JPS5944977B2 - injection mold - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the structure of an injection mold, and in particular to a mold in which a sprue is formed at a location other than the parting line of the mold, taking into consideration the strength of the injection molded product. This facilitates forming the sprue, cutting the gate, removing the sprue, and removing the molded product.

An injection mold is formed with a sprue portion connected to the molding cavity, and the sprue portion is composed of a gate, a runner, and a sprue when viewed from the product side. These sprues are used by selecting an appropriate cross-sectional volume and shape depending on the cavity volume, injection speed, press-fitting resin material, etc. Further, among these sprues, the gate and runner are generally formed on the parting line of the injection mold, and are formed so that they can be taken out together with the molded product when the mold is opened and the molded product is taken out. In addition, the gate and runner are selected depending on the volume and shape of the cavity as described above, and if these are not appropriate, resin filling may be insufficient, and whiskers, weld marks, flow marks, etc. may occur. Therefore, the shape of the molded product and its finish often depend on the shape and arrangement of the runner and gate. However, as described above, these gates and runners are generally formed on the parting line, and are selected to match the shape and volume of the cavity. Therefore, in order to prevent the above-mentioned defects, consideration has been given to making the gate thicker or giving it a special shape, and there is little consideration of where to form the sprue depending on the shape of the molded product. Nakatsuta. The main reason for this is that if the mold part for forming the sprue part is outside the parting line, a special mold for molding the sprue is required, and no measures have been taken for this structure and assembly. On the other hand, the present inventors have molded a T-shaped pipe joint 1 as shown in FIG. ing.

2 and 3 illustrate cores that enter the mold to form a core mold, and 4 also illustrate cores that enter from the other side, and these cores 2, 3, and 4 are respectively formed slidingly to form a core mold. form.

Note that although the cavity molding die is omitted in the figure, its parting line is formed at 10 as described above, making it easy to take out the molded product. In the T-shaped pipe joint 1 injection-molded in this manner, weld marks are likely to appear at the connecting corner (shoulder) 11 between the branch pipe and the main pipe, which is a factor in reducing the strength of the product. In addition, these weld marks not only impair the appearance of the product, but also cause the product to have lower strength than other parts. In particular, weld marks on the shoulder portion 11 of the pipe joint should be eliminated as much as possible. To this end, it is recommended to change the position of the sprue 5, and in particular, it was considered to provide the gate and runner outside the parting line so that the weld mark occurs outside the base of the branch pipe (shoulder 11). . However, the construction of a mold for forming gates and runners outside the parting line has not been developed as described above, and implementation has not been possible. The present invention has been made based on these circumstances, and provides a molding mold in which a sprue can be formed at a free position off the parting line in an injection molding mold.
Moreover, these sprues are automatically cut off when the mold is opened, and are also separated and discharged when the molded product is taken out.

And, such an injection mold is a movable side mold of a mold, and a sprue part and a molding sprue that are slidable in a direction orthogonal to the moving direction of the movable side mold are provided at the parting line part. A sprue mold for molding a part of the product is provided, a sprue is formed by the sprue mold and a fixed cavity plate, and when the mold is opened, the sprue is held in the sprue mold and slid away. At the same time, the holding sprue is configured to discharge the molded product at the same time as the molded product is taken out. The present invention will be explained below based on the drawings, which illustrate an injection mold for a pipe fitting 1 similar to that illustrated in FIG. The same applies. Moreover, since appropriate molds are used depending on the molded product, these can be freely changed and carried out according to the spirit of the description described above or later. FIG. 3 is a cross-sectional view showing the main part configuration of the injection mold according to the present invention, and is an explanatory view in which the molded product and the sprue molded part are shown in the same cross-section. FIG. 4 is an explanatory diagram of the operation when the mold is opened, FIG. 5 is an explanatory diagram of the operation of the sprue forming mold after the mold is opened, and FIG. 6 is an explanatory diagram of the operation showing molded product removal and sprue discharge. In these figures, the injection mold is composed of a fixed side mold 12 and a movable side mold 13 as shown in FIG. 3, and the fixed side mold 12 has a fixed side mounting plate 15 and a first cavity plate 16. , and a sprue bush 17 passing through them.
Reference numeral 18 is an inclined pin attached to the stationary mold 12, and is a sliding guide pin for the core 4, which will be described later.

Reference numeral 24 denotes a regulating plate of the sprue mold 14, which will be described later, and is attached to the first cavity plate 16.
is configured.

