US2245581A

US2245581A - Electron discharge device

Info

Publication number: US2245581A
Application number: US307231A
Authority: US
Inventors: Sture O Ekstrand
Original assignee: Bell Telephone Laboratories Inc
Current assignee: AT&T Corp
Priority date: 1939-12-02
Filing date: 1939-12-02
Publication date: 1941-06-17
Anticipated expiration: 1958-06-17
Also published as: US2268165A; GB545835A; FR52414E; US2268196A; FR881705A; BE444006A; DE883938C; NL68166C; GB545689A; US2268197A; US2268195A; DE862640C; US2268194A; NL72884C; BE444002A

Description

Filed Dec. 2. 1939 2 sheeis -sheet 1 //v VEN TOR S. 0. E/(STRAND A 7' TORNEY June 17, 1941.

S. O. EKST RAND ELECTRON DISCHARGE DEVICE Filed Dec., 2,1939:

2' Sheets-Sheet -2 AT TO RNEY Patented June 17, 19 41 UNITED STATES PATENT OFFICE 2,245,581 I smac'mon mscrmnoa nrvrcu State 0. Ekstrand, Bidgefleld Park, N. 1., assignor to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application December 2, 1939, Serial No. 307,231

8 Claims. (01. 250-1152 This invention relates to electron discharge devices and more particularly to cathode ray devices of the type disclosed in the application Serial No. 387,232, filed S. Glass.

Cathoderay devices, such as shown in the above-identified application of Myron 8. Glass, comprise in general an electron source, such as a cathode, an electron receiving element, such as a fluorescent screen, spaced from the electron source, and an electrode system for concentrating the electrons emanating from the source into a thin beam or pencil, for focussing the beam or pencil upon the screen and for deflecting the beam whereby it traces a pattern upon: the electron receiving element.

As pointed out in the Glass application, the desired concentrating and foeussing of the electron beam may be achieved by a multielectrode collimating system and a multielectrode focussing system, the various electrodes being of predetermined configuration and axially symmetrical whereby axially symmetrical fields of particular contour and strength are produced.

The number of electrodes involved entails mechanical diiflculties from the standpoint of construction and. furthermore, the complexity of the electrode system renders dimcult the attainmentof accurate coaxiality of the electrodes which is requisite for the production of axially symmetrical fields.

One general object of this invention is to simplify the assembly of muitielectrode systems for cathodev raydevices. I

Another object of this invention is to expedite the mounting of the electrodes of such systems in cathode ray devices.

A further object of this invention is to facilitate the accurate coaxial alignment of a plurality of electrodes in a collimating and focussing system for cathode ray devices.

Still another object of this invention is to shield eflectively the deflector plates in cathode ray devices from extraneous'flelds.

In one illustrative embodiment of this invention, a cathode my device comprises anenclosing vessel having a stem at one end and a fluorescent screen at the other end, and provided with a cylindrical column or standard extending from adjacent the stem and coaxial therewith. A cathode is mounted adjacent the stem and a collimating system and a focussing system are disposed between the cathode and the screen, each of these systems including a pair of axially symmetrical electrodes. A plurality of deflector December 2, 1939,0f Myron plates are located between the focusing system and the screen.

' In accordance with one feature of this invention, the entire electrode system is fabricated in two unitary assemblies one of which is sup- 4 ported from the stem and the other of which supported by the column or standard.

comprises collimating and modulating electrodes and one of the electrodes of the focussing system, and means are provided for automatically locating these electrodes in accurate coaxial relation during fabrication of the assembly.

In accordance with a further feature of this invention, the other unitary assembly comprises pairs of deflector plates and'a plurality of shields each enclosing a pair of the deflector plates.

The invention and the foregoing and other features thereof will be understood more clearly and fully from the following detailed description with reference to the accompanying drawings in which:

Fig. 1 is an elcvational view in perspective of a cathode ray discharge device illustrative of one embodiment of this invention, portions ofthe enclosing vessel and of one of the terminal carrying bases being broken away to show the internal structure more clearly;

Fig. 2 is an end view of the device shown in Fig. 7

1, illustrating the arrangement of the terminals for the electrodes; v

Fig. 3 is an enlarged detail view, mainly in section, of the electron gun and deflector plate assembly included in the device shown in Fig. 1;

Fig. 4 is a plan view, partly in section along line 4-4 of Fig. 3, of the yillustrated in Fig. 3:

.Fig. 5 is, an enlarged detail elevational view, mainly in section, of the electron gun includ in the assembly shown in Fig. 3;

Fig. 6 is another enlarged detail view, in section, showing details of the oollimating electron; and

Figs. 7 and 8 are detail views of modifications of the deflector plate and shield assembly in the structure shown inFlg.3.

