FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION (See section 10, rule 13)
"MASK ASSEMBLY FOR CATHODE RAY TUBE (CRT)"
SAMSUNG SDI CO., LTD., a company of Republic of Korea, of 575, Shin-dong, Yeongtong-gu, Suwon-si, Gyeonggi-do, Republic of Korea,
The following specification particularly describes the invention and the manner in which it is to be performed.

-MASK ASSEMBLY FOR CATHODE RAY TUBE (CRT)
BACKGROUND OF THE INVENTION
Field of the Invention
5 [0001] The present invention relates to a mask assembly for a Cathode Ray
Tube (CRT), and more particularly, to a mask assembly for a CRT which can minimize the transference of vibration through a frame.
Description of the Related Art
10 [0002] Generally, a Cathode Ray Tube (CRT) is an electronic tube where
electron beams emitted from an electron gun are deflected due to a magnetic deflection field, pass through a color selection shadow mask, and then strike and excite green, blue, and red phosphors on a phosphor film within a panel, thereby displaying desired images.
15 [0003] In the CRT, the mask assembly comprises a shadow mask and a frame
which is the supporting body of the shadow mask.
[0004] The shadow mask is formed such a way that a plurality of beam passage holes are formed on a metal plate through a photolithography process, and the circumference of the frame is bent through a pressing process. The
20 frame is fixed to the circumference of the shadow mask through a method such as
welding.
[0005] A plurality of spring members are attached on the outer circumference portion of the frame, and the mask assembly is built in a CRT in such a way that the spring members are inserted into a stud pin fixed in a panel.
25 [0006] The shadow mask has a color selection function of selecting the
emitted electron beams and landing them on the phosphor film.
[0007] For this purpose, it is important that the beam passage holes maintain a predetermined pattern to guarantee high image quality.
[0008] Since the shadow mask is very thin and weak, transference of the
30 vibration to the shadow mask should be minimized when shocks or vibrations due
to the sound pressure of speakers are applied to the shadow mask.
[0009] To prevent the transference of the vibration, the thickness of the frame can be increased. But in this case, the weight of the mask assembly will be also increased, so another method to improve the strength while not increasing the
2

weight of the frame is needed.
SUMMARY OF THE INVENTION
[0010] It is an object of the present invention to provide a mask assembly for a
5 Cathode Ray Tube (CRT) that can improve strength and vibration absorbing ability
of the frame by reforming the structure of the frame.
[0011] This and other objects can be achieved by a mask assembly for a CRT
with the following features.
[0012] A mask assembly for a CRT according to the exemplary embodiment of
10 the invention can include a shadow mask with a plurality of beam passage holes, a
frame including a supporting portion with a pair of long sides and a pair of short
sides fixed to the shadow mask, and a strength maintenance portion bent and
formed from the supporting portion.
[0013] The frame can include a plurality of reinforcement indentations formed
15 on a portion of the boundary between the supporting portion and the strength
maintenance portion.
[0014] At least one of the reinforcement indentations can satisfy the following
conditions:

20
[0015] wherein a and b respectively represent the distance from the end of the long side of the frame to one side and to the other side of the reinforcement indentation located on the long side of the frame, a' and b' respectively represent the distance from the end of the short side of the frame to one side and to the
25 other side of the reinforcement indentation located on the short side of the frame,
and wherein LH and Lv respectively represent the lengths of the long side and of the short side of the frame.
[0016] In addition, the reinforcement indentation can include first indentations located on the center of the long and the short sides of the frame, second
30 indentations located next to the first indentations and at a predetermined distance
from the first indentations, and third indentations located on the four corners of the frame.
3

[0017] At least one of the second indentations can satisfy at least one of the conditions described above.
[0018] Furthermore, the mask assembly for a CRT according to the exemplary
embodiment of the present invention can include a shadow mask with a plurality of
5 beam passage holes, a frame including a supporting portion with a pair of long
sides and a pair of short sides fixed to the shadow mask, and a strength
maintenance portion bent and formed from the supporting portion.
[0019] The frame can include a plurality of reinforcement indentations formed
on a portion of a boundary between the supporting portion and the strength
10 maintenance portion.
[0020] At least one of the reinforcement indentations can satisfy the following condition:

