US2743391A

US2743391A - Cathode ray tube

Info

Publication number: US2743391A
Application number: US254575A
Authority: US
Inventors: Kenneth A Hoagland
Original assignee: Allen B du Mont Laboratories Inc
Current assignee: Allen B du Mont Laboratories Inc
Priority date: 1951-11-02
Filing date: 1951-11-02
Publication date: 1956-04-24
Anticipated expiration: 1973-04-24

Description

April 24, 1956 K. A. HOAGLAND CATHODE RAY TUBE Filed NOV. 2, 1951 mw om@ T A NL) E G www 1H AJM., m .NLV/ MY KB ATTORNEYS A lnited CATHODE RAY TUBE Kenneth A. Hoagland, Nutley, N. J., assignor to Allen B. Du Mont Laboratories, Inc., Clifton, N. J., a corporation of Delaware v Application November 2, 1951, Serial N o. 254,575 9 Claims. (Cl. 31517) The present invention relates to cathode ray tubes and particularly to improvements in cathode ray tubes of the post deflection acceleration type.

Cathode ray tubes in which electron acceleration is obtained after deflection have the desirable characteristic of a high degree of deflection sensitivity at substantially lower deflection control voltages. Heretofore, this desirable characteristic has been obtained in cathode ray tubes by providing either an electrically conductive ring or a plurality of electrically conductive rings spaced between the deflection means and the screen of the tube. Such rings' have commonly been referred to as intensifier rings and where a single ring has been utilized, the tube is generally operated with the ring at a voltage substantially higher than the anode voltage to obtain the desired electron acceleration. Where a series of spaced rings have been utilized, the tube is generally operated with each of the rings at voltages substantially higher than the anode voltage and at successively increased voltage as the rings approach the screen.

Tubes of these types have not been entirely satisfactory, however, because of the electron lens effect caused by the rings and the consequent distortion of the beam along paths angularly displaced from the central axis of the tubes.

Accordingly, it is an object of the present invention to provide an improved cathode ray tube of the post deflection acceleration type.

It is another object of the present invention to provide an improved cathode ray tube of the post deflection acceleration type in which post deflection beam distortion is substantially eliminated.

lt is still another object of the present invention to provide an improved cathode ray of the post deflection acceleration type in which the electron lens effect is substantially eliminated between the deflection means and the screen of the tube. l

These and other desirable objects are attained in accordance with the present invention by providing a cathode ray tube in which acceleration of the electrons is obtained after deflection thereof by an electron acceleration region in the tube formed by spaced electrically conductive elements positioned transversely of the tube and adjacent the screen.

For a better understanding of the invention, reference may be had to the following description along with the drawing in which Figure l is' a longitudinal crosssectional View with parts broken away of a cathode ray `tube embodying the present invention and Figure 2 is a diagrammatic illustration ofv the tube with a schematic illustration of circuit relationship of the elements of the tube.

Referring now to the drawing and particularly to Figure 1, there is illustrated a cathode ray tube embodying Vthe present invention and comprising a substantially tubular container 2 which is generally made of glass but vmay be made of other suitable materials. One end of the container is reduced to provide a neck portion 4 and the other end of the container is provided with a face plate 6. Supported within the neck portion 4 is an electron gun 8 such as are commonly used in cathode ray tubes and comprising a cathode 10, a grid 12, a first accelerating electrode 14,'a focussing electrode 16 sometimes referred to as a first anode, and a secondl accelerating electrode y18 also known in the art as a second anode. Each of the aforementioned elements are supported in axial alignment in a unitary assembly within the neck portion by apair of insulating rods 20.*v A pair of horizontal deflection plates 22 and a pair of vertical deflection plates 24 are secured in spaced relationship on opposite sides of the longitudinal axis of the electron gun and are respectively positioned parallel with the perpendicular cross-sectional axes of the electron gun, and at one end thereof. The deflection plates are secured to supporting wires 26 which, in turn, are supported by a pair of insulating discs 27, one of which is attached to the ends of the insulating rods 20, as shown.

While I have illustrated and described a cathode ray tube structure especially adapted to utilize electrostatic means' such as deflection plates for horizontal and Avertical detlection of the electron beam, it will be obvious that deflection of the beam may be obtained by wellknown means other than deflection plates, such as an electromagnetic yoke which is supported externally of the neck of the tube.

The face 6 of the cathode ray` tube 2 is provided on its inner surface with a fluorescent coating 28 and an electrically conductive screen or coating 30. The coating 30, as shown, s formed on the surface of the fluorescent coating 28 and is accordingly provided with electron permeable characteristics. In this connection, it should be understood that a transparent metallic electrically conductive screen interposed between the face of the tube and the fluorescent coating would be equally as effective for the purposes of this invention as screen 30. An electrically conductive lead 32 provides an external connectionfor the screen 30.