- ray device shown in Fig. 1 comprises an evacuated Referring now to the drawings. the cathode tending stem II which terminates in a tri-armed press It. The flaring end portion ll terminates in a dome-shaped wall 15, the inner surface of which has thereon a fluorescent coating 16 defining a screen. Portions of the inner surfaces of the tubular portion In and flaring end portion H are coated with an opaque electrically conductive material l1, such as colloidal graphite known commercially as Aquadag," as described in Patent 2,096,416, granted October 19, 1937, to Howard W. Weinhart. Sealed-toan intermediate area of the reduced end portion I2 is an elongated cylindrical insulating column or standard l8 coaxial with the stem l3. The column' or standard 18 may be, for example, of glass and fused at one end to the inner wall of the reduced end portion I2.

Suitably afilxed to the end of the reduced cylindrical portion I2 is a base 19 carrying a plurality of terminal prongs 20 through which electrical connection may be established to certain of the electrodes of the device. A second base is ailixed to an intermediate portion of the enclosing vessel and comprises a metallic shell 2|, cemented to the vessel as indicated at 22, and an insulating disc 23, which carries a plurality of terminal prongs 24 to which the other electrodes of the device are connected.

Supported by the stem 13 and column or standard 18 and constituting a unitary assembly therewith is an axially symmetrical electrode system for producing a concentrated electron beam having a sharp clearly defined spot focus upon the fluorescent screen 15.

In general, this electrode system comprises an electron source, a collimating system for concentrating the electrons emanating from the source into an electron beam of small cross-section, a focussing system for bringing the electron beam to a sharp point focus upon the screen l6, and means for controling the direction or intensity or both of the electron beam. More specifically, as shown in detail in Figs. 3 and 5, the electrode system comprises a cathode 25, a control or modulating electrode 26, a collimating electrode 21, a cylindrical focussing electrode 28 and a dished focussing electrode 29. The direction of the electron beam may be controled by pairs of parallel deflector plates 30 and 3|, one pair being mounted at right angles to the other and the plates of each pair being equally spaced on opposite sides of the longitudinal axis of the electrode system.

The cathode 25, as shown clearly in Fig. 5, may be of the indirectly heated equipotential type, and comprises an elongated metallic sleeve to one end of which a metallic cap 32 is secured, like cap having the base surface 33 thereof coated with a thermionic material. The cathode sleeve encompasses an insulating, preferably ceramic, core 34 in which a heater filament 35 is embedded, the inner end of the filament 35 being insulated from the cap 32 by an insulating plug or insert 36. The core 34 is fitted in a central aperture in an insulating, preferably ceramic, platform or spacer 31. Electrical connection to the filament 35 and to the cathode may be established through leading-in

conductors

38 and 39, respectively, sealed in the press l4 and connected to appropriate ones of the terminals 20. The cathode may be anchored in position by the leading-in conductor 39, which is fitted in an aperture in the platform 31 and cemented to the platform as indicated at 40 in Fig. 5.

The cathode 25 is encompassed by a cylindrical metallic sleeve 4| positioned in exact coaxiality with the cap 32 and abutting the platform 31 at the base of a recess in one surface of the platform. As indicated at 42 in Fig. 5, the sleeve 4| may be cemented to the platform 31 and further locked in position by a bent leading in conductor 43, which is fitted in an aperture in the platform, embedded in the press l4 and connected to one of the terminal prongs 20.

The control or modulating electrode 26, which may be machined from a metallic block such as nickel, is fitted in the end of the metallic sleeve 4| and secured, as by welding, to the sleeve 4|.

As illustrated in Fig.- 5, the electrode 26 has an inner frustoconical surface 44 coaxial with the cap 32.

The collimating electrode 21 and cylindrical focussing electrode 29 are mounted coaxially with the modulating electrode 26 and cap 32 and are supported as a unit by a pair of metallic standards or uprights 45 extending from split metallic bands or collars 45 clamped about the stem I3, the standards or uprights 45 being afflxed, as by welding, to the cylindrical portion 41 of a metallic coupler in which the electrode 28 is fitted, as shown clearly in Fig. 5.- The collimating electrode 21 may be machined from a metallic block, for example of cold rolled steel, and has a central aperture 48 and a convex surface 49 coaxial with and opposite the surface 44. The

opposed surfaces

44 and 49 are of accurately predetermined configuration, as described in the application of Myron S. Glass identified hereinabove, whereby the field therebetween is such as to concentrate the electrons emanating from the cathode surface 33 into a thin beam entering the aperture 48.

