US2617956A - High-frequency discharge device - Google Patents

Description

L. U- HAMVAS HIGH-FREQUENCY DISCHARGE DEVICE Nov. 11, 1952 Filed June 27, 1951 Inverfitor Laszl O U. Ham-vas His Attorney ceivers.

Patented Nov. 11, 1952 2,617,956 HIGH-FREQUENCY DISCHARGE DEVICE Laszlo U. Hamvas, Schenectady, N. Y., assignor to General Electric Company, a corporation of New York Application June 27, 1951, Serial No. 233,798

7 Claims.

My invention relates to high frequency discharge device and more particularly to improved discharge devices of the magnetron type.

In certain applications of compact, relatively inexpensive electronic equipment, there is need for a generator of ultra high frequency electrical signals, for example, as in ultra high frequency television receivers or in small ultra high frequency communication transmitters and re- The frequency range of the electrical signals required in such applications includes frequencies of such magnitudes as to be unattainable in a practical sense from oscillators of the type used heretofore for generating cyclically jvarying electrical signals in compact, relatively inexpensive equipment used at lower frequencies.

It has been known that electric discharge devices of the magnetron type will provide the necessary ultra high frequency electrical signals.

However, magnetron devices which are presently known in the art, in generalare, by their sizes, operating voltages, cost, and complexity, prohibited from use in a practical way as oscillating signal generators in applications of the type described.

- It isa primary object of my invention to provide a new and improved electric discharge device of the magnetron type. i

It is another object of my invention to provide an electric discharge device of the magnetron ype which is of simplified and economical construction, easily produced on a low cost, mass production basis.

It is another object of my invention to provide an electric discharge device of the magnetron type which is suited in its simplified structure to be embodied in small sizes and mounted in conventional receiving tube envelopes.

It is still another object of my invention to provide such a magnetron device as described in the foregoing objects which may serve as a generator of ultra high frequency electrical signals such as are required from the local oscillator in an ultra high frequency television receiver or communication receiver.

each having a ring portion and a plurality of elongated elements or digital projections extendin axially therefrom in a circular array and in mutually-spaced parallel relation. To each of the. two ring portions, there is secured a disk of 2 insulating material having defined therein a central opening and a plurality of spaced slots around the opening. The ring portions with the disks secured thereto are mounted in spaced parallel planes with the digital projections from each ring portion interspaced between those from the other ring portion and extending for support into the slots in the disk secured to the other ring portion. Thus, all of the digital projections form a parallel mutually spaced circular array, alternate ones being supported from one ring portion and extendin through slots in the insulating disk secured to the other ring portion. A tubular cathode member is conveniently mounted in centrally located relation within the circular array of digital projections, extending for insulated support through the central openings in the insulating disks. By this structure, the digital projections and the cathode member are easily and economically spaced accurately from one another and firmly supported so that such spacing is maintained.

Conventional means to heat the cathode member may be provided and connected to two of the lead-in connectors; and the cathode member is also connected to a lead-in connector. A permanent magnet is provided around the exterior of the envelope and so oriented as to produce an axial magnetic field within the annular space between the cathode member and the circular array of digital projections. Thus, when the two anode members are connected to an external resonant circuit and a direct current voltage applied between the cathode member and the anode members, the radial electric field therebetween in conjunction with the axial magnetic field permits the device to produce ultra high frequency oscillating electrical signals in a manner of operation well-known in the artof magnetron discharge devices.

The novel features of my invention are pointed out with particularity in the appended claims. For a better understanding of the invention, however, together with further objects and advantages thereof, reference should be had to the following description taken in conjunction with the accompanying drawing, wherein the single figure is an enlarged perspective view of a mag netron discharge device embodying my invention.

In the drawing, I have shown an evacuated and hermetically sealed envelope l, which preferably is generally cylindrical in shape, as shown. Envelope I includes a circular base portion 2, through which a plurality of electrically conductive and relatively stifi lead-in connectors 3-9 are sealed in mutually spaced and insulated relation. The connectors 39 may be conveniently arranged to cooperate with a conventional tube socket, such as is commonly used to support and electrically connect discharge devices, the arrangement shown in the drawing being suited for use with a 7 pin miniature type socket. For a purpose to become apparent hereinafter, envelope I is made of a non-magnetic material. either metal or glass. Base portion 2 is made of suitable insulating material, for instance either ceramic or glass, and sealed at its periphery to the main cylindrical portion of envelope I. An exhaust and seal-ofi' tubulation It may conveniently be located in the upper end of envelope l as shown.

