CA1111966A - Electron gun for a cathode ray tube - Google Patents
Electron gun for a cathode ray tubeInfo
- Publication number
- CA1111966A CA1111966A CA295,638A CA295638A CA1111966A CA 1111966 A CA1111966 A CA 1111966A CA 295638 A CA295638 A CA 295638A CA 1111966 A CA1111966 A CA 1111966A
- Authority
- CA
- Canada
- Prior art keywords
- voltage
- electrodes
- picture tube
- neck portion
- resistor
- 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
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- Vessels, Lead-In Wires, Accessory Apparatuses For Cathode-Ray Tubes (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
An electron gun used in a cathode ray tube, for example, color television picture tube, is disclosed. The electron gun has a plurality of electrodes aligned in one direction along an axis of a neck portion of the cathode ray tube. Each of the electrodes is supplied with a suitable potential for focusing and accelerating an electron beam derived by a cathode. A
resistance element which comprises a ceramic substrate coated with a layer of resistive material is provided along and adjacent to the electrodes in the cathode ray tube. One end of the resistance element is electrically connected to the anode potential, and another end is connected to a stem lead pin which is at a substantially low enough potential to avoid mutual ele-tric discharge between stem lead pins. Suitable potential for the selective electrodes is derived from intermediate taps of the resistor.
An electron gun used in a cathode ray tube, for example, color television picture tube, is disclosed. The electron gun has a plurality of electrodes aligned in one direction along an axis of a neck portion of the cathode ray tube. Each of the electrodes is supplied with a suitable potential for focusing and accelerating an electron beam derived by a cathode. A
resistance element which comprises a ceramic substrate coated with a layer of resistive material is provided along and adjacent to the electrodes in the cathode ray tube. One end of the resistance element is electrically connected to the anode potential, and another end is connected to a stem lead pin which is at a substantially low enough potential to avoid mutual ele-tric discharge between stem lead pins. Suitable potential for the selective electrodes is derived from intermediate taps of the resistor.
Description
1~1196~
BACKGROUND OF THE INVENTION
_ Field o~ the Invention:
The present invention relates to an electron gun unit and especially to an electron gun unit used in a television picture tube.
Prior Art:
In a conventional color television picture tube, a high voltage of 25,- 30 KV is applied to a last accelerating elec-trode of an electron gun unit and a picture screen through an anode button mounted at the funnel portion of a picture tube.
At the same time, a voltage of Or~ 5 KV is applied to a focusing electrode forming a focusing electron lens positioned near the last accelerating electrode, through a terminal pin provided at the end o a neck portion of the picture tube.
In order to make a small beam spot on the picture screen which results in a more precise and clear picture, it is desir-able to reduce the aberration of the focusing lens as much as possible. To reduce the aberration of the focusing lens, it is ; necessary to relax the voltage gradient between the electrodes.
To achieve this, there are such methods as widening the dis-tance between the electrodes, applying close voltage to the electrodes, and a combination of the a~ove.
` In the case of applying a similar voltage to the elec-trodes, it is necessary to apply a high voltage of more than 10 KV to the focusing electrode next to the last accelerating .1 .
electrode. Such high voltage cannot be applied through a terminal pin provided at the end of the neck portion of the picture tube, because there occurs an electric discharge (spark) between the terminal pin and the other terminal pins which supply , .
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voltage to otller electrodes of the electron gun unit, for exa~.ple, heaters. Then, it can be supplied through another button provided at the funnel portion, however, it causes compllca~ed assembly and a substantial cos~-up.
In the case of z picture tube widely known as a "Trinitron" (registered Trademark of Sony Corporation, the assignee of the present invention), three electron beams are focused by a single electron lens, in which each beam passes through the center of a single electron lens of large diameter.
The focused three electron beams are deflected to hit the same position of an apertured grille provided in front of the picture screen by four convergence electrodes provided at the top end of the electron gun unit which makes three passages therebetween for each of the electron beams. Two inner electrodes of the convergence electrode are applied by the same potential as the anode potential. Two outer electrodes of the convergence elec-trodes are applied by a lower voltage than the anode potential by 0.4~ 1.5 Y~V, so that the electron beams which pass through the convergence electrodes are deflected to the side of the center beam.
At one time, the voltages were applied through another button provided at the funnel portion and an electrically shield-ed cable connected to the button and the outer electrodes.
Now, a co-axial anode button, which has two cylindrical electrodes electrically insulated from each other, is used to provide an anode voltage through an outer electrode of the anode button, and convergence voltage through an inner electrode of the anode button and an electrically shielded cable connecting the inner electrode and the convergence electrodes. By the above co-axial anode button, it is not necessary to provide two buttons - . :. - ~ ,...... - . .. .
6~i at the funnel portion of the picture tube, however, still it is troublesome to connect the inner electrode of the anode button and outer convergence electrodes by the electrically shielded cab]e.
Other specific disclosures of possible interest are Japanese Publication 40987/72 and U.S. Patent 3,514,663, issued May 26, 1970 in the names of susumu Yoshida and Akio Ohgoshi, both assigned to the same assignee as the present invention, and u.S. Patent 3,932,876 issued January 13, 1976 in the name of Francis Joseph Campbell.
OBJECTS A~ SUMMARY OF THE II~VE~TION
It is an object of the present invention to provide an improved electron gun unit for use in a cathode ray tube.
It is another object of the present invention to pro-vide an electron gun unit in which desired potential to the electrode is applied by a simple construction.
According to an aspect of the present invention, there is provided an improved electron gun which comprises a plurality of electrodes for focusing and accelerating an electron beam arranged along an axis of a neck portion of the cathode ray tube. There is also provided a resistor formed in a zig-zag ; pattern on a ceramic base located within the neck of the ~icture tube. One end of the resistor is applied with high voltage which is the same as the anode voltage. Desirable voltages for focusing and/or convergence are obtained from intermediate taps of the resistor. While another end of the resistor is connected to the substantially low voltage.
Accordingly, there is provided a television picture tube comprising a glass envelope having neck and funnel portions and a screen portion in said funnel portion to be bombaxded by an electron beam generated in said neck portion, &~i an electron gun unit sealed in said envelope in said neck portion, having a plurality o~ electrodes for focusing and accelerating and deflecting an electron beam generated by a cathode, aligned along an axis of said neck portion, a resistor comprising an insulating substrate and a resistive path formed thereon provided along said plurality of electrodes and sealed in said neck portion, said resistive path having one end and another end, said one end being supplied with the same voltage as the voltage supplied to said screen portion, said another end of said resistor being electrically connected to a terminal pin at one voltage provided at one edge of said neck portion through which said another edge of said resistor being lead to the outside of said envelope, a desirable voltage for the electrodes being derived from an intermediate tap between said two ends of said resistance path by dividing a voltage between both of said ends according to a resistance between said intermediate tap and said one end, and said one voltage of said terminal pin being substantially low enough to avoid an electric discharge between electrodes and said terminal pin.
More particularly there is provided:
A television picture tube comprising: :
a) a glass envelope having neck and funnel portions and a screen portion in saia funnel portion to be bombarded by an electron beam generated in said neck portion, . .
- 4a - .
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b) an electron.gun unit sealed in ~aid envelope in said neck portion, having a plurality.of electrodes for .
focusing and accelerating an electron.beam generate~ by a cat:hode, aligned.along an axis of said neck portion, c) a resistor comprising an insulating substrate and a resisti~e path formed thereon provided along said plurality of electrodes and sealed in said neck portion, said resistive path having one end and another end, said one end being supplied with the same voltage as the voltage supplied to said screen portion, said another end of said resistor being electrically connected to a terminal pin at one voltage provided at one edge of said neck portion through which said another edge of said resistor being lead to the outside of said envelope, a predetermined voltage for said electrodes being derived from an intermediate tap between said two ends of said resistive path by dividing a voltage between both of said ends according to a resistance between said intermediate tap and said one end, and said one voltage of.said terminal pin being substantially low enough to avoid an electric discharge between electrodes and said terminal pin.
There is also provided: a c~lor picture tube having an evacuated bulb which includes a funnel.portion and a neck portion, a picture screen and an apertured grille being formed in the outer end of said funnel portion, an anode in the form of an electrically. conductive coating being formed over the inner surface of said funnel portion and over the inner surface of a portion of the neck portion adjacent the funnel portion, and an electron gun being formed in the neck portion;
j said elcctron gun comprising a plurality of electrodes aligned -4b-~r~
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a~ong the axis of said neek portion, at least three of which are main focusing electrodes, a resistor comprising a substrate of ceramic mater;al on which a resistive path is formed, said ceramic substrate.being mount.ed along said plurality of elec-trodes, said resistive path having a high voltage end, a low voltage end and an intermediate tap between said ends, said high voltage end of said resistive path being connected to said conductive surface on the inner surface of said tube, an intermediate voltage lower than said high voltage for one of said main electrodes being obtained at said intermediate tap, said low voltage end of said resistive path being connected to a terminal provided at one end of said neck portion for con-nection to a relatively low voltage, thereby to avoid an electric discharge at other terminals provided at said high voltage end of said neck portion.
There is further rovided a color nicture tube having an evacuated bulb which includes a funnel portion and a neck portion, a picture screen and an apertured grille being formed in the outer end of said funnel portion, an anode in the form of an electrically conductive coating being formed over the inner surface of said funnel portion and over the inner ...
surface of a portion of the neck portion adjacent the funnel portion, and an electron gun being formed in the neck portion;
said electron gun comprising an electron beam source for pro-ducing an electron beam path along the axis of said tube, a plurality of grid electrodes aligned along the axis of said neck portion, at least three of said electrodes constituting a first, second and third grids which form the main focusing electrodes, being provided for acceleration and focusing of said electron beam, a resistor comprising a substrate formed with a resistive path thereon provided along said plurality of electrodes and -4c-B
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sealed in said neck portion, s~id resistive path having an end, another end, and an intermediate tap provided between said ends, ~aid third ~rid and said one end of said resistive path being applied with a high anode voltage which is the same voltage as applied to said picture screen of said picture tube, said ~econd grid being applied with a voltage lower than said anode voltage, which is obtained at said intermediate tap of said resistive path, said first grid being applied with a voltage higher than said voltage applied to said second grid, said another end of said resistive path being connected to a terminal pin provided at one end of said neck portion at a substantially low voltage to avoid an electric discharge between other terminal pin provided at said one end of said neck portion.
There is further ~rovide~ a color picture tube having an evacuated bulb which includes a funnel portion and a nec~ portion, a picture screen and an aper~ured grille being formed in the outer end of said funnel portion, an anode in the form of an electrically conductive coating being formed ov~r the inner surface of ~aid funnel portion and over the inner surface of a portion of the neck portion adjacent the funnel portion, and an electron gun.being formed in the neck portion;
said electron gun having three electron beams generated in one plane and accelerated and focused by a single electron lens, at least first, second and third electrodes aligned in this order along a beam path of said electron beams, forming said electron lens, two inner and two outer plate ~haped electrodes provided next to said third electrode along said beam path formin~ three slits therebetween to be passed by said three electron beams, for deflecting saîd electr~n beams, a resistor comprising a substrate formed with a resistive path thereon, -4d-:æ
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provided along said electro(les and sealed in ~ neck portion of an envelope of said pictur~ tube, said resi~tive path having one encl, another end, and nn intermcdi.at~ tap b~tween s~id ends, said third grid, said two inner electrodes, and said one end of said resistive path being applied with a high anode voltage the same voltage as applied to a picture screen of said picture tube, said outer electrodes being applied with a lower voltage than said anode voltage which is obtained at said intermediate tap of said resistive path, said another end of said resistive path being connected to a terminal pin provided at one end of said neck portion at a substantially low voltage to avoid an electric discharge between other terminal pins provided at said one end of said neck port ion .
BRI EF DESCRIPTION OF THE DRAWINGS
Figure 1 is a perspective view of an electron gun unit of the present invention;
Figure 2 is a schematic drawing to show the connection between electrodes and a register.
; D -4e-~ 6 Figure 3 is ~1 schem~tic side elevation~l view to show th~ electron gtln Ullit oE th~ pr~serlt illv~nti~n ~ealcd in a neck portion of th~ catho~le lly tu~;
Figure 4 is a ~ S s~ctional vi~ tak~n as IV-IV line of Figure 3;
Figure 5 is ~ scheln~tic Qide elevational view to show the electron gun unit of ~nother example of the present inven-tion sealed in a neck portion of the cathode ray tube;
Figure 6 is a cross sectional view taken as VI-VI line of Figure 5; and Figure 7 is a diagrammatic top view illustrating a color picture tube having an electron gun of the type illustrated in Figure 1, ~ut without showing the resistance element which ~ro-vides one of the i~portant features of the present invention (this being shotm in Figures 1 and 2).
DESCRIP~ION OF THE PREFERRED EMBODIMENTS
The first embodiment of the invention ~Jill be explained with reference to the drawings, in which an electron gun unit with a uni-potential electron lens is applie~ to a "Trinitron"
picture tube.
As seen in Figures 1, 2 and 7, the picture tube in-cludes a neck portion 23 and a funnel portion 30. A picture screen P closes the end of the funnel portion and has an apertured grille in front of the screen. An electron gun 1 (see Figure 1) is mounted in the neck. The gun 1 includes three cathodes KR,KG and KB aligned in a horizontal plane. The thxee cathodes are positioned behind a control grid Gl which in turh are followed by prefocusing grids G2 and G3. Next in line is the main focusing lens which is formed by grid G4. Grids Y' .
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Gri~s G3, G4 and G5 are accelerating grids. Thereaf~er, there is formed the convergence electrodes & and 9 and 11 and 12. In p~ssing to screen P, the electron beam from cathode I~R pass through its associated opening in grid Gl and Grid ~2~ respect-ively, then through G3, G~ and G5 and finally between plate electrodes 9 and 12. The electron beam from cathode KG passes straight through the electron gun 1 and out between convergence plates 8 and 9 before reaching the apertured grille AG. The electron beam from cathode K~ passes through its associated apertures in grid Gl and grid G2, then through G3, G~ and G5, and finally between convergence electrodes 8 and 11 before reach-ing the apertured grille AG
A de1ection yoke DY surrounds the neck at its junction with the funnel portion of the picture tube.
A conductive carbon coating is formed over the inner surface of the funnel of the picture tube, and this coating also extends over the inner surface of the neck of the tube back to the area of the convergence electrodes 8, 9, 11 and 12. A high voltage contact button 31 extends through the wall of the funnel to apply a high voltage Eb to the conductive carbon coating 24 and to the picture screen and to the apertured grille.
Terminal pins 4 are formed at the end of the stem 2.
Figure 1 shows an electron gun unit of the present in-vention which is sealed in the neck portion of the picture tube, and Figure 2 shows a connection diagram between the electrodes of the electron gun unit and a resistor. In Figures 1 and 2, a reference number 1 designates a~ electron gun unit generally.
There are provided a stem 2 made of glass, and an evacuation i pipe 3 integrally formed with the stem 2, terminal pins ~
mounted on the stem 2. The terminal pins are connected to '.
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various electrocles, for example, heaters of the cathode in the picture tube. There are also provided electrodes (grids) Gl, G2, G3 J G~, G5, arranged coaxially, each having a cylindrical shape and supported integrally by a pair of supporters 5, h made of bead glass. Convergence electrodes 3, 9 are attached to a flange portion 10 of the fifth grid G5, and convergence electrodes 11, 12 are supported by the bead glass supporter 5, 6 through a supporting piece 13. A connecting piece 14 is also integrally provided with the fIange portion 10. As explained later, the connecting pieces 14 contacts the carbon layer on the inner wall of a funnel portion 30 of the picture tube, through which a desired high voltage Eb is the same voltage as applied to the picture screen P (i.e., the anode voltage), is supplied to the fifth grid G5. There is provided a resistor 15 along the grids Gl~ G5 supported at one end by a metal supporting piece 16, and at another end by a lead 22.
