Gate structure of mold with built-in hot runner and mold with built-in hot runner

Abstract

To provide: a gate structure of a mold having a built-in hot runner, which can prevent weld lines and resin burning caused by collision of resin material with a valve pin and can reduce pressure loss of resin supply; a mold having a built-in hot runner; and an injection molding machine.SOLUTION: A gate structure 5 of a mold having a built-in hot runner has: a probe 21 that extends along a Y direction, is hollow, has no movable objects within its hollow interior 1c, and causes a resin material 6 to flow along the Y direction; a gate 22 arranged near an end of the probe 21 for discharging the resin material 6 out of the probe 21 parallel to the Y direction; an open / close part 23 capable of switching between discharging and shutting of the resin material 6 to the outside by opening and closing the gate 22. The open / close part 23 has: a shutter member 24 capable of switching between an open state for the gate 22 to open and a closed state for the gate to close; and drive means 25 for driving the shutter member 24 into between the open state and the closed state.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a gate structure of an injection mold with an in-built hot runner and an injection mold with an in-built hot runner.

Background Art

[0002] Plastic injection molding technology is used as a manufacturing means and a shaping means for products and parts in various fields of industry, and has been extended to fields that require high precision. In such injection molding, the mold plays an important role together with the molding machine.

[0003] In recent years, various attempts have been made in the field of injection molding in order to use resources more effectively, such as resource conservation and recycling. Among them, a molding method using a hot runner system that heats the resin flow path has been widely adopted. The hot runner system is also called a runnerless system. In hot runner molding (hereinafter also referred to as "hot runner molding"), the flow path for injecting molten resin into the mold is located inside the fixed mold for injection molding (injection mold with an in-built hot runner), and is heated so that the molten state of the resin is maintained. Then, in hot runner molding, the heated molten resin is directly injected from the discharge port (gate) on the fixed mold side into the space (inside the mold) between the fixed mold and the movable mold. Inside the fixed mold, in the sprue flow path and the runner flow path, since the sprue and the runner are in a molten state due to heating even after resin injection, solid sprues and runners, which were generated secondarily in conventional molding, are not generated (for example, Patent Document 1). Hot runner molding in which sprues and runners are not generated is advantageous from the viewpoints of resource conservation and cost reduction.

Prior Art Documents

Patent Documents

[0004] [[ID=z7]]

Patent Document 1

Summary of the Invention

[0005] In conventional hot runner molding, a valve pin is placed inside a hollow probe through which the resin material flows, and the gate is opened and closed by the up-and-down movement of this valve pin. The resin material is typically supplied to the probe from outside via a manifold, either laterally or diagonally.

[0006] However, with conventional resin material supply methods, the resin material supplied into the probe collides with the valve pin, branches off at the valve pin, and flows around it as it heads towards the gate. The resin material that collides with the valve pin, branches off, and then rejoins behind it may create a weld line at that point.

[0007] Near the point where the branched resin material merges on the back of the valve pin, the flow velocity of the resin material slows down, and in some cases, this can lead to situations where the resin material stagnates. Such situations can result in superimposed thermal history, which can cause the resin to burn. Furthermore, if the supplied resin material collides with the valve pin, it can also cause pressure loss in the resin supply.

[0008] The present invention has been made in view of the above circumstances, and its exemplary objective is to provide a gate structure for a mold with a built-in hot runner and a mold with a built-in hot runner that can prevent the occurrence of weld lines and resin burning caused by the collision of resin material with the valve pin, and reduce pressure loss in resin supply. [Means for solving the problem]

[0009] To solve the above problems, the gate structure of a mold with a built-in hot runner, as an exemplary aspect of the present invention, has the following configuration.

[0010] A resin channel that extends along a predetermined direction, is hollow, has no movable parts inside its hollow interior, and allows a resin material to flow along the predetermined direction, A gate, which is an outlet located near the end of the resin channel, discharges the resin material from the resin channel to the outside in a direction parallel to the predetermined direction, The device has an opening / closing mechanism that allows switching between discharging the resin material to the outside and blocking it by opening and closing the gate, The opening and closing part is, A shutter member that can be switched between an open state in which the gate is opened and a closed state in which it is closed, A gate structure for a mold with a built-in hot runner, comprising a driving means for driving the shutter member to the open state and the closed state.

