1. A method of assembling a color selecting mechanism for a cathode-ray tube, comprising the steps of: preparing a grid structure 1 formed of a square metal sheet having a plurality of slits 3 extending in the direction perpendicular to a pair of parallel sides of said metal sheet; pressing a frame" 7 having a pair of members 9 in parallel to each other in the same direction as that of said parallel sides of said metal sheet in such a manner that said members 9 are close to each other; welding a pair of said parallel sides of said grid structure 1 each to a pair of said members 9; and releasing the pressure applied to said frame 7 and mounting said grid structure 1 on said frame 7 in a stretching state; wherein each of intervals "w" between welded points at which said grid structure 1 is welded to said members 9 is set to be in a range from 20 to 35 times a thickness "t" of said grid structure 1 and from 8 to 14 times a pitch "p" of said slits 3.

2. A method of assembling a color selecting mechanism for a cathode-ray tube according to claim 1, wherein each of said intervals "w" between welded points is set to be in a range from 24 to 29 times a thickness "t" of said grid structure 1 and from 8 to 14 times a pitch "p" of said slits 3.

3. A method of assembling a color selecting mechanism for a cathode-ray tube according to claim 1, wherein each of said intervals "w" between welded points is set to be in a range from 20 to 35^ times a thickness "t" of said grid structure 1 and from 10 to 12 times a pitch "p" of said slits 3.

4. A method of assembling a color selecting mechanism for a cathode-ray tube according to claim 1, wherein each of said intervals "w" between welded points is set to be in a range from 24 to 29 times a thickness "t" of said grid structure 1 and from 10 to 12 times a pitch "p" of said slits 3.

5. A color selecting mechanism for a cathode-ray tube, comprising: a grid structure 1 formed of a square metal sheet having a plurality of slits 3 extending in the direction perpendicular to a pair of parallel sides of said metal sheet; and a frame 7 having a pair of members 9 in parallel to each other in the same direction as that of said parallel sides of said metal sheet; wherein said grid structure 1 is installed to said frame 7 by pressing said frame 7 in such a manner that said members 9 are close to each other, welding a pair of said parallel sides of said grid structure 1 each to a pair of said members 9, and releasing the pressure applied to said frame 7 and mounting said grid structure 1 on said frame 7 in a stretching state^ and each of intervals "w" between welded points at which said grid structure 1 is welded to said members 9 is set to be in a range from 20 to 35 times a thickness "t" of said grid structure 1 and from 8 to 14 times a pitch "p" of said slits 3.

6. A color selecting mechanism for a cathode-ray tube according to claim 5, wherein each of said intervals "w" between welded points is set to be in a range from 24 to 29 times a thickness "t" of said grid structure 1 and from 8 to 14 times a pitch "p" of said slits 3.

7. A color selecting mechanism for a cathode-ray tube according to claim 5, wherein each of said intervals "w" between welded points is set to be in a range from 20 to 35 times a thickness "t" of said grid structure 1 and from 10 to 12 times a pitch "p" of said slits 3.

8. A color selecting mechanism for a cathode-ray tube according to claim 5, wherein each of said intervals "w" between welded points is set to be in a range from 24 to 29 times a thickness "t" of said grid structure 1 and from 10 to 12 times a pitch "p" of said slits 3.

9. A method of producing a color selecting mechanism for a cathode-ray tube substantially as hereinbefore described with reference to the accompanying drawings.