Spaced from the screen 30 is a grid assembly 34 comprising spaced

grids

36 and 38.

Grids

36 and 38 are electrically conductive discs supported transversely of the tube and are provided respectively with a plurality of equally

spacedsmall apertures

40 and ,42 throughout the entire cross-section thereof. The

discs

36 and 38 are positioned in the tube with the

apertures

40 and 42 in alignment along axes parallel to the central axis of the tube and discs and apertures 42 are formed with a cross-sectional diameter substantially larger than that of apertures 40 to avoid the interception of electrons which have passed through the apertures ,40 of disc 36.

External terminals

44 and 46 passing through the tube wall provide means for electrical connections with the

discs

36 and 38. Likewise prongs 448 in the base 50 provide electrical connections with the cathode 10, grid 12, focussing electrodel and

deflection plates

22 and 24. An electrical conductive coating 52 on the inner surface of the tube which is-in circuit conducting relationship with disc 36 and the spring fingers of a support member 54 connected to the electrodes 18 and 14 in a manner to be described hereinafter in connection with Figure 2 of the drawing provides means for connecting these electrodes with an external source of potential.

For a 4better understanding of the operation of the cathode ray tube of the present invention, reference may be had to Figure 2 of the drawing. In this figure, 56 illustrates a -source of accelerating potential for the electron gun 8. Focussing electrode 16 of the electron gun S is connectedby lead wire 58 to source 56 at an intermediate potential terminal of the source while electrodes connecting potential to said electrically conductive screen and to one of said grids to provide an electron accelerating force therebetween.

5. An electron discharge device comprising an envelope having a uorescent screen, an electrically conductive surface adjacent said uorescent screen, an electron gun for generating and directing electrons toward said screen, a Iirst grid positioned between said gun and said screen and having electron-permeable openings therein, and a second grid adapted to operate at a potential lower than the potential of said iirst grid and positioned between said iirst grid and said screen, with electron-permeable openings therein in alignment with the path of said electrons to permit said electrons to pass therethrough and to prevent said electrons from striking the conductive portions thereof said iirst and said second grids being substantially parallel to said conductive screen.

6. An electron discharge device comprising an envelope having a target face, a iluorescent screen on said face, an electrically conductive screen positioned in said envelope adjacent said uorescent screen, an electron gun positioned in said envelope for directing a stream of electrons toward said uorescent screen, a pair of grids positioned in said envelope between said electrically conductive screen and said gun and substantially parallel to said conductive screen, a source of potential, means connecting said source of potential to said grids to cause the grid nearer said screen to be negative with respect to the other of said pair of grids, and means connecting said source of potential to said electrically conductive screen and the grid nearest thereto to cause an electron accelerating force therebetween.

7.An electron discharge device comprising an envelope having a target face, a uorescent screen on said face, an electrically conductive screen positioned in said envelope adjacent said uorescent screen, an electron gun positioned in said envelope for directing a stream of electrons toward said fluorescent screen, a pair of grids positioned in said envelope between said electrically conductive screen and said gun and substantially parallel to said conductive screen, a source of potential having an intermediate terminal and a second terminal less than approximately 100 volts negative with respect to said intermediate terminal and a third terminal positive with respect to said intermediate terminal by approximately 20,000 volts, means connecting said intermediate terminal the grid nearest said gain and connecting said second terminal to the other grid and means connecting said third terminal to said electrically conductive `screen to cause said electrically conductive screen to be positive with respect to the grid adjacent thereto.

8. An electron discharge device comprising an enve lope having a target face, a uorescent screen on said face, an electrically conductive screen positioned in said envelope adjacent said uorescent screen, an electron gun positioned in said envelope for directing a stream of electrons toward said fluorescent screen, a iirst and a second perforated grid plate positioned in order in said envelope between said gun and conductive screen and transversely of the longitudinal axis of said envelope and substantially parallel to each other and to said conductive screen, said plates having their perforations in electron path alignment with the electron path to substantially prevent electrons from striking said second grid after passing through the perforations in said first grid, a source of potential, means connecting said source of potential to said tirst and second grids to cause said rst grid to be positive with respect to said second grid and means connecting said source of potential to said electrically conductive screen and to said second grid to cause said electrically conductive screen to be positive with respect to said second grid.

9. The apparatus of claim 8, in which the perforations in said second grid plate are larger than the perforations in said lirst grid plate.

References Cited in the tile of this patent UNITED STATES PATENTS Re. 23,672 Okolicsanyi June 23, 1953 1,810,018 Howes June 16, 1931 2,029,639 Schlesinger Feb. 4, 1936 2,118,865 Schlesinger May 31, 1938 2,165,308 Skellett July 11, 1939 2,315,367 Epstein Mar. 30, 1943 2,532,511 Okolicsanyi Dec. 5, 1950 2,606,303 Bramley Aug. 5, 1952 2,692,532 Lawrence Oct. 26, 1954