[0011] Another exemplary aspect of the present invention is a mold with a built-in hot runner, which comprises the gate structure of the mold with a built-in hot runner described above.

[0012] Further objects or other features of the present invention will be revealed by preferred embodiments described below with reference to the accompanying drawings. [Effects of the Invention]

[0013] According to the present invention, it is possible to prevent the occurrence of weld lines and resin burning caused by the collision of resin material with the valve pin, and to reduce pressure loss in resin supply. [Brief explanation of the drawing]

[0014] [Figure 1] This is a schematic diagram of a mold with a built-in hot runner used in an injection molding machine according to an embodiment of the present invention. [Figure 2] Figure 1 is a schematic diagram showing a magnified view of the mold with a built-in hot runner and its surroundings. [Figure 3] Figure 2 shows a cross-sectional view of the gate structure near the gate, where (a) shows the gate in the open state and (b) shows the gate in the closed state. [Figure 4] Figure 3 is an external view of the shutter component. [Figure 5] This is a schematic diagram of a gate structure according to a modified example of the present invention.

Best Mode for Carrying Out the Invention

[0015] [Embodiment] <Injection molding machine 1> Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram of a mold with an integrated hot runner used in the injection molding machine 1 according to the embodiment. The injection molding machine 1 is for performing hot runner molding. The injection molding machine 1 has a press device 2 and is configured to be able to attach a fixed mold (mold with an integrated hot runner) 3 and a movable mold 4.

[0016] The movable mold 4 is movable relative to the fixed mold 3 by the press device 2. In a state where the movable mold 4 is moved so as to be in close contact with the fixed mold 3 for mold clamping, a resin material is discharged into a gap 10 (see FIG. 1) formed in both molds, and resin molding according to the shape of the gap 10 is performed. The press device 2 is composed of an actuator such as a hydraulic cylinder or a servo motor, and performs mold clamping with a press pressure of several tens of tons to several hundreds of tons.

[0017] Regarding other components of the injection molding machine, such as a resin material tank, etc., since they are well-known, illustration and description are omitted. Also, regarding the process of resin molding in hot runner molding, although the part related to the present invention will be described below, the other parts are well-known, so the description is omitted.

[0018] Figure 2 is a schematic configuration diagram showing the fixed mold 3 attached to the injection molding machine 1 and its surroundings. Figure 2 shows the gate structure 5 and the fixed mold 3 attached to the injection molding machine 1. The supply port 1a of the injection molding machine 1 is joined to the fixed mold 3 via the bushing 1b. The resin material 6 supplied through the supply port 1a from a resin material tank (not shown) on the injection molding machine 1 side reaches the fixed mold 3, flows through the hollow interior 7a in the manifold 7, and then flows into the gate structure 5. The resin material 6 that has flowed through the gate structure 5 is injected (discharged) from the gate (discharge port) 22 into the gap 10 formed by the fixed mold 3 and the movable mold 4. In this specification, since injection molding is being described, "discharge" and "injection" are used synonymously for simplicity.

[0019] <fixed mold 3> The fixed mold 3 forms the gap 10 for the resin molded product by being clamped with the movable mold 4, and is the mold on the side attached to the injection molding machine 1 by the press device 2, that is, the side that is not moved by the press device 2. The fixed mold 3 is configured to have, for example, a mounting plate 11, a spacer block 12, a back plate 13, and a cavity plate 14.

[0020] A hollow bushing 1b is attached to the mounting plate 11, and the resin material 6 supplied from the supply port 1a flows into the hollow interior 1c of the bushing 1b. The manifold 7 is disposed within the spacer block 12. A hollow interior 7a for flowing the resin material 6 is formed within the manifold 7, and the hollow interior 7a communicates with the hollow interior 1c of the bushing 1b. The gate structure 5 is attached in connection with the manifold 7. The probe (resin flow path) 21 of the gate structure 5 is hollow, and its hollow interior 21a communicates with the hollow interior 7a of the manifold 7. Thus, the hollow interiors 1c, 7a, and 21a communicate with each other to form the flow path F for the resin material 6, and the resin material 6 supplied from the supply port 1a of the injection molding machine 1 is configured to be injectable into the gap 10.

