JP2002219728A - Injection molding machine for foam molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an injection molding machine for foam molding which enables appropriate injection of gas, while preventing inflow of a resin into a gas supply device. SOLUTION: In the injection molding machine 10 for foam molding, a resin material is melted by a screw 16 provided in a heating barrel 14, while inactive gas is injected into the molten resin through a check valve 46, and the resin is then injected into a mold 12 to be subjected to foam molding. Herein the gas supply device has a gas injection hole 57 of which one end is opened in the inner peripheral surface of the barrel 14 and the other opened in first gas passages 52 and 54 holding the fore end side of the valve main body of a needle valve 50 movably, while it has a second gas passage 48 supplying the inactive gas from a gas supply source 20 to the first gas passages through the check valve 46 and a driving means 58 for the main body of the needle valve 50 which closes or opens the communication of the gas injection hole 57 with the first gas passages 52 and 54 by pressing by the fore end part thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection molding machine for injecting an inert gas such as carbon dioxide or nitrogen gas as a foaming agent into a heating barrel in an injection molding machine.

[0002]

2. Description of the Related Art Conventionally, an inert gas such as carbon dioxide gas or nitrogen gas is injected and mixed into a molten resin material in order to reduce the weight, heat insulation, sound absorption effect, and rigidity of a synthetic resin molded product. Is molded by injecting into a mold, and countless fine bubbles are formed in the molded resin.

FIG. 3 shows an example of a conventional injection molding machine for performing this type of foam molding. Here, reference numeral 10 is an injection molding machine for foam molding, and reference numeral 12 is a mold. The injection molding machine 10 includes a heating barrel 14, a screw 16 disposed in the heating barrel 14, a hopper 18 for supplying a resin raw material such as resin pellets melted in the heating barrel 14, And a gas supply source 20 for supplying carbon dioxide gas to the fuel cell.

[0004] The heating barrel 14 is configured to be heated by a heating device (not shown) provided on the outer periphery thereof.
0 is connected. The introduction path 22 is provided with a flow control valve 24, which controls the amount of carbon dioxide gas injected through the introduction path 22.

[0005] According to the injection molding machine 10 for foam molding having the above-described configuration, the resin material supplied from the hopper 18 is melted by the screw 16, and the molten resin mixed with the carbon dioxide supplied from the introduction path 22 is further mixed. , Heating barrel 1
4 is injected into the mold 12 from a nozzle 26 formed at the tip.

In the injection molding machine for foam molding formed as described above, a check valve 28 is provided to prevent the molten resin from flowing from the inside of the heating barrel 14 to the introduction path 22 side. The stop valve 28 is structured such that resin pressure is always applied during injection and metering. As a result, more resin easily flows into the introduction path 22, and seizure and clogging of the resin retained here, and further,
There is a risk that the molten resin leaks to the gas supply source side.

[0007]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an injection molding machine for foam molding capable of appropriately injecting gas while suppressing the inflow of resin into a gas supply device. It is to be.

[0008]

According to the present invention, in order to solve the above-mentioned problems, an injection molding machine for foam molding comprises a screw disposed in a heating barrel so as to be able to advance and retreat and rotate around an axis. In addition to melting the resin material, foam molding is performed by injecting an inert gas such as carbon dioxide gas as a foaming agent through a check valve into the molten resin and then injecting it into a mold to perform foam molding. In the injection molding machine, one end is opened on the inner peripheral surface of the heating barrel, and the other end is provided in the first gas passage having an inner diameter larger than the outer diameter of the valve body so as to movably accommodate the distal end side of the valve body of the needle valve. A second gas passage having a gas injection hole composed of an open pore, and having a second gas passage communicating with the first gas passage to supply the inert gas from a gas supply source via a check valve; The needle valve body is connected to the first gas Those having a gas supply apparatus having a driving means of the press closing or opening allowed to the needle valve body by the valve body tip the communication between the gas injection hole and the first gas passage moved in the road.

In the injection molding machine for foam molding according to the present invention, an electromagnetic valve is interposed between a gas supply source and a check valve, and the electromagnetic valve is used to previously connect the first and second gas passages when the screw rotates. After gas pressure is applied, the needle valve may be opened to perform gas injection.

The driving means is a pneumatic cylinder device, and the rear end of the needle valve is connected to the pneumatic cylinder device so that the needle valve can be driven forward and backward.

[0011]

Next, an embodiment of an injection molding machine for foam molding according to the present invention will be described with reference to FIGS.