Within envelope i and for practical purposes, entirely supported from connectors 6 and 1, there is provided an electrode structure including two anode members H and [2, a cathode member I3, and two disks Hi and iii of insulating material. Supported from connector 4 so as to form an inductive loop, there is a strip 56 in which a suitable getter material, such as barium, isplaced. After final evacuation and sealing of envelope I, the loop may be excited with radio frequency energy to heat and vaporize the getter material which, as is well known, absorbs residual gases remaining in the envelope.

Directing particular attention now to the electrode. structure of the illustrated device, it will be seen that anode members H and I2 include annular or ring portions ll and 18 respectively which are supported in spaced parallel planes, i. e., in spaced coaxial relation, by welding or other fastening means, preferably from diametrically opposed connectors 6 and I. A plurality of elongated anode elements or digital projections l9 extend axially from ring portion I? in parallel mutually spacedrelation; and a plurality of similar digital projections 23 extend in like manner from ring portion it in opposition to but interspaced between projections it. Together, the plurality of digital projections iii-2i) form a closed array of mutually spaced parallel extending elements which enclose a geometric space, preferably a cylindrical space formed by projections l922l in a circular array, coaxial with the mutual axis of ring portions I1 and I8.

Insulating disks Hi and [5 are mounted upon ring portions ll and it as shown. A simple Way, to accomplish this mounting is provided by a plurality of tabs 2!, spaced around the periphery of ring portions I! and i8 intermediate the points from which digital projections 59 and 20 extend. Before final bending of tabs 2 l, they may be slipped through spaced slots 22 provided in disks [4 and I5; and a quick and simple bending of tabs 21 secures the disks to the anode ring portions as shown. Disks Hi and [5 are also each provided with a central opening 23 and a plurality of mutually spaced slots 2% around the opening therein. It will be obvious that a quick and. economical stamping of sheet insulating material, preferably mice, for example, will provide the disks l4 and $5 with the openings 23, slots 22, and slots 24 therein.

Anode members H and I2 may also be formed bysimple fabricating operations. lanks in the form of a ring withalternate short spokes, to form tabs 2!, and long spokes, to form digital projections 19 or 29, radiating from the peripheries thereof may be punched from sheet metal, preferably non-magnetic metal, as for instance stainless steel. The short spokes may 4 bebent in one direction to form tabs Zl and the long spokes bent 180 degrees in the other direction at their bases, and again 90 degrees at a point radially inward from the ring portions to provide projections l3 and 2%, as shown.

When anode members H and I2 with disks Hi and I5 secured thereto are placed in spaced relation with digital projections l9 and'Ell, interspaced as shown, the free extremities of the digital projections l325 extend through slots 24 in disks i l and i5. That is, alternate ones of the parallel mutually spaced projections zs-zs in circular array are supported between one anode ring portion and the insulating disk secured to the other ring portion. This arrangement is particularly advantageous because the spacings between alternate digital projections are thereby accurately eifected along the whole length of the projections. Further, with digital projections l9 2l supported at both ends as shown, theoriginal spacings aremaintained even though the device be subjected to mechanical shocks or jars. The mutual spac ings of digital projections lt-28 are accurately made and maintained; and the device, therefore, is not subject to microphonic or frequency drift disturbances duringv operation.

Tubular cathode member 13 is supported in insulated and accurately spaced relation within the array of digital projections l3--20 by disks l5 and I5, cathode member l3 extending between disks M and 15 through openings 23 as shown. This mounting arrangement for cathode mem ber 13 has several advantages. First, since the size and location of openings 23 may be ac curately determined when disks is and I5 are formed, cathode member 13 is accurately located within the array of digital projections Iii-4s; this is essential to good operation of the device. Second, cathode member I3 is not only electrically insulated from other components of the electrode structure, but is also thermally insulated since no metallic structure is in contact therewith to conduct heat away; this is an important feature because heating power for cathode member I3 during operation of the device is thereby minimized. Third, the structure and assembling thereof for mounting cathode member !3 are extremely simple and economical, being adapted for production on a mass production basis.

Coated upon the outer surface of cathode member i3, which may be made of nickel, is a thermionically emissive sub-stance 25. for example, bariu-m-strontium oxide, and mounted within cathode member [3 is a suitable heating element 23 which is connected to connectors 3 and 5 as shown to be supplied with heating current. The right end of cathode member 13, not visible in the drawing, is preferably closed by crimping or a suitable cap to reduce heat losses by radiation and is connected to connector 9 by means of a cathode tab 27. Also, as shown in the drawing, a convenient manner of mounting anode members H and I2 is to weld connectors G and 1 respectively to one of the tabs 2| thereon.

