US2416799A - Electron discharge device - Google Patents

Description

March 4, 1947. c. T. GODDARD 7 2,416,799

ELECTRON DISCHARGE DEVICE Filed Aug. 4, 1942 INVENTOP c. r. GODDARD B A T TORNEY y 5 RHWM l atented Mar. 4,

UNITED STATES PATENT OFFICE ELECTRON DISCHARGE iDEVICJE Charles T. Goddard, New York, 1N."Y., assignor to Western Electric "Company,Incorporated, "New York,"NY.,.'a.corp'oration of -New York Application August-4, 1942,;Serial N o. AS3515 Claims. (019250-215) This invention relates to electron discharge devices, and more particularlyto devices of the types used in ultra high frequency transmission systems.

In such devices th-e-efliciency thereof depends greatly upon the mannerof control of the electrons from the filament to the anode and under the function of the grid. At certain intervals during the functioning of such-devices, the grid structure may attract certain of the electrons and if this attraction may be reduced to a minim-um, the efllciency of the device will be greatly increased. Grid current resultingfrom attraction of theelectrons toward'the grid is commonlyknown as grid loading.

An object of the inventionis to provide an electron discharge device, particularly. one Where the grid loading is reduced to a minimum.

'With thisand other objects in view, the inven tion comprises .an electron discharge device including a filament, anode and control grid, the latter being constructed in .amanner such that portions of-thegrid which .do not actively contribute to power output are prevented from absorbing power. fromthe electron stream.

Other objects andadvantages will be apparent from the following detailed description when considered in conjunction with the accompanying drawing, wherein Fig. 1 is a side elevational view of the device, portions thereof being broken away;

Fig.2 is a fragmentary perspective view of the elements of the device;

Fig. 3 is airagmentary'top plan view of the grid and filament, and

Figs. 'and 5 are sectional'views'of other species of grid structures.

Referring ;nowjto thefdra wing'pthe l device in. cludes a transparent vessel Ill in which leads II are positioned for the mountingvof filamentsupports I 4 and I5, a grid! 6 and an anode I?! thereon.

The grid 16 is of 'the'fin type shown in (Figs. land'z, consisting of a mandrel I8 about which convolutions of a grid wire l9 are wound, leaving loop portions projectingin' front of the mandrel as-s'h'ownin Fig.2. In the present instance the mandrel *is "formed of solid nickel and is supported, together "with the convolutions, by a bracket 26 adaptedfo'r mounting upon its respective lead I I. Thesupports l'd and have a filament 22 positioned therebetween, the ends of the filament being secured to the supports by suitable means such-as welding. The anode I! has acentral portion 24 similar in contour :to the free portionsof :the grid, convolutions l9,y et spacedrequal distances'therefrom. throughout the area "of this portion ofthe anode.

It is known that during the functioning of such devices, a positive potential is applied to the anode H, the filament 22 being negative, while the potential of the grid is 'Eorthemajor portion negative with respect to .the filament. 'Ye't positive peaks in grid. potential intermittently occur which cause attraction of .the electrons and result inscurrent flow in the grid circuit. Thisattraction-wou'ld :occur, ofcourse, only in the electron paths where the. grid wire is disposedaifit were not for the mandrel 18, which is a part of the gridassembly. A flat surface .26 of the mandrel is thus positioned where itwould attractelectrons during the intervals when the ,g-ridis made positive, this surface providing ..a,.greater .areathan those in which the .grid :convolutions are .disposed v and providing a large attracting surface for the electrons during'these intervals. The .attractionv for this surface may be-eliminated, however,..by.covering.-the surface with asuitable material. 1In,F!ig..,-2 an insulatingmaterialjil .is disposed on the :surface .26 and may, if desired, be extended over the ends of the bracket [29. This material may be disposed on .these grid portions by spraying orinsheet form, and. otherwise secured in place.

As another illustration, attention is directed .to Fig. 4,.where-theq-samereference numerals are applied to. the mandrel and the; associated parts, the surface 25 in this instance, however, being provided vwithanother material .such as aluminum oxide indicated at 29, this material being sprayed upon the surface of the mandrel.

In Fig. 5,ganother cross-sectional view of the mandrel It with theassociated parts therein bearing the same referencenumerals.as in Fig.2, illustrates another species wherein .a cover plate 36 of -,a suitable material such as nickeLwith one surface coated as.at 31 with an insulating material, is secured'to thesurfacezt ,of the mandrel by suitable means .suchas welding.

It will thus be apparent that by covering the surfacev 26 of the mandrel with a material ,or materials which will not permit the passage-of electrons at the positive intervals, .t-hegridlloading,that is, the now of electronic current in the grid circuit will .be,,great-ly;reduced. :This of utmost impflrtancein maintaining the device at its maximum efilciency.