As pointed out in the aforenoted application of Myron S. Glass, production of the fields requisite for the attainment of the desired electron concentration requires that the

surfaces

44 and 49 be accurately coaxial 'and symmetrical with respect to the common axis. It will be apparent from Fig. 5 that such accurate coaxiality cannot be obtained by usual methods, such as sighting, because the collimating electrode blocks the view into the frustoconical aperture in the modulating electrode 26. The accurate coaxiality is obtained, however, in accordance with one feature of this invention as will be clear from the following description.

Secured to the insulating member 31, as by a plurality of rivets or eyelets 50, and in exact coaxiality with the cylindrical sleeve 4| is a flanged circular metallic guide having a cylindrical upstanding portion 5| and a laterally extending fiange 52. A plurality of resilient fingers or clips 53 are affixed to the flange 52, as by welding. Fitted between the cylindrical portion 5| and the fingers or clips 53 is a cylindrical metallic member 54 in which the electrode 21 is fitted and to which it is secured, as by welding. The end of the member 54 may be fitted in and secured to a depending cylindrical portion 55 of the coupler member.

In the assembly of the device, the cylindrical sleeve 4| with the modulating electrode 26 thereon and the

flanged guide

51, 52 are afiixed to the insulating member 31 in accurate coaxial relation. The electrodes 21 and 28, cylinder 54, coupler member, supports 45 and bands or collars 46 are fabricated into a unitary assembly, the spring clips 53 are affixed as by welding to the cylinder 54, and the cylinder 54 is then slipped over the flange 5|, the clips 53 are afiixed as by welding to the flange 52 and the bands or withthe modulating electrode 28.

" It is highly desirable, of course, that the aperture in the collimating electrode 21 through which the electron beam passes be accurately alined with the cathode surface 33 and be on the axis of symmetry of the

surfaces

44 and 49. Furthermore,

as pointed out in the aforenoted application of 29 byaplurality of resilient metallic fingers I0. which are secured at one end, as by welding, to the cylindrical shield 86 and bear against the coating.

A centrally apertured insulating, preferably ceramic, platform or disc ll supports the deflector plates 29 and 3|, is seated upon the edge of the cylindrical shield 66 and is locked against this Myron 8. Glass, preferably this aperture. should ture 01' this invention, the desired aperture properly located is achieved readily. As shown in Fig.

6, the aperture 49 in the collimating electrode 21 is made of relatively great diameter and the walls thereof are provided with

shoulders

58 and 51. A length of tubing 58 having'a cap 59 afiixed there.- to is fitted in the aperture 48 with the edge of the cap 59 abutting the shoulder 56 and the tubing is spun over as indicated at 60 to lock the tubing in the aperture 18. The cap 59 is provided with a central aperture SI of the desired shape and dimension, for example circular and of the order of 10 mils in diameter.

It will be noted that the cathode 25, modulating electrode 25, collimating electrode 21 and focusing electrode 28 together with the insulating spacer II and

coupler

41, 55 constitute a unitary V assembly which'is supported by the bands or collars l8 clamped about the stem l3, so that but small stresses are produced in the leading-in

conductors

38, 39 and I3, and, consequently, imilarly small stresses obtain in the arms of the press ll whereby cracking 'or breaking of the stem is prevented.

A suitable positive potential may be applied. to the electrodes 21 and 28 through a leading-in conductor 62 embedded in the press and connected to one of the standards or uprights 45 by a tie wire Ill.

A second unitary assembly comprising the focussing electrode 29 andthe deflector plates 30 and 3| is supported upon the tubular column 18 as best shown in Fig. 3. This assembly includes a dished metallic base member 53 which is seated upon the inner end of the column l8 and held thereagainst by a plurality of arms 64 carried by and extending from a split metallic band 55 clamped about the column is. The focussing electrode 29 is provided with an integral cylindrical portion 65'fitted inthe dished member 63, is coaxially positioned with the cylindrical electrode 28 and is provided with a central aperture 81 through which the electron beam passes. The surface 69 of the focussing electrode 29 is of acedge as by a plurality of wires 12 securedto the shield, extending throughthe platform or disc and bent over against the platform or disc. Each of the deflector plates 30, and 9| .has an edge seated on a chordal groove or slot in the platform or disc II and is provided with extensions 13 which extend through slots in the platform and are twisted to hold the plates 30 and 3| securely in position. Each of the deflector plates 30 and 3| is provided also with an extension 14 to which a leading-in conductor 15, connected to a corre-. sponding one of the terminals 24, is afiixed. The extensions 14 on the deflector plates 30 extend through apertures 15 in the cylindrical member 56.

The cylindrical member 66. it will be noted, surrounds the deflector plates 3ll and screens these plates and also the beam passing therebetween from extraneous fields.

Seated upon the focussing electrode 29 is a centrally apertured metallicbarrier or baflle 11, which is coaxial with the focussing electrode 29 and screens the focussing field, between the focussing

electrodes

28 and 29, from potentials upon the deflector plates.

