US2013419A - Electron discharge device and improved anode therefor - Google Patents

Description

' Sept. 3, 1935. w G MORAN 2,013,419

ELECTRON DISCHARGE DEVICE AND IMPROVED ANODE THEREFOR Filed July 15, 1953 INVENTOR W 6. MOP/71V ATTDRNE Patented Sept. 3, 1935 PATENT OFFICE ELECTRON DISCHARGE DEVICE AND IMPROVED ANODE THEREFOR William G. Moran, Bloomfield, N. J., assignor to Westinghouse Lamp Company, a corporation of Pennsylvania Application July 15, 1933, Serial No. 680,515

13 Claims.

This invention relates to electric discharge devices and more particularly to an improved type of anode therefor. In its more specific aspect the invention is an improvement of the electron discharge device and anode disclosed in the United States application of George M. Dinnick, Serial No. 673,865, filed June 1, 1933, and assigned to the same assignee as the present invention. Said application discloses a three-electrode tube 1 including a grid, an anode and a cathode. The anode comprises a single unitary piece of graphite in the form of ahollow tubular element. The anode surrounds both the grid and filament.

Although tubes containing an anode of .the above character have beenan advance in the art, it was found that some of the tubes were faulty. In the course of my work with these tubes I found that in many cases the shortcomings of these faulty tubes was attributable to the anode. During the normal operation of the tube some of the graphite was loosened from the plate and was transferred in the form of, a loose dustrto the grid and filament, This graphite then formed a thin coating or film on the grid and cathode. 25 The coating or film of graphite on the filamentary cathode increased the thermal emissivity of the filament. Sometimes the increase in the thermal emissivity of the cathode would cause the reduction of the filament temperature to a value below the necessary operating value at normal filament voltage and current.

In order to obviate this difficulty, I have employed a simple expedient which consists in the employment of a material on the anode to entrap any loose dust particles and which will prevent graphite particles from becoming loosened from the anode and being deposited on the filament or grid.

An object of my invention is to provide an improved electric discharge device.

Another object of my invention is to provide an electric discharge device which, during seasoning or normal operations thereof, will not cause an increase of the thermal emissivity of the cathode.

A further object of my invention is to provide an electric discharge device having a graphite anode and which may be seasoned or operated under normal conditions without coating the filament thereof with a film of carbon.

A still further object of my invention is to provide a graphite anode having a protective surface thereon; V

Other objects and advantages of my invention will be readily apparent from the following description and drawing wherein:

Figure 1 represents a longitudinal front view, with some of the parts broken away, of a discharge device embodying my invention;

Figure 2 represents a perspective view of an anode embodying my invention; and

Figure 3 represents a horizontal cross sectional view of Figure 2 taken at about the mid-length thereof.

The electric discharge device, with the exception of the anode, is the same as that illustrated in the above mentioned application. As shown, it comprises an envelope 9 having a re-entrant tube In extending therein. The re-entrant stem 10 has a press in which are secured a plurality of spaced conductors [2, I3 and I4 extending interiorly and exteriorly of said envelope.

A flexible metallic band 15 is wrapped around the-stem l0 below the press thereof and is in frictional engagement therewith by means of a nut and bolt arrangement It. At one side of said press are a plurality of standards H and I8 which are welded to said band [5 and extend upwardly in said envelope. A corresponding pair of standards are secured to said band at the other side of the press. The standards I! and 18 are welded to each other at that position where the standard l8 terminates. The standard I1 has the major portion thereof extending upwardly in said envelope and substantially parallel to the longitudinal axis thereof an appreciable distance above the upper limit of the standard [8.

A cruciform insulator 19, having diametrically disposed openings in one of the cross arms thereof, has the upper portion of the standards I 1 extending through these openings with said cross arm resting upon the upper limit of the standards l8. The other cross arm of the insulator l9 has a plurality of openings therein adapted to accommodate conductors and supports 29, 2|, 22 and 23. A suitably sized wire 24 is wound around and secured to the conductors 20 and 23 to serve as the grid element. An inverted M-shaped filament 25 serves as the cathode element. The filament 25 has its lower bight secured to a conductor, not shown, and its upper bights secured to a pair of hooks 2B and 21. The ends of the filament 25 are secured to conductors 2| and 22. A small carbon shallow disc 28, having a circular opening therein, is mounted on each of the standards IT.

A rigid improved anode 29 surrounds the grid and filament. The main body foundation or base of the anode includes a hollow elongated member consisting of two flat sides 30 of sufficient width and arranged parallel to each other and integral with two curved portions 3! forming the other sides. A cross sectional View of said anode, which is in the form of a hollow shell, at right angles to its major axis, is in the form of a rectangle having rounded ends. At the midwidth of each of said flat sides and extending along the entire length thereof are outwardly extending lateral extensions 32. Each extension 32 is of appreciable cross-sectional area and has an opening therein throughout the entire length thereof. The opening may be cylindrical, as shown, or in the form of a groove.

The main body of the anode, as above described, is a unitary single element composed of graphite or the like. Because of its composition, the anode has a good heat emissivity characteristic, comparable with that of a black body, which is a desirable feature in an anode construction employed in radio tubes. In order that the filament as well as the grid may be protected from being covered with a film of carbon from the anode and so that the anode may still retain its heat-emissivity characteristic, I coat the entire interior surface of the anode with a metal such as copper, nickel, iron, chromium, molybdenum, tungsten, platinum or the like. If desired, I may also coat the upper and lower extreme faces of the body of the anode with one of the above metals.