[0021] <gate structure 5> The gate structure 5 is used in a fixed mold 3 as a mold with a built-in hot runner, and is attached to the fixed mold 3 or injection molding machine 1. It has the function of switching between injecting and blocking the resin material 6 toward the void 10. The gate structure 5 is generally composed of a probe 21, a gate 22, and an opening / closing part 23.

[0022] The probe 21 is hollow and does not have any movable parts such as valve pins inside its hollow interior 21a. The probe 21 is positioned to extend in the Y direction (a predetermined direction) in Figure 2, and the resin material 6 flowing through its hollow interior 21a also flows along the Y direction. The Y direction is shown as the vertical direction in Figure 2, and specifically, it is the direction in which the resin material 6 is injected from the gate 22. The Y direction may also be parallel to the direction in which the movable mold 4 is moved by the press device 2.

[0023] The resin material 6 flows from the flow path F on the manifold 7 side to the flow path F on the probe 21 side. In conventional valve systems, the flow direction of the resin material 6 is changed, but in this embodiment, the flow direction of the resin material 6 does not change within the hollow interior 21a of the probe 21. The resin material 6 can flow into the hollow interior 21a from approximately the rearmost end (approximately the uppermost part) of the probe 21, eliminating the need to supply the resin material 6 to the hollow interior 21a laterally or diagonally from the middle of the probe 21's extension direction. This results in a smoother flow of the resin material 6 and reduces pressure loss in the flow path. Since there are no movable parts in the hollow interior 21a of the probe 21, the resin material 6 does not collide with movable parts, preventing the occurrence of weld lines and resin burning due to reduced flow velocity caused by such flow conditions.

[0024] Furthermore, in the gate structure 5 of this embodiment, since there is no need to arrange movable parts such as valve pins inside the hollow interior 21a, the thickness of the mounting plate 11, which previously required a certain thickness for driving the valve pins, can be reduced, contributing to the overall miniaturization of the fixed mold 3. Also, since there is no need to arrange valve pins, there is no need to form an opening for valve pins inside the hollow interior 7a of the manifold 7.

[0025] Figure 3 is a cross-sectional view of the gate structure 5 near the gate 22. The gate 22 is located near the end of the probe 21 and is an outlet that discharges the resin material 6 from the hollow interior 21a of the probe 21 to the outside of the probe 21 in a direction parallel to the Y direction. By injecting the resin material 6 from the gate 22 into the gap 10 formed by the fixed mold 3 and the movable mold 4, a resin molded product can be manufactured that conforms to the shape of the gap 10.

[0026] The gate 22 is typically cylindrical in shape, and its hollow interior 22a communicates with the hollow interior 21a of the probe 21. The hollow interior 22a of the gate 22 typically has a roughly circular cross-sectional shape. In this embodiment, the gate 22 can be switched between an open state (ejection-ready state, see Figure 3(a)) and a closed state (blocked state, see Figure 3(b)) by inserting and removing two shutter members 24, which will be described later, into its hollow interior 22a.

[0027] The opening / closing section 23 is composed of a shutter member 24 and a driving means 25. The shutter member 24 achieves a closed state by being inserted into the hollow interior 22a of the gate 22, thereby closing the gate 22. The shutter member 24 also achieves an open state by being withdrawn from the hollow interior 22a of the gate 22, thereby opening the gate 22.

[0028] In this embodiment, two shutter members are used, but there is no limit to the number; one or three or more may be used. If there are multiple shutter members, they cooperate to be inserted into the hollow interior 22a to achieve the closed state.

[0029] The driving means 25 drives the shutter member 24 to an open state and a closed state, and actuators such as a motor, air cylinder, or hydraulic cylinder can be applied. In this embodiment, the driving means 25 can drive the shutter member 24 in a direction parallel to the Y direction, and the shutter member 24 is closed when driven in the flow direction of the resin material 6, i.e., downstream, and downward in Figure 3. The shutter member 24 is open when driven in the opposite direction to the flow direction of the resin material 6, i.e., upstream, and upward in Figure 3.

[0030] In this embodiment, the gate mechanism 5 further includes a link member 26, and the shutter member 24 is connected to the drive means 25 via the link member 26. The two shutter members 24 move in the Y direction along a guide portion 27 which has a roughly V-shape that narrows downstream and widens upstream. As a result, the two shutter members 24 are inserted into the hollow interior 22a of the gate 22 while moving closer to each other as they are driven by the drive means 25 toward the flow direction (downstream), achieving a closed state. As the two shutter members 24 are driven by the drive means 25 toward the opposite direction of flow (upstream), they are withdrawn from the hollow interior 22a of the gate 22 while moving further apart from each other, achieving an open state.

