GB2201833A - Cathode ray tubes - Google Patents

Description

1 1 1 1 1 CATHODE RAY TUBES This invention relates to cathode ray tubes.

The electron gun of a cathode ray tube of the TR1NITRON (Sony Registered Trade Mark) type is a so-called one-gun three-beam single electron gun, in which three electron beams which are respectively emitted from its three cathode diverge after the beams cross at a point in the centre of the principal lens, and the three electron beams are then converged again on the screen by the action of convergence means. The convergence means is formed of four convergence plates which consist of a pair of inner convergence plates and a pair of outer convergence plates. The inner convergence plates are supplied with an anode voltage HV from a voltage supply means disposed on the tube wall at the funnel portion of the cathode ray tube, and the pair of outer convergence plates are supplied with an equal convergence voltage CV which is lower than the anode voltage. Adjustment of the convergence is performed by changing the DC voltage CV which is supplied to the outer convergence plates, so that deflection of the red (R) and blue (B) beams which are located on respective sides or the central green (G) beam may be changed.

The convergence is thus adjusted by changing the voltage CV which is supplied to the convergence plates. However, even if the convergence is adjusted so that the G and R beams converge at the centre of the screen, sometimes the B beam will not converge at the centre of the screen, and so-called horizontal misconvergence is produced, as shown in Figure 4 of the accompanying drawings, due, for example to errors in the assembly of the electron gun. Such horizontal misconvergence has been corrected by means such as six-pole magnets 61a to 61f as shown in Figure 5 of the accompanying drawings.

Although convergence has already been achieved, there has still been a problem that the form of the beam spots 62R, 62G and 62B are distorted as shown in Figure 6 of the accompanying drawings, due to the influence of the magnetic field. This problem becomes more severe as the resolution of the cathode ray tube is enhanced.

Convergence is also achieved at peripheral portions of the screen by the action of the deflection yoke, but in practice asymmetric misconvergence sometimes occurs in which the B beam deviates in the 2 1 horizontal direction when the R and G beams are converged, as shown in Figure 3 of the accompanying drawings, due to errors in assembly of the deflection yokes, positioning errors of the electron gun when it is placed in the neck portion, and installation errors of the deflection yokes. Until now, when the B and R beams are symmetrically deviated with respect to the G beam which is in between, adjustment has been achieved by dynamically applying to the outer convergence plates a common voltage having a parabolic waveform. However, it has not been possible to correct the misconvergence which occurs asymmetrically in the horizontal direction at both end portions on the X axis of the screen and at the four corners of the screen.

According to the present invention there is provided a cathode ray tube with a multiple beam electron gun which has convergence plates, comprising means for supplying individual voltages to said convergence plates so as to deflect the electron beam located on respective sides of a central electron beam.

The invention will now be described by way of example with reference to the accompanying drawings, throughout which like parts are referred to by like references, and in which:

Figure 1 is a sectional view of an embodiment of the invention; Figure 2 is a sectional view of the embodiment normal to Figure 1; Figures 3 and 4 are diagrams showing misconvergence; Figure 5 shows correction magnets; Figure 6 shows distortion of the shapeof beam spots; Figure 7 is a perspective view of an anode button; Figure 8 is a sectional view of the anode button of Figure 7; Figure 9 is a perspective view of another anode button; Figure 10 is a sectional view of the anode button of Figure 9; Figure 11 is a diagram for explaining another button arrangement; Figure 12 is a plan view of a connector; Figure 13 is a side view of the connector of Figure 12; Figure 14 is a side view of another connector; Figure 15 is a perspective view of part of the connector of Figure 14; Figure 16 is a side view of a shield member; Figure 17 is an exploded view perspective of the shield member of 1 4 3 i Figure 16; Figure 18 is a front view of a connection means; Figures 19 to 21 are plan, side and perspective views respectively of the connection means of Figure 18; and Figure 22 is a perspective view of another form of connection means.

Figures 1 and 2 show a TRINITRON type cathode ray tube 1 forming an embodiment of the present invention. The body 2 of the cathode ray tube 1 is formed of a panel portion 3, a funnel portion 4, and a neck portion 5 within which is mounted an electron gun 6. On the side towards the stem of the electron gun 6, there are mounted three cathodes 7R, 7G and 7B corresponding to red (R), green (G) and blue (B) beams in an in- line manner, and there are positioned sequentially ahead of the cathodes 7R, 7G and 7B, and coaxially with respect to the centre axis, a first grid G1 which opposes the cathodes 7R, 7G and 7B, a common second grid G2, a third grid G3, a fourth grid G4, and a fifth grid G5.