The coating, designated as 33, is in the form of a thin film which maybe deposited thereon in any suitable manner, as for example, electrodeposition, an oxide paste, deposit and subsequently reduced thereon or by other convenient means. The metal coating 33 is in intimate contact with and serves to coat that portion of the anode which is to be subjected to bombardment so that no graphite dust may be formed and/or transferred to the grid and filament. The coating is firmly adherent to and supported by the anode body and is substantially impervious to any graphite dust that may have been on, the inner surface thereof prior to coating. By limiting the area of coating to only the interior surface and the extreme upper and lower faces of the anode, the heat radiating properties of the effective heat radiating surface of the anode remains unimpaired. V The coated anode may be readily assembled in an electric device by simply sliding the standards I! through the longitudinally disposed openings in the extensions 32 of the anode. The diameter of the openings is substantially the same as that of the standards I1. Small shallow discs 35, the same type as the discs heretofore described, have openings therein through which the upper portions of the standards ll extend so that these discs rest upon the lateral extensions of the anode. A cruciform insulator 36, similar to the insulator l9, also has openings therein adapted to accommodate the standards I'lwhich project therethrough and extend upwardly thereabove.

The insulator 36 has openings adapted to receive conductors 2B and 23 which extend there-.

through. Short cross-bars 31 are welded to the upper portion of the conductor 20 immediately adjacent and above the insulator 36. Acrossbar 37 is also welded to the lower portion of the conductor 23 immediately adjacent and below the insulator l9. Hooks 26 and 27, which support the upper bights of the filament, have the shanks thereof integral with springs which rest in small recesses in the upper face of v the insulator 36,

with the shanks thereof extending through openings in said insulators.

Resting upon the insulator 36 and adjacent the outer portions thereof and welded to each of the standards I? above the insulator, is an. inverted U-shaped rod 38 having the sides thereof welded to the standards I! and [8 at the places where the sides of said U-shapedrods and standards ode having the foundation portion thereof composed of a material having a relatively high heat emissivity characteristic, a metallic coating on that surface of the anode which is bombarded by the electronsemanating from the cathode duringthe operation of the device.

2. An electric device comprising an envelope, an anode andacathode, therein, said anode hav ing a foundation composedof graphite, a metal lic coating located on that surface of said foundation which. is bombarded by. the electrons from the cathode during. seasoning or normaloperation of the device. 7 j V 3. An electric device comprising an. envelope,-

ing a portion of the area thereof facing said an anode and a cathode therein, saidanode hava cathode and a portion of the area thereof facing said envelope, said anode being composed essen tially of graphite, a metallicv coating on said first mentioned portion, said other portion being substantially uncoated. 1 1

4. An electric device comprising an envelope, an anodeand a cathode therein, said-cathode having a'foundation composed of graphite, a

coating of nickel forming the interior surface of said anode which surface is normally bombarded bythe electrons from the cathode during the seasoning or commercial operation of said device.

5. An electric discharge device comprising an envelope, an anode and a cathode therein, said anode surrounding said cathode, the foundation of said anode being composed of a material hav-= ing a. high heat-emissivity characteristic comparable: with that of a black body, .a metallic coating; locatedon the interior surface of said foundation. I

,6. An electric device comprising, an, envelope, an anode and a cathode therein, the foundation of said anode being composed of graphite, said anode surrounding said cathode, a high melting point metal coating on the interior surface .of

said anode. r

7. An electric device comprising an envelope,

an anode and a cathode therein, said anode being, a hollow body and surrounding said cathode,

the foundation of said anode being composed of. 7'

graphitaa coating of nickel on the interior surface of said anode.

8. An electric device comprising an envelope, an anode and a cathode therein, said anode being a hollow body and surrounding said: cathode, the foundation of said anodebeing, composed of graphite, a metallic coating located on the interior surface of said anode.

9. An electric device comprising an envelope, an anode and a cathode therein, said anode partially surrounding said cathode and being composed of graphite, a relatively thin film of metal coating the interior surface of said anode to prevent the graphite of the anode from being deposited onto the cathode during bombardment of said anode.

10. A radio tube including an anode, a cathode and a grid, said grid surrounding said anode, said anode surrounding said grid, said anode being composed of carbon, a metallic coating on the surface thereof facing said grid, the major portion of the remaining surface being substantially uncoated.

11. An electric device including an anode, a cathode and a grid, said grid surrounding said anode, said anode surrounding said grid, said anode being tubular .and composed of carbon, a metallic coating on the interior surface thereof and the exterior surface thereof being substantially uncoated.

12. An anode comprising a base and a metallic coating secured toa portion of the surface of the base, the remainder of the base being substantially uncoated, said base being composed of graphite, said first mentioned portion being that portion which is to be bombarded when the anode is employed in a discharge device.

13. An electric device comprising an anode and a cathode therein, said anode comprising a foundation of carbon, a metallic film located substantially on only that portion of the surface of said foundation which is to be subjected to electron bombardment.

WILLIAM G. MORAN.

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