[0021] wherein Si represents the area of a triangle defined by the whole width
15 of the supporting portion that includes the reinforcement indentation, the whole
width of the strength maintenance portion that includes the reinforcement
indentation and the imaginary line connecting the ends of the supporting portion
and the strength maintenance portion, and wherein S2 represents the sectional
area of the reinforcement indentation.
20 [0022] The reinforcement indentation can include first indentations located on
the center of the long and the short sides of the frame, second indentations located
next to the first indentations at a predetermined distance from the first indentations,
and third indentations located on the four corners of the frame.
[0023] At least one of the second indentations can satisfy the condition
25 described above.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] A more complete appreciation of the present invention and many of the
attendant advantages thereof, will be readily apparent as the present invention
30 becomes better understood by reference to the following detailed description when
considered in conjunction with the accompanying drawings in which like reference symbols indicate the same or similar components, wherein:
[0025] FIG. 1 is a perspective view of a mask assembly for a Cathode Ray
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Tube (CRT) according to an exemplary embodiment of the present invention.
[0026] FIG. 2 is a perspective view of a frame according to the exemplary
embodiment of the present invention.
[0027] FIG. 3 is a sectional view of FIG. 2 taken along the line Ill-Ill.
5 [0028] FIG. 4A and 4B are graphs of the amplitudes at the welding point on a
long side of the frame according to the position of a second indentation.
[0029] FIG. 5 is a perspective view of the frame according to the exemplary
embodiment of the present invention.
[0030] FIG. 6A and 6B are graphs of the amplitudes at the welding point on a
10 short side of the frame according to the position of the second indentation.
[0031] FIG. 7 is a sectional view of FIG. 2 taken along the line VII-VII.
[0032] FIG. 8 is a schematic view of areas S1 and S2 in the frame according
to the exemplary embodiment of the present invention.
[0033] FIG. 9 is a graph of the amplitude at the welding point of the shadow
15 mask and the frame according to the area of the second indentation.
[0034] FIG. 10 is a partial sectional perspective view of a CRT adopting the
mask assembly according to the exemplary embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
20 [0035] The present invention is described more fully hereinafter with reference
to the accompanying drawings, in which a certain exemplary embodiment of the
present invention is shown.
[0036] FIG. 1 is a perspective view of a mask assembly for a Cathode Ray
Tube (CRT) according to an exemplary embodiment of the present invention, and
25 FIG. 2 is a perspective view of a frame 20 showing a strength maintenance portion
22 arranged toward the upper portion of the drawing.
[0037] As shown in the drawings, the mask assembly for a CRT includes a
shadow mask 10 with a plurality of beam passage holes 11 and the frame 20 that
is fixed to the shadow mask 10 and supports it.
30 [0038] The shadow mask 10 includes a holed portion 12 constituting an
effective screen portion, a non-holed portion 13 surrounding the holed portion 12,
and a skirt portion 14 bent to extend from the non-holed portion 13 to the frame 20.
[0039] The holed portion 12 has a plurality of beam passage holes 11, and the
shadow mask 10 is formed of Invar or an aluminum killed steel, for example.
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[0040] The frame 20 includes a supporting portion 21 attached to the skirt
portion 14 of the shadow mask 10, and the strength maintenance portion 22,
having a predetermined width, and bent to extend from the supporting portion 21 to
the inside of the frame 20.
5 [0041] The supporting portion 21 has a pair of long sides and a pair of short
sides corresponding to the shape of the skirt portion 14.
[0042] A plurality of reinforcement indentations 23, 24, and 25 are formed on a portion of a boundary between the supporting portion 21 and the strength maintenance portion 22.
10 [0043] The frame 20 with the above structure can be made by deforming
sheet metal by deep drawing, or by attaching an L-shaped metal sheet by welding and deforming the reinforcement indentations 23, 24, and 25 by a deep drawing process. [0044] The shadow mask 10 and the frame 20 are attached to each other by
15 welding the skirt portion 14 of the shadow mask 10 to the supporting portion 21 of
the frame 20.
[0045] In the present embodiment, three reinforcement indentations (one indentation 23 and two indentations 24) are arranged on each of the sides of the frame 20, and a reinforcement indentation 25 is arranged on each corner of the
20 frame 20.
[0046] More specifically, the reinforcement indentations 23, 24, and 25 include first indentations 23 located on the middle of the long sides and the short sides of the frame 20, second indentations 24 located on either side of and at a predetermined distance from the first indentations 23, and third indentations 25
25 located on the corners of the frame 20 at a predetermined distance from the
second indentations 24.
[0047] The first indentations 23 and the second indentations 24 are elongated in a straight line, and the third indentations 25 are L-shaped such that they wrap around the corners of the frame 20. The reinforcement indentations can be
30 arranged in bilateral symmetry with respect to the center of the sides.
[0048] FIG. 3 is a sectional view of the height and the protrusion depth of the reinforcement indentations 23, 24, and 25. In the drawing, H represents the height of the first indentation 23 and D represents the protrusion depth thereof in the direction toward the inside of the frame 20.
6

