Patent Grant
7038367
This application claims the benefit of Korean Patent Application No. 2002-0051541, filed on Aug. 29, 2002, which is hereby incorporated by reference for all purposes as if fully set forth herein.
1. Field of the Invention
The present invention relates to an electron gun for a cathode ray tube, and more particularly, to an electron gun for a cathode ray tube driven using a dynamic focus method.
2. Discussion of the Related Art
The resolution of a cathode ray tube (CRT) is determined by characteristics of the electron beams. The characteristics include the focal point characteristics of the electron beam. In order to obtain quality images on the display, the electron beams landing on the phosphor screen must land on all areas of the phosphor screen. For example, the electron beams must land on the center and peripheral portions of the screen and have a small halo.
In the related art CRTs the electron beam holes for red (R), green (G), and blue (B) electron beams are arranged in an in-line configuration. A magnetic field is used to deflect electron beams into a pin cushion shape for a horizontal deflection and a barrel shape for vertical deflection. As a result, the focal point of the electron beams landing in the peripheries of the screen is distorted by astigmatism, which is caused by the non-uniform magnetic fields formed in the deflection apparatus. A reduction in the CRT resolution is caused by the distortion of the focal points of the electron beams in scanning peripheries and center, that is these focal points are different.
Accordingly, a dynamic focus electron gun is employed in the related art CRTs to remedy this problem. Dynamic focusing refers to the application of a dynamic focus voltage. The dynamic focus voltage creates a higher focus voltage than the normal focus voltage when the peripheries of the screen are scanned by the electron beams. Accordingly, the focal point formation on the peripheries is compensated using this technique.
The electrons to which the dynamic focus voltage is applied are typically realized through two interconnected electrodes. The electrodes may be cup-shaped and/or plate-shaped or any combination thereof, and are generally welded together.
An electromagnetic field is formed in the area of the electron gun by a deflection magnetic field formed by the deflection apparatus. The voltage is synchronized with the horizontal deflection magnetic field signal, that is a part of the deflection magnetic field, and applied to the dynamic focus electrodes.
However, in the related art dynamic focus CRT systems, noise is generated in the area of the electron gun and interferes with the operation of the device, thereby reducing the quality of the device. Vibration of the dynamic focus electrodes generates the noise and the vibration is caused by a dynamic focus voltage applied to the electrodes. However, the dynamic focus voltage generates the electromagnetic field and electromagnetic force and causes the electrodes to vibrate.
Korean Laid-Open Patent No. 2001-0018045 discloses such a dynamic focus electron gun. Further, there is disclosed in Korean Laid-Open Patent No. 2001-0057789 an electron gun for a color Braun tube that improves an insertion depth structure of electrodes with respect to bead glass, and a structure for wires connected to electrodes and stem pins to reduce the noise.
However, in the above related art electron guns, the structure directly responsible for the generation of noise is not altered. Instead the structure in the general area is improved (i.e., the insertion sections of the electrodes that are inserted into the bead glass or the wire structure). Therefore, only a minimal reduction in noise is realized.
Noise is generated by the electrodes of the electron gun at specific frequencies, for example, at 7.4 kHz or 12 kHz. If an attempt is made to reduce noise by varying the specific frequency in the indirect and not the direct area of the noise source, that is, in the path through which the vibrations caused by the noise occur, then it becomes difficult to vary the frequency with respect to the noise source. Further, if the vibrations caused by the noise source pass through a path other than the one normally taken, then the effectiveness in reducing the vibrations through conventional methods decreases considerably.
It is an aspect of the present invention to provide an electron gun for a cathode ray tube that reduces noise caused by a dynamic focus voltage.
