US3024380A - Cathode ray tube gun construction - Google Patents

Cathode ray tube gun construction Download PDF

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Publication number
US3024380A
US3024380A US473213A US47321354A US3024380A US 3024380 A US3024380 A US 3024380A US 473213 A US473213 A US 473213A US 47321354 A US47321354 A US 47321354A US 3024380 A US3024380 A US 3024380A
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US
United States
Prior art keywords
convergence
lens
tube
electrode
beams
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
US473213A
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English (en)
Inventor
Burdick Glen Alden
Krawitz Max
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
Priority to NL202514D priority Critical patent/NL202514A/xx
Priority to BE543332D priority patent/BE543332A/xx
Priority to NL94232D priority patent/NL94232C/xx
Application filed by Sylvania Electric Products Inc filed Critical Sylvania Electric Products Inc
Priority to US473213A priority patent/US3024380A/en
Priority to GB34635/55A priority patent/GB799533A/en
Priority to DES46598A priority patent/DE1124160B/de
Priority to FR1139940D priority patent/FR1139940A/fr
Application granted granted Critical
Publication of US3024380A publication Critical patent/US3024380A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J31/00—Cathode ray tubes; Electron beam tubes
    • H01J31/08—Cathode ray tubes; Electron beam tubes having a screen on or from which an image or pattern is formed, picked up, converted, or stored
    • H01J31/10—Image or pattern display tubes, i.e. having electrical input and optical output; Flying-spot tubes for scanning purposes
    • H01J31/20—Image or pattern display tubes, i.e. having electrical input and optical output; Flying-spot tubes for scanning purposes for displaying images or patterns in two or more colours
    • H01J31/201—Image or pattern display tubes, i.e. having electrical input and optical output; Flying-spot tubes for scanning purposes for displaying images or patterns in two or more colours using a colour-selection electrode
    • H01J31/203—Image or pattern display tubes, i.e. having electrical input and optical output; Flying-spot tubes for scanning purposes for displaying images or patterns in two or more colours using a colour-selection electrode with more than one electron beam
    • H01J31/205—Image or pattern display tubes, i.e. having electrical input and optical output; Flying-spot tubes for scanning purposes for displaying images or patterns in two or more colours using a colour-selection electrode with more than one electron beam with three electron beams in delta configuration
    • 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
    • H01J29/46—Arrangements of electrodes and associated parts for generating or controlling the ray or beam, e.g. electron-optical arrangement
    • H01J29/48—Electron guns
    • H01J29/51—Arrangements for controlling convergence of a plurality of beams by means of electric field only
    • 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
    • H01J29/46—Arrangements of electrodes and associated parts for generating or controlling the ray or beam, e.g. electron-optical arrangement
    • H01J29/58—Arrangements for focusing or reflecting ray or beam
    • H01J29/62—Electrostatic lenses

