JPH04102826U - In-mold gate cutting device for thermoplastic injection molding - Google Patents

Abstract

(57) [Summary] [Purpose] After injection molding the thermoplastic material into the cavity through the runner and gate, a relatively small force is required in the gate cutting operation to cut and remove the thermoplastic material solidified in the gate. To provide a gate cutting device capable of performing gate cutting with a gate and extremely easy to remove plastic material solidified within the gate. [Structure] An escape recess 6a is provided in the gate 6, and when the gate cut pin moves forward and reaches the 7' position, when the communication between the gate 6 and the cavity 3 is cut off, the connection between the gate 6 and the runner 5 is Configure so that communication is maintained.

Description

[Detailed explanation of the idea]

0001

[Industrial application field]

This invention is a method to obtain a molded product by injection molding a thermoplastic material into a mold. In industry, molten thermoplastic material is passed from a runner through a gate. When injected into the cavity and solidified, the plastic material solidified inside the sprue and The plastic material (molded product) that hardens inside the cavity hardens inside the runner and gate. This is a device to obtain molded products by cutting the parts connected by plastic materials. It is related to

0002

[Conventional technology]

FIG. 6 is a schematic cross-sectional view showing a conventional plastic injection mold. The mold of this example is made by combining cavity block 1 and core block 2. A cavity 3 is formed between them.

0003 Molten thermoplastic material is press-fitted from sprue 4 and passes through runner 5 to the gate. is injected into the cavity 3 from the port 6.

0004 When the molten plastic is cooled, it solidifies and becomes a molded product within the cavity 3. This molded product consists of plastic solidified in gate 6 and plastic solidified in runner 5. The solidified plastic inside the sprue 4 is removed from the mold in a connected form. be taken out.

[0005] Therefore, the part corresponding to gate 6 must be cut using nippers or a hot knife. This requires a great deal of effort.

[0006] Furthermore, if a precise shape is required, manual finishing of the cut part is required. It takes a lot of man-hours.

[0007] How to cut using a robot, how to cut by applying vibration, and how to cut using a laser beam. Although it is theoretically possible to cut using It is not practical because maintenance is not easy.

[0008]

[Problem that the idea aims to solve]

As a device that automatically or semi-automatically cuts the gate part in the mold, The configuration shown in 7 is possible.

[0009] A gate cut pin 7 is provided opposite the gate 6 and can be driven up and down in the figure. It is.

0010 Thermoplastic in cavity 3 and thermoplastic plus in gate 6 When the tick solidifies, drive the gate cut pin 7 upwards in the figure to cut the gate. It will be done. 8 in the figure is a sprue ejector pin for discharging the solidified sprue 4. It is connected to the gate cut pin 7 outside of the figure, and is connected to the gate cut pin 7 above and below in the figure. driven in the direction.

[0011] However, in the gate cutting device according to the prior art shown in Fig. 7, the following occurs. There are difficulties as described in .

0012 Molten plastic material press-fitted into a mold is mainly heated by the mold. is taken away, cooled, and solidified. For this reason, the molten plastic material in contact with the mold cools rapidly, forming a hard skin layer along the inner surface of the mold.

[0013] Since the above skin layer is formed, cut around the gate 6 with the gate cut pin 7. It's not easy to do. That is, sandwiched between hard skin layers, It is not easy to shear solidified plastic materials that are elastic.

[0014] Moreover, if you try to forcefully cut the solidified plastic material at this gate, isolated fragments (both the molded part and the plastic material solidified in the runner). If this occurs, the problem arises that the removal of this isolated fragment is not easy. There is also a problem.

[0015] This invention was developed in view of the above-mentioned circumstances, and allows gates to be cut with a relatively small force. gate cutting, which allows for easy removal of cut parts. The purpose is to provide equipment.

[0016]

[Means to solve the problem]

In order to achieve the above object, the in-mold gate cutting device according to the present invention has the following features: Into the cavity formed between the cavity block and core block Injection molding of molten thermoplastic material via runners and gates After that, in the device that cuts the gate part, A gate cover that is driven forward and backward toward the gate that communicates the cavity and the runner. A lock pin is provided. When the above gate cut pin retreats away from the gate, the cavity and The gate communicates with the runner, and the gate and the runner communicate with each other. When the gate cut pin moves forward in the direction approaching the gate, the cavity and Communication with the gate is cut off by the gate cut pin, The state immediately after the communication between the cavity and the gate is cut off by the gate cut pin. The structure is characterized in that the gate and the runner are in communication with each other.

[0017]

[Effect]

According to the above configuration, when the gate and the runner are in communication with each other, the gate and the cabinet are connected. It is possible to cut off the tee (gate cut). Using this effect, a. The inside of the layer other than the skin layer still has plasticity (semi-fluid state) and the gel The cut can be made by moving the cut pin forward. At this time, the gate The resistance to the pin is due to the reaction force that cuts the thin skin layer and the semi-fluid state of the plastic. The main purpose is flow resistance to cut the stick material, and no large force is required. .

[0018] b. The skin layer formed within the gate is separated from the molded part and The solidified plastic material remains connected within the screws and sprues. Therefore, it is easy to remove this together with the sprue. As a practical matter, When the sprue is removed using the sprue injector pin 8 shown in Figure 7, it will form inside the gate. The formed skin layer is removed together.

[0019]

【Example】

1 to 5 are cross-sectional views schematically depicting one embodiment of the device of the present invention.

[0020] Figure 2 shows the state before the injection process, where 3 is the cavity, 5 is the runner, and 6 is the gate. It is the default. The gate cut pin 7 is arranged to face the gate 6. and is driven in the vertical direction in the figure.