In the stage succeeding the fifth grid G5, there is provided a convergence means 8, which is formed of inner convergence plates 8a and 8b which vertically oppose each other with the centre axis in between, and outer convergence plates 8e and 8d mounted outwardly of the inner convergence plates 8a and 8b and which oppose each other with the centre axis in between. Both the inner convergence plates 8a and 8b are electrically and mechanically connected to the fifth grid G5. The first grid G1, the second grid G2 and the third grid G3 have through holes therein for passing electron beams 9R, 9G and 9B which correspond to red, green and blue, and which are supplied from the respective cathodes 7R, 7G and 7B.

The third, fourth and fifth grids G3, G4 and G5 form a principal electron lens. The electron beams 9R, 9G and 9B cross virtually in the centre of the principal electron lens, and then the R beam 9R and the B beam 9B which are located on respective sides of the central G beam 9G diverge. While the G beam 9G in the centre travels straight between the inner convergence plates 8a and 8b, the R beam 9R and the B beam 9B are deflected while travelling between the inner convergence plates 8a and 8b and the outer convergence plates 8c and 8d which face each other, respectively, and are caused to converge again at a point 1 i 4 on the phosphor screen.

To cause the deflection, the inner convergence plates 8a' and 8b are supplied with an anode yoltage HV through an anode button 12 by means of conductive resilient contact members 10 which are attached to the fifth grid G5 and which have their free ends in contact with an inner conductive coating 11. The outer convergence plates 8c and 8d are individually supplied with respective voltages by convergence voltage supply means. The anode button 12 for supplying these voltages is shown in Figures 7 and 8, and is formed such that two conductive pines 15a and 15b supply the respective outer convergence plates 8c and 8d with the individual voltages, and are mounted parallel to each other in the centre of a shell 13 which is formed of a conductive material so as to supply the anode voltage HV, and which are insulated by duraglass (barium glass including alumina powder) 14.

Alternatively, the anode button 12 shown in Figures 9 and 10 can also be used, this having a first pin 15a formed as a cylindrical conductor so as to supply one convergence plate 8c, and mounted within the shell 13 which is formed of a conductor and is insulated therefrom by duraglass 14. A second conductive pin 15b supplies the other convergence plate 8d and is mounted within the pin 15a and is insulated therefrom by duraglass 14.

An arrangement may also be provided wherein two anode buttons of known type each of which have a conductive pin mounted within a shell and insulated therefrom by duraglass are used, and which are mounted on the left and the right sides of the funnel portion 4 as shown in Figure 11, so as to supply the outer convergence plates 8c and 8d with their respective voltages. In such arrangement, however, the construction of the funnel portion 4 is required to be modified, and it is also required that high voltage lead wires be laid along the periphery of the cathode ray tube 1 with consequent risk that electrical leakage will occur. Therefore, in actual practice, the two previously described types of anode button 12 are preferred. The shell 13 and the pins 15a and 15b are made of a material such as 426 alloy, for example, and are provided with surface treatment by oxide coating.

The supply of the voltages to each of the outer convergence plates 8c and 8d from the anode ' button 12 is performed in the k- 1 following manner. First, when using the anode button 12 shown in Figures 7 and 8, a connector 17 for connecting the two parallel pins 15a and 15b respectively to lead wires 16a and 16b is formed as shown in Figures 12 and 13, such that metal members 20a and 20b are provided which have bent portions 19 which are capable of mating with the pins 15a and 15b, respectively, and are fixed by fastening members 21 to a ceramic board 18, in which through holes for the two pines 15a and 15b are formed. The lead wires 16a and 16b for supplying voltages to the respective outer convergence plates 8c and 8d are fixed to the metal members 20a and 20b, and thereby, electrical connections between the lead wires 16a and 16b and the pins 15a and 15b are achieved through the metal members 20a and 20b.

Then, in the case of the anode button 12 shown in Figures 9 and 10, a connector 17 for connecting the two coaxial pins 15a and 15b with the lead wires 16a and 16b is shown -in Figures 14 and 15, and is formed of a lower metal member 24 which has a through hole 22 formed therein which is large enough not to come into contact with the central pin 15b, and which has both side portions 23a and 23b folded so that they make contact with the periphery of the outer pin 15a and an upper metal member 27 which is fixed over the lower metal member 24 and has bent portions 19 capable of mating with the central pin 15b. A ceramic plate 26 having a through hole 25 so as to allow the central pin 15b to pass therethrough is mounted in between. The lead wires 16a and 16b for supplying voltages to the respective outer convergence plates 8c and 8d are welded to the upper metal member 27 and to the lower metal member 24, and thus, electrical connections between the lead wires 16a and 16b and the pins 15a and 15b are achieved through the metal members 27 and 24. In the case where this type of connector 17 is used, the lead wires 16a and 16b are connected so that they extend vertically, and therefore, they must be twisted through an angle of 900 so they can be laid along the inside of the funnel portion 4. It is preferable that the twisted portion 28 be provided within 25 mm of the pins 15a and 15b.