Definitions

  • This invention relates to electron discharge devices, such as cathode ray tubes. More specifically, it relates to improved forms of electrostatic lenses, and associated structures for use in such devices. While the invention, as will be apparent after reading the specification and claims, is capable of broad application, it will be illustrated here in association with a color television picture tube.
  • Electrostatic defleeting plates or electrostatic converging lenses may also be employed at the exit of the guns for this purpose.
  • the electrostatic convergence type of color gun structure is thought preferrable to the electromagnetic type because of the simpler structures, the reduced number of external components, and the reduced number of power supplies required.
  • Tubes employing electrostatic convergence have been commercially produced in the 15 inch envelope size with bipotential electrostatic convergence lenses. This invention relates to convergence lenses of this type.
  • bipotential lens structures used to produce beam convergence two electrodes are employed in the lens producing structure, one electrode, the so-called convergence electrode, being a cylinder or cup extending over the open ends of three parallel, triangularly disposed, electron guns towards the screen of the tube and operated at a potential equal to that applied to the last gun electrodes.
  • the other portion of the lens producing structure may be an extension of the aquadag anode coating on the inside of the cathode ray tube neck which overlaps the convergence electrode, or it may be a cylinder supported by the gun mount. It is operated at the anode potential of the cathode ray tube, a potential much higher than any other applied to the electron gun of the tube.
  • the final anode voltage is ordinarily of the order of 20 kilovolts and the static volt- ICQ age applied to the convergence electrode for converging the beams at the center of the screen is approximately half the anode voltage, about 10 kilovolts.
  • the ratio of convergence electrode voltage to anode voltage is therefore about 1:2.
  • cathode ray tubes of this type it is customary in cathode ray tubes of this type to bring the convergence electrode voltage lead out through the base of the cathode ray tube, since to take it directly out through the glass neck of the tube would introduce special structural problems in the tube as well as in structures which must be fitted around the neck of the tube.
  • the convergence voltage is 10 kilovolts
  • Electrolysis of the glass of the stem may be harmfully increased. Leakage on the glass outside of the stem but inside of the tube base occurs due to undesired material collecting on the. glass, such as dirt or moisture. Arc-over sometimes occurs in the space within the base due to carelessly placed leads and the effects of humidity. While the base pin to which the convergence lead is connected may be intentionally placed as far away as possible from the pins to which other, lower voltage, connections are made, the placement of the leads within the base may be faulty, bringing them too close together and facilitating breakdown. Similar troubles may be encountered within the socket and within the leads which lead up to the socket.
  • FIG. 1 is a side view in partial cross-section of a cathode ray tube embodyingapplicants invention
  • FIG. 2 is a side view in partial cross-section of a gun employing electrostatic convergence as taught by the prior art
  • FIG. 3 is an end view looking into the convergence electrode of FIG. 2;
  • FIG. 4 is a view in partial cross-section of the convergence electrode end of the gun of the cathode ray tube of FIG. 1, illustrating one embodiment of applicants invention
  • FIG. 5 is a view in partial cross-section of a portion of the convergence lens structure of a color tube gun according to an alternative embodiment of applicants invention.
  • FIG. 6 is an end view, looking into the convergence electrode of FIG. 5.
  • FIG. 1 of the drawings illustrates the general scheme of a typical color television reproducing tube in which an aperture mask is utilized to assist in the production of a color picture.
  • the tube is provided with an envelope 10 into one end of which is sealed a multiple gun 12 capable of producing three cathode ray beams 14.
  • Connections to various electrodes of the gun portion of the tube are made by means of leads extending backwards from the mount to the base 16 where they penetrate the envelope of the tube (see FIG. 2) and are connected to the pins generally designated 13. Connections to the gun are not made through the neck portion 20 of the tube because they would interfere with the passage of tightly fitted auxiliary components which must be slid down over the neck of the tube.
  • the opposite viewing end of the tube is provided with phosphor dot bearing screen surface 24 and aperture mask 22 so disposed that the electron beams 14, will be caused to strike first the mask and then, finding apertures to travel on to the screen.
  • the beams are accelerated towards the screen after they leave the guns by means of anode 26, which may be found as a conductive coating on the inside of the cone of the tube connection to the coating being accomplished by means of a connec tive member penetrating the wall of the tube, such as the button 28 or the flanges utilized in some structures to seal on the face plate.
  • each one of the apertures 30 on the aperture mask 22 is associated with a group of three color phosphors 32 appearing on the screen portion of the tube.
  • the disposition of the guns, aperture mask, and screen dots, is such that, as the bundle of cathode ray beams 14 is directed through a given aperture 30, each of the beams strikes one of the three dots, so that if a beam is turned on the phosphor associated with the gun from which the beam emanates will be excited.
  • FIG. 2 illustrates a color gun which is capable of producing three beams and which is built according to the prior art.
  • the tri-color gun consists of three guns, 34, 36, and 38 mounted side by side so that the gun axes form the apices of a prism as best seen in the view of FIG. 1.
  • each of the guns 34, 36, and 38 is the same, only one of them is shown in section.
  • Each of the guns has a cathode'and heater portion 40, con tained within a first grid 42, a second grid 44, a third grid 46 and a fourth grid 48 all of which are generally tubular in nature and may or may not be provided with masking apertures 50, depending upon the individual design of the electron producing portion of the guns.
  • the cathodes 40, the first grids 42, to which color signals are supplied, and the second grids are ordinarily provided with separate leads to the outside of the tube, while the third grids are ordinarily tied together, as are the fourth grids.
  • the individual fourth grids 48 each extend into the rear wall of cup shaped convergence electrode 52.
  • Convergence electrode 52 extends in turn into the cathode ray tube neck portion 54 of the final anode26.
  • the conventional convergence electrode structure is shown as a cup having cylinder walls'of a length equal to the diameter of the cup. For illustrative purposes, the course of the conecting lead from the convergence electrode voltages is shown as it extends to the tube base.
  • the interaction of the convergence electrode and the final anode when the proper operating potentials are applied produces a field which has a general configuration as shown by the equipotential lines 56.
  • the action of the convergence lens field on electrons which have left the cathode and have been shaped, according to conventional techniques into a beam traveling from the upper gun 34 is illustrated by the trajectory shown as the dark line 58 which represents the path taken by a typical electron traveling from the cathode 40 of the gun 34 to a target electrode or plane 59 which, for our purposes, may be considered the equivalent of the aperture mask 22 of FIG. 1.
  • the course of an electron leaving the gun is gradually altered as it traverses the convergence portion of the field towards the axis of the tube.
  • the electron As the electron passes into the divergent portion of the field, its course is once more altered, this time in the opposite direction, so that its final path is close to and gradually convergent upon the axis of the tube. If allowed to continue toward the aperture mask undeflected, the electron will eventually be on the axis of the tube when it reaches the mask.
