US3909655A - Cathode ray tube having cylinder with internal resistive helix - Google Patents

Cathode ray tube having cylinder with internal resistive helix Download PDF

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Publication number
US3909655A
US3909655A US376166A US37616673A US3909655A US 3909655 A US3909655 A US 3909655A US 376166 A US376166 A US 376166A US 37616673 A US37616673 A US 37616673A US 3909655 A US3909655 A US 3909655A
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Prior art keywords
coating
electrically
resistor
cylinder
internal
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Expired - Lifetime
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US376166A
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English (en)
Inventor
Michael Charles Grimmett
Douglas Gerald Crawley
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EMI Group Ltd
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Thorn Electrical Industries Ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J29/00—Details of cathode-ray tubes or of electron-beam tubes of the types covered by group H01J31/00
    • H01J29/96—One or more circuit elements structurally associated with the tube
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J2229/00—Details of cathode ray tubes or electron beam tubes
    • H01J2229/48—Electron guns
    • H01J2229/4824—Constructional arrangements of electrodes
    • H01J2229/4827—Electrodes formed on surface of common cylindrical support

Definitions

  • NV Q a CATHODE RAY TUBE HAVING CYLINDER WITH INTERNAL RESISTIVE HELIX BACKGROUND OF THE INVENTION
  • his invention relates to cathode ray tubes, and especially to cathode ray tubes including means for reducing the effects of internal flashover.
  • a cathode ray tube having an electron gun assembly mounted within a sealed evacuated envelope formed substantially of electrically insulating material is usually provided with a first coating of electrically conductive material on part of its external surface and a second coating of electrically conductive material on part of its internal surface. These coatings form a capacitor which can be used in a smoothing circuit for a high voltage supply circuit for use with the tube. This capacitor then contains a charge during operation of the tube, the internal coating being supplied with a positive voltage, and the external coating being connected to earth.
  • Anodes are normally maintained at the same voltage as the internal coating in operation. A flashover from one of the anodes to one or more of the other electrodes, even the heater, having lower voltages may occur within the electron gun assembly.
  • a cathode ray tube housing an electron gun assembly mounted within a sealed evacuated envelope formed substantially of electrically insulated material and having a first coating of electrically conductive material on part of its external surface and a second coating of electrically conductive material on part of its internal surface, the said conductive coatings forming a capacitor.
  • the resistor has a conductive element which provides the resistance of the resistor and is supported by a rigid member formed of electrically insulating material.
  • the said conductive element is in the form of a helix of resistive material
  • the rigid member is a hollow cylinder of insulating material, the helix being coaxial with the cylinder and disposed on the internal or the external surface of the cylinder.
  • FIG. 1 is a longitudinal sectional view of a cathode ray tube embodying the invention.
  • FIG. 2 is a longitudinal sectional view of part of the cathode ray tube of FIG. 1 on a larger scale.
  • FIG. 1 there is shown a cathode ray tube 10 having an electron gun assembly 11 mounted within a sealed evacuated envelope 12 formed substantially of electrically insulating material and having a first coating 13 of, electrically conductive material on part of its external surface and a second coating 14 of electrically conductive material on part of its internal surface.
  • the coatings 13 and 14 form a capacitor which is electrically connected to an electrode, which is the final anode 15, of the electron gun assembly 11 by a resistor 16 includcd in the assembly 11.
  • the electron gun assembly includes a thermionic cathode 17 mounted over a heater, a modulation electrode l8, and first, second and third anodes 19, 20 and 21 respectively, the secondanode 20 being connected directly to the final anode 15.
  • a modulation signal circuit is connected to apply a modulation signal between the modulation electrode 18 and the cathode 17, the modulation signal circuit supplying a voltage to the cathode 17 which voltage is varied to vary the intensity of the electron beam emitted by the cathode 17, the electrode 18 being maintained at a constant bias voltage.
  • the anodes 19, 20 and 21 are connected to supply circuits which provide voltages enabling these anodes together with the final anode 15 to form and focus the electron beam to a point on the screen.
  • Means, not shown, are also provided for deflecting the beam to desired positions, such means preferably being in the form of electromagnetic deflection coils located outside the envelope 12.
  • the first coating 13 on the envelope 12 consists of a layer of conductive graphite and extends over substantially the whole of the curved surface of a bulbous portion 22 of the envelope 12 which terminates at its wider end in a substantially flat face plate 23, one boundary of the coating 13 lying in a plane parallel to the face plate 23.
  • a small part of the bulbous portion 22 of the envelope 12 is formed by an electrically conductive connector 24, and a clearance is left between the coating 13 and the connector 24 so that they are electrically insulated from one another.
  • the connector 24 makes electrical contact with a first portion 25 of the second coating 14 which portion 25 is in the form of a layer of conducting graphite,the coating 14 having a second portion 26 which is in the form of a layer of aluminium which makes electrical connection with the first portion 25 at a common boundary 27 lying in a plane parallel to the face plate 23.
  • the inner surface of the face plate 23 is coated with a layer 28 of electroluminescent material which is overlain by part of the second portion 26 of the coating 14.
  • the first portion 25 of the coating 14 extends from the common boundary 27 to the smaller end of the bulbous portion 22 of the envelope 12 and some distance into a cylindrical neck 29 which forms the remaining por tion of the envelope 12,'the portion 25 ending in the neck 29 at a boundary 30 which lies in a plane parallel to the face plate 23 and is closer to the face plate 23 than is the resistor 16.
