JP3712965B2 - Injection mold - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an improvement of an injection mold for injection molding of a plastic product, and particularly relates to measures for degassing.
[0002]
[Prior art]
In general, when plastic products are injection-molded, gas in the cavity is released from the mold mating surface of the mold so that voids do not occur in the injection-molded plastic products. For example, as disclosed in Japanese Patent Application Laid-Open No. 10-44198, a degassing pin is inserted so as to reach the cavity, and the gas in the cavity is separated from the gap around the degassing pin. 2. Description of the Related Art An injection mold that is allowed to escape from the mold is known. In this injection mold, the gas vent pin is inserted at a position away from the gate communicating with the cavity.
[0003]
[Problems to be solved by the invention]
Incidentally, in the case of the runner and the gate against one cavity is provided with a plurality, it is the timing to be injected into the cavity of the molten resin is different by each runner and gate. In this case, if molten resin is injected from a certain runner and gate into the cavity a little earlier than the other runners and gates, the gas in the cavity moves to the other runners and gates. When molten resin is injected from the runner and gate into the cavity, the gas transferred to the other runner and gate side returns to the cavity and voids are generated in the injection-molded plastic product.
[0004]
Moreover, in the injection molding die of the above publication example, an insertion hole for inserting the gas vent pin must be formed, and a separate gas vent pin is required, and accordingly, The mold structure becomes complicated and expensive.
[0005]
The present invention has been made in view of such a point, and an object of the present invention is to injection-mold a sound plastic product having no voids without a cost with a simple mold structure.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, the present invention is characterized in that the mold structure around the runner is devised.
[0007]
Specifically, the present invention relates to a molten resin in which one cavity is formed in a mold composed of a first mold and a second mold, and is injected from a plurality of valve gate ports provided in the second mold. The following solutions are aimed at injection molds for molding plastic products by injecting the mold into the cavity through a plurality of concave runners provided on the mold mating surface of the first mold with the second mold. Measures were taken.
[0008]
That is, a first aspect of the present invention, above the first type and at least one of die matching surface of the mold matching surface of each of the second type is passed through one end communicated to the respective runner in each runner A plurality of gas escape grooves for discharging gas out of the mold are provided in each runner, and the gas gate shifts to the runner on the valve gate port side with a low injection timing due to the injection timing difference of the molten resin injected from each valve gate port. The gas in the cavity is configured to be discharged out of the mold from the gas escape grooves .
[0009]
According to the above configuration, in the first aspect of the invention, the gas transferred from the cavity to the runner is quickly discharged out of the mold through the plurality of gas escape grooves and is not returned to the cavity. Sound plastic products without injection are injection molded.
[0010]
Further, since only the gas escape groove is provided in the die-matching surface, the cost is not so high with a simple die structure without significantly remodeling the die structure.
[0011]
According to a second aspect of the present invention, in the first aspect of the present invention, the other end of the gas escape groove is a runner on at least one of the mold matching surfaces of the first mold and the second mold. It is characterized by communicating with a collecting groove that is recessed along the periphery.
[0012]
With the above configuration, in the invention according to the second aspect, since the gas flowing into the gas escape groove is introduced into the collecting groove, the gas venting effect is increased.
[0013]
The invention according to claim 3 is the invention according to claim 1, wherein either one of the first mold and the second mold is provided with a pressurized gas passage for gas suction leading to the gas escape groove. It is characterized by.
[0014]
With the above configuration, in the invention described in claim 3, when the pressurized gas flows through the pressurized gas passage, the gas escape groove becomes negative pressure, the gas in the runner is forcibly sucked, and the degassing effect is obtained. Further increase.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0016]
FIG. 1 is a cross-sectional view showing a clamping state before injection in an injection mold 1 according to an embodiment of the present invention. The injection mold 1 includes a first mold 3 that is a movable mold and a second mold 5 that is a fixed mold, and a clamped state is provided between the first mold 3 and the second mold 5. A cavity 7 for molding a plastic product (not shown) is formed. A plurality of concave runners 9 communicating with the cavity 7 via the gate 8 in a clamped state are provided on the mold matching surface 3a of the first mold 3 with the second mold 5 (only one appears in the figure). Is formed.
