JPS5981144A - Preplunger type injection molding machine - Google Patents

Abstract

PURPOSE:To minimize any resin leakage from a gap between an injection plunger and a plunger barrel by providing a check ring on the injection plunger and a hole for drawing a melted resin from an extruder on the base side of the injection plunger. CONSTITUTION:Material in a hopper 6 is conveyed to be plasticized with an extrusion screw 8 driven with a motor 5, fed to the base f a plunger barrel 1 passing through a stop valve 9 from the tip of a screw barrel 7 to be accumulated in a space C passing through a check ring 10 via a space D. Then, the retraction of an injection plunger 11 is detected and stops the motor 5 to complete the plasticization. Then, a high pressure oil is fed to a space A of a cylinder 3 to advance the injection plunger 11 while closing the stop valve 9 and a resin in a space C is compressed to be injected into a die from a nozzle 4. Here, with a rise in the pressure of the resin in the space C, the check ring moves to the right to prevent the pressure propagation to the space D thereby minimizing the leakage of the resin from a gap G.

Description

DETAILED DESCRIPTION OF THE INVENTION In a conventional pre-plastic injection molding machine, as shown in FIG.
The amount of F91 is accumulated in the injection plunger (2)
Through the nozzle (4) at the tip of the injection cylinder (3),
This is a structure that is injected into a mold. In the figure, (5) is the motor, (6) is the hopper, (7) is the extrusion screw barrel,
(8) is an extrusion screw, (9) is a stop valve (check valve)
It is.

Next, the operation will be explained with reference to FIG. First, to explain plasticization, the raw material in the hopper (6) is
) is plasticized and conveyed by a screw (8) driven by a screw (8). The plasticized resin from the tip of the extrusion screw barrel (force) passes through the stop valve (9) and is fed into the plunger barrel (1).

The plunger (2) continues to retreat due to the pressure of the resin sent into the space C, and when the amount of retreat reaches a predetermined value, the motor (5)
) stops rotating to complete plasticization.

Next, injection will be explained. When high pressure oil is sent to the space A of the injection cylinder (3), the plunger (2) moves forward. At this time, the stop valve (9) is closed, so the space C
The resin is injected into the mold through the nozzle (4).

In addition, plunger barrel (1) and injection plunger (2)
are in a fitted state with a slight gap G, so the high-pressure resin in the space C passes through the gap G and flows out into the space B (albeit slightly).

However, the molding machine shown in FIG. 1 had the following drawbacks. That is, during injection, the resin leaks from the small gap G between the injection plunger (2) and the plunger barrel (1) as described above. Then, the leaked resin accumulates in space B, or the temperature in this part is lower than the resin temperature, and the resin cools and solidifies. When the amount of cooled and solidified resin increases, the injection plunger (2) f! /I will be able to prevent damage.

In addition, in order to reduce resin leakage, the injection plunger (
It is better to reduce the gap G between the plunger barrel (1) and the plunger barrel (2), but if it is too small, the plunger (
2) and the barrel (1) were likely to seize, and it was difficult to determine the optimal gap.

Since the gap between the injection plunger and the plunger barrel cannot be eliminated structurally, the present invention prevents the resin in the space C from becoming high pressure even during injection, and minimizes resin leakage from the gap. This is what I am trying to do.

That is, in the present invention, a check ring is provided on the injection plunger, and an intake hole for the molten resin from the extruder is provided on the base side of the injection plunger, and the high pressure resin generated during injection is sealed with the check ring, and the injection plunger and plunger barrel are sealed. It is an object of the present invention to provide a pre-plastic injection molding machine in which the amount of resin leaking from the gap between the parts is minimized.

An embodiment of the present invention will be explained below with reference to the drawings. Fig. 2 shows an embodiment of the present invention, which includes a screw extruder device for plasticizing resin, and a fixed amount of plasticized resin stored in a mold at high pressure. It consists of an injection device that performs injection. In Figure 2, (1) is the plunger barrel, (3) is the injection cylinder, (4) is the nozzle, (5) is the motor, (6) is the hopper, (force is the extrusion screw barrel, and (8) is the extrusion The screw, (9) is the stop valve, and since these are the same as in Fig. 1, detailed explanation will be omitted and only the differences from Fig. 1 will be explained. 00) is the check ring, and the injection plunger (
It is provided on the outer periphery of flJ, and is pressed against the tip side (left side) of the injection plunger (11) by the flow pressure of the resin during the plasticizing operation, thereby making the passage to the space C free through the space.

However, during injection operation, the injection plunger (
l]) is pressed against the base side (right side) as shown in the drawing, and the passage between the space and the space C- becomes blocked.

That is, the check ring (10) is fitted into the plunger barrel (1) with an extremely small gap, and its movement is regulated by the movable stroke S provided on the injection plunger Ql).

Now, the molten resin supplied from the extrusion screw barrel (7) enters the space through the openings (1) at the base (right end) of the plunger barrel (1), and enters the check ring (10).
A passage is formed through which the resin flows smoothly into space C without stagnation or stagnation.

Next, the operation of the embodiment shown in FIG. 2 will be explained.

First, to explain plasticization, the raw material in the hopper (6) is passed through an extrusion screw (8) driven by a motor (5).
) and is transported to the left front and plasticized. Then, the plasticized resin passes through the stop valve (9) from the tip of the extrusion screw barrel (7), is fed into the base of the plunger barrel (1), passes through a space, and then enters the check ring (■0).
is accumulated in space C. Further, the completion of plasticization is accomplished by Kokichi, who detects the amount of retreat of the injection plunger (IIJ) and stops the Morse (5).

Next, injection will be explained. When high pressure oil is sent to the space A of the injection cylinder (3), the injection plunger aυ moves forward. At this time, the stop valve (9) is closed, so the resin in the space C is compressed and injected into the mold through the nozzle (4). Furthermore, an increase in the resin pressure in the space C moves the check ring (10) to the right to prevent pressure from propagating to the space.

Since the present invention is configured as explained in detail above,
Since the resin in the space does not become under high pressure even during injection, resin leakage from the gap G between the injection plunger and plunger barrel is extremely small, and the frequency of cleaning and inspection of resin leaking into space B can be greatly reduced. Moreover, it is possible to reduce as much as possible the troubles caused by poor cleaning, and there are advantages such as less loss of resin.

Further, the resin that has entered the gap G between the injection plunger and the plunger barrel deteriorates and changes in quality over time, and this resin may flow back into the space C during plasticization. In the conventional method, there was a large amount of resin that entered the gap G, so the amount of backflow was large, but in the case of the present invention, this amount of backflow is almost eliminated.

[Brief explanation of the drawing]

FIG. 1 is a side sectional view showing an example of a conventional pre-plastic injection molding machine, and FIG. 2 is a side sectional view of a pre-plastic injection molding machine showing an embodiment of the present invention. Explanation of the main parts of the diagram■...Plunger barrel 8...Sealing cylinder small...Nozzle? ... Extrusion screw barrel 8 ... Extrusion screw IO ... Check ring 11 ... Injection plunger ■ 2 ... Port (intake hole) C, D ... Space G ... Gap patent Applicant Mitsubishi Heavy Industries Co., Ltd.

Claims (1)

[Claims] A check ring is provided on the injection plunger, and an intake hole for the molten resin from the extruder is provided on the base side of the injection plunger, and the high pressure resin generated during injection is sealed by the check ring and the gap between the injection plunger and the plunger barrel is This pre-plastic injection molding machine is characterized by minimizing the amount of resin leaking from the machine.