JP2017105023A - Injection nozzle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an injection nozzle that is an injection nozzle used in a molding method in which the injection nozzle is alienated from a metal mold every molding cycle, can surely prevent the leakage from occurring and can shorten a molding cycle, the injection nozzle particularly suitable as an injection nozzle for sandwich molding.SOLUTION: An injection nozzle (5) that performs contact with a sprue of a metal mold (37) and alienation from the sprue for every molding cycle is targeted. The injection nozzle (5) provides a partition (23) in a tip resin flow path (22) that is a resin flow path in the neighborhood of the tip. An air nozzle (25) is provided such that air may be blown to an outer periphery surface in the neighborhood of the tip of the injection nozzle (5). The injection nozzle (5) is provided with a heater (33) on an outer periphery surface.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an injection nozzle used in a molding method for separating from a mold sprue for each molding cycle, and although not limited, a resin is injected from two injection devices to form a core layer and a skin layer The present invention relates to an injection nozzle suitable for an injection nozzle used in so-called sandwich molding.

  The injection molding machine includes a mold clamping device that clamps a mold, an injection device that injects an injection material into the clamped mold, and the injection device is provided with an injection nozzle. The injection nozzle must be in contact with the mold sprue at least in the injection process of injecting the molten resin from the injection device, but depending on the molding method, the injection nozzle may be separated from the mold in other processes. You may have to. For example, it is a case where two or more sets of molds are provided in the mold clamping device, and the molds of each set are switched to be clamped and injected. In such a case, it shape | molds as follows. A predetermined set of molds is clamped. The molten resin is injected by bringing the injection nozzle into contact with the sprue of the mold. Waiting for holding pressure, the injection nozzle is separated from the mold. The set of molds is then opened at an appropriate timing to obtain a molded product, but the mold clamping apparatus switches to another set of molds in parallel. The other set of molds is clamped. The molten resin is injected by bringing the injection nozzle into contact with the sprue of the mold. Waiting for holding pressure, the injection nozzle is separated from the mold. The other set of molds is then opened at an appropriate timing to obtain a molded product. In the same manner, the molding cycle is carried out by switching to a predetermined set of molds. That is, when such a molding method is carried out, the injection nozzle is separated from the mold every molding cycle.

  In the molding method in which the injection nozzle is separated from the sprue of the mold for each molding cycle, so-called sag dripping from the tip of the injection nozzle becomes a problem. This is because the occurrence of dripping causes the resin to adhere to the tip of the injection nozzle and hinder the next contact with the sprue and contaminate the surrounding environment. Various injection nozzles that prevent the occurrence of such dripping have been proposed. For example, an injection nozzle having a built-in shutoff valve composed of a needle valve is well known. An injection nozzle provided with a shut-off valve opens the shut-off valve when it is in contact with the sprue of the mold, and closes the shut-off valve when separated from the mold. If it does so, even if it separates an injection | spray nozzle from a metal mold | die, it will not generate. An injection nozzle in which a partition is provided in the resin flow path of the injection nozzle so that the cross-sectional area of the flow path is substantially halved is also known. Molten resin is a viscous fluid. Generally, when a viscous fluid is flowed by extruding a flow path at a predetermined pressure, if the pressure loss per length of the flow path is constant, the average flow velocity is the square of the inner diameter. Is proportional to That is, when the cross-sectional area is reduced, the flow resistance is increased and the flow rate is decreased. The injection nozzle in which the flow path is divided by the partition and the cross-sectional area of each of the divided flow paths is approximately ½ is increased in flow resistance, and is difficult to be broken. However, the degree to which the flow resistance increases depends on the length of the partition. In other words, if the length of the pipe line partitioned by the partition is short, the flow resistance does not increase so much, so the effect of preventing drooling is small. Patent Document 1 describes an injection nozzle capable of blowing air to the tip of the injection nozzle for preventing dripping. If air is blown before the injection nozzle is separated from the mold, the temperature of the molten resin near the tip temporarily decreases. If it does so, viscosity will become large and it will become difficult to rip off.

