Hot nozzle assembly of hot runner system

Abstract

The present invention provides a hot nozzle assembly for a hot runner system, belonging to the technical field of injection molds. It solves the problem of poor product quality caused by uneven temperature of molten plastic. It includes a long tubular body, a nozzle sleeve fixedly connected to one end of the body, and a flow dividing nozzle core fixed between the two. The end of the flow dividing nozzle core away from the nozzle sleeve is provided with an inlet cavity, and the flow dividing nozzle core has a protruding portion in the inlet cavity. The flow dividing nozzle core is provided with a plurality of flow dividing holes distributed around the protruding portion. The flow dividing nozzle core at the inlet cavity sequentially includes an acceleration section and a holding section along the axial direction. The cavity wall of the inlet cavity at the acceleration section has a taper. The maximum inner diameter of the inlet cavity at the acceleration section is the same as the inner diameter of the body, and its minimum inner diameter is the same as the inner diameter of the inlet cavity at the holding section. The protruding portion is located in the inlet cavity at the holding section, and its top has a flow disturbing surface. The cross section of the flow dividing hole is generally polygonal. It has the advantages of making the temperature of molten plastic more uniform and having good product quality, etc.

Description

Technical Field

[0001] The present invention belongs to the technical field of injection molds, relates to a hot runner system, and particularly relates to a nozzle assembly of a hot runner system. Background Art

[0002] Currently, the injection molds commonly used in the injection molding industry are hot runner injection molds. Compared with ordinary molds, the plastic products injected through the hot runner system have higher quality. Among them, the hot runner system keeps the plastic in the runner and the gate in a molten state by heating. The hot runner system generally includes a nozzle assembly, a manifold plate, a temperature control box, and some other corresponding accessories. And the existing hot runner systems are specifically divided into an open hot runner system and a needle valve hot runner system according to requirements. The open hot runner system means that the outlet of the nozzle assembly is normally open. The traditional such normally open nozzle assembly usually includes a tubular body and a gate bushing fixed at one end of the body. The other end of the body is fixedly connected to the branch port of the manifold plate (the branch port is communicated with the main runner in the manifold plate), and the gate is docked with the cavity of the mold. Further, in order to ensure that the molten plastic does not block in the gate, a diverter nozzle core is generally fixed between the body and the gate bushing. The diverter nozzle core is provided with a plurality of diversion holes, so that the molten plastic is first diverted by the diverter nozzle core and then injected into the cavity of the mold.

[0003] As mentioned above, the molten plastic is kept in a molten state in the hot runner system by heating. Taking the molten plastic in the nozzle assembly as an example, the commonly used method is heat transfer, that is, a heating coil is arranged outside the body or heating wires are wound. After the heating coil or the heating wires are energized to generate heat, the heat is transferred to the molten plastic through the body. However, in practice, the temperature of the molten plastic adhering to the inner wall of the body must be higher than that of the molten plastic at other positions, and when entering each diversion hole, the molten plastic at different positions will only be mixed to a very small extent. In this way, the temperature of the molten plastic injected into the cavity of the mold is uneven, which will lead to poor quality of the produced products. Summary of the Invention

[0004] The purpose of the present invention is to solve the above problems existing in the prior art, and provides a nozzle assembly of a hot runner system, which solves the problem of poor product quality caused by uneven temperature of molten plastic.

[0005] The purpose of the present invention can be achieved by the following technical solutions:

[0006] The hot nozzle assembly of a hot runner system includes a long tubular body, a nozzle sleeve fixedly connected to one end of the body, and a manifold core fixed between the two. The end of the manifold core away from the nozzle sleeve is provided with an inlet cavity, and the manifold core has a protruding portion in the inlet cavity. The manifold core is provided with a plurality of distribution holes distributed around the protruding portion. It is characterized in that the manifold core at the inlet cavity sequentially includes an acceleration section and a holding section along the axial direction. The cavity wall of the inlet cavity at the acceleration section has a taper. The maximum inner diameter of the inlet cavity at the acceleration section is the same as the inner diameter of the body, and its minimum inner diameter is the same as the inner diameter of the inlet cavity at the holding section. The protruding portion is located in the inlet cavity at the holding section, and its top has a turbulence surface. The cross-section of the distribution hole is generally polygonal. The protruding portion has an outer taper. The turbulence surface is a circular plane. The turbulence surface is perpendicular to the central axis of the body, and the center of the turbulence surface is collinear with the central axis of the body.