The resistor 15 is formed with a printed resistive path 17 on one surface of a substrate made of an insulating material, for example, a ceramic substrate. The printed resistive path is covered with a glass layer. The size of the resistor is, for example, 10 mm width, 50 mm length, 1.5 mm thickness. An edge of the resistive path 17 and the fifth grid G5 are electrically connected by the supporting piece 16, and the fifth grid G5 and the third grid G3 are electrically connected by a lead 19.
A predetermined position b which is remote by a predetermined length from one end of the resistive path 17 and the fourth grid G4 are electrically connected by a lead 20, and another position a which is remote by a predetermined length from one end of the resistive path 17 iG electrically connected to the convergence electrodes 11 and 12 by a lead 21. Another end of ~ .
~ $ ~ 1~ 6 ~ , the resistive path 17 is electrically connected to a terminal pin ~ by a lead 22. The convergence electrodes 11 and 12_ a~e electrically connected with each other.
The above constructed electron gun unit is sealed in a neck portion 23 of the picture tube> as sho~ in Figur~s 3 and 4. There is provided a carbon coating layer 24 on the inner wall of the neck portion 23 and funnel portion (which is not sho~m in the drawings) of the picture tube, to which the connecting pieces 14 touch. The carbon coating layer 24 is electrically connected to a button provided on a funnel portion of the picture tube, through which a hi~h voltage ~f, for example, 30 KV is applied from the outside of the picture tube.
By the above construction, the high voltage applied to the carbon coating layer 24 i8 applied to the convergence elec-trodes ~, 9 and the fifth grid G5 through the connecting piece 14, and the same voltage is applied to the third grid G3 through the connecting lead 19 and one end of the resistive path 17 through the supporting piece 16. Thus, the convergence elec-trodes ~, 9 and the grids G3, G5 are applied with the same potential. The high voltage supplied from the anode button is also applied to the picture screen.
The high voltage applied to the end of the resistive path 17 is divided at the intermediate tap a by the voltage drop caused by the resistive path between the high voltage end and the intermediate tap a, and the derived voltage is applied to the convergence electrodes 11, 12 through the lead 21. It is also divided at the tap b to derive a lower voltage than the anode voltage by the voLtage drop between the high voltage end and the tap b, and the derived voltage is applied to the fourth grid G4 through the lead 20, There are provided claws on the .
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leads 21 and 20 ~o be fixed to -the intermedia~e taps. Thus, the potential applied to the convergence electrodes 11 and 12 is a little lower than the potential applied to the convergence electrodes 8 and 9, and the potential of the fourth ~rid G4 is still lower than that. The other end of the resistive path 17 is electrically connected to the terminal pin ~a mounted in the stem 2 through the léad 22. The terminal pin 4a is connected to the ground potential through a variable resistor 25. The variable resistor 25 is provided to do fine control of the poten-tial applied to the convergence electrodes 11 and 12 and the fourth grid G4. The first grid Gl and the second grid G2 are supplied with a predetermined voltage through predetermined terminal pins 4 from outside of the picture tube. A current for a heater o the cathode is also supplied through predeter-mined terminal pins. Thus, each of the electrodes are applied with a desirable voltage which is derived from an intermediate tap of the resistor ~ based on the anode voltage obtained by the connecting piece 14.
The resistive path 17 is manufactured by, for example, printing and baking a mixture of binder, glass powder and resistive material, for example, metal oxide powder, on a sub- -strate of a thin ceramic plate. Following is an example. A
paste of 10 weight parts of ruthenium oxide powder, 60 weights parts of glass powder, and 30 weight pa~ts o binder o ethyl-cellulose is printed zig-zag pattern as shown in Figures 1 and 2, on a ceramic substrate. The printed substrate is then baked and the coating glass is applied on the resistive path.
The resistance of the resistive path 17 is about 500 M ~ or more be~ween the both ends. In the above method to supply desirable voltage by using resistor, there is a tendency to ~ q .
increase the current loss, so it is desirable to suppress the current value less than about 50~ A. It is convenient to electrically connect and support one end of the resistive path which is applied with high voltage by ~he ~e~al supporting piece 16 which is welded to the fifth grid G5. The lead 22 welded to the terminal pin 4a is supporting the substrate 15 and also electrically connecting the low voltage end of the resistive path. So, there are provided claws on the support-ing piece 16 and the lead 22 to fix the same to the substrate.
In the example, the length of the substrate 15 is selected substantially the same as the length of the electron gun. Thus, it is possible to make the length of the resistive path satisfactorily long, and accordingly, satisfactorily large amount of the voltage drop can be achieved along the resistive path. And the voltage at the terminal pin 4a which is the low voltage side can be made very close to the ground potential and not e~ceeding 2 KV. Thus, the voltage control for the convergence electrodes 11 and 12 and the fourth grid G4 can be achieved easily and safely. Of course, it is not necessary to provide the variable resistor 25 when the low voltage side is directly connected to the ground potential or directly con-nected to a terminal of a predetermined potential. In this example> the convergence electrodes ~ and ~, the fifth grid G5 and the third grid G3 are applied with 30 KV, the convergence electrodes 11 and 12 are applied with about 29 KV, and the fourth grid G4 is applied with 12 KV. So the position of the inter-mediate taps are selected to achieve the suitable voltage drop.
The substrate 15 formed with the resistive path 17 thereon is provided along the electron gun and is supported at `s ...................................... _ ]. ~) _ . . . -. ., . : -.
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one end by the fifth grid G5 to which a high voltage of anode vol~age is applied and at another end by the terminal pin 40, and the surface of the resistive path 17 is arranged not to contact with the other electrodes. Each of the voltage divider terminals (high voltage end, and the intermediate taps _ and b) is supplying voltage to the gridsG5 and G3 to the convergence electrodes 11 and 12, and to the grid G4, respec-tively. So, even if the voltage of the terminal 4a is controlled, there are no influences on the electron beam modulating system com-prising a cathode, the first grid Gl, and the second grid G2.
As shown in Figllres 1 and 4, the resistor 17 is provided on the side where no bead glass supporters 5, 6 exist. So, it is not necessary to reduce the diameter of electrodes nor to widen the diameter of the neck portion. In the above example, both o~ the convergence voltage and the focusing voltage are obtained by dividing the anode voltage using the resistor. Of course, it is possible to arrange to obtain only the conver-gence voltage or the focusing voltage. In the case when only the convergence voltage is obtained by dividing the anode voltage, low convergence voltage of O ~ 5 KV can be supplied through the terminal pin 4.
In the conventional picture tube except the "Trinitron"
(TM) picture tube, only the focusing voltage is obtained by dividing the anode voltage. Figures 5 and 6 show another example of the present invention applied to the picture tube which does not have the convergence electrodes 8, 9, 11 and 12 of Figure 1. Figures 5 and 6 show an example of the elec-tron gun applied to a so-called unitized in-line three beams hi-unipotential type electron gun, in which each grid electrode has a slightly flattened shape, and each grid electrode for three electron beams are formed inte~rally in one body. I~
Figure.s 5 and 6, portions corresponding to that appearing in Figures 1 and 2 are designated by the same reference numerals.
The substrate 15 formed with the resistive layer I7 is mounted on one of the supporters 5 and 6 which support the grid electrodes Gl to G6 each has a slightly flattened shape. There is provided a connecting piece 14 on the sixth grid G6, which contacts the inner carbon coating 24 of the neck portion. The sixth grid G6 is electrically connected to the fourth grid G4 through a lead 26 and is connected to one end of the resistive path 17 through another lead 27.
