JP2003103577A - Injection molding tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a molten resin from being excessively supplied in one side direction of a cavity and thereby, inhibit the concentration of a stress or the warpage of a finished product, even when a gate is arranged at a position where it is deviated from the center of the cavity to the one side. SOLUTION: The injection molding tool 1 has a recessed resin reservoir 7 formed in an opposite face to a gate 6 and a molten resin is injected into a cavity 4 from a molten injection hole 5 in the center of the gate 6 to form a resin molded product. The resin reservoir 7 is formed at an offset position to the molten resin injection hole 5. A gap between the tip face of the gate 6 encircling the hole 5 and the inner face 3a of the cavity 4 opposed to the tip face of the gate 6, differs in circumferential size. Besides, the difference in the circumferential size of the gap works to adjust the flow rate and direction of the molten resin.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection mold for resin molding upper and lower shells of a disk cartridge.

[0002]

2. Description of the Related Art FIG.
The one shown in FIG. 14 is known. The disc cartridge 101 includes a disc-shaped recording medium 102, a cartridge case (hereinafter referred to as a shell) 103 that rotatably accommodates the disc-shaped recording medium 102, and a shell 1.
03 includes a shutter 105 that opens and closes an opening 104 provided on the upper and lower surfaces, and a shutter spring 106 that biases the shutter 105 in a direction to close the opening 104.

The shell 103 comprises an upper shell (upper half) 107 and a lower shell (lower half) 108.

The upper and lower shells 107 and 108 are provided with recessed shutter slide portions 109 and label sticking portions 110 on their surfaces.

The upper and lower shells 107 and 108 are provided with a gate mark 111 generated when molding with an injection mold described below, and a gate mark 111 so that the gate mark 111 does not protrude from the shell surface. A gate drop-in recess 112 is provided.

15 and 16 show the upper and lower shells 10 described above.
The injection molding die 201 which injection-molds 7,108 is shown.
The injection mold 201 includes a fixed mold 202 and a movable mold 203. A cavity 204 for molding, for example, the upper shell 107 between the fixed mold 202 and the movable mold 203. Are formed.

The fixed mold 202 is provided with a gate 206 having a molten resin injection hole 205 in the center. Further, the movable mold 203 is provided with a resin reservoir 207 having an arcuate concave surface on the cavity inner surface 203 a facing the molten resin injection hole 205.

The resin reservoir 207 has a molten resin injection hole 20.
The center CL2 of the resin pool 207 with respect to the center CL1 of 5
Are arranged in a matched state. Then, the molten resin is injected from the molten resin injection hole 205 into the cavity 204.

At the tip of the gate 206, a ring-shaped convex portion 208 for forming a gate drop-in concave portion that protrudes into the cavity 204 is provided so as to surround the molten resin injection hole 205 as a center.

A convex portion 208 for forming a gate drop concave portion
The gap δ between the front end surface 209 of the above and the cavity inner surface 203a on the movable mold 203 side facing the front end surface 209 is formed uniformly over the entire circumference of the convex portion 208 for forming the gate drop concave portion. There is. The resin reservoir 207 is directly formed on the cavity inner surface 203a of the movable mold 203 by punching the cavity inner surface 203a of the movable mold 203.
It is formed or is formed by detachably attaching the resin pool forming pin 210 provided with the resin pool 207 to the movable mold 203.

[0011]

In the conventional injection molding die 201, as described above, the tip surface 209 of the convex portion 208 for forming the gate drop concave portion and the movable die 203 side facing the distal end surface 209. The gap δ between the cavity inner surface 203a and the cavity inner surface 203a at the outer peripheral portion of the resin reservoir 207 is uniformly formed over the entire circumference of the ring-shaped convex portion 208 for forming the gate drop concave portion. There was a problem. (1) When the gate 206 is arranged in the center of the cavity 204, the molten resin is uniformly filled in the cavity 204 from all directions of 360 ° centering on the molten resin injection hole 205. Therefore, as shown in FIG. 15, when the gate 205 is arranged in the central portion of the cavity 204, the molten resin is uniformly injected from the gate 206 in the central portion of the fixed mold 202 in all directions of the cavity 204. As it goes, you can do ideal molding. However, as shown in FIG. 13, the upper shell 107 having the gate mark 111 and the gate drop recess 112 in the central portion has the gate mark 111.
Since the gate drop recess 112 is conspicuous, the aesthetic appearance is impaired. (Even if the gate mark 111 and the gate drop recess 112 are covered with a label, the gate mark 111 and the gate drop recess 11 are covered.
2 is often visible on the surface of the label). (2) The gate mark 111 and the gate drop recess 11
In order to make 2 inconspicuous, as shown in FIG. 18, the gate 206 is offset (shifted) from the central portion of the cavity 204 so that it is close to the first side portion 204a side (close to the first side portion 204a side). And is arranged at a position apart from the second side portion 204b), it becomes difficult to fill the molten resin on the side of the second side portion 204b separated from the gate 206.
The filling pressure must be increased in order to completely fill the second side portion 204b with the molten resin. But the second
When the filling pressure is increased to completely fill the side portion 204b of the molten resin, the first side portion 20 of the cavity 204 having a small distance from the gate 206 and a small resin filling capacity
On the side of 4a, the molten resin is in an excessively supplied state, stress concentrates, the product warps, and the corners are curled due to defective release. For example, in FIG.
As shown in FIG. 7, when the gate is arranged on the first side portion 107a of the upper shell 107, the first side portion 107a
The stress concentrates on the side, and the upper shell 107 warps back as shown in FIG.

