US3210596A - Device provided with a cathode-ray tube protection circuit for crt activated by power switch - Google Patents

Device provided with a cathode-ray tube protection circuit for crt activated by power switch Download PDF

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Publication number
US3210596A
US3210596A US228546A US22854662A US3210596A US 3210596 A US3210596 A US 3210596A US 228546 A US228546 A US 228546A US 22854662 A US22854662 A US 22854662A US 3210596 A US3210596 A US 3210596A
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Prior art keywords
anode
cathode
sections
voltage
ray tube
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US228546A
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English (en)
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Gier Johannes De
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US Philips Corp
North American Philips Co Inc
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US Philips Corp
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N3/00—Scanning details of television systems; Combination thereof with generation of supply voltages
    • H04N3/10—Scanning details of television systems; Combination thereof with generation of supply voltages by means not exclusively optical-mechanical
    • H04N3/16—Scanning details of television systems; Combination thereof with generation of supply voltages by means not exclusively optical-mechanical by deflecting electron beam in cathode-ray tube, e.g. scanning corrections
    • H04N3/20—Prevention of damage to cathode-ray tubes in the event of failure of scanning

Definitions

  • the invention relates to a device provided with a cathode-ray tube comprising an electron gun which at least consists of a cathode, a control electrode, a first anode and a second anode.
  • the invention further relates to a circuit arrangement for energizing the first anode.
  • the electrode to which the fluorescent screen of the cathode-ray tube is connected usually consists of a conductivelayer provided on the inner side of the bulb. This electrode generally has a comparatively high capacitance with respect to ground, and consequently a considerable charge, since this electrode is connected to a very high voltage. After the device has been switched off, this high voltage charge may be retained for a comparatively long time.
  • the cathode ray is usually suppressed only in part. Consequently, part of the electrons still emanating from the glowing cathode may flow to the fluorescent screen then still strongly positive, and impinge thereon with a high velocity, as a result of which a burn may occur, since the electric charge on the screen and the electrodes connected therewith are neutralized only slowly. If, however, the ray could pass at its full strength, the screen could be discharged before the deflection voltages have disappeared completely.
  • the burning-in of the screen after switching off such a device is avoided by providing a first anode which consists of two parts to which approximately equal potentials are supplied by means of switching circuits having different discharge times in a manner such that if the potential of one of the anode parts drops below that of the other part, the cathode ray no longer impinges upon the screen. It is then possible to suppress the ray completely, but the ray is preferably deflected so that it strikes the second anode and discharges it. Since the second anode is also connected to the electrode which is provided on the inner wall of the bulb, this electrode, and consequently also the screen, are discharged. In the case where the ray is completely suppressed, these electrodes remain charged, which may be unpleasant upon touching.
  • FIG. 1 shows diagrammatically a circuit arrangement of a device in accordance with the invention
  • FIGS. 2 and 3 show in greater detail two embodiments in accordance with the invention.
  • reference numeral 1 denotes a cathode-ray tube comprising a fluorescent screen 2 and an electron gun consisting of a cathode 3 heated by a heat ing member 4, a control electrode 5 with which the intensity of the cathode ray can be controlled, a first anode 6 consisting of two parts, a second anode 7, 8 and a focusing electrode 9.
  • the parts 7 and 8 of the second anode are electrically connected together in the tube and the part 8 is connected electrically 'by means of a spring 10 to the conductive coating 11 on the inner wall of the tube 1.
  • the electrodes 7, *8 and 11 have a capacitance with respect to ground which is represented diagrammatically by the capacitor 12.
  • the electrode 11 comes also into contact with the fluorescent screen 2.
  • the electrode 11 is connected to a source of high voltage 14 (16 kv.) which derives its voltage from the horizontal deflection circuit.
  • High voltage source 14 is connected at 15 to the synchronisation separating circuit (not shown) and further to the positive terminal of the power supply apparatus 16.
  • Deflection coils 37 are arranged around the neck of the cathode-ray tube in normal manner.
  • the efficiency diode circuit 17 of the deflection circuit 14 supplies the positive voltage for the parts of the first anode 6 and the focussing electrode 9 through potentiometers 18 and 19, respectively.
  • the two parts of the first anode 6 are connected to the circuit arrangement 20, two embodiments of which are shown in FIGS. 2 and 3.
  • the control electrode 5 is connected to a video amplifier 21 and the cathode 3 to the brightness control consisting of resistors 22, 23, 24, 25 and a capacitor 26.
  • the control voltages may also be supplied to the cathode 3, in which case the electrode 5 is connected to the brightness control.
  • a switch 38 controls the supply of power to the system.
  • the first anode 6 is divided into two parts by a diagonal cut, so that parts 6a and 6b are formed, which are separated along a plane which is at a sharp angle to the axis of the parts.
  • the part 6a of the first anode is connected to the capacitor 27 and its potential is supplied through resistors 28, 29 which constitute a voltage divider.
  • the part 612 of the first anode 6 is connected to a potentiometer 32, the ends of which are connected to resistors 30 and 31.
  • the potentiometer 32 renders it possible to make the voltage of the part 6b exactly equal to that of the part 6a.
  • the electron beam passes in the direction I. Since the circuit branch 30, 31, 32 does not include a capacitor, its R.C. time constant is very short.
  • the device If the device is switched oif, the voltage of 6b will decrease much more rapidly than that of 6a, as a result of which due to the diagonal cut, the part 6b causes a deflection of the ray in the direction II, so that this ray impinges on the second anode 7 and discharges the electrodes 7, 8 and 11 before the deflection due to the voltage difierence between electrodes 6a and 6b has decreased to zero.
  • the circuit arrangement may also be simplified, as shown in FIG. 3, in which at the same time another embodiment of the first anode is illustrated.
  • the part 60 is then connected to a capacitor 33 and through a resistor 34 of high value to the anode part 6d and the common point of a voltage divider constituted by resistors 35 and 36.
  • the voltages of the parts 60 and 60! will then always become equal. After the receiver is switched off, the voltage of 6d will decrease more rapidly than that of 60. Since 6d has a small aperture through which the ray passes the control effect of 6d is so great that the ray is suppressed completely. As has been indicated already, the disadvantage of this arrangement is that the electrodes 7, 8 and 11 remain at a high voltage, which may be unpleasant if the device is opened, for example, for checking, adjusting or repairing purposes.
  • the embodiment of the first anode of FIG. 2 is consequently preferred. It should be noted that the circuit arrangement of FIG. 3 may also be used with the construction of the anode parts 6a and 6b shown in FIG. 2, and conversely.