  • resistor 16 Details of the resistor 16 and the manner in which it is mounted in the envelope 12 are shown in FIG. 2.
  • the resistor 16 has a conductive element 31 which provides the resistance of the resistor 16 is supported by a rigid member 32 formed of electrically insulating material, for example, glass.
  • the conductive element 31 is in the form of a helix of resistive material, for example a resistive material containing graphite as its primary constituent, and the rigid member 32 is a hollow cylinder, the helix being coaxial with the cylinder and disposed on the internal surface of the cylinder.
  • a protective layer 33 of chromic oxide overlies the conductive element 31, but may be omitted.
  • the element 31 is shown disposed on the internal surface of the member 32, it may be disposed on the external surface of the member 32 with consequent rearrangement of the electrical contacts to be described below.
  • That end of the element 31 which is the nearer to the portion 25 of the coating 14 is electrically connected to it through a plurality of spring contacts 34, an outwardly directed flange 35,of a flanged metal member 36, and a further plurality of spring contacts 37, the contacts 34 and 37 being welded to the flange 35 and having their respective free ends in electrical contact with the said end of the element 31 and the portion 25 of the coating 14 as shown in FIG. 2.
  • the conductive element 31 is terminated at each of its ends by respective short lengths 31 and 31 of low resistance graphite deposited around the internalcircumference of the rigid member 32.
  • the spring contacts 34 make electrical and physical contact with the length 31.
  • the flanged member 36 has an inwardly directed flange 38 which defines a circular aperture through which the electron beam passes in operation.
  • the other end of the element 31 is electrically connected to the final anode through a plurality of spring contacts 39 welded to an outwardly directed flange 40 of the anode 15.
  • the inner coating 14 is electrically connected to the anode 15 by the resistor. 16.
  • the spring contacts 39 make electrical and physical contact with the length 31".
  • the lengths 31 and 31" may be omitted, and the spring contacts 34 and 39 make contact directly with the ends of the element 31'.
  • the flanged member 36 is secured to the flange 40 of the anode 15 by a plurality of insulating rods 41, for example of glass, having short lengths 42 of stiff wire embedded coaxially in their ends and welded to the flanges 35 and 40.
  • the resistor 16 which is mechanically supported by the spring contacts 39 and 34 which hold the rigid member 32 coaxial with the trajectory of the electron beam, is mounted in the electron gun assembly 11.
  • a tube getter 43 is also included in the electron gun assembly, being mounted on the flange 35 of the member 36.
  • the coatings 13 and 14 form a capacitor which can be used in a smoothing circuit for a high voltage supply circuit for use with the tube 10.
  • This capacitor contains a charge during operation of the tube, the connector 24 i being supplied with a positive voltage, and the external coating 13 being connected to earth.
  • the anodes 15 t and 20 are normally maintained at the same voltage as the internal coating 14 in operation, but may undergo a lowering of voltage if, as sometimes occurs when the electron beam constitutes a high emission current, the beam is partially intercepted by one or both of the anodes 15 and 20, these electrodes being electrically connected to the connector 24 only by the resistor 16.
  • a flashover from one of the anodes 15 and 20 to one or more of the other electrodes, even the heater, having lower voltages may occur within the electron gun assembly.
  • the resis tance between the said capacitor formed by the coatings l3 and 14 and one or more of the electrodes 18 to 21 is reduced, butthe resistance of the resistor 16 is chosen to be sufficient even in these circumstances to restrict the current flowing from the said capacitor to a value which will not damage any of the supply circuits or the modulation circuit, which may contain components such as solid state devices which are vulnerable to damage by high current levels, which are connected to the electrodes 18 to 21 in operation.
  • the resistance provided by the element 31 should be at least 1000 ohms.
  • the said conductive element is in the form of a continuous film supported on an insulating base, and in a further embodiment the conductive element is in the form of a hollow cylinder. of conductive material having sufficient rigidity to support itself and thus constituting the resistor.
  • this stray capacitance In a tube with magnetic deflection, the principal contributor in the immediate surroundings to this stray capacitance is the deflector yoke. Before a flashover this stray capacitance is charged to the full voltage of, the high voltage supply connected to the high voltage connector corresponding to the connector 24. When a fla'shover occurs, the charge from this stray capacitance flows unimpeded into circuits connected to the gun assembly and, if the stray capacitance is large enough, can deliver sufficient energy to damage semiconductor devices.
  • a cathode ray tube having an electron gun assembly mounted within a sealed evacuated envelope formed substantially of electrically insulating material and having a first coating of electrically conductive material on part of its external surface and a second coating of electrically conductive material on part of its internal surface, the coatings forming a capacitor which is electrically connected to the final anode of the electron gun assembly by a resistor included in the assembly, a small part of the envelope being formed by an electrically conductive connector, and a clearance being left between the external coating and the connector so that they are electrically insulated from one another, the connector making electrical contact with a first portion of the second coating which portion is in the form of a layer of conducting graphite, the internal coating having a second portion which is in the form of a layer of aluminium which makes electrical connection with the first portion at a common boundary lying in a plane, the said resistor having a conductive element which provides the resistance of the resistor and is supported by a rigid member formed of electrically insulating material and is in the form of a

