JP7527454B2 - Gas replacement method and device for injection molding machine - Google Patents

Description

The present invention relates to a gas replacement method and device for an injection molding machine, which replaces the gas inside a screw cylinder of the injection molding machine.

Currently, injection molding is the most widely used method for manufacturing plastic resin products. An injection molding machine that carries out the injection molding method heats and melts the plastic material inside the machine, pressurizes the molten material, and then cools and solidifies it to obtain a molded product.

The injection molding machine is composed of a hopper for storing and supplying the resin material, a heater for heating and melting the resin material, a screw/cylinder for pressurizing and supplying the resin material, and an ejection nozzle for injecting the molten resin material into a mold.

The above-mentioned injection molding machines heat and melt the resin material inside the screw and cylinder, so the oxygen in the air causes the resin material to oxidize (burn). This can cause problems such as the resin burning inside the molding machine or the burnt resin getting into the molded product, resulting in defective products.

To prevent the above phenomenon, measures have been taken to inject an inert gas (nitrogen, argon, etc.) from the hopper into the screw cylinder as a purge gas to replace the atmosphere inside the screw cylinder.

The applicant is aware of the following patent documents 1 and 2 as prior art documents related to this type of gas replacement technology.

Japanese Patent Application Publication No. 3-248826 Japanese Patent Application Publication No. 9-10910

The above-mentioned Patent Document 1 relates to a "gas replacement device for an injection molding machine" and includes the following description.
2. Claims
(1) A gas replacement device for an injection molding machine, characterized in that a change-over valve for gas suction, ejection and resin injection is provided in a resin injection section of an injection molding machine for injection molding of thermoplastic resin.
[Page 2, upper left column, lines 18 to 20]
Reference numeral 1 denotes a nozzle which is a resin injecting portion of an injection molding machine, and a gas replacement device 3 of the present invention is attached to the tip of this nozzle 1 via a mounting frame 2.
[Page 2, upper right column, lines 7 to 10]
The mounting nozzle body 5 is equipped with a switching valve 9 for gas suction, ejection and resin injection, which is rotatable via a rotary drive shaft 8 of a motor 7 fixed to the mounting frame 2 .
[Page 2 of the publication, lower right column, lines 8 to 12]
Thereafter, the gas suction/ejection switching valve 13 is operated to connect the end 12b of the conduit 12 to the conduit 15, and the gas suction/ejection hole 11 is connected to the rotary pump 16, which is then operated to suck out the air from within the mold.
[Page 2, lower right column, line 17 to page 3, upper left column, line 9]
Therefore, after the suction process via the rotary pump 16 is completed, in conjunction with the stopping of the rotary pump 16, the switching valve 13 is switched to connect the conduit 12 to the inert gas injection device 14, and the device 14 is operated to suck in the inert gas stored in the device 14 in the above process and inject it into the mold through the injection hole 11 and the nozzle hole 4, thereby replacing the inside of the cavity with the inert gas.
Then, after the inert gas injection device 14 is stopped, the motor 7 is operated again to rotate the switching valve 9, and the resin injection hole 10 of the switching valve 9 is again aligned with the nozzle holes 4 and 6 to connect both the nozzle holes 4 and 6, and then the resin is injected from the nozzle 1.

The above-mentioned Patent Document 2 relates to an "injection molding method and injection molding machine for light alloy injection material" and includes the following description.
[0005]
...Even during molding as described above, the inside of the hopper is kept in an inert gas atmosphere continuously or intermittently. By keeping the inside of the hopper in an inert gas atmosphere, the screw supply section below the hopper is also kept in an inert gas atmosphere. ...
[0012]
During the preparation period for starting molding, the inert gas replacement jig 50 is slid by a drive device, for example, a hydraulic piston mechanism not shown, to the first position where the opening 52 is aligned with the injection nozzle 3 in the axial direction, as shown in FIG. 1. Then, pressure oil is supplied to the hydraulic chamber 8 on the piston rod side of the piston-cylinder device 5. Then, the injection nozzle 3 touches the opening 52 of the inert gas replacement jig 50. Then, the main valve 42' of the second pressure vessel 41' is opened. Then, the inert gas adjusted to a predetermined pressure by the pressure regulator 48 is supplied from the gas passage 51 of the inert gas replacement jig 50 to the opening 52 by the second gas supply pipe 46. This places the tip of the injection nozzle 3 in an inert gas atmosphere. The main valve 42 of the first pressure vessel 41 is also opened. Then, the inert gas, whose pressure has been adjusted to a predetermined value by the pressure regulator 44 and whose flow rate has been controlled to a predetermined value by the flow regulator 45, is supplied from the branch pipes 43', 43" to the main body 21 of the hopper 20 and the vicinity of the supply port 24. As a result, the inside of the main body 21 of the hopper 20, the vicinity of the supply port 24, and the screw supply section 16 below the hopper 20 are placed in an inert gas atmosphere.

