Deflection apparatus and cathode ray tube with the deflection apparatus

Abstract

 Provided is a cathode ray tube having a deflection apparatus that can precisely correct a screen distortion caused by mis-convergence of electron beams. The deflection apparatus includes horizontal and vertical deflection coils, and a separator disposed between the horizontal and vertical deflection coils. At least one of the horizontal and vertical deflection coils comprises main deflection portions having respective first ends close to a neck and respective second ends close to a panel, a first flange portion interconnecting the first ends, and a second flange portion interconnecting the second ends. The second flange portions includes a plurality of sections spaced apart from each other, and at least one of the sections is indented from a reference line defined in a circumferential direction of a cone portion toward the first flange portion.

Description

BACKGROUND OF THE INVENTION

Field of the Invention

[0001] The present invention relates to a cathode ray tube, and more particularly, to a deflection apparatus that deflects electron beams by generating a deflection magnetic field.

Description of Related Art

[0002] A cathode ray tube is a display device that can display an image by deflecting electron beams in horizontal and vertical directions of a screen and exciting phosphors of the screen using the electron beams. The deflection of the electron beams is realized by a deflection apparatus that is disposed around a funnel of the cathode ray tube to generate a horizontal deflection magnetic field and a vertical deflection magnetic field.

[0003] The deflection apparatus includes a pair of horizontal deflection coils installed inside a separator, a pair of vertical deflection coil disposed outside the separator, and a ferrite core that is installed outside the separator in association with the vertical deflection coils.

[0004] Generally, the deflection coil includes a pair of main deflection portions, a first flange portion interconnecting first ends of the pair of main deflection portions, and a second flange portion interconnecting second ends of the pair of main deflection portions. Here, the first ends are close to a neck of the cathode ray tube and the second ends are close to a panel of the cathode ray tube.

[0005] In the deflection coil, the main deflection portions generate a main deflection magnetic field that mainly affects a scan path of the electron beams while the second flange portion functions to correct a mis-convergence such as a 1/2 N/S distortion or a trilemma, which is caused by a difference between a deflection distance with respect to a central portion of the phosphor screen and a deflection distance with respect to four corner portions of the phosphor screen.

[0006] In a conventional deflection coil, the second flange portion interconnecting the second ends of the main deflection portions is designed to be straight between the second ends of the main deflection portions. When the deflection coil is actually mounted on the funnel of the cathode ray tube, the degree to which the second flange portion can come close to the scan path of the electron beams is limited. Therefore, a mis-convergence correction function cannot be maximized and precisely realized.

[0007] Considering that flattened, large-sized cathode ray tube consumption is on the rise, this limitation meansthat the maximum display quality cannot be provided to users.

SUMMARY OF THE INVENTION

[0008] According to a first aspect of the invention there is provided a deflection apparatus for a cathode ray tube as set out in claim 1. Preferred features of this aspect are set out in claims 2 to 7.

[0009] According to a second aspect of the invention there is provided a cathode ray tube as set out in claim 8. Preferred features of this aspect are set out in claims 9 and 10.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] These and/or other aspects and advantages of the invention will become apparent and more readily appreciated from the following description of embodiments of the invention, taken in conjunction with the accompanying drawings of which:

FIG. 1 is a side view of an image display device having a cathode ray tube according to an exemplary embodiment of the present invention;

FIG. 2 is a top plan view of a cathode ray tube according to an exemplary embodiment of the present invention;

FIG. 3 is a perspective view of a cone portion of a cathode ray tube according to an exemplary embodiment of the present invention;

FIG. 4 is a top plane view of a deflection apparatus of a cathode ray tube according to an exemplary embodiment of the present invention;

FIGS. 5A and 5B are perspective views of a horizontal deflection coil of a cathode ray tube according to an exemplary embodiment of the present invention;

FIG. 6 is a perspective view of a deflection coil according to another embodiment of the present invention;

FIG. 7 is a perspective view of a deflection coil of a deflection apparatus of a cathode ray tube according to a comparative example; and

FIG. 8 is a schematic view of a screen of a cathode ray tube, illustrating a 1/2 N/S characteristic.

