JP4516208B2 - Injection device and injection molding method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an injection device and an injection molding method, and more particularly to an inline screw type injection device and an injection molding method.
[0002]
[Background Art and Problems to be Solved by the Invention]
An in-line screw type is known as an injection device, and an injection molding process in such an injection device is performed by repeating a charging step, an injection step, and a pressure holding step.
[0003]
In order to complete the injection process and the pressure holding process and enter the injection process of the next cycle, the charging process must be completed within the time of the cooling process of the molded product, the mold opening process, the removing process and the mold clamping process. .
[0004]
If the cooling time in the cooling process of the molded product is shortened in order to shorten the molding cycle, the time required for the charging process for the next cycle is insufficient, and the charge may not be in time.
[0005]
Therefore, there is a screw pre-pull type injection device that charges in advance, but the device is large and expensive.
[0006]
In addition, the number of screw rotations during charging may be increased to shorten the molding cycle, but the generation of acetaldehyde may be a problem particularly when molding a preform for molding a PET bottle. there were.
[0007]
An object of the present invention is to provide an injection apparatus and an injection molding method that do not require a large apparatus, are inexpensive, and can shorten a molding cycle.
[0008]
Another object of the present invention is to provide an injection apparatus and an injection molding method capable of reducing the generation of acetaldehyde by lowering the screw rotation speed.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, an injection apparatus of the present invention is attached to the tip of an injection cylinder, and an injection nozzle for injecting a resin charged by an injection screw in the injection cylinder;
A shut-off device attached to the injection nozzle,
The injection nozzle includes a main resin passage for injecting resin from a tip of the injection nozzle, and a pressure-maintaining bypass resin passage communicating between the main resin passage and the shut-off position and between the shut-off position and the tip of the injection nozzle. And
The shut-off device includes a shut-off plunger capable of traveling from the shut-off position of the main resin path and the bypass resin path for holding pressure from the shut-off position.
[0010]
The injection molding method of the present invention is an injection molding method for performing injection molding using the injection device,
After injecting the resin from the main resin path of the injection nozzle, the shut-off plunger is advanced to close the main resin path at the shut-off position;
A step of applying pressure to the main resin path by pressing the resin in the bypass resin path by causing the shut-off plunger to advance to the pressure-holding bypass resin path in the shut-off state;
Charging the resin of the next cycle with the injection screw after closing the main resin path with the shut-off plunger;
And after the pressure holding time by the shut-off plunger ends, the step of moving the shut-off plunger to the open position of the main resin path and injecting the next cycle is included.
[0011]
According to the present invention, in addition to the main resin path, a pressure holding bypass resin path is formed in the injection nozzle, and the main resin path is closed by the shutoff plunger of the shutoff device and the pressure holding by the progress to the bypass resin path is performed. Since the configuration is such that the device does not become large like a screw prep plastic type injection device, it can have a small and simple configuration and can be inexpensive.
[0012]
In addition, since the main resin path is closed by the shut-off plunger and the pressure holding is performed by proceeding to the bypass resin path, the pressure holding time can be used for the charge time even when the cooling time of the molded product is shortened. Therefore, a sufficient charge time can be secured and the next cycle can be charged, which contributes to shortening of the molding cycle.
[0013]
Furthermore, since the pressure holding time can be taken sufficiently by the shut-off plunger, a good molded product without sink can be obtained, and a sufficient charging time can be taken, so that the screw rotation speed can be lowered. In addition, with a resin such as polyester, acetaldehyde in the molded product can be reduced.
[0014]
In the present invention, in the step of closing the main resin path, after injecting resin from the main resin path of the injection nozzle, while applying pressure to the main resin path by an injection screw, the shut-off plunger is advanced, After the main resin path is closed by the shut-off plunger, the pressure holding by the injection screw may be released.
[0015]
By adopting such a configuration, it is possible to maintain a pressure-holding state at all times after the injection of the resin, and it is possible to further prevent occurrence of sink marks in the molded product and obtain a good molded product.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described in detail with reference to the drawings.
[0017]
FIG. 1 is a cross-sectional view showing an injection apparatus according to an embodiment of the present invention.
[0018]
In FIG. 1, only the tip portion of the injection device is shown, and a molding material supply hopper, an injection hydraulic cylinder, screw rotation driving means, and the like on the rear are omitted.