[0049] The height of the reinforcement indentations 23, 24, and 25 is
measured according to the direction of the width of the supporting portion 21, and
the protrusion depth of the reinforcement indentation 23, 24, and 25 is defined by
the depth measured in the direction of the width of the strength maintenance
5 portion 22.
[0050] In the present embodiment, at least two of the reinforcement indentations 23, 24, and 25 have different heights from each other. For instance, the height of the third indentation 25 is less than that of the first indentation 23 and the second indentation 24.
10 [0051] Since the third indentation 25 is substantially L-shaped, it can provide
enough strength reinforcement in spite of its lesser height than that of the elongated first and second indentations 23 and 24.
[0052] The first indentation 23 and the second indentation 24 on each of the long and short sides of the frame 20 can also have different heights from each
15 other. The drawings show that the first indentation 23 has greater height than
that of the second indentation 24, as an example.
[0053] In addition, at least two of the reinforcement indentations 23, 24, and 25 can have different protrusion depths from each other.
[0054] For instance, the protrusion depth of the second indentation 24 can be
20 greater than that of the first and third indentations 23 and 25, and the protrusion
depth of the third indentation 25 can be greater than that of the first indentation 23. [0055] It is more effective for the reinforcement of strength to have the protrusion depths of the second and third indentations 24 and 25 be greater than that of the first indentation 23.
25 [0056] In the frame 20 with the above structure, the second indentation 24 can
satisfy at least one of the following conditions regarding the length, position, and volume according to its height and protrusion depth with respect to improving the strength of the frame 20.
[0057] The condition regarding the length and the position of the second
30 indentation 24 located on the long sides is described below.
[0058] As shown in FIG. 2, a represents the distance from the end of the long sides of the frame 20 to one side of the second indentation 24, and b represents the distance from the end of the long side of the frame 20 to the other side of the second indentation 24.
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[0059] In this situation, the second indentation 24 satisfies the following Formula 1:
[0060] wherein LH represents the length of the long sides of the frame 20.
5 [0061] FIG. 4A and 4B are graphs of the amplitudes at the welding point on a
long side of the shadow mask 10 according to the position of the second indentation 24 while vibrations are applied to the long side of the frame 20.
[0062] The welding point at which the amplitude was measured is located on the long side of the frame 20 (hereinafter, referred to as the "long side welding
10 point").
[0063] More specifically, FIG. 4A is a graph of the amplitude on the long side welding point while a is varied to be LH/12, LH/6, and LH/4, and b is fixed at LH/3.
[0064] FIG. 4B is a graph of the amplitude on the long side welding point while b is varied to be U/4, U/3, and 5IV12, and a is fixed at LH/6.
15 [0065] In FIG. 4A, the values indicating the amplitude of the long side welding
point are values that are comparative to the value measured when the distance a is LH/12. In FIG. 4B, the values indicating the amplitude of the long side welding point are values that are comparative to the value measured when the distance b is5LH/12.
20 [0066] As shown in the FIG. 4A and 4B, while the same condition of vibration
is given, when the distance a is above LH/6, the amplitude on the long side welding point rises abruptly, and when the distance b is less than LH/3, the amplitude on the long side welding point rises abruptly.
[0067] The rises of the amplitude on the long side welding point represent the
25 shaking of the shadow mask 10. Accordingly, the characteristics of the image
quality deteriorate due to the change of the position of the beam passage holes 11. [0068] However, when the second indentation 24 located on the long side of the frame 20 satisfies Formula 1, the shaking of the shadow mask 10 is effectively prevented by absorbing the vibration applied to the long side of the frame 20.
30 [0069] The conditions regarding the length and the position of the second
indentation 24 are described below.
[0070] As shown FIG. 5, a' represents the distance from the end of the short side to one side of the second indentation 24, and b' represents the distance from
8

