Elastic member for supporting shadow mask of color picture tube

An elastic member for supporting the shadow mask of a color picture tube comprises a fixing portion having a welding point which is moved from the bottom end to the center or closer to the top end thereof, so that the fixing portion is fixed to the frame of the color picture at the welding point, a sliding portion and a connecting portion to be attached to the panel pin of a face panel through a connecting hole.

BACKGROUND OF THE INVENTION 
The present invention relates to a fixing elastic member for supporting 
shadow mask of a color picture tube. Particularly, it relates to the 
elastic member with reduced permanent plastic deformation of elastic 
member caused by repetitive work of removal and attachment of the shadow 
mask from the color picture tube. 
In the conventional color picture tube referring to FIG. 1, electron beams 
emitted from electron gun 5 of neck 3 and selected by shadow mask 6 are 
guided to radiate red, green and blue lights, emitting phosphor components 
of a luminescent screen formed inside of panel 1. 
Only 20% of the electron beam is to pass through the shadow mask 6 and the 
remaining 80% will be absorbed by it. Due to this absorbed beam, the 
shadow mask 6 is expanded. This causes a change of distance between shadow 
mask 6 and panel 1, which results in the degrading of color purity. It is, 
however, to note that in this stage elastic member 8 is used to prevent 
the degrading of color purity resulted from the change of position. In 
other words, in a situation where a position change has occurred according 
to shadow mask's heat expansion by the electron beam emanated from 
electron gun 5, the elastic member 8 allows the shadow mask 6 to move from 
the position 9 to 9(a) toward the panel 1 in order to prevent degrading of 
color purity. 
In the conventional elastic member design referring to FIG. 4, the welding 
point A of fixing portion 80 is located at 3/4 (three quarters) of fixing 
portion's length from top end 80a thereof where the plastic deformation of 
elastic member 8 occurs so often as the excessive force over the 
elasticity limit is applied to elastic member 8, due to the repetitive 
work of launching the shadow mask 6 to color picture tube. Moreover, the 
color purity is degraded when a member among several elastic members is 
deformed more than others, which causes the shadow mask deviation from a 
prearranged position. 
As shown in FIGS. 2 through 4, the conventional elastic member comprises 
fixing portion 80 welded at the welding point A to mask frame 7 supporting 
shadow mask 6, a connecting portion 81 having a connecting hole 81a 
attached through panel pin 1a formed interior of the panel land a sliding 
portion 82 by which the fixing portion 80 and the connecting portion 81 
form a one piece. 
In this regard, the moving distance of shadow mask 6 moved toward panel 1 
by elastic member 8 is the same as the length of sliding portion 82. 
Further it relates to the horizontal distance between fixing portion 80 
and panel pin 1a. 
Generally, in case of shadow mask using invar shadow mask with non-frame, 
the length of fixing portion is less than 5 mm, that of sliding portion is 
approximately 16 mm and that of connecting portion is around 18.5 mm, 
while the thickness of it is about 0.76 mm. With reference to FIG. 4, the 
welding point A of fixing portion 80 welded to mask frame 7 is located at 
three quarters of fixing portion's length from top end 80a thereof. And 
elastic member 8 has the limitation of transferring the shadow mask 6 to a 
certain distance toward panel 1. As a result, the length of sliding 
portion 82 has to be decided within a fixed range. 
On the other hand, elastic member of second embodiment as shown in FIG. 5 
comprises two pieces of the conventional elastic member shown in FIG. 4, 
welded symmetrically with each other so that it forms one elastic member. 
Furthermore, the connecting portion 812 without any connecting hole is 
welded to mask frame 7 whereas the other connecting portion 81 with 
connecting hole 81a is attached through panel pin 1a. The sliding portion 
811 connects the second fixing portion 813 and the connecting portion 812. 
This type of elastic member, like one-piece elastic member, has a function 
of transferring shadow mask 6 toward panel 1 in order to prevent the 
degrading of color purity. 
When the distance between the shadow mask and the panel changes due to heat 
expansion of the shadow mask; the problem of one-piece still applies to 
the two-piece elastic member because of the fact that the welding point A 
for fixing portion 80 and second fixing portion 813 is still located at 
three quarters of fixing portion's length from top end 80a thereof. 
SUMMARY OF THE INVENTION 
It is an object of the present invention is to provide an elastic member 
for supporting shadow mask of a color picture tube to decrease permanent 
plastic deformation of the elastic member resulted from the repetitive 
work of shadow mask removal from color picture tube. In order to achieve 
aforementioned objects, a welding point of fixing portion, which is 
attached to a mask frame, is disposed at less than one half (1/2) distance 
of fixing portion's length, which is in between the center of fixing 
portion and top end thereof. 