  • FIG. 4 illustrates one embodiment of applicants invention.
  • the beam generating portions of the guns have been omitted for the purposes of simplicity, but they will be understood to be the same as those generally illustrated in FIG. 2.
  • the cup-shaped convergence electrode 52 receives the ends of the fourth grids 48 in apertures in an end closure wall or bottom 60.
  • the cup which forms the electrode 52 is approximately half as long as the cup is wide.
  • the modified field which is produced by this sort of structure is illustrated by the equipotential lines 62, and the relative difierence in trajectory between an electron stream accelerated at the potentials utilized with the gun of FIG. 2 and the trajectory followed by electrons accelerated in the fields made possible by this structure has been shown by sketchin in the equivalent previous trajectory 66 alongside the new trajectory 64.
  • the altered eifect of the lens produced by the structure of FIG. 4 results from deliberate shaping of the otherwise normal fields developed by a simple two-cylinder bipotential electrode structure as will be seen from the ensuing discussion.
  • the converging action. of a simple bipotential lens upon spaced electron beams results from bending of the beams as they pass through the converging and diverging fields within the associated axially aligned cylindrical electrodes, the converging field being located within the electrode to which the lower potential is applied and the diverging field being located within the electrode to which the higher potential is applied.
  • the strength of the lens depends upon the strength of the fields produced in the cylinders and the strength of the fields, in turn, is generally proportional to the potential difference between the electrodes. Because the converging field has a greater effect upon the electron beams than the diverging field, the net effect of the simple bipotential lens on separate, parallel beams is a change in direction as the beams leave the high potential side of the lens.
  • the change in direction is away from parallel and towards the extended line of the lens axis.
  • An increase in strength of the lens produced by increasing the difference of potential between the electrodes, shortens the distance at which a given, non-axial, electron beam will cross the lens axis after leaving the lens field.
  • reduction of the convergence electrode potential so as to meet the problems set forth in the preamble above is accomplished by accepting the stronger field which results from the increase in potential difference across the lens while deliberately altering the field configuration within the lens in such a way as to reduce the efiect of the strengthened lens upon the electron bearns. This is done by shortening the convergence electrodes so as to cause interference between the convergence field and the end wall portion of the electrode, reducing the curvature of the equipotential lines in thi region, and so reducing the convergent effect of the lens. Since the focal length of the gun assembly is principally determined by other conditions and so is fixed, the weakened shaped lens 6 produced by the shorter cup compensates for the increased strength of the lens due to the greater field strength.
  • the nature of the field configuration utilized in the shaped lens of FIG. 4 is demonstrated by the equipotential field lines 62. Since the end closure portion of the cup 60 has rotational dissymmetry as a result of the gaps at the points of entry of the fourth grid electrodes 48, and since there are plane electrode areas present in the back of the cup as well, the curvature of the equipotential lines in the region of the field closest to the back of the cup and on the lenss axis is no longer regular, and smooth as shown in FIG. 2 where the field is free of shaping, but may be characterized as flattened in the region of the plane surfaces and more sharply curved in the regions radially outward of the apertures.
  • the overall effect is one of reduced field curvature at the points of entry of the beams and so bending of the beams as they travel through the lens is reduced.
  • the potential gradient is thereby reduced at the points of electron entry from that value of potential gradient established adjacent the planar surfaces of the closure portion of cup 60.
  • Guns employing the 1:2 length to width ratio in the convergence electrode have been found to have a ratio of fourth grid to anode voltage of approximately .25, and require, for example, about 8 kilovolts for convergence when used with an anode supply of 27 kilovolts. It has been found that by experiment the optimum value of depth to width ratio for the convergence electrode cup dimensions is in the neighborhood of .5. If this value is increased, the undesirable effects of increasing the length of the tube employing such an electrode and increasing the required convergence voltage are produced.
  • the focussing effect of the shaped con vergence lens is increased with the result that too much focussing may be accomplished in the convergence lens leaving no room for the accomplishment of focussing in the focussing lenses.
  • the accomplishment of concurrent convergence and focussing in a single lens while advantageous from the point of view of simplified, shortened gun structures is disadvantageous in that with the elimination of the focussing electrodes, limiting apertures would be required in the cylindrical electrode adjacent and connected to the convergence electrode.
  • the current drawn by this arrangement would be undesirably high, requiring an undesirably expensive power supply capable of supplying substantial current at a high voltage.
  • FIGS. 5 and 6 show an alternative embodiment of the invention in which the contours of the convergence portion of a bipotential lens are shaped by means of axial pin 68, mounted centrally of the bottom of the convergence electrode cup and of the apertures formed by the fourth grid cylinders. Suitable proportioning of the pin length to the cup length produces the modified field shape shown by the contour lines 72 outlining the equipotential lines.
  • This arrangement produces a shaped field which is rotationally symmetrical with respect to the axis of the cylinder, being somewhat in the nature of dimpled hemispherical surface which is suitable for converging multiple beams at a lower voltage.
  • the structure is inferior to the structure of FIG. 4 in one respect, namely, that it is somewhat longer, calling for greater tube length in color television applications. Further shaping of the field may be accomplished by changing the dimensions and shape of the field shaping pin.
  • the configuration of the convergence portion of the bipotential lens field may be shaped according to the particular needs of an electronic structure by placing less reliance on the back Wall of the cup electrode, or eliminating it altogether and depending upon changes in the shapes of the end portions of the electron beam supplying electrodes where they project into the convergence field.
  • the bottom of the convergence electrode cup may be omitted, depending upon the fourth grid electrodes entirely for shaping of the convergence field.
  • An electron discharge device having: means for producing and directing a plurality of electron beams in the same direction; bipotential lens means having a convergence electrode for causing said beams to converge upon one another; said convergence electrode having means for reducing the potential gradient of said lens in the regions of entry of said electron beams, said last named means including a metallic electrode projecting into the field of said lens means centrally of said beams.
  • An electron discharge device having means for producing and directing a plurality of electron beams in the same direction, and bi-potential lens means positioned in the path of said beams having a convergence electrode with a tubular portion for causing said beams to converge upon one another, said convergence electrode having a given length and a metallic electrode projecting into said tubular portion centrally of said beams a distance less than said given length to shape the convergence lens by reducing the potential gradient of said lens in the regions of entry of said electron beams into the lens.

