JPS6114025A - Formation of shadow mask for color cathode ray tube - Google Patents

Abstract

PURPOSE:To form the titled shadow mask with good accuracy safely by forming a spherical surface part with an inner punch and knock-out after pinching the peripheral part of a mask material with a blank holder and die and then by forming an annular rib part around the spherical surface part with an outer punch and knock-out. CONSTITUTION:A punch 12 is divided into the inner punch 12a forming a spherical surface part C and a punch 12b forming an annular rib part R. First, then, a spherical surface part C forming numerous holes for electron beam passing through is formed by the punch 12a and knock out 15 and the bulging quantity K of the raw material M of the mask is adjusted. The annular rib part R is then formed by the outer punch 12b and knock out 15 with pinching the spherical surface part C by the punch 12a and knock out 15. With said method the shadow mask without the cut of an electron beam passing light and the deformation can be formed by not only the carbon steel used conventionally but also a high tensile steel, for instance, even the material having bad formability of an invar material, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method for forming a color cathode ray tube shadow mask.

[Technical background of the invention and its problems]

A shadow mask type color cathode ray tube is provided with a shadow mask inside the front surface of the tube, which controls an electron beam emitted from an electron gun, facing a phosphor screen formed inside the front surface thereof.

This shadow mask is made by forming a large number of electron beam passing holes in a thin steel plate by photo-etching, and then shaping the mask material so that the part where the electron beam holes are formed is shaped into a spherical shape, and a frame is formed around it. In order to prevent the curved surface of the spherical surface from changing during this molding process, an annular skirt is formed around one spherical surface (C) as shown in FIGS. 3(A) and 3(B). There is one in which a rib portion (R) is formed, and a skirt portion (S) is formed on the outside of the rib portion (R).

Conventionally, this shadow mask has a molded surface (1) having the same shape as the curved surface of the shadow mask, as shown in FIG. 4(A).
A punch (2) with a shape and a forming surface (1) of this punch (2)
A knockout (4) with a molding surface (3) of a shape corresponding to
), the mask material (M) is inserted between the blank holder (5) and the die (6), and then the punch (2) is inserted as shown in FIG. 4(B). was advanced, and the mask material (M) was pressed and formed by the punch (2) and the knockout (4). However, when a ribbed shadow mask is formed using the mold, the mask material ( The periphery of M) includes protrusions (7), (8) of punch (2) and knockout (4), and die (
Because the center part side where the electron beam passage hole is formed is squeezed or bent at the corners (9) of 6), the electron beam passage hole may be stretched and deformed, and due to this elongation. It has the disadvantage of being cut into pieces, and of changing the curved surface of the shadow mask.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for molding a color cathode ray tube shadow mask, which accurately and stably produces a ribbed CRT shadow mask.

[Summary of the invention]

The punch for forming the shadow mask consists of an inner punch with a forming surface in the same shape as the spherical surface of the ribbed shadow mask, and an outer punch with a forming surface in the same shape as the annular rib. After the peripheral part of the mask material in which the beam passage hole is formed is held between a blank holder and a die, a spherical surface part is first formed using an inner punch and a knockout, and then a spherical surface part is formed using an outer punch and a knockout.
An annular rib portion is formed around the spherical surface portion.

[Embodiments of the invention]
fart.

Hereinafter, the present invention will be described based on embodiments with reference to the drawings.

First, the mold for forming the shadow mask will be described.

As shown in Figure 2, the molds are an upper mold (10) and a lower mold (1
1), the upper mold (10) has a punch (12),
A blank holder (13) is arranged closely and coaxially on the outside of this punch (12), and an upper die set (13) that supports these punches (12) and blank holders (13).
14). The lower die (11) also includes a knockout (15), a die (16) coaxially arranged closely outside the knockout (15), and a lower die that supports the knockout (15) and the die (16). It consists of a mold die set (17). In particular, the punch (12) of the upper die (10) is an inner punch (12a) having a forming surface (19) having the same shape as the spherical surface portion (C) of the shadow mask.
and an outer punch (12b) having a molding surface (20) of the same shape as the annular rib portion (R) of the shadow mask.
b) is slidably attached to the concave hole (21) formed on the molding surface side and coaxially with the outer punch (12b), and the molding is performed by a spring member (not shown) provided in the concave hole (21). The surface side protrudes from the forming surface (20) of the outer punch (12b) when no load is applied, and both forming surfaces (19), (2
A step with a constant height h is formed between 0) and when a load is applied to this inner punch (12a), this step disappears and both molding surfaces (19) and (20) are continuous, forming a curved surface of the shadow mask. It is now possible to make the same curved surface as. Knockout (1) for this punch (12)
5) have the same shape as the curved surface of the shadow mask, that is, double punches (12a) and (12b) when the step is eliminated.
) is formed as an integral body with a molding surface (22) corresponding to the continuous molding surface of the molding surface (22).

In forming the shadow mask, the lower mold (11) is mounted on the press table of a press molding device, and the upper mold (10) is attached to the lower mold (11) on a movable part that moves forward and backward with respect to the press table using, for example, hydraulic pressure. This is done by installing it coaxially with the Note that the height of the knockout (15) of the lower mold (11) with respect to the die (16) is determined by the knockout spacer (
25).

In addition to the press molding equipment that moves the movable parts using hydraulic pressure, there are 1. It may be moved by gas or by a mechanism such as a crank.

Next, a method for forming a shadow mask will be explained with reference to FIG. First, as shown in Figure (A), the movable part is moved back to the top dead center to separate the upper mold (10) from the lower mold (11), and then the mask material is placed in a fixed position on the lower mold (11). CM) and place it there. After that, move the upper die (10) forward as shown in figure CB) and press the blank holder (13).
The periphery of the mask material (M) is held between the mask material (M) and the die (16). Afterwards, move the punch (12) forward and press (
Both the inner punch (12a) and the outer punch (12b) move forward) The forming surface (19) of the inner punch (12a) knocks out the central part of the mask material (M) (15
) side, and as shown in figure (C), this overhanging part is attached to the molding surface (19) of the inner punch (12a).
) and the molding surface (22) of the knockout (15) to mold the central part of the mask material (M) into a spherical shape. In the molding of the central part of this mask material (M), the amount of overhang by the inner punch (12a) is limited to the knockout (1) by the knockout spacer (25).
5) This is done by changing the height of. Further, the molding surface (20) of the inner punch (12a) is located at a position retreating from the molding surface (19) of the inner punch (12a) and is away from the mask material (M).

When the mask material (M) is pinched between the inner punch (12a) and the knockout (15), the blank holder (13) is slightly retracted just before that, as shown in figure (D), and the mask material is It is recommended to loosen the grip around the periphery of (M). (Assuming that the thickness of the mask material (M) is t, t<"ri) Next, following the formation of the spherical surface part (C) by the inner punch (12a) and the knockout (15), this inner punch ( 12a
) and the knockout (15), the outer punch (12b) is advanced as shown in figure (E), and at the same time the blank-holder (
13) is moved back to sufficiently release the peripheral part of the mask material (M), the skirt part (S) is drawn (TI<T2), and further advanced as shown in the figure CF). The forming surface (20) of the outer punch (12b) and the forming surface of the knockout (15) allow the ask material to be
1. Press the peripheral portion of (M) to form an annular rib portion (R) on the outside of the spherical surface portion (C). Thereafter, by retracting the upper die (10) together with the movable part, the desired shadow mask can be taken out.

As described above, the punch (12) is divided into the inner punch (12a) for forming the spherical surface portion (C) and the outer punch (12b) for forming the annular rib portion (R), and first the inner punch (12a) is By knockout (15).

After molding the spherical surface part (C) in which a large number of electron beam passage holes are formed, by adjusting the overhang amount k of the mask material (M), the spherical surface part (C) can be formed by keeping the elongation of the electron beam passage holes constant. Can be molded.

Also, after that, this spherical surface part (C) was punched with an inner punch (12
Since the annular rib portion (R) is formed by the outer punch (12b) and the knockout (15) while being pressed by the outer punch (12b) and the knockout (15), the rib portion (R)
It was possible to prevent the elongation or breakage of the electron beam passage hole and the deformation of the spherical surface portion (C) that would otherwise occur due to this. Therefore, when forming a shadow mask using this forming method,
It is possible to form a shadow mask with no cut or deformation of the electron beam passage hole, not only with conventionally used carbon steel but also with materials with poor formability such as high tensile strength steel such as invar material.

Although this invention has been described above with reference to one embodiment, this invention is not limited to the above embodiment.

For example, in the above embodiment, the inner punch is pressurized via the spring member provided in the recessed hole of the outer punch, but the inner punch and the outer punch are constructed to be pressurized independently using, for example, hydraulic pressure. But that's fine.

〔Effect of the invention〕

(1) The punch used to form the shadow mask is divided into an inner punch and an outer punch, and the inner punch and knockout form a spherical surface with many electron beam passage holes. By adjusting the amount of overhang of the mask material, it became possible to form a spherical surface with a constant elongation of the electron beam passage hole.

(2) The annular rib portion is formed by the outer punch and knockout while the inner punch and knockout keep the thyroid surface portion in which the electron beam passage hole is formed, so that the electron beam passage hole does not stretch or break. , and deformation of the spherical surface portion could be prevented.

[Brief explanation of drawings]

Figures 1 (A) to (F) are process diagrams for explaining an embodiment of the present invention, Figure 2 is a sectional view of a mold used in an embodiment of the present invention, and Figure 3 (A). ) and (8) are a plan view and a partially cutaway sectional view of the shadow mask, respectively.
FIGS. 4(A) and 4(CB) are process diagrams for explaining a conventional shadow mask forming method. (C)... Spherical surface part (R)... Rib part (S)... Skirt part (M)... Mask material (10)... Upper mold (11)...
・Lower die (12)...Punch (12a)
... Inner punch (12b) ... Outer punch
(13) Blank holder (15) Knockout
(16) Die (19) Inner punch forming surface (20) Outer punch forming surface (22) Knockout forming surface Fig. 1 (β) Fig. 1 . (Dn?? (L) wJ2 Figure 3 (fl)

Claims (2)

[Claims] (1) A punch for forming a shadow mask having an annular rib part around a spherical surface part: an inner punch having a forming surface of the same shape as the spherical surface part, and an outer punch having a forming part of the same shape as the annular rib part. After sandwiching the periphery of the mask material between a blank holder and a die, the mask material is formed into a molding surface having a molding surface of the same shape as the curved surface of the inner punch and the shadow mask and arranged coaxially with the punch. The spherical surface portion of the shadow mask is formed by pinching with the knockout, and then the mask material is pinched with the outer punch and the knockout while maintaining the pinching pressure between the inner punch and the knockout to form the spherical surface portion of the shadow mask. A method for forming a color cathode ray tube shadow mask, which is characterized by forming an annular rib portion around the circumference. (2) The color cathode ray tube shadow mask according to claim 1, characterized in that when the mask material is pinched by the inner punch and the knockout, the peripheral portion of the mask material is released from being held by the blank holder and the die. Molding method.