10. A color selecting mechanism for a cathode-ray tube substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

BACKGROUND OF THE INVENTION
The present invention relates to a method of assembling a color selecting mechanism for a color cathode-ray tube, and the color selecting mechanism assembled by the method.
Color selecting mechanisms for color cathode-ray tubes have been known, of a type in which a grid structure formed of a metal sheet having a plurality of slits (beam apertures) is mounted on a metal frame. A trinitron (trade name) type cathode-ray tube adopts a grid structure having linear apertures, which is called an aperture grille.
Fig. 3 is a perspective view of a color selecting mechanism, and Fig. 4 is an enlarged view of an essential portion of an aperture grille. An aperture grille 1 formed of a rectangular metal sheet has in an effective screen a plurality of slits 3 for allowing an electron beam to pass therethrough and tape portions 5 between these slits 3. The aperture grille 1 is mounted on a metal frame 7 formed in a rectangular shape by welding. The frame 7 includes a pair of parallel A members 9 which are curved and to which
the aperture grille 1 is to be welded, and B members 11 each connecting both ends of each of the A members 9 to each other.
The aperture grille 1 is mounted on the frame 7 by the steps of pressing the frame 7 in the direction where the A members 9 are close to each other, and welding in such a state opposed sides of the aperture grille 1 each to the A members 9 at suitable intervals between welded points by seam welding or laser- welding.
Next, by releasing the pressure applied to the frame 7, the aperture grille 1 is mounted on the frame 7 in a state being stretched at a high tension. The reason why the aperture grille 1 is mounted in a stretching state is to reduce mislanding of electron beams passing through slits of the aperture grille 1 on a phosphor screen due to thermal expansion of the aperture grille 1 upon operation of the cathode-ray tube. An excess peripheral portion of the aperture grille 1 projecting from the frame 7 is removed by trimming, to thus complete the mounting of the aperture grille 1 on the frame 7.
Recently, in color selecting mechanisms, it has been required to make finer the slit pitch and to make thinner the aperture grille 1 with the trend toward high precision and lightweightness. This makes it difficult to
mount the aperture grille 1 on the frame 7 in such a manner as to prevent occurrence of wrinkles by keeping the tape portions 5 in a suitable state, that is, in a state being matched with the curved surfaces of the A members 9. For example, with respect to the aperture grille 1 having a thickness of 0.1 mm, when the pressure applied to the frame 7 is released, wrinkles do not occur if the slit pitch is set at 0.5 mm; however, they occur at a high occurrence rate if the slit pitch is set at 0.25 mm. The occurrence rate of wrinkles is also dependent on the thickness of the aperture grille 1, and more concretely, it tends to be increased as the thickness of the aperture grille 1 becomes thinner.
The intervals between welded points at which the opposed sides of the aperture grille 1 are welded to a pair of the parallel A members 9 by seam welding or laser welding, have been suitably set to prevent occurrence of wrinkles. In the aperture grille 1, when each interval between welded points is excessively widened, a stress is concentrated at each welded point due to a reaction force from the frame 7 from which the compression is released, tending to produce torsion and strain at each tape portion 5. On the other hand, when the interval between welded points is excessively narrowed, each tape portion 5 cannot
absorb a difference in stress between adjacent welded points and thereby it tends to receive torsion and strain.
Accordingly, the related art method of assembling a color selecting mechanism suppresses somewhat occurrence of wrinkles by setting the interval between welded points to prevent occurrence of wrinkles; however, it cannot positively reduce occurrence of wrinkles, which obstructs improvement in quality. Such a disadvantage of the related art method includes an inconvenience that a suitable interval between welded points must be determined each time there is a change of a condition (thickness and/or slit pitch) in the case of manufacturing the aperture grilles 1 under special specifications.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a method of assembling a color selecting mechanism for a cathode-ray tube, which is capable of setting an optimum interval between welded points for preventing occurrence of torsion and strain, thereby stabilizing the quality of the color selecting mechanism and easily setting the interval between welded points even when there is a change of a condition (thickness and/or slit pitch).
Another object of the present invention is to
provide a color selecting mechanism assembled by the above method.
To achieve the first object, according to a first aspect of the present invention, there is provided a method of assembling a color selecting mechanism for a cathode-ray tube, including the steps of: preparing a grid structure formed of a square metal sheet having a plurality of slits extending in the direction perpendicular to a pair of parallel sides of the metal sheet; pressing a frame having a pair of members in parallel to each other in the same direction as that of the parallel sides of the metal sheet in such a manner that the members are close to each other; welding a pair of the parallel sides of the grid structure each to a pair of the members; and releasing the pressure applied to the frame and mounting the grid structure on the frame in a stretching state; wherein each of intervals between welded points at which the grid structure is welded to the members is set to be in a range from 20 to 35 times a thickness of the grid structure and from 8 to 14 times a pitch of the slits.
