JP2001246646A - Injection mold - Google Patents

Abstract

PROBLEM TO BE SOLVED: To certainly release a molded article from a mold on a release side in an injection mold wherein a part is injection-molded by a fixed mold and a movable mold. SOLUTION: The surface roughness of the molding surface of the movable mold 32 on a side having to release the molded article among the fixed mold 31 and the movable mold 32 is mage larger than that of the molding surface of the fixed mold 31 on a side having to allow the molded article to remain to certainly release the molded article from the fixed mold 32.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mold for injection molding, and more particularly, to a mold for opening a mold so that a molded article remains on a predetermined side of a movable mold or a fixed mold. And a mold for injection molding.

[0002]

2. Description of the Related Art In general, in audio equipment and video equipment, a magnetic tape cassette for recording and reproducing data by holding a magnetic tape wound around a pair of tape reels movably in a cassette case is often used. . On the other hand, a computer (one reel type) in which a single tape reel around which a magnetic tape is wound is rotatably supported in a cassette case is used.

FIG. 3 is an exploded perspective view of a digital video cassette (DVC) which is an example of a magnetic tape cassette. The magnetic tape cassette 70 includes an upper cassette half 71 and a lower cassette half 72, each having a flat plate and a peripheral wall, and a pair of tapes formed by welding an upper flange 73a and a lower flange 73b in the lower cassette half 72. The reel is rotatably supported. A magnetic tape 76 is wound around a hub 75 formed integrally with the lower flange 73b of these tape reels. Further, engaging teeth 74 are formed on the outer periphery of the lower flange 73b of the tape reel.

A tape guide 81 is provided on both sides of an opening 80 on the front end side (front side in the figure) of the lower cassette half 72.
Is provided. Each tape guide 81 guides the magnetic tape 76 sent out from one tape reel and wound on the other tape reel, and passes the magnetic tape 76 at a predetermined position in the opening 80.

[0005] A tape reel lock member 82 having a pair of tape reel locking arms 82a is attached to the lower cassette half at the rear end side (the back side in the figure). The tape reel lock member 82 is urged by the compression coil spring 83 so that the tape reel locking arm 82a is engaged with the engaging teeth 7 formed on the outer periphery of the lower flange of each tape reel.
4 to prevent unexpected rotation of each tape reel. Thereby, loosening of the magnetic tape 76 and the like are prevented.

The flat plate of the upper cassette half 71 has a plate spring 85 for urging the reel formed by bending a band-shaped metal plate.
Is provided for each tape reel. The leaf spring 85 for biasing the reel is cantilevered by the upper cassette half 71 and biases the corresponding tape reel toward the lower cassette half 72. An opening is provided in the flat plate of the upper cassette half 71 so that the winding amount of the magnetic tape 76 on the tape reel can be checked, and a transparent window member 8 is closed so as to close the opening.
6 are provided.

The upper cassette half 71 has a magnetic tape 7 stretched between a pair of tape guides 81 of the lower cassette half in order to obtain dustproofness that can withstand outdoor use.
An outer lid 86, an upper lid 87, and an inner lid 88, which cover the front and back surfaces of 6, respectively, are provided to be freely openable and closable.

When such a magnetic tape cassette 70 is loaded into a recording / reproducing device or the like (not shown), the reel lock member 82 slides backward (in the direction of compressing and compressing the compression coil spring 83) by an engagement release pin provided in the device. Then, the engagement between the locking arm 82a and the engagement teeth 74 is released, and the tape reel can rotate.

The above and below cassette halves 71, 7
2, the outer lid 86, the upper lid 87 and the inner lid 88, and the upper and lower flanges 73 of the tape reel.
a, 73b, window member 86, etc. are formed by injection molding, respectively. In addition, a member formed by injection molding is appropriately used for the magnetic tape cassette 70.

FIG. 4 shows a conventional injection molding die for molding the window member 86. As shown in FIG.
The conventional injection mold 22 includes a fixed mold 23, a movable mold 24, a projecting means (not shown), and the like.
A cavity 26 is formed in the movable mold 24 to form a molded product 25. The fixed mold 23 is attached to the movable mold 24 while the molded product 25 is in close contact with the cavity 26 of the movable mold 24. From the molding surface 23a of
The molded product 25 is protruded from the movable mold 24 and released from the movable mold 24 by a protruding means (not shown) provided in the movable mold 24.

[0011]

As described above, in the injection mold 22, the movable mold 24 or the fixed mold 2 is used.
It is important that the molded article 25 is left on a predetermined side of any one of the three.

However, due to the injection mold 22,
In the case of molding a glossy molded product 25 on the surface such as the window member 86, as shown in FIG. 5, the molded product 25 adheres not to the movable mold 24 but to the molding surface 23 a of the fixed mold 23. May remain. In this case, since the remaining molded product 25 is manually released from the mold, the production process must be temporarily stopped. In addition, when the mold is manually released, the molded product 25 may be unnecessarily bent, causing local stress concentration and deformation such as whitening.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems, and when a mold is opened, a molded product can be reliably left on a fixed side of a movable mold or a fixed mold. An object of the present invention is to provide a mold for injection molding that does not impair the quality.

[0014]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an injection molding mold for injection-molding a part using a fixed mold and a movable mold. Injection molding characterized in that the surface roughness of the molding surface of the mold on the side from which the product is to be released is greater than the surface roughness of the molding surface of the mold on the side on which the molded product is to remain when the mold is opened. Achieved by the mold.

The present invention is particularly suitable for molding a molded product having relatively smooth front and back surfaces, such as a molded product having gloss on both surfaces.

