JPS6357212B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a screw type injection device used for injection molding of synthetic resin molded products.

Conventionally, a wide variety of synthetic resin molded products have been molded from various thermoplastic and thermosetting resins, and many of these molded products are manufactured using a so-called in-line screw injection device. In this in-line screw type injection device, as shown in Fig. 1, a molding material 1a such as resin pellets and coloring agent is heated and melted in a cylinder 2, and a bladed screw 3 is rotated to mix the molding material 1a. After kneading and pressure feeding, the rotation of the screw 3 is stopped and the screw 3 is moved forward to increase the pressure inside the cylinder 2, and the molten material 1 is poured into the mold 5 through the nozzle 4.
It is designed to eject b. The screws 3 and cylinder 2 are installed on a base 7 that is slid by a shift cylinder 6, and the screw 3 is driven by an injection cylinder 8 that is also installed on the base 7. It is becoming more and more common. Then, when the screw 3 is rotated again, the screw 3
The screw 3 is pushed back by the reaction force of the molten material 1b accumulating at the tip of the screw 3, and the limit switch 9 regulates the amount of retreat, and by stopping the rotation of the screw 3 at a certain position, the next injection amount can be adjusted. has been decided.

When manufacturing minute molded products, screw 3
It is desirable to reduce the size of the screw 3 according to the molded product, but it is difficult to miniaturize the screw 3 due to mechanical constraints, making it impossible to precisely control the injection amount and reducing the incidence of defective products. The disadvantage is that it is expensive. Therefore, the distribution of the molten material 1b within the mold 5 must be adjusted by increasing the amount of the molten material 1b remaining in the spool and runner, which serve as passageways for introducing the molten material 1b into the mold 5. However, there are problems in that the yield of the molten material 1b is extremely poor and the cooling time is long.

In order to solve these problems, the present applicant has already published Japanese Patent Application No. 174270-1981 regarding a screw-type injection device that enables accurate and precise control of the injection amount when manufacturing minute molded products, for example. I have applied. It consists of a cylinder equipped with a nozzle and a hopper, a screw blade that rotates at a fixed position within the cylinder to pump the molding material, a screw that has a through hole along its axis, and a screw that rotates at a fixed position in the cylinder and has a through hole along the axis, and a screw that can move freely back and forth within the through hole of the screw. It is equipped with a plunger provided. However, like the conventional injection device shown in FIG. 1, this improved injection device also requires two cylinder mechanisms, one for injection and one for shifting.

The purpose of the present invention is to replace the two cylinder mechanisms used in conventional injection devices, one for injection and one for shift, into one.
The overall structure has been simplified by allowing multiple cylinder mechanisms to be used in common, thereby significantly reducing manufacturing and operating costs.In addition, it is small, lightweight, and high-performance, making it possible to mold minute molded products with high precision. The objective is to provide a high-precision screw type injection device, the gist of which is to provide a cylinder that heats and melts the molding material, and a screw that rotates at a fixed position within the cylinder and pumps the molding material to the nozzle side of the cylinder. In the injection device, a plunger having an injection hole in the axial direction between the nozzle part of the cylinder and the mold is slidably fitted into the cylinder, and a drive mechanism drives the plunger in the axial direction. The invention is characterized in that the cylinder and screw drive motors are connected to a fixed base.

The present invention will be explained in detail below based on the embodiments shown in FIG. 2 and below.

In FIG. 2, 10 is a hopper for supplying the molding material 11, 12 is a cylinder for melting the molding material, and this cylinder 12 has a nozzle portion 1 at its tip.
2a, and a screw 13 having screw blades 13a is rotatably built inside. In this case, the screw 13 is rotated in a fixed position relative to the cylinder 12, and the cylinder 12 and the screw blade 1 are rotated in a fixed position.
3a and the screw barrel 13b, the volume of the space surrounded by the screw barrel 13b gradually decreases toward the tip of the screw 13.

A plunger 14 is inserted into the nozzle portion 12a of the cylinder 12 so as to be slidable with respect to the cylinder 12, and a molten material 11b melted by a heating device 16 is ejected from an injection hole 15 bored in the axial direction of the plunger 14. It is designed to be injected into a mold 17.

The driving electric motor 18 that rotates the screw 13 and the cylinder 12 are installed on a common base 19, and a single cylinder mechanism 20 consisting of a hydraulic or pneumatic cylinder is used to move the cylinder 12 in the axial direction onto a sliding surface 21. 19 is designed to slide. Further, 22 and 23 are power transmission gears of the driving electric motor 18. Although not shown in the drawings, it goes without saying that peripheral devices such as control devices such as the heating device 16, drive motor 18 or cylinder mechanism 20, and a limit switch that detects the amount of movement of the base 19 are arranged. be.

