JPH05174722A - Manufacture of internal magnetic shield of image receiving tube - Google Patents

Abstract

PURPOSE:To accurately fold a plate by bending each plate edge located at the sides of the place intersecting the folding line to become the place of folding at the edge of the plate, and then performing folding along the folding line. CONSTITUTION:A part at the under-edge of a plate 11 is folded along the folding line, as shown in the attached illustration, using a press and die. The edge portions at the sides of each cut 200, 300 are bent along the bending lines 21 and ones 22, and then the plate 11 is folded along the bending lines 20. Two of such plates 11 as prepared in the described manner are used to fabricate a mask frame. Accordingly the bent portions are given a mechanical strength by bending each plate edge located at the sides of the place intersecting the folding line to become the place of folding at the edge of the plate 11, and the end of the line 20 is locates between these mechanically strengthened portions. The place of folding can be specified owing to the difference in the mechanical strength at the ends of the line 20, and folding can be done accurately along the line 20.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing an inner magnetic shield of a picture tube.

[0002]

2. Description of the Related Art For example, a color picture tube is provided with an internal magnetic shield formed of a truncated pyramid-shaped cylindrical portion which is positioned on the inner wall side and is closed on the electron gun side.

This internal magnetic shield is for shielding a so-called external magnetic field such as the earth's magnetism so as not to adversely affect the electron beam emitted from the electron gun and deflected by the magnetic field of the deflection yoke. Is.

The internal magnetic shield is constructed by assembling a plurality of bent plate members (for example, two) due to the peculiar shape of the truncated pyramid.

The structure of such an internal magnetic shield is described in detail, for example, in Japanese Unexamined Patent Publication No. 2-220334 or Japanese Unexamined Patent Publication No. 2-170919.

[0006]

However, the plate material for forming the internal magnetic shield has a thickness of 0.1.
It is as thin as about mm to 0.2 mm, and is subjected to a so-called bead processing to mechanically reinforce such a thin plate.

However, this bead has a restriction that it must be designed with a small processing strain. This is because the magnetic properties of the plate material are deteriorated due to changes in the magnetic permeability of the plate material when the baring and processing strain occur.

From the above, the plate material on which the bead is formed has a certain degree of mechanical strength, but when this plate material is bent, it can be bent accurately along the bending line which is the bending point. There was a problem that it could not be done.

Therefore, the present invention has been made under such circumstances, and the object of the present invention is to easily and accurately fold along a fold line which is a fold point. It is an object of the present invention to provide a method of manufacturing an inner magnetic shield of a picture tube.

[0010]

In order to achieve such an object, the present invention is basically based on a truncated pyramidal cylindrical portion which is positioned on the inner wall side of the picture tube and which is closed on the electron gun side. In the method for manufacturing a magnetic shield configured by assembling a plurality of bent plate materials, the side parts of the plate material are bent at both sides of a part intersecting with a bending line which is a bending part. After that, a step of bending along the bending line is included.

[0011]

According to the method of manufacturing an internal magnetic shield of a picture tube constructed as described above, in particular, each side portion positioned on both sides of a portion intersecting with a bending line which is a bending portion on a side portion of a plate member is bent. After that, it is bent along the bending line.

By bending the respective side portions positioned on both sides of the portion intersecting with the bending line which is the bending portion in the side portion of the plate material, the bent portion has mechanical strength, and these mechanical strengths are increased. The ends of the fold line will be located between the portions that have. Such a structure is the same at the other end of the bending line.

Therefore, since it becomes possible to specify the bending point at the both ends of the bending line by the difference in mechanical strength, it becomes possible to easily and accurately bend along the bending line.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a method of manufacturing an internal magnetic shield of a picture tube according to the present invention will be described below with reference to the drawings.

First, FIG. 7 is a sectional view showing an embodiment of a color picture tube having an internal magnetic shield to which the present invention is applied.

In the figure, 1 is a face panel, 2 is a phosphor surface, 3 is a shadow mask, 4 is a mask frame,
Reference numeral 5 is an internal magnetic shield, 6 is an electron gun, and 7 is a polarization yoke.

