JPH0890601A - Multi-cavity mold device - Google Patents

Abstract

PURPOSE: To offer a balance in filling cavities without recourse to a temperature control and reduce the thickness of a manifold. CONSTITUTION: A resin flow to cavities is branched into eight in total through a primary runner 29, a secondary runner 30, and tertiary runners 31a, 31b disposed to be flush with each other. The tertiary runner 31a is a reverse tertiary runner turned back to the primary runner 29. The tertiary runner 31b is a forward tertiary runner directed oppositely to the runner 29. The diameter of the forward tertiary runner 31b is determined to be larger than that of the reverse tertiary runner 31a. Intrinsically, a resin flow to the forward tertiary runner 31b is not smooth in comparison with a resin flow to the reverse tertiary runner 31a. However, this tendency can be compensated with the setting of the diameters. Since the primary runner 29, the secondary runner 30, and the tertiary runners 31a, 31b are disposed to be flush with each other, a manifold 21 can be reduced in thickness.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-cavity mold apparatus used for resin injection molding.

[0002]

2. Description of the Related Art For example, in injection molding of a thermoplastic resin, a plurality of products are molded by one mold device. In this case, a plurality of product-shaped cavities are formed between the fixed mold and the movable mold that open and close each other. A sprue, which is one resin injection port provided in the fixed mold, causes resin to enter each cavity by a runner. Distribute.

FIG. 3 shows an example of the arrangement of runners in a multi-cavity mold apparatus. Eight mold tools are used, and the runner splits from sprue 1 to 2
The secondary runner 2, a secondary runner 3 that branches off from both ends of the primary runner 2, and a tertiary runner 4a, 4b that branches off from both ends of the secondary runner 3, respectively.
The third runners 4a and 4b communicate with the cavities 5a and 5b via a spear system which is a hot hot tip system. Sprue 1 to cavity 5a,
The distance to 5b is the same for all cavities 5a, 5b. The tertiary runners 4a and 4b have a reverse-direction tertiary runner 4a folded back to the primary runner 2 side and a forward-direction tertiary runner 4b heading to the opposite side. The cross-sectional diameter of the directional tertiary runner 4a and the cross-sectional diameter of the forward tertiary runner 4b were equal.

By the way, in a multi-molding die device,
When the resin is a thermoplastic resin having a low viscosity such as ABS resin or polystyrene, the filling balance of the resin between the cavities 5a and 5b becomes a problem. However, in the conventional mold apparatus, the primary runner 2 and the secondary runners 3 and 3 are
When the next runners 4a and 4b are located on the same plane,
There was a tendency for overfilling to occur in the cavity 5a located on the inner side, and underfilling for the cavity 5b located on the outer side. As a result, the molded products also have dimensional differences. This is a particular problem for thin-walled products such as videocassette shell cases.

As a means for eliminating such an imbalance in filling between the cavities 5a and 5b,
The temperature of the body of the spear system may be changed for each 5a and 5b. The result of the trial, for example, the inner cavity 5a
It was found that, when the temperature was set to 250 to 270 ° C., the temperature could be set to 40 to 50 ° C. higher in the outer cavity 5b to achieve the filling balance. However, if the temperature control is changed for each of the cavities 5a and 5b, this temperature control becomes troublesome.

Another means for eliminating the imbalance of filling is to raise the temperature of the resin itself to increase the fluidity of the resin. For example, the temperature of the body is 300 ~
If the temperature is set to 340 ° C., the filling balance can be considerably maintained without changing the temperature settings of the inner cavity 5a and the outer cavity 5b. However, increasing the temperature of the resin itself has many harmful effects.

On the other hand, depending on the layout of the runners,
Filling balance is also traditionally done. In fact, as shown in FIG. 4, a vertical portion 6 orthogonal to the primary runner 2 and the secondary runner 3 has been conventionally provided. Such vertical part 6
By providing, the filling balance can be achieved in each of the cavities 5a and 5b. However, when the runner is provided with the vertical portion 6, the mold apparatus becomes large.

