JP2628135B2 - Pre-plastic injection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pre-plastic injection device used for injection molding of a synthetic resin.

[0002]

2. Description of the Related Art In general, a plastic injection machine has a plasticizing cylinder inside a screw and a plasticizing cylinder inside a plunger, and the tip of the plasticizing cylinder has a large diameter and a short cylindrical body. , And a resin melted and kneaded by a plasticizing cylinder (hereinafter referred to as a molten resin) is injected into a front portion of an injection cylinder by using a cylinder or the like as a resin path, and then injected by a plunger. .

The reason why the resin path is constituted by a large-diameter, short cylinder or the like is to reduce the flow resistance of the molten resin sent from the plasticizing cylinder in the resin path and to inject the molten resin into the injection cylinder as soon as possible. .

[0004]

In such a pre-plastic injection device, since the resin is plasticized by a screw rotating at a fixed position, an in-line screw injection device in which the plasticizing is performed by a screw that retreats while rotating. It is said that the plasticization can be performed more uniformly than the device, but the plasticization is not necessarily performed uniformly, and the temperature difference between the heating members (band heaters) individually attached to the outer circumference of the plasticizing cylinder If it is present, temperature unevenness tends to occur, and the temperature unevenness often causes non-uniform plasticization. In particular, since the resin has poor thermal conductivity, the resin is injected into the injection cylinder as it is without the temperature unevenness being improved in the flow process and the plasticized state being not uniform.

The present invention has been conceived in order to solve the problem in the pre-plastic injection apparatus, and has an object to make the temperature of the resin plasticized by the screw uniform in the resin path and to reduce the influence of uneven temperature. It is an object of the present invention to provide a prepra-type injection device having a new configuration capable of minimizing the size as much as possible.

[0006]

A feature of the present invention according to the above object is that a plasticizing cylinder inside a screw is arranged in parallel with an injection cylinder inside a plunger, and resin melted by the plasticizing cylinder is injected into the front of the injection cylinder. In a pre-plastic injection apparatus in which injection is performed by a plunger, the diameter of a resin path connecting the injection cylinder and the plasticizing cylinder is set to 5 mm.
The length is set to be at least five times the diameter, and the flow resistance is generated in the resin path.

Another feature is that a temperature control means for the molten resin is provided around the outside of the resin path.

[0008]

[Operation] In the above configuration, the flow resistance is easily generated in the resin path due to the limitation and the length of the cross-sectional area of the resin path, and the molten resin flowing in the resin path is caused to flow into the injection cylinder by the flow resistance. During that time, the temperature is leveled and the plasticized state becomes uniform.

In the case where a temperature control means is provided around the outer periphery of the resin path, the temperature can be controlled up to the center of the molten resin by limiting the cross-sectional area of the resin path, whereby the temperature of the resin becomes more uniform. .

[0010]

1 shows an injection cylinder 1 in which an injection plunger 2 is provided so as to be able to advance and retreat, and an injection hydraulic cylinder 3 is provided at the rear end.
The plunger 2 is connected to the piston 4 of the injection hydraulic cylinder 3.

Reference numeral 5 denotes a plasticizing cylinder juxtaposed on the injection cylinder 1, which is provided with a plasticizing screw 6 rotatably at a fixed position, and has a hopper 7 at a supply port provided at the rear of the cylinder. Although not shown in the figure, a screw drive device such as an electric motor is connected to the rear end of the cylinder.

Reference numeral 8 denotes a resin path, which has a diameter of 5 to 10 mm and a length of at least 5 times, preferably 20 to 40 times the diameter. In this embodiment, the diameter is 8 mm and the length is 25
The resin path 8 is formed by a steel pipe 9 having a required thickness of 0 mm (about 31 times). The resin passage 8 is provided between the rear part of the nozzle 10 at the tip of the injection cylinder and the nozzle member 11 at the tip of the plasticizing cylinder, and is provided with the pipe body. A check valve 12 is provided to cause the spring member 13 to act in the valve closing direction.

Reference numeral 14 denotes a temperature control means comprising a composite of a refrigerant jacket 15 attached to the outer periphery of the tube 9 and a band heater 15 on the outer periphery of the jacket, and cools the molten resin flowing through the resin path 8 by cooling. Improve temperature unevenness.

In the embodiment shown in FIG. 2, a band heater 17 for reheating is provided in the resin path 8 between the temperature control means 14 and the injection cylinder 1. The passage 8 is formed longer than the case shown in FIG. 1, and a band heater 17 is attached to the outer periphery of the joint pipe 9, and the check valve 12 is provided at the joint of the resin passage ahead of the temperature control means 14. I have. In such a structure, the molten resin can be secondarily heated, so that the temperature control effect is improved as compared with the case of only cooling.