DETAILED DESCRIPTION OF THE EMBOIMENTS

[0011] The present invention will now be described more fully with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. The invention may, however, be embodied in many difference forms and should not be construed as being limited to the embodiments set forth herein. Rather these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of the invention to those skilled in the art.

[0012] Referring to FIG. 1, an image display device includes a cathode ray tube 10, a case 12 surrounding the cathode ray tube 10 and defining an outer appearance of the image display device, and a support 14 supporting the case 12.

[0013] The case 12 includes front and back cases 121 and 122 that are respectively disposed in front and rear of the cathode ray tube 10. The front and rear cases 121 and 122 are coupled to each other by screws, but other coupling methods could be used in other embodiments. The cathode ray tube 10 is mostly located in the case 12 except for a neck portion located in the support 14.

[0014] FIG. 2 is a top plan view of the cathode ray tube.

[0015] Referring to FIG. 2, the cathode ray tube 10 includes a vacuum tube having a panel 16 formed in an approximately rectangular shape and having a phosphor screen (not shown) formed on an inner surface thereof, a funnel 18 connected to a rear end of the panel 16 and having a cone portion 181, and a neck 24 connected to a rear end of the cone portion 181. A deflection apparatus 20 is mounted on an outer circumference of a cone portion 181 of the funnel 18. An electron gun 22 is inserted in the neck 24.

[0016] As is well known, the cathode ray tube 10 displays an image by (a) deflecting electron beams emitted from the electron gun 22 along a horizontal axis (an x-axis in FIG. 2) and a vertical axis (a y-axis in FIG. 2) using a deflection magnetic field generated by the deflection apparatus 20 and (b) allowing the electron beams to pass through beam passing apertures of a color selection apparatus (not shown) installed inside the panel 16 and to collide with desired phosphors of the phosphor screen.

[0017] FIG. 3 is a perspective view of the cone portion.

[0018] Referring to FIGs. 2 and 3, the cone portion 181 on which the deflection apparatus 20 is installed is designed such that a shape of a vertical section with respect to a tube axis (the z-axis of FIGs. 2 and 3) is gradually changed from a circular shape to a non-circular shape (i.e., a rectangular shape) having a maximum length in a direction other than the directions of the horizontal and vertical axes (the x and y-axes) of the panel 16 as it goes from a neck 24 side to a panel 16 side.

[0019] The above-described shape of the cone portion 181 increases a deflection sensitivity for deflecting the electron beams, thereby reducing the electric power consumption for the deflection.

[0020] Alternatively, the cone portion 181 on which the deflection apparatus 20 is installed is designed such that a shape of a vertical section with respective to the tube axis is formed in a circular shape whose diameter is gradually reduced as it goes from the panel 16 side to the neck 24 side.

[0021] FIG. 4 is a top plane view of the deflection apparatus mounted on the outer circumference of the cone portion.

[0022] Referring to FIG. 4, the deflection apparatus 20 includes a separator 26 that is formed of an insulation material, a pair of horizontal deflection coils 28 disposed on an inner portion of the separator 26 at upper and lower sides of the electron beam path, a pair of vertical deflection coils 30 disposed on an outer portion of the separator 26 at left and right sides of the electron beam path, a ferrite core 32 mounted on the outer portion of the separator 26 while enclosing the vertical deflection coils 30.

[0023] The horizontal deflection coils 28 form a pin cushion-shaped magnetic field along the vertical axis (the y-axis) of the panel 16 to deflect the electron beams in the direction of the horizontal axis (the x-axis) of the panel 16. The vertical deflection coils 30 form a barrel-shaped magnetic field along the horizontal axis (the x-axis) to deflect the electron beam in the direction of the vertical axis (the y-axis) of the panel 16. The ferrite core 32 functions to improve the magnetic efficiency by reducing the loss of the magnetic force generated from the deflection coils 28 and 30.

