JP2017019120A - Injection nozzle for sandwich molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an injection nozzle for sandwich molding capable of using a resin foam for a core layer, and capable of stably performing sandwich molding.SOLUTION: The invention relates to an injection nozzle (5) for sandwich molding in which, an injection device (3) for a core layer and an injection device (2) for a skin layer are connected. The injection nozzle (5) comprises: a nozzle body (19) in which a hollow part is formed; and an inner nozzle (20) which is stored in the hollow part. The resin for a core layer flows a resin channel (30) for a core layer which is disposed on the inner nozzle (20), and the resin for a skin layer flows a resin channel (24) for a skin layer which is formed of a gap between the hollow part and an outer peripheral face of the inner nozzle (20). The resin channel (30) for a core layer has a needle valve (32) for closing an opening part (29) by spring energization. When pressure of the resin for a core layer injected from the injection device (3) for a core layer becomes prescribed pressure, the needle valve (32) retreats against to the spring energization, and the resin channel (30) for a core layer is opened.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an injection nozzle used in so-called sandwich molding, in which a resin is injected from two injection devices to obtain a molded product composed of a core layer and a skin layer.

  So-called sandwich molding is known in which two types of resins are injected to obtain a molded product composed of a core layer and a skin layer. Generally, an injection molding machine is composed of a mold clamping device for clamping a mold, an injection device for injecting an injection material into a mold that has been clamped, a protruding device for projecting a molded product from the mold, etc. In an injection molding machine that performs sandwich molding, two injection devices are provided. These two injection devices are connected to a common injection nozzle so that resin can be injected from the common injection nozzle into the mold. In such an injection molding machine, first, one injection device is driven to inject a predetermined amount of the resin for the skin layer, and then the other injection device is driven to inject the resin for the core layer. If necessary, finally, one of the injection devices is driven to inject the resin for the skin layer. When the resin is injected in this order, the first injected resin for the skin layer is brought into contact with the inner wall surface of the cavity of the mold and quickly solidified, and the injected resin for the core layer is then injected into the cavity. It will be devoted to the center. Thereby, a molded product composed of the core layer and the skin layer can be obtained.

  When a molded product is obtained by sandwich molding, for example, a new resin is used for the skin layer that affects the aesthetics of the molded product, and a recycled resin is used for the core layer to reduce the manufacturing cost. Or an environmentally friendly molded product can be obtained. Further, the molded product can be made lighter by using foamed resin. Foamed resin has an excellent property that it is lightweight while being strong, but the aesthetics are impaired by bubbles. Therefore, sandwich molding is performed so that the core layer is made of foamed resin and the skin layer is made of ordinary resin. Specifically, for the core layer, a chemical foaming agent is added to the resin, or an inert gas is injected and injected. The injected resin is foamed in the cavity to obtain a core layer made of a foamed resin in which fine bubbles are formed.

Japanese Patent No. 3609808

  Various injection nozzles for sandwich molding have been proposed. For example, the applicant of the present application also proposed in Patent Document 1. The injection molding machine described in Patent Document 1 is also connected to two injection devices, the first injection device is coaxial with the injection molding machine, and the second injection device is oblique to the injection device. It is provided to become. These first and second injection devices are provided with a common injection nozzle. The injection nozzle described in Patent Document 1 is composed of a nozzle body and an inner nozzle 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 core resin can be injected from the second resin flow path. The injection nozzle described in Patent Document 1 is characterized in that the inner nozzle is selected and attached from the first and second inner nozzles having different shapes. When the first inner nozzle is provided in the nozzle body, the first injection device communicates with the first resin flow path, and the second injection device communicates with the second resin flow path. It has become. Then, the resin for skin is injected from the first injection device, and the resin for core is injected from the second injection device. On the other hand, when the second inner nozzle is provided in the nozzle body, the first injection device communicates with the second resin flow channel, and the second injection device communicates with the first resin flow channel. It comes to communicate. Then, the resin for skin is injected from the second injection device, and the resin for core is injected from the first injection device. In other words, the injection nozzle described in Patent Document 1 is obtained by replacing the injection device for injecting the skin resin and the core resin with either the first or second injection device by simply replacing the inner nozzle. You can even choose from.

  There are various types of injection nozzles for sandwich molding, and each is excellent. The injection nozzle described in Patent Document 1 is also excellent in usability because it can inject the resin for the core layer and the resin for the skin layer from either of the first and second injection devices. However, there are some problems to be solved in these conventional injection nozzles. Specifically, a problem is observed when sandwich molding is performed using a foamed resin. The foamed resin is injected into the mold and foamed in the cavity. This is because the pressure of the resin is lowered in the cavity and the chemical foaming agent or physical foaming agent is foamed. However, if the pressure of the resin decreases in the injection nozzle, foaming starts in the injection nozzle. This will cause trouble in the next injection molding. Conventional injection nozzles are not particularly considered for such problems.