To achieve the second object, according to a second aspect of the present invention, there is provided a color selecting mechanism for a cathode-ray tube, including: a grid structure formed of a square metal sheet having a
plurality of slits extending in the direction perpendicular to a pair of parallel sides of the metal sheet; and a frame having a pair of members in parallel to each other in the same direction as that of the parallel sides of the metal sheet; wherein the grid structure is installed to the frame by pressing the frame in such a manner that the members are close to each other, welding a pair of the parallel sides of the grid structure each to a pair of the members, and releasing the pressure applied to the frame and mounting the grid structure on the frame in a stretching state; and each of intervals between welded points at which the grid structure is welded to the members is set to be in a range from 20 to 35 times a thickness of the grid structure and from 8 to 14 times a pitch of the slits.
Each of the above intervals between welded points may be set to be in a range from 24 to 29 times a thickness of the grid structure and from 8 to 14 times a pitch of the slits; or in a range from 20 to 35 times a thickness of the grid structure and from 10 to 12 times a pitch of the slits. More preferably, each of the above intervals between welded points may be set to be in a range from 24 to 29 times a thickness of the grid structure and from 10 to 12 times a pitch of the slits.
In the inventive method of assembling a color
selecting mechanism for a cathode-ray tube and the color selecting mechanism assembled by the method, each interval between welded points is set to be in the above specified range, and accordingly it is possible to ensure a degree of freedom for removing torsion and strain components around welded points and prevent a stress applied to each welded point from producing torsion and strain around the welded point, and hence to significantly reduce the occurrence rate of wrinkles occurring in the grid structure. As a result, it is possible to stabilize the quality of the color selecting mechanism and to easily set the interval between welded points even when there is a change of a condition (thickness and/or pitch).
BRIEF DESCRIPTION OF THE DRAWINGS
Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings wherein:
Fig. 1 is an illustrative view of intervals between welded points at which an aperture grille is welded to a frame in accordance with an assembling method of the present invention;
Fig. 2 is a flow chart showing a procedure of
assembling a color selecting mechanism for a cathode-ray tube;
Fig. 3 is a perspective view of a color selecting mechanism; and
Fig. 4 is an enlarged view showing an essential portion of an aperture grille.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Hereinafter, preferred embodiments of a method of assembling a color selecting mechanism for a cathode-ray tube of the present invention will be described with reference to the drawings.
Fig. 1 is an illustrative view of intervals between welded points at which an aperture grille is welded on a frame in accordance with the assembling method of the present invention, and Fig. 2 is a flow chart showing a procedure for assembling a color selecting mechanism for a cathode-ray tube. In addition, parts corresponding to those shown in Figs. 3 and 4 are indicated by the same characters, and the repeated explanation thereof is omitted.
As shown in Figs. 2 and 3, a color selecting mechanism is assembled by the steps of cleaning a frame 7, mounting a spring holder 21 (see Fig. 3) to the frame 7,
pressing the frame 7 in such a manner that A members 9 to which the aperture grille 1 is to be welded are close to each other, and welding in such a state opposed sides of the aperture grille 1 each to the A members 9 by seam welding or laser welding.
Next, by releasing the pressure applied to the frame 7, the aperture grille 1 is mounted on the frame 7 in a state being stretched at a high tension. A portion of the aperture grille 1 projecting from the frame 7 is then removed by trimming, and the aperture grille 1 and the frame 7 are blackened, followed by mounting of the spring 23 and the like.
In the inventive assembling method, the aperture grille 1 is welded to the A members 9 at specified intervals "w" between welded points (see Fig. 1). More specifically, the interval "w" between welded points is set to be in a range of from 20t to 35t (t: thickness of aperture grille 1) and from 8p to 14p (p: pitch of slits 3). Such a range of the interval "w" between welded points is determined in consideration of the fact that torsion and strain of the aperture grille 1 produced after release of the pressure applied to the frame 1 are dependent on the interval between welded points and also the interval between welded points varies depending on the plate
thickness "t" of the aperture grille 1 and the pitch "p" of the slits.
Table 1 shows results of a test of examining occurrence rate of wrinkles for 17 inch type aperture grilles 1 (condition: specified as described below) which are each welded to frames 7 at different intervals between welded points.
Condition:
thickness of aperture grille: 0.1 mm
slit pitch: 0.25 mm Inspection of wrinkles: visual
As is seen from the results shown in Table 1, the occurrence rate of wrinkles is significantly higher when the interval between welded points is out of a range of from 2.0 mm to 3.5 mm. This shows that these values define the borderlines of the significantly increased occurrence rate of wrinkles, and accordingly, the range between these values, that is, from 2.0 mm to 3.5 mm has a critical characteristic in terms of occurrence rate of wrinkles.
Table 1
(Table Removed)

