JPS6064821A - Injection molding apparatus - Google Patents

Abstract

PURPOSE:To provent a thick molded item when it is molded from generating sink marks or voids during the cooling and solidifying thereof and to increase the dimensional accuracy, by pressing a piston of a pressure-holding machine after the injection and filling into a mold to carry out a higher pressure-holding. CONSTITUTION:A mold 10 is opened at a position (D) and a molded item is removed. After the mold opening, hot water is supplied into a medium passage of the mold 10 until it comes to a position (A) by the rotation of a rotating body 1, so that the mold 10 is heated and the injection and filling of a resin 40 is carried out smoothly, and thereafter the mold 10 is water-cooled. Before the completion of cooling and solidification of the filled resin 40, the rotating body 1 is rotated a prescribed angle, the resin 40 at the tip of a nozzle 23 is cut, and the mold 10 filled with the resin 40 reaches a position (B) to face a pressure-holding machine 30. The forward end of a piston 32 is pressed into a cylinder section 14 of the mold 10 by driving the pressure-holding machine 30. Thus the pressure in a cavity 13 is kept high, and the resin 40 in the cylinder section 14 is supplemented into the cavity 13. Thus, after the injection and filling, since the piston of the pressure-holding machine is pressed into the mold to effect high pressure holding, even a thick molded item can be prevented from producing sink marks or voids.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus particularly suitable for producing thick-walled synthetic lubricant moldings.

Recently, injection molded products made of synthetic resin have tended to be thicker and thicker, and a high level of dimensional accuracy has been required, and conventional general injection molding equipment has not been able to meet this requirement. In other words, in the conventional device, the nozzle of the injection machine is applied to the resin passage of the mold, and the molten resin inside the cylinder of the injection machine is
The injection pressure generated by the 1111 rotation or rotation of the screw causes the resin to be injected and filled into the molding cavity through the resin passage of the mold, and then cooled and solidified to obtain a molded product. However, synthetic resins are prone to sink marks and voids due to heat shrinkage while being cooled and solidified in the mold, and this phenomenon becomes especially noticeable when molding products with a certain thickness.
It is difficult to achieve a high level of 1j method accuracy.

In order to solve this problem, it is sufficient to increase the resistance pressure of molten resin when it is injected into the mold, and to cool and solidify it while maintaining this state. Injection (many have been developed; however,
In an injection machine with a screw set, the higher the pressure, the larger the back 70 of molten resin from the screw slint becomes, making it difficult to obtain a light effect. In addition, there are known products that use check rings to prevent this backflow, but if check rings are used, synthetic resins with high melt viscosity, such as hard vinyl chloride resin, will suffer from burns due to stagnation of the synthetic resin. The problem is that it tends to occur. Furthermore, in such injection molding, there is the problem that the screw cannot be made very long due to the buckling strength of the screw material since the cross section of the screw is subjected to high pressure.

The above structure has not only a structural disadvantage but also a disadvantage that the molding cycle becomes longer due to the pressure holding time, which reduces productivity.

The purpose of the present invention is to eliminate the drawbacks mentioned in 1.The gist of the present invention is to provide an injection molding system that includes an injection machine, a pressure holding machine, and a mold that moves between the injection machine and the pressure holding machine. The press has a piston that moves forward and backward, the mold has a molding cavity and a part of the sill that communicates with the molding cavity, and the mold is injected with TJL fat into the cavity from injection 11!
The injection molding apparatus is moved to a pressure holding machine, and the piston of the pressure holding machine is press-fitted into a part of a cylinder of a mold.

Hereinafter, one embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a rotary type injection molding apparatus. In the figure, reference numeral 1 indicates a rotating body (I), and a large number of molds 10, for example, six molds, are provided on the periphery of the rotating body.

The rotating body 1 is configured to stop every time it rotates by a predetermined angle (in this example, 60 degrees), so that each mold 10
It is designed to stop at six locations A-F. An injection machine 20 is placed at the stop position A. The pressure retainer 30 is placed at the next stop position B and the next stop position C1.

The mold 10 includes one fixed mold and one fixed mold as shown in FIGS. 2 and 3.
1 and a mobile type 12. These fixed types 11. A molding cavity 13 is formed between the movable molds 12. Furthermore, a sill portion 14 whose inner peripheral surface is a cylindrical surface is formed at the joint between the fixed mold 11 and the movable mold 12.

The cavity 13 and the cylinder part 14 communicate with each other via a small diameter resin passage 15.

The injection machine 20 does not require particularly high injection pressure, and a general-purpose one can be used. The injection machine 20 is constructed as shown in FIG. That is, 21 is a barrel that accommodates the requisite melting resin 40. A nozzle 213 is formed in the front 22 of the barrel 21 .

Further, a screw 24 is housed inside the barrel 21.

The pressure retainer 3 ( ) is constituted by a piston cylinder as shown in the third and eleventh figure. That is, by supplying hydraulic pressure into the cylinder 31, the cylindrical piston 32 is moved forward and backward.

