Electric lamp and discharge devices: systems – Cathode ray tube circuits – Cathode-ray deflections circuits
Reexamination Certificate
2001-05-17
2003-06-10
Wong, Don (Department: 2821)
Electric lamp and discharge devices: systems
Cathode ray tube circuits
Cathode-ray deflections circuits
C313S421000, C313S426000, C313S440000
Reexamination Certificate
active
06577082
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a braun tube reproducing a received electric signal as a video signal, and in particular to a deflection yoke for a braun tube which is capable of deflecting an electron beam radiated from an electron gun toward a screen.
2. Description of the Prior Art
A braun tube is for displaying a picture by converting an electric signal into an optical image such as a graphic, a character, etc. by an operation of an electron beam and is used for a video display unit such as a television, a monitor, etc.
As depicted in
FIG. 1
, a braun tube includes a funnel
10
as a vacuum bulb, a panel
12
maintaining a vacuum state by combining with the funnel
10
and reproducing colors by a R.G.B (Red, Green, Blue) fluorescent substance coated at its inner surface, an electron gun
14
installed at the rear of the funnel
10
and radiating R.G.B electron beams toward the panel
12
, a shadow mask
16
installed with a certain distance from the panel
12
and performing a color selection function, and a deflection yoke
20
installed at a neck portion
11
of the funnel
10
and deflecting an electron beam radiated from the electron gun
14
.
Herein, the deflection yoke
20
deflects an electron beam radiated from the electron gun
14
by using the principle of a magnetic field generated by a coil in order to make the electron beam sequentially contact to a pertinent pixel on a request position of a screen
12
a.
The deflection yoke
20
includes a horizontal deflection yoke
21
deflecting an electron beam in a horizontal direction on the basis of a center of deflection by generating a magnetic field in a vertical direction, a vertical deflection coil
23
deflecting an electron beam in a vertical direction on the basis of the center of deflection by generating a magnetic field in a horizontal direction, and a ferrite core
25
preventing a magnetic field generated by currents applied to the horizontal and vertical deflection coils
21
,
23
from leaking out and strengthening a magnetic force at the same time.
And, the deflection yoke
20
includes a holder
27
determining correlation positions of the horizontal deflection coil
21
and vertical deflection coil
23
, and guaranteeing insulation between them.
In the braun tube in accordance with the prior art, when an electron beam is radiated from the electron gun
14
, the electron beam reaches to the screen
12
a
through the deflection yoke
20
, herein the electron beam moves in a horizontal direction under the influence of a magnetic field of the horizontal deflection coil
21
and in a vertical direction under the influence of a magnetic field of the vertical deflection coil
23
.
Accordingly, the electron beam radiated from the electron gun
14
can reach to the whole parts of the screen
12
a
by motions in both the horizontal and vertical directions under the influence of the horizontal and vertical deflection coils
21
,
23
.
And, the ferrite core
25
is for forming the deflection force sufficiently by preventing the magnetic field generated by the vertical and horizontal deflection coils
21
,
23
from leaking out to a surrounding space and strengthening the magnetic force at the same time.
However, in the braun tube in accordance with the prior art, because the deflection yoke
20
is installed outside of the funnel
10
, it is easy to adjust a position of the deflection yoke
20
, accordingly the convergence and deflection sensitivity of an electron beam can be easily compensated. However, the deflection performance may lower due to expansion of the magnetic field from the center of the deflection. And, because the deflection yoke
20
is externally exposed, the deflection yoke
20
may be physically affected in the manufacturing process or delivery and has to be reset in that case.
Accordingly, in order to solve problems of the braun tube including the deflection yoke
20
installed outside of the funnel
10
, an in-neck deflection yoke type braun tube including the deflection yoke
20
which is installed inside the funnel
10
has been developed.
As depicted in
FIG. 2
, in an in-neck deflection yoke type braun tube, a deflection yoke
20
′ is installed inside a funnel
10
′.
In other words, a holder
27
′ attached to an electron gun
14
′ is installed inside the funnel
10
′, the holder
27
′ is constructed so as to support a horizontal deflection coil
21
′, a vertical deflection coil
23
′ and a ferrite core
25
′.
As described above, when the deflection yoke
20
′ is installed inside the funnel
10
′, a neck portion
11
′ of the funnel
10
′ is wider than the neck portion
11
of the braun tube of
FIG. 1
, and the overall outer structure of the braun tube can be simplified.
Particularly, the in-neck deflection yoke type braun tube can have the more improved deflection sensitivity on the comparison with the braun tube of
FIG. 1
as the deflection yoke
20
is installed outside of the funnel
10
, the reason will now be described.
In general, the deflection sensitivity of an electron beam can be described as power generated by currents and voltages applied to deflection coils performing deflection in the vertical and horizontal directions, it can be described as below.
P
H
=
1
2
L
H
I
H
2
(
1
)
P
V
=
1
2
R
V
I
V
2
(
2
)
Herein, P
H
and P
V
describe the horizontal deflection sensitivity and vertical deflection sensitivity, respectably, L
H
and R
V
describe the inductance of a horizontal deflection coil and the resistance a vertical deflection coil, respectively, and I
H
and I
V
describe currents applied to the horizontal deflection coil and vertical deflection coil, respectively.
With reference to the above-described equations 1 and 2, it is better to improve the deflection sensitivity of the braun tube with a small quantity of power, accordingly the more P
H
and P
V
lower in equations 1 and 2, the more the deflection sensitivity improves.
In a general braun tube, when a frequency of current applied in a horizontal direction is a high frequency not less than 15.75 kHz, an inductance value is a main adjustment factor, on the contrary when a frequency of current applied in a vertical direction is a low frequency as 60 Hz, a resistance value is a main adjustment factor.
Accordingly, in order to improve the deflection sensitivity of the braun tube, a L
H
value of the horizontal deflection coil and a R
V
value of the vertical deflection coil have to lower on the basis of the same current value.
Accordingly, in the in-neck deflection yoke type braun tube, because the deflection yoke
20
′ is installed inside the funnel
10
′, although the same amount of current is applied to the horizontal and vertical deflection coils
21
′,
23
′, the deflection force of an electron beam in up-and-down and right-and-left directions can improve by generating a bigger magnetic field inside the funnel
10
′.
In the in-neck deflection yoke type braun tube, because the deflection yoke
20
′ is installed inside the funnel
10
′, external physical influence can be minimized. However it is difficult to compensate the convergence and deflection sensitivity of an electron beam after the deflection yoke
20
′ is installed.
In addition, in the in-neck deflection yoke type braun tube, gas elements included in the ferrite core
25
′ of the deflection yoke
20
′ can leak inside the funnel
10
′ due to a high temperature circumstances in the fabrication process of the braun tube or operation of the braun tube, it may damage a characteristic of the braun tube which can show the sufficient performance in a vacuum state, accordingly lots of work are required in order to prevent it.
SUMMARY OF THE INVENTION
In order to solve above-mentioned problems, an object of the present invention is to provide a deflection yoke for a braun tube which is capable of compensating the convergence and deflection sensitivit
Kim Gyoo Hwan
Lim Jong Ho
Yang Woo Young
Fleshner & Kim LLP
LG Electronics Inc.
Tran Thuy Vinh
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