US3035203A - Cathode-ray tube - Google Patents

Cathode-ray tube Download PDF

Info

Publication number
US3035203A
US3035203A US858897A US85889759A US3035203A US 3035203 A US3035203 A US 3035203A US 858897 A US858897 A US 858897A US 85889759 A US85889759 A US 85889759A US 3035203 A US3035203 A US 3035203A
Authority
US
United States
Prior art keywords
mesh
cathode
screen
deflection
ray tube
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US858897A
Inventor
Fischman Martin
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
GTE Sylvania Inc
Original Assignee
Sylvania Electric Products Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Sylvania Electric Products Inc filed Critical Sylvania Electric Products Inc
Priority to US858897A priority Critical patent/US3035203A/en
Application granted granted Critical
Publication of US3035203A publication Critical patent/US3035203A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01JELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J29/00Details of cathode-ray tubes or of electron-beam tubes of the types covered by group H01J31/00
    • H01J29/46Arrangements of electrodes and associated parts for generating or controlling the ray or beam, e.g. electron-optical arrangement
    • H01J29/80Arrangements for controlling the ray or beam after passing the main deflection system, e.g. for post-acceleration or post-concentration, for colour switching

Definitions

  • a further object is to provide a cathode-ray tube in which the brightness of the picture is maintained at a high level although the power needed to drive the deflection system is relatively low.
  • Another object is to minimize defocusing and changes in picture size resulting from variations in the high voltage supply to the phosphor screen.
  • Still another object is to provide a cathode-ray tube utilizing post-deflection acceleration which has excellent deflection sensitivity.
  • the present invention comprises a monochrome cathode-ray tube in which post-deflection acceleration is achieved by placing a wire mesh having high electron transparency between the beam deflection apparatus and the phosphor screen of the tube.
  • the entire wire mesh is maintained at a uniform positive D.-C. voltage having a magnitude substantially lower than that of the D.-C. voltage applied to the phosphor screen.
  • Electrons are emitted in the direction of the phosphor screen by an electron gun assembly and then deflected by an electrostatic or electromagnetic field while being simultaneously accelerated by the positive voltage on the aquadag coating and the wire mesh. Since the voltage on the wire mesh is relatively low, the power required todrive the deflection yoke is proportionally small. After the electrons reach the mesh, they are accelerated toward the phosphor screen by the high voltage existing between the screen and mesh to produce the desired brightness.
  • FIG. 1 is a schematic diagram of a cathode-ray tube embodying the invention.
  • FIG. 2 is a cross-sectional view of the tube of FIG. 1 showing the surface of the wire mesh.
  • FIG. 1 there is shown a cathoderay tube having a conventional electron gun assembly consisting of a cathode 11, control grid 12, anode 13, and focusing coil 14.
  • the current through yoke produces a transverse magnetic field which deflects the electrons emitted by cathode 11 through an angle determined by the magnitude and direction of the yoke current.
  • These electrons are accelerated along a path, such as 17, toward a wire mesh 18 having a terminal T maintained at a positive voltage E with respect to the cathode.
  • Wire mesh 18 is mounted perpendicular to the longitudinal axis of cathode-ray tube 10 and is spaced from the screen 19 of the curved cathode-ray tube by a distance which is relatively short when compared with the total length of the tube.
  • the openings in the mesh each have an area approximately equal to the area of the electron beam.
  • the inside of screen 19 is coated with an aluminized phosphor maintained at a positive potential E by a voltage connected to a terminal T voltage E having a magnitude several times higher than E
  • a cathode-ray tube screen having a wrap-around conducting cylindrical edge 19a is preferred for this application, since it has been found that the effect of the collimating action of the screen-to-mesh electric field on the deflection of the electron beam is thereby minimized.
  • Deflection of the electron beam across the screen 19 is obtained by passing a current which increases linearly with time through the coils of the deflection yoke 15.
  • the current in the deflection yoke 15 required to produce a given deflection is approximately proportional to the square root of the accelerating voltage and, therefore, the power used in producing the linear deflection current is directly proportional to the wire mesh voltage E
  • the electrons are deflected using relatively little deflection coil power. The electrons are then accelerated to high speeds in the region between the screen 19 and wire mesh 18.
  • the ratio of the deflection coil power required with wire mesh 18 in the tube to that required without the mesh is approximately E divided by E It has been found that excellent performance is obtained with a spacing between mesh 18 and screen 19 of about one inch, a screen voltage (E equal to 12 kv., and a mesh voltage (E of about 4 kv. The power required for deflection under these conditions is about one third of the power required without mesh 18. It shall be understood that the values stated above are merely typical and are not intended to limit the invention in any way.
  • FIG. 2 is a cross-sectional view of cathode-ray tube 10 showing the surface of wire mesh 18.
  • This mesh which may be made from woven metal gauze, be produced by electroforrning, or punched from a thin stainless steel sheet, is maintained at a uniform potential over its entire surface by the voltage E applied to terminal T
  • the openings in the mesh are square, the center to center distance being typically about .01 inch. While the size and shape of the openings are not critical, the spacing of the openings should not be so large as to produce discernible patterns or shadows on the phosphor screen 19.
  • the mesh 18 is placed in the cathode-ray tube 10 so that the wires comprising it are at an angle of about 45 with respect to the horizontal scanning axis in order to minimize moire patterns.
  • the aquadag coating 21 on the inside of the tube structure may be maintained at the same potential as mesh 18 by connecting terminal T directly to terminal T or by extending the aquadag coating so that it electrically contacts mesh 18. If a voltage gradient higher than 8 kv. per inch is applied between the mesh and screen then some secondary emission may occur. In this case the aquadag coating 21 may be operated at a somewhat higher potential than mesh 18 in order to collect stray electrons emanating from the mesh and prevent them from striking phosphor screen 19. In addition, secondary emission may be reduced by coating the wire mesh 18 with graphite.
  • the aluminized phosphor screen 19 may be coated with a suitable substance, such as beryllium, in order to reduce the effect of secondary electrons.
  • a monochrome cathode-ray tube comprising (a) electron beam projecting means mounted at one end of said tube,
  • said con- 20 ducting mesh comprises first and second groups of spaced parallel conductors, said first and second groups of conductors being arranged perpendicularly to each other and being conductively joined to form an equipotential surface.