the end of the short side to the other side of the second indentation 24. In this situation, the second indentation 24 satisfies the following Formula 2:
[0071] wherein Lv represents the length of the short sides of the frame 20.
5 [0072] FIG. 6A and 6B are graphs of amplitudes at the welding point on the
shadow mask 10 and the frame 20 according to the position of the second
indentation 24.
[0073] The welding point at which the amplitude of vibration was measured is
located on the short side of the frame 20 (hereinafter, referred to as the "short side
10 welding point").
[0074] More specifically, FIG. 6A is a graph of the amplitude on the short side
welding point while a' is varied to 3Lv/20, Lv/5, and Lv/4 and b' is fixed as 3LV/10.
[0075] FIG. 6B is a graph of the amplitude on the short side welding point
while b' is varied as Ly/4, 3U/10 and 7LHv/20 and a' is fixed as Lu/5.
15 [0076] In FIG. 6A, the values indicating the amplitude of the short side welding
point are values that are comparative to the value measured when the distance a*
is 3Lv/20. In FIG. 6B, the values indicating the amplitude of the short side welding
point are values that are comparative to the value measured when the distance b'
is 7U/20.
20 [0077] As shown in FIG. 6A and 6B, while the same condition of vibration is
applied, when the distance a' is above Lv/5, the amplitude on the short side
welding point rises abruptly, and when the distance b' is less than 3LV/10, the
amplitude on the short side welding point rises abruptly.
[0078] The rises of the amplitude on the short side welding point also
25 represent the shaking of the shadow mask 10. Accordingly, the characteristics of
the image quality are deteriorated due to the change of the position of the beam
passage holes 11.
[0079] However, when the second indentation 24 located on the short side of
the frame 20 satisfies Formula 2, the shaking of the shadow mask 10 is effectively
30 prevented by absorbing the vibration applied to the short side of the frame 20.
[0080] The volume conditions of the second indentation 24 are described
hereinafter.
[0081] FIG. 7 is a sectional view of FIG. 2 taken along the line VII-VII, and in
9

the drawing, H represents the height of the second indentation 24, and D
represents the protrusion depth of the second indentation 24 toward the inside of
the frame 20.
[0082] Although FIG. 7 shows the second indentation 24 located at the long
5 side of the frame 20 as an example, the following volume condition of the second
indentation 24 is also applied to the second indentations 24 located on the short
side of the frame 20.
[0083] In FIG. 7, a triangle is defined by an imaginary line connecting the end
of the supporting portion 21 and the end of the strength maintenance portion 22,
10 the whole width of the supporting portion W1 comprising the height of the second
indentation H and the whole width of the strength maintenance portion W2
comprising the protrusion depth of the second indentation D.
[0084] In FIG. 8, St represents the area of the triangle, and S2 represents the
sectional area of the second indentation 24.
15 [0085] The sectional area of the second indentation 24 S2 is the product of the
height H and the protrusion depth D of the second indentation 24, and that is
applied when the sectional shape of the second indentation 24 is a square.
[0088] But the sectional shape of the second indentation 24 is not limited to
the square shown in the drawings, and it can be a pentagon, a hexagon, or other
20 various shapes.
[0087] In all of these cases, the area S2 is defined as the sectional area of the
second indentation 24 projected toward the inside of the frame 20, when it is
shown as a section.
[0088] The second indentation 24 satisfies the following Formula 3:

25 (3)
[0089] An experiment was conducted in such a way that for the second
indentation located on the long side of the frame, the amplitude on the long side
welding point was measured while the vibration was applied to the long side of the
frame, and for the second indentation located on the short side of the frame, the
30 amplitude on the short side welding point was measured while the vibration was
applied to the short side of the frame.
[0090] In both cases, the results of the experiment were the same as shown in FIG. 9.
10

[0091] As shown in FIG. 9, on the same condition of vibration, when the
sectional area of the second indentation is less than Si/3, the amplitude on the
welding point of the shadow mask and the frame rises abruptly.
[0092] Accordingly, it is desirable for the sectional area of the second
5 indentation S2 to be §J3 or more.
[0093] In addition, since the strength of the frame is reduced by the second
indentation when the sectional area of the second indentation is more than 2s-,/3, it is desirable for the sectional area of the second indentation S2 to be 2s!/3 or less.
[0094] As described above, when the second indentation satisfies Formula 3,
10 the strength and the vibration absorbing ability of the frame can be improved.
[0095] FIG. 10 is a perspective view of a CRT including the mask assembly according to the exemplary embodiment of the present invention.
[0096] As shown in the drawing, the CRT is formed by a vacuum vessel having a panel 30, a funnel 31, and a neck portion 32, and an electron gun 34, A
15 deflection yoke 35 is arranged on the vacuum vessel.
[0097] A phosphor screen 33 is formed on the inner surface of the panel 30 with red R, green G, and blue B phosphors patterned while interposing a black matrix BM.
[0098] The mask assembly comprising the shadow mask 10 and the frame 20
20 is installed inside of the panel 30 such that it is spaced apart from the phosphor
screen 33 by a predetermined distance.
[0099] With the CRT, the electron beams emitted by the electron gun 32 are deflected due to the deflection magnetic field of the deflection yoke 35, and pass through the beam passage holes 11 of the shadow mask 11 having a color
25 selection function. The electron beams then collide against the green, blue, and
red phosphors of the phosphor screen 33 formed on the inner surface of the panel 30. Consequently, the phosphors are excited to thereby display the desired images.
[0100] With the above structure, the mask assembly according to the present
30 embodiment can minimize shaking of the shadow mask and deterioration of image
quality due to the vibration by absorbing the vibration transferred to the frame.
[0101] The mask assembly according to the present invention has more effect when it is applied to a CRT having a deflection angle of 110 degrees.
[0102] While the present invention has been described in connection with
11

certain exemplary embodiments, it is to be understood that the present invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

WE CLAIM:
WHAT IS CLAIMED IS:-
1. A mask assembly for a Cathode Ray Tube (CRT), comprising:
a shadow mask including a plurality of beam passage holes; and
5 a frame including a supporting portion with a pair of long sides and a pair of
short sides attached to the shadow mask and a strength maintenance portion bent and arranged from the supporting portion;
wherein the frame includes a plurality of reinforcement indentations
arranged on a portion of a boundary between the supporting portion and the
10 strength maintenance portion; and
wherein at least one of the reinforcement indentations satisfy the following conditions:

15 wherein a and b respectively represent a distance from the end of the long
side to one side and the other side of the reinforcement indentation located on the long side, a' and b' respectively represent a distance from the end of the short side to one side and the other side of the reinforcement indentation located on the short side, and LH and Lv respectively represent a length of the long side and the short
20 side of the frame.
2. The mask assembly for a CRT of claim 1, wherein the reinforcement
indentations comprise:
first indentations arranged on a center of the long side and the short side of
25 the frame;
second indentations arranged next to and at a predetermined distance from the first indentation; and
third indentations arranged on four corners of the frame;
wherein at least one of the second indentations satisfies at least one of the
30 conditions.