[0008]

As described above, the secondary runner is bent from the tip of the primary runner, and the secondary runner is reversed from the tip of the secondary runner to the primary runner side. In the conventional multi-cavity mold device in which the forward-direction tertiary runner that branches toward the side is branched, since the cross-sectional area of the backward-direction tertiary runner and the cross-sectional area of the forward-direction tertiary runner are equal, Next runner and 3
When the secondary runner and the secondary runner are located on the same plane, there is a problem that the cavity communicating with the reverse tertiary runner and the cavity communicating with the forward tertiary runner cannot be balanced. On the other hand, in order to balance the filling, 1
Although a mold apparatus having a vertical portion provided between the secondary runner and the secondary runner has been conventionally used, the provision of the vertical portion causes a problem that the entire mold apparatus becomes large. Further, it is possible to change the temperature control for each cavity in order to achieve the filling balance, but this has a problem that the temperature control becomes troublesome.

The present invention is intended to solve such a problem, and provides a multi-cavity mold apparatus which can balance the filling of each cavity without depending on temperature control and can be downsized. The purpose is to

[0010]

In order to achieve the above object, the present invention comprises a plurality of mold bodies which are opened and closed to form a plurality of cavities between them when the molds are closed, and one mold body is provided with one resin. It has a runner that branches from the inlet to each of the cavities.The runner is a base runner on the resin injection port side, an intermediate runner bent from the tip of the base runner, and a branch from the tip of the intermediate runner. There is a reverse runner folded back to the base runner side and a forward runner facing the opposite side, and a plurality of these base runners, intermediate runners, reverse runners and forward runners are located on the same plane. In the mold apparatus, the cross-sectional area of the forward runner is larger than the cross-sectional area of the reverse runner.

[0011]

In the multi-molding die apparatus of the present invention, at the time of molding, a plurality of molds are closed to form a plurality of cavities between these molds, and the resin injected from one resin injection port of the molds. Is branched by a runner and filled in each cavity. In the runner, the resin bends from the base runner to the intermediate runner, and further branches from the tip portion of the intermediate runner into the backward runner and the forward runner, and goes to each cavity. By the way, when the base runner, the intermediate runner, the reverse runner, and the forward runner are located on the same plane, the forward runner heading to the opposite side is more resin than the reverse runner originally folded back to the base runner side. Is hard to flow. On the other hand, by making the cross-sectional area of the forward runner larger than the cross-sectional area of the reverse runner, the difference in the fluidity of the resin to these two runners is compensated, and the resin is evenly filled in each cavity. .

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the multi-cavity mold apparatus of the present invention will be described below with reference to FIGS.
In FIG. 2, 11 is a fixed type and 12 is a movable type. The fixed type 11 and the movable type 12, which are mold bodies, move vertically with respect to each other to open and close, and when the mold is closed, a total of eight cavities 13a,
It forms 13b between each other.

In the fixed mold 11, a first fixed side receiving plate 17 is fixed to the back side (upper surface in the drawing) of the fixed side mold plate 16 forming the cavities 13a and 13b, and the first fixed side receiving plate 17 is provided.
The second fixed side receiving plate 18 is fixed to the back side of the. Further, a fixed side mounting plate 20 attached to a fixed side platen of the injection molding machine is fixed to the back side of the second fixed side receiving plate 18 via a fixed side spacer block 19. A manifold 21 made of an integral member is located inside the fixed-side spacer block 19 and is located between the second fixed-side receiving plate 18 and the fixed-side mounting plate 20.
Fixed through 22. Further, one sprue bush 26, to which the nozzle of the injection molding machine is connected, penetrates the fixed side mounting plate 20 and is fixed to the manifold 21. The inside of the sprue bush 26 is a sprue 27 which is a resin injection port.