The outer diameter of the piston 32 is the same as or slightly smaller than the inner diameter of the cylinder part 14 described in 1. A circumferential groove 3 is provided at the tip of the piston 32.
3 is formed, and a ring 34 is attached to this circumferential groove 33. The ring 34 is made of heat-resistant rubber, heat-resistant synthetic resin, etc., and has five circumferential grooves 33 that have a certain degree of elasticity.
The inner diameter of the ring 34 before being attached to the circumferential groove 33 is formed to be slightly smaller than the outer diameter of the circumferential groove 33, so that the ring 34 is brought into close contact with the circumferential groove 33. The outer diameter of the ring 34 is the same or slightly larger than the inner diameter of the cylinder part 14 of the mold 10, so that when the tip of the piston 32 is press-fitted into the cylinder part 14 as described later, It comes into close contact with the inner peripheral surface of the cylinder part 1.1.

With the injection molding apparatus having the above configuration, i) creative molding is performed as follows. The mold 10 is opened at ◇ normal position 1), and the molded product is taken out here. 71, 14 After opening, until reaching stop position A due to rotation of li1 rolling element 1,
Hot water is supplied to the W and body passages of the mold 10, and the mold 10 is heated. Heating of the mold 10 is continued until just before completion of η·j light filling, which will be described later. Since the mold 10 is maintained at a high temperature, injection and filling of the resin/10 is carried out smoothly.

Once the mold 10 has stopped at the stop position A, the nozzle 23 of the injection machine 20 is connected to the opening of the shilling part 14 of the mold station 10, as shown in FIG. And screw 2
Due to the injection pressure generated by the rotation or advancement of 4, the i8 @ L6i oil 40 or 7 spools in the barrel 21 is released.
The cylinder parts 14, 13 and 11 are injected into the cavity 13 through the passages 15 and 15, respectively. 1. Immediately after the filling of the grease is completed, cooling water is supplied to the water channel of the mold 10 to cool the mold 10. Note that this cooling is continued until just before the mold is opened.

The rotating body 1 rotates by a predetermined angle before the resin 40 filled as described above is completely solidified by cooling. As a result, the 01 resin 40 at the tip of the /slug 23 is cut off, and the mold 10 filled with the resin 40 reaches the stop position B and faces the pressure holding machine 30. And holding pressure t!
130 causes the tip of the piston 32 to touch the mold 10.
is press-fitted into the shilling part 14 of. As a result, the inside of the cavity 13 is kept at a high pressure, and the resin 40 of the cylinder part 14 passes through the resin passage 15 to the cavity 13.
It is supplemented inside. Therefore, resin sink marks and voids caused by cooling are eliminated, and a molded product with a high level of dimensional accuracy can be obtained. In addition, in this pressure holding state, the ring 34 is in close contact with the circumferential groove 33 of the piston 32 and the inner circumferential surface of the silling part 14, so the high-pressure resin 40 comes into contact with the inner circumferential surface of the piston 32 and the silling part 14. It is possible to reliably prevent 8 from leaking out from between the cavities 13 and to reliably maintain a high pressure inside the cavity 13.

By rotating the body 1 again by a predetermined angle, it reaches the stop position C and faces the other pressure holder 30. Here, the same pressure holding as described above is performed.

After completing the second holding pressure, the mold 10 reaches the stop position l) by further rotating the rotating body 1 by a predetermined angle.
The mold is opened in two steps.

Note that the present invention is not limited to the first embodiment described above, and various embodiments are possible. For example, the mold may not rotate as in the first embodiment, but may move linearly and reciprocate between the injection machine and the holding pressure.

As explained above, in the injection molding apparatus of the present invention, the piston of the pressure holding machine is press-fitted into the mold after injection filling to perform high pressure holding, so when molding thick-walled products. Even in this case, it is possible to prevent sink marks and voids from occurring during the cold no-11 solidification process, and a high level of dimensional accuracy can be obtained. In addition, since high-pressure holding is performed by a pressure holding machine instead of an injection machine, productivity is improved by shortening the molding cycle by the time required for this holding time. Furthermore, since the injection machine does not require high pressure holding, a general-purpose machine can be used without requiring particularly high injection pressure, thereby eliminating the inconveniences associated with high injection pressure injection machines.

[Brief explanation of drawings]

Fig. 1 is a plan view of an injection molding apparatus which is an embodiment of the present invention, Fig. 2 is an enlarged sectional view of the mold and the injection mold, and Fig. 3 is an enlarged sectional view of the mold and the injection molding machine. 10... Mold, 13... Molding cavity, 14...
... Cylinder part, N0... Injection machine, 30... Pressure holding machine, 32.

Claims (1)

[Claims] The mold has a mold that moves between the injection machine and the pressure holding machine, and the pressure holding machine has a piston that moves forward and backward, and the mold has a molding cavity and a mold that moves between the injection machine and the pressure holding machine. It has a part of the cylinder that communicates with it, and during injection (the mold whose cavity is injected and filled with resin is moved to a pressure holder, and the piston of the pressure holder is press-fitted into a part of the cylinder of the mold). An injection molding device characterized by: