Electric lamp and discharge devices – Cathode ray tube – Shadow mask – support or shield
Reexamination Certificate
2001-04-11
2004-03-02
Patel, Vip (Department: 2879)
Electric lamp and discharge devices
Cathode ray tube
Shadow mask, support or shield
C313S404000, C313S405000
Reexamination Certificate
active
06700318
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a spring for supporting a support frame of a shadow mask in a color cathode ray tube and more particularly, to a spring for a color cathode ray tube that is capable of compensating for the displacement of a shadow mask according to a thermal expansion of the support frame for the shadow mask, thereby preventing mislanding of electron beams that may be caused from the displacement of the shadow mask.
2. Description of the Related Art
With the development of the technology for a cathode ray tube, recently, a large-sized color cathode ray tube becomes popular, which causes weight of a support frame for a shadow mask to be increased. However, this causes an amount of shock resistance, upon dropping, to be undesirably increased, such that an excessive shock may be applied to a spring that is adapted to connect a stud pin of a panel with the shadow mask and to the shadow mask. This results in the deviation of the support frame for the shadow mask and the deformation of the shadow mask. In addition, the shadow mask suffers a thermal expansion, which evokes the change in the landing of the electron beams. This results in the degradation of the color purity.
Therefore, there is a need for an effective buffering against the shock applied upon a dropping test and the thermal expansion of the shadow mask, for the purpose of reducing the amount of the shock resistance and preventing the degradation of the color purity.
FIG. 1
is a partly cut sectional view illustrating a general color cathode ray tube.
As shown, the general cathode ray tube includes: a panel
1
formed on the front surface of the cathode ray tube and provided with a luminous fluorescent material
2
of colors R, G and B on the inside thereof; a funnel
4
fused on the rear end of the panel
1
; a shadow mask
6
on which beam transmitting holes of a dot or slot shape are formed for separating the colors; a support frame
8
for supporting the shadow mask
6
, such that the shadow mask
6
is separated by a predetermined interval from the panel
1
; an earth magnetic shield
10
coupled to the support frame
8
; a spring
12
coupled to the support frame
8
, for buffering the shock applied to the shadow mask
6
due to a thermal expansion of the shadow mask; a stud pin
14
formed on the side wall
1
a
of the panel
1
, for coupling the spring
12
to the panel
1
; an electron gun
18
inserted into the neck of the funnel
4
, for emitting electron beams
16
to the luminous fluorescent material
2
; a deviation yoke
20
for adjusting the advancing orbits of the electron beams
16
, such that the electron beams
16
are scanned to the luminous fluorescent material
2
; and a reinforcing band
22
for preventing the width contraction caused from external shocks.
The spring
12
, as shown in
FIGS. 4
a
to
4
c
is comprised of: a stud pin coupling part
12
a
on which a hole ‘h’ adapted to be inserted and fixed into a stud pin
14
on the side wall
1
a
of the panel
1
is formed; a frame welding part
12
b
for coupling on the support frame
8
; and an inclined part
12
c
coupled to the stud pin coupling part
12
a
and the frame welding part
12
b
, while being inclined at a predetermined angle and having folded faces
12
d
and
12
e
inclined at a predetermined angle (&thgr;) on the coupled parts with the stud pin coupling part
12
a
and the frame welding part
12
b.
Under the above construction, the electron beams of the colors R, G and B emitted from the electron gun
8
inserted into the neck of the funnel
4
are adjusted in the orbits thereof by means of the deflection yoke
20
and then passed through the beam transmitting holes of the shadow mask
6
. Next, the electron beams are scanned horizontally and vertically in a sequential order to the luminous fluorescent material
2
of the colors R, G and B spread on the inside of the panel
1
to thereby emit the light from the luminous fluorescent material
2
. As a result, image is formed and displayed.
At this time, only about 30% of the electron beams
16
emitted from the electron gun
18
are passed through the beam transmitting holes of the shadow mask
6
and those of the remainder 70% are scanned to the part where no hole is formed on the shadow mask
6
.
A part of the electron beams
16
scanned on the shadow mask
6
is reflected. In this case, a part of the electron beams reflected is changed to shock energy and then absorbed on the shadow mask
6
. The absorbed energy enables the movement of the molecules in the interior of the shadow mask
6
to be activated, which induces the friction among the molecules. The friction generates heat from the shadow mask
6
.
As a consequence, the temperature of the shadow mask
6
rises and the volume thereof becomes expanded according to a thermal expansion coefficient of the material of the shadow mask
6
. The result is shown in FIG.
2
. As shown, the shadow mask
6
is expanded toward the luminous fluorescent material
2
relative to the direction of a tube shaft.
In the figure, a reference number ‘
6
’ represents a position where the shadow mask
6
before the thermal expansion is fixed and ‘
6
a
’ represents a position where the shadow mask
6
after the thermal expansion is moved.
Under the above state, the heat generated from the shadow mask
6
is conducted to the support frame
8
, whereby the temperature of the support frame
8
rises. This enables the support frame
8
to be thermally expanded. Hence, the support frame
8
is expanded toward the side wall
1
a
of the panel
1
and the shadow mask
6
expanded is moved to the direction opposite to the luminous fluorescent material
2
relative to the direction of the tube shaft.
If the volume of the support frame
8
is larger than that of the shadow mask
6
, however, the shadow mask
6
is excessively moved to the direction opposite to the luminous fluorescent material
2
relative to the direction of the tube shaft, which results in the mislanding of the shadow mask
6
. In this case, an amount of variation in the landing of the shadow mask
6
is &Dgr;LE, as shown in FIG.
3
.
In order to decrease the amount of variation in the landing &Dgr;LE, the support frame
8
has to be made of a material having a low thermal expansion coefficient. However, this causes the cost of the product to be undesirably high. As an alternative, hence, the spring
12
is designed in many ways in the structure thereof, such that the position of the shadow mask
6
is corrected to decrease the amount of variation in the landing &Dgr;LE.
FIG. 3
is an enlarged view of the part ‘a’ of FIG.
1
. As shown, the hole, which is formed on the end of the one side of the spring
12
, is inserted and coupled to the stud pin
14
formed on the center of the side wall
1
a
of the panel
1
, and the end of the other side of the spring
12
is welded and coupled to the rectangular type of support frame
8
. And, a skirt (which is not shown in the drawing) having an end portion folded along the periphery of the hole formation part (on which the beam transmitting holes of a dot or slot shape are formed, which is not shown in the drawing) of the shadow mask
6
is welded and fixed on the inner wall of the support frame
8
.
In
FIG. 3
, a reference numeral
16
a
represents the electron beams moved by a predetermined interval from the orbits of the electron beams
16
and
8
a
represents the support frame
8
moved by a predetermined interval from the position thereof before the thermal expansion.
On the other hand, the spring
12
having the inclined folded faces is varied according to the thermal expansion of the support frame
8
, such that the stage difference between the stud pin coupling part
12
a
, the frame welding part
12
b
and the inclined part
12
c
is generated.
FIG. 4
a
shows the spring
12
having the inclined folded faces at the state where the stud pin coupling part
12
a
, the frame welding part
12
b
and the inclined part
12
c
are disposed in parallel with each other in a
Fleshner & Kim LLP
Leurig Sharlene
Patel Vip
LandOfFree
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