Shadow mask assembly

Details Shadow mask assembly Shadow mask assembly

2001-05-16

2004-04-27

Patel, Ashok (Department: 2879)

Electric lamp and discharge devices

Cathode ray tube

Shadow mask, support or shield

C313S402000

Reexamination Certificate

active

06727639

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an improved frame structure for fixing a shadow mask in a flat color CRT(Cathode Ray Tube).
2. Description of the Related Art
In general, the flat color CRT is an apparatus for scanning electron beams to phosphor dots applied on a screen according to image information.
As shown in
FIG. 1
, the electron beams are color selected while passing through a shadow mask
10
, which is formed of a thin film with a number of slots
11
and fixed at the rear of the screen by a frame structure.
The frame structure comprises main frames
20
a
directly welded to the shadow mask
10
, and sub-frames
30
for supporting the lower parts of the main frames
20
a
while tensioning the same.
To be specific, the upper part of each of the main frames
20
a
defines a section perpendicular to the shadow mask
10
and the lower part is bent inwardly about the shadow mask in a right angle with the end reaching the perpendicular section so that the cross sectional configuration in the x-axis direction defines a triangle.
The sub-frames
30
are shaped as a bar. The shadow mask is tensioned and fixed to the frame structure according to the following process.
After the sub-frames
30
are welded to both end lower parts of the main frames
20
a
, when the main frames are forced so that the shadow mask
10
having a small amount of volume can be placed on the main frames, the sub-frames
30
are bent.
After the shadow mask
10
is welded to the upper parts of the main frames
20
, when the force is released from the main frames
20
a
, the sub-frames
30
return to the original position while tensioning the shadow mask
10
.
However, since the upper parts of the main frame perpendicular sections are very narrow, it is not easy to weld the shadow mask to the upper parts of the main frames and thus productivity is lowered.
Also, the main frames have a small amount of stiffness, and are easily deformed in tensioning the shadow mask so that the shadow mask may not be tensioned with a uniform tensile force.
Therefore, a resistant force generated to the shadow mask corresponding to the tensile force is distributed different according to the position so that the shadow mask has a low vibration frequency in a middle portion and a high vibration frequency at both ends thereby having a wide range of amplitude.
In other words, in use of the CRT, vibration from a speaker is amplified in a cabinet for defining a front outer case of the CRT and amplified vibration is transferred to a panel side of the CRT, then to the main frames and the shadow mask through springs in the frame.
When vibration transferred to the shadow mask is identical with the vibration frequency of the shadow mask, resonance takes place and slots tremble to distort the incident direction of the electron beams so that howling takes place to create stripes on the screen and definition is degraded.
SUMMARY OF THE INVENTION
It is therefore an object of the invention to provide a flat color CRT in which a frame structure for supporting a shadow mask in a shadow mask assembly is modified to simplify a welding operation and howling of the shadow mask is reduced to reproduce clean definition.
According to an embodiment of the invention to obtain the object, it is provided a shadow mask assembly comprising: a shadow mask having an effective area with slots and a non-effective area without slots in the periphery; and a frame fixing body for tensioning the shadow mask; wherein the shortest distance t
M
from the outermost end of a main frame welded to the shadow mask to the interface between the effective area and the non-effective area and the width t
W
of the mask welding part formed at the upper part of the main frame have the relation of
0.14
≤
t
W
t
M
≤
1.0
.
It is preferred that the shadow mask is welded to the outermost end of the main frame in the effective area side direction in the range of t
W
/2 to t
W
.
It is more preferred that the main frame and the shadow mask are weld in the range of
0.30
≤
t
M
t
W
≤
0.99
.


REFERENCES:
patent: 3894321 (1975-07-01), Moore
patent: 4737681 (1988-04-01), Dietch et al.
patent: 4748371 (1988-05-01), Bauder
patent: 4857027 (1989-08-01), Makita et al.
patent: 5111106 (1992-05-01), Kaplan et al.
patent: 5406168 (1995-04-01), Takagi
patent: 5525859 (1996-06-01), Ito et al.
patent: 5644192 (1997-07-01), Ragland, Jr.
patent: 5672935 (1997-09-01), Ito et al.
patent: 6054803 (2000-04-01), Saita
patent: 6335594 (2002-01-01), Park
patent: 6388367 (2002-05-01), Taguchi
patent: 6479925 (2002-11-01), Kim

Affiliated with

Also associated with

Rating

Shadow mask assembly does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Shadow mask assembly, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Shadow mask assembly will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3190750