[0019]
The injection device 10 incorporates an injection screw 14 in an injection cylinder 12, and an injection nozzle 18 having a shut-off device 16 is attached to the tip of the injection cylinder 12.
[0020]
A molding material supply hopper (not shown) is connected to the injection cylinder 12, and a resin as a molding material is supplied from the molding material supply hopper into the injection cylinder 12.
[0021]
A heater (not shown) is attached around the injection cylinder 12 and the injection nozzle 18 to heat and melt the resin supplied from the molding material supply hopper.
[0022]
A known drive mechanism can be arbitrarily used for the screw rotation driving means and the injection hydraulic cylinder.
[0023]
The injection screw 14 has a screw head 20 at the tip, and can be rotated by a screw rotation driving means (not shown). By the rotation of the injection screw 14, the resin heated and melted in the injection cylinder 12 is depopulated, and the screw The head 20 moves backward while charging the resin for one injection, and after the charging is completed, the injection screw 14 is advanced by an injection hydraulic cylinder (not shown) to perform injection.
[0024]
The injection nozzle 18 communicates with the inside of the injection cylinder 12 and reaches the nozzle bush 22 provided at the tip of the injection nozzle 18, and the shutoff position A and the shutoff by the shutoff device 16 of the main resin path 24. Between the position A and the nozzle bush 22 at the tip of the injection nozzle 18, there is a pressure holding bypass resin passage 26 communicating with the main resin passage 24.
[0025]
The nozzle bush 22 is connected to the injection cavity mold via, for example, a hot runner mold (not shown).
[0026]
The shut-off device 16 performs shut-off of the main resin passage 24 and holding pressure after the shut-off, and a hydraulic cylinder 32 attached to the injection nozzle 18 via an attachment member 28 and an attachment rod 30, and the hydraulic cylinder The piston rod 34 is made to be able to advance and retreat from 32, and the shut-off plunger 36 attached to the tip of the piston rod 34.
[0027]
A heater (not shown) is attached around the attachment member 28.
[0028]
The shut-off plunger 36 is inserted into the inlet of the injection nozzle 18 that passes through the mounting member 28 and guides the shut-off plunger 36 to the shut-off position A of the main resin passage 24.
[0029]
Then, the shut-off plunger 36 advances to the shut-off position A of the main resin path 24 via the hydraulic cylinder 32 and the piston rod 34, thereby closing the main resin path 24 and further from the shut-off position A. By proceeding into the pressure-holding bypass resin path 26, pressure can be applied to the resin on the front end side from the shut-off position in the main resin path 24.
[0030]
Next, an injection molding method using such an injection apparatus 10 will be described.
[0031]
First, in a state where the injection screw 14 moves backward by a predetermined stroke in the injection cylinder 12 and the resin for one injection is charged in front of the screw head 20, the injection screw 14 is advanced by an injection hydraulic cylinder (not shown) for one time. Inject.
[0032]
At this time, the tip of the shut-off plunger 36 is in a state of being retracted from the shut-off position A adjacent to the main resin path 24 at the introduction port, and the charged resin is in the main resin path 24 and the bypass resin path. 26 and filled into the mold (not shown) from the nozzle bush 22 through the main resin passage 24.
[0033]
Subsequently, after the resin is injected from the main resin path 24 of the injection nozzle 18 (injection process end), the hydraulic cylinder 32 is operated simultaneously with switching to the pressure holding process, and the shut-off plunger 36 is moved to the shut-off position of the main resin path 24. Proceed to A to close the main resin path 24.
[0034]
In order to close the main resin passage 24 quickly, it is preferable that the tip of the shut-off plunger 36 is disposed at a position adjacent to the main resin passage 24 at the inlet.
[0035]
At this time, the tip of the shut-off plunger 36 closes the main resin passage 24 and the communication portion with the shut-off position A of the bypass resin passage 26.
[0036]
Further, the pressure holding process by the injection screw 14 is continued until at least the shut-off plunger 36 closes the main resin passage 24.
[0037]
When the shut-off plunger 36 is further advanced into the pressure-holding bypass resin path 26 from this state, the resin in the bypass resin path 26 is pressed by the shut-off plunger 36, and the pressure is passed from the bypass resin path 26 to the main resin path. The pressure is applied to the main resin path 24.
[0038]
Therefore, the straight portion of the bypass resin passage 26 for the shut-off plunger 36 to advance may be more than the amount necessary for holding pressure, and is about several percent of the injection capacity.
[0039]
In this state, the pressure-holding state is maintained for a predetermined time, and the injection molded product is waited until it is sufficiently cooled until the gate is sealed.
[0040]
In this way, maintaining the holding pressure with the shut-off plunger 36 prevents the occurrence of sink marks when the injection molded product is cooled, thereby maintaining the quality of the molded product and shortening the molding cycle. It becomes.
[0041]
Further, after the main resin passage 24 is closed by the shut-off plunger 36, the pressure holding of the injection screw 14 is terminated, and charging of the resin in the next cycle is started.
[0042]
In this case, since the main resin path 24 is closed by the shut-off plunger 36, the resin pressure in the main resin path 24 does not decrease even when the injection screw 14 is retracted, and the time of the conventional pressure holding process is reduced. Since it can be used for charging, a sufficient charging time can be ensured, the cooling time of the injection molded product can be shortened, and even when an attempt is made to shorten the molding cycle, it is possible to sufficiently cope.
[0043]
That is, it is possible to enter the charging process of the next cycle immediately after injecting the charged resin without waiting for the completion of the pressure holding process by the injection screw as in the prior art, and to perform the charging process with sufficient time margin. Therefore, it is possible to reliably complete the charging process within the time of the cooling process, the mold opening process, the removing process, and the mold clamping process.
[0044]
Further, if the cycle time is the same, the charging time can be made relatively long, so that the number of acetaldehyde generation can be kept low by lowering the screw rotation speed.
[0045]
Next, after completion of the pressure holding time by the shut-off plunger 36, the shut-off plunger 36 is moved to the open position of the main resin passage 24 to be in a retracted state, and injection of the next cycle is performed.
[0046]
The present invention is not limited to the above-described embodiment, and can be modified into various forms within the scope of the gist of the present invention.
[0047]
For example, a pressure sensor is provided between the shut-off position A of the main resin passage 24 and the mold so that the pressure-holding process of the injection screw is not completed before the shut-off plunger 36 closes the main resin passage 24. You may control, monitoring the resin pressure of a resin path.
[0048]
Moreover, in the said embodiment, although the state which attached the shut-off plunger to the piston rod was shown, it is also possible to extend a piston rod and to form a shut-off plunger integrally.
[Brief description of the drawings]
FIG. 1 is a partially enlarged sectional view showing an injection apparatus according to an embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Injection apparatus 12 Injection cylinder 14 Injection screw 16 Shut-off apparatus 18 Injection nozzle 20 Screw head 24 Main resin path 26 Bypass resin path 36 Shut-off plunger

Claims (3)

An injection nozzle that is attached to the tip of the injection cylinder and injects resin charged by an injection screw in the injection cylinder;
A shut-off device attached to the injection nozzle,
The injection nozzle includes a main resin passage for injecting resin from a tip of the injection nozzle, and a pressure-maintaining bypass resin passage communicating between the main resin passage and the shut-off position and between the shut-off position and the tip of the injection nozzle. And
The shut-off device has a shut-off plunger that can travel from the shut-off position of the main resin passage and the bypass resin passage for holding pressure from the shut-off position. An injection molding method for performing injection molding using the injection apparatus according to claim 1,
After injecting the resin from the main resin path of the injection nozzle, the shut-off plunger is advanced to close the main resin path at the shut-off position;
A step of applying pressure to the main resin path by pressing the resin in the bypass resin path by causing the shut-off plunger to advance to the pressure-holding bypass resin path in the shut-off state;
Charging the resin of the next cycle with the injection screw after closing the main resin path with the shut-off plunger;
After completion of the pressure holding time by the shut-off plunger, moving the shut-off plunger to the open position of the main resin path and injecting the next cycle;
An injection molding method comprising: In claim 2,
In the step of closing the main resin path, after injecting the resin from the main resin path of the injection nozzle, the main resin path is pressurized with an injection screw, the shut-off plunger is advanced, and the shut-off plunger An injection molding method, wherein after the main resin passage is closed, the holding pressure by the injection screw is released.

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