In the technology disclosed in the above-mentioned Patent Document 1, a gas replacement device 3 with a complex structure is attached to the tip of the nozzle 1, and the inside of the cavity of the mold is suctioned and then an inert gas is introduced to replace the gas. In this way, even if only the inside of the cavity of the mold is gas replaced, the nozzle 1 is supplied with resin material from a hopper together with air. Therefore, when the resin melts in the nozzle 1, it is not possible to prevent the resin from burning, which occurs in the molten resin. In other words, it does not fundamentally solve the problems of resin burning and defective products caused by the burning of the resin heated and melted inside the nozzle 1 (screw/cylinder).

The technology disclosed in the above Patent Document 2 supplies inert gas to the main body 21 of the hopper 20 and near the supply port 24. However, this only places the screw supply section 16 below the hopper 20 in an inert gas atmosphere. For this reason, in the above Patent Document 2, an inert gas replacement jig 50 is also provided at the tip of the injection nozzle 3, and the tip of the injection nozzle 3 is placed in an inert gas atmosphere. In other words, simply supplying inert gas to the main body 21 of the hopper 20 and near the supply port 24 cannot sufficiently prevent the resin from burning during melting, so the inert gas replacement jig 50 is also provided at the tip of the injection nozzle 3. As such, there is a problem that the device becomes complicated and the control thereof becomes complicated.

In this way, in the conventional gas replacement method, an inert gas is injected from the hopper section to replace the atmosphere inside the hopper and in the cylinder section located at the bottom of the hopper. However, since the cylinder section of the injection molding machine is not provided with a gas vent, the purge gas injected from the hopper section cannot pass through the cylinder section. The purge gas passes only through the end of the cylinder section from the injection point, and then makes a U-turn and escapes to the top of the hopper. In this way, the purge does not function effectively in the conventional method, and it takes a long time to replace the atmosphere in the cylinder section. For this reason, the injection of the purge gas is continued even while the injection molding machine is stopped.

The present invention has been made in order to solve the above problems and with the following objectives.
A gas replacement method and device for an injection molding machine that can efficiently replace gas inside the screw cylinder of the injection molding machine with a simple device and control.

In order to achieve the above object, the gas replacement method for an injection molding machine according to claim 1 employs the following configuration.
1. A method for replacing gas in a screw cylinder in an injection molding machine including a heat-melting section for heating and melting an injection material supplied from a supply means, and a screw cylinder having a screw for extruding the injection material melted in the heat-melting section toward an injection hole at a tip thereof, comprising the steps of:
Further comprising a nozzle for ejecting an inert gas,
the ejection nozzle is disposed in the chute section of the supply means so as to extend vertically, and ejects the inert gas on the side of the supply means closer to the heat-melting section in the screw cylinder , and the tip of the ejection nozzle is bent in the chute section so that the ejection direction of the ejected inert gas has an inclination angle with respect to the axis of the screw cylinder,
The inert gas is ejected so that the nozzle opening of the ejection nozzle is directed toward the injection hole of the screw cylinder.

In order to achieve the above object, the gas replacement device for an injection molding machine according to the second aspect of the present invention employs the following configuration.
1. An apparatus for replacing gas in a screw cylinder in an injection molding machine comprising: a heat-melting section for heating and melting an injection material supplied from a supply means; and a screw cylinder having a screw for extruding the injection material melted in the heat-melting section toward an injection hole at a tip thereof, comprising:
Further comprising a nozzle for ejecting an inert gas,
the ejection nozzle is disposed in the chute section of the supply means so as to extend vertically, and ejects the inert gas on the side of the supply means closer to the heat-melting section in the screw cylinder , and the tip of the ejection nozzle is bent in the chute section so that the ejection direction of the ejected inert gas has an inclination angle with respect to the axis of the screw cylinder,
The inert gas is ejected so that the nozzle opening of the ejection nozzle is directed toward the injection hole of the screw cylinder.

