JP2514900B2 - Injection device equipped with inert gas supply means - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection device having an inert gas supply means for preventing oxidation of a molding material in a heating cylinder in injection molding of synthetic resin.

[0002]

2. Description of the Related Art When a synthetic resin is plasticized by an injection device and injected into a mold, the molded product may be discolored or black spots may occur. The discoloration and the black spots are due to the oxidative deterioration of the material, and it is considered that the molding material staying in the heating cylinder for a long time is oxidatively deteriorated by the oxygen in the air taken in together with the material.

The above black spots are likely to occur at the start of injection molding, and very rarely occur when injection molding is continuously performed. These rare black spots did not occur during molding, but those that adhered to the screw and the like due to oxidative deterioration due to long-term retention were only separated and mixed.

As this oxidation preventing means, it is necessary to supply an inert gas such as nitrogen into the heating cylinder.
No. 4, JP-A-3-216321 and the like. In these methods, a supply pipe is provided in a hopper, a material supply section at the rear of the heating cylinder is made an atmosphere of an inert gas, and a granular molding material is melted in the atmosphere.

[0005]

The conventional feeding method as described above is such that an inert gas is simply fed to the material feeding portion of an injection apparatus having a normal structure by utilizing a hopper, and therefore, the inert gas during molding is not used. Although it is possible to prevent oxidation by means of the above, some of the inert gas supplied into the heating cylinder easily leaks through the gap between the heating cylinder rear part and the screw shaft, the gap in the hopper mounting part, etc. It was difficult to prevent the resulting oxidation.

The oxidation that occurs when molding is restarted is caused by the fact that the molten molding material is not discharged into the heating cylinder but is left as it is. If the molten material remaining in the heating cylinder is left as it is after the completion of injection molding, the molten material solidifies around the screw by cooling and shrinks. Due to this shrinkage, a gap is generated between the heating cylinder and the solidified residual material, although the size varies depending on the type of molding material. Since this gap also communicates with the nozzle hole at the front end of the heating cylinder and the rear portion of the heating cylinder, air flows in from the outside due to the negative pressure associated with the formation of the gap and exists as an air layer between the heating cylinder and the residual material.

When the band heater around the heating cylinder is used for heating in such a state to start the molding, the air layer is heated, and the solidified residual material around the screw is heated and melted. The surface reacts with oxygen in the air to cause oxidative deterioration.

Therefore, if the air layer that causes oxidation is replaced with an inert gas layer and the residual material around the screw is heated, discoloration and black spots due to oxidation at the start of molding can be prevented. Since the gap generated by the contraction is limited, it is difficult to replace the inert gas supplied into the hopper with air as it is, and some means must be provided there.

It is an object of the present invention to hermetically seal a part without significantly improving the injection device and to change the way of supplying the inert gas so that the gap generated by cooling the molten material can be prevented. An object of the present invention is to provide an injection device that can supply active gas.

[0010]

SUMMARY OF THE INVENTION According to the present invention according to the above object, a packing for hermetically closing a gap with a rear part of a screw is fitted to an inner periphery of a rear part of a heating cylinder having a screw for injection therein, and the packing. An opening is provided in the upper part of the heating cylinder in the front side to form a material supply part, and the seat plate of the hopper is superposed on the upper part of the heating cylinder of the material supply part so that the central opening overlaps with the opening and is integrally fixed. , The inert gas supply hole in the rear wall of the molding material supply port formed by the polymerization of this opening, downward through the screw forward by the through hole obliquely provided from the upper part of the seat plate to the inner end of the seat plate opening. The inert gas supply pipe is connected to the socket on the seat panel provided at the outer end of the supply hole that is obliquely installed, and the above hopper sealed by the lid member is attached to the seat panel, and the hopper and the seat panel are installed. Heating cylinder and seat board around the connection part and supply port Contact portion formed by preventing the leakage of the inert gas supplied in airtight a, is that.

[0011]

[Operation] In the above configuration, the entire amount of the inert gas is supplied toward the front of the screw of the supply port, and the rear part of the heating cylinder and the material supply part are airtightly configured. If there is a gap between the heating cylinder and the residual material due to contraction due to cooling of the molten material, there will be no other escape area. Flows out of the opening. As a result, the gap is grooved by the inert gas, and the oxidation of the residual material at the time of heating and melting is prevented.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The illustrated example is for explaining an inert gas supply method in the case of using an in-line screw type injection device, and the heating cylinder front end is omitted.

In the figure, reference numeral 1 is a heating cylinder having a band heater 2 on its outer periphery, and has a screw 3 for injection therein. A packing 4 is fitted on the inner periphery of the rear portion of the heating cylinder 1, whereby the gap with the screw rear portion 3a is closed to make it airtight.

Reference numeral 5 denotes a seat plate of the hopper 6, which has an opening in the center, and the opening overlaps with the opening provided in the material supply section of the heating cylinder 1 and is integrally installed and fixed on the upper part of the heating cylinder 1. The molding material supply port 7 is formed by these openings.

On the rear wall of the supply port 7, a supply hole 8 for the inert gas (nitrogen gas N ₂ ) is provided obliquely downward toward the front of the screw. The supply hole 8 is formed by a through hole obliquely provided from the upper part of the seat 5 to the inner end of the seat opening.
An inert gas supply pipe 10 is connected to a receptacle 9 on the seat provided at the outer end of the supply hole 8.

The seat 5 is provided with the hopper 6 whose opening is closed by a lid member 11, and the lid member 11 has a vent member 12 for discharging excess inert gas.
Is provided.