FIG. 1 schematically shows an injection molding machine for foam molding according to the present invention. 1 except for a gas supply device main body (hereinafter referred to as a main body) 40 and a solenoid valve 42 fixedly attached to the outer peripheral portion of the heating barrel 14.
It has the same configuration as the conventional device shown in FIG. In FIG. 1, reference numeral 30 denotes a screw rotation motor, 32 denotes an injection cylinder, 34 denotes a pinion, and 36 denotes a rotary encoder for detecting a screw position. FIG. 2 is an enlarged view of the structure of the main body 40 shown in FIG. 1 and 2, the same components as those of the conventional device shown in FIG. 3 are denoted by the same reference numerals, and the detailed description thereof will be omitted.

FIG. 2 shows a cross section of the heating barrel 14 to which the gas supply device is attached, which is cut in a direction perpendicular to the screw 16. The main body 40 is provided with a gas supply port 44 connected to a carbon dioxide gas supply source 20 composed of, for example, a cylinder-type storage tank via a solenoid valve 42 for opening and closing. Source 20
A gas flow path (second gas passage) 48 is formed via a check valve 46 for preventing backflow to the side. This gas channel 4
8 is perpendicularly connected to a first guide hole (a part of the first gas passage) 52 in which the needle valve 50 is accommodated. The first guide hole 52 extends to a portion where the main body 40 is attached to the heating barrel 14, and the heating barrel 14 is provided with a second guide hole (the remaining portion of the first gas passage) at a position matching the first guide hole 52. ) 54 are formed. These guide holes 52 and 54 are formed to have an inside diameter that is somewhat larger than the diameter of the needle valve 50, so that a hollow portion is formed around the needle valve 50 therein. Further, a gas injection hole 57 having an inner diameter smaller than the diameter of the needle valve 50 is formed at the distal end of the second guide hole 54, and the distal end of the needle valve 50 is configured to abut this gas injection hole 57. Have been.

In front of the front end of the needle valve 50, there is formed a guide portion 55 composed of a plurality of projections whose outer diameter substantially corresponds to the inner diameter of the first and second guide holes 52 and 54. 55 acts to guide the distal end side of the needle valve 50. Behind the gas flow path 48 of the needle valve 50,
For example, a seal portion 59 made of a labyrinth seal is formed. Further, a resin discharge passage 56 for discharging a resin leak when the resin leaks is formed in the rear main body wall portion so as to be perpendicular to a hole into which the rear end side of the needle valve 50 is fitted. . The rear end of the needle valve 50 is connected to a piston 60 of a pneumatic cylinder 58 for driving the needle valve 50 forward and backward. Further, at the rear end of the needle valve 50, the main body 4
A rod 62 that penetrates through 0 and extends to the outside is provided, and the opening and closing of the needle valve 50 is detected by a proximity switch (not shown) and used for an injection start signal and a gas injection start signal.

In the gas supply device thus constructed, when the screw 16 is rotated to start the measuring process, air pressure is applied to the pneumatic cylinder 58 to press the piston 60, thereby closing the needle valve 50. State.
Thus, at the start of the measurement, the resin pressure in the heating barrel 14 is reliably shut off by the needle valve 50 and does not act on the check valve 46, and at the same time, the molten resin in the heating barrel 14 flows into the gas injection hole 57. However, it does not flow deeper than the needle valve 50.

The position of the screw 16 is detected by the rotary encoder 36. When the screw 16 is retracted by the progress of the measuring process and reaches a preset gas injection position, the piston 60 of the pneumatic cylinder 58 is retracted. ,
The needle valve 50 is opened. At this time, the electromagnetic valve 42 is opened in advance, and carbon dioxide gas is supplied from the gas supply source 20 to the first and second guide holes 52 and 54, that is, the hollow portion around the needle valve 50 via the check valve 46 and the gas flow path 48. It is preferable to introduce and apply pressure.

In this way, when the needle valve 50 is opened, the carbon dioxide gas given the pressure in the first and second guide holes 52 and 54 is immediately injected from the gas injection hole 57 into the heating barrel 14. Is done. Thereby, the needle valve 50
At the time of opening, the molten resin in the heating barrel 14 can be prevented from flowing into the gas injection hole 57 and the first and second guide holes 52 and 54, and the molten resin flows into the gas injection hole 57. When I was doing this
4 can be discharged.