  • the invention is of particular importance for tubes without an ion trap, and especially if the deflection voltages are produced by means of transistors, since in this case, after the device has been switched off, they drop to zero substantially immediately, because there are no tubes with afterglowing cathodes present.
  • the voltage of the supply apparatus 16 designated in the drawing by is, for example, 200 v.
  • the high voltage supplied by the circuit arrangement 14 is 16 kv. and the voltage supplied by the efliciency diode circuit to the focusing electrode 9 and the circuit arrangement 20 is approximately 800 v.
  • the resistors and capacitors shown in the drawing may have, for example, the following values.
  • Resistor 22 9 47,000 Resistor 23 Q 2,200 Resistor 24 Q 6,000 Resistor 25 "52.. 21,300
  • Capacitor 12 pF 1,500 Capacitor 26 pF 80,000 Capacitors 27, 33, each pF 68,000
  • a cathode ray tube arrangement comprising a cathode, a first anode comprising first and second sections insulated from one another, a second anode, a source of anode voltage, first and second circuit means for coupling said voltage source to said first and second sections, respectively, said first and second circuit means having diflerent discharge time constants, and means for eflectively removing said voltage source from said first and second sections thereby to diminish the anode voltages of said first and second sections in accordance with the said respective time constants of said first and second circuit means.
  • a cathode ray tube arrangement comprising a fluorescent screen, an electron gun for directing an electron beam to said screen, said electron gun comprising a cathode, a first anode and a second anode, said first anode comprising first and second sections insulated from one another, a source of anode voltage, first and second circuit means for coupling said voltage source to said first and second sections, respectively, to provide approximately equal potentials thereto, said first and second circuit means having different discharge time constants, and means for effectively removing said voltage source from said first and second sections thereby to diminish the anode voltages of said first and second sections in accordance with the said respective time constants of said first and second circuit means, said first and second sections being arranged within said tube so as to deflect the electron beam away from said screen at a given inequality of the anode potentials of said first and second sections.
  • each of said first and second sections comprises a truncated right circular cylinder longitudinally displaced from one another along the axis of said cathode ray tube so as to produce a deflection field during the decay of said anode potentials having a transverse component which directs said beam to said second anode.
  • a cathode ray tube arrangement comprising a cathode, a first anode comprising first and second spaced apart truncated cylindrical sections, each of said sections having a matching truncated surface separated from each other by a diagonal cut along a plane which forms an acute angle with the longitudinal axis of said cylindrical sections, a second anode, a source of anode voltage, first and second circuit means for coupling said voltage source to said first and second sections, respectively, said first and second circuit means having different discharge time constants, and means for deenergizing said voltage source thereby to diminish the anode voltages of said first and second sections in accordance with the said respective time constants of said first and second circuit means.
  • a cathode ray tube arrangement comprising a fluorescent screen, an electron gun for directing an electron beam to said screen, said electron gun comprising a cathode, a first anode and a second anode, said first anode comprising first and second spaced truncated cylindrical sections separated from one another by a plane which forms an acute angle with the longitudinal axes of said cylindrical sections, said first and second sections being electrically insulated from one another, a source of anode voltage, first circuit means comprising a resistance-capacitance network for coupling said first section to said voltage source, second circuit means coupling said second section to said voltage source, said first circuit means having a longer discharge time constant than said second circuit means, said first and second circuit means being arranged to supply approximately equal anode potentials to said first and second sections, and means for eifectively decoupling said voltage source from said first and second sections thereby to diminish the anode voltage of said first and second sections in accordance with the said respective time constants of said first and second circuit means where
  • a cathode, ray tube arrangement comprising a cathode a first anode comprising a cylinder longitudinally positioned within said tube and divided into two sections along its longitudinal axis, a second anode, a source of anode voltage, first circuit means for coupling said voltage source to one of said cylindrical sections, second circuit means for coupling said voltage source to the other one of said two sections, and first and second circuit means having different discharge time constants, and means for deenergizing said voltage source thereby to initiate a decay in the anode voltages of said one and said other cylindrical sections in accordance with the said respective time constants of said first and second circuit means.
  • first anode cylinder is divided into two separate sections each of which comprises a truncated right circular cylinder, said two sections being electrically insulated from one another and said first and second circuit means being arranged to supply approximately equal potentials to said first and second sections.
  • a cathode ray tube arrangement comprising a fluorescent screen, an electron gun for directing an electron beam to said screen, said electron gun comprising a cathode, a first anode and a second anode, said first anode comprising first and second spaced sections insulated from one another, said first section comprising a substantially disc-shaped member having an aperture for passage therethrough of said electron beam and said second section comprising a cylindrical member, a source of anode voltage, first and second circuit means for coupling said voltage source to said first and second sections, respectively, said first and second circuit means having different discharge time constants, means for effectively removing said voltage source from said first and second sections thereby to diminish the anode voltage of said first and second sections in accordance with the said respective time constants of said first and second circuit means.
  • said second circuit means comprises a resistance-capacitance network having a substantially longer discharge time constant than said first circuit means.
  • a cathode ray tube arrangement comprising a fluorescent screen, an electron gun for directing an electron beam to said screen along a given path, said electron gun comprising a cathode, a first anode and a second anode, said first anode comprising first and second longitudinally spaced sections insulated from one another, a source of anode voltage, first circuit means for coupling said voltage source to said first section to supply a given potential thereto, second circuit means for coupling said voltage source to said second section to supply a potential thereto having a predetermined relationship to the potential of said first section thereby to direct said electron beam to said screen, and means for effectively removing said voltage source from said first and second sections, said first and second circuit means having different discharge time constants whereby a deflection field is produced by the decay in anode potential of said first and second sections, said field having a component transverse to said given path upon a given variation in said predetermined anode potential relationship whereby said electron beam is deflected away from said screen.