JP-A-6-297529 Japanese Patent No. 3609808

  By the way, as a molding method, there is so-called sandwich molding in which two types of resins are injected to obtain a molded product composed of a core layer and a skin layer. In an injection molding machine that performs sandwich molding, two injection devices are provided, and these are connected to a common injection nozzle. In sandwich molding, first, one injection device is driven to inject a predetermined amount of resin for the skin layer, and then the other injection device is driven to inject the resin for the core layer. Then, the first injected resin for the skin layer contacts the inner wall surface of the mold cavity and quickly solidifies, and then the injected resin for the core layer is filled in the center of the cavity. become. Thereby, a molded product composed of the core layer and the skin layer can be obtained.

  There are various injection nozzles for sandwich molding. For example, the injection nozzle proposed in Patent Document 2 can be cited. The injection molding machine described in this document is also provided with two injection devices, the first injection device is coaxial with the injection molding machine, and the second injection device is inclined with respect to the injection device. These first and second injection devices are provided with a common injection nozzle. The injection nozzle described in Patent Document 2 includes a nozzle body and an inner nozzle that is accommodated coaxially in the nozzle body. In this injection nozzle, the gap between the outer peripheral surface of the inner nozzle and the hole in the nozzle body in which the inner nozzle is accommodated constitutes the first resin flow path, and the through hole provided in the inner nozzle is the second. A resin flow path is configured. The resin for the skin layer can be injected from the first resin flow path, and the resin for the core layer can be injected from the second resin flow path. Such an injection nozzle also needs to be separated from the mold for each molding cycle depending on the molding method, and in that case, it is necessary to take some measures against the dripping.

  In the case of carrying out a molding method in which the injection nozzle is separated from the mold for each molding cycle, it is necessary to prevent dripping, and there are various mechanisms or methods as described above. However, these mechanisms and methods also have problems to be solved. First, considering the case where a shut-off valve is provided in the injection nozzle, if the shut-off valve can be provided, it is possible to reliably prevent the dripping. However, depending on the type of injection nozzle, a shut-off valve may not be provided. Specifically, an injection nozzle for sandwich molding becomes a problem. This is because the injection nozzle for sandwich molding has two resin flow paths formed therein, and the internal structure is complicated, so that it is practically impossible to provide a shut-off valve. In the case of the injection nozzle described in Patent Document 2, since at least the second resin flow path is provided in the inner nozzle, there is room for providing a shutoff valve. However, since the first resin flow path is formed on the outer peripheral surface of the inner nozzle and has an annular shape, a shut-off valve cannot be provided. That is, the injection nozzle for sandwich molding cannot substantially be provided with a shut-off valve. Next, when a method for providing a partition in the resin flow path of the injection nozzle and thereby reducing the cross-sectional area of the flow path is considered, this method has an effect that it is difficult to ridicule to some extent. However, if the length of the partition in the flow direction is insufficient, the effect of preventing drooling is not high. By the way, when the partition is provided in the injection nozzle for sandwich molding, it is conceivable that the partition is provided at the tip portion where the first and second resin flow paths merge, that is, the tip portion of the injection nozzle. If the length in the direction is long, it is necessary to increase the overall length of the injection nozzle, which is not practical. Further, when a resin having a relatively low viscosity is targeted, there is also a problem that the effect of preventing dripping is reduced. As for the method of blowing air to the tip of the injection nozzle as in the method described in Patent Document 1, if the temperature of the resin is sufficiently lowered, the viscosity increases, and therefore, dripping can be prevented to some extent. However, if the time of blowing air is short, the viscosity of the resin is not sufficiently increased, and dripping occurs. Further, the resin adjacent to the metal part of the injection nozzle is cooled relatively quickly, but the resin away from the metal part, that is, the resin in the center part of the flow path is hardly cooled. In order to lower the temperature of the resin in the central portion so that the viscosity becomes sufficiently large, it takes a little time when considering the heat capacity of the resin, and the molding cycle becomes long. That is, the molding cost increases.