The gas replacement method for an injection molding machine according to claim 1 is a method for replacing gas in a screw cylinder of an injection molding machine equipped with a screw cylinder. The screw cylinder has a heat melting section and a screw. The heat melting section heats and melts the injection material supplied from a supply means. The screw extrudes the injection material melted in the heat melting section toward an injection hole at the tip. The method of the present invention further includes an ejection nozzle for ejecting an inert gas. The ejection nozzle ejects the inert gas on the side of the supply means of the screw cylinder relative to the heat melting section. A nozzle opening of the ejection nozzle ejects the inert gas toward the injection hole of the screw cylinder.
As a result, the air around the injection material supplied from the supply means before it melts is replaced with inert gas, and the injection material in this state is melted and extruded for injection. Therefore, compared to the conventional method, the gas replacement inside the screw cylinder can be performed efficiently with simple equipment and control, fundamentally solving the problem of burning inside the screw cylinder and the occurrence of defective products due to resin burning.
The ejection nozzle is disposed so as to extend vertically within the chute of the supply means, and the tip of the ejection nozzle is bent within the chute so that the ejection direction of the ejected inert gas has an inclination angle with respect to the axis of the screw cylinder. This allows the nozzle opening of the ejection nozzle to eject the inert gas toward the injection hole of the screw cylinder. In this way, by ejecting the inert gas at a predetermined inclination with respect to the axis of the screw cylinder, the gas in the screw cylinder is pushed out by the ejected inert gas. This allows for effective gas replacement.

The gas replacement device for an injection molding machine according to claim 2 is a device for replacing gas in a screw cylinder of an injection molding machine equipped with a screw cylinder. The screw cylinder has a heat melting section and a screw. The heat melting section heats and melts the injection material supplied from a supply means. The screw extrudes the injection material melted in the heat melting section toward an injection hole at the tip. The device of the present invention further includes an ejection nozzle for ejecting an inert gas. The ejection nozzle ejects the inert gas on the side of the supply means of the screw cylinder relative to the heat melting section. A nozzle opening of the ejection nozzle ejects the inert gas toward the injection hole of the screw cylinder.
As a result, the air around the injection material supplied from the supply means before it melts is replaced with inert gas, and the injection material in this state is melted and extruded for injection. Therefore, compared to the conventional method, the gas replacement inside the screw cylinder can be performed efficiently with simple equipment and control, fundamentally solving the problem of burning inside the screw cylinder and the occurrence of defective products due to resin burning.
The ejection nozzle is disposed so as to extend vertically within the chute of the supply means, and the tip of the ejection nozzle is bent within the chute so that the ejection direction of the ejected inert gas has an inclination angle with respect to the axis of the screw cylinder. This allows the nozzle opening of the ejection nozzle to eject the inert gas toward the injection hole of the screw cylinder. In this way, by ejecting the inert gas at a predetermined inclination with respect to the axis of the screw cylinder, the gas in the screw cylinder is pushed out by the ejected inert gas. This allows for effective gas replacement.

FIG. 1 is a configuration diagram illustrating a gas replacement device of an injection molding machine according to an embodiment of the present invention. FIG. 4 is a diagram illustrating a gas replacement method for the injection molding machine of the above embodiment. FIG. 1 is a configuration diagram illustrating a test device used in a demonstration test performed as an example. FIG. 2 is a diagram illustrating the test device. FIG. 13 is a schematic diagram illustrating a change in the ejection flow rate in the second test.

Next, we will explain how to implement the present invention.

〔overview〕
FIG. 1 is a configuration diagram for explaining a gas replacement device for an injection molding machine according to an embodiment of the present invention.
The present embodiment relates to an apparatus and method for replacing gas within a screw cylinder 10 in an injection molding machine equipped with the screw cylinder 10.

[Screw cylinder 10]
The screw cylinder 10 has a cylindrical cylinder body 10A that is tapered at the tip and extends forward and backward. An injection hole 12 is formed at the tip of the cylinder body 10A, through which the heated and melted injection material is injected. The screw cylinder 10 has a heat melting part 20 and a screw 30.

