JP2009040023A - Method and apparatus for feeding nitrogen gas to injection molding machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problems in the process of driving air away in a cavity that it is necessary to send nitrogen gas instantaneously in a large volume causing adiabatic expansion and resulting in cooling inside the cavity which affects fluidity of the molten resin, and further causing a backflow of the resin into a hole for feeding the nitrogen gas and resulting in leaving a mark of the hole on the molded article and deteriorating appearance so that adjustment work is necessary. <P>SOLUTION: When the molten resin is injected into the cavity 60 sandwiched between a fixed mold 40 and a movable mold 50 from a sprue 70 via a gate 79, the nitrogen gas to be sent into the cavity 60 is heated in advance during the process of sending it. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method and apparatus for supplying nitrogen gas to an injection molding machine. More specifically, the invention relates to feeding heated nitrogen gas into a cavity sandwiched between a fixed mold and a movable mold. In addition, by sending nitrogen gas when the fixed mold and the movable mold are closed, the flow of the resin is kept good, and further, the deterioration of the resin material, the generation of black spots which are oxidizing substances, and the resin burn are generated. It describes the technology to prevent this.

  As a conventional technique related to a method and apparatus for supplying nitrogen gas to an injection molding machine, a method that does not leave air in the cavity and a method that expels the air in the cavity have been proposed.

  In this case, in the method that does not leave air in the cavity, the entire chamber in which the injection molding machine is installed is filled with nitrogen gas, and the cavity is filled with nitrogen gas when the fixed mold and the movable mold are closed. Has been proposed.

  In the method of expelling the air in the cavity, as a method for expelling the air in the cavity and filling the nitrogen gas, a hole is made from the side of the fixed mold or the movable mold and nitrogen gas is injected.

  However, there are many problems as described below with respect to such conventional techniques.

  That is, in the method that does not leave air in the cavity, there is a problem that the entire apparatus is too large.

  In addition, in the method of expelling the air in the cavity, it is absolutely necessary to send a large amount of nitrogen gas instantaneously, so that adiabatic expansion is performed, resulting in cooling the cavity and adversely affecting the fluidity of the molten resin. In addition, the resin flowed back into the hole for supplying nitrogen gas, and the mark of the hole was attached to the molded product, so that the appearance was bad and rework was required.

  In the present invention, when the molten resin is injected from the spool 70 into the cavity 60 sandwiched between the fixed mold 40 and the movable mold 50 via the gate 79, nitrogen gas is previously fed into the cavity 60. In the method of supplying nitrogen gas to an injection molding machine, the nitrogen gas to be fed is heated, and the nitrogen gas to be fed is controlled to have a heating temperature close to a melting temperature and to control a flow rate. Further, the nitrogen gas to be fed is characterized in that the temperature to be heated is controlled to about the atmospheric temperature and the flow rate can be controlled, and further, the nitrogen gas to be fed is The fixed mold 40 and the movable mold 50 are fed when they are closed, and the nitrogen gas to be fed fills the cavity 60. Further, the heating is stopped at the moment when only the surface of the cavity 60 is heated, and then the molten resin is injected into the cavity 60. Further, the position of the gate 79 is as follows. In the vicinity, the nitrogen gas is a place where it is possible to cover the front surface of the molten resin immediately after being injected into the cavity 60. Further, the nitrogen gas to be fed is 0.1 to 1 MPa. By solving this problem, the above-mentioned problems have been solved.