Landscapes

  • Vessels, Lead-In Wires, Accessory Apparatuses For Cathode-Ray Tubes (AREA)

Description

May 15, 1962 M. FISCHMAN CATHODE-RAY TUBE Filed Dec. 11, 1959 BEA/ERA TOR /6' SAW 700771 INVENTOR MART/IV FISCf/MAN BY dwkk ATTORNEY 3,035,203 Patented lVlay 15, 1962 Fice 3,035,203 CATHODE-RAY TUBE Martin Fischrnan, Wantagh, N.Y., assignor to Sylvania Electric Products Inc., a corporation of Delaware Filed Dec. 11, 1959, Ser. No. 858,897 2 Claims. (Cl. 31515) This invention relates to cathode-ray tubes.
Conventional cathode-ray tubes, whether they use electrostatic or electromagnetic deflection, require relatively large amounts of power to drive their deflection systems. When these tubes are used in conjunction with efficient electronic circuits, such as those employing transistors, the power required to deflect the electron beam becomes a substantial percentage of the total input power to the equipment. It has been found, for example, that in a transistorized television receiver using a conventional cathode-ray tube about 70% of the total input power is used to drive the deflection system. This has resulted in the need for comparatively heavy batteries which re quire frequent reacharging thereby impairing the usefulness of the receiver.
Accordingly, it is a principal object of this invention to provide an improved cathode-ray tube wherein relatively small amounts of power are required to drive the deflection system.
A further object is to provide a cathode-ray tube in which the brightness of the picture is maintained at a high level although the power needed to drive the deflection system is relatively low.
Another object is to minimize defocusing and changes in picture size resulting from variations in the high voltage supply to the phosphor screen.
Still another object is to provide a cathode-ray tube utilizing post-deflection acceleration which has excellent deflection sensitivity.
The present invention comprises a monochrome cathode-ray tube in which post-deflection acceleration is achieved by placing a wire mesh having high electron transparency between the beam deflection apparatus and the phosphor screen of the tube. The entire wire mesh is maintained at a uniform positive D.-C. voltage having a magnitude substantially lower than that of the D.-C. voltage applied to the phosphor screen. Electrons are emitted in the direction of the phosphor screen by an electron gun assembly and then deflected by an electrostatic or electromagnetic field while being simultaneously accelerated by the positive voltage on the aquadag coating and the wire mesh. Since the voltage on the wire mesh is relatively low, the power required todrive the deflection yoke is proportionally small. After the electrons reach the mesh, they are accelerated toward the phosphor screen by the high voltage existing between the screen and mesh to produce the desired brightness.
The above objects of and the brief inuoduction to the present invention will be more fully understood and further objects and advantages 'will become apparent from a study of the following description in connection with the drawing, wherein:
FIG. 1 is a schematic diagram of a cathode-ray tube embodying the invention; and
FIG. 2 is a cross-sectional view of the tube of FIG. 1 showing the surface of the wire mesh.
Referring now to FIG. 1, there is shown a cathoderay tube having a conventional electron gun assembly consisting of a cathode 11, control grid 12, anode 13, and focusing coil 14. An electromagnetic deflection yoke 15, energized from a sawtooth generator 16, surrounds the neck of tube 1!). The current through yoke produces a transverse magnetic field which deflects the electrons emitted by cathode 11 through an angle determined by the magnitude and direction of the yoke current. These electrons are accelerated along a path, such as 17, toward a wire mesh 18 having a terminal T maintained at a positive voltage E with respect to the cathode. Wire mesh 18 is mounted perpendicular to the longitudinal axis of cathode-ray tube 10 and is spaced from the screen 19 of the curved cathode-ray tube by a distance which is relatively short when compared with the total length of the tube. The openings in the mesh each have an area approximately equal to the area of the electron beam.
The inside of screen 19 is coated with an aluminized phosphor maintained at a positive potential E by a voltage connected to a terminal T voltage E having a magnitude several times higher than E The high voltage produced by the voltage difierence E minus E acting over the region between mesh 18 and screen 19, causes the electrons impinging on mesh 18 to be rapidly accelerated along the path 20 thereby producing a bright spot on the screen 19. A cathode-ray tube screen having a wrap-around conducting cylindrical edge 19a is preferred for this application, since it has been found that the effect of the collimating action of the screen-to-mesh electric field on the deflection of the electron beam is thereby minimized.
