JP3240379B2 - Disc injection molding apparatus and disc injection molding method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection molding apparatus, and more particularly to a record disk having a central opening, a magnetic disk,
The present invention relates to an injection molding apparatus and a disk injection molding method used for molding a disk substrate (hereinafter, simply referred to as a disk) such as an optical disk or an information recording disk.

[0002]

2. Description of the Related Art Discs having an opening at the center, particularly optical discs, are required to have a low birefringence and a small deformation as a condition for reproducing a clear image or high-quality sound. Generally, in molding a disk having an open central portion by high-pressure injection molding, as shown in FIG. 7, molten resin is injected and filled into a cavity 3 that has been mold-closed through a sprue bush 7, and the center of the disk is opened by punching. are doing. At this time, the mold is slightly opened by overcoming the mold clamping force to inject the molten resin at high pressure, and gas and the like are discharged from the cavity 3 to complete the filling of the molten resin, but the mold clamping force continues. Therefore, pressure is applied to the resin filled in the cavity by closing the mold, and the resin in the cavity flows back to the sprue side because the resin in the cavity is not completely cooled and solidified. The birefringence and deformation of the disc are greatly affected by this backflow, so the male cutter 19 advances the gate seal to close the sprue gate to the tip of the female cutter 8 after the injection filling is completed to stop the backflow. Gate cutting was performed simultaneously with punching to open the openings.

[0003]

However, in the above-mentioned prior art, the setting of the sprue bush 7, the clearance between the male cutter 19 and the female cutter 8, the pressure for performing the gate cut according to the molding conditions, and the like are performed. Therefore, it was necessary to adjust the gate cut timing for each molding machine.

In gate cutting, gate sealing and punching are performed at the same time, but the best timing for performing gate sealing for stopping backflow and the best timing for performing punching without burrs and burrs are different. Therefore, it is impossible to select the best timing together, and there is a problem that molding must be performed at the expense of either timing.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to enable gate sealing and punching to be performed separately at the best timing, thereby enabling easy adjustment for each molding machine. .

[0006]

In order to solve the above-mentioned problems, a disk injection molding apparatus according to the present invention is provided with a fixed die fixed to a fixed platen and a retractable movable die. An injection molding machine comprising a movable mold fixed to a movable platen and forming a cavity by clamping the mold, wherein a male cutter and a seal pin are concentrically arranged at the center of one mold, and the other mold is formed. At the center, a female cutter carrying a sprue bush that opens to the cavity side is attached. At the tip of the male cutter, a head having a diameter smaller than the inner diameter of the female cutter is provided facing the sprue bush, and the head has an annular shape. A groove is formed so that the male cutter and the seal pin can be driven and controlled so that they can move forward and backward respectively.

Further, in order to solve the above problem, a disk injection molding method according to the present invention provides a mold clamping step of closing a fixed die fixed to a fixed platen and a movable die fixed to a movable platen to increase the pressure. And an injection step of injecting the molten resin into the cavity formed by clamping, a cooling step of holding the injection in a completed state and cooling the molten resin in the cavity, and opening the mold and moving the movable platen The molding method of an injection molding apparatus for a disk according to claim 1, wherein the mold opening step and the ejecting step of ejecting the molded disk by ejecting the molded disk from the mold are sequentially performed.
A gate sealing step of advancing the seal pin to close the cavity by contacting the cooling solidified layer on the surface of the opening of the sprue bush on the cavity side is performed, and then performing a punching step of advancing the male cutter to open the center of the disk. Method.

[0008]

When the molten resin is filled into the cavity of the clamped mold, the molten resin filled at a high pressure is radially diffused into the cavity, and the generated gas and air in the cavity dissipate the molten resin during injection filling. Since the injection power is high, the mold is slightly opened by overcoming the mold clamping force and discharged outside the mold. The sprue gate is sealed by advancing the seal pin at the best timing for the gate seal. Therefore, although the mold is closed because the mold clamping force is continued, the molten resin stays in the cavity without flowing backward and is cooled by the sealed sprue gate to form a disk because the sprue gate is sealed. The timing of punching and opening the center of the disk formed by advancing the male cutter to the tip of the female cutter can be set to the best timing for punching, separately from the gate seal.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a disk molding die according to the present invention will be described below with reference to FIGS. FIG. 1 is a cross-sectional view of a disk forming die according to the present invention. A fixed die 1 and a movable die 2 form a disk-shaped cavity 3 in a clamped state.