[0017]
A manifold block 13 having a hot runner 11 is fixed to the back surface of the second mold 5, and one end of the hot runner 11 is connected to a nozzle of an injection molding machine (not shown).
[0018]
Valve mounting holes 15 are formed at locations corresponding to the runners 9 of the second mold 5, and gate valves 17 are mounted in the valve mounting holes 15. The gate valve 17 includes a valve box 21 having one end opened and the other end opened to the runner 9, and a heater 19 attached to the outer periphery. The opening is covered and sealed with the manifold block 13.
[0019]
Further, the other end of the hot runner 11 is connected to the valve box 21, and molten resin R (see FIG. 3) is supplied from the injection molding machine through the hot runner 11 into the valve box 21. Yes. The molten resin R supplied into the valve box 21 is secured in a molten state by the heat of the heater 19.
[0020]
Further, a gate pin 23 is disposed in the valve box 21 with a tapered tip 23a corresponding to the valve gate port 21a. A disc-shaped spring seat 25 is attached to the axial center of the outer periphery of the gate pin 23, and a coil spring 27 is mounted between the spring seat 25 and the bottom surface of the recess 13 a of the manifold block 13. .
[0021]
The gate pin 23 is urged toward the runner 9 by the spring force of the coil spring 27 to cause the tapered tip 23a to enter the valve gate port 21a, and the valve gate port 21a is closed by the gate pin 23 (see FIG. 1). Then, the resin pressure of the molten resin R supplied into the valve box 21 through the hot runner 11 acts on the spring seat 25 so that the gate pin 23 resists the spring force of the coil spring 27 and the second mold 5 Retract to the back side, remove the tapered tip 23a from the valve gate port 21a, open the valve gate port 21a (see FIG. 3), and inject the molten resin R into the cavity 7 through the runner 9 to mold a plastic product. It is supposed to be. In the gate valve 17, the gate pin 23 is advanced and retracted by the spring force of the coil spring 27 and the resin pressure. However, the present invention is not limited to this, and the advance / retreat mechanism may be hydraulic or electromagnetic.
[0022]
On the other hand, on the first mold 3 side, a plurality of ejector pins 29 are arranged corresponding to the runners 9. Although not shown, the base end of the ejector pin 29 is attached to an ejector plate disposed so as to be able to come into contact with and separate from the first mold 3 by an expansion and contraction operation of a hydraulic cylinder fixed to the back surface of the first mold 3. The tip of the ejector pin 29 is inserted into the insertion hole 31 of the first mold 3 so as to be able to protrude and retract with respect to the runner 9, and the ejector pin 29 (ejector plate) is advanced by the contraction operation of the hydraulic cylinder (not shown). By operation, the runner scrap in which the molten resin R is solidified in each runner 9 is removed from each runner 9.
[0023]
As shown in FIG. 2, a feature of the present invention is that, as shown in FIG. 2, the mold matching surface 3a of the first mold 3 and the second mold 5 are connected to the runner 9 at one end, and the gas in the runner 9 is passed through a mold. 1 is provided with a plurality of recessed gas escape grooves 33, and a substantially U-shaped collective groove 35 is recessed along the periphery of the runner 9 around the outer periphery of the gas escape grooves 33. The other end of 33 communicates with the collecting groove 35. The depth and width of the gas escape groove 33 are preferably 0.1 mm to 0.2 mm. If the thickness is less than 0.1 mm, the gas escape will be worse, while if it exceeds 0.2 mm, the molten resin R will easily enter the gas escape groove 33. The width of the collecting groove 35 is preferably 2 mm to 6 mm. This is because, if it is less than 2 mm, the amount of gas flow decreases, while if it exceeds 6 mm, the surface pressure during mold clamping must be increased in order to ensure sealing performance. The depth of the collecting groove 35 is preferably 3 mm to 6 mm. This is because if the diameter is less than 3 mm, the gas flow rate decreases, while if it exceeds 6 mm, the collecting groove 35 may be crushed by the surface pressure when closing the mold.
[0024]
The first mold 3 is formed with a gas suction pressurized gas passage 39 communicating with one of the gas escape grooves 33 via the collecting groove 35 and the communication hole 37. A pressurized gas such as pressurized air is circulated at a high speed as indicated by broken line arrows in FIG. 2 so that the gas in the runner 9 is sucked by setting the collecting groove 35 and the gas escape groove 33 to a negative pressure. .