The present invention solves the above-mentioned conventional problems, and even when the gate 206 is arranged at a position deviated from the central portion of the cavity 204 to one side portion, the molten resin is excessive in the one side portion direction. It is possible to prevent the supply of the power and to suppress the concentration of the stress and the warp of the product.

[0013]

In order to achieve the above object, the present invention provides a concave resin reservoir on the facing surface of the gate, and the molten resin is injected into the cavity from the molten resin injection hole at the center of the gate. And a tip end surface of a gate surrounding the molten resin injection hole by providing the resin pool at an offset position with respect to the molten resin injection hole. , A gap between the inner surface of the cavity facing the front end surface of the gate and a difference in size in the circumferential direction, and adjusting the flow rate of the molten resin and its directionality depending on the size of the gap, The amount of the molten resin flowing through was regulated, and more molten resin was made to flow smoothly in the direction of the larger gap.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Next, an injection molding die of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view of an injection molding die 1 according to the first embodiment. The injection mold 1 is 3.
It is configured as an injection mold for molding the upper shell of a 5-inch optical disk cartridge.

The injection molding die 1 is provided with a fixed die 2 and a movable die 3 which is movable in the contact and separation directions with respect to the fixed die 2, and these fixed die 2 and the movable die are provided. A cavity 4 is formed between the three.

The fixed mold 2 has a molten resin injection hole 5 at the center thereof.
Gate bush (hereinafter simply referred to as a gate) 6 having
Is equipped with.

The movable mold 3 is provided with a resin reservoir 7 on the cavity inner surface 3a facing the molten resin injection hole 5. Then, the molten resin is injected into the cavity 4 from the molten resin injection hole 5 at the center of the gate 6.

The gate 6 is located on the first side 4 of the cavity 4.
a (close to the first side portion 4a and the second side portion 4a)
It is arranged at a position apart from b).

The gate 6 is the center CL of the molten resin injection hole 5.
It is removably attached to the fixed mold 2 so that 1 is perpendicular to the cavity inner surface 2a on the fixed mold 2 side.

As shown in FIG. 2, the gate 6 is formed of a metal such as a nickel alloy into a bottomed cylindrical shape having a diameter φ1 of about 11 mm.

The gate 6 is provided with a projection 8 for forming a drop recess for forming a gate drop recess of a gate mark on the upper shell as a molded product at the center of the bottom 6a.

As shown in FIG. 3, the projection 8 for forming the recessed recess has a truncated cone shape with a root diameter φ2 of approximately 3 mm, a tip diameter φ3 of approximately 2 mm, and a height H1 of approximately 0.6 mm. Is formed in. Further, the mouth portion at the tip of the molten resin injection hole 5 formed in the bottom portion 6a of the gate 6 has a diameter reduction angle θ1.
Has a diameter of about 30 °, and the diameter φ4 of the mouth portion is about 1.
It is formed in a circular shape of 0 mm.

The resin reservoir 7 has a radius R of 3 to 5 mm (5 mm in the case of the embodiment), and a diameter φ5 is a circle having a diameter approximately equal to the diameter φ2 of the root of the projection 8 for forming the recessed recess. It is formed in an arcuate concave surface.

With respect to the center CL1 of the molten resin injection hole 5,
The center CL2 of the resin reservoir 7 is provided at a position eccentric to the right in FIG. 3, that is, at an offset position.

The offset amount between the center CL1 of the molten resin injection hole 5 and the center CL2 of the resin pool 7 is determined by the molten resin injection hole 5
The outer peripheral edge 5a of the resin reservoir 7 is set inside the outer peripheral edge 7a, that is, the distance S between the outer peripheral edge 5a of the molten resin injection hole 5 and the outer peripheral edge 7a of the resin reservoir 7 is set to 0 or more. Has been done.