As illustrated in Fig. 7, the deflector plates 3| also may bescreened from extraneous fieldsby .a metallic shield including a cylindrical portion 18- and a centrally apertured top plate 19 which curately determined configuration, as described Electrical connection to the elec-v "is held in position by a centrally apertured cap against the platform. Also, as shown in Fig. 7,

the resilient fingers ll may be the arms of a hair-" pin shaped wire element carried by an insulating,

preferably ceramic, member 90 mounted on a bracket 82 secured to the cylinder 66. The fingers H may be connected electrically to

terminals

20 or 24 by conductors 83 whereby the coating I! may be used as an accelerating electrode.

In the modification illustrated in Fig. 8. an auxiliary pair of deflector plates 84 are provided within the shield 66 to enable control of the deflection sensitivity of the device. Each of the deflector plates 94 is coplanar with a corresponding one of the deflector plates 30 and is supported therefrom through wire stubs 85 embedded in insulating beads 88. Suitable leading-in conduc tors, not shown, may be provided for the auxiliary plates 84 and connected to terminals 24.

Although specific embodiments of this invention have been shown and described, it will be understood, of course, that they are but illustrative and that various modifications may be made therein without departing from the scope and spirit of this invention as defined in the appended claims. I

What is claimed is:

1. A unitary electrode assembly for electron discharge devices comprising a stem, a platform supported above said stem and having a central aperture and a recess coaxial with said aperture,- guide means carried by said platform and coaxial with said aperture, a cathode fitted in said aperture, an electrode coaxial with said cathode and having a tubular portion seated in said recess and secured to said platform, and a second electrode having a tubular portion positioned by said guide means in coaxial relation with said cathode and said first electrode.

2. A unitary electrode assembly for cathode ray discharge devices comprising a platform having a circular recess in one face thereof, a cylindrical guiding member mounted on said platform coaxial with said recess, a cathode carried by said platform and coaxial with said recess and guiding member, a modulating electrode coaxial with said cathode having a tubular portion seated in said recess and positioned thereby, an electrode structure having a collimatlng portion opposite said modulating electrode and a cylindrical portion fitted to said guiding member, and resilient means aiiixed to said platform and locking said cylindrical portion to said guiding member.

3. A unitary electrode assembly in accordance with claim 2 wherein said collimating portion is provided with a central aperture countersunk at opposite ends, said assembly comprising also an insert fitted in said aperture and having its ends locked to said countersunk ends, said insert having a laterally extending portion provided with a restricted aperture in alignment with said cathode.

4. An electron gun for cathode ray discharge devices comprising a stem, an insulating platform having a central aperture and a recess coaxial with said aperture, a guiding member secured to said platform and having a cylindrical portion coaxial with said aperture, a cathode fitted in said aperture, a control electrode having a tubular portion seated in said recess and aiiixed to said platform, a unitary assembly including a collimatlng electrode, a cylindrical focussing electrode and a cylindrical member, said cylindrical member being fitted on said cylindrical portion, means locking said cylindrical member to said cylindrical portion, and supporting means aflixed to said stem and to said unitary assembly.

5. An electron discharge device comprising an enclosing vessel having an internal tubular column, and a unitary electrode assembly mounted on said column, said assembly including a base member, a cylindrical shield carried by said base member, an insulating platform supported by said shield and ailixed thereto, a pair of deflector plates depending from said platform and within said shield, and a second pair of deflector plates extending front-said platform and supported thereon.

6. An electron discharge device in accordance with claim 5 comprising a second cylindrical shield mounted on said platform and encompassing said second pair of deflector plates.

7. An electron discharge device in accordance with claim 5 wherein said platform is provided with chordal slots in which said deflector plates are seated, each of said deflector plates having extensions projecting through said slots and anchored to said platform.

8. A cathode ray discharge device comprising an enclosing vessel having a stem at one end and an interior tubular standard extending longitudinally of said vessel from adjacent said stem, a unitary electrode assembly within said standard including a cathode and control. collimatlng and focussing electrodes coaxial with one another, a platform having a central aperture in which said cathode is fitted, and having also a recess in one surface coaxial with said cathode, said control electrode including a tubular portion seated in said recess, guiding means afflxed to said platform and having a tubular member coaxial with said aperture, said collimatlng electrode having a tubular portion fitted on said tubular member, means afllxing said tubular portion to said tubular member, and means supporting said focussing electrode upon said tubular member and in coaxial relation therewith, means supporting said unitary assembly from said stem, a second unitary assembly including a base member, a second focussing electrode carried thereby, a second platform supported from said base member, and pairs of deflector plates mounted on said second platform, and means supporting said second assembly on said standard coaxial with said first assembly.

STURE O. EKSTRAND.