Electric lamp and discharge devices – Cathode ray tube – Envelope
Reexamination Certificate
2000-08-14
2003-03-18
Patel, Ashok (Department: 2879)
Electric lamp and discharge devices
Cathode ray tube
Envelope
C313S47700R, C313S478000, C313S495000, C220S00210A, C220S00230A, C220S00210R
Reexamination Certificate
active
06534909
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a cathode ray tube, and more particularly, to an implosion protection band for a color cathode ray tube, which is fastened to an outer circumference of the cathode ray tube for enhancing implosion proof characteristics.
2. Background of the Related Art
Referring to
FIG. 1
, in general the color cathode ray tube is provided with a panel
1
having R, G, B fluorescent films
1
a
coated on an inside surface, a funnel
2
welded to a rear end of the panel for maintaining vacuum in an inside space thereof, an electron gun(not shown) sealed in a neck part
2
a
of the funnel for emitting electron beams
3
, a deflection yoke
4
for deflecting the electron beams emitted from the electron gun, and a shadow mask
5
for selection of a color of the electron beams deflected by the deflection yoke. The shadow mask
5
is supported on a support frame
6
, so as to have a gap to the fluorescent film
1
a
. In order to make the electron beams
3
emitted from the electron gun to hit a target on the fluorescent film
1
a
exactly, an inside space of the cathode ray tube should be maintained to be a high vacuum. Accordingly, an evacuation step is carried out, in which air inside of the cathode ray tube is evacuated while the electron gun is inserted into the neck park
2
a
. However, as shown in
FIG. 2
, upon completion of the evacuation step, the panel
1
has substantial amounts of tension and compression exerted thereto. That is, the cathode ray tube is susceptible to implosion even if a slight impact is applied thereto. Therefore, in order to prevent this, an implosion protection band
11
is strapped around a skirt portion of the panel
1
before the evacuation.
FIGS. 3A and 3B
illustrate stress simulations of a panel
1
of a cathode ray tube under a high vacuum, wherein portions with high stresses are sensitive to impacts and have high probabilities of implosions.
In general, the implosion protection band
11
is strapped by a method as shown in FIG.
4
.
First, an implosion protection band
11
having an inner circumference slightly shorter than an outer circumference of the panel
1
is provided.
Second, the implosion protection band is heated until the inner circumference of the implosion protection band
11
becomes longer than the outer circumference of the panel
1
.
Third, the implosion protection band is inserted in the outer circumference of the panel
1
and the implosion protection band is cooled down, to complete the strapping.
At the end, the uniform compression of the four comers by the implosion protection band
11
disperses the stresses distributed in a screen portion of the panel
1
during the vacuum. As alternatives to the implosion protection band, the panel
1
may be heat treated to strengthen the panel
1
physically, or a film is attached on a surface of the panel. A position of the implosion protection band strapping on the skirt portion of the Panel
1
differs depending on a shape of the panel
1
. As shown in
FIG. 5
, a parameter influencing to the strapping position of the implosion protection band
1
is an “wedge ratio=S/t”, a ratio of a corner thickness ‘S’ of the panel
1
to a center thickness ‘t’ of the panel
1
in an effective surface thereof. The wedge ratio, dependent on an inner surface curvature and an outer surface curvature as well as the center thickness‘t’ of the panel
1
, is in general 2.0. Recently, as screen of the cathode ray tube is large sized and flatter, it has been a trend that the wedge ratio becomes smaller. The smaller wedge ratio implies that thickness of the comer of the Panel
1
becomes the thinner by the much, which implies that the panel
1
is susceptible to implosion even by a small impact. That is, as described, the smaller wedge ratio means a weaker comer portions, a wrong position determination under which state may lead the implosion protection band strapping, not to prevent the implosion, but to an opposite effect.
SUMMARY OF THE INVENTION
Accordingly, the present invention is directed to an implosion protection band for color 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 an implosion protection band for color cathode ray tube, in which a strapping position of an implosion protection band is improved for enhancing an implosion proof characteristics of a flat panel.
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 implosion protection band for color cathode ray tube includes a panel with a wedge ratio of 1.1~1.8 and a substantially flat outer surface, wherein the implosion protection band is strapped around an outer circumference of the panel to satisfy a condition of 0.2≦UW/LW≦0.5, where the UW denotes an upper band width and the LW denotes a lower band width with reference to an extension line from an inside surface of the panel at a center thereof.
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: 4720657 (1988-01-01), Tischer
patent: 4930015 (1990-05-01), Dougherty et al.
patent: 4990825 (1991-02-01), Tsukui et al.
patent: 5241394 (1993-08-01), Mutso et al.
patent: 5606377 (1997-02-01), Swank
Fleshner & Kim LLP
LG Electronics Inc.
Patel Ashok
Roy Sikha
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