  An object of the present invention is to provide an injection nozzle that solves the above-described problems, and specifically, an injection nozzle that is used in a molding method in which the injection nozzle is separated from a mold for each molding cycle. Thus, an object of the present invention is to provide an injection nozzle that can reliably prevent the occurrence of dripping, does not increase the molding cycle, and is suitable for an injection nozzle for sandwich molding, but is not limited thereto.

  In order to achieve the object of the present invention, the present invention is directed to an injection nozzle in which a mold is brought into contact with and separated from a sprue every molding cycle. A partition is provided in the front end resin flow path which is a resin flow path, and gas is blown to the outer peripheral surface near the front end. The injection nozzle is provided with a heater on the outer peripheral surface.

Thus, in order to achieve the above object, the invention according to claim 1 is an injection nozzle in which a mold is brought into contact with and separated from a sprue every molding cycle, and the injection nozzle Is configured as an injection nozzle characterized in that a partition is provided in a tip resin flow path that is a resin flow path in the vicinity of the tip, and gas is blown to the outer peripheral surface in the vicinity of the tip. The
A second aspect of the present invention is the injection nozzle according to the first aspect, wherein the injection nozzle is provided with a heater on an outer peripheral surface thereof.
The invention according to claim 3 is the injection nozzle according to claim 1 or 2, wherein the injection nozzle injects the core layer resin, and the skin layer injection injects the skin layer resin. A core layer resin flow path through which the core layer resin flows, and a skin layer resin flow path through which the skin layer resin flows, the core layer resin flow path and the The skin layer resin flow path is formed as an injection nozzle for sandwich molding, characterized in that the resin flow path for the skin layer joins in the vicinity of the front end of the injection nozzle to form the front end resin flow path.
According to a fourth aspect of the present invention, in the injection nozzle according to the third aspect, the injection nozzle includes a nozzle body in which a hollow portion is formed, and an inner nozzle that is placed in the hollow portion, and the core. The layer resin flow path is formed in the inner nozzle, and the skin layer resin flow path is formed by a gap between the hollow portion and the outer peripheral surface of the inner nozzle, and the core layer resin flow path is provided with a spring. When the core layer resin injected from the core layer injection device reaches a predetermined pressure, the needle valve recedes against the spring bias and the core layer resin flow path is provided. It is configured as an injection nozzle for sandwich molding, which is opened and closed when the pressure drops.

  As described above, the present invention is an injection nozzle in which the mold is brought into contact with and separated from the sprue for each molding cycle, and the injection nozzle is a tip that is a resin flow path in the vicinity of the tip. A partition is provided in the partial resin flow path, and gas is blown to the outer peripheral surface near the tip. Since gas is blown to the outer peripheral surface, the viscosity is increased by cooling the resin in the vicinity of the tip of the injection nozzle. Since the partition is provided at this time, the heat of the resin is conducted to the metal part of the injection nozzle through the partition, and the heat near the center of the resin flow path can be efficiently conducted to the outside. The effect of cooling becomes higher. As a result, the resin is efficiently cooled and the viscosity becomes sufficiently high. Moreover, the sectional area of the tip resin flow path is substantially halved by the partition, and there is an effect that the flow resistance is slightly increased although it is only the length of the partition. The injection nozzle according to the present invention can reliably prevent dripping by increasing the viscosity of the resin by cooling and increasing the flow resistance by partitioning. Another advantage is that the cooling effect is enhanced by the heat conduction effect of the partition. That is, since the cooling time is shortened, the molding cycle can be shortened and the molding cost can be reduced. According to another invention, the injection nozzle is provided with a heater on its outer peripheral surface. In this way, the cooled resin can be easily heated in preparation for the next injection. According to still another invention, the injection nozzle is connected to the core layer injection device for injecting the core layer resin and the skin layer injection device for injecting the skin layer resin, and the core layer resin flows inside. A core layer resin flow path; and a skin layer resin flow path through which the skin layer resin flows. The core layer resin flow path and the skin layer resin flow path are merged in the vicinity of the tip of the injection nozzle. It is configured as an injection nozzle for sandwich molding, which is a partial resin flow path. Such an injection nozzle for sandwich molding is difficult to adopt a shut-off valve composed of a needle valve, and is difficult to prevent dripping. However, according to the present invention, dripping can be reliably prevented. According to another invention, in the injection nozzle for sandwich molding, the injection nozzle includes a nozzle body in which a hollow portion is formed and an inner nozzle that is placed in the hollow portion, and the resin flow path for the core layer is an inner nozzle. The skin layer resin flow path is formed by a gap between the hollow portion and the outer peripheral surface of the inner nozzle, and the core layer resin flow path is provided with a needle valve with a spring bias, so that the core layer injection is formed. When the core layer resin injected from the apparatus reaches a predetermined pressure, the needle valve retreats against the spring bias to open the core layer resin flow path, and is closed when the pressure decreases. . Therefore, the core layer resin flow path can be closed by a needle valve so that the core layer resin does not flow, and the skin layer resin flow path is substantially divided by partitioning and gas blowing in the tip resin flow path. Since it is possible to prevent the resin for the skin layer from flowing, it is possible to reliably prevent dripping.