A voltage applied to the resistive path is divided at the in~ermediate tap _ and applied to the fifth grid G5 through a lead 2~. The fifth grid G5 is connected to the third grid G3 through a lead 29. The grids Gl and G2 are connected to predetermined terminal pins 4. Thus, the sixth and fourth grids are applied the same high voltage (for example, 30 KV, the anode voltage), and the fifth and third grids G5 and G3 are applied lower voltage than the above (for example, 12 - KV). Or, the third grid G3 is separated from the fifth grid G5 and, connected to the different position of the resistive path to be applied different voltage from that of the fifth grid ; As shown in ~igure 6, in the second example of the invention, the substrate 15 is mounted on the supporter 5, because the electrodes are flat shaped. Similar supporting method to the first example can be considered in which the substrate is supported by the leads 27 and 22 Further, the substrate 15 can be melt-bonded to the supporter 5. It is expected that directly printing and baking the resistive Dath on the supporter 5 made of bead glass, ~lakes a simplified structure, however, in this case, it is a problem that the resistance value of the resistive path possibly changes upon heat treat~ent to soften the bead glass supporters 5, 6 to put the grids into together by changing of the shape of the supporter. So, practically, the ceramic substrate formed with the resistive path thereon is melt-bonded on the supporter 5 when the bead-glass supporter is softened or, has been bonded on the back side of the supporter 5 previousl~.
Further, the ceramic substrate 15 can be bonded to the bead-glass supporter after the beadin~ operation. In this case, the substrate 15 can be bonded by using low melting temperature glass or flit type ceramics, for example, "Sumi8eramu" (trade designation of Sumitomo Kagaku Corpora-tion, Japan). The suitable materials for the resistive layer other than ruthenium oxide are Ni-SiO type of oxide, Cr-SiO
type of oxide, Ni-Cr type of alloy, Cu-Mn type of alloy, Cr metal, and so on. These can be manufactured as thin films by a sputtering technique.
Generally speaking, i~ is rather difficult to bury the anode button in the funnel portion of the picture tube, and usually glass bulb manufacturer buries it.
In the Trinitron picture tube, the convergence voltage is close to the anode voltage, so it is not so dangerous to supply these voltages by using the co-axial button. But it is dangerous to supply the high focusing voltage, for example, 12 KV, and the anode voltage by the co-axial button, because there are substantial chances of electric discharge. Then two buttons must be provided on the funnel portion. This causes a `~
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substantial new problem, for example, it is necessary to provide two electrlcally separated inner carbon coatings, and complicated connection by the cables from the button.
According to the present invention, it is enough to provide only one anode button without any special struc-ture, such as co-axial button. Further, the cable which connects the anode button and the convergence electrodes is not necessary anymore. So, the assembly is simplified.
As shown in the examples, by making the length of the resis-tor substantially equal to the length of the electron gun, the supporting structure is simplified, assembly is simpli-fied, and it is possible to obtain a sufficiently high resistance to provide enough voltage drop.
The larger size picture tube requires a higher anode voltage, and the size of the electron gun becomes long. In this invention, the resistive path can be made long to make a large voltage drop corresponding to the increase of the anode voltage.
It will be apparent to those skilled in the art that many modifications and variations may be effected with-out departing from the spirit and scope of the novel concepts of the present invention.
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BACKGROUND OF THE INVENTION
_ Field o~ the Invention:
The present invention relates to an electron gun unit and especially to an electron gun unit used in a television picture tube.
Prior Art:
In a conventional color television picture tube, a high voltage of 25,- 30 KV is applied to a last accelerating elec-trode of an electron gun unit and a picture screen through an anode button mounted at the funnel portion of a picture tube.
At the same time, a voltage of Or~ 5 KV is applied to a focusing electrode forming a focusing electron lens positioned near the last accelerating electrode, through a terminal pin provided at the end o a neck portion of the picture tube.
In order to make a small beam spot on the picture screen which results in a more precise and clear picture, it is desir-able to reduce the aberration of the focusing lens as much as possible. To reduce the aberration of the focusing lens, it is ; necessary to relax the voltage gradient between the electrodes.
To achieve this, there are such methods as widening the dis-tance between the electrodes, applying close voltage to the electrodes, and a combination of the a~ove.
` In the case of applying a similar voltage to the elec-trodes, it is necessary to apply a high voltage of more than 10 KV to the focusing electrode next to the last accelerating .1 .
electrode. Such high voltage cannot be applied through a terminal pin provided at the end of the neck portion of the picture tube, because there occurs an electric discharge (spark) between the terminal pin and the other terminal pins which supply , .
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voltage to otller electrodes of the electron gun unit, for exa~.ple, heaters. Then, it can be supplied through another button provided at the funnel portion, however, it causes compllca~ed assembly and a substantial cos~-up.
In the case of z picture tube widely known as a "Trinitron" (registered Trademark of Sony Corporation, the assignee of the present invention), three electron beams are focused by a single electron lens, in which each beam passes through the center of a single electron lens of large diameter.
The focused three electron beams are deflected to hit the same position of an apertured grille provided in front of the picture screen by four convergence electrodes provided at the top end of the electron gun unit which makes three passages therebetween for each of the electron beams. Two inner electrodes of the convergence electrode are applied by the same potential as the anode potential. Two outer electrodes of the convergence elec-trodes are applied by a lower voltage than the anode potential by 0.4~ 1.5 Y~V, so that the electron beams which pass through the convergence electrodes are deflected to the side of the center beam.
At one time, the voltages were applied through another button provided at the funnel portion and an electrically shield-ed cable connected to the button and the outer electrodes.
Now, a co-axial anode button, which has two cylindrical electrodes electrically insulated from each other, is used to provide an anode voltage through an outer electrode of the anode button, and convergence voltage through an inner electrode of the anode button and an electrically shielded cable connecting the inner electrode and the convergence electrodes. By the above co-axial anode button, it is not necessary to provide two buttons - . :. - ~ ,...... - . .. .
6~i at the funnel portion of the picture tube, however, still it is troublesome to connect the inner electrode of the anode button and outer convergence electrodes by the electrically shielded cab]e.
Other specific disclosures of possible interest are Japanese Publication 40987/72 and U.S. Patent 3,514,663, issued May 26, 1970 in the names of susumu Yoshida and Akio Ohgoshi, both assigned to the same assignee as the present invention, and u.S. Patent 3,932,876 issued January 13, 1976 in the name of Francis Joseph Campbell.
OBJECTS A~ SUMMARY OF THE II~VE~TION
It is an object of the present invention to provide an improved electron gun unit for use in a cathode ray tube.
It is another object of the present invention to pro-vide an electron gun unit in which desired potential to the electrode is applied by a simple construction.
According to an aspect of the present invention, there is provided an improved electron gun which comprises a plurality of electrodes for focusing and accelerating an electron beam arranged along an axis of a neck portion of the cathode ray tube. There is also provided a resistor formed in a zig-zag ; pattern on a ceramic base located within the neck of the ~icture tube. One end of the resistor is applied with high voltage which is the same as the anode voltage. Desirable voltages for focusing and/or convergence are obtained from intermediate taps of the resistor. While another end of the resistor is connected to the substantially low voltage.
Accordingly, there is provided a television picture tube comprising a glass envelope having neck and funnel portions and a screen portion in said funnel portion to be bombaxded by an electron beam generated in said neck portion, &~i an electron gun unit sealed in said envelope in said neck portion, having a plurality o~ electrodes for focusing and accelerating and deflecting an electron beam generated by a cathode, aligned along an axis of said neck portion, a resistor comprising an insulating substrate and a resistive path formed thereon provided along said plurality of electrodes and sealed in said neck portion, said resistive path having one end and another end, said one end being supplied with the same voltage as the voltage supplied to said screen portion, said another end of said resistor being electrically connected to a terminal pin at one voltage provided at one edge of said neck portion through which said another edge of said resistor being lead to the outside of said envelope, a desirable voltage for the electrodes being derived from an intermediate tap between said two ends of said resistance path by dividing a voltage between both of said ends according to a resistance between said intermediate tap and said one end, and said one voltage of said terminal pin being substantially low enough to avoid an electric discharge between electrodes and said terminal pin.
More particularly there is provided:
A television picture tube comprising: :
a) a glass envelope having neck and funnel portions and a screen portion in saia funnel portion to be bombarded by an electron beam generated in said neck portion, . .