[0024] The deflection apparatus 20 has a shape corresponding to a shape of an outer surface of the cone portion 181. That is, when the cone portion 181 is formed in a shape shown in FIG. 3, the deflection apparatus 20 is also formed such that a vertical section thereof is gradually changed from a circular shape to a rectangular shape as it extends from the neck 24 side to the panel 16 side.

[0025] In one embodiment of the present invention, one of the horizontal and vertical deflection coils 28 and 30 of the deflection apparatus 20 is formed in the following structure in order to more precisely correct the screen distortion caused by the mis-convergence of the electron beams.

[0026] FIGS. 5A and 5B are perspective views of a deflection coil of a cathode ray tube according to an exemplary embodiment of the present invention. In this embodiment, a horizontal deflection coil corresponding to the shape of the cone portion of FIG. 3 is illustrated as an example.

[0027] Referring to FIGs. 5A and 5B, the horizontal deflection coil 28 includes a pair of main deflection portions 34 having first ends close to the panel 16 and second ends close to the neck 24, a first flange portion 36 interconnecting the first ends, and a second flange portion 38 interconnecting the second ends. The second flange portion 38 has a length longer than that of the first flange portion 36.

[0028] The second flange portion 38 includes a plurality of sections spaced apart from each other. At least one of the sections is indented toward the first flange portion 36 with respect to a reference line set in a circumferential direction of the cone portion 181. Here, the circumferential direction means a direction rotating by one turn around the cone portion 181 while being vertical with respect to the tube axis (the z-axis) of the cathode ray tube.

[0029] For example, the second flange portion 38 can be divided into a first section 381 further from the first flange portion 36 and a second section 382 closer to the first flange portion 36. A coil winding amount of the first section 381 may be less than that of the second section 382. In addition, the first section 381 may be substantially formed in a rectangular shape corresponding to the shape of the outer surface of the cone portion 181.

[0030] The division of the first and second sections 381 and 382 is for independently correcting the distortion of the central portion of the screen and the distortion of the periphery portion of the screen. That is, the first section 381 of the second flange portion 38 mainly corrects the distortion of the periphery portion of the screen and the second section 382 of the second flange portion 38 mainly corrects the distortion of the central portion of the screen.

[0031] Further, each of the first and second sections 381 and 382 is indented at a portion (i.e., a central portion) from a corresponding reference line (reference lines a-a and b-b of FIG. 5B), which is set in a circumferential direction of the cone portion 181, toward the first flange portion 36. The reference line contacts the outermost part each of the first and second sections 381 and 382. The indentation of the second flange portion 38 toward the first flange portion 36 is for more precisely correcting the distortion of the central portion of the screen.

[0032] As shown in FIGs. 5B, the indentation of each of the first and second sections 381 and 382 may be formed with two bending points A, B.

[0033] Alternatively, as shown in FIG. 6, each of first and second sections 381' and 382' is indented at a portion (i.e., a central portion) from a corresponding reference line (reference lines a'-a' and b'-b'), which is set in a circumferential direction of the cone portion 181, toward the first flange portion 36. At this point, the indentation may be formed with one bending point C, D. That is, the indentation is formed in a V-shape notch.

[0034] The bending point A, B, C, D may be defined at a portion where the second flange portion 38, 38' receives an external force for bending the second flange portion 38, 38' toward the first flange portion 36, 36'. The number and location of the bending points are not limited to the above-described embodiments.

[0035] As described above, the deflection apparatus 20 is designed to independently correct the mis-convergence of the electron beams at the central and periphery portions of the screen by varying the deflection magnetic fields. Furthermore, the deflection apparatus 20 is designed to correct more precisely the mis-convergence of the electron beam at the central portion of the screen.

[0036] A cathode ray tube (hereinafter, "embodiment") having the above-described deflection apparatus and a cathode ray tube (hereinafter, "comparative example") having a conventional deflection apparatus were tested to measure a 1/2 N/S property and a trilemma property.

