Electric lamp and discharge devices – Cathode ray tube – Ray generating or control
Reexamination Certificate
2002-02-22
2003-09-16
O'Shea, Sandra (Department: 2875)
Electric lamp and discharge devices
Cathode ray tube
Ray generating or control
C313S269000, C313S440000
Reexamination Certificate
active
06621204
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a color cathode ray tube which displays a color image, and more particularly to a color cathode ray tube having a deflection unit of an improved structure.
2. Description of the Related Art
A color cathode ray tube which is used as a color television picture tube, a monitor tube of an information equipment or the like is constituted of a vacuum envelope which is formed by connecting a panel portion having a phosphor screen (also simply referred to as “screen”) on an inner surface thereof and a neck portion which accommodates an electron gun for irradiating electron beams by means of a funnel portion.
In the color cathode ray tube having such a vacuum envelope, to obtain the best convergence under the favorable focusing characteristic over the whole region of a phosphor screen which constitutes a display screen thereby obtaining the high resolution without color irregularities, a magnet assembly which is constituted of magnets having a plurality of magnetic poles is arranged on an outer surface of the neck portion which accommodates the electron gun and the loci of electric beams are corrected by the magnetic field.
Further, the color cathode ray tube includes horizontal and vertical deflection coils for performing the deflection scanning of electron beams irradiated from the electron gun in the horizontal direction as well as in the vertical direction. Further, the color cathode ray tube exteriorly mounts a deflection unit which includes a rotation correction coil which corrects the rotation of an image (raster) on the screen and a magnetic current modulator (MCM) which corrects raster distortions, that is, a so-called inner pin at a central region of the screen on a boundary between the neck portion and the funnel portion.
FIG. 8
is a side cross-sectional view for schematically explaining a structural example of a color cathode ray tube which mounts a deflection unit on a color cathode ray tube. The color cathode ray tube is formed of a vacuum envelope which is constituted of a panel portion
1
having a phosphor screen
4
, a neck portion
2
and a funnel portion (also referred to as “cone portion”)
3
which contiguously connects the panel portion
1
and the neck portion
2
. The color cathode ray tube is also configured such that a deflection unit
15
which includes a deflection yoke
16
is exteriorly mounted over a transitional region from the neck portion
2
to the funnel portion
3
.
An electron gun
11
which irradiates three electron beams B are housed in the inside of the neck portion
2
, the phosphor screen
4
which is formed on an inner surface of the panel portion
1
includes three-colored phosphors coated thereon in a mosaic form, and a shadow mask structural body
5
which constitutes a color selection electrode is arranged in the vicinity of the phosphor screen
4
.
The shadow mask structural body
5
includes a support frame
7
which holds a shadow mask
6
and is held by engaging suspension springs
8
with stud pins
9
which are mounted in an erected manner on an inner wall of a skirt portion of the panel portion
1
. Further, a magnetic shield
10
which shields an external magnetic field is mounted on an electron-gun side of the shadow mask structural body
5
Here, an implosion prevention band
14
is fastened to an outer-side wall of the panel portion
1
.
FIG. 9
is enlarged side view of the deflection unit
15
which is exteriorly mounted on the color cathode ray tube. An arrow P side of the deflection yoke
16
incorporated into the deflection unit
15
is a large-diameter portion which constitutes a phosphor screen side and an arrow G side is a small-diameter portion which constitutes an electron-gun side and exhibits an approximately funnel shape. A horizontal deflection coil is disposed in the inside of the deflection yoke
16
and the vertical deflection coil is disposed in the outside of the deflection yoke
16
by way of a separator. Further, a core made of ferrite or the like is disposed in the outside of the vertical deflection coil.
Further, a rotation correction coil
17
is mounted on the large-diameter-portion-side end portion of the deflection yoke
16
, while a magnet assembly
12
which is formed by combining magnets of 4 poles or 6 poles is mounted on the small-diameter-portion side of the deflection yoke
16
.
An upper protective cover
19
which houses a convergence adjusting circuit board
18
is provided to a top portion (upper side in
FIG. 9
) of the deflection unit
16
, while a lower protective cover
21
which houses a circuit board on which a magnetic current modulator (MCM)
20
is mounted is provided to a bottom portion (lower side in
FIG. 9
) of the deflection unit
Further, a fixing band
22
is provided to the small-diameter-portion side of the deflection yoke
16
which constitutes the electron-gun side and the fixing band
22
is fixedly secured to the neck portion
2
by fastening. The whole deflection unit
15
is tilted using the fixing point as a fulcrum to adjust the deflection unit
15
to the best position and, thereafter, the deflection unit
16
is mounted on a portion ranging from the funnel portion
3
to the neck portion
2
by inserting a plurality of wedges between the large-diameter-portion side and the funnel portion
3
.
Here, in
FIG. 9
, numeral
23
indicates a power supply line for supplying electricity to the rotation correction coil
17
and numeral
24
indicates a power supply line for supplying electricity to deflection coils.
FIG. 10
is a plan view for explaining a constitutional example of the magnetic current modulator
20
. The magnetic current modulator
20
is served for correcting the pin distortions at a central region of a screen of the cathode ray tube and is constituted of modulation coils which are respectively inserted into a vertical deflection coil and a horizontal deflection coil in series and a bias magnet.
In
FIG. 10
, numeral
202
indicates a vertical modulation coil and numerals
203
and
204
indicate horizontal modulation coils. A structure in which the horizontal modulation coils
203
and
204
are arranged at both sides of the vertical modulation coil
202
and these modulation coils
203
,
204
are sandwiched by bias magnets
205
,
206
from both sides is housed in the inside of a resin casing
201
and is mounted on a printed circuit board which will be explained later. Here, respective coils are wound around magnetic cores and an adhesive agent
208
is coated over each portion defined between cores of the neighboring coils and bias magnets
205
,
206
which are arranged close to the cores so as to fix them together.
FIG. 11
is a developed view for explaining the arrangement of the coils and bias magnets of the magnetic current modulator. The vertical modulation coil
202
is constituted of a vertical modulation coil
202
b
which is wound around one vertical core
202
a
and the horizontal modulation coils
203
,
204
are constituted of horizontal modulation coils
203
b
,
203
d
,
204
b
,
204
d
which are respectively wound around respective pairs of horizontal cores
203
a
,
203
c
,
204
a
,
204
c
which are arranged in parallel.
At both ends in the winding axis direction of the vertical modulation coil
202
, the winding axis directions of the horizontal modulation coils
203
,
204
are arranged in parallel and the bias magnets
205
,
206
are arranged at the outermost side of the horizontal modulation coils
203
,
204
.
The winding axis directions of the vertical modulation coil
202
and respective horizontal modulation coils
203
,
204
are set to directions which generate magnetic fields indicated by arrows in the drawing and these modulation coils are inserted between the vertical deflection coil and the horizontal deflection coil in series so as to correct the inner pin distortions of the raster on the screen.
FIG. 12
is a plan view for explaining a mounting state of the magnetic current modulator
20
on a printed circuit board
207
. The ma
Honma Kouichi
Kakesu Takateru
Koganezawa Nobuyuki
Hitachi , Ltd.
Krishnan Sumati
Milbank Tweed Hadley & McCloy LLP
O'Shea Sandra
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