It is front sectional drawing which shows a part of injection molding machine which concerns on embodiment of this invention. BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows the injection nozzle which concerns on embodiment of this invention, (a) Front sectional drawing of the injection nozzle, The (a) is sectional drawing of the injection nozzle cut | disconnected by the XX cross section in (a).

  Embodiments of the present invention will be described. The injection nozzle 5 according to the present embodiment is a so-called sandwich molding injection nozzle, and as shown in FIG. 1, the injection molding machine 1 according to the present embodiment which is an injection molding machine for sandwich molding is used. Is provided. The injection molding machine 1 is roughly composed of first and second injection devices 2 and 3 and a mold clamping device. Although the mold clamping device is not shown in the drawing, it is constituted by, for example, a toggle type and is provided in a lateral direction. The first injection device 2 is arranged coaxially so as to be on an extension line in the axial direction of such a mold clamping device. In contrast, the second injection device 3 is disposed so as to be inclined at a predetermined angle with respect to the mold clamping device. Therefore, even if the first and second injection devices 2 and 3 are close to each other, the first and second injection devices 2 and 3 do not interfere with each other because they are arranged at a predetermined angle. Note that the second injection device 3 is slightly smaller than the first injection device 2. The connection block 6 is connected to the tip portions of the first and second injection apparatuses 2 and 3, and the injection nozzle 5 according to the present embodiment is connected to the connection block 6. Although not shown in the drawing, the first and second injection devices 2 and 3, the connection block 6 and the injection nozzle 5 are slid back and forth as a whole. As a result, the injection nozzle 5 can be brought into contact with or separated from the sprue of the mold.

  The connection block 6 and the injection nozzle 5 described in detail later can be called the injection nozzle in a broad sense by combining them together. However, the connection block 6 and the injection nozzle 5 will be described below as separate members. First and second injection devices 2 and 3 are connected to the connection block 6, and the first injection device 2 is connected to the connection block 6 by a fixing means such as a bolt (not shown). On the other hand, the nozzle part 3a at the tip of the second injection device 3 is in contact with the touch part 6a of the connection block 6 with a predetermined contact force. The second injection device 3 is connected to the connection block 6 of the injection nozzle 5 by abutting in this way. In the connection block 6, the 1st resin flow path 10 which sends the resin from the 1st injection apparatus 2 ahead, and the 2nd resin flow path 11 which sends the resin from the 2nd injection apparatus 3 ahead, Is provided. In this embodiment, as shown in detail in FIG. 2A, the second resin flow path 11 communicates with an axial core flow path 13 that aligns with the axial center of the injection nozzle 5. . On the other hand, the first resin flow path 10 is annularly expanded by a mekura plug 14 provided so as to prevent this flow path, and the first resin flow path 10 is formed in an annular flow path 15 formed concentrically with the axial core flow path 13. Communicate. Although the structure is not described in detail in the first and second resin flow paths 10 and 11, backflow prevention valves 16 and 17 are provided so that the resin does not flow back to the first and second injection devices 2 and 3. Yes.