[Heat melting section 20]
The heating and melting section 20 is for heating and melting the injection material (not shown) supplied from the supply means 11. The heating and melting section 20 is configured by providing a plurality of heaters 21 on the outer periphery of the tip side of the cylinder body 10A. The heaters 21 heat the cylinder body 10A, and the injection material filled inside is heated and melted.

[Screw 30]
The screw 30 is for extruding the injection material melted in the heat melting portion 20 toward the injection hole 12 at the tip. The screw 30 is inserted into the cylinder body 10A so as to be coaxial with the cylinder body 10A. The tip of the screw 30 is located near the narrowed tip of the cylinder body 10A. The rear end of the screw 30 is connected to a motor (not shown). The screw 30 is provided with a flange 31 for preventing the injection material from leaking from the rear end opening of the cylinder body 10. A helical ridge 32 for feeding the injection material toward the tip side is formed on the outer periphery of the screw 30 on the tip side of the flange 31.

[Supply Means 11]
The supply means 11 is for supplying the temporarily stored injection material into the screw cylinder 10. In this example, the supply means 11 is formed to include a hopper section 11A and a chute section 11B. The hopper section 11A is funnel-shaped, widening upward, and receives and stores the injection material. The chute section 11B is a tubular body that connects a lower end opening 13 of the hopper section 11A to a supply port 14 formed in the cylinder body 10A.

The supply port 14 of the cylinder body 10A is formed on the base side of the heat melting portion 20. In other words, the supply port 14 is provided on the base side of the heat melting portion 20 of the screw cylinder 10 and on the tip side of the flange 31 of the screw 30. New injection material is supplied into the screw cylinder 10 from the supply port 14.

[Injection material]
The injection material may be a resin material such as a thermoplastic resin or a metal material such as a light alloy. The injection material is supplied in the form of pellets to the hopper section 11A of the supply means 11. The injection material passes through the chute section 11B while remaining in the form of pellets and is supplied into the screw cylinder 10. In the screw cylinder 10, the injection material is gradually sent to the tip side by the rotation of the screw 30, and is heated and melted when it reaches the heat melting section 20. The melted injection material is injected from the injection hole 12 and injected into the cavity of a mold (not shown).

[Ejection nozzle 40]
This embodiment further includes an ejection nozzle 40 for ejecting an inert gas.
The ejection nozzle 40 ejects the inert gas on the supply means 11 side of the heat melting portion 20 in the screw cylinder 10. The nozzle opening of the ejection nozzle 40 ejects the inert gas so as to face the injection hole 12 side of the screw cylinder 10. In this example, the ejection nozzle 40 is configured so that the ejection direction of the inert gas ejected from the nozzle opening 41 has an inclination angle with respect to the axis of the screw cylinder 10.

The ejection nozzle 40 is supplied with an inert gas from an inert gas supply source (not shown). The inert gas may be nitrogen gas or argon gas.

In this example, the ejection nozzle 40 is disposed within the chute section 11B of the supply means 11. The ejection nozzle 40 in the illustrated example is disposed so as to extend vertically within the chute section 11B, and the lower tip is bent at a predetermined inclination angle, so that the inert gas is ejected from the nozzle opening 41 at the tip in an ejection direction that has an inclination angle with respect to the axis of the screw cylinder 10.

The inclination angle can be set to, for example, an angle greater than 0° and less than about 60°.

It is preferable that the ejection nozzle 40 intermittently switches the ejection flow rate of the inert gas. Specifically, this can be achieved by controlling the opening and closing of an on-off valve 42 provided in an introduction path for introducing the inert gas into the ejection nozzle 40. In the figure, reference numeral 43 denotes a control unit 43 that controls the on-off valve 42.

Figure 2 is a diagram illustrating an example of a gas replacement method for the injection molding machine of the above embodiment. Specifically, it shows the change in the ejection flow rate when the inert gas is ejected from the ejection nozzle 40. The horizontal axis is the elapsed time, and the vertical axis is the flow rate.

In this example, the opening and closing control of the on-off valve 42 is not a gradual opening and closing operation, but an on-off control that opens and closes the valve all at once. Therefore, when the valve is opened, the flow rate increases suddenly at a steep rate of increase and becomes a constant flow rate, and when the valve is closed, the flow rate instantly becomes zero.

