JP2003112337A - Method for injection-molding axially opened synthetic resin molded article and apparatus therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for injection-molding an axially opened synthetic resin molded article of high accuracy having no weld line and not requiring the post-processing of a gate mark after molding by a hot runner system, and an apparatus therefor. SOLUTION: When the molten resin ejected from the annular gate 12a of an upper mold 8 is injected in the cavity 16 formed between the upper mold 8 and a lower mold 15, the molten resin is allowed to flow in the cavity along the outside of the leading end 17a of a core pin 17 engaged with and disengaged from the center of the annular gate 12a of the upper mold 8 to be coold and solidified. Thereafter, the upper and lower molds 8 and 15 are separated to obtain the axially opened synthetic resin molded article A or B or C having an axial hole based on the core pin 17 bored therein.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection molding method and apparatus for a shaft-shaped open synthetic resin molded product which enables a shaft-shaped open molded product to be molded easily and efficiently by using a hot runner system. Regarding

[0002]

2. Description of the Related Art As a molding method and apparatus for this type of axially open synthetic resin molding (hereinafter referred to as "opening molding"),
For example, Japanese Patent Laid-Open No. 2000-326365 or Japanese Patent Laid-Open No.
-38096 and JP-A-3-31328 are known.

[0003]

Among the above known examples,
The technique disclosed in Japanese Patent Laid-Open No. 2000-326365 is
Since the mold life is short because the small core pin is moved, and the cold runner method is used, a large amount of sprue runners can be obtained as wasteful molded products, resulting in the disadvantages of resin loss and molding cost, and the latter 2 In the related art, since the valve gate is used, there is a problem that the moldability of the open-hole molded product is poor and the accuracy cannot be kept high.

The present invention was made by paying attention to the above points. In a hot runner system for injection molding, a tip heater is incorporated in the tip of the probe facing the gate, and injection molding is performed each time. The tip of the core pin, which is capable of being intermittently heated and capable of forming a shaft hole of a molded product or a shaft-shaped molded product having a cap shape, is stored in an annular gate in contact with and separated from the distal end of the probe. When the gate is opened and closed by melting or solidifying the resin to open and close the gate, the heat of the resin near the gate escapes to the core pin during the gate closing operation to stop the heating to the gate part. The cooling and solidification of the resin of the part is promoted, and conversely,
When the gate heater is energized to heat the tip of the probe to open the gate, the resin stored in the gate that maintains a low temperature can be rapidly melted, and the gate opening / closing operation can be performed with good responsiveness. , The molten resin injected into the cavity flows along the core pin, there is no weld line, and there is no need for post-processing such as correcting the misalignment of the gate traces of the open-hole molding. An object of the present invention is to provide an injection method of a synthetic resin article having an open hole and an apparatus therefor.

[0005]

The present invention can solve the above-mentioned problems by providing the following constitutions.

(1) Molten resin is melted or solidified by an intermittent heating operation to inject the molten resin from an upper-shaped annular gate that opens or closes the gate, and the molten resin is formed between the lower mold. When injecting into the cavity, it flows along the outside of the tip of the core pin provided in the lower mold that engages and disengages with the center of the annular gate of the upper mold, and after the molten resin has cooled and solidified, the upper mold and the lower mold are released. An injection molding method of a synthetic resin molded product having a shaft-shaped opening, wherein a molded product having an axial hole based on the core pin is obtained.

(2) The annular gate is formed by exposing the tip of the probe, which contains the chip heater, to the central position of the upper mold gate, and heating the chip heater by energizing it during the injection operation of injection molding. Then, melt the solidified resin facing the annular gate and open the gate.After injection molding is complete, stop energizing the chip heater to solidify the molten resin facing the annular gate and close the gate. The method of injection molding a synthetic resin molded article having an axial opening according to (1) above.

(3) The core pin is movable in the axial direction so as to absorb a difference in expansion between the core pin and the mold due to thermal expansion at the time of injection molding. Injection molding method for molded products.