  An object of the present invention is to provide an injection nozzle for sandwich molding that solves the above-described problems. Specifically, the foamed resin can be injected and the foamed resin is injected. An object of the present invention is to provide an injection nozzle for sandwich molding that can surely prevent foaming in the nozzle.

  In order to achieve the object of the present invention, the core layer injection device for injecting the core layer resin and the skin layer injection device for injecting the skin layer resin are connected. It is configured as an injection nozzle for sandwich molding. The injection nozzle is composed of a nozzle body in which a hollow portion is formed and an inner nozzle that is placed in the hollow portion, and the core layer resin has a core layer resin flow path provided in the inner nozzle. The skin layer resin is caused to flow through the skin layer resin flow path formed by the gap between the hollow portion and the outer peripheral surface of the inner nozzle. A needle valve is provided in the resin flow path for the core layer. This needle valve closes the core layer resin flow path by spring biasing, but when the core layer resin injected from the core layer injection device reaches a predetermined pressure, the needle valve resists spring biasing. Is configured so that the core layer resin flow path opens.

Thus, in order to achieve the above object, the invention according to claim 1 connects the core layer injection device for injecting the core layer resin and the skin layer injection device for injecting the skin layer resin. The injection nozzle comprises 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 layer resin flow path is configured as an injection nozzle for sandwich molding, characterized in that a valve for opening and closing the resin flow path is provided at the opening.
According to a second aspect of the present invention, in the injection nozzle according to the first 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 A 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. Configured as an injection nozzle.
According to a third aspect of the present invention, in the injection nozzle according to the first or second aspect, the valve is a needle valve configured to close the opening by a spring bias, and the core layer injection device An injection nozzle for sandwich molding, wherein the needle valve is retracted against the spring bias and the opening is opened when the core layer resin injected from the pressure reaches a predetermined pressure Configured as

  As described above, the present invention is configured as an injection nozzle in which the core layer injection device for injecting the core layer resin and the skin layer injection device for injecting the skin layer resin are connected. Yes. The injection nozzle includes 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, and the core layer resin flow path is opened and closed at its opening. A valve is provided. That is, the opening of the core layer resin flow path through which the core layer resin flows is opened and closed by the valve. Then, even when the foamed resin is used as the core layer resin, the foamed resin can be prevented from foaming in the injection nozzle by closing the core layer resin flow path. This ensures that even if the foamed resin is used as the core layer resin, sandwich molding can be performed safely. According to another invention, the injection nozzle includes a nozzle body in which a hollow portion is formed, and an inner nozzle that is put in the hollow portion, the resin flow path for the core layer is formed in the inner nozzle, and the skin layer The resin flow path is composed of a gap between the hollow portion and the outer peripheral surface of the inner nozzle. That is, the core layer resin flow path is provided at the center of the injection nozzle, and the skin layer resin flow path surrounds the outside of the core layer resin flow path. Then, when the core layer resin and the skin layer resin are injected at the same time, the core layer resin is injected into the mold in a form in which the skin layer resin is coated. When two kinds of resins are injected in such a state, the skin layer resin comes into contact with the inner wall of the cavity first, and it is guaranteed that the skin layer is formed by the skin layer resin. The core layer resin is guaranteed to remain inside the skin layer. As a result, a sandwich molded article having an excellent aesthetic appearance is surely obtained. According to still another invention, the valve comprises a needle valve that closes the opening by spring biasing, and when the core layer resin injected from the core layer injection device reaches a predetermined pressure, the spring biasing is performed. Against this, the needle valve is retracted to open the opening. That is, the needle valve is automatically opened and closed by the pressure of the resin. Since it is not necessary to provide a special valve driving device, the injection nozzle can be configured at low cost.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows a part of injection molding machine concerning embodiment of this invention, The (a) is front sectional drawing which shows the 1st, 2nd injection apparatus and an injection nozzle, The (a) is a front sectional view of an injection nozzle. FIG. BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows typically the effect | action of the injection nozzle which concerns on embodiment of this invention, (a), (b) is an injection nozzle which shows a mode that the resin for skin layers and the resin for core layers are each injected FIG. It is front sectional drawing which shows the injection nozzle which concerns on 2nd Embodiment.

  Embodiments of the present invention will be described. The injection molding machine 1 according to the present embodiment is configured as a so-called sandwich molding injection molding machine, and as shown in FIG. And a mold clamping device (not shown). The mold clamping device is constituted by, for example, a toggle type and is provided sideways, but 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. Yes. 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, they are arranged at a predetermined angle so that they do not compete with each other. Note that the second injection device 3 is slightly smaller than the first injection device 2. An injection nozzle 5 according to the present embodiment described below is connected to the tip portions of the first and second injection devices 2 and 3.