  Further, according to the present invention, when the molten resin is injected from the spool 70 via the gate 79 into the cavity 60 sandwiched between the fixed mold 40 and the movable mold 50, nitrogen gas is fed into the cavity 60 in advance. In the apparatus for supplying nitrogen gas to the injection molding machine, an electromagnetic valve 140 that can be opened and closed is disposed in the middle of the nitrogen gas pipe 150 for feeding nitrogen gas into the cavity 60 to control the operation of the injection molding machine. The nitrogen gas to be fed is fed when the stationary mold 40 and the movable mold 50 are closed, and then the cavity 60 is filled. And stopping at the moment when only the surface of the cavity 60 is heated, and then the molten resin is injected into the cavity 60, The nitrogen gas pipe 150 is connected to the cavity 60 via an inlet 81, a flow path 80, a gap 85 having a smaller cross-sectional area than the flow path 80, and an opening 89, and The size of the gap 85 is 0.01 to 0.02 mm, and further, a tank 120 for storing nitrogen gas is provided upstream of the electromagnetic valve 140. In addition, a heater 110 that can be heated is disposed anywhere in the nitrogen gas pipe 150 to the electromagnetic valve 140. Further, the heater 110 is connected to the controller 130 to obtain a temperature. The above-mentioned problem has been solved by the feature that it is possible to manage the above.

  As is clear from the above description, the present invention can provide the following effects.

  First, by heating the nitrogen gas to be fed, and by placing a heater that can be heated anywhere in the nitrogen gas piping to reach the solenoid valve, the resin material deteriorates and black spots that are oxidants are removed. On the other hand, it was possible to keep the flow of the resin good by solving the problem that the surface of the cavity cooled when nitrogen gas was fed while ensuring the prevention of generation and resin burn.

  Secondly, the nitrogen gas fed in can control the flow temperature of the general-purpose resin particularly well by controlling the heating temperature close to the melting temperature and controlling the flow rate.

  Third, the nitrogen gas fed in can control the heating temperature to about the atmospheric temperature and control the flow rate, so that the flow of the engineering plastic resin can be kept particularly good.

  Fourth, the heater can manage the temperature by connecting with a controller, thereby making it possible to maintain a good resin flow.

  Fifth, the nitrogen gas to be sent is sent when the fixed mold and the movable mold are closed, so that it is possible to supply effective nitrogen gas without waste at a very ideal timing. .

  Sixth, the nitrogen gas to be fed is filled in the cavity and stopped at the moment when only the surface of the cavity is heated, and then the molten resin is injected into the cavity, so that the fluidity of the molten resin is also considered. It has become possible to supply effective nitrogen gas without waste at very ideal timing.

  Seventh, the position where nitrogen gas is fed into the cavity is in the vicinity of the gate and is a place where the front surface of the molten resin can be covered immediately after the nitrogen gas is injected into the cavity. By making the positional relationship between the feeding and the molten resin injected into the cavity ideal, the effect of covering the periphery of the molten resin with nitrogen gas was ensured.

  Eighth, since the nitrogen gas to be fed is 0.1 to 1 MPa, it is possible to fill the cavity with the nitrogen gas in a short time, and it is possible to always ensure stable quality.

  Ninth, supply and injection of nitrogen gas by installing a solenoid valve that can be opened and closed in the middle of the nitrogen gas piping that feeds nitrogen gas into the cavity, and connected to a controller that controls the operation of the injection molding machine It became possible to control the molding machine integrally.

  Tenth, the nitrogen gas pipe is connected to the cavity through the inlet, the flow path, and the gap and opening having a smaller cross-sectional area than the flow path, thereby opening the opening and gap that are holes for supplying nitrogen gas. The resin does not flow backward, and the mark of the hole is left on the molded product, so that it does not look good and it is not necessary to rework it.

  Eleventhly, the size of the gap is 0.01 to 0.02 mm, which causes problems due to poor appearance due to the marks of the holes on the molded product due to the holes for supplying nitrogen gas. That was solved.

  Twelfth, by installing a tank that stores nitrogen gas upstream of the solenoid valve, it is possible to supply a large amount of nitrogen gas instantaneously, ensuring stable quality at all times. It became.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
Here, FIG. 1 is a view showing an injection molding machine, FIG. 2 is a view showing the whole of the present invention, and FIG. 3 is a detailed view of part A of the present invention.