The contact portion between the heating cylinder 1 and the seat 5 and the connecting portion between the seat 5 and the hopper 6 around the supply hole 7 are airtightly closed by seal rings 13, 14 and 15, and these seal rings are connected to each other. The packing 4 makes the material supply portion of the heating cylinder 1 airtight so that the supplied inert gas does not leak to the outside.

Reference numeral 16 denotes an inert gas supply device, which comprises a nitrogen gas generator 17 connected to the supply pipe 10, a pressure adjusting valve 18 arranged in the supply pipe 10, and a stop valve 19. Further, the supply pipe 10 is provided with a flow rate control valve 20 for controlling the supply amount of the inert gas in response to an electric command from the molding machine.

Although not shown in the figure, the amount of inert gas in the material supply section is measured by measuring the concentration in the hopper, and the flow rate control valve 20 is electrically operated according to the measured value to control the supply amount. I do. In the concentration measurement, the oxygen concentration may be measured and then the nitrogen concentration may be calculated and controlled. Further, depending on the case, the nitrogen gas generator may be a nitrogen cylinder.

In the above structure, the granular molding material flowing down from the hopper 6 to the supply port 7 is sent to the material melting portion in the heating cylinder as it is in a granular form by the rotation of the screw 3. At the same time, the inert gas is supplied while controlling the supply amount according to the molding state. The inert gas supplied to the supply hole 8 at a predetermined pressure through the supply pipe 10 is jetted obliquely downward to the front of the screw of the supply port 7 to fill all the small spaces generated between the molding materials. .

As a result, the air is diluted and invasion from the outside is blocked, so that the material melting portion becomes an atmosphere of an inert gas, and the molding material is melted while being prevented from being oxidized by oxygen in the air. Be seen. Then, the granular material becomes a molten state and is sent to the tip of the heating cylinder by the rotation of the screw 3.

When the heating by the band heater 2 is stopped after the molding is completed, the molten material remaining in the heating cylinder is cooled and solidified. If the above-mentioned supply of the inert gas is continued as it is, the inert gas flows into the gap b between the heating cylinder 1 and the residual material a caused by the contraction due to cooling, and prevents the invasion of air from the outside. , Prevents the oxidation of the molten material in the cooling process.

When an inert gas was supplied to the supply port 7 at a predetermined pressure before the injection molding was started, the inert gas was formed between the heating cylinder 1 and the residual material a from the material supply section. It flows into the gap b and flows out through the opening at the tip of the heating cylinder. As a result, the air in the gap b is pushed out of the opening,
The residual material a is heated and melted in an atmosphere of an inert gas, and oxidation by oxygen in the air is prevented. As a result, black spots do not occur even in a molded product at the start of molding.

Therefore, when the inert gas is continuously supplied regardless of the operation stop of the molding machine, the oxidative deterioration of the molding material can be completely prevented. Further, such an inert gas can be supplied by adopting a nitrogen generator that separates nitrogen from the air as a source of the inert gas.

[0025]

As described above, according to the present invention, the inert gas supply hole is provided in the rear wall of the molding material supply port, and the screw is formed by the through hole obliquely provided from the upper part of the seat plate to the inner end of the seat plate opening. Since it is installed obliquely downward to the front, the inert gas is jetted obliquely downward to the front of the screw from the supply port to fill all the small spaces created between the molding materials. Therefore, the effect of preventing the oxidation of the molding material is superior to the case of supplying the inert gas to the hopper, and the oxidation at the start of molding is also performed by supplying the inert gas to the gap formed between the heating cylinder and the residual resin. Since it can be prevented, defective products are reduced and the rise time of the molding machine can be shortened.

Further, since the inert gas supply hole is provided on the rear wall of the molding material supply port, it is not affected by the heating by the band heater on the outer periphery of the heating cylinder, and the heat transfer around the supply port by the heating cylinder is Since it is suppressed by the molding material that passes through the supply port, the temperature around the supply hole does not rise even if molding is continued for a long time, and there is no thermal effect on the supply pipe connected to the supply hole. The connection structure of the device is simplified.

Further, the means for supplying the inert gas in the injection device may be provided by obliquely providing the supply holes in the seat plate of the hopper and making the respective parts of the material supply section airtight. In particular, the supply holes are formed by forming through holes in the seat plate. Since there is no need to significantly improve the usual injection equipment and the supply port does not become narrow due to the inert gas supply pipe etc., it is possible to supply the molding material smoothly. Have.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional side view of a main part of an injection device including an inert gas supply means of the present invention.

[Explanation of symbols]

 1 Heating Tube 2 Band Heater 3 Screw 4 Packing 5 Seating Board 6 Hopper 7 Supply Port 8 Supply Hole 10 Supply Pipe 11 Cover Member 13 Seal Ring 14 Seal Ring 15 Seal Ring 16 Inert Gas Supply Device 20 Flow Control Valve

Claims (1)

(57) [Claims] 1. A packing for airtightly closing a gap between the heating cylinder having a screw for injection inside and a rear part of the heating cylinder is fitted, and an opening is provided at an upper portion of the heating cylinder in front of the packing. To form a material supply part, and the seating plate of the hopper is placed on the upper part of the heating cylinder of the material supply part by superimposing the central opening on the above opening and integrally fixed, and the molding material formed by the superposition of this opening An inert gas supply hole is provided on the rear wall of the supply port, and is obliquely provided downward from the upper part of the seat by the through hole obliquely provided at the inner end of the seat opening toward the front of the screw, and at the outer end of the supply hole. The inert gas supply pipe is connected to the receiving port on the seat panel provided, and the hopper sealed by the lid member is attached to the seat plate, and the connection part between the hopper and the seat plate and the heating cylinder around the supply port are provided. Inert supplied with airtight contact with seat An injection device provided with an inert gas supply means, characterized in that gas leakage is prevented.