- 4a - .
B
b) an electron.gun unit sealed in ~aid envelope in said neck portion, having a plurality.of electrodes for .
focusing and accelerating an electron.beam generate~ by a cat:hode, aligned.along an axis of said neck portion, c) a resistor comprising an insulating substrate and a resisti~e path formed thereon provided along said plurality of electrodes and sealed in said neck portion, said resistive path having one end and another end, said one end being supplied with the same voltage as the voltage supplied to said screen portion, said another end of said resistor being electrically connected to a terminal pin at one voltage provided at one edge of said neck portion through which said another edge of said resistor being lead to the outside of said envelope, a predetermined voltage for said electrodes being derived from an intermediate tap between said two ends of said resistive path by dividing a voltage between both of said ends according to a resistance between said intermediate tap and said one end, and said one voltage of.said terminal pin being substantially low enough to avoid an electric discharge between electrodes and said terminal pin.
There is also provided: a c~lor picture tube having an evacuated bulb which includes a funnel.portion and a neck portion, a picture screen and an apertured grille being formed in the outer end of said funnel portion, an anode in the form of an electrically. conductive coating being formed over the inner surface of said funnel portion and over the inner surface of a portion of the neck portion adjacent the funnel portion, and an electron gun being formed in the neck portion;
j said elcctron gun comprising a plurality of electrodes aligned -4b-~r~
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a~ong the axis of said neek portion, at least three of which are main focusing electrodes, a resistor comprising a substrate of ceramic mater;al on which a resistive path is formed, said ceramic substrate.being mount.ed along said plurality of elec-trodes, said resistive path having a high voltage end, a low voltage end and an intermediate tap between said ends, said high voltage end of said resistive path being connected to said conductive surface on the inner surface of said tube, an intermediate voltage lower than said high voltage for one of said main electrodes being obtained at said intermediate tap, said low voltage end of said resistive path being connected to a terminal provided at one end of said neck portion for con-nection to a relatively low voltage, thereby to avoid an electric discharge at other terminals provided at said high voltage end of said neck portion.
There is further rovided a color nicture tube having an evacuated bulb which includes a funnel portion and a neck portion, a picture screen and an apertured grille being formed in the outer end of said funnel portion, an anode in the form of an electrically conductive coating being formed over the inner surface of said funnel portion and over the inner ...
surface of a portion of the neck portion adjacent the funnel portion, and an electron gun being formed in the neck portion;
said electron gun comprising an electron beam source for pro-ducing an electron beam path along the axis of said tube, a plurality of grid electrodes aligned along the axis of said neck portion, at least three of said electrodes constituting a first, second and third grids which form the main focusing electrodes, being provided for acceleration and focusing of said electron beam, a resistor comprising a substrate formed with a resistive path thereon provided along said plurality of electrodes and -4c-B
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sealed in said neck portion, s~id resistive path having an end, another end, and an intermediate tap provided between said ends, ~aid third ~rid and said one end of said resistive path being applied with a high anode voltage which is the same voltage as applied to said picture screen of said picture tube, said ~econd grid being applied with a voltage lower than said anode voltage, which is obtained at said intermediate tap of said resistive path, said first grid being applied with a voltage higher than said voltage applied to said second grid, said another end of said resistive path being connected to a terminal pin provided at one end of said neck portion at a substantially low voltage to avoid an electric discharge between other terminal pin provided at said one end of said neck portion.
There is further ~rovide~ a color picture tube having an evacuated bulb which includes a funnel portion and a nec~ portion, a picture screen and an aper~ured grille being formed in the outer end of said funnel portion, an anode in the form of an electrically conductive coating being formed ov~r the inner surface of ~aid funnel portion and over the inner surface of a portion of the neck portion adjacent the funnel portion, and an electron gun.being formed in the neck portion;
said electron gun having three electron beams generated in one plane and accelerated and focused by a single electron lens, at least first, second and third electrodes aligned in this order along a beam path of said electron beams, forming said electron lens, two inner and two outer plate ~haped electrodes provided next to said third electrode along said beam path formin~ three slits therebetween to be passed by said three electron beams, for deflecting saîd electr~n beams, a resistor comprising a substrate formed with a resistive path thereon, -4d-:æ
. . . ... .
provided along said electro(les and sealed in ~ neck portion of an envelope of said pictur~ tube, said resi~tive path having one encl, another end, and nn intermcdi.at~ tap b~tween s~id ends, said third grid, said two inner electrodes, and said one end of said resistive path being applied with a high anode voltage the same voltage as applied to a picture screen of said picture tube, said outer electrodes being applied with a lower voltage than said anode voltage which is obtained at said intermediate tap of said resistive path, said another end of said resistive path being connected to a terminal pin provided at one end of said neck portion at a substantially low voltage to avoid an electric discharge between other terminal pins provided at said one end of said neck port ion .
BRI EF DESCRIPTION OF THE DRAWINGS
Figure 1 is a perspective view of an electron gun unit of the present invention;
Figure 2 is a schematic drawing to show the connection between electrodes and a register.
; D -4e-~ 6 Figure 3 is ~1 schem~tic side elevation~l view to show th~ electron gtln Ullit oE th~ pr~serlt illv~nti~n ~ealcd in a neck portion of th~ catho~le lly tu~;
Figure 4 is a ~ S s~ctional vi~ tak~n as IV-IV line of Figure 3;
Figure 5 is ~ scheln~tic Qide elevational view to show the electron gun unit of ~nother example of the present inven-tion sealed in a neck portion of the cathode ray tube;
Figure 6 is a cross sectional view taken as VI-VI line of Figure 5; and Figure 7 is a diagrammatic top view illustrating a color picture tube having an electron gun of the type illustrated in Figure 1, ~ut without showing the resistance element which ~ro-vides one of the i~portant features of the present invention (this being shotm in Figures 1 and 2).
DESCRIP~ION OF THE PREFERRED EMBODIMENTS
The first embodiment of the invention ~Jill be explained with reference to the drawings, in which an electron gun unit with a uni-potential electron lens is applie~ to a "Trinitron"
picture tube.
As seen in Figures 1, 2 and 7, the picture tube in-cludes a neck portion 23 and a funnel portion 30. A picture screen P closes the end of the funnel portion and has an apertured grille in front of the screen. An electron gun 1 (see Figure 1) is mounted in the neck. The gun 1 includes three cathodes KR,KG and KB aligned in a horizontal plane. The thxee cathodes are positioned behind a control grid Gl which in turh are followed by prefocusing grids G2 and G3. Next in line is the main focusing lens which is formed by grid G4. Grids Y' .
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Gri~s G3, G4 and G5 are accelerating grids. Thereaf~er, there is formed the convergence electrodes & and 9 and 11 and 12. In p~ssing to screen P, the electron beam from cathode I~R pass through its associated opening in grid Gl and Grid ~2~ respect-ively, then through G3, G~ and G5 and finally between plate electrodes 9 and 12. The electron beam from cathode KG passes straight through the electron gun 1 and out between convergence plates 8 and 9 before reaching the apertured grille AG. The electron beam from cathode K~ passes through its associated apertures in grid Gl and grid G2, then through G3, G~ and G5, and finally between convergence electrodes 8 and 11 before reach-ing the apertured grille AG
A de1ection yoke DY surrounds the neck at its junction with the funnel portion of the picture tube.
A conductive carbon coating is formed over the inner surface of the funnel of the picture tube, and this coating also extends over the inner surface of the neck of the tube back to the area of the convergence electrodes 8, 9, 11 and 12. A high voltage contact button 31 extends through the wall of the funnel to apply a high voltage Eb to the conductive carbon coating 24 and to the picture screen and to the apertured grille.
Terminal pins 4 are formed at the end of the stem 2.
Figure 1 shows an electron gun unit of the present in-vention which is sealed in the neck portion of the picture tube, and Figure 2 shows a connection diagram between the electrodes of the electron gun unit and a resistor. In Figures 1 and 2, a reference number 1 designates a~ electron gun unit generally.