When the ejection nozzle 40 intermittently switches the ejection flow rate of the inert gas, it is preferable to set the time TS during which the ejection flow rate of the inert gas is low to be equal to or longer than the time TO during which the ejection flow rate of the inert gas is high. For example, the TS can be set to 1.5 times or more the TO. Also, the TS can be set to 4 to 5 times or less the TO. Preferably, the TS can be set to 2 to 3 times the TO. If the TS is shorter than the TO, it may be difficult to exhaust the gas from inside the screw cylinder 10, and the replacement efficiency may not be improved.

The TO can be set to, for example, 1 to 2 seconds. As mentioned above, the TS can be set to 1.5 times or more and 4 to 5 times or less than the TO.

[Effects of the embodiment]

The above embodiment is a method and device for replacing gas in a screw cylinder 10 in an injection molding machine equipped with the screw cylinder 10. The screw cylinder 10 has a heat melting section 20 and a screw 30. The heat melting section 20 heats and melts the injection material supplied from the supply means 11. The screw 30 extrudes the injection material melted in the heat melting section 20 toward the injection hole 12 at the tip. This embodiment further includes an ejection nozzle 40 for ejecting an inert gas. The ejection nozzle 40 ejects the inert gas on the side of the supply means 11 of the heat melting section 20 in the screw cylinder 10. A nozzle opening 41 of the ejection nozzle 40 ejects the inert gas so as to be directed toward the injection hole 12 of the screw cylinder 10.
As a result, the air surrounding the injection material supplied from the supply means 11 before it melts is replaced with inert gas, and the injection material in this state is melted and extruded for injection. Therefore, compared to the conventional method, the gas replacement inside the screw cylinder 10 can be performed efficiently with a simple device and control, fundamentally solving the problem of burning inside the screw cylinder 10 and the generation of defective products due to resin burning.

In the above embodiment, the ejection direction of the inert gas ejected from the nozzle opening 41 of the ejection nozzle 40 has an inclination angle with respect to the axis of the screw cylinder 10 .
If the inert gas is ejected at a predetermined inclination with respect to the axis of the screw cylinder 10, the gas in the screw cylinder 10 is pushed out by the ejected inert gas, thereby enabling effective gas replacement.

In the above embodiment, the ejection nozzle 40 intermittently switches the ejection flow rate of the inert gas.
By intermittently switching the ejection flow rate of the inert gas, the inert gas is fed into the screw cylinder 10 at a large ejection flow rate, and the gas in the screw cylinder 10 is discharged while the ejection flow rate is small. For example, by repeatedly ejecting and stopping the ejection of the inert gas intermittently, the inert gas is fed into the screw cylinder 10 by the ejection of the inert gas, and the gas in the screw cylinder 10 is discharged while the ejection is stopped. This allows for effective gas replacement.

In the above embodiment, when the ejection nozzle 40 intermittently switches the ejection flow rate of the inert gas, the time TS during which the ejection flow rate of the inert gas is low is set to be equal to or longer than the time TO during which the ejection flow rate of the inert gas is high.
During the time TS when the ejection flow rate is small, the gas in the screw cylinder 10 is discharged, and during the subsequent time TO when the ejection flow rate is large, the inert gas is fed into the screw cylinder 10. This allows for effective gas replacement.

〔Example〕
Test Equipment FIG. 3 is a configuration diagram for explaining the test equipment used in the demonstration test carried out as an embodiment of the present invention.
In this test apparatus, a model cylinder 50 was prepared in which the above-mentioned cylinder body 10A and chute portion 11B were modeled using resin pipe material. The model cylinder 50 has a cylinder model portion 50A corresponding to the cylinder body 10A and a chute model portion 50B corresponding to the chute portion 11B.

Figure 4 is a diagram explaining the above-mentioned test equipment, showing details of the model cylinder 50. (A) is the first example, and (B) is the second example.

The cylinder model part 50A and the chute model part 50B were both created using resin pipes cut to a specified length. The chute model part 50B was joined at a 90° angle to the base side of the cylinder model part 50A. The tip of the cylinder model part 50A was closed with a tip cap 51, and the base end of the cylinder model part 50A was also closed with a base cap 52. The upper opening of the chute model part 50B was closed with a plug 53 with an exhaust pipe 55.

The plug 53 is provided with a nozzle tube corresponding to the ejection nozzle 40. The first example in FIG. 4(A) is the first nozzle tube 54A, and the second example in FIG. 4(B) is the second nozzle tube 54B.

