US2964664A - Electric discharge device - Google Patents

Description

De 13 1960 T. A. solLEAU, JR

ELECTRIC DISCHARGE DEVICE Filed Sept. 3, 1958 nu hun 1.

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|NvENToR TRAslMoNo A. so|LEAu,JR. mwen? against ce Patented Dec.. 13, 1960 ELECTRIC DISCHARGE DEVICE Trasimond A. Soileau, Jr., Owensboro, Ky., assignor to genlral Electric Company, a corporation of New Filed Sept. 3, 1958, Ser. No. 758,827

8 Claims. (Cl. 313-43) My invention relates to electric discharge devices and pertains more particularly to electric discharge devices of stacked construction.

This invention represents an improvement in the construction of ceramic tube types, certain forms of which are disclosed and claimed in my copending application for Electric Discharge Device and Methods of Manufacture, Serial No. 711,982, filed January 29, 1958, and assigned to the assignee of this application.

Ceramic materials used in the fabrication of tubes of the type disclosed in my above-noted application are capable of withstanding relatively high ambient as well as steady-state operating temperatures. Such tubes using ceramic construction have been operated successfully at ambient temperatures of the order of 400 C. It has been observed, however, that such ceramic materials are caused to fracture, rendering the tube inoperative, when exposed to thermal gradients as high as 40 C. per centimeter. Many ceramic bodies fracture upon exposure to thermal gradients of even leser magnitude.

Ceramic tubes designed for operation at relatively high power levels are normally subject to relatively high thermal gradients during each warm-up period since large quantities of heat are generated at the anode region of the tube, causing the ceramic body portion adjacent the anode to rise quickly. The cathode region of the tube is at a relatively low temperature shortly after operation of the tube is begun, and in view of the low thermal Conductivity of the ceramic material, excessive thermal gradients are established therein.

jf Accordingly, a primary object of the present invention is to provide new and improved electric discharge devices of ceramic construction.

Another object of the present invention is to provide 'new and improved ceramic tube construction wherein the establishment of excessive thermal gradients in the body of the ceramic is avoided, thereby to permit operation of such tubes at higher power levels.

Another object of the present invention is to provide Further objects and advantages of my invention will become apparent as the following description proceeds and the features of novelty which characterize my invention will be pointed out with particularity in the claims annexed to and forming part of this specification.

In carrying out the objects of my invention l provide a ceramic and metal electric discharge device structure including alternate ceramic annular wall sections and metal contacts. Secured to the anode electrode of the device is a heat-conductive and radiating member or hood that is adapted to envelop or enshroud a substantial part of the device over its entire length, whereby a low-resistance heat path is provided from the anode causing the temperature of the hood to rise rapidly and to radiate heat energy uniformly over all parts of the ceramic. In this maner, all the ceramic parts are heated uniformly, thereby minimizing the establishment of excessive thermal gradients thereacross.

For a better understanding of my invention, reference may be had to the accompanying drawing in which:

Figure l is an elevational view, partly in cross section, of a ceramic and metal tube of stacked construction manufactured'according to the present invention; and

Figure 2 is an exploded view, in perspective, of the device of Figure 1 showing one embodiment of my invention.

Referring to Figure l, there is shown an electric discharge device generally designated 1 and of stacked construction including alternate insulative and conductive elements. The device may be of the type illustrated and claimed in my above-noted application for patent, and, as therein disclosed, is formed with insulative elements that comprise a pair of coaxial cylindrical ceramic wall sections 2 and 3 and a ceramic disk 4. The conductive elements can comprise, for example, titanium electrode contacts including disk-like anode, grid, and cathode contracts 5, 6 and 7, respectively, and a pair of striplike filament contacts 8. These contacts can include prong-like connectors 9 extending, as shown in Figure 2, from one side of the device to enable connection in a suitable circuit, as by insertion in suitable apertures in a printed circuit board. Additionally, on each side of the connectors 9, each of the contacts 5, 6 and 7 is provided with straight edges which facilitate mounting of the device on a planar surface such as that of a printed circuit board (not shown).