There are provided a stem 2 made of glass, and an evacuation i pipe 3 integrally formed with the stem 2, terminal pins ~
mounted on the stem 2. The terminal pins are connected to '.
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various electrocles, for example, heaters of the cathode in the picture tube. There are also provided electrodes (grids) Gl, G2, G3 J G~, G5, arranged coaxially, each having a cylindrical shape and supported integrally by a pair of supporters 5, h made of bead glass. Convergence electrodes 3, 9 are attached to a flange portion 10 of the fifth grid G5, and convergence electrodes 11, 12 are supported by the bead glass supporter 5, 6 through a supporting piece 13. A connecting piece 14 is also integrally provided with the fIange portion 10. As explained later, the connecting pieces 14 contacts the carbon layer on the inner wall of a funnel portion 30 of the picture tube, through which a desired high voltage Eb is the same voltage as applied to the picture screen P (i.e., the anode voltage), is supplied to the fifth grid G5. There is provided a resistor 15 along the grids Gl~ G5 supported at one end by a metal supporting piece 16, and at another end by a lead 22.
The resistor 15 is formed with a printed resistive path 17 on one surface of a substrate made of an insulating material, for example, a ceramic substrate. The printed resistive path is covered with a glass layer. The size of the resistor is, for example, 10 mm width, 50 mm length, 1.5 mm thickness. An edge of the resistive path 17 and the fifth grid G5 are electrically connected by the supporting piece 16, and the fifth grid G5 and the third grid G3 are electrically connected by a lead 19.
A predetermined position b which is remote by a predetermined length from one end of the resistive path 17 and the fourth grid G4 are electrically connected by a lead 20, and another position a which is remote by a predetermined length from one end of the resistive path 17 iG electrically connected to the convergence electrodes 11 and 12 by a lead 21. Another end of ~ .
~ $ ~ 1~ 6 ~ , the resistive path 17 is electrically connected to a terminal pin ~ by a lead 22. The convergence electrodes 11 and 12_ a~e electrically connected with each other.
The above constructed electron gun unit is sealed in a neck portion 23 of the picture tube> as sho~ in Figur~s 3 and 4. There is provided a carbon coating layer 24 on the inner wall of the neck portion 23 and funnel portion (which is not sho~m in the drawings) of the picture tube, to which the connecting pieces 14 touch. The carbon coating layer 24 is electrically connected to a button provided on a funnel portion of the picture tube, through which a hi~h voltage ~f, for example, 30 KV is applied from the outside of the picture tube.
By the above construction, the high voltage applied to the carbon coating layer 24 i8 applied to the convergence elec-trodes ~, 9 and the fifth grid G5 through the connecting piece 14, and the same voltage is applied to the third grid G3 through the connecting lead 19 and one end of the resistive path 17 through the supporting piece 16. Thus, the convergence elec-trodes ~, 9 and the grids G3, G5 are applied with the same potential. The high voltage supplied from the anode button is also applied to the picture screen.
The high voltage applied to the end of the resistive path 17 is divided at the intermediate tap a by the voltage drop caused by the resistive path between the high voltage end and the intermediate tap a, and the derived voltage is applied to the convergence electrodes 11, 12 through the lead 21. It is also divided at the tap b to derive a lower voltage than the anode voltage by the voLtage drop between the high voltage end and the tap b, and the derived voltage is applied to the fourth grid G4 through the lead 20, There are provided claws on the .
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leads 21 and 20 ~o be fixed to -the intermedia~e taps. Thus, the potential applied to the convergence electrodes 11 and 12 is a little lower than the potential applied to the convergence electrodes 8 and 9, and the potential of the fourth ~rid G4 is still lower than that. The other end of the resistive path 17 is electrically connected to the terminal pin ~a mounted in the stem 2 through the léad 22. The terminal pin 4a is connected to the ground potential through a variable resistor 25. The variable resistor 25 is provided to do fine control of the poten-tial applied to the convergence electrodes 11 and 12 and the fourth grid G4. The first grid Gl and the second grid G2 are supplied with a predetermined voltage through predetermined terminal pins 4 from outside of the picture tube. A current for a heater o the cathode is also supplied through predeter-mined terminal pins. Thus, each of the electrodes are applied with a desirable voltage which is derived from an intermediate tap of the resistor ~ based on the anode voltage obtained by the connecting piece 14.
The resistive path 17 is manufactured by, for example, printing and baking a mixture of binder, glass powder and resistive material, for example, metal oxide powder, on a sub- -strate of a thin ceramic plate. Following is an example. A
paste of 10 weight parts of ruthenium oxide powder, 60 weights parts of glass powder, and 30 weight pa~ts o binder o ethyl-cellulose is printed zig-zag pattern as shown in Figures 1 and 2, on a ceramic substrate. The printed substrate is then baked and the coating glass is applied on the resistive path.
The resistance of the resistive path 17 is about 500 M ~ or more be~ween the both ends. In the above method to supply desirable voltage by using resistor, there is a tendency to ~ q .
increase the current loss, so it is desirable to suppress the current value less than about 50~ A. It is convenient to electrically connect and support one end of the resistive path which is applied with high voltage by ~he ~e~al supporting piece 16 which is welded to the fifth grid G5. The lead 22 welded to the terminal pin 4a is supporting the substrate 15 and also electrically connecting the low voltage end of the resistive path. So, there are provided claws on the support-ing piece 16 and the lead 22 to fix the same to the substrate.
In the example, the length of the substrate 15 is selected substantially the same as the length of the electron gun. Thus, it is possible to make the length of the resistive path satisfactorily long, and accordingly, satisfactorily large amount of the voltage drop can be achieved along the resistive path. And the voltage at the terminal pin 4a which is the low voltage side can be made very close to the ground potential and not e~ceeding 2 KV. Thus, the voltage control for the convergence electrodes 11 and 12 and the fourth grid G4 can be achieved easily and safely. Of course, it is not necessary to provide the variable resistor 25 when the low voltage side is directly connected to the ground potential or directly con-nected to a terminal of a predetermined potential. In this example> the convergence electrodes ~ and ~, the fifth grid G5 and the third grid G3 are applied with 30 KV, the convergence electrodes 11 and 12 are applied with about 29 KV, and the fourth grid G4 is applied with 12 KV. So the position of the inter-mediate taps are selected to achieve the suitable voltage drop.
The substrate 15 formed with the resistive path 17 thereon is provided along the electron gun and is supported at `s ...................................... _ ]. ~) _ . . . -. ., . : -.
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one end by the fifth grid G5 to which a high voltage of anode vol~age is applied and at another end by the terminal pin 40, and the surface of the resistive path 17 is arranged not to contact with the other electrodes. Each of the voltage divider terminals (high voltage end, and the intermediate taps _ and b) is supplying voltage to the gridsG5 and G3 to the convergence electrodes 11 and 12, and to the grid G4, respec-tively. So, even if the voltage of the terminal 4a is controlled, there are no influences on the electron beam modulating system com-prising a cathode, the first grid Gl, and the second grid G2.
As shown in Figllres 1 and 4, the resistor 17 is provided on the side where no bead glass supporters 5, 6 exist. So, it is not necessary to reduce the diameter of electrodes nor to widen the diameter of the neck portion. In the above example, both o~ the convergence voltage and the focusing voltage are obtained by dividing the anode voltage using the resistor. Of course, it is possible to arrange to obtain only the conver-gence voltage or the focusing voltage. In the case when only the convergence voltage is obtained by dividing the anode voltage, low convergence voltage of O ~ 5 KV can be supplied through the terminal pin 4.
In the conventional picture tube except the "Trinitron"
(TM) picture tube, only the focusing voltage is obtained by dividing the anode voltage. Figures 5 and 6 show another example of the present invention applied to the picture tube which does not have the convergence electrodes 8, 9, 11 and 12 of Figure 1. Figures 5 and 6 show an example of the elec-tron gun applied to a so-called unitized in-line three beams hi-unipotential type electron gun, in which each grid electrode has a slightly flattened shape, and each grid electrode for three electron beams are formed inte~rally in one body. I~
Figure.s 5 and 6, portions corresponding to that appearing in Figures 1 and 2 are designated by the same reference numerals.