An electron gun for a cathode ray tube includes a triode portion including cathodes, a first electrode, and a second electrode arranged with predetermined gaps therebetween. A plurality of electrodes arranged in sequence starting from a position adjacent to the second electrode. The electrodes receiving a voltage, for example, a constant voltage or a dynamic voltage. The dynamic voltage is synchronized with a deflection signal of electron beams. An anode electrode is positioned having a predetermined gap between the electrode arranged farthest from the cathodes. A support for supporting the electrodes at predetermined intervals. One of the electrodes is a multiple-element electrode that includes two interconnected sub-electrodes. Gaps are formed between the sub-electrodes of the multiple-element electrode. The electrode may receive a constant voltage or a dynamic voltage, which is synchronized with a deflection signal of electron beams.
The sub-electrodes of the multiple-element electrode may be cup-shaped and/or plate shaped or any combination. The cup-shaped sub-electrodes have different dimensions, and the gaps are formed between ends of the sub-electrodes. The sub-electrodes may include a container having electron beam passage holes and a flange is formed extending from a circumference of an opening of the container. Additionally, the sub-electrode may include insertion members formed extended from the flange, the insertion members may be fixedly inserted into the support.
The cup-shaped sub-electrodes may have at least one identical dimensions and the gap may be formed between circumferences of the sub-electrodes. Protrusions may be formed on opposing surfaces of the cup-shaped sub-electrodes for connecting the sub-electrodes and forming a gap between the sub-electrodes.
In another aspect, one of the sub-electrodes of the multiple-element electrode is cup-shaped and the other sub-electrode is plate-shaped. The cup-shaped sub-electrode and the plate-shaped sub-electrode have at least one substantially identical dimension. A gap may be formed between circumferences of the sub-electrodes. Protrusions may be formed on opposing surfaces of the cup-shaped sub-electrodes, and the sub-electrodes are connected with the protrusions in such a way to form a gap.
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention.
Reference will now be made in detail to various embodiments of the present invention, examples of which are illustrated in the accompanying drawings.
Referring to
A mask assembly may be arranged inwardly from the panel 22. The mask assembly includes a shadow mask 32 having a plurality of electron beam apertures formed therein, and a mask frame 34 for supporting the shadow mask 32. Further, an inner shield 36 may be connected to the mask frame 34 for shielding electron beams emitted from the electron gun 28 from the earth's magnetic field, when the electron beams are traveling toward the screen 20.
The electron gun 28 may be structured arranging three red (R), green (G), and blue (B) electron beam holes in an in-line configuration and adopts a dynamic focus method for operation. This will be described in more detail below.
The electron gun 28 forms a triode portion that includes cathodes 28a, a first electrode 28b, and a second electrode 28c arranged in this sequence with predetermined gaps between them. There are three of the cathodes 28a that are arranged in a line configuration corresponding to each of the R, G, B colors. Electron beam passage holes are formed in the first electrode 28b and the second electrode 28c corresponding to the cathodes 28a.
A plurality of electrodes 28d, 28e, 28f, and 28g are provided in this sequence starting after the second electrode 28c. These electrodes 28d, 28e, 28f, and 28g form a dynamic lens during operation of the electron gun 28. Electron beam passage holes are formed in the electrodes 28d, 28e, 28f, and 28g in a line and corresponding to the cathodes 28a, similar to those formed in the first electrode 28b and the second electrode 28c. The electrode 28e may be formed as a single unit. The electrode 28g may be formed of two sub-electrodes 280g and 282g (see
During operation of the electron gun 28 a constant voltage (Vf) or a dynamic voltage (Vd) synchronized with a deflection signal of the deflection apparatus 24, is applied to the electrodes. The dynamic voltage (Vd) refers to a varied voltage. That is, when the electron beams are deflected toward peripheries of the screen 20 the resulting spot of the electron beams is substantially identical to the electron beam on a center of screen 20.
The electron gun 28 also includes an anode electrode 28h arranged adjacent to the electrode 28g and positioned farthest away from the cathodes 28a. There is a predetermined gap between the anode electrode 28h and the electrode 28g. An anode voltage (Ve) is applied to the anode electrode 28h through a shield cup 28i which is connected to the anode electrode 28h. A support 28j for supporting the electron gun 28 as described above. The support 28j may be made of bead glass or other suitable material, thereby forming a single integral assembly.