  As shown in FIG. 2A, the injection nozzle 5 includes a nozzle body 19 that is formed in a hollow shape, and an inner nozzle 20 that is placed in the hollow portion. The hollow portion of the nozzle body 19 is reduced in diameter in the front to form a small-diameter opening. The inner diameter of the hollow portion of the nozzle body 19 is larger than the outer diameter of the inner nozzle 20, and an annular predetermined gap is formed between the inner peripheral surface of the hollow portion and the outer peripheral surface of the inner nozzle 20. This annular gap constitutes a skin layer resin flow path 24 in which the resin for forming the skin layer, that is, the skin layer resin flows. The skin layer resin flow path 24 communicates with the annular flow path 15 and the first resin flow path 10. The first injection device 2 is an injection device for injecting skin layer resin, and the skin layer resin injected from the first injection device 2 flows through the skin layer resin flow path 24 of the injection nozzle 5. It is injected from the opening, that is, the tip. The resin flow path in the vicinity of the front end portion of the injection nozzle 5 through which the skin layer resin is injected is referred to as a front end resin flow path 22 in this specification, and a structure peculiar to the present invention is provided as will be described later. ing.

  The inner nozzle 20 placed in the nozzle body 19 is composed of an inner nozzle body 26 formed in a hollow shape and a torpedo 27 placed in the hollow portion. The hollow portion of the inner nozzle main body 26 has a small diameter at the rear end portion, but the diameter is increased toward the front, and a torpedo 27 is placed in the expanded diameter portion. The front of the hollow portion is reduced in diameter and opened. That is, the opening 29 is formed. The opening 29 is disposed in the vicinity of the tip resin flow path 22. The hollow portion of the inner nozzle body 26 constitutes a core layer resin flow path 30 in which a resin for forming the core layer, that is, a core layer resin flows. In the vicinity of the torpedo 27, the core layer resin flow path 30 is composed of an annular gap formed in the hollow portion of the inner nozzle body 26 and the outer peripheral surface of the torpedo 27, and merges at the opening 29. The core layer resin flow path 30 communicates with the axial flow path 13 and the second resin flow path 11. Accordingly, the second injection device 3 is an injection device for injecting the core layer resin, and the core layer resin injected from the second injection device 3 is the core layer resin flow path 30 in the inner nozzle 20. And is injected from the tip resin flow path 22 through the opening 29. The tip resin flow path 22 can also be referred to as a resin flow path where the skin layer resin flow path 24 and the core layer resin flow path 30 merge.

  In the present embodiment, the torpedo 27 is provided with a needle valve 32 so as to open and close the opening 29 of the inner nozzle 20. The needle valve 32 is placed in a hollow portion formed in the torpedo 27, and only the tip portion projects forward and faces the opening 29. The needle valve 32 is spring-biased forward by a spring 34 placed in a hollow portion of the torpedo 27, and normally closes the opening 29 with a predetermined contact force. The tip of the needle valve 32 is a tapered pressure receiving surface 35. Therefore, when the pressure of the resin in the core layer resin flow path 30 increases, the pressure acts on the pressure receiving surface 35 and the needle valve 32 moves backward against the spring bias, as shown in FIG. As shown, the opening 29 is opened and the core layer resin is injected via the tip resin flow path 22.

  The tip resin flow path 22 is provided with a structure specific to the injection nozzle 5 according to the present embodiment. That is, the front end resin flow path 22 is provided with a partition 23. As shown in FIG. 2A, the partition 23 divides the front end resin flow path 22 in half, and the front end resin flow path 22 is substantially 2 having a cross-sectional area of 1/2. It is divided into two channels. The partition 23 is formed integrally with the nozzle body 19 by welding or the like, and the heat of the resin in the tip resin passage 22 is efficiently conducted to the nozzle body 19 through the partition 23.

