JPS6184221A - Injection molding device - Google Patents

Abstract

PURPOSE:To contrive to prevent the abrasion wear of a screw and the unevenness of a product by keeping molten plasticized resin in the chamber formed by the relative movement of the screw and a plunger. CONSTITUTION:A screw 12 is retracted by the pressure of molten and plasticized resin, and a resin path 16 is formed in between the tip of the screw 12 and a heating cylinder 10. When the resin path 16 is formed, the resin pressure is applied onto the tip surface of a plunger 17. Therefore, the plunger 17 is independently retracted relative to the screw 12, and molten and plasticized resin is kept in the chamber (C) formed by their relative movement. When the specified amount of resin is kept in the chamber (C), the screw 12 is advanced, and the resin path 16 is closed. Then the plunger 17 is advanced and resin is infected. Consequently, because there is no necessity for retracting the screw in proportion to the increase of resin amount, the abrasion wear of the screw may be suppressed, and also the unevenness in the molten and plasticized state of the resin is elminated.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention This invention relates to an injection molding apparatus with a set of in-line screws for molding resin molded products.

Conventional technology A set of inline screws (also simply called a set of screws)
Plasticizing equipment in injection molding equipment (including injection equipment)
generally has a structure as shown in H43a (
For example, ``Machine Stock Engineering Handbook, Revised 6th Edition, 9 Volumes 18'' (1973)
2.3.18) 9 Japan Society of Mechanical Engineers, P33-34).

That is, as shown in Fig. 4, the pellet-shaped resin raw material stored in the hopper 1 is sent forward in the heating cylinder 3 by the rotation of the screw 2, and is absorbed by the heat of the protectors 4 and 4 due to the rotation of the screw. It is melted and plasticized by heat insulation. The screw 2 moves relatively backward due to the reaction force of the resin sent forward by the screw 2, while the melted and plasticized resin flows into the space R defined by the heating cylinder 3 and the screw 2. It can be stored. The resin in the space R is then injected into the mold M from the nozzle 5 by moving the screw 2 forward by the action of an injection cylinder (not shown). In addition, check the ring shape for backflow of molten and plasticized resin.

This is prevented by valve 6.

Problems to be Solved by the Invention In the injection molding apparatus as described above, since the screw 2 moves relatively as the amount of resin stored in the space R increases, the heater 4 , 4... causes a large deviation in the relative positional relationship C between the heating zone and the screw 2, and furthermore, the effective length of the screw 2 and eventually L/D (length/diameter) also gradually change.

For this reason, as mentioned above, the melting and plasticizing state of the resin becomes uneven due to the heating by the heater and the shear heat of the screw.
Particularly in the case of resins containing reinforcing materials such as glass fibers, the properties after completion of molding may be affected.

In addition, in the case of resin containing reinforcing material as described above, it tends to accumulate near the check valve 6 for backflow prevention, and the reinforcing material may break, making it impossible to fully demonstrate its original function as a reinforcing material. Sometimes there isn't.

Means for Solving the Problems The present invention aims to provide an injection molding apparatus that solves the above-mentioned problems. A plunger movable in the axial direction is inserted into the screw, and the space formed by relative movement between the screw and the plunger is used as a chamber portion for storing molten and plasticized resin.

Function According to the present invention, the chamber portion created by the relative movement between the hollow screw and the plunger has the function of storing molten and plasticized resin, thereby eliminating the need for relative movement between the heating cylinder and the screw. Moreover, since the screw itself has a backflow prevention function, the above-mentioned problems can be solved at once.

Embodiment FIG. 1 is a sectional view showing an embodiment of the present invention, showing a state in which a plasticizing device (including an injection device) emits photons.