In each of the above embodiments, a band heater 18 is mounted around the injection cylinder 1, the plasticizing cylinder 5 and the nozzle 10, and the band heater 18 plasticizes the resin and maintains the resin temperature. Done.
However, plasticization of the resin is performed by setting the cylinder temperature higher than a normally set temperature. Therefore, even if there is a low-temperature portion in the molten resin, the low-temperature portion is at least higher than the resin temperature at the time of normal injection.

In addition, the temperature of the molten resin is previously set to a temperature equal to or lower than the plasticization temperature in the temperature control means so that the temperature of the molten resin becomes a desired temperature at the time of injection. The setting of the temperature is performed by using the refrigerant jacket 15 and the band heater 16 selectively.

The resin of the pellets supplied from the hopper 7 to the plasticizing cylinder 5 is melted and kneaded by the rotation of the screw 6 and the heating from the plasticizing cylinder 5, and the molten resin is supplied from the nozzle member 11 at the tip as a molten resin. Flow into Road 8.

The molten resin flowing into the resin path 8 has a diameter of 8 mm.
flow resistance due to the passage restricted to
The temperature unevenness is improved while flowing. The mixture is cooled to the center by a coolant jacket 15 or a band heater 16 set at a temperature lower than the plasticization temperature, adjusted to a temperature suitable for injection molding, and then injected into the injection cylinder 1.

The plasticizing temperature of the resin, the set temperature of the temperature control means, and the temperature of the molten resin at the time of injection are shown below. Type of resin Plasticization temperature (° C) Set temperature (° C) Injection temperature (° C) PMMA 260 240 245.7 ABS 240 230 235.6 PA6-6 280 265 272.4 PPS 330 315 318.2

FIGS. 3A and 3B show the relationship between the resin temperature and time in the case of the conventional screw prepeller injection apparatus and in the case of the present invention, wherein A is the embodiment shown in FIG. 1, B is the embodiment shown in FIG. C is a conventional device, and accumulation means a state in which it is injected into an injection cylinder. As is clear from this figure, A,
In B, the accumulated temperature of the molten resin does not fluctuate even after the lapse of time, but in C, vertical fluctuation is observed. It is recognized that this temperature fluctuation is caused by non-uniform temperature of the molten resin.

If the diameter of the resin passage 8 is 5 mm or less, the flow resistance increases and it takes too much time to measure. On the other hand, if the diameter is 10 mm or more, the flow resistance decreases and the flow becomes easy. It did not improve.

[0022]

As described above, according to the present invention, since the resin passage connecting the injection cylinder and the plasticizing cylinder is configured to generate flow resistance, the molten resin sent out from the plasticizing cylinder has uneven temperature. However, the temperature unevenness is improved during the passage through the melting passage, and the plasticized state becomes uniform.

When the temperature control means for the molten resin is provided in the resin path, the temperature of the entire molten resin can be adjusted to a temperature suitable for injection in addition to the improvement of the temperature unevenness due to the flow resistance. Injection molding with good thermal management of the molten resin can be performed.

Since the distortion of the molded product is eliminated by the improvement of the temperature unevenness and the thermal management of the molten resin, the non-defective product can be used for molding optical products such as thick lenses and prisms or precision products requiring dimensional accuracy. Obtainable.

[Brief description of the drawings]

FIG. 1 is a schematic vertical sectional side view of a first embodiment of a pre-plastic injection apparatus according to the present invention.

FIG. 2 is a schematic vertical sectional side view of the second embodiment.

FIG. 3 is a comparison diagram of a molten resin temperature accumulated in an injection cylinder between a case according to the present invention and a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Injection cylinder 2 Plunger 5 Plasticizing cylinder 6 Screw 8 Resin path 9 Pipe 10 Nozzle 11 Nozzle member 12 Check valve 14 Temperature control means 15 Refrigerant jacket 16 Band heater 17 Band heater 18 Bant heater

Claims (2)

(57) [Claims] A plastic injection cylinder in which a plasticizing cylinder inside a screw is juxtaposed to an injection cylinder inside a plunger, and a resin melted in the plasticizing cylinder is injected into a front portion of the injection cylinder to perform injection by a plunger. The diameter of the resin passage connecting the injection cylinder and the plasticizing cylinder is limited to 5 to 10 mm, and the length is set to at least five times the diameter, so that flow resistance is generated in the resin passage. Pre-plastic injection device. 2. A pre-plastic injection apparatus according to claim 1, wherein said resin path is provided with a means for controlling the temperature of the molten resin on the outer periphery.