[0007] Melted plastic flows from the main runner of the hot runner system into the body and flows along the body. The manifold core at the inlet cavity sequentially includes an acceleration section and a holding section along its axial direction. The cavity wall of the inlet cavity at the acceleration section has a taper. The maximum inner diameter of the inlet cavity at the acceleration section is the same as the inner diameter of the body, and its minimum inner diameter is the same as the inner diameter of the inlet cavity at the holding section. The flow cross-sectional area at the maximum inner diameter of the inlet cavity at the acceleration section is larger than the flow cross-sectional area at the minimum inner diameter of the inlet cavity at the acceleration section. In this way, the melted plastic will enter the holding section at a greater flow rate after passing through the acceleration section. At the same time, the protruding portion is located in the inlet cavity at the holding section, and its top has a turbulence surface. A part of the melted plastic that has been accelerated will directly impact on the turbulence surface after entering the holding section. Since the melted plastic that has been accelerated has greater kinetic energy, it will sputter in a wider range around after impacting on the turbulence surface and impact the remaining melted plastic. And because the turbulence surface is perpendicular to the central axis of the body and the center of the turbulence surface is collinear with the central axis of the body, it makes the melted plastic that is farthest from the inner wall of the body (the farthest from the inner wall of the body and the temperature is correspondingly the lowest) can be impacted on the turbulence surface more and sputter around to fully mix with the melted plastic at a higher temperature. Thus, to a certain extent, the flow of the melted plastic is disturbed and is in a state similar to being stirred, so that the melted plastic can be mixed once before being distributed by each distribution hole. After that, the melted plastic enters each distribution hole. The cross-section of the distribution hole is generally polygonal (here the cross-section refers to the cross-sectional shape along the direction perpendicular to the center line of the distribution hole). When the melted plastic passes through the distribution hole, the inner side walls of the distribution hole form resistance to the corrugations of the melted plastic expanding radially outward and thereby generate a reaction force on the melted plastic, thus forming a secondary turbulence stirring effect on the melted plastic in the distribution hole, that is, secondary mixing. Through the combination of these two mixings, the temperature of the melted plastic entering the mold will be more uniform and the quality of the product will be improved.

[0008] Conventionally, for the purpose of enabling sufficient mixing of the molten plastic before splitting to make the temperature more uniform, it is generally not thought of to provide an acceleration section in the inlet cavity. This is because the molten plastic after simple acceleration will only pass through each split hole faster and enter the mold, which will not only not make the temperature of the molten plastic more uniform, but may also make it more difficult for the temperature of the molten plastic to become uniform because it enters the mold faster.

[0009] In the nozzle assembly of the hot runner system described above, the split nozzle core portion is located within the nozzle sleeve. There is a heat insulation gap between the outer peripheral wall of the split nozzle core located within the nozzle sleeve and the inner wall of the nozzle sleeve. The end of the split nozzle core located within the nozzle sleeve has an annular flange, and the outlets of each split hole are located inside the annular flange.

[0010] The body, split nozzle core, and nozzle sleeve are all made of metal materials. In order to slow down heat transfer and prevent a large change in the temperature of the molten plastic, a heat insulation gap is provided between the outer peripheral wall of the split nozzle core located within the nozzle sleeve and the inner wall of the nozzle sleeve. However, in actual production, since the molten plastic is in a flowing state, when the molten plastic flows out from the outlet of the split hole, it will inevitably also flow towards the outer peripheral wall of the split nozzle core. In this way, it is easy for the molten plastic to be squeezed into the heat insulation gap. This part of the molten plastic squeezed into the heat insulation gap will solidify to a certain extent when the mold is not in use. When the mold is used again, the new molten plastic will inevitably come into contact with the old molten plastic located within the heat insulation gap, resulting in the temperature at which the new molten plastic has been evenly mixed being absorbed by this part of the molten plastic and affecting the product quality.

[0011] This nozzle assembly sets an annular flange at the end of the split nozzle core located within the nozzle sleeve, and the outlets of each split hole are located inside the annular flange. In this way, it is possible to prevent the molten plastic from being squeezed into the heat insulation gap as much as possible, so as to ensure that the temperature at which the molten plastic has been evenly mixed can be basically maintained stable to ensure the product quality.

[0012] In the nozzle assembly of the hot runner system described above, a gate is provided within the nozzle sleeve. The nozzle sleeve at the gate includes a first straight section, a first contraction section, a second straight section, and a second contraction section in sequence along the axial direction. The inner wall of the gate at the first contraction section has a taper. The maximum inner diameter of the gate at the first contraction section is the same as the inner diameter of the gate at the first straight section. The minimum inner diameter of the gate at the first contraction section is the same as the inner diameter of the gate at the second straight section. The inner wall of the gate at the second contraction section has a taper. The maximum inner diameter of the gate at the second contraction section is the same as the inner diameter of the gate at the second straight section. The annular flange is located within the first contraction section. The heat insulation gap is located between the outer peripheral wall of the split nozzle core and the inner wall of the gate at the first straight section. The inner diameter of the annular flange is between the maximum inner diameter and the minimum inner diameter of the gate at the first contraction section.

[0013] The annular convex edge is located within the first constriction section, such that after the molten plastic flows out from the distribution holes, it drips along the inner wall of the annular convex edge onto the first constriction section. Since the inner wall of the gate at the first constriction section has a taper, when the molten plastic lands on the inner wall of the gate at the first constriction section, it can directly slide downward rapidly by virtue of the taper, thereby making it more difficult for the molten plastic to squeeze into the heat insulation gap.