  As shown in FIG. 1, reference numeral 10 denotes a plasticizing cylinder, which constitutes a part of an injection molding machine and does not specifically show individual parts, but a barrel, a screw, etc. Consists of. A plurality of heaters are located on the outer periphery of the barrel, a head is located at the tip, and a screw fitted to be further rotatable inward and movable in the axial direction. Further, a pusher, a backflow prevention ring, and a screw head are disposed on the tip end side of the screw.

  In addition, a hopper storing pellets as a resin material is located in the upper part of the barrel constituting the plasticizing cylinder 10 relatively rearward, and the resin can be dropped and sent to the plasticizing cylinder 10. It is possible. The sent resin is sent to the tip of the screw by the rotation of the screw while being melted and kneaded by the plasticizing cylinder 10.

  However, in an injection molding machine that melts and molds a resin, oxidation during the melting of the resin is a problem. Specifically, there are problems such as deterioration of the resin, generation of black spots that are oxidizing substances, and occurrence of resin burn.

  This oxidation occurs because the resin is melted by the plasticizing cylinder 10 that melts and kneads the resin around the pellets that are the material of the resin, and the molten resin produced in this melting process is fixed. This is an injection process for injecting into the cavity 60 filled with air sandwiched between the mold 40 and the movable mold 50. The present invention aims to prevent oxidation in this injection process.

  On the other hand, the injection molding machine comprises a fixed plate 20, a fixed mold 40 connected to the fixed plate 20, and a movable plate 30 and a movable mold 50 connected to the movable plate 30. In this case, a cavity 60 in the shape of a molded product is formed between the fixed mold 40 and the movable mold 30. In the injection process, the molten resin melted and kneaded by the plasticizing cylinder 10 is injected into the cavity 60.

  In other words, when the movable platen 30 moves and closes the fixed mold 40 and the movable mold 50 from the state in which the fixed mold 40 and the movable mold 50 are opened to take out the molded product, the surrounding air is closed. Is confined in the cavity 60. In the injection process, molten resin melted and kneaded by the plasticizing cylinder 10 is injected into the cavity 60.

  Here, in the present invention, by heating the supplied nitrogen gas, the temperature of the nitrogen gas that is self-cooled by adiabatic expansion is increased, so that the temperature in the cavity 60 is not lowered, but rather The temperature of the surface in the cavity 60 was raised so as to keep the flow of the resin good.

  Therefore, as seen in FIGS. 2 and 3, when viewed as a flow of molten resin, the spool 70 formed in the fixed mold 40 from the tip of the screw constituting the plasticizing cylinder 10. In addition, while being connected to the cavity 60 via the gate 79, the molten resin is fed into the cavity 60 via these positions during the injection process. .

  On the other hand, when considered as a flow of nitrogen gas, the final flow passes from the inlet 81 formed outside the movable mold 50 through the flow path 80 and further through the gap 85 having a smaller cross-sectional area than the flow path 80. Thus, it is connected to the cavity 60 through the opening 89, and nitrogen gas is fed there.

  In this case, the size of the gap 85 is such that the molten resin and the nitrogen gas are opposed to each other at the opening 89, and the molten resin has a considerable viscosity at a high temperature, and the nitrogen gas has a viscosity as a property. Since there is almost no value, a value of 0.01 to 0.02 mm can be said to be the most ideal value at which the molten resin does not flow backward to the gap 85 side. However, a reasonable effect can be confirmed even with a value of 0.005 to 0.05 mm.

  The position where the injection port 81 is formed need not be limited to the outside of the movable mold 50 and may be formed outside the fixed mold 40. Of course, in that case, the flow path 80, the gap 85, and the opening 89 are also formed in the fixed mold 40. On the other hand, two cavities 60 are formed in FIG. 2, but may be one, three, or more.

