JPH05285995A - Gate cut structure of disk molding machine - Google Patents

Abstract

PURPOSE:To improve precision in a molded piece with improvement of cleanness of molding environment and prolong lifetime of a cut pin by preventing generation of metal powders due to sliding friction of the cut pin. CONSTITUTION:In a cylinder member 30 embedded in a moving side mold 6, a cut pin 34 having a sprue ejector pin 32 is provided movably back and forth. The cut pin 34 is locked at its back end side by a ball bearing 33 and centered. With a clearance provided between the tip side and the inner face of the cylinder member 30, to which melted resin does not flow, a non-contact state is kept.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the molding of disks as disk-shaped recording media such as video disks and audio disks, and more particularly to a gate cut structure for forming a central hole of the disk.

[0002]

2. Description of the Related Art Conventionally, in this type of gate cut, for example, a cylinder member is embedded in one of a movable mold plate and a fixed mold plate of a mold, and a cut pin can be slid in the cylinder member. It has a structure to move it back and forth. By advancing the cut pin, the gate portion arranged at the center of the disk-shaped cavity is sheared to form the center hole. Further, the cut pin is retracted after the solidification process, and the disc is taken out.

[0003]

By the way, this type of disk molding is carried out in a clean room in order to avoid contamination due to dust adhesion to the information track surface, and the molding environment is strictly regulated. In the prior art, the structure itself is a source of dust generation, and there is a limit to improving the cleanliness of the molding environment and eventually improving the quality of the molded product (disk).

That is, as shown in FIG.
A large diameter rear end 102a and a small diameter tip 102b
A cut pin 102 having a groove is provided so as to be able to move forward and backward, and the front end portion 102b is centered by holding the rear end portion 102a. However, since this is merely a sliding structure, the center position of the front end portion 102b is maintained. Is unstable, which causes misalignment of the center hole of the disk. Therefore, the result of providing the large-diameter rear end portion 102a has not been achieved.

Even if the surface of the cut pin and the inner surface of the template 100 are surface-finished with high precision, as shown in FIG. Mutual polishing is repeated by sliding,
Metal powder is generated. Although the effect of polishing scratches on the cut pin can be avoided by adopting a shearing method in the semi-solidified or molten state of the resin during gate cutting, the inner circumferential surface of the disc is scraped by scratches when it is pulled back after the solidification process. And resin powder is generated.

[0006] Such metal powder or resin powder easily adheres to a disk having static electricity to cause an erroneous signal, and also mixes with the information track surface in the next cycle to deteriorate the quality of the molded product. .. On the other hand, it is also a cause of increasing the polishing scratches on the cut pin.

Further, in the conventional one, since the molding accuracy is deteriorated due to the mutual wear between the cut pin and the mold plate side, it is unavoidable to replace the parts with a certain number of molding times.

Therefore, according to the present invention, it is possible to avoid the generation of metal powder and resin powder due to the sliding of the cut pin, and it is possible to form the disc center hole with high precision, so that the quality of the molded product can be improved and the service life thereof can be increased. Its purpose is to provide a gate cut structure that can be realized.

[0009]

The present invention was devised in order to achieve the above-mentioned object, and its feature is that the cut pin is centered with the rear end side being restrained by the bearing member and the front end side being The configuration is such that the molten resin is held in a non-contact state with a clearance that prevents the molten resin from entering the template side.

[0010]

According to the present invention, since the tip end of the cut pin moves in a non-contact state, polishing is not performed between the cut pin and the template side.
Generation of metal powder is also avoided. Further, since the gate portion is sheared without any polishing scratches, the generation of resin powder at the time of pulling back is avoided.

Further, the centering of the cut pin is prevented by the restraint of the rear end side in the centered state, and the center hole is formed with high accuracy.

[0012]

1 to 4 show an embodiment of the present invention.
The mold 2 is provided with a fixed-side mold plate 4 and a movable-side mold plate 6 so that the mold 2 can be directly supported and opened / closed by two guide rods 8 also having a tie bar function without using a die plate. It has become. The guide rod 8 can directly use, for example, a rod of a mold clamping cylinder (not shown), and can be held by the bearing member 10 on the fixed-side mold plate 4 so as to be slidable smoothly. The nozzle 12 is inserted into the nozzle guide hole 4a formed in the fixed-side mold plate 4 for injection.

The sprue bushing 1 is provided at the center of the stationary mold plate 4.
4 is attached, and a cavity 15 is provided on the mold facing surface.
The fixed-side mirror surface portion 16 forming one of the components of (1) is fitted into the sprue bushing 14 and the outer peripheral portion is fixed by a bolt 17 and attached. Although not explicitly shown in the drawing, a stamper as a transfer base material is attached to the fixed-side mirror surface portion 16, and the stamper is held by an inner peripheral pressing member (not shown) and an outer peripheral pressing member 18. It is like this.

The outer peripheral pressing member 18 is composed of a ring member 20 which also serves as a spacer between the molds and seals the outer peripheral region of the cavity 15, and a stamper holding portion 22 which is integrally formed on the inner periphery of the ring member 20. ing. Also,
Threaded holes 20a are formed on both sides of the ring member 20, and the fixed-side mold plate 4 and the movable-side mold plate 4 and the movable-side mold plate 4 do not need to be held manually by a through bolt 24 penetrating the fixed-side mold plate 4 or the movable-side mold plate 6. Any of the template 6 can be attached and converted.

As a result, the labor required for replacing the stamper can be reduced and the replacement work can be performed easily and smoothly. That is, in the conventional structure, since it is configured to be attached to and detached from only one of the template plates, it is necessary to hold the outer peripheral pressing member 18, which is a heavy object, during replacement of the stamper, but it is possible to move by replacing the through bolt 24. It can be temporarily temporarily fixed to the side mold plate 6 side, and can be reattached to the fixed side mold plate 4 side without a holding operation by replacing the through bolt 24 again and tightening it in the mold closed state. .. Reference numerals 4b and 6a denote through bolts 2.
4 shows the insertion hole.