When a so-called external magnetic field such as terrestrial magnetism acts on the electron beam emitted from the electron gun 6 and deflected by the magnetic field of the deflection yoke 7, mislanding occurs to deteriorate the color luminance characteristic. The internal magnetic shield 5 attached to the mask frame 4 is for shielding the external magnetic field and has a truncated pyramid-shaped cylindrical portion that is closed on the electron gun 6 side.

Here, FIG. 8 is an external perspective view of the internal magnetic shield 5 attached to the mask frame 4. In the figure, the internal magnetic shield 5 fixed to the rectangular mask frame 4 is configured by combining two plate members that are symmetrical and three-dimensional. In the figure, the respective plate members are arranged with a virtual line 40 that is parallel to the long side and crosses the center of each pair of opposing short sides as a boundary.

Therefore, the lower side of each plate member forming the internal magnetic shield 5 is positioned on both sides of the side which is in contact with the long side of the mask frame 4 and on both sides of this side, and is half of the short side of the mask frame 4. The upper side is composed of sides and abutting sides, and the upper side is formed of sides shorter than the corresponding sides of the lower side. The side that connects the upper side and the lower side is configured as a side that contacts the side of the other plate.

1 to 5 are process drawings showing an embodiment of a method of manufacturing the above-mentioned internal magnetic shield 5.

Step 1. First, a plate material 11 made of carbon (C) steel and having a thickness of about 0.1 mm to 0.2 mm is prepared. Then, the plate material 11 is pressed into a predetermined shape. FIG. 1 is a view showing the shape of the punched plate material 11. The plate material 11 shown in FIG.
As shown in FIG. 8, it is a plate member 11 that constitutes a half portion on one side of the internal magnetic shield 5 configured as a three-dimensional shape.

Since the plate material 11 is bent along the dotted line shown in FIG. 6 in the subsequent steps, this embodiment has a shape as shown below. That is, the fold line 20 is formed between the side 11A that is in contact with the long side of the mask frame 4 and each side 11B that is positioned on both sides of this side 11A and that is in contact with half of the short sides of the mask frame 4 respectively. There is a bending portion indicated by, and the bending line 20 extends (linearly) between the respective sides 11C and 11D which are formed shorter than the corresponding sides of the lower side.

Then, notches 200 and 300 are formed at the intersections of the bent portion indicated by the bending line 20 and the lower side and the upper side, respectively. Moreover, the side portions positioned on both sides of the notch 200 are adapted to be bent in a later step, and a bending line indicating the bent portion is indicated by reference numeral 21 in the drawing. Similarly, each side portion positioned on both sides of the notch 300 is adapted to be bent in a later step, and a bending line indicating the bending portion is indicated by reference numeral 22 in the drawing.

In the figure, since a bent portion for fixing to the mask frame 4 is formed on the lower side of the plate member 11, a bending line 25 indicating the bent portion is formed at this portion.
It is shown.

Step 2. In order to increase the mechanical strength of the punched plate material 11, so-called bead molding is performed (FIG. 2). The lower and upper sides of the plate member 11 and the bending line 20
A bead 13 is formed in each area surrounded by and.
Here, the mechanical strength of the bead 13 is not so large and is limited. This is because when the bead 13 is formed with a large depth, processing strain is caused by the bead 13 and the magnetic permeability and the like change, and the magnetic characteristics of the internal magnetic shield 5 deteriorate.

Step 3. A portion attached to the mask frame 4, that is, a lower side portion of the plate material 11 is bent along a bending line 25 in FIG. 6 using a die press (FIG. 3). Here, the reason why the die press is used is that even after being bent, the flat plate shape is maintained as before and the cubic shape is not particularly bulky, and the pressing can be easily performed.

Step 4. Each notch 200 and 3 described above
00 are bent along the bending lines 21 and 22 on both sides thereof, and then the bending line 20 is bent.
The plate material 11 is bent along the line (FIG. 4). FIG. 4 shows that the bent side 26 is formed by bending the sides on both sides of the notch 300. Further, the bent sides are similarly formed on the sides on both sides of the notch 200 on the lower side (not shown). The bending along the bending line 20 after this is performed manually. This is because the bending at this time becomes three-dimensional and bulky, and the bending method is complicated.

Step 5. 2 pieces of the plate material 11 that has undergone the above-mentioned steps
Individually prepare and assemble to the mask frame 4 (FIG. 5).

According to the method of manufacturing the internal magnetic shield as described above, in particular, the side portions positioned on both sides of the side portion (lower side, upper side) of the plate member 11 that intersects with the bending line 20 that is the bending portion. Is bent to form a bent side 26, and then is bent along the bending line 20.

By bending the side portions positioned on both sides of the side portion of the plate member 11 that intersects with the bending line 20 which is the bending portion, the bent portion has mechanical strength and these mechanical portions The ends of the fold line 20 will be located between the strong parts. Such a structure is the same at the other end of the bending line 20.

Therefore, since the bending points can be specified at the both ends of the bending line 20 by the difference in mechanical strength, it becomes possible to easily and accurately bend along the bending line 20.

In the above-mentioned embodiment, the notch 200 or 300 is provided at the intersection of the side of the plate 11 and the bending line 20. These notches 2
00 or 300 has a technical effect such that the bent side 26 can be easily formed or the bent portion can be easily specified.
It is not necessarily an essential component of the present invention.

The point is that bent sides 26 may be formed on both sides of a portion of the side of the plate material 11 that intersects with the bending line 20 which is a bent portion.

In the above-mentioned embodiments, the present invention has been described with the bead formed for the purpose of reinforcing the plate material, but the present invention is not necessarily limited to the bead thus formed. , It can be applied even to the case where no beads are formed.

In the above-mentioned embodiment, the inner magnetic shield is constructed by assembling two plate materials.
Needless to say, the number is not limited to two, and a plurality may be used.

[0036]

As is clear from the above description,
According to the method for manufacturing an internal magnetic shield of a picture tube according to the present invention, the plate material forming the internal magnetic shield can be easily and accurately bent along a bending line which is a bending point.

[Brief description of drawings]

FIG. 1 is a process diagram showing an embodiment of a method of manufacturing an internal magnetic shield of a picture tube according to the present invention. FIG.

FIG. 2 is a step diagram of a step diagram showing an embodiment of a method of manufacturing an internal magnetic shield of a picture tube according to the present invention. FIG.

FIG. 3 is a step diagram of a step diagram showing an embodiment of a method of manufacturing an internal magnetic shield of a picture tube according to the present invention. FIG.

FIG. 4 is a flow chart showing step 4 of the process diagram showing the embodiment of the method of manufacturing the internal magnetic shield of the picture tube according to the present invention. FIG.

FIG. 5 is a flow chart showing step 5 of the process diagram showing the embodiment of the method of manufacturing the internal magnetic shield of the picture tube according to the present invention. FIG.

FIG. 6 is an explanatory diagram for explaining the shape of the plate material pressed in FIG.

FIG. 7 is a schematic configuration diagram showing an embodiment of a picture tube incorporating an internal magnetic shield to which the present invention is applied.

FIG. 8 is a perspective configuration diagram showing a state in which an internal magnetic shield to which the present invention is applied is attached to a mask frame.

[Explanation of symbols]

4 ... Mask frame, 5 ... Internal magnetic shield, 20 ... Bend line, 26 ... Bend side, 200 ... Notch, 300 ... Notch

Claims (1)

[Claims] 1. A method for manufacturing a magnetic shield, which is formed by assembling a plurality of bent plate members, each of which is composed of a truncated pyramid-shaped cylindrical portion positioned on the inner wall side of a picture tube and closed on the electron gun side. An internal magnetic shield for a picture tube comprising a step of bending each side part positioned on both sides of a part intersecting with a bending line which is a bending part in a side part of the plate member, and then bending the side part along the bending line. Manufacturing method.