The tip of the first nozzle pipe 54A in the first example of FIG. 4A is bent at 45 degrees so that the direction of ejection of the inert gas is directed toward the tip side of the cylinder model part 50A.
In the second example of FIG. 4B, the second nozzle pipe 54B ejects the inert gas in a direction perpendicular to the axis of the cylinder model portion 50A.

Returning to FIG. 3, nitrogen gas is introduced into the nozzle pipe as an inert gas from a nitrogen gas cylinder 61. The nitrogen gas cylinder 61 is replenished with nitrogen gas from a nitrogen gas production device 65. A flow controller 63 and an on-off valve 64 are connected in parallel to the nitrogen gas introduction pipe 62. The on-off valve 64 corresponds to the on-off valve 42 in the device of FIG. 1. The flow controller 63 is used for continuous ejection of nitrogen gas from the nozzle pipe, and the on-off valve 64 is used for intermittent ejection of nitrogen gas from the nozzle pipe.

The cylinder model part 50A was provided with a tip port 72 near the tip, and an intermediate port 71 in the middle between the tip and the base. A sampling pump 73 and an oxygen concentration meter 74 were connected to the intermediate port 71, and a purge line 75 was connected to the sampling pump 73 to measure the oxygen concentration of the gas sampled from the cylinder model part 50A, allowing the oxygen concentration meter 74 to be purged with nitrogen. The oxygen concentration of the gas sampled from the intermediate port 71 was measured with the oxygen concentration meter 74, and gas replacement was evaluated. An air purge line 77 and an air compressor 76 were connected to the tip port 72, allowing the inside of the cylinder model part 50A to be purged with air. After each measurement, the inside of the cylinder model part 50A was purged with air to reset the state.

First test: First, air was poured into the cylinder model part 50A, and nitrogen gas was ejected from the nozzle tube for a certain period of time. The residual oxygen concentration of the gas sampled from the intermediate port 71 was then measured. The degree of gas replacement was evaluated by its maximum value. The smaller this value, the better the gas replacement inside the cylinder model part 50A was evaluated to be by ejecting nitrogen gas from the nozzle tube. The flow rate when ejecting nitrogen gas from the nozzle tube was all standardized to 10 L/min. In the continuous ejection, nitrogen gas was ejected continuously at a flow rate of 10 L/min. In the intermittent ejection, the ejection of nitrogen gas was turned ON/OFF so that the average ejection flow rate was 10 L/min. If the time was the same, the first and second examples ejected the same amount of nitrogen. The results are shown in Table 1 below.

As can be seen from Table 1, the longer the ejection time, the lower the residual oxygen concentration tends to be. In other words, the longer the ejection time, the more gas replacement inside the cylinder model section 50A progresses. In addition, when comparing continuous ejection with intermittent ejection, the intermittent ejection has a lower residual oxygen concentration, and gas replacement is more advanced. In addition, when comparing the ejection directions, the first example, which has an inclination angle, has a lower residual oxygen concentration than the downward second example, and gas replacement is more advanced. For example, after 120 minutes, the result is a residual oxygen concentration of 73,000 ppm for the continuous ejection of the second example, and 47,700 ppm for the intermittent ejection of the first example. Comparing the second example with the first example, the residual oxygen concentration is about 35% lower.

Second Test Next, the purging effect was compared by changing the nitrogen gas ejection flow rate when the ejection flow rate was switched intermittently.

FIG. 5 is a schematic diagram illustrating the change in the ejection flow rate in the second test.
5A is a diagram illustrating the change in the jetting flow rate in Experimental Example 1. The intermittent jetting flow rate (area A in the figure) was set to 10 L/min, and the continuous jetting flow rate was set to zero L/min. In other words, this is an intermittent pattern in which the jetting flow rate temporarily becomes zero.
5B is a diagram illustrating the change in the ejection flow rate in Experimental Examples 2 to 6. The intermittent ejection flow rate (area A in the figure) was changed to 9 L/min, 8 L/min, 7 L/min, 6 L/min, and 5 L/min, and the continuous ejection flow rate (area B in the figure) was changed to 1 L/min, 2 L/min, 3 L/min, 4 L/min, and 5 L/min. In other words, this is a pattern in which a constant amount is ejected continuously and the ejection amount is increased intermittently.
5C is a diagram illustrating the change in the ejection flow rate in Experimental Example 7. The continuous ejection flow rate (area B in the figure) was set to 10 L/min. In other words, this is a pattern in which a constant amount is ejected continuously.
In all patterns, the average ejection flow rate is 10 L/min, and the same amount of nitrogen gas is ejected for the same period of time.