Suitable means, sucha an annular permanent magnet 23 having diametrically opposed poles, are positioned externally around envelope l to provide an axial magnetic field in the annular space between digital projections 19-20 and cathode member iii. In order that the magnetic field strength, for a given magnet, in this space, be a maximum and virtually uniform, envelope I and anode members I I and I 2 should be of a nonmagnetic material.

Although the operation of the magnetron device shown and described is conventional and well understood, it'may be briefly described as followstA directcurrent potential difference mak ing anode membersJI and I2 positive withrespecttoicathode member I3 is applied between the anode members II and I2 and cathode member I3 .through a circuit which, in combination with the section of transmission line formed by conductors 6 and 1,.is resonant at a predetermined frequency. With this potential difference which creates a radial electric field, and with a suitable axial magnetic field, between digital projections I9+20 and cathode member I 3, electrons emitted from the heated substance 25 move in curvilinear paths to set up oscillatory fields in the spaces between adjacent digitalprojections, which cause oscillatory electrical signals in the external resonant circuit. High frequency electrical energy may be extracted from the resonant circuit and the frequency ofoperation maybe varied or tuned by changing the circuit parameters in the external circuit. It is understood that the capacitive reactance of the resonant circuit is providedf to a large extent, by the surfaces of closely spaced adjacent digital projections, while the inductive reactance is provided largely by the transmission line formed of connectors 6 and I and the external circuit connected thereto.

A notable feature of the present invention resides in the fact that the insulating disks I4 and I not only serveto securely support and posi tion the extremities of digital projections Iii-23 in mutually spaced and insulated relation, and to insulatably support cathode member I3 in accurately centered relation within digital projections -I3--2II, but also serve as end shields to prevent electrons fromescaping axially out of the spacebetween these members in which the forces of the electric and magnetic fields interact on the electrons; It is known that a considerable number of electrons tend to escape the interaction space'if it is unclosed at its ends, thereby lowering the efiiciency of operation. In the past, metallic end-shields have often been used at the ends of the interaction space to prevent electron escape; these shields were ordinarily maintained at cathode potential and necessarily were mounted in spaced or insulated relation with respect to the anode'jthus adding complexity and cost to the devices in which they were employed. Also, the extra capacitance between the interdigital pro- 'jections and the endshields was undesirable. In accordance with my invention, the insulating disks --serve as end shields. The'emitting substance25' is not extended completely to the insulating disks I4 and I5, as shown in the drawembossments may be provided on cathode member I3 intermediate the ends of the emitting substance 25 and the disks to intercept electrons in their travel toward the disks.

In a preferred embodiment of my invention 6 illustrated by the drawing, the mutual axis of cathode member I3, ring portions I! and I8, and the circular array of interdigital projections Iii-20 is oriented at right angles to the major axis of envelope I. Such an arrangement is pre- 'ferred and advantageous for two reasons.

First, the air gap across which magnetic flux must pass is minimized and a lower strength magnetic source, such as permanent magnet 28, may be employed to produce the same flux density in the interaction space than one needed for any other .i'were positioned with the axis of cathode I3 vertiarrangement. Secondly, connectors B and I which form a transmission line to the external resonant circuit may be made extremely short and equal in length. If, for example, the electrode structure asymmetrical with respect to anode members II and I2 or else a terminal from the top of the envelope would be required.

, From the foregoing, my invention is seen to be an electric discharge device of the magnetron {type which is characterized by extreme simplicity and suited for mass production, even in 1 small sizes. Through the use of insulating disks and the cooperating electrode structure shown and described the array of digital rojections and the cathode member enclosed thereby are accurately spaced and firmly supported while all components of the structure are economical to fabricate and assemble. Furthermore, the device of my invention requires no end shields. as are commonly known, since the insulating disks therein adequately serve also as end shields for found to be very stable in its frequency of operation. It is also tunable, by varying the parameters of the external circuit, over a, wide range I of ultra high frequencies. The electrode structure is easily enclosed in an economical evacuated glass envelope and connected with con- ;nectors extending from the envelope to form a conventional pin-type base.

While the present invention has been described by reference to a particular embodiment thereof, it will be understood that numerous modificaftions may be made by those skilled in the art without actually departing from the invention.

'1, therefore, aim in the appended claims to cover all such equivalent variations as come within the true spirit and scope of the foregoingdisclosure. What I claim as new and desire to secure by Letters Patent of the United States is:

1. An electric discharge device comprising an hermetically sealed envelope, a plurality of elongated anode elements in parallel mutually spaced relation forming a closed array thereof, two

-janode ringportions mounted in spaced coaxial relation within said envelope, two disks of insulating material each secured to one of said ring portions, alternate ones of said anode elements being supported from one of said ring portions and the disk secured to the other ring portion, and a cathode member supported between said disks in accurately spaced relation within said array of said elements.

