Electric lamp and discharge devices – Cathode ray tube – Plural beam generating or control
Reexamination Certificate
2000-05-18
2002-07-09
Day, Michael H. (Department: 2879)
Electric lamp and discharge devices
Cathode ray tube
Plural beam generating or control
C313S414000
Reexamination Certificate
active
06417610
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a color cathode ray tube, and particularly to a color cathode ray tube having precision main lens electrodes for an in-line type electron gun.
Color cathode ray tubes such as a color picture tube, a display tube, and the like are widely used as a receiver of TV broadcasting or as a monitor in an information processing apparatus for their high-definition image reproduction capability.
The color cathode ray tube of this kind includes a vacuum envelope comprised of at least a funnel having a faceplate carrying a phosphor screen on its inner surface at one end thereof, and a neck connected to the end of the funnel housing therein an electron gun structure for emitting electron beams toward the phosphor screen.
FIG. 15
is a schematic sectional view for explaining the configuration of a shadow mask type color cathode ray tube as one example of a color cathode ray tube to which the present invention is applied. Reference numeral
20
designates a faceplate,
21
a neck,
22
a funnel for connecting the faceplate to the neck,
23
a phosphor screen formed on the inner surface of the face plate to constitute an imaging screen,
24
a shadow mask which is a color selection electrode,
25
a mask frame for supporting the shadow mask to constitute a shadow mask structure,
26
an inner shield for shielding external magnetic fields,
27
a suspension spring mechanism for suspending the shadow mask structure on studs heat-sealed to the inner side wall,
28
an electron gun housed in the neck for emitting three electron beams Bs (×2) and Bc,
29
a deflection device for horizontally and vertically deflecting the electron beams,
30
a
magnetic device for carrying out a color purity adjustment and a centering adjustment,
31
a getter,
32
an internal conductive coating, and
33
an implosion protection band.
In the configuration shown in
FIG. 15
, the faceplate
20
, the neck
21
and the funnel
22
constitute a vacuum envelope. Three electron beams Bc and Bs×2 emitted in a line from the electron gun are horizontally and vertically deflected by magnetic fields formed by the deflection device
29
to scan the phosphor screen
23
two-dimensionally.
The three electron beams Bs, Bc×2 are respectively modulated by color signals of red (side beam Bs), green (center beam Bc) and blue (side beam Bs) and subjected to color selection in beam apertures in the shadow mask
24
disposed immediately in front of the phosphor screen
23
to impinge upon a red phosphor, a green phosphor and a blue phosphor of the mosaic three color phosphors of the phosphor screen
23
, thereby reproducing a desired color image.
FIG. 16
is a top view of main parts for explaining a structural example of an in-line type electron gun structure used for the color cathode ray tube shown in FIG.
15
. Reference numeral
10
designates a cathode,
11
a first grid electrode serving as a control electrode,
12
a second grid electrode,
13
a third grid electrode,
14
a fourth grid electrode,
15
a fifth grid electrode,
16
a sixth grid electrode,
16
a
a correction plate electrode in the sixth grid electrode
16
,
17
an anode,
17
a
a correction plate electrode in the anode,
18
a shield cup, and
19
insulating supports (only one of two is shown).
In the electron gun, three electron beams generated in a triode constituted by the cathode
10
, the first grid electrode
11
and the second grid electrode
12
are accelerated and preliminarily focused by the third grid electrode
13
, the fourth grid electrode
14
and the fifth grid electrode
15
, focused as desired by a main lens formed between the opposing surfaces of the sixth grid electrode and the anode
17
, and they are directed toward the phosphor screen as shown in FIG.
15
.
In the electron gun of this type, the fifth electrode
15
, the sixth electrode
16
and the anode
17
constituting the focus lens are cup-shaped. Particularly, each of the grid electrode
16
and the anode
17
constituting the final lens has a single opening surrounded by an in-turned rim on mutually facing ends thereof and has a correction plate electrode
16
a
,
17
a
therein set back from the mutually facing ends thereof which has an individual aperture therein for each of the electron beams, respectively.
FIGS. 17A and 17B
are schematic sectional views for explaining a main lens forming electrode of the aforementioned type electrode gun.
FIG. 17A
is a sectional view in parallel with the in-line direction of the three beams, and
FIG. 17B
is a sectional view perpendicular to the in-line direction.
In
FIGS. 17A and 17B
, the sixth grid electrode
16
has a single opening
16
-
1
in the end face of the sixth grid electrode
16
opposing the anode
17
, surrounded by a rim turned in an axial distance H toward the interior of the sixth grid electrode
16
, and has a correction plate electrode
16
a
having three beam apertures therein corresponding to the number of the electron beams and disposed at a position therein set back a distance d
1
from the single opening toward the interior of the sixth grid electrode, and similarly the anode
17
has a single opening
17
-
1
in the end face of the anode opposing the sixth grid electrode
16
across a spacing g, surrounded by a rim turned in an axial distance H toward the interior of the sixth electrode
16
, and has a correction plate electrode
17
a
having three beam apertures therein corresponding to the number of the electron beams end disposed at a position therein set back a distance d
2
from the single opening toward the interior of the anode. The correction plate electrode
17
a
has an opening for passing a center electron beam and forms passageways for side electron beams in cooperation with the inner wall of the cup-shaped anode
17
. A combination of the single openings
16
-
1
,
17
-
1
and the correction plate electrodes
16
a
,
17
a
produces an effectively large diameter electron lens. Japanese Patent Application Laid-Open No. 4-43532 Publication discloses an above-described effectively large diameter main lens formed by provision of oval rims in opposing end faces of a pair of electrodes in the main lens and correction plate electrodes set back from the respective opposing end faces toward the interiors of the respective electrodes.
FIGS. 18A
to
18
C are schematic sectional views for explaining the shapes of the electrodes for a main lens of the conventional electron gun. Generally, the inner wall of the cup-shaped electrode
16
(
17
) is formed to have an axially uniform inside diameter (in major and minor axis directions) from the open end A to the opposite end B formed with a rim as shown in FIG.
18
A. The opening end A sometimes becomes narrower than the opposite end B after manufacturing process such as drawing as shown in FIG.
18
B.
The outside diameters of the correction plate electrode are made substantially equal to the inside diameters of the cup-shaped electrode in major and minor axis lengths. Since the correction plate electrode
17
a
disposed within the anode
17
is semi-circular or semi-oval at both ends of its major axis, only top and bottom edges of the plate electrode in the minor axis direction are welded to the inner wall of the cup-shaped electrode.
When the correction plate electrode
16
a
(
17
a
) is inserted into the cup-shaped electrode
16
(
17
) and fixed by laser weld or the like to a position of a desired set back amount d from the electrode end face to manufacture the electrode as shown in
FIG. 18C
, if the inside diameter of the cup-shaped electrode is of the shape shown in
FIG. 18A
or
FIG. 18B
, it is very difficult to accurately position the correction plate electrode
16
a
(
17
a
) within the cup-shaped electrode (the sixth grid electrode
16
or the anode
17
). Thus, it is difficult to establish the dimension d or to secure the parallelism with respect to the single opening, resulting in deterioration of characteristics of the electron gun.
As described above, in the conventional elect
Moriwaki Satoshi
Sudo Akihito
Sugiyama Mitsuhiro
Antonelli Terry Stout & Kraus LLP
Day Michael H.
Hitachi , Ltd.
Williams Joseph
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