Shadow mask/frame assembly for color cathode ray tube

Details Shadow mask/frame assembly for color cathode ray tube Shadow mask/frame assembly for color cathode ray tube

2000-05-30

2002-07-09

Kim, Robert H. (Department: 2882)

Electric lamp and discharge devices

Cathode ray tube

Shadow mask, support or shield

C312S402000

Reexamination Certificate

active

06417608

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a shadow mask/frame assembly for a color cathode ray tube (CRT), and more particularly, to a shadow mask/frame assembly for a color cathode ray tube in which a frame installed at a panel is improved.
2. Description of the Related Art
FIGS. 1 and 2
are a sectional view of a typical color CRT and an exploded perspective view showing a shadow mask frame assembly for a color CRT installed at the color CRT, respectively. Referring to the drawings, a typical color CRT includes a panel
11
on an inner surface of which a fluorescent film
11
a
is formed, and a funnel
30
coupled to the panel
11
. An electron gun
15
is installed at a neck portion
14
of the funnel
30
and a deflection yoke
20
is installed at a cone portion
12
of the funnel
30
.
Also, the typical color CRT has a shadow mask frame
10
. The shadow mask frame
10
includes a shadow mask
16
installed to be separated a predetermined distance from the fluorescent film
11
a, a frame
17
supporting the shadow mask
16
, and an inner shield
21
of a rectangular funnel shape which is coupled to the frame
17
. A skirt portion
17
a
for supporting the shadow mask
16
by being welded thereto is formed at the frame
17
. A flange portion
17
b
bent toward the inner side is extended from the skirt portion
17
a
so that the flange portion
17
b
is coupled to the inner shield
21
.
The shadow mask
16
includes a hole portion
16
c
having a plurality of electron beam passing holes, a hole-free portion
16
b
extending from the edge of the hole portion
16
c
, and a bending portion
16
a
extending downward at a right angle from the hole-free portion
16
b
and fixed to the skirt portion
17
a.
A hook spring
19
fixed to the outer surface of the frame
17
is coupled to a stud
18
installed on the inner surface of the panel
11
and the shadow mask frame assembly
10
is installed at the inner surface of the panel
11
.
The weight of the frame
17
increases as the size of the color CRT increases. Typically, a panel member having a thickness of about 1.2 mm is used for the color CRT less than 14 inches whereas a thin panel having a thickness of about 0.8 mm is used for a color CRT about 14-29 inches to reduce the weight thereof. When these thin panels are used, the support force of the frame
17
to the shadow mask
16
decreases so that the shadow mask
16
is deformed when an external impact is applied or during the manufacturing process.
Also, an electron beam emitted from the electron gun is selectively deflected by the deflection yoke
20
and passes through the holes of the shadow mask
16
for color selection, and excites the fluorescent film
11
a
. Here, the electron beam input to the edge of the shadow mask
16
is reflected on the flange portion
17
b
, generating diffusion-reflection. Furthermore, although not shown in the drawings, the diffused electron beam passes through the electron beam passing hole of the shadow mask
16
and excites an undesired pixel. To solve the above problems, a method of bending an end portion of the flange portion
17
b
at a predetermined angle toward the shadow mask
16
has been suggested. However, the sufficient structural strength of the frame
17
and sufficient prevention of the diffusion-reflection cannot be expected.
SUMMARY OF THE INVENTION
To solve the above problems, it is an objective of the present invention to provide a shadow mask/frame assembly having an improved frame structure so that the shadow mask can be prevented from being deformed by an external impact and the diffusion-reflection can be prevented.
Accordingly, to achieve the above objective, there is provided a shadow mask/frame assembly for a color CRT which comprises a shadow mask including a hole portion having a predetermined curvature where a plurality of electron beam passing holes are formed and a bending portion extending from the edge of the hole portion by being bent at a predetermined angle, and a frame including a skirt portion coupled to the bending portion of the shadow mask, a flange portion extending from the skirt portion by being bent at a right angle thereto, a connection portion extending downward from the flange portion, and an extension portion extending from the connection portion, parallel to the flange portion.
It is preferable in the present invention that an end portion of the extension portion has a knife edge shape for allowing an electron beam colliding with the extension portion to be diffusely reflected to the area except for the hole portion.


REFERENCES:
patent: 4737681 (1988-04-01), Dietch et al.
patent: RE33253 (1990-07-01), Strauss
patent: 4994712 (1991-02-01), Strauss

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