(4) An upper die having an annular gate in which the tip heater of the probe provided in the runner portion through which the molten synthetic resin flows is built-in for intermittent heating, and the tip portion faces the gate. And a lower die that includes a core pin that is detachable from the tip of the probe that faces the upper mold annular gate, and that can form a cavity between the upper die and the core pin toward the outside of the core pin. An injection molding apparatus for a synthetic resin molded product having a shaft-shaped opening, wherein a molded product having an axial hole based on the above is obtained.

(5) The tip heater at the tip of the probe is configured so that the annular gate can be intermittently heated in connection with the injection molding operation, and the axial opening synthesis according to the above (4). Injection molding equipment for molded products.

(6) The axial pin synthetic resin molding according to the above (4), wherein the core pin is movably provided so as to absorb and absorb the expansion and contraction fluctuation of thermal expansion due to the temperature change of the injection molding resin. Injection molding equipment.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below.

In each drawing, 1 is an injection molding apparatus main body 2
The reference numeral 3 designates a desired injection means, and the molten resin injected by the injection means 3 is the manifold 1.
From the molten resin flow passage 4 of the runner hole 5 communicating with this
Is circulated through the cannonball-shaped probe 6 which is vertically passed through. Reference numeral 7 denotes a holding plate of an upper mold 8 for holding the probe 6, 9 denotes a cavity plate of the upper mold 8 arranged on the end face of the holding plate 7, and a molten resin reservoir formed in the cavity plate 9 stores the molten resin. Recess 10
Of the probe 6 on the locking step 10a provided on the outer periphery of the opening of the
The annular locking portion 11 of the tip end portion 6a of the outer peripheral portion is locked, and the nozzle 12 is opened in the lower central portion of the storage recess 10. And this nozzle 12
The tip portion 6a of the probe 6 is exposed, so that an annular gate 12a is formed in the nozzle 12. Incidentally, the runner hole 5 becomes two or more branch holes 5a and communicates with the reservoir recess 10 on the way, leaving the tip 6a of the probe 6.

Reference numeral 13 denotes a heater disposed on the outer periphery of the probe 6 except for the tip portion 6a thereof, which is provided to prevent the molten resin in the runner hole 5 including the branch hole 5a from being cooled and solidified. Reference numeral 14 denotes a chip heater arranged in the tip portion 6a, which can open the gate forming the annular gate 12a by heating and melting the resin stored in the annular gates 12a, or closing the gate by cooling and solidifying. As described above, it is constructed so that heating can be performed by intermittently energizing in association with the injection molding operation.

Reference numeral 15 is a lower mold which can be brought into contact with and separated from the upper mold 8 and 16 is a molded product which can be formed between the upper mold 8 and the periphery of the gate which receives the molten resin injected from the gate constituted by the annular gate 12a. Cavity shaped structure, 17
Shows a core pin that penetrates the cavity 16 at the center of the lower mold 15 and can be brought into contact with and separated from the tip portion 6a. The tip 17a of the core pin 17 can be engaged with and disengaged from the tip portion 6a of the probe 6 by a desired means. It has become.

Reference numeral 22 denotes an eject pin, which has a function of allowing a molded product to be ejected and taken out when separated.

Based on the above construction, the synthetic resin molding method of the present invention will be described with reference to FIGS.

First, as shown in FIG. 1, the lower mold 15 is closed with respect to the upper mold 8. That is, the core pin 17 of the lower mold 15 firmly holds the engaged state with the tip portion 6a of the probe 6, and the molten resin flow passage 4, the runner hole 5, the branch hole 5a and the storage recess 10 of the injection molding device 2 are It is filled with the desired molten resin (see FIG. 4A), and the heater 13 in the probe 6 maintains the energized state. However, since the resin of the gate portion of the annular gate 12a is cooled and solidified, the gate is closed.

