Electric lamp and discharge devices: systems – Cathode ray tube circuits – Combined cathode ray tube and circuit element structure
Reexamination Certificate
2001-03-30
2003-03-25
Wong, Don (Department: 2821)
Electric lamp and discharge devices: systems
Cathode ray tube circuits
Combined cathode ray tube and circuit element structure
C315S005380, C315S368160, C313S412000, C313S413000, C313S414000
Reexamination Certificate
active
06538385
ABSTRACT:
CROSS-REFERENCES TO RELATED APPLICATIONS
This application claims priority from Japanese Patent Application No. 00-192665, filed on Jun. 22, 2000, and Japanese Patent Application No. 00-357615, filed on Nov. 20, 2000, which are both incorporated by reference for all purposes.
BACKGROUND OF THE INVENTION
This invention relates to shapes of holes of a flat electrode of electronic gun of cathode-ray tube for use in a display device, particularly in a CRT display device, and a method for processing the flat electrode, wherein three electron beam passage holes are formed in the flat electrode of electronic gun for improving the hole diameter precision and enhancing the resolution of focus lenses.
In recent years, the enhancement of the resolution of electronic gun components of a cathode-ray tube for color television has been increasingly demanded as the progress of the minuteness and definition of the image of color display. The resolution of an electronic gun can be enhanced by deterring the occurrence of bur which induces electron discharge as viewed from the improvement of the assembly precision of the electronic gun by highly precise components and the enhancement of the withstand voltage characteristics of the electronic gun.
A cathode-ray tube (
FIG. 1
) for color image display consists of a panel section
1
which is an image screen, a neck section
2
for accommodating the electronic gun, and a funnel section
3
which connects panel section
1
and neck section
2
, and the funnel section
3
having a deflector which makes the electron beam
5
(Bc, Bs) emitted from an electronic gun
4
scanning on a fluorescent surface
6
of the color display.
Electronic gun
4
to be installed in the neck section
2
has various electrodes, such as a cathode electrode, control electrode, focusing electrode, and accelerating electrode. Electron beam
5
which is emitted from the cathode electrode is modulated by the signal to be applied to the control electrode. Modulated electron beam
5
is given a required sectional shape and energy through the focusing and accelerating electrodes. The formed and energized modulated electron beam is made to collide with fluorescent surface screen
6
. On the way that the electron beam from electronic gun
45
reaches fluorescent surface screen
6
, the electron beams are deflected to both the horizontal and vertical directions by the deflector installed in funnel
3
to form an image on fluorescent surface screen
6
.
On the other hand, electronic gun
4
of this kind of color cathode-ray tube has a cylindrical electrode having a nearly elliptical peripheral shape, inside which flat electrodes having electron beam passage holes are disposed. (Japanese App. No. 59-215640).
FIG. 2
is a plan view showing a block diagram of such a flat electrode, and
FIG. 3
shows a sectional view of the electron beam passage hole. The flat electrode has three electron beam passage holes
8
,
9
, and
10
.
In the prior art, in the production of a flat electrode having the electron beam passage holes
8
,
9
, and
10
, a flat electrode including electron beam passage holes was shaped by means of through punching using a usual press machine. In this case, as an enlarged sectional view of electron beam passage hole
9
of
FIG. 3
shows, a sheared surface
11
and a broken-out surface
12
are formed on the inner surface of electron beam passage hole
9
, resulting in a bur
13
on the outer surface of the metal plate. In the usual punching off method, sheared section length t
1
accounted for about 60% of plate thickness t, while broken-out section length t
2
accounted for as much as 40% of the plate thickness t. Further, some metal plates developed burs as high as 0.01 mm on their outer surfaces.
The existence of this broken-out section
12
causes distortion mainly in the focus lens. Accordingly, in a flat electrode of which a distortion developed in the focus lens is required to be as a particularly small as possible, such a method for punching out holes in the flat electrode is applied that when punching the flat electrode from the other side surface thereof, a hole smaller than the hole to be finally punched out is punched once, and after that a shaving method is applied to enlarge the hole until it finally meets a required diameter (Japanese App. No. 3-17964).
This shaving method, as the conceptual diagram of
FIG. 4
shows, is required to punch metal plate
14
a few times to achieve a hole having a diameter D so that necessary electron beam can pass through. For example, a punch
15
that can make holes with diameters of 0.5D, 0.7D, 0.9D, and 1D in a metal plate is used to enlarge the hole diameter one by one until an objective length has been reached. As a consequence, the number of times required for punching increases. The use of such a punching process, in comparison with the usual punching off method, can reduce the thickness of broken-out surface to a range of 10-20% of plate thickness t and the length of bur
13
to below 0.005 mm. In order to achieve the high resolution of an up-to-date cathode-ray tube, more precise punching is required.
Further, bur
13
causes a decline of mainly the withstand voltage characteristic of the focus lens. Although an attempt is made to remove bur
13
from the outer edge of the hole by means of barrel grinding, the end of the hole may be rounded, and an excessive rounding at the end of the hole may result in undesirable distortion of the focus lens, thereby declining the resolution of the focus lens.
The purpose of the present invention is to provide a punching method for making the broken-out section
12
shorter compared with the conventional processing method to achieve flat electrode
7
without bur
13
and a desirable flat electrode of electronic gun.
In the color cathode-ray tubes of the prior art, a shaving method was used that requires punching a few times to punch out electron beam passage holes highly precisely on a flat electrode of electronic gun so that the number of times required for punching increases, resulting in a production cost increase. In addition, because even this shaving method leaves problems that the broken-out section length of around 20% and the difficulty of removing bur completely, there was a limitation in the enhancement of the withstand voltage characteristic of electron beam.
BRIEF SUMMARY OF THE INVENTION
It is an object of the present invention to provide a method for resolving the problems, and in order to achieve the above-mentioned object, a cathode-ray tube has a metal plate having a hole, wherein electron beam passes through, and wherein the hole is different in diameter between the upper surface and lower surface of the metal plate.
Further, in order to achieve the aforementioned object, a cathode-ray tube of a metal plate having a hole, through which an electron beam from the electrode of an electronic gun passes through; wherein there exists a difference in the diameter of the hole between the upper and lower surfaces of the metal plate; and wherein the pertinent difference in diameter is within a range of ratio from 0.01 to 0.4 relative to the metal plate.
Further, in order to achieve the aforementioned objects, a cathode-ray tube of a metal plate, through which an electron beam from the electrode of an electronic gun passes; wherein there exists a difference in the diameter of the hole between the upper and lower surface of the metal plate; and wherein the pertinent difference in diameter is within a range of ratio of 0.01-0.2 relative to the metal plate.
Further, in order to achieve the aforementioned objects, a cathode-ray tube of a metal plate, through which an electron beam from the electrode of an electronic gun passes; wherein there exists a difference in the diameter of the hole between the upper and lower surfaces of the metal plate; wherein there exists a difference in the diameter of the hole, wherein there exists a difference in the hole pitch between the upper and lower surfaces of the metal plate; and wherein the ratio of the difference in the hole pitch on
Endo Satoru
Hatada Naozumi
Kanetoo Osami
Kato Shin-ichi
Mera Takeshi
Hitachi , Ltd.
Townsend and Townsend / and Crew LLP
Vo Tuyet T.
Wong Don
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