On the other hand, a gate cut member 26 is attached to the central portion of the movable side mold plate 6, and a movable side mirror surface portion 28 which is the other component of the cavity 15 is attached to the mold facing surface.

The gate cut member 26 has a sprue ejector pin 32 and a cut pin 34 provided in the cylinder member 30 so as to be movable back and forth. The movable side mirror surface portion 28 is fitted in the cylinder member 30, and the outer peripheral portion is fixed by bolts 29.

The cut pin 34 is centered by being restrained by the ball bearing 33 on the rear end side, and is in a non-contact state with a clearance C (for example, 10 μm) at which the front end side does not enter the molten resin with the inner surface of the cylinder member 30. It has a mirror-finished tip.

A housing hole 14c into which the tip of the cut pin 34 is inserted is formed in the fixed side mirror surface portion 16, and the housing hole 1 is formed.
A so-called cup-shaped gate portion 35 including 4c is configured.

At the tip of the cut pin 34, there is formed a small-diameter gate entry portion 34b having a slack well portion 34a in the center and a chamfered outer peripheral edge corner portion, and the cut pin 34 is advanced. Before
The gate entrance portion 34b is set in a state in which the gate entrance portion 34b enters the accommodation hole 14c with a movement gap t left.

When the cavity 15 is filled with the molten resin P, the molten resin P is filled in the cavity 15 under the condition that the pressure is uniformly applied in the thickness direction of the disk by being guided by the gate entrance portion 34b. As a result, the defective molding due to the dripping of the radial pressure, which has been conventionally caused, can be avoided.

After the filling, the cut pin 34 is advanced while the molten resin P is in a molten state, and the tip end of the cut pin 34 further enters the accommodation hole 14c to shear the gate portion 35. Since it is in a molten state, the shearing is performed smoothly and the compressive force generated in the gate portion 35 is applied to the cavity 15
Also, the stress gradient does not occur by uniformly propagating to the sprue bushing 14 side. Further, the resin volume corresponding to the movement of the cut pin 34 moves to the cavity 15 and the sprue bush 14 side, whereby the cavity 15 is uniformly compressed.

When the gate is cut, the mold is opened after the solidification process, the sprue 36 is projected by the movement of the sprue ejector pin 32, and the cut pin 3 is formed.
4 is retracted. After that, the disk 38 having the pits transferred by the stamper is peeled off from the movable mirror surface portion 28. Reference numeral 38a indicates a central hole of the disk 38.

The clearance C between the tip end side of the cut pin 34 and the inner peripheral surface of the cylinder member 30 as the template side is kept in a non-contact state, so that polishing scratches due to the forward and backward movement of the cut pin 34 occur. Therefore, no metal powder is generated. Further, since the tip end of the cut pin 34 is kept in a mirror state, no resin powder is generated due to the backward movement, and the surface property of the center hole 38a becomes smooth.

Further, since the centering of the cut pin 34 is maintained by the bearing restraint on the rear end side, the center hole 38a is formed.
There is no misalignment, and the product accuracy is improved. Since the molten resin P is prevented from entering the gate cut member 26, non-contact movement of the cut pin 34 is always ensured, and there is no need to replace parts due to sliding wear. Further, in this example, the inner peripheral surface 30a of the cylinder member 30 is also mirror-finished, which further improves the accuracy.

Further, an air supply passage 40 is formed in the cylinder member 30, and an annular air discharge port 42 communicating with the air supply passage 40 is formed between the cylinder member 30 and the movable side mirror surface portion 28. Has been done. When the mold is opened, the air discharge port 42 is used as an air suction port to ensure close contact with the movable side mirror surface portion 28 of the disc, and when the disc 38 is taken out, air is blown from the air discharge port 42 to move the side. Mirror part 28
The disc 38 that is in close contact with is easily peeled off.

[0027]

According to the present invention, since the generation of metal powder and resin powder due to the forward and backward movement of the cut pin can be avoided and the centering accuracy of the cut pin can be maintained, the cleanness of the molding environment, which has a limit in the past, can be maintained. It is possible to significantly improve the molding accuracy and the quality of the product.

Further, since the sliding wear of the cut pin can be avoided, it is not necessary to replace the parts due to consumption, so that the working cost can be reduced.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an embodiment of a gate cut structure in a disk molding machine according to the present invention.

FIG. 2 is an enlarged sectional view of a main part.

FIG. 3 is an enlarged cross-sectional view of a main part showing a filled state of resin.

FIG. 4 is an enlarged sectional view of an essential part showing a gate cut state.

FIG. 5 is a schematic sectional view of a conventional gate cut member.

FIG. 6 is a cross-sectional view of a main portion showing a conventional misalignment of a cut pin.

[Explanation of symbols]

 2 Mold 4 Fixed-side mold plate 6 Movable-side mold plate 15 Cavity 35 Gate part 33 Ball bearing (bearing member) 34 Cut pin 38a Center hole C Clearance P Molten resin

Claims (1)

[Claims] 1. A gate, wherein a cut pin is provided to be movable back and forth on one of a movable side mold plate and a fixed side mold plate of a mold, and the cut pin is moved forward to be arranged at the center of a disk-shaped cavity. In a gate cut structure in a disk molding machine in which a part is sheared to form a central hole, the cut pin has a rear end side constrained by a bearing member and centered, and a front end side between the mold plate side. A gate cut structure in a disk molding machine, which is held in a non-contact state with a clearance that prevents molten resin from entering.