[0025]
Next, the procedure for injection molding of a plastic product using the injection mold 1 according to this embodiment will be described.
[0026]
(1) As shown in FIG. 1, the first mold 3 is moved closer to the second mold 5 and the injection mold 1 is clamped. In this state, the gate pin 23 of the gate valve 17 is advanced by the spring force of the coil spring 27, and the tapered tip 23a enters the valve gate port 21a to close the valve gate port 21a. The ejector pin 29 is retracted by an extension operation of a hydraulic cylinder (not shown) fixed to the back surface of the first die 3, and the tip of the ejector pin 29 is immersed in the insertion hole 31 without advancing into the runner 9. Further, the pressurized gas flows through the pressurized gas passage 39 so that the gas escape groove 33 and the collecting groove 35 are set to a negative pressure.
[0027]
(2) As shown in FIG. 3, molten resin R is injected from an injection molding machine. The injected molten resin R is supplied into the valve box 21 of the gate valve 17 through the hot runner 11, and the resin pressure of the molten resin R acts on the spring seat 25 so that the gate pin 23 becomes the spring force of the coil spring 27. The taper tip portion 23a is retracted against the valve gate port 21a, and the valve gate port 21a is opened. Thereby, the molten resin R is injected into the cavity 7 through the plurality of runners 9 and the gate 8. At this time, if the injection timing of the molten resin R injected into the cavity 7 by the plurality of runners 9 and the gate 8 is different, the gas moves together with the molten resin R to the runner 9 having a low injection timing. Since the gas escape groove 33 and the collective groove 35 are at negative pressure due to the pressurized gas flowing through the pressurized gas passage 39, the gas escape groove 33 and the collective groove 35 are sucked into the runner 9 and are not collected.
[0028]
(3) The injection of the molten resin R from the injection molding machine is stopped, and the screw of the injection molding machine is advanced to hold the pressure in the cavity 7 for a while, and then the holding pressure is released. As a result, the resin pressure in the valve box 21 is released, and although not shown, the gate pin 23 advances by the spring force of the coil spring 27, the tapered tip 23a enters the valve gate port 21a, and the valve gate port 21a closes. .
[0029]
(4) When the molten resin R is solidified in the cavity 7 and the plastic product is injection molded, the first mold 3 is moved backward to open the mold 1 for injection molding. From this state, the ejector pin 29 is The runner scrap is advanced by contraction operation of the hydraulic cylinder (not shown), and the runner scrap in which the molten resin R is solidified in the runner 9 is removed from the runner 9. The advancement operation of the ejector pin 29 is performed simultaneously with the protruding operation of an ejector pin (not shown) for plastic products.
[0030]
Thus, in the above-described embodiment, a plurality of gas escape grooves 33 are formed in the mold matching surface 3 a of the first mold 3 and the second mold 5, and one end of each gas escape groove 33 is formed in the runner 9. Because of the communication, the gas transferred from the cavity 7 to the runner 9 is quickly passed from between the mold matching surface 3a of the first mold 3 and the mold matching surface 5a of the second mold 5 through the plurality of gas escape grooves 33. Therefore, it is possible to prevent the product from being discharged out of the mold 1 so as to return to the cavity 7 and injection molding a healthy plastic product without voids.
[0031]
Further, in the above-described embodiment, it is only necessary to provide the gas escape groove 33 on the die mating surface 3a of the first die 3 with the second die 5, so that a simple die can be obtained without significantly remodeling the die structure. The structure can be less expensive.
[0032]
Furthermore, in the above-described embodiment, the other end of the gas escape groove 33 is communicated with the collecting groove 35 that is recessed along the periphery of the runner 9 on the die-matching surface 3 a of the first die 3 with the second die 5. Therefore, the gas flowing into the gas escape groove 33 can be introduced into the collecting groove 35 to increase the degassing effect.
[0033]
In addition, in the above embodiment, since the pressurized gas passage 39 communicating with the gas escape groove 33 is formed in the first mold 3, the gas escape groove is formed by the pressurized gas flowing through the pressurized gas passage 39. It is possible to further increase the degassing effect by making 33 a negative pressure and sucking the gas in the runner 9.