In the above experimental examples 1 to 7, the measured oxygen concentration in the cylinder model part 50A after the ejection time was set to 30 minutes, 60 minutes, and 120 minutes, respectively, is shown in Table 2 below.

As shown in Table 2 above, when the nitrogen gas ejection flow rate was switched intermittently (Experimental Examples 1 to 6), better results were obtained than when nitrogen gas was ejected continuously (Experimental Example 7). The results tended to worsen as the intermittent ejection flow rate decreased. It can be considered that the flow of gas in the cylinder model section 50A was promoted by temporarily and completely stopping the ejection of nitrogen gas.

In addition, even if the nitrogen gas jetting is not completely stopped, the results tend to be better by intermittently switching the jetting flow rate. Specifically, if the intermittent jetting flow rate is 90% or more (Experimental Example 2), the effect is similar to that of Experimental Example 1. On the other hand, if the intermittent jetting flow rate is 80% or less (Experimental Examples 3 to 6), the effect is smaller.

〔summary〕
It is believed that by spraying nitrogen gas diagonally from above into the cylinder model part 50A, the gas inside the cylinder model part 50A is pushed and moved horizontally, and by spraying nitrogen gas intermittently, the gas in the cylinder model part 50A can be made to flow without being suppressed.

[Modifications]
Although the above describes a particularly preferred embodiment of the present invention, the present invention is not intended to be limited to the illustrated embodiment, but can be modified and embodied in various forms, and the present invention is intended to encompass various modified embodiments.

For example, in each of the above experimental examples, when the ejection flow rate of the inert gas is switched intermittently, the flow rate when the ejection flow rate is small and the flow rate when the ejection flow rate is large are fixed, but the flow rate when the ejection flow rate is small and the flow rate when the ejection flow rate is large can also be set in stages.

10: Screw cylinder 10A: Cylinder body 11: Supply means 11A: Hopper section 11B: Chute section 12: Injection hole 13: Lower end opening 14: Supply port 20: Heating and melting section 21: Heater 30: Screw 31: Flange 32: Spiral protrusion 40: Spray nozzle 41: Nozzle opening 42: Opening and closing valve 43: Control section 50: Model cylinder 50A: Cylinder model section 50B: Chute model section 51: Tip cap 52: Base cap 53: Plug 54A: First nozzle pipe 54B: Second nozzle pipe 55: Exhaust pipe 61: Nitrogen gas cylinder 62: Introduction pipe 63: Flow rate controller 64: Opening and closing valve 65: Nitrogen gas production device 71: Intermediate port 72: Tip port 73: Sampling pump 74: Oxygen concentration meter 75: Purge line 76: Air compressor 77: Air purge line

Claims (2)

1. A method for replacing gas in a screw cylinder in an injection molding machine including a heat-melting section for heating and melting an injection material supplied from a supply means, and a screw cylinder having a screw for extruding the injection material melted in the heat-melting section toward an injection hole at a tip thereof, comprising the steps of:
Further comprising a nozzle for ejecting an inert gas,
the ejection nozzle is disposed in the chute section of the supply means so as to extend vertically, and ejects the inert gas on the side of the supply means closer to the heat-melting section in the screw cylinder , and the tip of the ejection nozzle is bent in the chute section so that the ejection direction of the ejected inert gas has an inclination angle with respect to the axis of the screw cylinder,
a nozzle opening of the ejection nozzle ejecting the inert gas toward an injection hole of the screw cylinder. 1. An apparatus for replacing gas in a screw cylinder in an injection molding machine comprising: a heat-melting section for heating and melting an injection material supplied from a supply means; and a screw cylinder having a screw for extruding the injection material melted in the heat-melting section toward an injection hole at a tip thereof, comprising:
Further comprising a nozzle for ejecting an inert gas,
the ejection nozzle is disposed in the chute section of the supply means so as to extend vertically, and ejects the inert gas on the side of the supply means closer to the heat-melting section in the screw cylinder , and the tip of the ejection nozzle is bent in the chute section so that the ejection direction of the ejected inert gas has an inclination angle with respect to the axis of the screw cylinder,
a nozzle opening of the ejection nozzle ejecting the inert gas toward an injection hole of the screw cylinder.

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