The portion 4c having the smallest distance S and the narrowest gap between the convex portion 8 for forming the depression concave portion and the cavity inner surface 3a is arranged toward the first side portion 4a of the cavity 4. In addition, the portion 4d in which the gap between the projection 8 for forming the recessed recess and the cavity inner surface 3a is the widest is the second side portion 4 of the cavity 4.
It is arranged toward b.

As shown in FIG. 4, in the resin reservoir 7, the center CL2 is the center (axial center) CL of the resin reservoir forming pin 11.
It is provided on the tip end surface of the resin puddle forming pin 11 in a state of being aligned with each other. The resin pool forming pin 11 is used for the movable mold 3
It is detachably attached to the pin attachment hole 12 provided in the.

As shown in FIG. 1, the fixed mold 2
Is provided with a spool bush 21 for resin supply, and the molten resin supplied from the spool bush 21 enters the cavity 4 from the resin injection hole 5 of the gate 6 via the runner 22 and the second spool 23. Supplied.
Further, the movable mold 3 is provided with an eject pin 24 for ejecting the molded upper shell.

Injection molding using the injection molding die 1 is performed in the following order. First, the movable mold 3 is moved toward the fixed mold 2 to close the mold. When the mold closing is completed, the molten resin is injected into the cavity 4 with a predetermined pressure. After injecting the molten resin, the inside of the cavity 4 is kept at a predetermined pressure for a certain time. Next, the mold and the upper shell as a resin molded product are cooled. Next, the movable mold 3 is separated from the fixed mold 2 to open the mold. Then, the upper shell as a resin molded product is taken out from the mold by the eject pin 24. FIG. 5 is a flow chart showing the injection molding process.

The injection-molding die of the first embodiment has the above-mentioned structure, and the projection 8 for forming the drop recess is formed.
And a portion 4c where the gap between the cavity inner surface 3a and
Is arranged toward the first side portion 4a of the cavity 4, and a portion 4d having the widest gap between the projection 8 for forming the recessed recess and the cavity inner surface 3a is formed on the second side portion 4b of the cavity 4. The molten resin flows smoothly toward the second side portion 4b side rather than the first side portion 4a side, as shown in the schematic view of FIG.

Therefore, it becomes possible to reduce the filling time (injection time), the filling pressure (injection pressure), the pressure holding time and the pressure holding of the molten resin into the entire cavity 4. Incidentally, as shown in FIG. 17, the center CL of the conventional resin reservoir 207 is
2 and the center CL1 of the molten resin injection hole 205 are aligned,
As a comparative example, the conventional example using a gate in which the gap between the tip end of the protrusion 208 for forming the recessed recess and the cavity inner surface 203a of the movable mold 203 is uniform over the entire circumferential direction is used as a comparative example. As a result, the results shown in FIG. 7 were obtained, and the filling time, the filling pressure, the holding time and the holding pressure were significantly reduced, and the molding cycle was significantly reduced (from the conventional 5 to 5).
10%) can be shortened.

Further, according to the injection molding die of the first embodiment, the excessive supply of the molten resin to the first side portion 4a side of the cavity 4 is suppressed and the stress is prevented from concentrating on the portion. can do. Therefore, it is possible to prevent the upper shell from warping or the like caused by stress concentration due to excessive supply of the molten resin. By the way, the warp (flatness) of the upper shell of the comparative example and the vicinity of the first side of the upper shell manufactured by the injection mold of the present invention (measurement length L≈40 mm at the position C in FIG. 18) ) Was obtained, the results shown in FIG. 8 were obtained, and it was proved that the warpage was reduced and the flatness was improved.

FIG. 9 shows an injection molding die according to the second embodiment. In this embodiment, the resin puddle forming pin 11 is rotatable in the pin mounting hole 12, and the axial center of the resin puddle forming pin 11, that is, the rotation center CL3 is aligned with the center CL1 of the molten resin injection hole 5. Is attached to. In addition, as shown in FIG.
The center CL2 of 07 is provided at an offset position with respect to the rotation center CL3 of the resin pool forming pin 11.