[0031] Since the two shutter members 24 move in the Y direction along the guide portion 27 to move closer to and further apart from each other, the shutter members 24 may have a shape that extends diagonally along the roughly V-shape exhibited by the guide portion 27. In that case, the hollow interior 22a may have a conical cross-section or a frustoconical cross-section that widens towards the upstream and narrows towards the downstream in order to achieve a closed state by the two diagonally extending shutter members 24.

[0032] Furthermore, the drive means 25 moves the link member 26 along the Y direction, but the link member 26 may be connected to the drive means 25 by a pin 28, and the link member 26 may be rotatable around the pin 28 (within the plane including the plane of paper in Figure 3). This may allow the shutter member 24 coupled to the link member 26 to move in a V-shape along the guide portion 27. Also, the pin 28, which is the connection between the drive means 25 and the link member 26, may be slidable in the left-right direction, i.e., in a direction perpendicular to the Y direction, in the radial direction of the circular cross-section of the gate 22.

[0033] Furthermore, it is preferable that the shutter member 24 has a tip shape that does not protrude from the gate 22 even when closed (see Figure 4). In this embodiment, the tips of the two shutter members 24 each form a tip surface 24a that is cut at an angle, so that when closed, the outer surface of the gate 22 and the tip surface 24a are flush.

[0034] Furthermore, in the closed state, the opposing surfaces 24b of the two shutter members 24 are cut to form flat surfaces so that they are in close contact with each other. Of course, as long as mutual contact is ensured, the surfaces do not necessarily have to be flat; one may be convex and the other concave, and they may interlock when closed. The shapes of these tip surfaces 24a and opposing surfaces 24b are adjusted as appropriate according to the mounting angle of the shutter member 24 with respect to the gate 22, the direction of movement of the shutter member 24 by the driving means 25 and link members 26, the number of shutter members 24, etc.

[0035] In this way, by eliminating the valve pin in an injection molding machine for hot runners and adopting the gate structure described in this embodiment, the resin material is allowed to flow along the flow direction from approximately the uppermost part of the probe, thereby preventing the occurrence of various defects such as weld lines and resin burning caused by the collision of the resin material with the valve pin, and improving the quality of the resin molded product.

[0036] Eliminating the valve pin reduces pressure loss during resin supply, thereby reducing the burden on the power source for resin supply and contributing to the overall miniaturization and cost reduction of the device. Eliminating the valve pin also eliminates the need to form an opening for the valve pin in the manifold, and eliminates the need to install the valve pin drive unit on the mounting plate 11, allowing the mounting plate to be made thinner and the size of the fixed mold to be reduced.

[0037] The number of shutter components can be one or multiple, but by using multiple shutter components, the same performance can be achieved even with a shorter operating distance for each shutter component. Since relatively low-output and low-torque drive mechanisms can be applied, the degree of freedom in selecting the drive mechanism is increased, contributing to miniaturization and cost reduction of the device. In addition, since the operating distance of each shutter component can be shortened compared to the case with a single shutter component, the operating speed of each shutter component can be reduced to achieve the same operating time. This also contributes to increased freedom in selecting the drive mechanism by enabling the application of relatively low-output and low-torque drive mechanisms, and also contributes to improved reliability of operation.

[0038] [Differentiation] Figure 5 is a schematic diagram of a modified gate structure 5. In this modified example, components similar to those in the embodiment are denoted by the same reference numerals, and their descriptions are omitted. In this modified example, the driving means 25 is configured to include a rod 25a inserted from the side of the fixed mold 3, a bracket 25b that can move along the Y direction by inserting and removing the rod 25a, and an actuator 25c that drives the rod 25a to be insertable and removable in the lateral direction (i.e., in a direction perpendicular to the Y direction in the plane of Figure 5). The end of the bracket 25b is connected by a link member 26 and a pin 28.

[0039] By inserting and removing the rod 25a using the actuator 25c, the bracket 25b can be moved up and down along the Y direction, which in turn causes the shutter member 24 to move via the link member 26, thereby enabling the gate 22 to be in an open state or a closed state.