Deflection of the electron beam across the screen 19 is obtained by passing a current which increases linearly with time through the coils of the deflection yoke 15. The current in the deflection yoke 15 required to produce a given deflection is approximately proportional to the square root of the accelerating voltage and, therefore, the power used in producing the linear deflection current is directly proportional to the wire mesh voltage E Thus, by introducing the low potential wire mesh 18 between the deflection yoke 15 and the high voltage screen 19, the electrons are deflected using relatively little deflection coil power. The electrons are then accelerated to high speeds in the region between the screen 19 and wire mesh 18. The ratio of the deflection coil power required with wire mesh 18 in the tube to that required without the mesh is approximately E divided by E It has been found that excellent performance is obtained with a spacing between mesh 18 and screen 19 of about one inch, a screen voltage (E equal to 12 kv., and a mesh voltage (E of about 4 kv. The power required for deflection under these conditions is about one third of the power required without mesh 18. It shall be understood that the values stated above are merely typical and are not intended to limit the invention in any way.
FIG. 2 is a cross-sectional view of cathode-ray tube 10 showing the surface of wire mesh 18. This mesh, which may be made from woven metal gauze, be produced by electroforrning, or punched from a thin stainless steel sheet, is maintained at a uniform potential over its entire surface by the voltage E applied to terminal T The openings in the mesh are square, the center to center distance being typically about .01 inch. While the size and shape of the openings are not critical, the spacing of the openings should not be so large as to produce discernible patterns or shadows on the phosphor screen 19. In addition, as shown in FIG. 2, the mesh 18 is placed in the cathode-ray tube 10 so that the wires comprising it are at an angle of about 45 with respect to the horizontal scanning axis in order to minimize moire patterns.
I have found that if the voltage gradient between the screen 19 and mesh 18 does not exceed 8 kv. per inch, that the secondary emission from mesh 18 is negligible. Under these conditions, the aquadag coating 21 on the inside of the tube structure may be maintained at the same potential as mesh 18 by connecting terminal T directly to terminal T or by extending the aquadag coating so that it electrically contacts mesh 18. If a voltage gradient higher than 8 kv. per inch is applied between the mesh and screen then some secondary emission may occur. In this case the aquadag coating 21 may be operated at a somewhat higher potential than mesh 18 in order to collect stray electrons emanating from the mesh and prevent them from striking phosphor screen 19. In addition, secondary emission may be reduced by coating the wire mesh 18 with graphite. The aluminized phosphor screen 19 may be coated with a suitable substance, such as beryllium, in order to reduce the effect of secondary electrons.
Focusing and deflection both occur in the portion of the tube Where the accelerating potential is due to the voltage on the aquadag coating and the wire mesh 18. Variations in the high voltage supply of the phosphor screen 19 have little effect on the picture size and no effeet on the focus due to the shielding eifect of the mesh 18. It is a relatively simple matter to maintain good regulation of the voltage on mesh 18 since the current drawn by the high transparency mesh is a small percentage of the total beam current.
As many changes could be made in the above construction and many different embodiments could be made Without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.
What is claimed is:
1. A monochrome cathode-ray tube comprising (a) electron beam projecting means mounted at one end of said tube,
(b) a screen having a phosphor coating located at the other end of said tube, said screen being maintained at a positive potential with respect to said electron beam projecting means;
(a) electromagnetic deflection means surrounding the longitudinal axis of said tube, said electromagnetic deflection means being mounted adjacent said electron beam projecting means,
(d) a conductive coating aflixed to the inner surface of said tube, said conductive coating being spaced from said screen and extending toward said electron beam projecting means, and
(e) a single conducting mesh mounted between said screen and said conductive coating, said conducting mesh having its surface substantially perpendicular to the longitudinal axis of said tube.
2. Apparatus as defined in claim 1, wherein said con- 20 ducting mesh comprises first and second groups of spaced parallel conductors, said first and second groups of conductors being arranged perpendicularly to each other and being conductively joined to form an equipotential surface.
Epstein Mar. 30, 1943 Dufour June 3, 1958
US858897A 1959-12-11 1959-12-11 Cathode-ray tube Expired - Lifetime US3035203A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
US858897A US3035203A (en) 1959-12-11 1959-12-11 Cathode-ray tube