Further, inside the manifold 21, there are formed runners branching from the sprue 27 to each of the eight cavities 13a and 13b. As shown in FIG. 1, this runner has a cylindrical shape 0 that is coaxial with the sprue 27.
Secondary runner 28 and a cylindrical primary runner (base runner) that bifurcates vertically from the tip of this zero-order runner 28
29, and a cylindrical secondary runner (intermediate runner) 30 that branches vertically from both ends of the primary runner 29.
And cylindrical third runners 31a and 31b that vertically branch off from both ends of these secondary runners 30, respectively. The tip ends of these tertiary runners 31a and 31b are bent vertically to form the manifold 21 in the manifold 21. There are cylindrical outlets 32a and 32b that pass through to the surface of the second fixed side receiving plate 18. The 0th-order runner 28 and the outlets 32a and 32b have a direction parallel to the mold opening / closing direction of the fixed mold 11 and the movable mold 12, but the primary runner 29, the secondary runner 30 and the tertiary runner. 31a and 31b are located on a plane orthogonal to the mold opening / closing direction. The third runners 31a, 31
b is the reverse direction third runner (reverse direction runner) 31a folded back to the primary runner 29 side and the forward direction 3 going to the opposite side.
There is a secondary runner (forward runner) 31b, but the cross-sectional diameter a of the reverse tertiary runner 31a is 8 mm, whereas the cross-sectional diameter b of the forward tertiary runner 31b is 9 mm. . That is, the cross-sectional area of the forward-direction tertiary runner 31b is larger than the cross-sectional area of the reverse-direction tertiary runner 31a. Also, the diameter c of the outlet portion 32a of the reverse-direction tertiary runner 31a is 8 mm, and the diameter d of the forward-direction tertiary runner 31b is 9 mm.
mm. In addition, primary runner 29 and secondary runner
The diameter of 30 is also 9 mm, which is the same as the forward third runner 31b. The outer shape of the manifold 21 is the runner 28,
It follows the arrangement of 29, 30, 31a and 31b.
It is located between the next runners 41 and has recesses 33 on both sides.
In addition, the runners 28, 29, 30, including the outlets 32a, 32b,
31a and 31b are processed by a drill, but unnecessary portions of the holes formed by the drill are closed by an embedding 37 held by a screw 36. Further, as shown in FIG. 2, the runners 28, 29, 3 are provided on both sides of the manifold 21.
A sheathed heater 38 for heating the thermoplastic resin in 0, 31a, 31b is embedded.

The outlets 32a and 32b of the tertiary runners 31a and 31b communicate with the cavities 13a and 13b via a spear system 41, respectively. The spear system 41 penetrates the fixed side receiving plates 17 and 18 and
It has a bush 42 fixed to 21 and a body 43 built in this bush 42, and a heater is built in this body 43. And the third runner 31a
, 31b respectively communicate with the cavities 13a, 13b via the resin passage 44 and the gate 45 in the spear system 41, respectively. Each cavity from sprue 27
The paths to 13a and 13b are all equal. There is a chip located near the gate 45 at the tip of the body 43, and this chip contains a heater of a different system from the heater of the body 43.

In the movable die 12, a movable side receiving plate 52 is fixed to the back side (lower surface in the figure) of a movable side die plate 51 forming the cavities 13a and 13b. A movable side mounting plate that is mounted on the movable side platen of the injection molding machine is fixed to the back side of the plate 52 via a movable side spacer block. In addition, the movable side receiving plate 52
A protruding plate provided with a protruding pin 53 is movably provided between the movable plate and the movable mounting plate.

It should be noted that, in actual use, FIG. 1 and FIG.
The left-right direction is the vertical direction.

Next, the operation of the above configuration will be described. At the time of molding, the fixed mold 11 and the movable mold 12 are closed, and cavities 13a and 13b are formed between them, and the heat of ABS resin or polystyrene melted from the nozzle of the injection molding machine into the sprue 27. Inject a plastic resin. This resin is sprue 27, 0th runner 2
8, the primary runner 29, the secondary runner 30 and the tertiary runners 31a, 31b are distributed, and their outlets 32a, 32 are provided.
From b through the resin passage 44 of the spear system 41,
The cavities 13a and 13b are filled from 45. Then, after the resin filled in the cavities 13a and 13b, that is, the product is cooled and solidified, the fixed mold 11 and the movable mold 12 are opened, and the product is released by the ejection pin 53 and taken out. After that, the mold is closed again, and the above molding cycle is repeated.

By heating the heater 38 of the manifold 21 and the heater of the body 43 of the spear system 41, the resin in the runners 28, 29, 30, 31a, 31b and the resin passage 44 is constantly melted throughout the entire molding cycle. To be kept.
On the other hand, when the resin is filled in the cavities 13a and 13b, the resin of the gate 45 portion is melted by the heating of the chip of the spear system 41, and the gate 45 is opened. At this time, by cooling the chip of the spear system 41, the resin in the gate 45 portion is solidified and the gate 45 is closed.

