US2508992A

US2508992A - Electrode assembly for electric discharge devices

Info

Publication number: US2508992A
Application number: US21876A
Authority: US
Inventors: Jr Arthur W Coolidge; Donald S Peck
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1948-04-19
Filing date: 1948-04-19
Publication date: 1950-05-23
Anticipated expiration: 1967-05-23
Also published as: FR984782A; GB672978A

Description

y 1950 A. w. COOLIDGE, JR., ET m.

ELECTRODE ASSEMBLY FUR ELECTRIC DISCHARGE DEVICES Filed April 19, 1948 Inventors:

w w k C F OD. 5 d m u nO JWUID 0% Their Attorney.

potential. an improved assembly of electrodes which mini- Patented May 23, 1950 ELECTRODE ASSEMBLY FOR ELECTRIC DISCHARGE DEVICES Arthur W. Coolidge, Jr., Scotia, N. Y., and Donald S. Peck, Allentown, Pa., assignors to General Electric Company, a corporation of New York Application April 19, 1948, Serial No. 21,876 I 4 Claims.

The present invention relates to an improved electrode assembly for controlled electric discharge devices, particularly devices of the type employing an ionizable medium, such as a gas or vapor.

In the operation of discharge devices of this character, the initiation of conduction between the anode and cathode is determined by the voltage of the control electrode or grid. Once conduction has started, the grid exercises no further control and conduction continues until the anode-cathode voltage is reduced to zero or reverses. It is essential to the successful application of discharge devices of this type that the control member or grid regain its ability to prevent the initiation of discharge in a very short interval of time after conduction has terminated as. a result of the anode voltage having been reduced to zero or made negative with respect to the cathode voltage. The reliability of the control effected by the control member or grid may be improved by preventing the control member from becoming contaminated with material sputtered from the cathode during operation of .the device. Maintaining the grid at a reasonably low operating temperature also minimizes the tendency of the grid to emit electrons and produce ionization which in turn results in loss of effective control by the grid. Adequate shielding of the anode and close spacing of the electrodes also prevents undesirable long-path discharges between the anode and an electrode of lower The present invention contemplates mizes the possibilities of loss of control by the control member by proper control of the above factors which tend to produce unreliable action of the control member. The over-all effect of these features is to provide a tube of high voltage rating at a relatively high gas pressure and a minimum of clean-up or absorption of the gas during operation. The invention further contemplates a structure which is readily assembled and in whichthe relative spacings of the various components, such as the anode, shield members,

and control grid are positively maintained in a provide an'improved electrode. assembly for a gaseous discharge device in which the anode, control grid, and shield member are all positively positioned with respect to one another in a unitary assembly.

Further objects and advantages of the present invention will become apparent as the following description proceeds, reference being had to the accompanying drawing, and its scope will be pointed out in the appended claims. In the draw ing Fig. l is an elevational view in section of a preferred embodiment of our invention, and Fig. 2 is a sectional view taken along the line 2-2 of Fig. 1.

Referring now to the drawing, we have shown our invention embodied in a gaseous electric discharge device of the shielded-grid type and comprising an envelope i including a stem or header 2 sealed to the lower end thereof and an inwardly directed stem 3 at the opposite end. The header 2 includes a plurality of support and lead-in conductors 4IU, inclusive, which are associated with various ones of the electrodes as will be described more in detail at a later point in the specification. The header also includes an exhaust tubulation (not shown) preferably located centrally between the cylindrical array of lead-in conductors 4-!0.

The cathode of the device is provided by an edgewise wound ribbon [2 of suitable material such as nickel which is coated with a suitable electron emission enhancing material such as a. mixture of alkaline earth oxides or a compound of'one of these oxides and nickel, such as barium nickelate. The cathode I2 is in the form of a helical spiral which is supported at opposite ends by conductors l3 and M which are electrically connected to and supported from lead-in conductors Ill and 4 respectively. Additional support for the cathode is provided by a pair of transverse stub conductors l5 extending into opposite ends of an insulating sleeve it which extends through the spiral l2. A generally cylindrical metallic heat shield I! for conserving heat energy supplied to the cathode is supported from the conductors I3 and I4 in insulated relation with respect thereto. The support is accomplished by the flanged eyelets l8 which are bonded to the conductors l3 and M on opposite sides of the closed end l9 of the heat shield 11. The eyelets I8 and conductors l3 and M are insulated from the heat shield by insulating sleeves 20 and insulating spacers 2| arranged between opposite sidesofth'eend'of'the heat shield and the eyelets l8. ,Conductor 22 is connected with themid-point, of, the cathode i2 and through and anode.

conductor 22' to lead-in conductors 5 and 1 so that the cathode may be utilized as two sections in parallel by bringing out all three terminals if desired.

The control member or grid 23, the anode 24 and shielding conductors 25, 25, and 21 form a part of a unitary assembly which is supported from the header 2 by three

conductors

28, 29, and 30 which are connected respectively at their lower ends with lead-in conductors 6, 8, and 9. The electrodes 23-21, inclusive, are provided with suitable openings through which pass the conductors 2830, inclusive. The electrodes are maintained in insulated relation with respect to conductors 28-30 and with respect to one another by insulating sleeves 3| and insulating spacers 32 which are interposed between adjacent ones of the electrodes 23- -2! and between the electrodes and the flanged eyelets 33 which are spot-welded to the conductors 2830 at Opposite ends of the electrode assembly. Suitable metal shields or sputter cups 32' are positioned between the insulating spacer and extend longitudinally to prevent the deposit of foreign material from depositing on these spacers which would tend to reduce their surface resistors.

All of the electrodes 23-21 are formed of sheet metal punchings and have a generally planar central portion. The control grid 23 is provided with a central opening 34 which is spanned by a plurality of parallel transverse conductors 35. These conductors may be formed integrally with the marginal portion of the grid structure or, as

illustrated, punched from a separate washer. A depending circular flange 36 extends from the .outer edge of the grid in fairly close proximity to the inner wall of the envelope I and provides a heat radiator for the grid structure.

Shield members

26 and 21 have circular flanges extending upwardly from the outer edges thereof and bonded together at their extremities to form a unitary box-like shield structure enclosing the anode. The member 26 is provided with a centrally located aperture 31 to allow for the passage of the discharge to the anode. The upper shield member 21 is provided with a central opening 38 to receive the glass stem 3 of the envelope. The clearance space between the shield member 21 and the glass stem is electrically closed by a mesh washer 39 which is bonded to the shield member 21 around the opening 38. The other cup-shaped shield member 25 is supported between the control member 23 and the cathode with a downwardly directed flange 40 extending in spaced relation with respect to the radiating flange 3B of the control member. This shield member prevents material sputtered from the cathode l 2 from depositing on the grid structure. The shield member 25 is likewise provided with a centrally located aperture 4| to allow for the passage of the discharge between the cathode A means for aligning the electrode assembly and the envelope during manufacture is provided by a plurality of resilient fingers 42 which are secured to the radiator flange 35 of the control grid and which extend downwardly and into resilient engagement with the inner wall of the envelope.

As illustrated, the lead-in terminal for the anode extends through the glass stem 3 and terminates in a metal terminal 44 which is cemented in position on the top of the envelope. It will be appreciated that the envelope and conductor 43 are hermetically sealed in the region where the conductor extends from the envelope. The shield structure including members 25 and 21 is connected with conductor 28 by a conductor 46, the shield member 25 is connected with the conductor 29 by conductor 4? and the heat shield I! is connected with conductor 28 by conductor 48. The control grid is electrically connected with conductor 30 by a conductor 49.

The discharge device is completed by a base including a metal shield 49, including a ceramic disk 50 at its lower end which supports a plurality of contact prongs 5|. While as many prongs as desired may be provided, four prongs are commonly used on devices of this character. In the embodiment of the invention illustrated, the two lead-in conductors 5 and I which are connected. to the midpoint of the cathode 12 by conductors 22 and 22' are brought out to a single terminal prong. The lead-in conductors 4 and iii connected with the ends of the cathode [2 are brought out to a second of the terminal prongs, thus providing terminals for supplying energy to the two halves of the cathode in parallel. The control grid connected with conductor 30 by conductor 49 (Fig. 2) is brought out to another of the contact prongs and in the particular embodiment illustrated, the fourth contact prong is electrically unconnected with the tube elements. In order to establish a point of voltage intermediate the voltage of the two contact prongs connected to the cathode,

resistors

52 and 53 are connected between the

conductors

5, 8 and 8, 10. The conductor 8 connects with the conductor 29 and in this way connects the

shield members

25, 28 and 2! with the point of intermediate voltage with respect to the supply terminals of the cathode l2. The

resistors

52 and 53 are each preferably in the order of 10,000 ohms.

In the assembly of the discharge device described above, it will be appreciated that the anode, control grid, and shield electrodes are all mounted on the conductors 28-30, inclusive, to form a unitary assembly which along with the cathode and cathode heat shield assembly are supported on the stem or header 2 of the tube. This assembly may then be inserted in the envelope with the anode conductor 43 extending through a passage in the anode stem 3. The envelope is then sealed around the conductor 43 and the rim of the header '2 prior to exhaust which is accomplished through the exhaust tubulation II.

The present invention is particularly applicable to discharge devices employing a gas or vapor and devices built in accordance with our invention have been charged with an inert gas, such as xenon, to a pressure in the order of -150 microns. The construction has resulted not only in a device which is readily manufactured and in which the parts may be readily produced as punch press operations, but also one in which spacings and relative positioning of the various parts is easily controlled with a high degree of accuracy. The relatively complete shielding of the anode by the box-like shield structure prevents any long-path discharges terminating on the anode. The control member is likewise adequately shielded from the cathode and is provided with a radiator which helps to maintain the temperature sufliciently low to minimize emission by the grid. All of these factors cooperate to provide a device which exhibits extremely reliable control characteristics and permits application of the tube to circuits where the deionization time during which the control member must regain control is very short. The tube is relatively free from gas clean-up during life.

While we have described and claimed a particular embodiment of our invention, it will be apparent to those skilled in the art that changes and modifications may be made Without departing from our invention in its broader aspects, and we aim, therefore, in the appended claims to cover all such changes and modifications as may be made without departing from our invention.

What we claim as new and desire to secure by Letters Patent of the United States is:

1. An electrode assembly for an electric discharge device comprising a stack of conducting electrodes including a shield, a control member, a shield, an anode, and a shield mounted in the order named, said electrodes each including a generally planar portion and the first three of said electrodes including an opening for the passage of an electric discharge, insulating spacer means positioned between adjacent electrodes of said assembly and located outside the area of the openings in said electrodes, elongated supporting means extending through said electrodes and Spacer means and. means engaging the outer electrodes of said assembly for maintaining them in assembled relation.

2. An electric discharge device of the gaseous type comprising an envelope including a stem at each end, a plurality of electrodes positioned within said envelope and including a cathode supported from one stem and a stacked electrode assembly supported from both stems, said stacked electrode assembly including an anode, a control member, and a plurality of shielding electrodes positioned respectively on opposite sides of said anode and between said control member and said cathode, insulating spacing members positioned between the electrodes of said stack and located outside the area of said openings, a plurality of elongated supporting means supported from said one system and extending through said electrodes and insulated therefrom by said insulated spacing members and fastening means for securing the electrodes of said assembly together.

3. An electrode assembly for gaseous electric discharge devices comprising a generally planar anode member, a shield structure for said anode substantially enclosing said anode except for a discharge receiving opening on one side thereof, a control member and a second shield structure positioned in the order named on said one side of said anode, insulating means positioned between the said electrodes and said shielding structures to determine the spacing therebetween and to maintain said members in mutually insulated relation and located outside the area of said openings, a plurality of elongated supporting means extending through said electrodes and insulating means and means for securing said electrodes and shield structures in assembled relation.

4. An electrode assembly for gaseous electric discharge devices comprising a generally planar anode member, a shield structure for said anode member including a discharge receiving opening on one side of said member, a control member and a second shield structure positioned in the order named on said one side of said anode, insulating means positioned between the said members and said shielding structures to determine the spacing therebetween and to maintain said members in mutually insulated relation, a plurality of elongated supporting means extending through said electrodes and said insulating means and means for securing said members and shield structures in assembled relation.

ARTHUR W. COOLIDGE, JR. DONALD S. PECK.

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

UNITED STATES PATENTS Number Name Date 2,044,618 Livingston June 16, 1936 2,064,981 Knoll Dec. 22, 1936 2,112,034 Livingston Mar. 22, 1938 2,292,081 Maser Aug. 4, 1942 2,381,632 Watrous, Jr Aug. 7, 1945 2,399,003 Crapuchettes Apr. 23, 1946 2,409,855 Hillyer, Jr., et a1. Oct. 22, 1946 2,443,205 Stutsman June 15, 1948