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US858897A US3035203A (en) 1959-12-11 1959-12-11 Cathode-ray tube

Publications (1)

Publication Number Publication Date
US3035203A true US3035203A (en) 1962-05-15

Family

ID=25329457

Family Applications (1)

Application Number Title Priority Date Filing Date
US858897A Expired - Lifetime US3035203A (en) 1959-12-11 1959-12-11 Cathode-ray tube

Country Status (1)

Country Link
US (1) US3035203A (en)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3177395A (en) * 1963-04-04 1965-04-06 Gen Electric Flat cathode ray tube with increased deflection sensitivity
US3250942A (en) * 1960-08-08 1966-05-10 Sony Corp Cathode ray tube with improved deflection magnifying screen
US3814966A (en) * 1971-09-08 1974-06-04 Hitachi Ltd Post-deflection acceleration type color cathode-ray tube
US3946265A (en) * 1969-09-17 1976-03-23 U.S. Philips Corporation Vidicon with grid wire angles selected to minimize chrominance signal interference
US4321470A (en) * 1980-06-30 1982-03-23 Rca Corporation Electron flood exposure apparatus

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2315367A (en) * 1940-07-31 1943-03-30 Rca Corp Cathode-ray tube
US2837689A (en) * 1954-12-02 1958-06-03 Csf Post acceleration grid devices

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2315367A (en) * 1940-07-31 1943-03-30 Rca Corp Cathode-ray tube
US2837689A (en) * 1954-12-02 1958-06-03 Csf Post acceleration grid devices

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3250942A (en) * 1960-08-08 1966-05-10 Sony Corp Cathode ray tube with improved deflection magnifying screen
US3177395A (en) * 1963-04-04 1965-04-06 Gen Electric Flat cathode ray tube with increased deflection sensitivity
US3946265A (en) * 1969-09-17 1976-03-23 U.S. Philips Corporation Vidicon with grid wire angles selected to minimize chrominance signal interference
US3814966A (en) * 1971-09-08 1974-06-04 Hitachi Ltd Post-deflection acceleration type color cathode-ray tube
US4321470A (en) * 1980-06-30 1982-03-23 Rca Corporation Electron flood exposure apparatus

Similar Documents

Publication Publication Date Title
US3143681A (en) Spiral electrostatic electron lens
US2454652A (en) Cathode-ray storage tube
US3035203A (en) Cathode-ray tube
US3102212A (en) Cathode ray tube with low velocity deflection and post deflection beam acceleration
US2837689A (en) Post acceleration grid devices
US2214729A (en) Magnetic field neutralizing system
US3295010A (en) Image dissector with field mesh near photocathode
US3154710A (en) Cathode-ray display system having electrostatic magnifying lens
US4339694A (en) Flat cathode ray tube
US2267823A (en) Scanning device for television
US2981864A (en) Image display device
US3579010A (en) Elongated aperture electron gun structure for flat cathode-ray tube
US3243645A (en) Post deflection focusing cathode ray tube for color television images of high brightness and low raster distortion
US2971108A (en) Electron discharge device
US3772551A (en) Cathode ray tube system
US2898493A (en) Method and apparatus for controlling electron beams
US4032815A (en) Collimated beam electron gun system for shaped beam cathode ray tube
US3249784A (en) Direct-view signal-storage tube with image expansion means between storage grid and viewing screen
US3691423A (en) Method of improving the resolution of an image converter system
US3250942A (en) Cathode ray tube with improved deflection magnifying screen
US2836752A (en) Beam generating system for cathoderay tubes employing an ion trap
US2951961A (en) Electron beam deflection system
US3576457A (en) High-resolution direct-view storage tube
US2782333A (en) Shortened triple gun for color television
US2835838A (en) Cathode-ray tube