In the present invention, the desired range of the surface roughness of the molding surface of the mold on the side where the molded product is to be left varies depending on the material of the resin, molding conditions, and the like. It is 0.05 μm or less, preferably Ra is 0.01 μm to 0.03 μm, and particularly preferably Ra is 0.01 μm to 0.02 μm. The desired range of the surface roughness of the molding surface of the mold on the side from which the molded product is to be released also varies depending on the material of the resin, molding conditions, and the like, but the center line average roughness Ra is approximately 0.1 μm or more.
0.5 μm, preferably Ra is 0.1 μm to 0.1 μm.
3 μm, particularly preferably Ra is 0.1 μm to 0.2 μm
It is. In the present invention, the difference in roughness between the two dies is 0.05 μm to 0.45 μm in terms of center line average roughness Ra, preferably Ra is 0.08 μm to 0.2 μm, and particularly preferably Ra is 0.5 μm to 0.2 μm. 08 µm to 0.19 µm.

[0017]

In the above construction, if the surface roughness of the molding surface of the mold on which the molded product is to be released is made larger than the surface roughness of the molding surface on which the molded product is to be retained, the molded product is left. The friction coefficient of the molding surface of the mold on the side to be molded is higher than the friction coefficient of the molding surface of the mold on the side where the molded article is to be released. This ensures that the molded product remains on the molding surface of the mold on the side where the molded product is to remain. The reason why the friction coefficient of the molding surface of the mold on the side from which the molded product is to be released is increased is that the smoothness of the molded surface is extremely high, so that the close contact with the molded product is enhanced.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIG.
This will be described in detail with reference to FIG. FIG. 1 shows an injection molding die for molding the window member 86 as a molded product having gloss on both sides, and FIG. 2 shows a mold opening process of the injection molding die.

As shown in FIG. 1, an injection mold 30 is provided.
Is composed of a fixed mold 31, a movable mold 32, and a projecting means (not shown). The movable mold 32 is formed with a concave cavity 34 for forming a molded product 33 as the window member 20. Further, when the mold is opened, the cavity 34 of the movable mold 32 is A projecting means for projecting and releasing the molded product 33 from the mold is provided.

The inventor of the present application proposes that when the surface roughness of the molding surface 31a of the fixed mold 31 and the cavity 34 of the movable mold 32 are relatively small and the surface roughness of It was found that the molded product remained on the smooth side with small size. Based on this finding, the surface roughness of the molding surface 31a of the fixed mold 31 is changed to the cavity 3 of the movable mold 32.
4 is rougher than the surface roughness. Of course, in this case, the fixed mold 31 has a cavity (not shown).
Is formed, the cavity of the fixed mold 31 has a rough surface over the entire surface.

For this reason, as shown in FIG.
However, even if the front and back surfaces have gloss on both sides as in the case of the window member 86, the molded product 33 adheres strongly to the cavity 34 of the movable mold 32 having a high friction coefficient, and the molded product 33 is fixed to the fixed mold 31.
From the molding surface 31a or the cavity of the fixed mold 31.

Therefore, the molding surface 31a of the fixed mold 31
Is prevented, the production process is temporarily stopped due to unexpected adhesion, and deformation of the molded product 33 is prevented.

The molding surface of the fixed mold 31 is, for example, abrasive diamond paste (trade name) product number # 15 manufactured by Ryoko Sangyo Co., Ltd.
By polishing with 00, a desired surface roughness is obtained. Further, the molding surface of the movable mold 32 is polished using, for example, an abrasive diamond paste (trade name) product number # 3000 manufactured by Ryoko Sangyo Co., Ltd., so that the desired molding surface is smoother than the molding surface of the fixed mold 31. Finished to surface roughness.

In this embodiment, the movable mold 3
2 has been described in which the molded article 33 is brought into close contact with the mold 2 and the molded article 33 is released from the fixed mold 31. However, in some cases, the molded article 33 is released from the cavity 34 of the movable mold 32, and It is also assumed that the molded article 33 is left on the molding surface 31a. In such a case, contrary to the above, the surface roughness of the cavity 34 of the movable mold 32 is increased over the entire surface, and the molding surface 31a or the cavity of the fixed mold 31 is extended over the entire surface. Correspondence shall be made with smooth roughness.

[0025]

According to the present invention, of the fixed mold and the movable mold, the surface roughness of the molding surface of the mold on the side from which the molded product is to be released when the mold is opened is determined by measuring the molded product when the mold is opened. By making the surface roughness of the molding surface of the mold to be left larger than the surface roughness of the molding surface, the molded product remains on the molding surface of the mold where the molded product is to remain. Deformation can be prevented.

[Brief description of the drawings]

FIG. 1 is a sectional view of an injection mold according to an embodiment of the present invention.

FIG. 2 is a process diagram showing a mold opening state of an injection mold according to an embodiment of the present invention.

FIG. 3 is an exploded perspective view showing a structure of a magnetic tape cassette in which main parts are molded by an injection mold.

FIG. 4 is a cross-sectional view of a conventional injection mold.

FIG. 5 is a process chart showing a mold opening state of a conventional injection mold.

[Explanation of symbols]

 31 Fixed mold 32 Movable mold 33 Molded product 86 Window member

Claims (1)

[Claims] 1. An injection molding mold for injection-molding a part by a fixed mold and a movable mold, wherein, of the fixed mold and the movable mold, one of the molds on which a molded product is to be released when the mold is opened. An injection mold, wherein the surface roughness of the molding surface is made larger than the surface roughness of the molding surface of the mold on the side where the molded product is to remain when the mold is opened.