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  • Electrodes For Cathode-Ray Tubes (AREA)
  • Cathode-Ray Tubes And Fluorescent Screens For Display (AREA)
  • Vessels, Lead-In Wires, Accessory Apparatuses For Cathode-Ray Tubes (AREA)
US473213A 1954-12-06 1954-12-06 Cathode ray tube gun construction Expired - Lifetime US3024380A (en)

Priority Applications (7)

Application Number Priority Date Filing Date Title
NL202514D NL202514A (de) 1954-12-06
BE543332D BE543332A (de) 1954-12-06
NL94232D NL94232C (de) 1954-12-06
US473213A US3024380A (en) 1954-12-06 1954-12-06 Cathode ray tube gun construction
GB34635/55A GB799533A (en) 1954-12-06 1955-12-02 Improvements in and relating to electrostatic lens structures in electron discharge devices
DES46598A DE1124160B (de) 1954-12-06 1955-12-05 Becherfoermige elektrostatische Linse fuer eine Kathodenstrahlroehre
FR1139940D FR1139940A (fr) 1954-12-06 1955-12-06 Lentille électrostatique pour dispositif de décharge électronique

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US473213A US3024380A (en) 1954-12-06 1954-12-06 Cathode ray tube gun construction

Publications (1)

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US3024380A true US3024380A (en) 1962-03-06

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US473213A Expired - Lifetime US3024380A (en) 1954-12-06 1954-12-06 Cathode ray tube gun construction