[0040] Although preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and various modifications and changes are possible within the scope of its essence. For example, the present invention includes the following aspects.

[0041] (Purpose 1) A resin channel that extends along a predetermined direction, is hollow, has no movable parts inside its hollow interior, and allows a resin material to flow along the predetermined direction, A gate, which is an outlet located near the end of the resin channel, discharges the resin material from the resin channel to the outside in a direction parallel to the predetermined direction, The device has an opening / closing mechanism that allows switching between discharging the resin material to the outside and blocking it by opening and closing the gate, The opening and closing part is, A shutter member that can be switched between an open state in which the gate is opened and a closed state in which it is closed, A gate structure for a mold with a built-in hot runner, comprising a driving means for driving the shutter member to the open state and the closed state.

[0042] (Purpose 2) The aforementioned driving means is The shutter member can be driven along a direction parallel to the predetermined direction, When the shutter member is driven in the direction of the flow of the resin material, the shutter member achieves the closed state. The shutter member may achieve the open state when driven in the direction opposite to the flow direction.

[0043] (Purpose 3) The shutter members are multiple, As the plurality of shutter members are driven in the flow direction by the driving means, the plurality of shutter members are inserted into the gate while moving closer to each other. As the plurality of shutter members are driven in the opposite direction by the driving means, the plurality of shutter members may separate from each other and be removed from the gate.

[0044] (Purpose 4) The plurality of shutter members are in close contact with each other in the closed state to achieve the closed state, In the closed state, at least a portion of the envelope shape that encloses the outer shapes of the plurality of shutter members coincides with the inner surface shape of the gate. In the closed state, the plurality of shutter members may be shaped so as not to protrude outward from the gate.

[0045] (Purpose 5) A hot runner-integrated mold equipped with the gate structure of the hot runner-integrated mold described above.

[0046] (Purpose 6) An injection molding machine equipped with the gate structure of the hot runner-integrated mold described above. [Explanation of Symbols]

[0047] F: Flow channel Y: predetermined direction 1: Injection molding machine 1a: Supply port 1b: Bush 1c: Hollow inside 2: Pressing device 3: Fixed mold (mold with built-in hot runner) 4: Movable mold 5: Gate structure 6: Resin materials 7: Manifold 7a:Hollow inside 10:Void 11: Mounting plate 12: Spacer Block 13: Backplate 14: Cavity Plate 21: Probe (resin channel) 21a:Hollow inside 22: Gate (discharge port) 22a: Hollow inside 23: Opening / Closing Section 24: Shutter component 24a: Tip 24b: Opposite surface 25: Driving means 25a: Rod 25b: Bracket 25c: Actuator 26: Link member 27: Guide Department 28: Pin

Claims

1. A resin channel that extends along a predetermined direction, is hollow, has no movable parts inside its hollow interior, and allows a resin material to flow along the predetermined direction, A gate, which is an outlet located near the end of the resin channel, discharges the resin material from the resin channel to the outside in a direction parallel to the predetermined direction, The device has an opening / closing mechanism that allows switching between discharging the resin material to the outside and blocking it by opening and closing the gate, The opening and closing part is, A shutter member that can be switched between an open state in which the gate is opened and a closed state in which it is closed, The shutter member has a driving means for driving it to the open state and the closed state, The aforementioned driving means is The shutter member can be driven along a direction parallel to the predetermined direction, When the shutter member is driven in the direction of the flow of the resin material, the shutter member achieves the closed state. When the shutter member is driven in the direction opposite to the flow direction, the shutter member achieves the open state. The shutter members are multiple, As the plurality of shutter members are driven in the flow direction by the driving means, the plurality of shutter members are inserted into the gate while moving closer to each other. As the plurality of shutter members are driven in the opposite direction by the driving means, the plurality of shutter members move apart from each other and are removed from the gate. The plurality of shutter members are in close contact with each other in the closed state to achieve the closed state, In the closed state, at least a portion of the envelope shape that encloses the outer shapes of the plurality of shutter members coincides with the inner surface shape of the gate. In the closed state, the plurality of shutter members are shaped so that they do not protrude from the gate to the outside, in a gate structure for a mold with a built-in hot runner.

2. A hot runner built-in mold comprising the gate structure of the hot runner built-in mold according to Claim 1.

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