  In addition, the opening 89 of the gap 85 connected to the cavity 60 is considered to be the vicinity of the gate 79 from which the molten resin is injected or the molten resin is not specifically illustrated in consideration of the flow of the injected molten resin. Ideally, it is provided on the spool 70 or the gate 79 where the resin flows, and covers the front surface of the molten resin from which the injected nitrogen gas is injected to prevent oxidation.

  Now, with the cavity 60 sandwiched between the fixed mold 40 and the movable mold 50 closed, nitrogen is injected through the flow path 80 from the injection port 81. In order to inject from the narrow gap 85, nitrogen gas having a predetermined pressure and a predetermined flow rate, more specifically, a large amount of nitrogen gas is required instantaneously. In this case, in order to fill the cavity 60 with nitrogen gas in a short time, a value of 0.3 to 0.5 MPa can be said to be the most ideal value. However, a reasonable effect can be sufficiently confirmed even at a value of 0.1 to 1 MPa.

  In order to satisfy such a situation, the nitrogen gas pipe 150 is connected to the inlet 81. Therefore, the nitrogen gas pipe 150 is provided with a nitrogen gas generator 100 that produces nitrogen gas, a tank 120 for storing nitrogen gas in the middle thereof, and an electromagnetic valve 140 for opening and closing the flow path further downstream. is doing. By the way, regarding the nitrogen gas generating device 100, various methods such as liquid nitrogen gas and a separation membrane can be considered, but a pressure increasing device such as a pressure increasing valve for increasing the pressure is included in the method. You may think that

  Among them, the nitrogen gas stored in the tank 120 can be heated by the heater 110. However, the place to be heated is not limited to the tank 120, and any place including the nitrogen gas generator 100 and the electromagnetic valve 140 may be used.

  The electromagnetic valve 140 has various opening and closing operations including the opening and closing operations of the fixed mold 40 and the movable mold 50 and the injection of the molten resin, and the adjustment of shifting in advance and after the time. A controller 130 for controlling the injection molding machine is connected so that it can be controlled in accordance with the operation. Further, the heater 110 is configured so that the temperature of the nitrogen gas to be heated can be freely set and controlled according to the state of the injection molding machine such as the type, shape, and size of the molded product. The ON and OFF switches are connected to a controller 130 that controls the injection molding machine.

  Here, the reason why the nitrogen gas needs to be heated by the heater 110 is that the release of the high-pressure nitrogen gas into the atmospheric pressure cavity 60 causes adiabatic expansion, and the temperature of the nitrogen gas itself. Will go down. On the other hand, the fact that the temperature is low is a fatal defect in molding the molten resin, so that the heater 110 tries to heat it before injecting nitrogen gas.

  On the other hand, in resin molding, it is important to keep the molten resin at a high temperature so that the molten resin flows easily. For this purpose, it is useful to keep the inner surface of the cavity 60 at a high temperature. However, in order to release the molded product from the cavity 60 sandwiched between the fixed mold 40 and the movable mold 50 quickly, it must be cooled. For this purpose, it is also necessary to heat the very thin surface of the cavity 60 in particular.

  The method and apparatus for supplying nitrogen gas to the injection molding machine according to the present invention are configured as described above, and the operation thereof will be described below.

  First, the plasticizing cylinder 10 of the injection molding machine melts and kneads the resin by adiabatic compression of a screw and a heater, and injects the resin into a cavity 60 sandwiched between the fixed mold 40 and the movable mold 50 for molding. Product.

  More specifically, in the plasticizing process, the heater disposed for the purpose of heating is energized, and the screw is rotated by the rotational movement of the screw driving device, so that the resin in the hopper is Then, it passes through the material supply port of the barrel and is further transferred to the front nozzle side along the spiral groove of the screw. The During this time, the screw is retracted by the pressure of the molten resin in the reservoir. When a predetermined amount of molten resin is stored, the rotation of the screw stops and the plasticizing process is completed.