The anodecontact 5 is suitable sealed, as by brazing, across the open end of the upper ceramic cylinder 2. Integrally formed with or brazed to the inner surface of the contact 5 is a cylindrical anode stud or block 10 including a planar active surface 11. The contact 6 is washer-like or apertured and is suitably sealed between the ceramic cylinders 2 Iand 3. The manner in which this contact is electrically connected and mechanically associated with the grid structure is described in detail in my above-noted application and is accordingly not repeated here. The contact 7 is similar to the contact 6 and is suitably sealed between the ceramic cylinder 3 and the ceramic disk 4. By -means not shown, the contact 7 is mechanically and electrically connected to a cathode support sleeve 12 which carries a planar cathode element 13 in substantially parallel relation to the planar anode surface 11. The contacts 8 are sealed to the outer end surface of the disk 4 and are suitably electrically connected to the opposite ends of a lamentary heater (not shown) disposed in the cathode sup-port 12.

Disposed between the anode and cathode is a grid electrode 14 including a planar array of wires, which can be a wire mesh and a shallow frusto-conical washer or cupped element 16. A thin metal tab 17 made from nickel-iron-cobalt alloy or other suitable material is interposed between the grid and upper ceramic cylinder 2 and spot welded at the outer edge to the inner edge of the grid contact 6 for thereby electrically connecting the grid and grid contact. The wire mesh grid 14 is adjacent the anode block and the smaller annular edge of the washer 16extends toward the cathode. The mesh 14 extends tautly across the washer and is secured at the edge thereof by brazing to the larger annular edge of the washer 16. This grid may also be of the same consrtuction as that shown and claimed in my above-noted copending application. Inasmuch as the foregoing features of the device 1, in and of themselves, form no part of the present invention, and are here disclosed as exemplary of the type of ceramic tube construction to which my invention may be adapted, a fuller description of these features is not deemed necessary.

For minimizing the establishment of excessive thermal gradients in the ceramic members 2, 3 and 4, l provide a heat conductor and radiator in the form of a hood comprising a substantially U-shaped body 18 having a substantially flat end wall 19; The hood is preferably of aluminum or copper or other good heat-conduction material and coated with any suitable material, such as a colloidal solution of graphite, to provide good radiative properties therefor. Such a solution is commercially available under the name of Aquadag The axial dimension of the hood is selected to correspond to that of the device 1 so that the ceramics 2, 3 and 4 are substantially enshrouded thereby. The length of the leg portions of the U-shaped body is selected to correspond to that of the contacts 5, 6 and 7 above the prongs 9, so that when the device 1 is plugged into a printed circuit board or the like, the free edges of the leg portions are flush with the board surface and the straight edges of contacts 5, 6 and 7. The hood is attached to the anode terminal plate and anode block at the central portions thereof at which, during operation of the device 1, the principal source of heat is located. Attachment of the hood to the device may be by any suitable means, here shown, for example, as screw member 20 which passes through opening 21 in an inwardly directed boss 22 centrally formed in wall portion 19 and is received in a threaded axial opening 23 in anode stud 10.

It will be noted that the flat wall portion 19 of the hood is maintained in spaced relation to the anode-terminal 5 by means of the inwardly directed boss.

To ensure a high conductivity path for heat from the anode stud relative to the heat path from the anode stud to the anode ceramic 2, an annular groove 24 is formed in the anode terminal member 5, which groove functions as a heat block to reduce or minimize the conduction of heat to the ceramic 2. An alternate method is to use a suiciently thin electrode 5 to provide a high heat-resistant path between the anode stud and the ceramic 2. The major portion of the heat developed at the active anode surface 11 is thus conducted directly to the hood, which by virtue of its excellent heat conductivity is quickly elevated to a relatively uniform high temperature and radiates heat substantially uniformly over the entire length of the device 1. In this manner each of the ceramic members 2, 3 and 4 is caused to become heated at relatively uniform and constant rates, thus obviating the production of thermal gradients.