3. The mask assembly for a CRT of claim 2, wherein the first indentations and the second indentations are elongated in a straight line, and wherein the third indentations are L-shaped and adapted to wrap around the corners of the frame.
5 4. The mask assembly for a CRT of claim 2, wherein the reinforcement
indentations have heights according to a direction of the width of the supporting portion, and wherein the height of the third indentations is less than that of the first and the second indentations.
10 5. The mask assembly for a CRT of claim 2, wherein the reinforcement
indentations have protrusion depths according to the direction of the width of the strength maintenance portion, and wherein the second indentations have greater protrusion depth than that of the third indentations, and the third indentations have greater protrusion depth than that of the first indentations.
L5
6. The mask assembly for a CRT of claim 2, wherein at least one of the second indentations satisfies the following condition:

wherein S^ represents an area of a triangle defined by a width of the supporting
20 portion comprising the second indentation, a width of the strength maintenance
portion comprising the second indentation and an imaginary line connecting an end of
the supporting portion and an end of the strength maintenance portion, and wherein
S2 represents a sectional area of the second indentation.
25 7. A mask assembly for a Cathode Ray Tube (CRT), comprising:
a shadow mask including a plurality of beam passage holes; and
a frame including a supporting portion with a pair of long sides and a pair of
short sides fixed to the shadow mask and a strength maintenance portion bent and
arranged from the supporting portion;
30 wherein the frame includes a plurality of reinforcement indentations arranged

on a portion of the boundary between the supporting portion and the strength maintenance portion, and wherein at least one of the reinforcement indentations satisfies the following condition:

5 wherein ST represents an area of a triangle defined by a width of the supporting
portion comprising a reinforcement indentation, a width of the strength maintenance portion comprising the reinforcement indentation and an imaginary line connecting an end of the supporting portion and an end of the strength maintenance portion, and wherein S2 represents a sectional area of the reinforcement indentation.
10
8. The mask assembly for a CRT of claim 7, wherein the reinforcement
indentation comprises first indentations arranged on a center of the long side and the
short side of the frame and second indentations arranged next to and at a
predetermined distance from the first indentations and third indentations arranged on
15 four corners of the frame, and wherein at least one of the second indentations satisfies the condition.
9. The mask assembly for a CRT of claim 8, wherein the first indentations
and the second indentations are elongated in a straight line, and wherein the third
20 indentations are L-shaped and adapted to wrap around the corners of the frame.
10. The mask assembly for a CRT of claim 8, wherein the reinforcement
indentations have heights according to a direction of the width of the supporting
portion, and wherein the height of the third indentations is less than that of the first
25 and the second indentations.
11. The mask assembly for a CRT of claim 8, wherein the reinforcement
indentations have protrusion depths according to the direction of the width of the
strength maintenance portion, and wherein the second indentations have greater
30 protrusion depth than that of the third indentations, and the third indentations have

greater protrusion depth than that of the first indentations

12. The mask assembly for a CRT of claim 8, wherein at least one of the
second indentations arranged on the long side of the frame satisfies the following
condition:

wherein a and b respectively represent a distance from an end of the long side to one side and the other side of the second indentation, and LH represents a length of the long side of the frame.
10
13. The mask assembly for a CRT of claim 8, wherein at least one of the
second indentations arranged on the short side satisfies the following condition:

wherein a* and b' respectively represent a distance from an end of the short
15 side to one side and the other side of the second indentation, and wherein Lv represents a length of the short side of the frame.

14. A mask assembly for a Cathode Ray Tube (CRT) substantially as herein described with reference to the accompanying drawings.
Dated this 20th day of March, 2006.

16

ABSTRACT OF THE DISCLOSURE
A mask assembly for a Cathode Ray Tube (CRT) includes a shadow mask with a plurality of beam passage holes, and a frame including a supporting portion with a pair of long sides and a pair of short sides which fix the shadow mask and a strength
5 maintenance portion bent from the supporting portion. The frame includes a plurality of reinforcement indentations formed on a portion of the boundary between the supporting portion and the strength maintenance portion. At least one of the reinforcement indentations satisfies the following condition:

10 wherein S1 represents an area of a triangle defined by a width of the supporting
portion including the reinforcement indentation, a width of the strength maintenance portion including the reinforcement indentation and an imaginary line connecting an end of the supporting portion and an end of the strength maintenance portion, and wherein S2 represents a sectional area of the reinforcement indentation.

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