In this state, when the injection molding operation is started,
First, the tip heater 14 in the tip portion 6a of the probe 6 is energized to locally heat the cooled and solidified resin in the annular gate 12a so that it melts instantly and the so-called gate opens vertically, and then a normal injection means not shown. 3, the molten resin passes through the gate of the annular gate 12a and the cavity 16
It is rapidly discharged into the inside and finishes the injection operation. That is, FIG.
The state of (c) is reached through the state of (b). After completion of this injection operation, the energization to the chip heater 14 is stopped, so that the resin in the gate portion of the annular gate 12a radiates heat.
The heat dissipation is transmitted through the core pin 17 and the heat dissipation effect is promoted, the heat is effectively cooled, and at that moment, the heat is solidified, the gate is closed, and the state shown in FIG.
Accurate molding is possible while maintaining moldability without causing problems such as sink marks.

In particular, the molten resin flowing in the upper mold 8 is
Since the discharge is discharged into the cavity 16 along the outer periphery of the core pin 17 along the tip 6a of the probe 6 forming the annular gate 12a of the gate portion, a weld line is not generated in order to generate a uniform concentric flow, and a uniform weld line is not generated. A molded product can be obtained.

Then, the upper mold 8 and the lower mold 15 are separated from each other, and the molded product A can be easily taken out by the eject pin 22 as shown in FIG.

In particular, since the resin in the annular gate 12a portion corresponding to the gate portion is cooled and solidified during the mold releasing operation, there is no inconvenience such as stringing with the molded product A and dripping at the gate portion. Can be molded efficiently.

By continuing the above operation, continuous injection molding operation by the runnerless hot runner system can be performed.

Next, referring to FIGS. 5 (a), 5 (b) and 5 (c), the tip 17a of the core pin 17 and the tip 6 of the probe 6 will be described.
Three examples of the structure for connecting and disconnecting with a will be described.

In (a), the tip 17a of the core pin 17 is formed in a hemispherical shape α, and a concave portion a having the same shape as the hemispherical shape α is formed.
Is formed in the distal end portion 6a of the probe 6 so as to ensure the engagement / disengagement operation.

In (b), the tip 17a of the core pin 17 is formed as a projecting portion β having a slightly small diameter, and a relatively long narrow hole b which can be engaged with the projecting portion β is formed in a recessed portion in the tip portion 6a. As in (a) above, the engagement / disengagement operation is ensured.

(C) is a structure in which a concave portion γ is formed at the tip 17a of the core pin 17, and the tip of the tip portion 6a is used as a protruding end c to disengage the concave portion γ from the protruding end c. I also ensure the engagement and disengagement operation.

Furthermore, based on FIGS. 6 (a), 6 (b) and 6 (c), 3 for solving the thermal expansion countermeasure of the core pin 17
An example will be described.

That is, in consideration of the escape of the core pin 17 which may be thermally expanded by the heating temperature working during the injection molding, (a) shows a coil spring for allowing the core pin 17 to be finely moved up and down by the lower mold 15. 18 is built in so as to absorb the amount of thermal expansion of the core pin 17, and (b) is modified by a leaf spring 19 having the same function as the coil spring 18. Also (c)
In the configuration of (b) of FIG. 5, without using an elastic material such as (a) and (b), the protrusion β of the core pin 17 can be moved with respect to the small hole b of the tip 6 a. With the fitting structure, the amount of thermal expansion of the core pin 17 can be absorbed.

Next, three examples in the case where the perforated molded article of the molded article is different are shown in FIGS. 7 (a), 7 (b) and 7 (c).

(A) shows a gear-shaped molded product A which is the same as that shown in the above embodiment. (B) is a battery sealing body B
The cooling water hole 20 is opened in the lower mold 15 to enhance the cooling effect. (C) shows the case where the hole-formed product is the cap C, and the core pin 17 has a large inner diameter of the cap C, and the cooling water flow passage 21 is provided inside the core pin 17 so as to effectively operate the cooling effect. There is.

In addition, although not shown, a cavity of a synthetic resin molded product having a shaft-shaped opening having a desired shaft-shaped opening configuration can be formed to obtain a desired injection-molded product.