  Next, an injection process is performed. That is, when the screw is advanced by the axial drive unit of the screw drive device, the stored molten resin passes through the nozzle, further passes through the spool 70 and the gate 79, and between the fixed mold 40 and the movable mold 50. It is injected into the sandwiched cavity 60. At this time, the backflow prevention ring is pressed against the front end portion of the presser to prevent the molten resin being stored from flowing back to the hopper side. Therefore, the front is higher than the backflow prevention ring in the barrel, but the back is not so high behind the backflow prevention ring. In addition, the proportion of unmelted resin increases as it approaches the material supply port behind the backflow prevention ring, and only the unmelted resin is in the vicinity of the material supply port, so that the unmelted resin is easily dispersed and moved. ing.

  On the other hand, the nitrogen gas fed into the cavity 60 for the purpose of preventing oxidation is made by the nitrogen gas generator 100, and finally connected to the inlet 81 formed in the movable mold 50 via the nitrogen gas pipe 150. However, it can be fed into the cavity 60. The tank 120 disposed in the middle of the nitrogen gas pipe 150 allows the nitrogen gas to be sent in a large amount of nitrogen instantaneously, and the nitrogen gas is heated by the heater 110 disposed in or near the tank 120. The electromagnetic valve 140 disposed downstream of the tank 120 enables the nitrogen gas to be sent and blocked from being sent.

  In addition, the solenoid valve 140 is connected to the controller 130 that controls the injection molding machine, so that it can be adapted to various operations of the injection molding machine including opening and closing of the fixed mold 40 and the movable mold 50 and injection of molten resin. Thus, the electromagnetic valve 140 can be opened and closed. Furthermore, by connecting the ON / OFF switch of the heater 110 to the controller 130 that controls the injection molding machine, the temperature of the nitrogen gas to be heated is injection molded such as the type, shape, and size of the molded product. It is possible to set freely according to the situation of the machine.

  Therefore, the nitrogen gas can be replaced with the purpose of expelling the air in the cavity 60 at the moment when the fixed mold 40 and the movable mold 50 are closed and before the molten resin is injected.

  Further, the nitrogen gas fed into the cavity 60 is controlled to a heating temperature in the vicinity of the melting temperature of 150 to 450 ° C. in the case of a general-purpose resin, and the heating temperature is controlled to 30 in the case of an engineering plastic resin. It is possible to control the flow rate by controlling the air temperature to about -80 ° C.

  In addition, the nitrogen gas to be fed is fed when the fixed mold 40 and the movable mold 50 are closed, and then is stopped at the moment when the cavity 60 is filled and only the surface of the cavity 60 is heated. Thereafter, the molten resin can be injected into the cavity 60.

  By the way, the nitrogen gas finally passes through the flow path 80 from the inlet 81 formed outside the movable mold 50, and further passes through the gap 85 having a smaller cross-sectional area than the flow path 80, and finally the opening 89 It is fed into the cavity 60 through. In this case, since high-pressure nitrogen gas is released all at once from the opening 89 of the gap 85 having a small cross-sectional area, the nitrogen gas is self-cooled by adiabatic expansion, thereby cooling the inside of the cavity 60 and flowing the molten resin. Impairs sex. Therefore, it is also intended by the present invention that the nitrogen gas is heated by the heater 110 in advance.

  The present invention relates to a method and apparatus for supplying nitrogen gas to an injection molding machine, and more particularly, by feeding heated nitrogen gas into a cavity sandwiched between a fixed mold and a movable mold, and also a fixed mold. The technology that keeps the flow of the resin good by feeding nitrogen gas when the movable mold is closed, and also prevents the deterioration of the resin material, the generation of black spots that are oxidizing substances, and the occurrence of resin burn It is stated.