Further scope of applicability of the present invention will become 
apparent from the detailed description given hereinafter. However, it 
should be understood that the detailed description and specific examples, 
while indicating preferred embodiments of the invention, are given by way 
of illustration only, since various changes and modifications within the 
spirit and scope of the invention will become apparent to those skilled in 
the art from this detailed description. 
BRIEF DESCRIPTION OF THE DRAWING 
The present invention will become more fully understood from the detailed 
description given hereinbelow and the accompanying drawings which are 
given by way of illustration only, and, thus, are not limitative of the 
present invention, and wherein: 
FIG. 1 is a partial, side sectional view showing the structure of a color 
picture tube. 
FIG. 2 is a partial perspective view showing the attached position of an 
elastic member. 
FIG. 3 is an enlarged fragmentary sectional view showing the position 
change an of elastic member. 
FIG. 4 is a partially enlarged, fragmentary sectional view showing a 
conventionally welded elastic member to a mask frame. 
FIG. 5 is a partially enlarged fragmentary sectional view of other type of 
elastic member according to the prior art. 
FIG. 6 is a partially enlarged fragmentary sectional view of a welded 
elastic member according to the present invention. 
FIG. 7 is a partially enlarged fragmentary sectional view of second 
embodiment according to the present invention. 
FIG. 8 is a partially enlarged, fragmentary sectional view showing a 
repetitive displacement test. 
FIG. 9 is a graph of displacement quantity of the conventional elastic 
member compared with that of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The elastic member according to the present invention is described in 
detail by preferred embodiments of accompanying drawings. 
The elastic member according to the present invention is an elastic body 
comprising a fixing portion, a connecting portion and a sliding portion. 
The fixing portion is a portion welded into the mask frame which supports 
the shadow mask in a certain position and the connecting portion includes 
a connecting hole through which the fixing portion is attached to the 
panel pin disposed on the inner side of panel. The sliding portion 
connects the fixing portion and the connecting portion, forming a 
one-piece elastic member. 
The elastic member according to the present invention relates to the 
embodiment in which welding point is changed from three quarters of fixing 
portion's length from top end thereof to less than one half (1/2) of the 
same length from top end thereof. This elastic member is for decreasing 
the degrading of color purity resulted from the position change due to the 
heat expansion of shadow mask. 
In the preferred embodiment of the present invention as shown in FIG. 6, 
the fixing portion is directly welded into the mask frame 7 which supports 
the shadow mask. Without departing from the scope of the present 
invention, an elastic member having the fixing portion with 5 mm length, 
16 mm long connecting portion, approximately 18.5 mm long sliding portion 
and 0.76 mm thickness can be used. It is preferable to use the stainless 
steel as substance for elastic member. 
In aforementioned embodiment, because a welding point A of fixing portion 
80 attached to mask frame 7 is located at less than one half (1/2) of the 
length from top end 80a thereof, an extended portion which is the portion 
from welding point A to the bottom end of fixing portion contributes to 
the reduction of the permanent plastic deformation of elastic member when 
the excessive force is applied. 
Accordingly, without changing the size of the elastic member, the present 
invention decreases the permanent plastic deformation of the elastic 
member because of the fact that sliding portion is substantially elongated 
by the length from the welding point A to the bottom end of fixing 
portion. 
FIGS. 8 and 9 show the displacement test method and its comparison data of 
the conventional elastic member's displacement quantity and that of the 
present invention. 
To know the variation of horizontal distance between fixing portion, and 
connecting portion several repetitive tests were conducted. 
The result shows that plastic deformation of the elastic member according 
to the present invention is reduced by moving the welding point toward the 
top end of fixing portion. 
In the another embodiment of the present invention shown in FIG. 7, elastic 
member is formed in two pieces where one piece elastic member is 
symmetrically welded into another elastic member. Here, the connecting 
portion 812 is attached to mask frame 7, the fixing portions 813, 80 of 
each piece one welded into each other, and the welding point is disposed 
at less than one half of fixing portion's length from top end 80a thereof. 
This another embodiment of the present invention has same functions and 
effects as those of first embodiment while specific embodiments of the 
invention have been illustrated and described wherein, it is to realize 
that modifications and changes will occur to those skilled in the art. 
It is therefore to be understood that the appended claims are intended to 
cover all modifications and changes which fall within the scope of the 
invention. 
The invention being thus described, it will be obvious that the same may be 
varied in many ways. Such variations are not to be regarded as a departure 
from the spirit and scope of the invention, and all such modifications as 
would be obvious to one skilled in the art are intended to be included 
within the scope of the following claims.