By the way, as described above, the molten thermoplastic resin is bent vertically from the primary runner 29 to the secondary runner 30 in the manifold 21, and further in the reverse direction 3 from the tip of the secondary runner 30. Branch into the next runner 31a and the forward direction third runner 31b,
Head to 13b. At this time, since the primary runner 29, the secondary runner 30, and the tertiary runners 31a and 31b are located on the same plane, the reverse direction tertiary runner originally folded back to the primary runner 29 side due to the shape of the runner. Than 31a
It is difficult for the resin to flow to the forward runner 31b that faces the opposite side. However, in the above-described embodiment, the diameter a of the reverse-direction tertiary runner 31a is set to 8 mm, and the forward-direction tertiary runner 31a is
Since the diameters of the other runners including b were smaller than 9 mm, the difference in the fluidity of the resin to the reverse tertiary runner 31a and the forward tertiary runner 31b was compensated for,
The resin is evenly filled in both the cavity 13a communicating with the reverse-direction tertiary runner 31a and the cavity 13b communicating with the forward-direction tertiary runner 31b. In this way, the filling of the resin in each cavity 13 can be balanced without increasing the temperature of the resin or changing the temperature control for each of the cavities 13a and 13b. Therefore, it is possible to obtain a stable quality product having no difference in size and the like.

Further, since the primary runner 29, the secondary runner 30 and the tertiary runners 31a and 31b are located on the same plane, the manifold 21 can be made thin and the mold apparatus as a whole can be made compact.

It should be noted that the present invention is not limited to the above embodiment, and various modifications can be made. For example,
The mold apparatus of the above-mentioned embodiment has eight pieces, but the number of pieces is not limited to that. That is, the present invention, the tip end intermediate runner of the base runner is bent, and has a runner shape in which the forward runner directed toward the opposite side and the reverse direction runner folded back from the tip end of this intermediate runner to the base runner side, In addition, it is generally useful for a multi-cavity mold apparatus in which the base runner, the intermediate runner, the backward runner, and the forward runner are located on the same plane.

In the above embodiment, the hot runner mold device for opening and closing the gate by the spear system has been described as an example, but the present invention is a valve gate type hot runner mold for mechanically opening and closing the gate. It can also be applied to devices. When using the spear system, there is a restriction on the resin passage from the runner of the manifold to the spear system.
In the case of the valve gate type, the degree of freedom in designing the resin passage from the runner to the valve device is higher, so that the present invention can be more effectively implemented.

Further, the present invention can be applied not only to the hot runner mold device but also to the cold runner mold device.

[0025]

According to the present invention, the runner has a base runner on the resin injection port side, an intermediate runner bent from the tip of the base runner, and a branch from the tip of the intermediate runner to the base runner side. In a multi-cavity mold device having a folded back runner and a forward runner directed to the opposite side, these base runner, intermediate runner, reverse runner and forward runner are located on the same plane, Since the cross-sectional area of the forward runner is larger than the cross-sectional area of the reverse runner, it is possible to compensate for the tendency that the resin does not easily flow to the forward runner than the reverse runner. It is possible to balance the filling of each cavity without changing the temperature control and to evenly fill each cavity with resin. That. Further, as described above, since the runners are located on the same plane, the mold apparatus as a whole can be downsized.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a manifold showing an embodiment of a multi-cavity mold device of the present invention.

FIG. 2 is a vertical cross-sectional view of the same fixed mold side.

FIG. 3 is an explanatory front view of the layout of runners showing an example of a conventional multi-cavity mold device.

FIG. 4 is an explanatory side view of the arrangement of runners showing another example of the conventional multi-cavity mold device.

[Explanation of symbols]

 11 Fixed type (mold body) 12 Movable type (mold body) 13a, 13b Cavity 27 Sprue (resin injection port) 29 Primary runner (base runner) 30 Secondary runner (intermediate runner) 31a Reverse direction Third runner (reverse direction) Runner) 31b Forward third runner (forward runner)

Claims (1)

[Claims] 1. A plurality of mold bodies which are opened and closed to form a plurality of cavities between them when the molds are closed, and the mold bodies have runners branched from one resin injection port to the respective cavities. Is a base runner on the side of the resin injection port, an intermediate runner bent from the tip of this base runner, a reverse runner branched from the tip of this intermediate runner and folded back to the base runner, and an order toward the opposite side. In a multi-cavity mold device that has a direction runner and these base runner, intermediate runner, backward runner, and forward runner are located on the same plane, the cross-sectional area of the forward runner A multi-cavity mold device characterized by being made larger than the cross-sectional area of the runner.