  Diagram showing injection molding machine   Diagram showing the entire invention of the present application   Detailed view of part A of the present invention

Explanation of symbols

10 .... Plasticizing cylinder 20 .... Fixed plate 30 ...... Moveable plate 40 ...... Fixed die 50 ...... Moveable die 60 ... ... Cavity 70 ... Spool 79 ... Gate 80 ... Flow path 81 ... Inlet 85 ... Gap 89 ... ... Opening part 100 ... Nitrogen gas generator 110 ... Heater 120 ... Tank 130 ... Controller 140 ... Solenoid valve 150 ... ..Nitrogen gas piping

Claims (14)

  When the molten resin is injected from the spool (70) through the gate (79) into the cavity (60) sandwiched between the fixed mold (40) and the movable mold (50), the cavity (60) is previously provided. A method for supplying nitrogen gas to an injection molding machine, wherein the nitrogen gas to be supplied to an injection molding machine is heated.   2. The method of supplying nitrogen gas to an injection molding machine according to claim 1, wherein the nitrogen gas fed in is controlled to have a heating temperature close to a melting temperature and a flow rate.   The method for supplying nitrogen gas to an injection molding machine according to claim 1, wherein the nitrogen gas to be fed is controlled to have a heating temperature of about the atmospheric temperature and a flow rate can be controlled.   4. The nitrogen gas to be fed is fed when the stationary mold (40) and the movable mold (50) are closed. 5. A method for supplying nitrogen gas to an injection molding machine.   The nitrogen gas to be fed is filled at the moment when the inside of the cavity (60) is filled and only the surface of the cavity (60) is heated, and then the molten resin is injected into the cavity (60). A method for supplying nitrogen gas to the injection molding machine according to claim 4.   The position where nitrogen gas is fed into the cavity (60) is in the vicinity of the gate (79), and is a place where the front surface of the molten resin can be covered immediately after the nitrogen gas is injected into the cavity (60). The method for supplying nitrogen gas to an injection molding machine according to any one of claims 1 to 5, wherein:   The method for supplying nitrogen gas to an injection molding machine according to any one of claims 1 to 6, wherein the nitrogen gas fed in is 0.1 to 1 MPa.   When the molten resin is injected from the spool (70) through the gate (79) into the cavity (60) sandwiched between the fixed mold (40) and the movable mold (50), the cavity (60) is previously provided. In a nitrogen gas supply device for an injection molding machine in which nitrogen gas is fed into the solenoid valve (140), which can be opened and closed in the middle of a nitrogen gas pipe (150) that feeds nitrogen gas into the cavity (60). And a controller (130) for controlling the operation of the injection molding machine, and a nitrogen gas supply device for the injection molding machine.   The nitrogen gas to be fed is fed when the stationary mold (40) and the movable mold (50) are closed, and then fills the cavity (60) and fills the cavity (60). The apparatus for supplying nitrogen gas to an injection molding machine according to claim 8, wherein the apparatus is stopped at the moment when only the surface is heated, and then the molten resin is injected into the cavity (60).   The nitrogen gas pipe (150) is connected to the cavity (60) via an inlet (81), a flow path (80), a gap (85) having a smaller cross-sectional area than the flow path (80), and an opening (89). The apparatus for supplying nitrogen gas to the injection molding machine according to claim 8 or 9, wherein the apparatus is connected to the injection molding machine.   The apparatus for supplying nitrogen gas to an injection molding machine according to claim 10, wherein the size of the gap (85) is 0.01 to 0.02 mm.   The tank (120) for storing nitrogen gas is disposed upstream of the electromagnetic valve (140), wherein nitrogen gas for the injection molding machine according to any one of claims 8 to 11 is disposed. Feeding device.   The heater (110) which can be heated is arrange | positioned in any place from the said nitrogen gas piping (150) to the said electromagnetic valve (140), The any one of Claim 8 thru | or 12 characterized by the above-mentioned. Nitrogen gas supply device for the injection molding machine described in 1.   The apparatus for supplying nitrogen gas to an injection molding machine according to claim 13, wherein the heater (110) is capable of managing temperature by being connected to the controller (130).

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