The substrate 15 formed with the resistive layer I7 is mounted on one of the supporters 5 and 6 which support the grid electrodes Gl to G6 each has a slightly flattened shape. There is provided a connecting piece 14 on the sixth grid G6, which contacts the inner carbon coating 24 of the neck portion. The sixth grid G6 is electrically connected to the fourth grid G4 through a lead 26 and is connected to one end of the resistive path 17 through another lead 27.
A voltage applied to the resistive path is divided at the in~ermediate tap _ and applied to the fifth grid G5 through a lead 2~. The fifth grid G5 is connected to the third grid G3 through a lead 29. The grids Gl and G2 are connected to predetermined terminal pins 4. Thus, the sixth and fourth grids are applied the same high voltage (for example, 30 KV, the anode voltage), and the fifth and third grids G5 and G3 are applied lower voltage than the above (for example, 12 - KV). Or, the third grid G3 is separated from the fifth grid G5 and, connected to the different position of the resistive path to be applied different voltage from that of the fifth grid ; As shown in ~igure 6, in the second example of the invention, the substrate 15 is mounted on the supporter 5, because the electrodes are flat shaped. Similar supporting method to the first example can be considered in which the substrate is supported by the leads 27 and 22 Further, the substrate 15 can be melt-bonded to the supporter 5. It is expected that directly printing and baking the resistive Dath on the supporter 5 made of bead glass, ~lakes a simplified structure, however, in this case, it is a problem that the resistance value of the resistive path possibly changes upon heat treat~ent to soften the bead glass supporters 5, 6 to put the grids into together by changing of the shape of the supporter. So, practically, the ceramic substrate formed with the resistive path thereon is melt-bonded on the supporter 5 when the bead-glass supporter is softened or, has been bonded on the back side of the supporter 5 previousl~.
Further, the ceramic substrate 15 can be bonded to the bead-glass supporter after the beadin~ operation. In this case, the substrate 15 can be bonded by using low melting temperature glass or flit type ceramics, for example, "Sumi8eramu" (trade designation of Sumitomo Kagaku Corpora-tion, Japan). The suitable materials for the resistive layer other than ruthenium oxide are Ni-SiO type of oxide, Cr-SiO
type of oxide, Ni-Cr type of alloy, Cu-Mn type of alloy, Cr metal, and so on. These can be manufactured as thin films by a sputtering technique.
Generally speaking, i~ is rather difficult to bury the anode button in the funnel portion of the picture tube, and usually glass bulb manufacturer buries it.
In the Trinitron picture tube, the convergence voltage is close to the anode voltage, so it is not so dangerous to supply these voltages by using the co-axial button. But it is dangerous to supply the high focusing voltage, for example, 12 KV, and the anode voltage by the co-axial button, because there are substantial chances of electric discharge. Then two buttons must be provided on the funnel portion. This causes a `~
_ 1 ~
substantial new problem, for example, it is necessary to provide two electrlcally separated inner carbon coatings, and complicated connection by the cables from the button.
According to the present invention, it is enough to provide only one anode button without any special struc-ture, such as co-axial button. Further, the cable which connects the anode button and the convergence electrodes is not necessary anymore. So, the assembly is simplified.
As shown in the examples, by making the length of the resis-tor substantially equal to the length of the electron gun, the supporting structure is simplified, assembly is simpli-fied, and it is possible to obtain a sufficiently high resistance to provide enough voltage drop.
The larger size picture tube requires a higher anode voltage, and the size of the electron gun becomes long. In this invention, the resistive path can be made long to make a large voltage drop corresponding to the increase of the anode voltage.
It will be apparent to those skilled in the art that many modifications and variations may be effected with-out departing from the spirit and scope of the novel concepts of the present invention.
:
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Claims (27)
1. A color picture tube having an evacuated bulb which includes a funnel portion and a neck portion, a picture screen and an apertured grille being formed in the outer end of said funnel portion, an anode in the form of an electrically conductive coating being formed over the inner surface of said funnel portion and over the inner surface of a portion of the neck portion adjacent the funnel portion, and an electron gun being formed in the neck portion;
said electron gun comprising a plurality of electrodes aligned along the axis of said neck portion, at least three of which are main focusing electrodes, a resistor comprising a substrate of ceramic material on which a resistive path is formed, said ceramic substrate being mounted along said plurality of elec-trodes, said resistive path having a high voltage end, a low voltage end and an intermediate tap between said ends, said high voltage end of said resistive path being connected to said conductive surface on the inner surface of said tube, an intermediate voltage lower than said high voltage for one of said main electrodes being obtained at said intermediate tap, said low voltage end of said resistive path being connected to a terminal provided at one end of said neck portion for con-nection to a relatively low voltage, thereby to avoid an electric discharge at other terminals provided at said high voltage end of said neck portion.
said electron gun comprising a plurality of electrodes aligned along the axis of said neck portion, at least three of which are main focusing electrodes, a resistor comprising a substrate of ceramic material on which a resistive path is formed, said ceramic substrate being mounted along said plurality of elec-trodes, said resistive path having a high voltage end, a low voltage end and an intermediate tap between said ends, said high voltage end of said resistive path being connected to said conductive surface on the inner surface of said tube, an intermediate voltage lower than said high voltage for one of said main electrodes being obtained at said intermediate tap, said low voltage end of said resistive path being connected to a terminal provided at one end of said neck portion for con-nection to a relatively low voltage, thereby to avoid an electric discharge at other terminals provided at said high voltage end of said neck portion.
2. A color picture tube having an evacuated bulb which includes a funnel portion and a neck portion, a picture screen and an apertured grille being formed in the outer end of said funnel portion, an anode in the form of an electrically conductive coating being formed over the inner surface of said funnel portion and over the inner surface of a portion of the neck portion adjacent the funnel portion, and an electron gun being formed in the neck portion;
said electron gun comprising an electron beam source for pro-ducing an electron beam path along the axis of said tube, a plurality of grid electrodes aligned along the axis of said neck portion, at least three of said electrodes constituting a first, second and third grids which form the main focusing electrodes, being provided for acceleration and focusing of said electron beam, a resistor comprising a substrate formed with a resistive path thereon provided along said plurality of electrodes and sealed in said neck portion, said resistive path having an end, another end, and an intermediate tap provided between said ends, said third grid and said one end of said resistive path being applied with a high anode voltage which is the same voltage as applied to said picture screen of said picture tube, said second grid being applied with a voltage lower than said anode voltage, which is obtained at said intermediate tap of said resistive path, said first grid being applied with a voltage higher than said voltage applied to said second grid, said another end of said resistive path being connected to a terminal pin provided at one end of said neck portion at a substantially low voltage to avoid an electric discharge between other terminal pin provided at said one end of said neck portion.
said electron gun comprising an electron beam source for pro-ducing an electron beam path along the axis of said tube, a plurality of grid electrodes aligned along the axis of said neck portion, at least three of said electrodes constituting a first, second and third grids which form the main focusing electrodes, being provided for acceleration and focusing of said electron beam, a resistor comprising a substrate formed with a resistive path thereon provided along said plurality of electrodes and sealed in said neck portion, said resistive path having an end, another end, and an intermediate tap provided between said ends, said third grid and said one end of said resistive path being applied with a high anode voltage which is the same voltage as applied to said picture screen of said picture tube, said second grid being applied with a voltage lower than said anode voltage, which is obtained at said intermediate tap of said resistive path, said first grid being applied with a voltage higher than said voltage applied to said second grid, said another end of said resistive path being connected to a terminal pin provided at one end of said neck portion at a substantially low voltage to avoid an electric discharge between other terminal pin provided at said one end of said neck portion.
3. A color picture tube according to claim 2, in which said plurality of electrodes are supported integrally by supporting glass from both sides of said electrodes along said axis of said neck portion.