  An air nozzle 25 that blows cooling air onto the outer peripheral surface is provided at the tip of the injection nozzle 5 where the tip resin flow path 22 is formed. The air nozzle 25 is connected to an air supply device 28, and when the air supply device 28 is driven, air is ejected vigorously from the air nozzle 25 so that the tip of the injection nozzle 5 can be cooled. Such an injection nozzle 5 is provided with a heater 33 for heating the injection nozzle 5.

  Although the clamping device is not shown in the figure. In this embodiment, two sets of molds are provided. The mold clamping device is provided with a slide mechanism for sliding the mold, and these two sets of molds are slid alternately between a mold clamping position and a retracted position. Although not described in detail, the mold according to the present embodiment is provided with a lock mechanism so that the mold can be locked in a closed state. FIG. 1 shows a part of such a mold, that is, a fixed mold 37 constituting a predetermined set of molds.

  A method of molding by the injection molding machine 1 according to the present embodiment configured as above will be described. First, a predetermined set of molds is slid to the mold clamping position. The mold clamping device is driven to clamp the mold. The whole composed of the first and second injection devices 2 and 3, the connection block 6 and the injection nozzle 5, hereinafter referred to simply as the entire injection device, is driven forward to drive the injection nozzle 5 to this one set. It is made to contact | abut to the sprue of the fixed side metal mold | die 37 which comprises the metal mold | die. In the first injection device 2, the skin layer resin is weighed. In the second injection device 3, a physical foaming agent such as an inert gas or a chemical foaming agent is added to the resin, and the core layer resin is weighed. First, the first injection device 2 is driven to inject the skin layer resin by a predetermined amount. The skin layer resin flows through the first resin flow path 10, the annular flow path 15, and the skin layer resin flow path 24, and is injected through the front end resin flow path 22. As a result, a predetermined amount is filled into the cavity of the mold. At this time, the needle valve 32 closes the opening 29 of the inner nozzle 20. Next, the first injection device 2 is stopped and the second injection device 3 is driven to inject the core layer resin. Then, the pressure of the core layer resin acts on the pressure receiving surface 35, the needle valve 32 moves backward, and the opening 29 opens. The core layer resin flows through the second resin flow path 11, the axial core flow path 13, and the core layer resin flow path 30 and is injected through the tip resin flow path 22. Since the core layer resin is filled in such a manner that the already injected skin layer resin is spread from the inside in the cavity, the skin layer is formed from the skin layer resin, and the core layer is formed from the core layer resin. It is formed. The core layer resin is foamed in the core layer. When the injection is completed, the second injection device 3 is stopped. Then, the resin pressure in the core layer resin flow path 30 in the inner nozzle 20 is slightly reduced, and the needle valve 32 closes the opening 29 by the spring bias. By closing, the pressure of the core layer resin does not drop any more in the injection nozzle 5, and foaming in the injection nozzle 5 is suppressed.

  The air supply device 28 is driven to blow air from the air nozzle 25 onto the tip of the injection nozzle 5. As a result, the resin in the tip resin flow path 22 is cooled, but the whole is cooled efficiently and in a short time by the partition 23. By cooling, the viscosity of the resin in the tip resin flow path 22 increases. The injection device is retracted and the injection nozzle 5 is separated from the fixed mold 37. Even if the injection nozzle 5 is separated, the resin does not drip from the injection nozzle 5. In other words, no rape occurs. The reason why the rape does not occur is mainly due to an increase in the viscosity of the resin accompanying a decrease in temperature, which increases the flow resistance. However, there is also an effect of increasing the flow resistance due to the partition 23 dividing the tip resin flow path 22 into flow paths having a substantially half cross-sectional area. That is, the partition 23 slightly increases the flow resistance of the resin by the length in the flow direction.