[0037] The deflection coil shown in FIG. 5A is applied as the horizontal deflection coil of the deflection apparatus of the embodiment and a deflection coil shown in FIG. 7 is applied as the vertical deflection coil of the deflection apparatus of the example. The deflection coil shown in FIG. 7 is applied as each of horizontal and vertical deflection coils of the deflection apparatus of the comparative example.

[0038] As shown in FIG. 7, a deflection coil 40 of the comparative example has a second flange portion 45 and a pair of main deflection portions 44. Second ends of the main deflection portions 44 are interconnected by a straight shape second flange portion 42.

[0039] The test was conducted by applying an identical deflection electric power to the embodiment and the comparative example. The test results are shown in the following table 1.

[Table 1]

	Comparative Example	Embodiment	Remark
1/2 N/S (mm)	2.5	1.7	Improvement by 0.8
Trilemma (mm)	+1.5	+0.3	Improvement by 1.2

[0040] As shown in FIG. 8, when horizontal lines are defined at 1/2 N/S points between a screen center and a screen upper end and between the screen center an a screen lower end and a pincushion distortion occurs due to the deflection of the electron beams by the deflection magnetic field, the 1/2 N/S property is a distance "d" between an electron beam scan line and each of the horizontal line. As can be noted from the table 1, the deflection apparatus of the embodiment is improved by 0.8mm compared to that of the comparative example.

[0041] The trilemma property is a distance between three lines of electron beams that do not coincide with each other but are spaced apart from each other at a diagonal corner portions by the horizontal and vertical deflection magnetic fields. As can be noted from the table 1, the deflection apparatus of the embodiment is improved by 1.2mm compared to that of the comparative example.

[0042] Although exemplary embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes may be made in this embodiment without departing from the principles of the invention, the scope of which is defined in the claims and their equivalents.

Claims

1. A deflection apparatus for a cathode ray tube comprising;

horizontal and vertical deflection coils; and

a separator disposed between the horizontal and vertical deflection coils,

wherein the deflection apparatus is installed on an outer circumference of a cone portion of the cathode ray tube,
wherein at least one of the horizontal and vertical deflection coils comprises:

two main deflection portions having a respective first end and a respective second end;

a first flange portion interconnecting the first ends; and

a second flange portion interconnecting the second ends and having a length longer than that of the first flange portion,

wherein the second flange portion includes a plurality of sections spaced apart from each other, and at least one of the sections is indented from a reference line defined in a circumferential direction of the cone portion toward the first flange portion.

2. A deflection apparatus according to claim 1, wherein the plurality of sections includes:

a first section; and

a second section disposed between the first section and the first flange portion.

3. A deflection apparatus according to claim 2, wherein each of the first and second sections is indented toward the first flange portion at its central portion.

4. A deflection apparatus according to claim 3, wherein each of the first and second sections has at least one bending point.

5. A deflection apparatus according to claim 3 or 4, wherein the indented portion of each of the first and second sections is formed in a notch-shape.

6. A deflection apparatus according to any one of the claims 2-5,
wherein a coil winding amount of the first section is less than that of the second section.

7. A deflection apparatus according to any one of claims 1 to 6,
wherein the at least one of the deflection coils is the horizontal deflection coil.

8. A cathode ray tube comprising:

a vacuum tube including a panel having a phosphor screen formed on an inner surface thereof, a funnel having a cone portion, and a neck in which an electron gun is installed; and

a deflection apparatus installed on an outer circumference of the cone portion,

wherein the deflection apparatus is according to any one of claims 1 to 7, wherein the first ends are located near the neck and the second ends are located near the panel.

9. A cathode ray tube according to claim 8, wherein the cone portion is arranged such that a shape of a vertical section thereof with respect to a tube axis is gradually changed from a circular shape to a non-circular shape having a maximum length in a direction other than the directions of horizontal and vertical axes of the panel as it extends from a neck side to a panel side.

10. A cathode ray tube according to claim 8 or 9, wherein at least one of the deflection coils is shaped to correspond to a shape of an outer surface of the cone portion.

Drawing