The :structure. previously described embodies but one, yet a very important, feature in maintaining the maximum efficiency ,of the .device. Another ,part of,.the sameiproblem lies in the additional grid loading introduced by portions of the grid .which .extend beyond the ends of. the anode. #In current practice, -the grid inst-structure of: the type consideredhereis usuallyextended abeyond'theends of the anode in-order to preventtherdirect-flow=of electrons to theanode from ,p'ortions :of the filament extending beyond the ends of the anode. However, this expedient results in increased grid loading because of the distorted nature of the electric field in this region.

, 3 I All portions of the anode being relatively remote from this portion of the grid and filament, the great majority of electric field lines of force from thefilament must terminate on the grid wires instead of passing between the grid wires as they do in the region bounded by the ends of the anode. This results in additional grid current or loading. Therefore, it would be advantageous to find some means of using a shorter grid to reduce the grid loading without permitting a direct flow of electrons to the anode from portions of the filament extending beyond the ends of the anode. This is accomplished through the aid of shields 34 of the contour illustrated in Figs. 1 and 3, and mounted upon the bracket above and below the grid.

As will be observed, the shields are of general fiatstructure cut away at to conform to the contour of the grid, the cutaway portion being substantially of the dimensions of the grid and smaller than that of the portion 24 of the anode. End portions 36 of the shields are bent to conform to the grid or to the portion of the bracket adjacent the mandrel I8 and are secured thereto by suitable means such as welding.

With the shields 34 in place, it will be apparent that they will intercept any path which electrons mayv take in attempting to pass from the filament portion beyond the grid to the anode. Although the covers 21, 29 and 30- 3l perform their individual functions which may be separate from the functions performed by the shields 34, it is known that they all form a part of the grid structure and their functions overlap in accomplishing a unitary result, namely, the reduction of grid current or loading without detracting from the control features of the grid.

Although specific improvements of the inven tion have been shown and described, it will be understood that they are but illustrative and that various modifications may be made therein without departing from the scope and spirit of this invention as definedby the appended claims.

What is claimed is:

-1. An electron discharge device comprising an elongate electron emitting filament, a control grid having a mandrel, with a fiat inner face, mounted parallel with the filament and formed of a conductive material to attract electrons emitted by the filament, and a grid wire wound about the mandrel and supported thereby with free loops in the convolutions of the wire extendin about therfilament, an anode partially surrounding the grid loops and the filament, and a member disposed on the flat inner face of the mandrel to shield the mandrel against the attraction of the electrons.

2. An electron discharge device comprising an elongate electron emitting filament, a control grid having a mandrel mounted parallel with the filament with its ends terminating short of the ends of the filament and formed of a conductive material to attract electrons emitted by the filament, and a grid wire wound about the mandrel and supported thereby with free loops in the convolutions of the wire extending about the filament, a support for the grid, an anode partially surrounding the grid loops and the filament, a member disposed on the inner face of the mandrel to shield the mandrel against the attraction of the electrons and members mounted upon elongate electron emitting filament, a control grid" Number 4 extending about the filament at each end of the grid to shield the anode from electrons emitted from portions of the filament extending beyond the ends of the grid.

3. An electron discharge device comprising an having a mandrel mounted parallel with the filament and formed of a conductive material to attract electrons emitted by the filament, and a grid wire wound about the mandrel and supported thereby with free loops in the convolutions of the wire extending about the filament, a support for the grid extending about the mandrel thereof excepting the inner face of the latter,

' an anode disposed adjacent the grid loops, and

means disposed on the inner face of the mandrel to shield the mandrel against the attraction of the electrons. a

4. An electron discharge device comprising an elongate electron emitting filament, a control grid having a mandrel mounted parallel with the filament and formed of a conductive material to attract electrons emitted by the filament, and a grid wire wound about the mandrel and supported thereby with free loops in the convolutions of the wire extending about the filament, a support for the grid extending about the mandrel thereof excepting the inner face of the latter, an anode disposed adjacent the grid loops, and a covering of insulating material disposed. on the inner face of the mandrel to shield the mandrel against the attraction of the electrons.

5. An electron discharge device comprising an elongate electron emitting filament, a control grid having a mandrel mounted parallel with the filament and formed of a conductive material to attract electrons emitted by the filament, and a grid wire Woundabout the mandrel and supported thereby with free loops in the convolutions of the wire extending about the filament, a support for the grid extending about the mandrel thereof excepting the inner face of the latter, an anode disposed adjacent thegrid loops, and a covering of aluminum oxide disposed on the inner face of the mandrel to shield the mandrel against the attraction of the electrons.

, CHARLES T. GODDARD.

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

UNITED STATES PATENTS Name 7 Date Hochstetter Nov. 22, 1932 Summers Mar. 1, 1927 Donle Jan. 14, 1919 Number FOREIGN PATENTS Country Date British Sept. 30,1988 British 'Mar. 30, 1931 British 1926 British Dec. 8, 1937 British Mar. 18, 1925 British Dec. 5, 1927 Samuel May 14, 1935

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