[0021] The gate 6 is provided with an escape recess 6a. This recess 6a is When the gate cut pin 7 moves forward and enters the gate 6, there is a gap between it and the tip. It is constructed to leave a gap. Regarding the method of setting the shape and dimensions of the escape recess 6a, FIG. 1 will be described later.

[0022] When the molten plastic material 9 is injected in the state shown in FIG. 2 above, the state shown in FIG. 3 is obtained. becomes.

[0023] The molten plastic material 9 then fills the cavity block 1 as shown in FIG. A thin and hard skin layer 10 is formed along the surface in contact with the core block 2. be done.

[0024] In this state, other than the skin layer 10 has not yet completed solidification and remains fluid. (has plasticity), insert the gate cut pin 7 as shown in Figure 1. The skin layer 10 formed within the gate 6 is formed within the cavity 3. Shear and separate from the skin layer. Since the skin layer 10 is thin, it requires less shearing. The power to do so is not great.

[0025] During this operation, the molten plastic material 9 separates without exhibiting much resistance. be done. At this time, the molten plastic material inside the gate 6 has fluidity. There is no risk of it becoming isolated fragments, and it flows into the runner 5 and is removed.

[0026] 7 indicated by a chain line in FIG. 1 is the position shown in FIG. 2, that is, the direction away from the gate 6. The position of the gate cut pin retreated in the direction is shown. 7' shown in solid line in Figure 1 is a gate cut advanced to block gate 6. It's a pin. Gate cut pin 7' in the forward position cuts off communication between gate 6 and cavity 3. However, since the gate 6 is provided with the escape recess 6a mentioned above (FIG. 2), , the gate 6 and the runner 5 maintain communication through the escape recess 6a.

[0027] When implementing the device of the present invention, the shape and dimensions of the above relief recess 6a are as follows. Set. That is, Located opposite the tip of the gate cut pin 7' in the forward position, Although it is isolated from the cavity 3 by the gate cut pin 7', It is not isolated from the runner 5 by the gate cut pin 7'. This fulfills the function described above.

[0028] After cooling and solidifying the molten plastic material 9 in the state shown in Figure 1, the gate cover is When the stop pin 7 is retreated downward in the figure, the state shown in FIG. 5 is achieved. In other words, The molded product in bit 3 is separated from the solidified plastic material in gate 6. It is now a complete product.

[0029] The skin layer formed within gate 6 (indicated by a chain line) is formed within runner 5. It is connected to the skin layer (indicated by a chain line).

[0030] The plastic material solidified in the runner 5 above solidified in the sprue (not shown). Since it is connected to the plastic material, the inside of gate 6 will be removed during the sprue removal operation. The solidified plastic material (consisting primarily of a skin layer) hardens in the runner 5. automatically removed along with any plastic material that has become oxidized.

[0031] The effects described above with respect to FIGS. An escape recess 6a is provided in the gate 6, and this escape recess is connected to the gate cut pin 7'. is isolated from the cavity 3 and maintains communication with the runner 5. It was done by this.

[0032]

[Effect of the idea]

Into the cavity formed between the cavity block and core block Injection molding of molten thermoplastic material via runners and gates After that, the present invention is applied to a device that cuts the gate part, A gate cover that is driven forward and backward toward the gate that communicates the cavity and the runner. A lock pin is provided. When the above gate cut pin retreats away from the gate, the cavity and The gate communicates with the runner, and the gate and the runner communicate with each other. When the gate cut pin moves forward in the direction approaching the gate, the cavity and Communication with the gate is cut off by the gate cut pin, The state immediately after the communication between the cavity and the gate is cut off by the gate cut pin. If the gate and runner are configured to communicate with each other in the Gate cuts can be made and removed parts are extremely easy to remove. It is.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing one embodiment of the device of the present invention, with a gate cut pin in an advanced state.

FIG. 2 is a sectional view similarly depicting the state before molten plastic is injected into the cavity 3 from the gate 6.

FIG. 3 is a sectional view similarly depicting the state immediately after the molten plastic material 9 is injected into the cavity 3. FIG.

FIG. 4 is a cross-sectional view similarly depicting a state in which the molten plastic 9 is cooled and a skin layer 10 is formed.

FIG. 5 is a cross-sectional view showing a state in which the gate cutting pin 7 is retreated after finishing the gate cutting.

FIG. 6 is a schematic cross-sectional view of a mold shown to explain a gate cutting device according to the prior art.

FIG. 7 is a sectional view for explaining a conventional mold having a structure including a gate cut pin and its problems.

[Explanation of symbols]

1 Cavity block 2 Core block 3 Cavity 4 Sprue 5 Runner 6 gate 6a Escape recess 7 Gate cut pin 8 Sprue ejector pin 9 Molten plastic material 10 Skin layer 11 Solidified plastic material

Claims (1)

[Scope of utility model registration request] Claim 1: An apparatus for injection molding a molten thermoplastic material into a cavity formed between a cavity block and a core block via a runner and a gate, and then cutting the gate portion. , a gate cut pin is provided that is driven forward and backward toward the gate that communicates the cavity and the runner.
When the gate cut pin retreats in the direction away from the gate, the cavity and the gate communicate with each other, and the gate and the runner communicate with each other, and when the gate cut pin moves forward in the direction approaching the gate, the cavity and the gate communicate with each other. Communication with the gate is cut off by the gate cut pin,
An in-mold gate cutting device for thermoplastic injection molding, characterized in that the gate and runner are in communication with each other immediately after the communication between the cavity and the gate is cut off by a gate cut pin.