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  • Vessels, Lead-In Wires, Accessory Apparatuses For Cathode-Ray Tubes (AREA)
US376166A 1972-07-05 1973-07-03 Cathode ray tube having cylinder with internal resistive helix Expired - Lifetime US3909655A (en)

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Application Number Priority Date Filing Date Title
GB3151472 1972-07-05

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US (1) US3909655A (enExample)
FR (1) FR2191813A7 (enExample)
GB (1) GB1353872A (enExample)

Cited By (17)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4070597A (en) * 1976-04-22 1978-01-24 General Electric Company Multi-apertured single plate matrix lens
US4101803A (en) * 1977-06-01 1978-07-18 Zenith Radio Corporation Arc suppression and static elimination system for a television crt
US4161673A (en) * 1977-06-30 1979-07-17 Zenith Radio Corporation Arc suppression and static elimination system for a television CRT
US4207493A (en) * 1978-09-26 1980-06-10 Rca Corporation Cathode ray tube arc-over protection
US4220893A (en) * 1976-07-26 1980-09-02 Zenith Radio Corporation Electrically resistive arc suppressor shadowing getter flash
US4234816A (en) * 1979-04-16 1980-11-18 Gte Products Corporation Cathode ray tube with internal arc suppressor and protective spark gap
US4323813A (en) * 1980-01-23 1982-04-06 Rca Corporation Spring-loaded resistive lens structure for electron gun
US4350925A (en) * 1980-07-09 1982-09-21 Rca Corporation Main lens assembly for an electron gun
US4491764A (en) * 1982-09-27 1985-01-01 Rca Corporation Arc suppression structure for an electron gun
US4514661A (en) * 1982-09-27 1985-04-30 Rca Corporation Arc-suppression means for an electron gun having a split electrode
US4531075A (en) * 1982-09-27 1985-07-23 Rca Corporation Electron gun having arc suppression means
US4554481A (en) * 1983-10-28 1985-11-19 Rca Corporation Electron discharge device having a ceramic member with means for reducing luminescence therein
US4713879A (en) * 1985-03-28 1987-12-22 U.S. Philips Corporation Method of manufacturing a device having an electric resistance layer and the use of the method
US4899079A (en) * 1984-03-12 1990-02-06 U.S. Philips Corporation Cathode ray tube
US4961023A (en) * 1988-09-21 1990-10-02 U.S. Philips Corporation Cathode ray tube including a helical focusing lens
US5430350A (en) * 1994-03-09 1995-07-04 Chunghwa Picture Tubes, Ltd. Electron gun support and positioning arrangement in a CRT
US6356015B2 (en) 1999-01-21 2002-03-12 Imaging & Sensing Technology Corporation Getter flash shield