On the other hand, in the movable mold 13, a second cavity plate 19 and a receiving plate 20 are integrally formed, and ejector pins 25, 25 and a sprue ejector pin 26 are provided through these. These pins 25 and 26 are then attached to the ejector plate 21. Furthermore, a sprue mold 14 is slidably provided on the top surface (parting line portion) of the second cavity plate 19 to form a movable mold 13. The sprue mold 14 is formed to be slidable in a direction (left and right in the drawing) perpendicular to the retracting direction (downward in the drawing) of the movable mold 13, and its configuration is not shown. is the second cavity plate 19
The dovetail part of the sprue part forming die 14 is fitted into the dovetail groove provided on the side so as to be slidable. In addition, the sliding of the sprue mold 14 is regulated by its sliding end, and when it moves forward, that is, when it moves to the left in the drawing, it forms part of the molded product 1 and the runner 8 and gate 9 of the sprue. will be stopped. On the other hand, when it is retracted, that is, when it moves to the right side in the drawing, it is stopped by the mounting plate 14' attached to the edge of the second cavity plate 19. These sliding movements are caused by the operation cylinder 23 provided on the mounting plate 14' and the piston rod 22 of the cylinder 23.
This is done by fixing the end to the sprue mold. Further, a hole penetrating through the sprue mold 14 along the direction of movement of the movable mold 13 is formed approximately in the center of the sprue mold 14, and the hole has a large diameter on the sliding side and is open. A sprue lock pin 27 is inserted into the hole, and the pin 27 has a receiving bottom 30 and a flange 28 on its lower side, and these receiving bottom 30 and flange 28 are fitted into the large diameter hole. A coil spring 29 is disposed between the flange 28 and the top surface of the large diameter portion to constantly bias the sprue lock pin 27 toward the second cavity plate. Incidentally, when the sprue lock pin 27 is biased as described above, the top surface of the sprue lock pin 27 is recessed into the hole, and
The recessed space is a part of the sprue 1 forming the slug well portion 7. The sprue bush 1 formed on the stationary side mold 12 is placed in the forward position of the sprue mold 14.
The sprue forming hole No. 7 and the hole coincide with each other, and when the mold is retracted, the sprue ejector pin 26 provided on the movable mold and the sprue lock pin 27 coincide with each other. When the sprue lock pin 27 slides, its receiving bottom 30 slides along the sliding surface, and the top surface thereof forms an engaging stepped portion for holding the sprue. Note that this engagement step may be made flat if necessary, and engagement and retention may be performed by a circumferential groove provided on the inner periphery of the upper part of the hole. FIG. 3 shows these molding molds 12, 13, and 14 closed, and the cores 2, 3, and 4 as explained in FIG. The cross section of the joint 1 is shown,
The sprue mold 14 is held in the forward position and is firmly supported by a regulating plate 24 that constitutes the stationary mold 12.

The sprue 16 is formed in the sprue bush 17 at the sprue sprue, and the runner 8 and gate 9 are connected to the first sprue of the stationary mold.
It is formed by a cavity plate 16 and a sprue mold 14, and the slug well 7 is formed in the sprue mold 14. Figure 4 shows the initial state of the mold opening after molding, in which the cores 2 and 3 shown in Figure 1 are punched out on both sides and retracted, and the movable mold 13 is located downward in the drawing. Move to. Therefore, the core 4 is pulled out of the molding along the inclined pins 18, and the sprue part is removed from the bush 17 while being held in the sprue mold 14. Also, the sprue part mold 14
is released from the regulation plate 24. Then, the movable mold 13 is still separated from the stationary mold 12, and the core 4 is separated from the molded product 1 as shown in FIG. Further, the sprue mold 14 is slid and retracted by the operation of the cylinder 23, and the gate 9 of the sprue portion is cut by this retraction. The sprue lock pin 27 of the sprue mold 14 that has reached the retracted position aligns with the sprue ejector pin 26, as described above. Next, to take out the molded product 1, the ejector plate 21 shown in FIG. 1 operates to separate the molded product 1 from the second cavity plate 19 via the ejector pins 25, 25 as shown in FIG. Since the sprue ejector pin 26 is also attached to the ejector plate 21, the sprue ejector pin 26 also protrudes together with the pin 25. Then, the sprue ejector pin 26 directly pushes up the sprue lock pin 27, and the slug well 7 of the sprue held in the sprue mold 14 is pushed out and opened, and is discharged together with the sprue 6 and the runner 8. The mold from which the molded product has been taken out and the sprue has been discharged in this way is joined in the reverse order to the third stage.
The mold is closed as shown in the figure. As described above, the injection mold of the present invention is molded using a sprue mold that has a sprue portion slidably configured on the movable side mold, and
Since the sprue mold is configured to hold and retract the sprue and automatically discharge the sprue, the sprue can be provided at any position other than the parting line of the molded product, and the mold can be easily removed. In addition to improving the appearance, defects such as insufficient resin filling and whiskers can be prevented, and the weld mark can be removed from the parting line to obtain a high-quality molded product.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing an example of a molded product and shows conventional sprue formation, Fig. 2 is an explanatory diagram of a sprue formed by using the mold of the present invention on the molded product shown in Fig. 1, and Fig. 3 is a cross-sectional view of the structure of the injection molding mold of the present invention, FIG. 4 is an explanatory diagram of the operation of FIG. 3, and FIG.
The figures are also an explanatory view of the operation of FIG. 3, and a partial explanatory view of the movable mold, and FIG. 6 is an explanatory view of the operation of FIG. 5. 1...T-shaped pipe joint (molded product), 2, 3, 4.
... Core 1, 5 ... Sprue part, 6 ...
...Sprue 1, 7...Sluthugwell, 8...
...Runner, 9...Gate, 10...
...Parting line, 11...Shoulder, 12
...Fixed side mold, 13... Movable side mold, 14... Sprue part mold, 15... Fixed side mounting plate, 16... ...First cavity plate, 17...Sprue bush, 18...
- Inclined pin, 19... Second cavity plate, 20... Reception plate, 21... Ejector plate, 23... Cylinder 24...・
・・Regulation plate, 25・・・・Edge tap pin, 26・
...Sprue ejector pin, 27...
Sprue lock pin, 28...Flange, 29
......Coil spring, 30...Bottom.

Claims (1)

[Claims] 1. In an injection mold for molding with a sprue provided outside the parting line, the sprue mold provided on the movable mold of the mold is slidable in a direction perpendicular to the direction of movement of the movable mold. A slug well portion is formed in the sprue mold, and a sprue lock pin is provided in the slug well portion so as to be biased toward the retraction side, and the sprue lock pin prevents the sprue mold from separating from the molded product. When sliding away,
An injection molding mold characterized in that it is configured to face an ejector pin provided on a movable mold.