The reason why the above range has the critical characteristic is as follows: namely, when the interval between welded points is less than 2.0 mm, a degree of freedom for removing torsion and strain around welded points is made smaller (in other words, a distance for absorbing strain is shortened); and when the interval between welded points is more than 3.5 mm, a stress applied to each welded point 25 is made larger, tending to produce torsion and strain of the tape portions 5 around the welded point.
With respect to the aperture grille 1, when the pressure applied to the frame 7 is released, wrinkles do not occur if the slit pitch is set at 0.5 mm; while they occur at a high occurrence rate if the slit pitch is set at 0.25 mm. Accordingly, the occurrence rate of wrinkles tends to be increased as the slit pitch becomes smaller. Also, the occurrence rate of wrinkles tends to be increased as the thickness of the aperture grille 1 becomes thinner.
The range of the interval "w" between welded points can be converted in relation to these values (slit pitch "p", thickness "t") into a range of from 20 to 35 times of the thickness "t" and from 8 to 14 times the slit pitch "p". Namely, by setting the interval "w" between welded points in the range of from 20 to 35 times the thickness "t" and from 8 to 14 times the slit pitch "p", it is possible to obtain an effect of significantly reducing the occurrence of wrinkles, so-called, a peak effect in terms of occurrence of wrinkles.
Table 2 shows results of a test of examining the occurrence rate of wrinkles for aperture grilles ( condition: specified as described below) which are each welded to frames at intervals "w" between welded points in a range of 2.0 to 3.5 mm, wherein the number of measurement
is increased more than that in the previous test.
Condition:
thickness of aperture grille: 0.1 mm slit pitch: 0.25 mm Inspection for wrinkles: visual inspection
Table 2
(Table Removed)

As is seen from the results in Table 2, wrinkles do not occur when the interval between welded points is in a range of from 2.4 mm to 2.9 mm. This shows that the range between these value, that is, from 2.4 mm to 2.9 mm has a critical characteristic. As described above, the wrinkles
occur in the aperture grille 1 depending on the slit pitch "p" and the thickness "t", so that the above range is converted in relation to these values into a range of from 24 to 29 times the thickness "t" and from 9.6 to 11.6 (10 to 12 by rounding the numerical value below 1.0) times the slit pitch "p". Namely, by setting the interval "w" between welded points in the range of from 24 to 29 times the thickness "t" and from 10 to 12 times the slit pitch "p", it is possible to obtain a significant effect of eliminating occurrence of wrinkles.
According to the above-described method of assembling a color selecting mechanism for a cathode-ray tube, when the opposed sides of the aperture grille 1 are welded to the A members 9 of the frame by seam welding or laser welding while the frame 7 is pressed in such a manner that the A members 9 are closed to each other, the interval "w" between welded points is set to be in the range of from 20 to 35 times the thickness "t" and from 8 to 14 times the pitch "p", so that it is possible to significantly reduce the occurrence rate of wrinkles occurring in the aperture grille 1 after release of the pressure applied to the frame 7. Moreover, by setting the interval "w" between welded points in the range of from 24 to 29 times the thickness "t" and from 10 to 12 times the pitch "p", it is possible
to perfectly prevent wrinkles from occurring in the aperture grille 1 after release of the pressure applied to the frame 7.
Additionally, according to the above-described method of assembling a color selecting mechanism for a cathode-ray tube, since the interval "w" between welded points can be set in relation to the thickness "t" and the pitch "p", it is not required to determine the interval "w" between welded points each time there is a change of a condition (thickness and/or slit pitch) in the case of manufacturing the aperture grilles 1 under special specifications, that is, it is possible to easily set an optimum interval "w" between welded points for preventing occurrence of torsion and strain even when there is a change of the condition (thickness and/or slit pitch).
While the preferred embodiment of the present invention has been described, such description is for illustrative purposes only, and it is to be understood that changes and variations may be made without departing from the spirit or scope of the following claims.