  A set of molds injected with resin is locked in a closed state, and the mold clamping device is driven to open the mold. This set of molds is maintained in a closed state. In the mold clamping device, the slide mechanism is driven to slide one set of molds to the retracted position and the other set of molds to the mold clamped position. The mold clamping device is driven to clamp another set of molds. The injection device is driven forward to bring the injection nozzle 5 into contact with the mold sprue. In preparation for injection, the heater 33 is heated to increase the temperature of the resin in the tip resin flow path 22 and reduce the viscosity. At this time, since the efficiency of heat conduction is high by the partition 23, the temperature of the resin in the tip resin flow path 22 quickly rises and the viscosity becomes small. In parallel, the resin for skin layer and the resin for core layer are weighed in the first and second injection devices 2 and 3. As described above, the resin for the skin layer and the resin for the core layer are injected in this order. As described above, air is blown from the air nozzle 25 to the tip of the injection nozzle 5 to separate the injection nozzle 5 from the mold. Hanatare does not occur. Unlock the set of molds that were previously injected with resin. Then, another set of molds injected with the resin is locked in a closed state. When the mold clamping device is driven in this state to open the mold, a set of molds is opened to obtain a molded product. The other set of molds is maintained in a closed state. The slide mechanism is driven to slide the other set of molds to the retracted position and the set of molds to the clamped position. Thereafter, sandwich molding is performed in the same manner.

  The injection nozzle 5 according to the present embodiment can be variously modified. For example, the partition 23 can be changed, and a plurality of partitions may be provided instead of fixing one. Further, the partition 23 may have a cross shape in cross section. In this specification, the injection nozzle 5 for sandwich molding has been described as an object, but a general injection nozzle that injects a single type of resin may also be an object. Even in this case, it is only necessary to provide a partition in the resin flow path in the vicinity of the tip of the injection nozzle, that is, the tip resin flow path, so that cooling air can be blown to the tip of the injection nozzle. Furthermore, in the present embodiment, the gas blown to the tip of the injection nozzle has been described as air, but other gases such as carbon dioxide and nitrogen may be used.

DESCRIPTION OF SYMBOLS 1 Injection molding machine 2 1st injection apparatus 3 2nd injection apparatus 5 Injection nozzle 6 Connection block 19 Nozzle main body 20 Inner nozzle 22 Tip part resin flow path 23 Partition 24 Skin layer resin flow path 25 Air nozzle 26 Inner nozzle main body 27 Torpedo 28 Air supply device 29 Opening 30 Core layer resin flow path 32 Needle valve 33 Heater 34 Spring 35 Pressure receiving surface 37 Fixing die

Claims (4)

  An injection nozzle in which the mold is brought into contact with and separated from the sprue at each molding cycle, and the injection nozzle is divided into a resin flow path at the front end which is a resin flow path near the front end. An injection nozzle characterized in that gas is blown to the outer peripheral surface near the tip.   The injection nozzle according to claim 1, wherein a heater is provided on an outer peripheral surface of the injection nozzle.   3. The injection nozzle according to claim 1, wherein the injection nozzle is connected to a core layer injection device for injecting a core layer resin and a skin layer injection device for injecting a skin layer resin. A core layer resin flow path through which the core layer resin flows; and a skin layer resin flow path through which the skin layer resin flows, wherein the core layer resin flow path and the skin layer resin flow path are injected. An injection nozzle for sandwich molding, characterized in that it joins in the vicinity of the tip portion of the nozzle to form the tip portion resin flow path.   The injection nozzle according to claim 3, wherein the injection nozzle includes a nozzle body in which a hollow portion is formed, and an inner nozzle that is placed in the hollow portion, and the resin flow path for the core layer is the inner nozzle. The skin layer resin flow path is formed by a gap between the hollow portion and the outer peripheral surface of the inner nozzle, and the core layer resin flow path is provided with a needle valve by spring biasing, When the core layer resin injected from the core layer injection device reaches a predetermined pressure, the needle valve retreats against the spring bias to open the core layer resin flow path, and closes when the pressure decreases. An injection nozzle for sandwich molding, characterized in that

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