Then, as shown in FIGS. 11A, 11B, and 11C, the resin pool forming pin 11 is rotated to offset the resin pool 7 from the molten resin injection hole 5 and the gate 6. It is possible to change the direction by 360 °. Other configurations, operations, and effects are the same as those in the first embodiment, and thus redundant description will be omitted. In addition, in the first and second embodiments, the case where the gate 6 is arranged in the vicinity of the first side portion 4a of the cavity 4 is shown. However, the position of the gate 6 is located on the first side of the cavity 4. It is not limited to the vicinity of the portion 4a, but may be in the vicinity of the second side portion 4b of the cavity 4 or a corner portion of the cavity 4. Further, although the case of molding the upper shell of the 3.5-inch optical disk cartridge has been described, the present invention can be applied to molding of the lower shell. Further, not only the 3.5-inch optical disc cartridge, but also various types of optical discs such as mini discs and shells such as 3.5-inch MFD can be widely applied to resin products other than the shell. In addition, even if the injection mold is a cold runner type,
It may be of a hot runner type, and can be applied to a so-called pinpoint gate type injection molding die.

[0035]

The injection molding die of the present invention has the following effects. (1) A ring-shaped gap between the tip surface of the gate surrounding the molten resin injection hole and the cavity inner surface facing the tip surface of the gate, and a large gap portion in the circumferential direction,
Since a small gap is formed and the flow rate and the directionality of the molten resin are controlled by the size of the gap, stress concentration is prevented and warpage or curling of the resin molded product is prevented. (2) By shortening the pressure holding time and the like, it is possible to shorten the molding cycle and improve the production efficiency. (3) Since the resin reservoir is provided on the tip surface of the resin reservoir forming pin and the resin reservoir forming pin is detachably attached to the pin mounting hole provided in the mold, the resin reservoir can be used for a long period of time. If it has expanded, replace it with a resin puddle formation pin,
The resin pool can be easily made new. (4) By rotating the resin pool forming pin, the direction of the large gap portion and the small gap portion between the tip end surface of the gate and the inner surface of the cavity facing the tip end surface of the gate can be set in any direction. Can be set to.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an injection molding die according to a first embodiment.

FIG. 2 is a cross-sectional view of a gate.

FIG. 3 is an enlarged view of a main part.

FIG. 4A is a perspective view of a resin pool forming pin, and FIG.
[FIG. 3] is a vertical cross-sectional view of a resin pool forming pin.

FIG. 5 is a flowchart showing an injection molding process.

FIG. 6 is a schematic diagram showing the flow of molten resin.

FIG. 7 is a graph showing a molding cycle.

FIG. 8 is a table showing the flatness measurement results.

FIG. 9 is a cross-sectional view of an injection molding die according to the second embodiment.

FIG. 10A is a perspective view of a resin pool forming pin,
FIG. 3B is a vertical cross-sectional view of the resin pool forming pin.

11 (A), (B), and (C) are plan views showing a state in which a resin pool forming pin is rotated.

FIG. 12 is a perspective view of a disc cartridge.

FIG. 13 is a perspective view of an upper shell.

14 is a cross-sectional view taken along the line AA of FIG.

FIG. 15 is a cross-sectional view of an injection molding die.

FIG. 16 is a cross-sectional view of an injection molding die.

FIG. 17 is an enlarged view of a main part.

FIG. 18 is a plan view of a disc cartridge.

19 is a cross-sectional view taken along the line BB of FIG.

[Explanation of symbols]

1 ... Injection mold, 2 ... Fixed mold, 3 ... Movable mold, 4 ...
Gate, 5 ... Resin injection hole, 6 ... Cavity, 7 ... Resin reservoir, 8 ... Convex portion for forming gate drop concave portion, 11 ...
Resin pool forming pin, 12 ... Pin mounting hole, 101 ... Cartridge holder, 107 ... Upper shell, 111 ... Gate mark, 112 ... Gate drop recess.

Claims (4)

[Claims] 1. An injection molding die for forming a resin molding by providing a concave resin reservoir on the facing surface of a gate and injecting the molten resin into a cavity from a molten resin injection hole at the center of the gate. An injection molding die, wherein the resin reservoir is provided at an offset position with respect to the molten resin injection hole. 2. The molten resin injection hole is formed in a circular shape, the resin pool is formed in an arcuate concave surface, and the resin pool is formed with respect to the center of the circular molten resin injection hole. The injection molding die according to claim 1, wherein the center is provided at an offset position. 3. The resin reservoir is provided on a tip end surface of a resin reservoir forming pin, and the resin reservoir forming pin is detachably attached to a pin attaching hole provided in a mold. The injection molding die according to claim 1. 4. The resin pool forming pin is rotatably mounted in the pin mounting hole with a center of rotation being aligned with a center of the pin mounting hole, and the resin pool is the resin pool. The injection mold according to claim 3, wherein the injection mold is provided at an offset position with respect to the center of rotation of the forming pin.