Electric lamp and discharge devices – Cathode ray tube – Envelope
Reexamination Certificate
2000-05-17
2002-12-31
Patel, Nimeshkumar D. (Department: 2879)
Electric lamp and discharge devices
Cathode ray tube
Envelope
C313S4770HC, C313S479000, C348S822000
Reexamination Certificate
active
06501215
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a shrinkage band for a CRT, and more particularly, to a shrinkage band combined to a CRT adopting a panel with a flat outer surface and a curved inner surface recently emerging as a new trend, which is capable of preventing occurrence of a explosion phenomenon on the panel.
2. Description of the Background Art
As is widely known, a CRT is a display instrument used for an observation of an oscilloscope or a radar as well as a television set.
The CRT serves to transmit a color image for users' viewing which is reproduced in a manner that a phosphor screen consisting of fluorescein pixels, that is, an electrooptic device, converting a video data received as an electric signal to a visual information, graphite, that is, an optical absorption substance, and an aluminum film improving a luminance, is hit by an electronic beam.
FIG. 1
illustrates a construction of a general CRT in accordance with a conventional art.
As shown in the drawing, the conventional CRT includes a panel
1
positioned in the front surface and a funnel
2
adhesively attached to the rear end of the panel
1
, forming a vacuum outer casing container.
An electric gun
5
radiating an electric beam
4
is hermetically sealed inside a neck portion
3
, that is, the end portion having relatively smaller diameter in the funnel
2
. A deflection yoke
9
for generating a pin-cushion-type horizontal deflection magnetic field and barrel-type vertical deflection magnetic field, is mounted in the outer circumferential side in the vicinity of the neck portion
3
, so as to deflect the radiated electronic beam to the whole screen.
A phosphor film
6
is formed on the inner surface of the panel
1
, and a shadow mask
7
having a section-based electrode function is supported by a frame
8
installed therein, spaced apart at a predetermined distance from the phosphor film
6
.
In the conventional CRT constructed as described above, the electronic beam
4
radiated from the electronic gun
5
is deflected to a desired portion of a screen by the vertical and horizontal deflection magnetic fields of the deflection yoke
9
, and as the electronic beam passes through a plurality of through holes (not shown) formed at the shadow mask
7
, it hits the phosphor film
6
, thereby creating a picture.
Since the inside of the conventional CRT constructed as above makes a vacuum state by the panel
1
and the funnel
2
, a stress is applied to the panel due to an external atmosphere pressure. That is, as shown in
FIG. 2
, according to the structural characteristics of the CRT, the front surface portion of the panel
1
receives a compressive stress while the side portion thereof receives a tension stress.
Thus, in a state that the compressive stress and the tension stress work due to the vacuum, when an external impact is applied to the CRT, a explosion phenomenon possibly causing that the panel
1
or the funnel
2
is exploded may occur, which, thus, causes a malfunction to the CRT as well as threatening users' safety.
In order to prevent such a explosion phenomenon, a shrinkage band
10
is typically combined to continuously cover the external side portion of the panel
1
.
The panel
1
is formed of a glass, which is weaker over the tension stress compared to the compressive stress in its property, and accordingly, the side portion of the panel
1
is structurally weaker compared to the front surface portion thereof.
Therefore, the shrinkage band
10
is combined to the CRT so as to strengthen the rigidity of the side portion of the panel
1
where the tension stress is concentrated, to thereby prevent the explosion phenomenon.
In detail, when an impact is applied to the surface of the CRT, a deformation stress, that is, a tension stress, expanding the side portion of the CRT is generated, which is, however, restrained by the rigidity of the shrinkage band
10
that compresses the side portion, so that a crack possibly caused passing the side portion and the surface portion can be restrained or the speed of the crack can be lowered down. And, at the same time, the direction of the main stress to the surface portion of the panel
1
and the proceeding direction of the crack are changed, thereby preventing the explosion phenomenon.
According to a research, the maximum tension stress working on the side portion of the panel
1
was observed by 87.9 kgf/cm
2
without the shrinkage band
10
, while when the shrinkage band is combined to the side portion of the panel
1
, the maximum tension stress was observed by 79.0 kgf/cm
2
.
The panel
1
is typically fabricated by molding. When the panel is fabricated by molding, a mold match line is formed in the panel
1
, and the shrinkage band
10
is generally combined to the CRT in a manner that it covers the mold match line
11
, as shown in
FIGS. 3A-3B
.
Referring to kinds of the shrinkage bands, there are a straight line-type shrinkage band
10
′ which is directed to highly improve an adherence of the shrinkage band itself for heightening the compression efficiency as shown in
FIG. 3A and a
fold-type shrinkage band
10
″ directed to strengthening a compression force in the front portion of the panel
1
as shown in FIG.
3
B.
Theoretically, though it is desired to install the shrinkage band
10
″ on the basis of the center of the curved portion of the corner portion, making a break-even point of the compression efficiency, of the inner surface of the panel
1
, since the mold match line
11
and the position of the center of the curved portion of the corner are almost the same owing to the spherical panel form, substantially the mold match line
11
is easily identified in view of form is used as an installment reference to the shrinkage band
10
.
In detail, since, on the basis of the mold match line
11
, the upper portion of the shrinkage band
10
compresses the front portion of the panel
1
and the lower portion of the shrinkage band
10
compresses a skirt portion of the panel
1
, the shrinkage band
10
is to be positioned suitably on the basis of the mold match line
11
in order to improve a explosion prevention capacity.
For example, if the shrinkage band
10
is inclined toward the lower portion (the skirt portion of the panel
1
) of the mold match line
11
, many cracks can be made in the CRT due to an external impact, or in a worse case, the panel
1
may be separated from the CRT.
Reversely, if the shrinkage band
10
is inclined toward the upper portion (the front portion of the panel
1
) of the mold match line
11
, a explosion or a crack can be easily made in the skirt portion of the panel
1
due to an external impact.
Actually, when the shrinkage band
10
is combined to the CRT, in order to accomplish optimum explosion-proof characteristics, the mold match line
11
is typically designed in a manner that the compression force of the upper portion is weak compared to that of the lower portion. Taking an example that the spherical panel as in the conventional art is adopted to the CRT, it is designed in a manner that the compression force of the upper portion of the mold match line
11
does not go beyond 90% compared to the compression force of the lower portion.
As another way of preventing the explosion, besides the shrinkage band
10
, a strong glass having an improved explosion prevention characteristics by heightening its rigidity may be used for the panel
1
, or a film may be attached onto the surface of the panel
1
so as to provide a explosion prevention function.
Meanwhile, recently, as a screen is turning large-sized and flat in order to provide a distinct image, there has been proposed a panel (termed as a ‘flat panel’, hereinafter) of which an outer surface is flat while inner surface is curved. This kind of panel offers a distinct image compared to the general spherical panel as used in conventional arts, implementing a highly-refined picture, but the corner portion of the panel is formed thick compared to that of the general spherical
Fleshner & Kim LLP
LG Electronics Inc.
Patel Nimeshkumar D.
Zimmerman Glenn
LandOfFree
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