Electric lamp and discharge devices – Cathode ray tube – Beam deflecting means
Reexamination Certificate
2000-04-14
2003-01-14
Patel, Vip (Department: 2879)
Electric lamp and discharge devices
Cathode ray tube
Beam deflecting means
C313S47700R
Reexamination Certificate
active
06507144
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a cathode ray tube such as a color picture tube and a color monitor, and in particular to an improved cathode ray tube which can prevent an interference from taking place to an electron beam deflection trajectory, by sufficiently obtaining the atmospheric pressure resistance of a vacuum vessel, and margin of a beam shadow neck BSN which causes a problem when adjusting a deflection yoke.
2. Description of the Background Art
FIGS. 1 and 2
illustrate an example of a conventional cathode ray tube, respectively.
FIG. 1
is a side-sectional view illustrating a color picture tube, and
FIG. 2
is a front view illustrating a fluorescent screen provided in a panel.
As shown therein, the cathode ray tube which has been generally known as a Braun tube includes a vacuum vessel
10
having: a glass panel
3
consisting of an image receiving unit
1
similar to a rectangle having a tube axis Z, a horizontal axis X and a vertical axis Y, and a skirt portion
2
provided around the image receiving unit
1
; a glass funnel
4
firmly connected to the skirt portion
2
, for maintaining a vacuum state in the cathode ray tube; and a cylindrical glass neck
7
connected to an end portion of the glass funnel
4
having a smaller diameter.
A fluorescent screen
5
having dot- or stripe-shaped fluorescent layers of three colors, blue, green and red is disposed at the panel
3
.
An electron gun
9
emitting three electron beams
8
is provided in the neck
7
. The electron gun
9
is an in-line type electron gun emitting the three electron beams
8
arranged in a line on an identical horizontal surface.
In addition, a yoke mounting portion
11
is disposed at a predetermined portion between the neck
7
and funnel
4
of the vacuum vessel
10
. A deflection yoke
6
deflecting the electron beam
8
emitted from the electron gun
9
to the whole screen is mounted on the yoke mounting portion
11
, thereby generating a pincushion type horizontal deflection magnetic field and a barrel type vertical deflection magnetic field.
The electron beam
8
emitted from the electron gun
9
is deflected in a horizontal deflection direction X and a vertical deflection direction Y generated by the deflection yoke
6
. Accordingly, when reaching to the fluorescent screen
5
through a shadow mask (not shown) distinguishing colors, the three electron beams arranged in a line are concentrated on the whole fluorescent screen
5
without requiring a specific compensating device, and color images are displayed by horizontal and vertical scanning.
The above-described color picture tube is a line type color picture tube of self convergence, and widely practically used.
It is very important to reduce consumption power of the deflection yoke
6
which is a maximum power consumption source in the cathode ray tube such as the color picture tube.
That is to say, it is necessary to increase an anode voltage which finally accelerates the electron beam in order to improve screen luminance, and it is also necessary to increase a deflection frequency so as to correspond to office automation OA apparatuses including a high definition television HDTV and a personal computer PC, which increases deflection power, namely the consumption power of the deflection yoke
6
.
Especially when the electron beam is deflected by a high frequency, the deflection magnetic field may be easily externally leaked from the cathode ray tube. Accordingly, restrictions are enhanced in regard to the leakage magnetic field of the cathode ray tube, namely the OA apparatuses such as the personal computer.
In the deflection yoke
6
, a method of using a compensating coil as a means for reducing the magnetic field leaked from the cathode ray tube has been generally employed.
However, to use the compensating coil increases the consumption power of the personal computer.
In general, when reducing the deflection power or leakage magnetic field, it is preferable to efficiently operate the deflection magnetic field in regard to the electron beams, by decreasing a diameter of the neck
7
of the cathode ray tube, an outer diameter of the yoke mounting portion
11
on which the deflection yoke
6
is mounted, and an operational space of the deflection magnetic field.
In the above-described cathode ray tube, in case the electron beam
8
is deflected in a direction of a maximum diameter of the screen, namely a diagonal direction, a deflection angle of the electron beam, namely an angle between the tube axis Z and the deflected electron beam
8
is increased.
When the deflection angle of the electron beam
8
is increased, the electron beam
8
passes near the yoke mounting portion
11
of the funnel on which the deflection yoke
6
is mounted.
Accordingly, when the diameter of the neck
7
or the outer diameter of the yoke mounting portion
11
of the funnel
4
is simply decreased, as illustrated in
FIG. 1
, the outer-side electron beam
8
collides with an inner wall P
1
near the neck
7
of the funnel
4
. In addition, as illustrated in
FIG. 2
, a region of the fluorescent screen
5
where the electron beam
8
does not reach, namely a non-luminescence portion P
2
is generated.
Therefore, in the conventional cathode ray tube, it is impossible to simply decrease the diameter of the neck
7
or the outer diameter of the yoke mounting portion
11
of the funnel
4
. As a result, it is difficult to reduce the deflection power or leakage magnetic filed.
In order to overcome the above-described disadvantage, it is disclosed in Japanese Patent Application 48-34349 a vacuum vessel
20
of the cathode ray tube having a different shape as depicted in
FIGS. 3
to
5
, based on the fact that a passing region defined according to a trajectory of the electron beam
8
passing the yoke mounting portion
11
near the neck
7
of the funnel
4
forms a shape similar to a rectangle, in the case of drawing a rectangular raster on the fluorescent screen
5
.
In the vacuum vessel
20
, as shown in
FIGS. 4A
to
4
E taken along lines B—B to F—F, respectively, the sectional shape from the neck
7
of the funnel
4
where the deflection yoke
6
is mounted to the funnel
4
is varied from a round shape to a shape similar to the rectangle via an elliptical shape.
As compared with the vacuum vessel of the cathode ray tube having the round-shaped yoke mounting portion
11
near the neck
7
of the funnel
4
, the vacuum vessel
20
has a shape similar to the rectangle.
Accordingly, the horizontal deflection coil and the vertical deflection coil of the deflection yoke are positioned at the passing region of the electron beam
8
, and thus the electron beam
8
is efficiently deflected, thereby reducing the deflection power.
However, in the conventional vacuum vessel
20
, the sectional shape of the side of the neck
7
of the funnel
4
where the deflection yoke
6
is mounted, namely the sectional shape of the yoke mounting portion
11
forms a shape similar to the rectangle, and accordingly the strength of the inside air pressure is decreased, thereby reducing stability. Thus, it is difficult to sufficiently reduce the deflection power.
On the other hand, in general, the more the deflection angle of the electron beam
8
is increased, the more a length of a tube of the cathode ray tube, namely a length of the whole neck
7
is shortened.
For instance, a deflection tube of 110° has been developed by utilizing enlarged angle deflection. However, in the case that the enlarged angle deflection is simply performed, the deflection angle of a diagonal portion is increased, thereby causing a beam shadow neck BSN.
According to Japanese Patent Application 58-225545, the beam shadow neck BSN is overcome by providing a groove at the diagonal portion in a cone-shaped portion of the funnel.
As described above, in the conventional cathode ray tube, the deflection yoke is designed according to the funnel. However, in a pyramid-shaped funnel and deflection yoke structure, when designing the side of the neck of the fun
Berck Ken A
Birch & Stewart Kolasch & Birch, LLP
LG Electronics Inc.
Patel Vip
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