Shadow mask in flat cathode ray tube

Details Shadow mask in flat cathode ray tube Shadow mask in flat cathode ray tube

2000-10-11

2003-05-27

Kim, Robert H. (Department: 2882)

Electric lamp and discharge devices

Cathode ray tube

Shadow mask, support or shield

C313S402000, C313S403000

Reexamination Certificate

active

06570311

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a flat Braun tube, and more particularly, to a flat-tension shadow mask in a flat cathode ray tube.
2. Background of the Related Art
In general, the Braun tube(or a cathode ray tube) is employed in a TV or a display, and particularly, the flat Braun tube is used widely presently as the reduction of image distortion in the flat Braun tube improves a sense of vision, and the reduction of random reflection in the flat Braun tube reduces eye fatigue. A system and function of the related art flat Braun tube will be explained with reference to FIG.
1
.
Referring to
FIG. 1
, the related art flat Braun tube is provided with a flat panel
1
having fluorescent material
3
coated on an inside, and a funnel
5
of a bulb form welded to a rear surface of the panel with Frit glass, to form an inner space at a high vacuum of 10
−7
Torr. There is a rectangular rail
7
in the inner space of the panel
1
and the funnel
5
fitted on an inside surface of the panel
1
, to which a shadow mask
9
having fine perforation of slits or holes
11
for passing electron beams is fitted with a tension given thereto in advance. And, there is an electron gun
13
built in a bottle neck formed neck part
6
in rear of the funnel
5
for emission of electron beams(thermal electrons) as red, green, and blue three color picture signals are provided thereto, and a deflection yoke
15
outside of the neck part
6
for forming electro-magnetic fields in vertical and horizontal directions for deflection of the electron beams.
When a picture signal is provided to the cathodes(not shown) in the electron gun
13
of flat Braun tube, electron beams of red, green, and blue three colors are emitted toward the fluorescent material
3
coated on an effective area inside of the panel
1
. Most of the electron beams(approx. 85%) is blocked by bridges
14
of the shadow mask( or flat-tension mask)
9
as the electron beams pass through the shadow mask
9
on an electron beam path, while rest of the electron beams(approx. 15%) pass through the fine holes
11
in the shadow mask
9
and collide onto red, green, and blue fluorescent materials
3
to reproduce a color picture.
In the meantime, if an impact or interferential acoustic wave is provided to the Braun tube from outside, the shadow mask
9
will vibrates. In this instance, as shown in
FIGS. 2 and 3
, since a position of the fine hole
11
(hereafter called as “beam pass through hole”) in the shadow mask
9
is varied with a vibration frequency, the electron beams can not pass through the beam pass through hole
11
regularly, but blocked by no-hole regions
12
and the bridges
14
periodically, to cause so called howling in which the picture shakes. In order to suppress this, a damping wire, a vibration attenuating means, is closely fitted to one side of the shadow mask
9
. In this instance, the damping wire
8
is fitted across the no-hole region
12
between adjacent horizontal lines
11
a
and
11
b
of beam pass through holes in the shadow mask
9
, by welding both ends to brackets
17
on the rail
7
under tension. And, there are reference holes
16
on both ends of a damping wire fitting path in the no-hole region
12
as reference points for aligning the damping wire
8
on an exact position of the no-hole region
12
by making the damping wire
8
to pass through the reference holes
16
. However, keeping pace with the recent trend of requiring high definition TVs, an area for the damping wire
8
has been restricted as a pitch ‘P’ of the beam pass through holes
11
becomes gradually smaller, causing the damping wire
8
to move into an area of the beam pass through hole
11
even by a minute vibration of the shadow mask
9
, to display a shadow on a screen. And, there has been difficulty in fabrication in that burr formed in welding the rail
7
to the shadow mask
9
impedes fastening the damping wire
8
at an exact position by welding through the burr.
There is another method for fastening a plurality of damping wires
8
(
3
in general) each with approx. 60 &mgr;m diameter under tension on the shadow mask
9
for controlling vibration of the shadow mask. In this instance, as the damping wire
8
has a diameter which is too small to weld itself on a rail assembly
7
directly, the welding is conducted under a condition a bracket
17
and a plate
21
, both of which secure a welding area, are fitted on top and bottom of both ends of the damping wire
8
. In a state each of the brackets
17
of a damping assembly formed thus is placed on a recessed step surface
7
a of the rail assembly
7
, the damping assembly is fixed to a top surface of the rail assembly
7
.
However, in the related art damping wire, since the damping assembly has the bracket
17
, the plate
21
, and the damping wire
8
integrated as one unit, the damping assembly delays a Braun tube fabrication process and deteriorates an efficiency of the fabrication process as the damping assembly requires respective component fabrication processes, and a component integration process. Since the damping assembly is not closely fastened to the shadow mask effectively, the plurality of damping wires, in general
3
, required for obtaining a damping effect of a desired level increases a number of components, that pushes up a production cost. And, the damping wire
8
coming into the area of the beam pass through hole
11
of the shadow mask
9
caused by shaky damping assembly deteriorates a picture quality. Since debris, produced when unnecessary edges of the shadow mask is cut off after the shadow mask is welded to the rail assembly and remained on a fastening surface of the damping wire
8
, impedes close fastening of the damping wire
8
to the shadow mask
9
, the related art damping wire can not provide a desired vibration attenuation effect required for the shadow mask.
SUMMARY OF THE INVENTION
Accordingly, the present invention is directed to a shadow mask in a flat cathode ray tube that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
An object of the present invention is to provide a shadow mask in a flat cathode ray tube, in which a damping wire can be fastened.at a more exact position and a fastening force between shadow mask and the damping wire are strengthened.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, the shadow mask in a flat cathode ray tube having a damping wire located across a no-hole region between adjacent lines of beam pass through holes formed on a vertical line in the shadow mask for damping vibration of the shadow mask, includes means for limiting a position of the damping wire on the no-hole region of the shadow mask
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.


REFERENCES:
patent: 4308484 (1981-12-01), Carroll et al.
patent: 4562377 (1985-12-01), Kamohara et al.
patent: 5049778 (1991-09-01), Capek et al.
patent: 5363011 (1994-11-01), Fendley
patent: 5910702 (1999-06-01), Maehara
patent: 6111347 (2000-08-01), Kwak
patent: 11073889 (1999-03-01), None

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