Electric lamp and discharge devices – Cathode ray tube – Shadow mask – support or shield
Reexamination Certificate
1998-09-02
2001-04-03
Day, Michael H. (Department: 2879)
Electric lamp and discharge devices
Cathode ray tube
Shadow mask, support or shield
C313S406000, C313S407000
Reexamination Certificate
active
06211609
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a color cathode-ray tube (hereinafter referred to as “CRT”). More particularly, it relates to a design compensation volume setup of a corner spring for supporting a mask structure within a panel.
2. Discussion of Related Art
As shown in
FIG. 1
, a conventional CRT includes a panel
2
mounted in front thereof; a funnel
7
mounted at the back of the panel
2
in order to maintain a vacuum; a neck
10
extending from the back of the funnel
7
; an electron gun
8
within the neck
10
, for emitting R, G, and B electron beams; a phosphor screen
3
applied to the inner surface of the panel
2
, including phosphor layer for producing red, green, and blue lights in accordance with landing of electron beams; and a shadow mask structure
6
consisting of a rectangular shadow mask
4
where a plurality of electron beam apertures (not shown) are formed for color selection, and a frame
5
for fixing the shadow mask
4
.
The frame
5
is supported by a corner spring
11
connected to a stud pin
12
toward the panel
2
. As shown in
FIG. 2
, the corner spring
11
disclosed in U.S. Pat. No. 4,827,180 is constructed of a first arm
27
having a stud pin hole, and a second arm
29
connected to the frame
5
, the first and second arms being welded to each other. The two, respective arms make a specific angle (&thgr;
1
,&thgr;
2
) with a central axis
1
of welding portion.
Reference numeral
9
is indicative of a deflection yoke for deflecting the electron beams.
In the conventional CRT, the electron beams emitted from the electron gun
8
are deflected by the deflection yoke
9
, before passing through the apertures of the shadow mask
4
and scanning the phosphor screen, to thereby display an image.
The internal parts are located like a dotted line of
FIG. 3
prior to operation of the CRT, but move like a solid line when the temperature rises due to heat expansion.
The mask apertures formed on the shadow mask
4
move toward P′ from P, and the corner spring
11
serves to allow the mask apertures to move to a phosphorescent screen, heading for the position of Q.
That is, in this case, the V-shaped corner spring
11
is pressed to make the first and second arms
27
and
29
closer to each other. The second arm
29
is welded to the frame
5
, and &thgr;
1
and &thgr;
2
of
FIG. 2
is differently changed, in such a way that the position of the corner spring
11
is varied outside.
The color CRT has been developed in recent years, having the shadow mask made of the material of low coefficient of expansion such as Invar alloy, namely 36% nickel-iron alloy with coefficient of expansion of about 1.2×10
−6
/° C., and the mask frame made of iron.
The shadow mask made of Invar alloy with very low coefficient of expansion, does not expand with heat, and the mask frame expands around with heat during operation of the CRT.
The typical corner spring for compensating the mislanding by angle (&thgr;
1
,&thgr;
2
) of spring results in inaccurate electron beam landing. The reason why the electron beams land inaccurately is as follows.
When the temperature rises in the CRT the shadow mask does not efficiently expand with heat. The mask frame is made of iron with coefficient of expansion (about 1.2×10
−5
/° C. at room temperature) about ten times as high as 36% nickel-iron alloy. In this connection, the mask frame expands with heat.
Consequently, the corner spring allows the shadow mask move toward the screen. A passage that the electron beams pass through the mask apertures is altered, which causes the electron beams to inaccurately land on the phosphor element, thereby resulting in degradation of color purity.
SUMMARY OF THE INVENTION
Accordingly, the present invention is directed to a corner spring for color CRT that substantially obviates one or more of the problems, limitations, and disadvantages of the related art.
An objective of the present invention is to provide a corner spring whose movable piece's length L is optimized to prevent the mislanding caused by heat expansion, to thereby enhance the color purity of a CRT.
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 through practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure, particularly as detailed 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 length L of slope of a first arm is represented as 1.08S≦L≦1.75S to the distance S from a center of a stud pin coupling portion
113
to a frame contacting portion that is an end of a frame welding portion
123
of a second arm, and the distance H between a welding portion
103
where the first and second arms are welded to each other and the frame welding portion
123
of the second arm is expressed as H <0.668S.
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: 4652792 (1987-03-01), Tolita et al.
patent: 4827180 (1989-05-01), Sone et al.
patent: 5012154 (1991-04-01), Ragland, Jr.
patent: 5063325 (1991-11-01), Ragland, Jr.
patent: 5072151 (1991-12-01), Spina
patent: 5502349 (1996-03-01), Seo
patent: 5557162 (1996-09-01), Han
patent: 6037709 (2000-03-01), Nakagawa et al.
Day Michael H.
Gerike Matthew J.
LG Electronics Inc.
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