There is provided a shield member 29 as shown in Figures 1, 2, 16 and 17 for enclosing therein the anode button 12 and the connector 17 within the funnel portion 4. The shield member 29 is made up of an upper member 30 and a lower member 31. The member 30 fits over the 6 member 31, and since in the case where the connected ends of the lead wires 16a and 16b extend vertically, the twisted portion 28 must also be accommodated by the shield member 29, and both of the members 30 and 31 are provided with portions 30a and 31a extending in the 5 direction of the lead wires 16a and 16b. The shield member 29 is especially provided so as to prevent the occurrence of a short circuit due to a getter which is used at the time of gettering of the cathode ray tube 1. Then, the lead wires 16a and 16b which are connected to the anode button 12 are led to the neck portion 5 along the inside of the funnel portion 4, and there they are connected -to their respective outer convergence plates 8c and 8d as described below. The lead wires 16a and 16b are covered by an insulating material 32, and the lead wires 16a and 16b with the insulating material 32 thereon are inserted into conductive pipes 33a and 33b. Connection means 34 for connecting the lead wires 16a and 16b to their respective outer convergence plates 8a and 8b is constructed, as shown in Figures 1 and 2 and Figures 18 to 21, such that the end portions 35a and 35b of the conductive pipes 33a and 33b are separated from each other so as to form a V, so that a bead glass 36 of the electron gun 6 will not touch the connection means 34 and the end portions 35a and 35b of the V-portion 39 thus formed is opened at least as wide as the width of the bead glass 36, for example approximately 12 mm, and the lead wires 16a and 16b which are led out of the end portions 35a and 35b are welded to resilient sheet members 38a and 38b, which have conductive resilient contact members 37a and 37b formed integrally therewith. Reference numeral 43 denotes insulating pipes. There is also provided a symmetrical support spring 41 which has a base portion 40 which is welded to the V-portion 39 of the two conductive pipes 33a and 33b. The support spring 41 is provided so as rigidly to support the lead wires 16a and 16b because they are positioned in contact with the inner conductive coating 11 of the neck portion 5. By applying the anode voltage HV to the conductive pipes 33a and 33b through the inner conductive coating 11 and the support spring 41, disturbance of the electrical field due to the mounting of the lead wires 16a and 16b, to which is applied the convergence voltage CV, on the inside of the funnel portion 11 can be avoided. The support spring 41 can be provided by punching it out of 1 1 7 a conductive sheet such that its base portion 40 is not separated.

The support spring 41 can also be provided, as shown in Figure 22, by having two linear conductive resilient members which are welded to the conductive pipes 33a and 33b and which correspond to the lead wires 16a and 16b at the V-portion 39. By the use of the support spring 41, an effect is obtained such that generation of eddy current therein due to the magnetic field from the deflection yoke is less likely as compared with the case where a previously known support spring is used.

Since in the embodiment the voltages to be applied to each of the outer convergence plates 8c and 8d in the convergence means 8 within the electron gun 6 can be individually adjusted, the horizontal misconvergence at the centre portion and peripheral portion of the screen can be eliminated. Hence, it follows only that care is required to be taken for vertical misconvergence in c6nnection with the deflection yokes, and the freedom during designing the deflection yoke is increased, and ease of designing the deflection yoke so as to produce smaller spot distortion becomes possible. Moreover, since the need for six-pole magnets or the like for correction of the horizontal misconvergence is eliminated, the prior problem of deterioration in the shape of the beam spots is overcome.

i 41 8

Claims (6)

1. A cathode ray tube with a multiple beam electron gun which has convergence plates, comprising means for supplying individual voltages to said convergence plates so as to deflect the electron beam located on respective sides of a central electron beam.

2. A cathode ray tube according to claim 1 compri sing an anode button having a plurality of voltage supply pins corresponding in number to the number of said convergence plates.

3. A cathode ray tube according to claim 2 wherein the end portions of a plurality of lead wires which extend from said anode button and which are for supplying voltages to said convergence plates are opened outwardly to form a space at least as wide as the width of a bead glass of said electron gun.

4. A cathode ray tube according to claim 2 or claim 3 wherein said anode button has two parallel extending said voltage supply pins.

5. A cathode ray tube according to claim 2 or claim 3 wherein said anode button has a first cylindrically shaped said voltage supply pin and a second said voltage supply pin which extends concentrically from said first said voltage supply pin.

6. A cathode ray tube substantially as the embodiment or any of the modified embodiments hereinbefore described with reference to Figures 1, 2 and 7 to 22 of the accompanying drawings.

Published 1988 at ne Patent Office, State House, 66171 High Holborn, London WC1R 4TP. Further copies may be obtained from The Patent Office,