4. A color picture tube according to claim 3, in which said resistor in said electron gun is positioned at the side where there is no supporting glass.
5. A color picture tube according to claim 2, in which said another end of said resistive path of said electron gun is electrically connected and supported by said terminal pin and said one end of said resistive path is electrically connected and supported by said third grid.
6. A color picture tube having an evacuated bulb which includes a funnel portion and a neck portion, a picture screen and an apertured grille being formed in the outer end of said funnel portion, an anode in the form of an electrically conductive coating being formed over the inner surface of said funnel portion and over the inner surface of a portion of the neck portion adjacent the funnel portion, and an electron gun being formed in the neck portion;
said electron gun having three electron beams generated in one plane and accelerated and focused by a single electron lens, at least first, second and third electrodes aligned in this order along a beam path of said electron beams, forming said electron lens, two inner and two outer plate shaped electrodes provided next to said third electrode along said beam path forming three slits therebetween to be passed by said three electron beams, for deflecting said electron beams, a resistor comprising a substrate formed with a resistive path thereon, provided along said electrodes and sealed in a neck portion of an envelope of said picture tube, said resistive path having one end, another end, and an intermediate tap between said ends, said third grid, said two inner electrodes, and said one end of said resistive path being applied with a high anode voltage the same voltage as applied to a picture screen of said picture tube, said outer electrodes being applied with a lower voltage than said anode voltage which is obtained at said intermediate tap of said resistive path, said another end of said resistive path being connected to a terminal pin provided at one end of said neck portion at a substantially low voltage to avoid an electric discharge between other terminal pins provided at said one end of said neck portion.
said electron gun having three electron beams generated in one plane and accelerated and focused by a single electron lens, at least first, second and third electrodes aligned in this order along a beam path of said electron beams, forming said electron lens, two inner and two outer plate shaped electrodes provided next to said third electrode along said beam path forming three slits therebetween to be passed by said three electron beams, for deflecting said electron beams, a resistor comprising a substrate formed with a resistive path thereon, provided along said electrodes and sealed in a neck portion of an envelope of said picture tube, said resistive path having one end, another end, and an intermediate tap between said ends, said third grid, said two inner electrodes, and said one end of said resistive path being applied with a high anode voltage the same voltage as applied to a picture screen of said picture tube, said outer electrodes being applied with a lower voltage than said anode voltage which is obtained at said intermediate tap of said resistive path, said another end of said resistive path being connected to a terminal pin provided at one end of said neck portion at a substantially low voltage to avoid an electric discharge between other terminal pins provided at said one end of said neck portion.
7. A color picture tube according to claim 6, in which said electrodes of said electron gun are supported integrally by supporting glass from both sides of them along said axis of said neck portion.
8. A color picture tube according to claim 6, in which said resistor of said electron gun is provided parallel to said one plane and remote from said one plane.
9. A color picture tube according to claim 6, in which said first and third electrodes of said electron gun are applied with the same voltage as said anode voltage and said second electrode is applied a lower voltage than said anode voltage.
10. A color picture tube according to claim 9, in which said voltage applied to said second electrode of said electron gun is obtained at an inter-mediate tap provided between said ends.
11. A color picture tube according to claim 6, in which said resistor of said electron gun is supported by said third electrode and said terminal pin.
12. A color picture tube according to claim 6, in which said terminal pin and said third electrode of said electron gun are provided with claws to fix said resistor.
13. A color picture tube according to claim 2, in which said resistor of said electron gun comprises a ceramic substrate coated with a resistive material on one surface thereof to make a large voltage drop between said ends.
14. A color picture tube according to claim 6, in which said resistor of said electron gun comprises a ceramic substrate coated with a resistive material on one surface thereof to make a large voltage drop between said ends.
15. A television picture tube comprising:
a) a glass envelope having neck and funnel portions and a screen portion in said funnel portion to be bombarded by an electron beam generated in said neck portion, b) an electron gun unit sealed in said envelope in said neck portion, having a plurality of electrodes for focusing and accelerating an electron beam generated by a cathode, aligned along an axis of said neck portion, c) a resistor comprising an insulating substrate and a resistive path formed thereon provided along said plurality of electrodes and sealed in said neck portion, said resistive path having one end and another end, said one end being supplied with the same voltage as the voltage supplied to said screen portion, said another end of said resistor being electrically connected to a terminal pin at one voltage provided at one edge of said neck portion through which said another edge of said resistor being lead to the outside of said envelope, a predetermined voltage for said electrodes being derived from an intermediate tap between said two ends of said resistive path by dividing a voltage between both of said ends according to a resistance between said intermediate tap and said one end, and said one voltage of said terminal pin being substantially low enough to avoid an electric discharge between electrodes and said terminal pin.
a) a glass envelope having neck and funnel portions and a screen portion in said funnel portion to be bombarded by an electron beam generated in said neck portion, b) an electron gun unit sealed in said envelope in said neck portion, having a plurality of electrodes for focusing and accelerating an electron beam generated by a cathode, aligned along an axis of said neck portion, c) a resistor comprising an insulating substrate and a resistive path formed thereon provided along said plurality of electrodes and sealed in said neck portion, said resistive path having one end and another end, said one end being supplied with the same voltage as the voltage supplied to said screen portion, said another end of said resistor being electrically connected to a terminal pin at one voltage provided at one edge of said neck portion through which said another edge of said resistor being lead to the outside of said envelope, a predetermined voltage for said electrodes being derived from an intermediate tap between said two ends of said resistive path by dividing a voltage between both of said ends according to a resistance between said intermediate tap and said one end, and said one voltage of said terminal pin being substantially low enough to avoid an electric discharge between electrodes and said terminal pin.
16. A television picture tube according to claim 15, in which said one end of said resistive path is electrically connected to and supported by a last accelerating electrode supplied with the same voltage as that of the picture screen.
17. A television picture tube according to claim 16, in which said another end of said resistive path is electrically connected to and supported by a terminal pin.
18. A television picture tube according to claim 17, in which said last accelerating electrode and said terminal pin have a metal claw to be fixed to said substrate of said resistor.
19. A television picture tube according to claim 16, in which three electron beams pass the center of the focusing electrodes and deflected by one pair of inner and one pair of outer electrode of plate shaped electrodes, to hit the same position of a mask provided in front of said picture screen, said inner pair being supplied with the anode voltage, said outer pair being supplied with a lower voltage than said anode voltage derived from said inter-mediate tap.
20. A television picture tube according to claim 16, in which said plurality of elec-trodes are supported integrally by supporting glass rods from both sides of them along the axis of the neck portion.
21. A television picture tube according to claim 20, in which said resistor is posi-tioned at the side where there are no supporting glass rods.
22. A television picture tube according to claim 16, in which said resistor has a re-sistance between said two ends enough to obtain a larger vol-tage drop.
23. A television picture tube according to claim 16, in which three beams are in one imaginary plane and said resistor is provided substantially parallel to the plane and remote from the plane.
24. A television picture tube according to claim 15, wherein said insulating substrate of said resistor is a ceramic substrate, and said resistive path is formed by coating said ceramic substrate with a resistive material on one surface thereof to make a large voltage drop between said ends.
25. A television picture tube according to claim 24, wherein said resistive material comprises ruthenium oxide.
26. A television picture tube according to claim 24, wherein said resistive path is covered with glass.
27. A television picture tube according to claim 15, wherein a variable resistor is connected between said terminal pin and ground potential.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA295,638A CA1111966A (en) | 1978-01-25 | 1978-01-25 | Electron gun for a cathode ray tube |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA295,638A CA1111966A (en) | 1978-01-25 | 1978-01-25 | Electron gun for a cathode ray tube |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1111966A true CA1111966A (en) | 1981-11-03 |
Family
ID=4110623
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA295,638A Expired CA1111966A (en) | 1978-01-25 | 1978-01-25 | Electron gun for a cathode ray tube |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1111966A (en) |
-
1978
- 1978-01-25 CA CA295,638A patent/CA1111966A/en not_active Expired
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