  The injection nozzle 5 according to the present embodiment includes a connection block portion 6 connected to the first and second injection devices 2 and 3 and a nozzle tip portion 8 having a structure unique to the present invention. . Only the nozzle tip 8 can be referred to as the injection nozzle, but in the following description, the connection block 6 and the nozzle tip 8 are collectively referred to as the injection nozzle 5. The first and second injection devices 2 and 3 are connected to the connection block portion 6, but the tip of the first injection device 2 is connected to the connection block portion 6 by a fixing means such as a bolt (not shown). Yes. 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 formed in the connection block part 6 with a predetermined contact force. The second injection device 3 is connected to the connection block portion 6 of the injection nozzle 5 by abutting in this way. In the connection block part 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 And are provided. In this embodiment, the second resin flow path 11 communicates with an axial core flow path 13 aligned with the axial center of the nozzle tip 8 as shown in detail in FIG. Yes. 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. 1A, the nozzle tip portion 8 is composed of 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 opened in the front, and this is an injection port 22 through which resin is injected. 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. Accordingly, in this embodiment, the first injection device 2 is an injection device for injecting the skin layer resin, and the skin layer resin injected from the first injection device 2 is the skin of the nozzle tip 8. It flows through the layer resin flow path 24 and is injected from the injection port 22.

  The inner nozzle 20 includes an inner nozzle body 26 that is formed in a hollow shape, and a torpedo 27 that is 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 injection port 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. In this embodiment, the core layer resin flow path 30 communicates with the axial core flow path 13 and the second resin flow path 11. Therefore, in this embodiment, 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 in the inner nozzle 20. It flows through the layer resin flow path 30 and is injected from the injection port 22 through the opening 29.

  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 entirely 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. Accordingly, when the pressure of the resin in the core 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.

  A molding method for obtaining a sandwich molded product having a core layer made of a foamed resin by the injection molding machine 1 according to the present embodiment will be described. As shown in FIG. 1A, the injection nozzle 5 according to the present embodiment is touched to the sprue of the fixing mold 37 attached to the mold clamping device with a predetermined contact force. 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. 2A, 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 from the injection port 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. As shown in FIG. 2A, 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 from the injection port 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. When the mold is opened after cooling and solidification, a sandwich molded product having a core layer made of a foamed resin can be obtained. In this molding method, the second injection device 3 is driven to stop the first injection device 2 when the core layer resin is injected. However, the first injection device 2 is also in parallel. By driving, the skin layer resin may be injected together with the core layer resin. Alternatively, after the second injection device 3 is stopped, the first injection device 2 may be driven to inject only a predetermined amount of the skin layer resin to complete the molding.

  The injection nozzle 5 according to the present embodiment can be variously modified. FIG. 3 shows an injection nozzle 5 'according to the second embodiment. The same members as those of the previous embodiment are denoted by the same reference numerals and description thereof is omitted. The injection nozzle 5 'according to the second embodiment is different from the previous embodiment in the connection block portion 6'. Specifically, the first resin flow path 10 communicates with the axial core flow path 13 ', and the second resin flow path 11 communicates with the annular flow path 15'. Therefore, in this embodiment, the core layer resin is injected from the first injection device 2, and the skin layer resin is injected from the second injection device 3. Other variations are possible. For example, the needle valve 32 that closes the opening 29 of the resin flow path 30 for the core layer is described as being spring-biased by a spring 34, and the needle valve 32 increases the pressure of the resin acting on the pressure receiving surface 35. I explained to open it. However, a predetermined drive mechanism that can drive the needle valve 32 from the outside may be separately provided, and the opening 29 may be opened and closed by an external operation. The skin layer resin flow path 24 and the core layer resin flow path 30 in the injection nozzle 5 can also be modified. In the present embodiment, the core layer resin flow path 30 and the skin layer resin flow path 24 are formed so as to be concentric annular flow paths, but they are not necessarily configured from annular flow paths. There is no need. In order to carry out the invention, it is sufficient that the opening 29 of the core layer resin flow path 30 is opened and closed by a valve. The shape can be freely selected.

DESCRIPTION OF SYMBOLS 1 Injection molding machine 2 1st injection apparatus 3 2nd injection apparatus 5 Injection nozzle 6 Connection block part 8 Nozzle front-end | tip part 8
DESCRIPTION OF SYMBOLS 19 Nozzle main body 20 Inner nozzle 22 Injection port 24 Skin layer resin flow path 26 Inner nozzle main body 27 Torpedo 29 Opening 30 Core layer resin flow path 32 Needle valve 34 Spring 35 Pressure receiving surface 37 Fixing die

Claims (3)

An injection nozzle configured to connect a core layer injection device for injecting a core layer resin and a skin layer injection device for injecting a skin layer resin,
The injection nozzle includes 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. An injection nozzle for sandwich molding, comprising a valve for opening and closing the valve.   2. The injection nozzle according to claim 1, 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. An injection nozzle for sandwich molding, wherein the resin flow path for skin layer is formed by a gap between the hollow portion and the outer peripheral surface of the inner nozzle.   3. The injection nozzle according to claim 1, wherein the valve is a needle valve configured to close the opening by spring bias, and the core layer resin injected from the core layer injection device is An injection nozzle for sandwich molding, wherein the needle valve is retracted against the spring bias to open the opening when a predetermined pressure is reached.

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