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  • Engineering & Computer Science (AREA)
  • Multimedia (AREA)
  • Signal Processing (AREA)
  • Transforming Electric Information Into Light Information (AREA)
  • Details Of Television Scanning (AREA)
  • Control Of Indicators Other Than Cathode Ray Tubes (AREA)
  • Manufacture Of Electron Tubes, Discharge Lamp Vessels, Lead-In Wires, And The Like (AREA)
US228546A 1961-10-09 1962-10-05 Device provided with a cathode-ray tube protection circuit for crt activated by power switch Expired - Lifetime US3210596A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
NL270069A NL270069A (no) 1961-10-09 1961-10-09

Publications (1)

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US3210596A true US3210596A (en) 1965-10-05

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US (1) US3210596A (no)
BE (1) BE623370A (no)
DE (1) DE1279216B (no)
ES (1) ES281335A1 (no)
GB (1) GB980210A (no)
NL (1) NL270069A (no)

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0036901A1 (de) * 1980-04-01 1981-10-07 Norddeutsche Mende Rundfunk KG Anordnung zur Erzeugung von gebündelten Elektronenstrahlen in einem Vakuum-Entladungsgefäss

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2096987A (en) * 1932-11-15 1937-10-26 Ardenne Manfred Von System for energizing a cathode ray tube
US2131203A (en) * 1931-03-27 1938-09-27 Loewe Opta Gmbh Television method
US2562242A (en) * 1950-06-06 1951-07-31 Du Mont Allen B Lab Inc Split anode for bent gun ion trap cathode-ray tubes

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2131203A (en) * 1931-03-27 1938-09-27 Loewe Opta Gmbh Television method
US2096987A (en) * 1932-11-15 1937-10-26 Ardenne Manfred Von System for energizing a cathode ray tube
US2562242A (en) * 1950-06-06 1951-07-31 Du Mont Allen B Lab Inc Split anode for bent gun ion trap cathode-ray tubes

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Publication number Publication date
BE623370A (no)
NL270069A (no) 1964-07-27
GB980210A (en) 1965-01-13
DE1279216B (de) 1968-10-03
ES281335A1 (es) 1963-03-16

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