It will be noted that the hood also operates to prevent undue heating of the anode block 10 inasmuch as it provides increased heat radiating and convection area to direct large quantities of heat away from the device. Fracture of the ceramic members is avoided by the hood construction, as above described, in view of the heat shunting effect provided by the hood whereby the anodegenerated heat energy is caused to by-pass the anode, grid and heater ceramics 2, 3 and 4 so far as heat conduction is concerned, the heat energy being caused by radiation from the hood to be directed toward and absorbed by the ceramics in uniform and constant amounts.

While I have shown and described a specific embodiment of my invention, I do not desire my invention to be limited to the particular form shown and described, and I intend by the appended claims to cover all modications within the Spirit and scope of my invention.

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

1. An electric discharge device comprising an envelope containing longitudinally spaced anode, grid and cathode electrodes, longitudinally arranged insulator members interposed between said electrodes and forming portions of the wall of said envelope, means associated with said anode electrode to define a low-heat-conductivity path between the anode and the insulator member next adjacent thereto, and heat conducting and radiating means connected to said anode electrode and disposed substantially to envelop said insulator members between said anode and cathode, whereby to dene a high-heat-con ductivity path from said anode and to radiate said heat uniformly over said insulators thus to minimize the establishrnent of thermal gradients in said insulator members.

2. An anode assembly for an electric discharge device comprising a substantially disk-shaped conductive member having a centrally-disposed stud defining an active electron-intercepting surface, means in said disk-shaped portion defining a heat block from Asaid active surface, and a hood structure connected at said stud and adapted to provide a high-heat-conductivity path therefrom.

3. An electric discharge device comprising an envelope `containing spaced anode, grid and cathode electrodes,

longitudinally arranged annular insulators comprising wall sections of said envelope and having said electrodes extending therein, and a hood structure connected at said anode electrode and substantially enveloping said insulators between said anode and cathode, said hood structure being disposed to receive heat energy from said anode and to radiate said heat uniformly over said insulators.V

4. An electric discharge device comprising an envelope containing longitudinally spaced anode, grid and cathode electrodes, longitudinally arranged annular insulators comprising wall sections of said envelope and having said electrodes extending therein, and a hood structure connected to said anode electrode and comprising a substantially U-shaped body portion substantially enveloping said insulators between said anode and cathode, said hood structure being spaced from said insulators and adapted to receive heat energy from said anode by a high-conduction path and to radiate said heat uniformly over said insulators.

5. An anode assembly for an electric discharge device, comprising a substantially disk-shaped conductive member having a centrally-disposed stud defining an active electron-intercepting surface, and a hood structure connected at said stud and adapted to provide a high-heat-conductivity path therefrom, said hood structure comprising a substantially planar end wall in juxtaposition to said stud, and a substantially U-shaped body portion extending from said end wall.

6. An electric discharge device, comprising a cylindrical envelope, spaced anode and cathode electrodes within said envelope, a stacked array of insulators forming wall sections of said envelope and having said electrodes extending therein, electrode terminals projecting exteriorly of said envelope and terminating in a common plane, and heat radiating means at said anode electrode and extending in spaced relation to said insulators between said anode and cathode electrodes, said radiating means in.- cluding a substantially U-shaped member having leg pot"- tions extending to said common plane.

7. An anode assembly comprising a planar conductive member having a portion defining an electron-interceptingv region, and a heat radiating structure connected to said member and adapted to provide a high heat-conductivityl path therefrom, said radiating structure comprising planar end wall in juxtaposition to said member and a` cup-shaped body portion extending from said end wall. 8. The assembly as defined in claim 7, wherein said body portion is formed with a pair of free edges to provide an opening bounded by an edge of said end wall and said pair of free edges.

References Cited in the le of this patent UNITED STATES PATENTS OTHER REFERENCES Kohl: Materials `Technology for Electron Tubes, Reinhold Pub. Corp., New York, 1951, pages 417-420.

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