Electron beams generated by the triode section of the electron gun 28 pass through the above plurality of electrodes to be focused and accelerated toward the screen 20, to display predetermined images.
The following structure is used in a embodiment of the present invention to reduce noise generated during operation of the electron gun 28. In particular, the electrode 28g formed of two sub-electrodes 280g and 282g as described above, is arranged such that there are gaps formed between the sub-electrodes 280g and 282g.
In this multiple-element electrode 28g according to this embodiment, gaps 38 may be formed between the sub-electrodes 280g and 282g. The sub-electrodes 280g and 282g are arranged into a single electrode by welding or any other suitable method. The sub-electrodes 280g and 282g are arranged such that the insertion members 2806g and 2826g are in a state where portions of the flanges 2804g and 2824g are in close contact and the gaps 38 are formed between other areas of the flanges 2804f and 2824g. For example, gaps 38 are formed at the ends of the sub-electrodes 280g and 282g.
A CRT that employs in its electron gun the electrode 28g as described has a substantial reduction in noise generation as compared to the related art CRT.
That is, by providing the gaps 38 between the sub-electrodes 280g and 282g that make up the multiple-element electrode 28g, friction between the sub-electrodes 280g and 282g caused by vibrations generated in the electrode 28g are reduced by the gaps 38, thereby minimizing the noise.
In the following embodiment variations of forming sub-electrodes and variations of the gap locations formed in the electrode will be described. However, a description of the operation will not be provided as the operation of the embodiments to be described is identical to that of the foregoing embodiment.
In the multiple-element electrode 60 according to an aspect of the present invention, the gap 62 size (c) and the gap 72 size (d) are greater than the thickness of at least one of the two sub-electrodes, thereby preventing deformation of the electrodes 60 and 70 by the electric fields formed in the area of the electrodes 60 and 70 during operation. The deformation causes undesirable frictions. The gap 62 size (c) and the gap 72 size (d) may be approximately three or more times thicker than at least one of the two sub-electrodes. That is, sub-electrodes 60a, 60b, 70a or 70b, which make up the electrodes 60 and 70, respectively substantially prevents weakness in the electrodes 60 and 70 and substantially prevents permeation of an electric field through the gaps 62 and 72.
The multiple-element electrodes 80 and 90 are formed differently from the electrodes of the other embodiments described above. The size (e) of the gap 82 formed by the sub-electrodes 80a and 80b and a size (f) of the gap 92 formed by the sub-electrodes 90a and 90b are larger than a thickness of at least one of the sub-electrodes. That is, the size (e) or (f) is larger than a thickness of 80a, 80b, 90a, or 90b, thereby preventing deformation of the electrodes 80 and 90 by the electric field formed in the vicinity of the electrodes 80 and 90 during operation of the electron guns preventing generation of friction.
The electron gun for CRTs of the present invention structured and operating as described above, reduces the noise caused by friction between elements during operation of the CRT. As result, the quality of the images displayed by the CRT is significantly improved.
Although preferred embodiments of the present invention have been described in detail hereinabove, it should be clearly understood that many variations and/or modifications of the basic inventive concepts herein taught which may appear to those skilled in the present art will still fall within the spirit and scope of the present invention, as defined in the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2002-0051541 | Aug 2002 | KR | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 5677590 | Matsuda et al. | Oct 1997 | A |
| 6353282 | Tojyou et al. | Mar 2002 | B1 |
| 6642646 | Kwon | Nov 2003 | B1 |
| 6819038 | Song et al. | Nov 2004 | B1 |
| Number | Date | Country |
|---|---|---|
| 1020010018045 | Mar 2001 | KR |
| 1020010057789 | Jul 2001 | KR |
| Number | Date | Country | |
|---|---|---|---|
| 20040041527 A1 | Mar 2004 | US |