Here, the plunger 14 must be installed in such a way that it can be easily replaced, since it is necessary to prevent the plunger 14 from accidentally escaping from the cylinder 12, and to change the injection amount, plunger diameter, etc. depending on the molded product. Figure 3 shows a practical installation example to facilitate the installation and removal of the cylinder 12.
The plunger 14 is slidably fitted into the mounting tube 24 screwed onto the tip of the cylinder 12, and the plunger 14 can be replaced by removing the attachment tube 24 from the cylinder 12.

In this case, the inner diameter of the distal end portion 24a of the mounting tube 24 is made smaller than the inner diameter of the rear end portion 24b, and the large diameter portion 14a for preventing the plunger 14 from coming off is provided at the rear end portion of the rear end portion 24b. Since the plunger 1 is fitted inside, unless the mounting tube 24 is removed, the plunger 1
4 will never escape. Although this shows only one example of the mounting method, since the plunger 14 can be attached and detached at will and should be mounted in such a way that it will not come off accidentally during installation, various other methods can be used in addition to the embodiment shown in Fig. 3. Any mounting method is possible.

In the configuration shown in FIG. 2, necessary molding materials 11a such as resin pellets, fillers, reinforcing agents, colorants, etc. are supplied from the hopper 10 into the cylinder 12 which is heated to a predetermined temperature by the heating device 16, and the molding material 11a is placed in a fixed position. When the molding material 11a is forced forward by the screw 13 rotating at the screw 13, the pressure is increased as it advances to the tip of the screw 13, and the molding material 11a is kneaded by the rotation.
The molten material 11b is melted and plasticized by heating action.
and enters into the injection hole 15 of the plunger 14.

Here, when the rotation of the screw 13 is stopped, the mold 17 is set on the tip of the plunger 14, and the base 19 is advanced by the cylinder mechanism 20, the plunger 14 is pushed into the cylinder 12 side, and the melt is melted. The material 11b is placed in the mold 1 under suitable pressure.
It is injected into the cavity within 7. After the cavity is filled with the molten material 11b and cooled and solidified,
When the screw 13 is rotated again, the molten material 11
b is sent to the tip of the screw 13 and accumulated, and the cylinder 12 moves backward together with the base 19 due to the reaction force.

Therefore, if this retraction amount is set to a predetermined value using a control means such as a limit switch, the screw 1
By stopping the rotation of No. 3, the next injection amount can be quantified. The amount of one injection of the molten material 11b is determined by the diameter of the injection hole 15 of the plunger 14 and the forward stroke of the cylinder 12, so by changing these minutely, the injection amount can be finely adjusted. It is.

As explained above, according to the screw type injection device according to the present invention, the advantages of the conventional inline screw type injection device, such as excellent injection speed and injection pressure, are ensured, and the reciprocating movement of the screw with respect to the cylinder is not required. The injection amount can be determined with extreme precision using the plunger. In addition, the spool and runner inside the mold can be made smaller, which improves the yield of molten material and shortens the cooling time inside the mold, making it ideal for molded products that require particularly high precision and minute molded products. It is particularly advantageous for products with In particular, in the case of the present invention, the two cylinder mechanisms for injection and shift that were conventionally required are replaced by a single cylinder mechanism 20.
The overall structure is simplified because it can be shared with
The overall device can be made significantly smaller and lighter than conventional devices, with significant benefits such as significantly lower manufacturing and operating costs.

Moreover, by removing the plunger portion and making it easy to replace it, it is possible to freely and easily change the plunger diameter, injection amount, color of molded resin, etc. Further, even if the molten resin material leaks from the gap between the plunger and the nozzle portion, the operation of the plunger will not be hindered, and the leaked material can be easily removed.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing a conventional screw type injection device, Fig. 2 and the following shows an embodiment of the screw type injection device according to the present invention, Fig. 2 is a sectional view thereof, and Fig. 3 is an example of mounting a plunger. FIG. 10 is a hopper, 11a is a molding material, 11b
is a molten material, 12 is a cylinder, 13 is a screw,
14 is a plunger, 15 is an injection hole, 18 is a driving electric motor, 19 is a base, 20 is a cylinder mechanism, 24
is the mounting tube.

Claims (1)

[Scope of Claims] 1. An injection device comprising a cylinder that heats and melts a molding material, and a screw that rotates at a fixed position within the cylinder and pumps the molding material to a nozzle side of the cylinder, the injection device comprising: A plunger having an injection hole in the axial direction between the nozzle part and the mold is slidably fitted into the cylinder, and a drive mechanism for driving the plunger in the axial direction is connected to an electric motor for driving the cylinder and the screw. A screw-type injection device characterized by being connected to a fixed base. 2. The screw type injection device according to claim 1, wherein the plunger is fitted into a mounting tube that is threaded onto the nozzle portion of the cylinder.