JP2522421B2 - Shadow mask molding method and molding apparatus - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shadow mask molding method for molding a shadow mask of a color cathode ray tube and a shadow mask molding apparatus for carrying out this method.

[Conventional technology]

Conventionally, a shadow mask of a color cathode ray tube is fixed in a glass panel and has a function of defining correspondence between an electron beam emitted from an electron gun and a phosphor. Further, the shadow mask material plate is provided with a large number of slot-shaped holes as shown in FIG. 8A and round holes as shown in FIG. 8B by photoetching or the like. This shadow mask material plate has a predetermined spherical shape by press molding.

On the other hand, as shown in FIG. 9, a shadow mask forming apparatus generally includes a punch 1 having a spherical surface portion to which a spring back of a material is added in order to form a shadow mask spherical surface and a side wall portion for determining an outer peripheral shape. A blank holder 2 located on the outer peripheral side of the punch 1 is arranged, and a pad 3 having a part of the surface facing the punch 1 or the peripheral part thereof is the same as the spherical surface part of the punch 1 in the lower part, and the pad 3. A die 4 is disposed on the outer peripheral side of the die 3 so as to face the blank holder 2 and clamps a shadow mask material plate (not shown) together with the blank holder 2. Further, the blank holder 2 and the die 4 are provided with a bead portion or a stepped portion (not shown) in order to enhance the clamping force to the shadow mask material plate.

The spherical shape of the punch 1 is generally expressed by a mathematical expression, and a part of the spherical surface represented by the mathematical expression similar to the punch 1 or a functional expression continuous with the spherical surface of the punch is partially present on the surface of the blank holder 2 facing the die 4. Or it is provided over the entire area. Further, the same spherical surface as the blank holder is provided on the surface of the die 4 facing the blank holder 1.

Next, a method for forming the shadow mask will be described with reference to FIGS. 10 to 13.

First, the blank holder 2 descends, and the peripheral portion of the shadow mask blank 5 placed on the lower mold is clamped by the blank holder 2 and the die 4 as shown in FIG. Then, the punch 1 descends to start the spherical projection of the shadow mask material plate 5. Then, as shown in FIG. 11, overhanging is performed until the punch 1 reaches the upper surface of the pad 3 to form the shadow mask spherical surface portion 5a.

Next, the punch 1 continues to descend together with the pad 3 after contacting with the pad 3, and at the same time the die 4 descends, but the blank holder 2 is fixed by a height gauge (not shown) and does not descend. As shown, the clamp on the peripheral portion of the shadow mask material plate 5 is released.

After that, even if the die 4 reaches the bottom dead center and stops, the punch 1 and the pad 3 continue to descend further, and as shown in FIG. 13, the shadow mask skirt portion 5b is formed between the side walls of the die 4 and the punch 1. Are formed by drawing and bending. Thus, after the above-mentioned molding, the punch 1, the blank holder 2, the pad 3 and the die 4 are lifted to obtain the shadow mask 6 that has been molded.

When clamping the peripheral portion of the shadow mask material plate 5 with the blank holder 2 and the die 4 during the above-mentioned overhanging process, it is necessary to clamp over the entire outer circumference, so when the blank holder 1 and the die 4 are superposed, Matching is performed in the peripheral portion where the shadow mask material plate 5 is clamped.

Therefore, the clearance formed between the blank holder 2 and the die 4 during drawing is uniform over the entire circumference.

As shown in FIG. 14, the shadow mask 6 has side portions 6a and corner portions 6b, and has a shape close to a rectangle. The side portion 6a is generally made to have a size of R3000 (mm) to straight, and in the step of forming the shadow mask skirt portion 5b, the bending element occupies a larger proportion than the drawing element in the step of forming the shadow mask skirt portion 5b. The corner 6b is generally R10.
The size is about 50 mm, and a pure drawing process is performed in the step of forming the shadow mask skirt portion 5b.

In the drawing process, if the clearance between the blank holder 2 and the die 4 is large, the material can move freely, so
As shown in Fig. 15, there is a thickness deviation, and that part is squeezed by the punch 1 and the die 4 and unnecessary stress is generated in the shadow mask 6, the spherical surface is deformed, and the ironing part is cracked. , Breakage may occur. In the bending process, the portion indicated by reference numeral C in FIG. 16 is the place where the processing is required, and the shoulder portion of the punch 1 and the shoulder portion of the die 4 are processed here. If the clearance between the blank holder 2 and the die 4 is small during bending, the movement of the material is restricted, so
As shown in FIG. 17, the shadow mask skirt portion 5b is continuously bent by the shoulder portion of the die 4 as indicated by reference numeral D.

Shadow mask skirt that has been continuously bent
5b is curled outward due to the influence of springback, as indicated by reference character E in FIG. If the shadow mask skirt portion 5b curls outward, the shadow mask spherical surface portion 5a is deformed by the reaction force as shown by the symbol F in FIG. 18, which causes a decrease in the color purity of the color CRT. turn into.

In recent years, with the improvement of brightness of color cathode ray tubes,
There is an active movement to use an Invar material, which has a small thermal deformation, as a shadow mask material. However, since the Invar material is a high-strength material, the amount of springback generated is 4 to 5 times larger than that of the conventional one. Curling of the shadow mask skirt and deformation due to curling have become a serious problem.

[Problems to be Solved by the Invention]

Since the conventional shadow mask forming method is performed as described above, in the drawing process of the shadow mask 6, the clearance between the blank holder 2 and the die 4 is made small in order to prevent cracks and breakage of the corner portion 6b. Therefore, curl of the shadow mask skirt portion 5b which occurs because the clearance is small in the side portion 6a where it is preferable that the clearance is large cannot be suppressed, and when the both are compromised, the clearance can be adjusted. There was a problem that it took a lot of time.

The present invention has been made to solve the above-described problems, and it is possible to obtain good molding conditions for both the corner portion and the side portion in the molding of the shadow mask skirt portion, and to prevent deformation and breakage. An object of the present invention is to obtain a shadow mask molding method and molding apparatus.

[Means for solving the problem]

A shadow mask forming method according to the present invention comprises a step of forming a curved surface while pressing and clamping an outer peripheral portion of a shadow mask material plate which is a part of a side wall of the shadow mask, and an outer peripheral portion of the protruding curved surface. Or clamping the entire area, releasing the pressing clamp during the overhanging step, and drawing the side wall of the shadow mask in a state where a clearance for moving the outer peripheral portion of the shadow mask material plate is formed, The clearance formed in the pressing clamp portion in the drawing step is set so that the corner portion of the shadow mask is smaller than the other side portions.

Further, the shadow mask forming apparatus according to the present invention is
A blank holder that presses the peripheral portion of the shadow mask material plate, a die that faces the blank holder and holds the outer peripheral portion of the shadow mask material plate, and a shadow mask that slides in the blank holder and the die. A punch for forming a predetermined curved surface portion and a skirt portion on the material plate, and a pad that holds the shadow mask material plate on a part or all of the surface facing the punch and slides in the die. In the shadow mask forming device, the shadow mask holding surface of the blank holder or the die has a corner portion divided with respect to the other side portions, and the divided holding surface is a shadow mask material plate. When holding, the divided holding surface was positioned like a continuous surface, and the holding of the shadow mask material plate was released. To are those as holding surfaces of the corner portions that are the divided protrudes than the other of the holding surface.

[Work]

In the molding method of the present invention, in the molding of the shadow mask side wall portion, the clearance between the blank holder and the die is set so that the corner portion is smaller than the other side portions. The clearance is small and it is possible to prevent the shadow mask material plate from leaning, and at the side that is mainly the bending process, the clearance between the blank holder and the die is large and the shadow mask material plate is continuous. Bending can be prevented.

Further, in the molding apparatus of the present invention, the corner portion of the shadow mask holding surface of the blank holder or the die is divided with respect to the other side portions, and the divided holding surface holds the shadow mask material plate. When the holding surface is divided so as to be a continuous surface, when the holding of the shadow mask material plate is released, the holding surface of the divided corner portion is more than the other holding surface. Since it is projected, the clearance between the blank holder and the die is smaller in the corner portion than in the side portion when the shadow mask side wall portion is formed,
It is possible to suppress the leaning of the corner portion and the curling of the side wall portion of the side portion.

〔Example〕

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view taken along diagonal corners of a shadow mask forming apparatus according to the present invention.
Is a punch having a spherical surface portion in which a spring back of the material is added to form the spherical surface of the shadow mask and a side wall portion that determines the outer peripheral shape, 2 is a blank holder located on the outer peripheral side of the punch 1, 21 is a blank holder 2 A corner sliding part attached to a corner part, 3 is a pad arranged below the punch 1 so as to be opposed thereto, and 4 is arranged so as to oppose the blank holder 2 on the outer peripheral side of the pad 3 and clamps the shadow mask material plate together with the blank holder 2. It is a die that does.

Here, as in the conventional shadow mask forming apparatus described with reference to FIG. 9, surfaces 1a and 3 of the punch 1 and the pad 3 which face each other are opposed to each other.
a and the surfaces (a shadow mask holding surfaces) 2a and 4a of the blank holder 2 and the die 4 which face each other have the same curved surface shape, and the blank holder 2 according to the present invention is used.
The surface (divided holding surface) 21a of the corner sliding portion 21 facing the die 4 provided on the above has the same curved surface shape as the surface 4a of the die 4. The side portions of the blank holder 2 other than the corner portions have the same structure as that shown in FIG.

Further, the corner sliding portion 21 is engaged with a dovetail groove 2b formed in a corner portion of the blank holder 2 as shown in FIG. 2, and is pressed by a spring 22 accommodated in the bottom of the dovetail groove 2b to be blanked. It projects from the surface 2 a of the holder 2.

Next, the shadow mask molding method according to the present invention will be first described.
A description will be given using the device shown in the figure. When the molding apparatus has X-axis, Y-axis, diagonal axis and Z-axis as shown in FIG. 3, (a) in FIGS. 4 to 7 shows the diagonal axis (corner portion) of the apparatus. A cross-sectional view is shown, and (b) shows a cross-sectional view along the X-axis or the Y-axis (side portion).

First, the blank holder 2 descends, and the peripheral portion of the shadow mask material plate 5 placed on the lower mold is clamped by the blank holder 2 and the die 4 as shown in FIGS. To be done. At this time, in the corner sliding portion 21, the spring 22 is compressed and the surface 21a of the corner sliding portion 21 has the blank holder 2
The blank holder 2 and the die 4 clamp the shadow mask blank 5 over the entire circumference because the blank holder 2 and the die 4 are pushed into the same plane as the surface 2a.

Next, the punch 1 descends and hits the shadow mask material plate 5 to start spherical projection. Then, as shown in FIGS. 5A and 5B, the punch 1 is formed on the upper surface of the pad 3.
Is subjected to overhanging until they contact each other through the shadow mask material plate 5, and a shadow mask spherical surface portion 5a is formed.

Next, the punch 1 continues to descend after coming into contact with the pad 3, and the die 4 descends accordingly, but the blank holder 2 is fixed by a height gauge (not shown) and does not descend. As shown in (a) and (b), a clearance is formed between the die 4 and the blank holder 2. At this time, the corner sliding portion 21 of the blank holder 2 is
Since it is pushed to the die 4 side by the spring pressure of the spring 22, the surface 21a of the corner sliding portion 21 is closer to the die 4 side than the surface 2a of the blank holder 2 as shown in FIG. 6 (a), The clearance formed between the die 4 and the corner sliding portion 21 of the blank holder 2 is set smaller than the clearance formed between the die 4 and the blank holder 2.

Next, even after the die 4 reaches the bottom dead center and stops, the punch 1 and the pad 3 continue to descend, and
As shown in FIGS. (A) and (b), the shadow mask skirt portion 5b is formed between the side wall of the punch 1 and the side wall of the die 4, but at that time, the clearance is small at the corner sliding portion 21 of the blank holder 2. Therefore, when the material flows in, resistance is generated, and the material is prevented from being leaned as shown in FIG. 15, and the material flows in because there is a large clearance in the place without the corner sliding portion 21. The bending force generated at this time is generated only at the point C in FIG.
The corner point D does not require continuous bending force. Thus, after the above molding, punch 1, blank holder
2, the pad 3 and the die 4 are raised in this order to obtain a shadow mask 6 that has been formed.

A test was conducted using the 21-inch size shadow mask 6 in the above-mentioned embodiment.
Clearance of 6b is less than 0.15mm thickness of the shadow mask material plate 5 with thickness less than + 0.1mm. Met. In addition, the shadow mask material plate 5 provided with beads or the like on the peripheral portion to be clamped to increase the resistance was in a practical range up to a plate thickness of +0.1 mm.

Furthermore, the spring back of the side part 6a increases rapidly when the clearance is reduced to + 0.3mm or less, but + 3.0mm.
At clearances of mm or more, the difference in springback amount due to the clearance did not appear significantly. By the way, as the amount of spread of the shadow mask skirt 5b,
Clearance + 0.5mm when skirt length is 12mm
When the value was 2.5 mm, the method and apparatus according to the present invention was adopted, and the clearance could be set to +3.0 mm to reduce the clearance to 1.3 mm. The deformation of the part 5a was also eliminated.

In the above embodiment, the blank holder 2 has a corner sliding portion 21.
However, the corner sliding portion may be provided on the die 4. In addition to the spring 22, a pressure generator such as hydraulic pressure may be used as the pressing force of the corner sliding portion 21. Further, although the corner sliding portion 21 is housed in the blank holder 2, it may be separated from the blank holder 2.

〔The invention's effect〕

As described above, according to the present invention, in forming a shadow mask skirt portion, resistance is generated when a material flows in a corner portion having a high specific gravity for drawing, and a material is used for a side portion having a high specific gravity for bending. Since it was set so that resistance does not occur when flowing in, it is possible to give an appropriate situation in the processing state, and thereby it is possible to mold a shadow mask with less distortion, leaning or breaking The effect is obtained.

Further, as a molding device, since it is only necessary to add a simple device to the conventional device, there is an effect that it can be provided at low cost.

[Brief description of drawings]

FIG. 1 is a sectional view of a shadow mask molding apparatus according to an embodiment of the present invention, FIG. 2 is an enlarged sectional view showing a corner sliding portion of FIG. 1, and FIG. 3 is an explanation of coordinate axes in the molding apparatus of the present invention. FIGS. 4 to 7 are process diagrams of forming a shadow mask according to the present invention, FIGS. 8 (a) and 8 (b) are diagrams of hole shapes punched in a shadow mask material plate, and FIG. 10 to 13 are sectional views of a conventional shadow mask forming process, FIG. 14 is an outline view of a shadow mask, and FIG. 15 is a perspective view of a corner portion of a shadow mask in which a thickness shift occurs. Fig. 16 is a diagram of the portion of the shadow mask that needs to be bent, Fig. 17 is a diagram of the shadow mask in which the bending force is continuously generated, and Fig. 18 is springback. The wider skirt shape and It is a diagrammatic view of the spherical portion. 1 ... Punch, 2 ... Blank holder, 3 ... Pad,
4 ... Die, 5 ... Shadow mask material plate, 21 ... Corner sliding part, 22 ... Spring. The same reference numerals in the drawings indicate the same or corresponding parts.

Claims (2)

(57) [Claims] 1. A step of overhanging a curved surface in a state where an outer peripheral portion of a shadow mask material plate which is a part of a side wall of a shadow mask is pressed and clamped, and the outer peripheral portion or the entire area of the overhanging curved surface is clamped and held. A step of drawing the side wall of the shadow mask in a state in which a pressure clamp is released during the overhanging step and a clearance for moving the outer peripheral portion of the shadow mask material plate is formed,
A method for forming a shadow mask, characterized in that the clearance formed in the pressing clamp portion in the drawing step is set so that the corner portion of the shadow mask is smaller than the other side portions. 2. A blank holder for pressing a peripheral portion of a shadow mask material plate, a die which faces the blank holder and holds an outer peripheral portion of the shadow mask material plate, and the blank holder and the inside of the die. A punch for sliding to form a predetermined curved surface portion and a skirt portion on the shadow mask material plate, and the shadow mask material plate is held by a part or all of the surface facing the punch and slid in the die. In the shadow mask forming device including a moving pad, the shadow mask holding surface of the blank holder or the die is divided into corner portions with respect to other side portions, and the divided holding surface is When holding the shadow mask material plate, the divided holding surface is positioned so as to be a continuous surface. Molding apparatus of the shadow mask, characterized in that as the holding surfaces of the corner portions that are the divided protrudes than the holding surface the other when releasing the holding.