The fixed mold 1 is mounted on a fixed platen 5 and has a female cutter 8 carrying a sprue bush 7 for injecting a molten resin into a through hole 6 provided at the center. An opening 10 having a tapered portion 9 is formed in the fixed platen 5, and a nozzle 11 is provided so as to contact and retreat with this opening. Between the injection opening 7a of the sprue bush 7 and the cutter portion 8a of the scalpel cutter, a tapered portion 7b that expands temporarily is formed (see FIGS. 3 and 5).

The movable mold 2 is provided so as to be able to advance and retreat with respect to the fixed mold 1, and is attached to the movable platen 15. A through hole 16 is provided in the center of the movable mold 2, and a stamper holder 17 and an ejector pin 18 are provided in the through hole 16.
The male cutter 19 and the seal pin 20 are arranged concentrically.

A stamper 21 is disposed on the mirror surface of the movable mold 2, and the inner peripheral edge thereof is held on the mirror surface by the tip claw portion of the stamper holder 17, and the outer peripheral edge of the stamper is formed along the outer peripheral portion of the movable mold 2. And is held at a small interval 23 by an outer peripheral ring 22 arranged in a vertical direction. A male cutter 19 is fitted and fixed inside the stamper holder 17.

The ejector pin 18 has an ejector plate 25 provided at a rear portion thereof, and is slidably inserted into the inside of the male cutter 19. The ejector plate 25 is disposed in a guide chamber 26 provided in a movable mold component, and a projecting body 27 is interposed between a front wall 26a of the guide chamber and a front face 25a of the ejector plate, and an ejector pin 18 is provided. Is biased in the opposite direction to the fixed mold 1. An ejector pressing rod 28 is located on the rear surface 25b of the ejector plate, and the ejector pressing rod 28 is driven by control means and driving means (not shown) when the mold is opened and the disc is taken out, so that the ejector plate 25 is ejected. Press the ejector pin
Push 18 forward.

The tip of the male cutter 19 is a female cutter.
A head having a diameter smaller than the inner diameter of 8 is provided, and this head has a tapered portion 19a so as to fit into the injection port of the sprue bush 7.
Is formed and the tapered portion 19a and the cutter portion 19 are formed.
An annular groove 30 for undercut is provided between b. Also, a cutter plate is attached to the rear of the male cutter 19.
31 is provided and is slidably inserted through the ejector pin 18. The cutter plate 31 is disposed in a guide chamber 32 provided in a movable mold component, and a front wall 32 of the guide chamber is provided.
A projecting body 33 is interposed between a and the front face 31a of the cutter plate to fix the male cutter 19 and the female cutter 8 of the mold 1
In the opposite direction. A punching and pressing rod 34 is located on the rear surface 31b of the cutter plate, and the punching and pressing rod 34 is driven by control means and driving means (not shown) to press the cutter plate 31,
Push the male cutter 19 forward. The protruding male cutter 19 has its cutter portion 19b inserted into the female cutter 8 and punches out the center of the disk.

The seal pin 20 has a seal plate 40 at the rear.
And is slidably inserted into the center of the male cutter 19. This seal plate 40 is disposed in a guide chamber 41 provided in the movable mold component, and a front wall 41 of the guide chamber is provided.
A spout bush 7 of the mold 1 fixes the seal pin 20 with a spout 42 interposed between the a and the front face 40a of the seal plate.
In the opposite direction. A seal pressing rod 43 is located on the rear surface 40b of the seal plate. The seal pressing rod 43 is driven by control means and driving means (not shown) to press the seal plate 40, and
20 is projected forward to close cavity 3. In addition,
As shown in FIG. 4, the molten resin in the initial stage of injection filling has begun to form the cooling solidified layer C around the sprue gate.
The seal pin 20 abuts and seals the cooled solidified layer C.

Next, an embodiment of a disk injection molding method according to the present invention will be described with reference to FIG. The disk injection molding method includes a mold clamping step, an injection step, a cooling step,
The mold opening step and the ejecting step are sequentially performed, a gate seal is performed during or after the injection of the molten resin, and the punching step is performed at a predetermined best timing.

In the steps from the mold clamping step to the injection step, the movable mold is moved to the fixed mold, the mold is closed, and the molten resin is filled from the nozzle through the sprue bush into the cavity of the pressurized mold. The molten resin is filled at high pressure and diffuses in the cavity radially, and the generated gas and air in the cavity slightly overcome the mold clamping force due to the high injection power of the molten resin during injection filling, causing the mold to slightly move. Opens and is released out of the mold.

At the time of the cooling step after the injection filling is completed, as shown in FIG. 3, the sealing pin 20 is advanced to the injection opening 7a of the sprue bush to perform the gate sealing. Although the mold clamping force continues and pressure is applied to the cavity, the molten resin stays in the cavity and cools down without forming a backflow because the sprue gate is sealed to form a disk. In this embodiment, the gate sealing is performed after the completion of the injection filling. However, the gate sealing may be performed before the completion of the injection filling depending on the condition of the molded product or the like.

As shown in FIG. 5, the disk which is cooled and cooled to a predetermined state after the gate seal and which is in the best condition for punching is used.
The male cutter 19 is advanced to the tip of the female cutter 8.
The center of the disk is punched and opened without burrs or burrs.

At the same time as the seal pin 20 is retracted, the mold clamping pressure is released and the mold is opened. When the disk D is taken out after the mold opening is completed, the resin S solidified in the sprue adheres to the head of the male cutter 19 due to the undercut of the annular groove 30 as shown in FIG. After ejecting the seal pin 20 and the ejector pin 18 in the retracted state, the ejector pin 18 is retracted earlier than the seal pin 20 to take out the molded disk and the resin S solidified in the sprue. The eject pin may be ejected to eject the disc, or ejected by blowing eject air between the mold and the disc.

[0021]

Since the present invention is configured as described above, the following effects can be obtained.

Since the timing of the gate seal and the punching can be set independently, it is possible to form a disk having a good cut of the central opening and a good birefringence.

Since the best timing for punching can be set separately from the timing of the gate seal, a disk free of burrs and burrs can be formed.

When the gate seal is performed, the seal pin abuts on the solidified cooling layer formed around the sprue gate, so that the sprue gate is securely closed and the resin solidified in the sprue after the mold is opened is surely removed. be able to.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of a disk injection molding apparatus according to the present invention.

FIG. 2 is a timing chart showing the operation of one embodiment of the disk injection molding apparatus according to the present invention.

FIG. 3 is a partially enlarged view showing a state where a seal pin is advanced to perform a gate seal.

FIG. 4 is a partially enlarged view showing a state in which the molten resin starts to cool and solidify around the sprue gate and the sealing pin tip and the sprue bush are in close contact with each other.

FIG. 5 is a partially enlarged view showing a state in which a male cutter advances to a female cutter to perform punching.

FIG. 6 is a partially enlarged view showing a state in which a molded disk is taken out by ejecting an eject pin and a seal pin.

FIG. 7 is a sectional view showing a conventional disk injection molding apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fixed die 2 Movable die 3 Cavity 7 Sprue bush 8 Female cutter 11 Nozzle 17 Stamper holder 18 Ejector pin 19 Male cutter 20 Seal pin 21 Stamper 30 Annular groove

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B29C 45/38-45/44

Claims (2)

(57) [Claims] 1. Injection molding comprising a fixed die fixed to a fixed platen and a movable die fixed to a movable plate provided so as to be able to advance and retreat with respect to the fixed die, wherein a mold is clamped to form a cavity. A male cutter and a seal pin are arranged concentrically at the center of one mold, and a female cutter carrying a sprue bush opening toward the cavity is attached to the center of the other mold; A head having a diameter smaller than the inner diameter of the female cutter is provided in the portion, and an annular groove is formed in the head, and the male cutter and the seal pin can be driven and controlled so that they can move forward and backward respectively. An injection molding apparatus for a disk. 2. A mold clamping step of closing a fixed die fixed to a fixed platen and a movable die fixed to a movable platen to increase the pressure, and an injection step of injecting a molten resin into a cavity formed by clamping. And a cooling step of holding the injection completed and cooling the molten resin in the cavity, a mold opening step of opening the mold and moving the movable platen, and an ejecting step of ejecting the molded disc from the mold by ejecting it. 2. The molding method of the disk injection molding apparatus according to claim 1, wherein the sealing pin is advanced during or after the injection to form a cooling solidified layer on the surface of the opening of the sprue bush on the cavity side. A gate sealing step of closing the cavity by abutting, followed by a punching step of opening the center of the disk by advancing the male cutter. Injection molding method of risk.