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US (1) US3024380A (de)
BE (1) BE543332A (de)
DE (1) DE1124160B (de)
FR (1) FR1139940A (de)
GB (1) GB799533A (de)
NL (2) NL202514A (de)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3252032A (en) * 1963-12-13 1966-05-17 Sylvania Electric Prod Electrode assembly locating means
US3254251A (en) * 1962-07-06 1966-05-31 Rca Corp Cathode ray tube gun having nested electrode assembly
US3258625A (en) * 1964-07-27 1966-06-28 Aligned electrode holders for mount- ing parallel array of electron guns
US4590403A (en) * 1984-08-31 1986-05-20 Rca Corporation Color picture tube having an improved inline electron gun
US6559586B1 (en) 2000-02-08 2003-05-06 Sarnoff Corporation Color picture tube including an electron gun in a coated tube neck

Citations (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2165028A (en) * 1933-12-29 1939-07-04 Emi Ltd Television and the like system employing cathode ray tubes
US2173165A (en) * 1936-05-16 1939-09-19 Rca Corp Electron tube
US2223040A (en) * 1937-06-30 1940-11-26 Gen Electric Electron discharge device
US2249453A (en) * 1938-12-02 1941-07-15 Gen Electric Electron microscope
US2496127A (en) * 1947-02-05 1950-01-31 Rca Corp Electron gun for cathode-ray tubes
US2563500A (en) * 1951-08-07 Plural beam tube
US2661436A (en) * 1951-11-07 1953-12-01 Rca Corp Ion trap gun
US2669672A (en) * 1953-03-10 1954-02-16 Sam H Kaplan Color image target structure
US2726347A (en) * 1953-04-30 1955-12-06 Rca Corp Multiple-beam electron gun
US2726348A (en) * 1953-05-26 1955-12-06 Rca Corp Multiple beam gun
US2729759A (en) * 1953-10-13 1956-01-03 Rca Corp Beam controlling apparatus
US2957106A (en) * 1954-08-12 1960-10-18 Rca Corp Plural beam gun

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB505751A (en) * 1937-09-13 1939-05-15 Frederick Hermes Nicoll Improvements in or relating to cathode ray tubes
GB510699A (en) * 1937-12-04 1939-08-04 Otto Klemperer Improvements in or relating to electron discharge devices such as cathode ray tubes

Patent Citations (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2563500A (en) * 1951-08-07 Plural beam tube
US2165028A (en) * 1933-12-29 1939-07-04 Emi Ltd Television and the like system employing cathode ray tubes
US2173165A (en) * 1936-05-16 1939-09-19 Rca Corp Electron tube
US2223040A (en) * 1937-06-30 1940-11-26 Gen Electric Electron discharge device
US2249453A (en) * 1938-12-02 1941-07-15 Gen Electric Electron microscope
US2496127A (en) * 1947-02-05 1950-01-31 Rca Corp Electron gun for cathode-ray tubes
US2661436A (en) * 1951-11-07 1953-12-01 Rca Corp Ion trap gun
US2669672A (en) * 1953-03-10 1954-02-16 Sam H Kaplan Color image target structure
US2726347A (en) * 1953-04-30 1955-12-06 Rca Corp Multiple-beam electron gun
US2726348A (en) * 1953-05-26 1955-12-06 Rca Corp Multiple beam gun
US2729759A (en) * 1953-10-13 1956-01-03 Rca Corp Beam controlling apparatus
US2957106A (en) * 1954-08-12 1960-10-18 Rca Corp Plural beam gun

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3254251A (en) * 1962-07-06 1966-05-31 Rca Corp Cathode ray tube gun having nested electrode assembly
US3252032A (en) * 1963-12-13 1966-05-17 Sylvania Electric Prod Electrode assembly locating means
US3258625A (en) * 1964-07-27 1966-06-28 Aligned electrode holders for mount- ing parallel array of electron guns
US4590403A (en) * 1984-08-31 1986-05-20 Rca Corporation Color picture tube having an improved inline electron gun
US6559586B1 (en) 2000-02-08 2003-05-06 Sarnoff Corporation Color picture tube including an electron gun in a coated tube neck

Also Published As

Publication number Publication date
GB799533A (en) 1958-08-13
NL94232C (de)
BE543332A (de)
NL202514A (de)
DE1124160B (de) 1962-02-22
FR1139940A (fr) 1957-07-08

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