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3295008A (en) * 1963-06-27 1966-12-27 Sylvania Electric Prod Electron discharge device with current surge attenuating resistance
US3355617A (en) * 1964-07-30 1967-11-28 Motorola Inc Reduction of arcing between electrodes in a cathode ray tube by conducting coating of resistance material on inner wall of tube neck
US3375390A (en) * 1966-01-03 1968-03-26 Gen Electric Electron optical system having spiral collimating electrode adjacent the target

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3295008A (en) * 1963-06-27 1966-12-27 Sylvania Electric Prod Electron discharge device with current surge attenuating resistance
US3355617A (en) * 1964-07-30 1967-11-28 Motorola Inc Reduction of arcing between electrodes in a cathode ray tube by conducting coating of resistance material on inner wall of tube neck
US3375390A (en) * 1966-01-03 1968-03-26 Gen Electric Electron optical system having spiral collimating electrode adjacent the target

Cited By (17)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4070597A (en) * 1976-04-22 1978-01-24 General Electric Company Multi-apertured single plate matrix lens
US4220893A (en) * 1976-07-26 1980-09-02 Zenith Radio Corporation Electrically resistive arc suppressor shadowing getter flash
US4101803A (en) * 1977-06-01 1978-07-18 Zenith Radio Corporation Arc suppression and static elimination system for a television crt
US4161673A (en) * 1977-06-30 1979-07-17 Zenith Radio Corporation Arc suppression and static elimination system for a television CRT
US4207493A (en) * 1978-09-26 1980-06-10 Rca Corporation Cathode ray tube arc-over protection
US4234816A (en) * 1979-04-16 1980-11-18 Gte Products Corporation Cathode ray tube with internal arc suppressor and protective spark gap
US4323813A (en) * 1980-01-23 1982-04-06 Rca Corporation Spring-loaded resistive lens structure for electron gun
US4350925A (en) * 1980-07-09 1982-09-21 Rca Corporation Main lens assembly for an electron gun
US4491764A (en) * 1982-09-27 1985-01-01 Rca Corporation Arc suppression structure for an electron gun
US4514661A (en) * 1982-09-27 1985-04-30 Rca Corporation Arc-suppression means for an electron gun having a split electrode
US4531075A (en) * 1982-09-27 1985-07-23 Rca Corporation Electron gun having arc suppression means
US4554481A (en) * 1983-10-28 1985-11-19 Rca Corporation Electron discharge device having a ceramic member with means for reducing luminescence therein
US4899079A (en) * 1984-03-12 1990-02-06 U.S. Philips Corporation Cathode ray tube
US4713879A (en) * 1985-03-28 1987-12-22 U.S. Philips Corporation Method of manufacturing a device having an electric resistance layer and the use of the method
US4961023A (en) * 1988-09-21 1990-10-02 U.S. Philips Corporation Cathode ray tube including a helical focusing lens
US5430350A (en) * 1994-03-09 1995-07-04 Chunghwa Picture Tubes, Ltd. Electron gun support and positioning arrangement in a CRT
US6356015B2 (en) 1999-01-21 2002-03-12 Imaging & Sensing Technology Corporation Getter flash shield

Also Published As

Publication number Publication date
GB1353872A (en) 1974-05-22
FR2191813A7 (enExample) 1974-02-01

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