10 is a heating cylinder equipped with a nozzle 1) at the tip, 1 is a hopper, 4.4... is a heating cylinder 10 and nozzle 1
) is a heater attached to the outer periphery of the

A hollow screw 12 is rotatably and slidably inserted into the heating cylinder 10 . This screw 1
A flange portion 13 is integrally provided at the rear end of 2,
The flange portion 13 rotatably engages with a back plate 14, and the back plate 14 is connected to a piston rod 15a of a hydraulic cylinder 15. Therefore, due to the action of the hydraulic cylinder 15, the screw 1
2, a resin passage 16 with a minute interval is formed between the screw 12 and the heating cylinder IO, as shown in FIG.

A plunger 17 is inserted into the screw 12 so as to be slidable in the axial direction, and this plunger 17 is directly connected to a motor 18 which is a rotational drive source.

Further, a support plate 19 supporting the motor 18 is connected to a piston rod 20a of an injection cylinder 20. In other words, the internal spline 2 formed on the screw 12
1, an outer spline 23 formed on the large diameter portion 22 of the plunger 17 is slidably coupled to the plunger 17 by a sliding spline. Therefore, the plunger 17 and the screw 12 are rotated together by the action of the motor 18, while the plunger 17 can independently slide with respect to the screw 12 by the action of the injection cylinder 20.

A series of operations of the device configured as above will be explained as follows.

Since FIG. 1 shows a state in which injection has been completed, a transition will be made from this state to the next plasticizing operation.

First, the hydraulic pressure acting on the hydraulic cylinder 15 to move the screw 12 forward is released, and then the motor 18 is started. As a result, plunger 17 and screw 12
are rotated together due to the spline connection, and the resin raw material in the hopper 1 is sent out and is sent forward in the heating cylinder 10 while being melted and plasticized. Then, as the molten and plasticized resin is sent out, the screw 12 is relatively retreated due to the resin pressure, and the resin is placed between the tip of the screw 12 and the heating cylinder 10 as shown in FIG. A passage 16 is formed. At this time, the stepped portion 24 of the inner circumferential surface of the screw 12 is connected to the stepped portion 2 of the plunger 170.
5, the plunger 17 also moves back by a minute amount together with the screw 12.

When the resin passage 16 is formed, the pressure of the molten and plasticized resin acts on the tip surface of the plunger 17, so the plunger 17 retreats independently with respect to the screw 12, causing relative movement between the plunger 17 and the screw 12. The molten and plasticized resin is stored in the chamber O created by this process. At this time, the retraction speed of the plunger 17 is controlled by the back pressure of the injection cylinder 20, and the plunger 17 prevents the resin from flowing back.

When a predetermined amount of resin is stored in the 1,000-Yanba part O in this way, the screw 12 is moved by the action of the hydraulic cylinder 15.
moves forward and closes the resin passage 16 as shown in FIG.

Then, the plunger 17 moves forward due to the action of the injection cylinder 20, whereby the resin stored in the chamber portion 0 is injected.

Effects of the Invention As described above, according to the present invention, there is no need to retract the screw as the amount of melted and plasticized resin increases, so wear of the screw can be suppressed, and the heating zone by the heater and the screw The relative positional relationship between the screws and the effective length of the screw do not change significantly, and the state of melting and ψ-ization of the resin does not become uneven.

In addition, since the plunger itself has a function to prevent resin from flowing backwards, there is no need to provide a check valve, which was previously required, and it is possible to prevent resin from stagnation. Even if the reinforcing material is included, the reinforcing material will not be broken.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention, FIGS. 2 and 3 are sectional views for explaining the operation of FIG. 1, and FIG. 4 is a sectional view showing the basic structure of a conventional device. It is. DESCRIPTION OF SYMBOLS 1... Hopper, 4... Heater, 10... Heating cylinder, 12... Screw, 15... Hydraulic cylinder, 16... Resin passage, 17... Plunger, 18
...Motor%20...Injection 7 cylinder, 21.23...
·spline.

Claims (1)

[Claims] (1) In an injection molding device equipped with a screw-type plasticizing device in which a screw is contained within a heating cylinder, the screw is formed into a hollow shape and is movable in the axial direction relative to the screw. An injection molding device characterized in that a plunger is inserted, and a space formed by relative movement between the screw and the plunger is used as a chamber portion for storing molten and plasticized resin.