[0033]

According to the present invention, in the hot runner system for injection molding, the tip heater of the probe facing the gate has a built-in chip heater for intermittent heating at each injection molding, and the shaft of the molded product. Open or close the gate by opening or closing the tip of the core pin capable of forming a hole-shaped or cap-shaped axially-perforated molded product by contacting or separating from the tip of the probe to melt or solidify the resin stored in the annular gate. At the time of closing the gate, stopping the energization to the chip heater and stopping the heating to the gate part, the heat of the resin in the vicinity of the gate escapes to the core pin and the cooling and solidification of the resin in the gate part is promoted. In addition, when the gate heater is energized to heat the tip of the probe to open the gate, the resin stored in the gate that maintains a low temperature is rapidly melted and the gate opening / closing operation is responsive. In addition to being able to be performed, the molten resin injected into the cavity flows the molten resin along the core pin, there is no weld line, and there is a need for post-processing such as correcting the unevenness of the gate traces of the upper hole molding. It is possible to obtain a highly accurate injection method of a synthetic resin molded product having an axial opening and an apparatus therefor.

[Brief description of drawings]

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

FIG. 2 is an enlarged cross-sectional view of the main part of FIG.

FIG. 3 is an exploded cross-sectional view showing a state where the molded product of FIG. 1 is taken out.

4 (a), (b), (c) Molding state diagram showing the molding process in the cavity during the molding operation.

5A, 5B, and 5C are cross-sectional views of a main part showing three examples of the contact / separation engagement / disengagement configuration of the core pin and the probe tip.

6A, 6B, and 6C are cross-sectional views of a main part showing three examples of measures against thermal expansion of the core pin.

7A, 7B, and 7C are cross-sectional views showing a main part of an injection molding apparatus for molding three examples of molded products.

[Explanation of symbols]

2 Injection molding machine body 5 runner holes 6 probes 6a Tip 8 Upper mold 12 nozzles 12a ring gate 14 Chip heater 15 Lower mold 16 cavities 17 core pins 17a tip A, B, C molded products

Claims (6)

[Claims] 1. A cavity formed between the lower mold and the upper mold annular gate which opens or closes the gate by melting or solidifying the molten resin by an intermittent heating operation, and forming the molten resin between the mold and the lower mold. When it is injected into the mold, it is made to flow along the outside of the tip of the core pin provided in the lower mold that engages and disengages with the center of the upper mold gate, and the upper mold and the lower mold are separated after cooling and solidification of the molten resin. An injection molding method of a synthetic resin molded product having a shaft-shaped opening is characterized in that a molded product having an axial hole based on the core pin is obtained. 2. The annular gate is formed such that the tip end portion of the probe having a built-in tip heater faces the central position of the upper die gate, and the tip heater is energized and heated during the injection operation of injection molding. , Melting the solidified resin facing the annular gate portion to open the gate, stopping the energization to the chip heater after the injection molding is completed, and solidifying the molten resin facing the annular gate portion to close the gate. The injection molding method for a synthetic resin molded product having a shaft-shaped opening according to claim 1. 3. The shaft-shaped open-hole synthetic resin molded product according to claim 1, wherein the core pin is axially movable so as to absorb a difference in expansion between the core pin and the mold due to thermal expansion during injection molding. Injection molding method. 4. An upper die having an annular gate in which a tip heater for intermittently heating is built in the tip of a probe provided in a runner portion through which a molten synthetic resin flows, and the tip of which faces a gate. , A lower die that is provided with a tip of the probe facing the annular gate of the upper die and a detachable core pin, and that can form a cavity with the upper die toward the outside of the core pin. An injection molding apparatus for a synthetic resin molded product having a shaft-shaped opening, characterized in that a molded product having a shaft hole based thereon is obtained. 5. A shaft-shaped open-hole synthetic molded product according to claim 4, wherein the tip heater on the tip of the probe is adapted to intermittently heat the annular gate in connection with the injection molding operation. Injection molding equipment. 6. The shaft-shaped open-hole synthetic resin molded article according to claim 4, wherein the core pin is movably provided so as to absorb and absorb the expansion and contraction fluctuation of thermal expansion due to the temperature change of the injection molded resin. Injection molding equipment.