The carbon dioxide gas injected into the heating barrel 14 from the gas injection hole 57 is mixed with the molten resin in the heating barrel 14 by the rotation of the screw 16.

Thereafter, even if the pressure in the heating barrel 14 rises abnormally while the needle valve 50 is open and exceeds the gas pressure from the gas supply source 20, the check valve 46 is closed and the gas injection hole is closed. The backflow of carbon dioxide from the gas supply source 20 to the gas supply source 20 is prevented, and the molten resin in the heating barrel 14 is prevented from flowing into the gas injection hole 57.

The operation of injecting the carbon dioxide gas is terminated by controlling the screw position at the time of metering or by controlling the time, and the needle valve 50 is closed again.

At the time of injection of the injection molding machine, the pneumatic cylinder 5
Air pressure is applied to 8 to keep the needle valve 50 closed. Accordingly, the resin pressure at the time of injection does not act on the check valve 46, and at the same time, the molten resin in the heating barrel 14 does not flow into the first and second guide holes 52, 54.

In the above-described embodiment, the second guide hole 54
Although the example in which the gas injection hole 57 is provided in the heating barrel 14 has been described, the present invention is not limited thereto, and the main body 40 may be provided in the heating barrel 14.
Various modifications are possible, for example, the second guide hole 54 and the gas injection hole 57 may be provided in the main body 40 by projecting so as to match the inner peripheral surface of the main body 40.

[0023]

According to the injection molding machine for foam molding according to the present invention, the needle valve is closed at the time of injection, so that the high-pressure resin pressure in the heating barrel does not act on the check valve, and at the same time, the melting is performed. The resin can be more reliably prevented from flowing into the gas supply device. Also, at the time of gas injection, if the needle valve is opened after introducing the gas into the guide hole and applying the gas pressure in advance, it is possible to more reliably prevent the resin from flowing into the gas supply device side and to prevent the resin from flowing. An injection can be made. Therefore, it is possible to effectively prevent the resin from accumulating in the gas injection hole and seizing, the gas injection hole from being clogged, and the resin from deeply entering the gas supply source side due to a malfunction of the check valve.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an injection molding machine for foam molding according to the present invention.

FIG. 2 is an enlarged cross-sectional view illustrating a configuration of a gas supply unit of FIG. 1;

FIG. 3 is a schematic configuration diagram showing an example of an injection molding machine for performing conventional foam molding.

[Explanation of symbols]

 Reference Signs List 10 injection molding machine for foam molding 12 mold 14 heating barrel 16 screw 18 hopper 20 gas supply source 22 introduction path 24 flow control valve 26 nozzle 28 check valve 30 screw rotation motor 32 injection cylinder 34 pinion 36 rotary encoder 40 gas supply Apparatus main body 42 Solenoid valve 44 Gas supply port 46 Check valve 48 Gas flow path (second gas passage) 50 Needle valve 52 First guide hole (part of first gas passage) 54 Second guide hole (First) 55 Guide part 57 Gas injection hole 58 Pneumatic cylinder 59 Seal part 60 Piston 62 Rod

Claims (3)

[Claims] 1. A resin material is melted by a screw disposed in a heating barrel so as to be capable of moving forward and backward and rotatable around an axis, and the molten resin is inerted by a non-return valve through a check valve. In a foam molding injection molding machine in which a gas is injected as a foaming agent and then injected into a mold to perform foam molding, one end is opened on the inner peripheral surface of the heating barrel, and the other end is a valve body of a needle valve. A first gas passage having an inner diameter larger than the outer diameter of the valve body so as to movably accommodate the distal end side of the first gas passage; and a first gas passage from a gas supply source via a check valve. A second gas passage communicating with the inert gas to supply the inert gas to the gas passage, and moving the needle valve main body in the first gas passage so that the gas injection hole and the first gas passage are connected to each other. Communication at the end of the valve body An injection molding machine for foam molding, comprising: a gas supply device having a drive means for a needle valve body for further pressing and closing or opening. 2. A solenoid valve is interposed between a gas supply source and a check valve, and the needle valve is opened after applying gas pressure to the first and second gas passages at the time of screw rotation by the solenoid valve. The injection molding machine for foam molding according to claim 1, wherein the injection is performed by gas injection. 3. The foaming molding according to claim 1, wherein the driving means is a pneumatic cylinder device, and the rear end of the needle valve is connected to the pneumatic cylinder device so as to be driven forward and backward. Injection molding machine.