, 2. An electric discharge device comprising an evacuated envelope, two anode members supported in spaced relation within said envelope, each of said anode members having a ring portion and a plurality of mutually spaced parallel elongated anode elements extending axially therefrom, two disks of insulating material each secured to one of said ring portions, said ring portions being positioned coaxially with the anode elements of each opposed and alternately interspaced with those of the other to form a circular array and extending for additional support through the disk secured to the other ring portion, and a cathode member accurately located and supported Within said closed array of said anode elements by said disks.

3. An electric discharge device comprising an hermetically sealed evacuated envelope, a plurality of elongated anode elements mounted in circular array within said envelope and extending in parallel mutually spaced relation, two anode ring portions supported within said envelope in spaced coaxial relation, two disks of insulating material each secured to one of said ring portions, alternate ones of said anode elements being supported from one of said ring portions and extending for additional support through spaced slots defined in the disk secured to the opposite ring portion, said disks having a central opening defined therein, and a tubular cathode member extending in parallel centrally spaced relation within the circular array of said anode elements and through said openings and supported by said disks.

4. An electric discharge device of the magnetron type comprising an evacuated envelope, a plurality of lead-in connectors extending in sealed and mutually insulated relation from the interior to the exterior of said envelope, two anode members each having a ring portion and a plurality of parallel mutually spaced digital projections extending axially therefrom, said anode members each supported within said envelope from a different one of said lead-in connectors with the digital projections therefrom in opposed parallel interspaced relation, two disks of insulating material each secured to one of said ring portions, said disks having a plurality of spaced slots therein through which the extremities of the digital projections from the opposite anode member extend and having a central opening defined therein, and a cathode member extending between said central openings in said disks for insulated and centered support with respect to said interspaced digital projections.

5. An electric discharge device of the magnetron type, comprising a generally cylindrical hermetically-sealed evacuated envelope including a base portion of insulating material, a plurality of lead-in connectors sealed in mutually insulated relation through said base portion, a plurality of parallel mutually spaced elongated anode elements in circular array, two anode ring portions supported in coaxial spaced relation with the mutual axis thereof perpendicular to the axis of said cylindrical envelope, two disks of insulating material each secured to one of said ring portions and having a central opening surrounded by a plurality of slots therein, alternate ones of said anode elements electrically and mechanically fastened to one of said ring portions and extending axially therefrom through the slots in the disk secured to the other of said ring portions, a tubular cathode member positioned coaxially with said ring portions and centrally within said array of elements and extending through said spaced openings insaid disks, a heating element within said tubular cathode member, and means for providing an axial magnetic field in the space between said cathode member and said array of anode elements.

6. An electric discharge device of the magnetron type comprising a generally cylindrical hermetically sealed evacuated glass envelope including a circular base portion, a plurality of lead-in connectors sealed with mutually insulated relation to said base portion, two anode members each having a ring portion and a, plurality of parallel spaced digital projections extending axially therefrom, said ring portions being supported in coaxial spaced relation within said envelope one from each of two diametrically opposed lead-in connectors with the mutual axis of said ring members and with said digital projections oriented at right angles to the major axis of said envelope and with opposing digital projections mutually interspaced, two disks of insulating material each secured to one of said ring portions and having a central opening and a plurality of mutually spaced slots around said opening defined therein, the free extremity of each of said digital projections extending through one of said slots in said disks, a tubular cathode member extending through said openings in said disks for centrally spaced support with respect to said interspaced digital projections, and an annular permanent magnet having opposite poles diametrically opposed surrounding a portion of said envelope and oriented to provide an axial magnetic field in the space between said cathode member and said interspaced digital projections.

7. An electric discharge device of the magnetron type comprising an evacuated envelope, an insulating base portion forming a part of said envelope, a plurality of lead-in connectors sealed in said insulating portion and extending from the interior to the exterior of said envelope, two anode members each having a ring portion and a plurality of circularly spaced digital projections extending axially from said ring portion, said anode members being mounted within said envelope on a first and a second of said lead-in connectors respectively with the ring portions thereof in parallel spaced relation and the opposed digital projections thereof interspaced between one another intermediate the inner sides of said ring portions, two insulating disks each mounted on the outer side of one of said ring portions and having definedtherein a central opening, and a tubular cathode member surrounded in spaced relation by said interspaced digital projections and extending between said insulating disks and through said central openings, said cathode member being connected to a third of said lead-in connectors.

LASZLO U. I-IAMVAS.

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

UNITED STATES PATENTS Number Name Date 2,144,222 Hollmann Jan. 17, 1939 2,147,159 Gutton et al Feb. 14, 1939

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