphere over an appreciable length of the path between said cathode and anode becomes ionized and an arc may be struck therebetween.

PAUL W. STUTSMAN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,784,869 Gray Dec. 16, 1930 1,787,689 Lederer Jan. 6, 1931 2,033,089 Bahls Mar. 3, 1936 2,062,268 Knowles Nov. 24, 1936 2,096,292 Van der Horst Oct. 19, 1937 2,190,079 Meier Feb. 13, 1940 2,331,771 Germcshausen et a1.-- Oct. 12, 1943 Certificate of Correction Patent No. 2,473,833. June 21, 1949.

PAUL W. STUTSMAN It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows:

Column 4, line 54, claim 1, after the Word electrode insert and disposed intermediate said cathode and anode;

and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Ofi'ice.

Signed and sealed this 22nd day of November, A. D. 1949.

THOMAS F. MURPHY,

Assistant Commissioner of Patents.

Images