We Claims:-
1. A method of assembling a color selecting mechanism
for a cathode-ray tube, comprising the steps of:
preparing a grid structure 1 formed of a square metal sheet having a plurality of slits 3 extending in the direction perpendicular to a pair of parallel sides of said metal sheet;
pressing a frame" 7 having a pair of members 9 in parallel to each other in the same direction as that of said parallel sides of said metal sheet in such a manner that said members 9 are close to each other;
welding a pair of said parallel sides of said grid structure 1 each to a pair of said members 9; and
releasing the pressure applied to said frame 7 and mounting said grid structure 1 on said frame 7 in a stretching state;
wherein each of intervals "w" between welded points at which said grid structure 1 is welded to said members 9 is set to be in a range from 20 to 35 times a thickness "t" of said grid structure 1 and from 8 to 14 times a pitch "p" of said slits 3.
2. A method of assembling a color selecting mechanism
for a cathode-ray tube according to claim 1, wherein each
of said intervals "w" between welded points is set to be in a range from 24 to 29 times a thickness "t" of said grid structure 1 and from 8 to 14 times a pitch "p" of said slits 3.
3. A method of assembling a color selecting mechanism for a cathode-ray tube according to claim 1, wherein each of said intervals "w" between welded points is set to be in a range from 20 to 35^ times a thickness "t" of said grid structure 1 and from 10 to 12 times a pitch "p" of said slits 3.
4. A method of assembling a color selecting mechanism for a cathode-ray tube according to claim 1, wherein each of said intervals "w" between welded points is set to be in a range from 24 to 29 times a thickness "t" of said grid structure 1 and from 10 to 12 times a pitch "p" of said slits 3.
5. A color selecting mechanism for a cathode-ray tube, comprising:
a grid structure 1 formed of a square metal sheet having a plurality of slits 3 extending in the direction perpendicular to a pair of parallel sides of said metal sheet; and
a frame 7 having a pair of members 9 in parallel to each other in the same direction as that of said parallel
sides of said metal sheet;
wherein said grid structure 1 is installed to said frame 7 by pressing said frame 7 in such a manner that said members 9 are close to each other, welding a pair of said parallel sides of said grid structure 1 each to a pair of said members 9, and releasing the pressure applied to said frame 7 and mounting said grid structure 1 on said frame 7 in a stretching state^ and
each of intervals "w" between welded points at which said grid structure 1 is welded to said members 9 is set to be in a range from 20 to 35 times a thickness "t" of said grid structure 1 and from 8 to 14 times a pitch "p" of said slits 3.
6. A color selecting mechanism for a cathode-ray tube according to claim 5, wherein each of said intervals "w" between welded points is set to be in a range from 24 to 29 times a thickness "t" of said grid structure 1 and from 8 to 14 times a pitch "p" of said slits 3.
7. A color selecting mechanism for a cathode-ray tube according to claim 5, wherein each of said intervals "w" between welded points is set to be in a range from 20 to 35 times a thickness "t" of said grid structure 1 and from 10 to 12 times a pitch "p" of said slits 3.
8. A color selecting mechanism for a cathode-ray tube
according to claim 5, wherein each of said intervals "w" between welded points is set to be in a range from 24 to 29 times a thickness "t" of said grid structure 1 and from 10 to 12 times a pitch "p" of said slits 3.
9. A method of producing a color selecting mechanism for a
cathode-ray tube substantially as hereinbefore described with
reference to the accompanying drawings.
10. A color selecting mechanism for a cathode-ray tube
substantially as hereinbefore described with reference to and as
illustrated in the accompanying drawings.