[0034]
In the above embodiment, the gas escape groove 33 is recessed in the mold matching surface 3a of the first mold 3 with the second mold 5, but the mold matching surface 5a of the second mold 5 with the first mold 3 is provided. In addition, the gas escape groove 33 may be provided in the mold matching surfaces 3 a and 5 a of the first mold 3 and the second mold 5. However, since the second mold 5 is equipped with a gate valve 17 which is a separate member, it is possible to cause a situation in which the gas escape groove 33 cannot be reliably communicated with the runner 9 due to dimensional tolerances or the like. It is desirable to provide a gas escape groove 33 on the first mold 3 side.
[0035]
In the above embodiment, the collecting groove 35 is recessed in the first mold 3. However, as in the case of the gas escape groove 33, the collecting groove 35 may be recessed on the second mold 5 side. You may make recessed in both 3 and the 2nd type | molds 5. FIG. Further, it is not necessary to connect the other ends of all the gas escape grooves 33 to the collecting groove 35. However, it is better to connect all the gas releasing grooves 33 to the collecting groove 35 as in the embodiment. This is desirable.
[0036]
Furthermore, in the above embodiment, the pressurized gas passage 39 is indirectly communicated with the gas escape groove 33 via the collecting groove 35, but the pressurized gas passage 39 is communicated directly with the gas escape groove 33. Also good.
[0037]
In addition, in the above embodiment, the inside of the cavity 7 is held on the injection molding machine side, but the ejector pin 29 is not shown in the state where the valve gate port 21a is closed by the gate pin 23 after the injection process. The cavity 7 may be advanced by contraction operation of the hydraulic cylinder, and the inside of the cavity 7 may be held through the runner 9. Since the valve gate port 21a is closed by the gate pin 23, the molten resin R does not solidify and remain in the valve gate port 21a at the time of demolding. Further, while the inside of the cavity 7 is maintained with the ejector pin 29, the injection molding machine can move to the cooling / metering process, which is the next process, so that the molding cycle time can be shortened.
[0038]
【The invention's effect】
As described above, according to the first aspect of the present invention, the gas escape grooves each having one end communicating with each runner are provided in the die-matching surface, and a plurality of recesses are provided for each runner. The mold can be quickly discharged out of the mold through the groove, preventing the gas from returning to the cavity and injection-molding a healthy plastic product without voids. In addition, since the gas escape groove is simply provided in the die-matching surface, the cost can be reduced with a simple die structure.
[0039]
According to the invention of claim 2, since the other end of the gas escape groove is communicated with the collective groove formed along the periphery of the runner of the die mating surface, the gas flowing into the gas escape groove is introduced into the collective groove. Thus, the degassing effect can be increased.
[0040]
According to the invention of claim 3, since the pressurized gas passage leading to the gas escape groove is provided in the first mold or the second mold, the gas venting effect can be further increased by sucking the gas in the runner. .
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a state of mold clamping before injection in an injection mold according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view taken along the line II-II in FIG.
FIG. 3 is a cross-sectional view showing a state of an injection process in the injection mold according to the embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Injection mold 3 1st type | mold 3a, 5a Mold matching surface 5 2nd type | mold 7 Cavity 9 Runner 21a Valve gate port 33 Gas escape groove 35 Collecting groove 39 Pressurized gas path R Molten resin

Claims (3)

Cavity is formed one on configured die in a first type and a second type, the second type of molten resin injected from the plurality of valve gate opening provided in the second type of the first type An injection mold for molding a plastic product by injecting into a cavity through a plurality of concave runners provided on the mold-matching surface,
At least one of the mold matching surfaces of the first mold and the second mold is connected to each runner at one end, and a gas release groove for discharging the gas in each runner out of the mold. A plurality of recesses are provided for each runner , and the gas in the cavity that has moved to the runner on the valve gate port side with a slow injection timing due to the injection timing difference of the molten resin injected from each valve gate port is discharged from each gas escape groove. An injection mold characterized by being configured to be discharged out of the mold. An injection mold according to claim 1, wherein
The other end of the gas escape groove communicates with a collecting groove that is recessed along the peripheral edge of the runner on at least one of the mold matching surfaces of the first mold and the second mold. Mold for injection molding. An injection mold according to claim 1, wherein
An injection mold, wherein either one of the first mold and the second mold is provided with a pressurized gas passage for gas suction leading to a gas escape groove.

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