[0014] Furthermore, the nozzle sleeve at the gate includes an axially extending first straight section, a first constriction section, a second straight section, and a second constriction section. The inner wall of the gate at the first constriction section has a taper. The maximum inner diameter of the gate at the first constriction section is the same as the inner diameter of the gate at the first straight section. The minimum inner diameter of the gate at the first constriction section is the same as the inner diameter of the gate at the second straight section. The inner wall of the gate at the second constriction section has a taper. The maximum inner diameter of the gate at the second constriction section is the same as the inner diameter of the gate at the second straight section. The molten plastic can achieve two stages of acceleration within the gate. The first stage is mainly to prevent the molten plastic from being not easily squeezed into the heat insulation gap, and the second stage of acceleration is to increase the injection speed of the molten plastic into the cavity of the mold.

[0015] In the nozzle assembly of the above-mentioned hot runner system, the cross-section of the distribution holes is substantially regular hexagon.

[0016] Since the distances from the six inner side walls of the distribution holes to its central axis are not completely the same, the actual achieved flow disturbance effect is better.

[0017] Compared with the prior art, in the nozzle assembly of the present hot runner system, the inlet cavity of the distribution nozzle core is axially provided with an acceleration section and a holding section, and by combining with the provision of a flow disturbance surface on the top surface of the protruding portion located in the holding section, the acceleration section can accelerate the molten plastic to have a large kinetic energy. After the accelerated molten plastic enters the holding section, a part of it will directly impact on the flow disturbance surface and sputter widely around, and the splashing molten plastic will impact the remaining molten plastic. Thus, to a certain extent, the flow of the molten plastic is disturbed and is in a state similar to being stirred, so that the molten plastic can be fully mixed before being divided by each distribution hole. In this way, the temperature of the molten plastic entering the mold is more uniform, improving the quality of the product. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a cross-sectional view of the nozzle assembly of the present hot runner system.

[0019] Figure 2 is Figure 1 a partially enlarged cross-sectional view at the distribution nozzle core in

[0020] Figure 3 is a three-dimensional schematic diagram of the distribution nozzle core.

[0021] Figure 4 is a three-dimensional schematic diagram of the distribution nozzle core from another angle.

[0022] Figure 5 It is a schematic diagram when the hot nozzle assembly is connected to the manifold plate.

[0023] Figure 6 It is a schematic diagram of the flow of molten plastic in the inlet cavity.

[0024] In the figure, 1 is the body; 2 is the sprue bushing; 2a is the sprue; 2b is the first straight section; 2c is the first contraction section; 2d is the second straight section; 2e is the second contraction section; 2f is the discharge channel; 3 is the manifold nozzle core; 3a is the inlet cavity; 3b is the protruding part; 3b1 is the turbulence surface; 3c is the manifold hole; 3d is the drainage part; 3e is the acceleration section; 3f is the holding section; 3g is the annular flange; 4 is the heat insulation gap; 5 is the manifold plate; 6 is the heating coil. Detailed implementation manners

[0025] The following are specific embodiments of the present invention and in combination with the accompanying drawings, the technical solutions of the present invention are further described, but the present invention is not limited to these embodiments.

[0026] As Figure 1 、 Figure 2 and Figure 3 shown, the hot nozzle assembly of the hot runner system includes a long tubular body 1, a sprue bushing 2 fixedly connected to one end of the body 1, and a manifold nozzle core 3 fixed between the two. Among them, the body 1, the sprue bushing 2 and the manifold nozzle core 3 are all made of metal materials. The manifold nozzle core 3 is columnar. One end of the manifold nozzle core 3 away from the sprue bushing 2 is provided with an inlet cavity 3a. The manifold nozzle core 3 has a protruding part 3b in the inlet cavity 3a. The manifold nozzle core 3 is provided with a plurality of manifold holes 3c evenly distributed around the protruding part 3b. The protruding part 3b has an outer peripheral surface and its outer peripheral surface has a taper. The outer diameter of the protruding part 3b gradually increases in the direction close to the sprue bushing 2. The inlets of the respective manifold holes 3c are all communicated with the inlet cavity 3a. The outlets of the respective manifold holes 3c all penetrate through the other end of the manifold nozzle core 3. The cross-sections of the respective manifold holes 3c are approximately polygonal. In this embodiment, it is approximately regular hexagon. Here, the cross-section refers to the cross-sectional shape along the direction perpendicular to the center line of the manifold hole 3c. The manifold nozzle core 3 at the inlet cavity 3a sequentially includes an acceleration section 3e and a holding section 3f along the axial direction. The cavity wall of the inlet cavity 3a at the acceleration section 3e has a taper. The maximum inner diameter of the inlet cavity 3a at the acceleration section 3e is the same as the inner diameter of the body 1 and its minimum inner diameter is the same as the inner diameter of the inlet cavity 3a at the holding section 3f. The protruding part 3b is located in the inlet cavity 3a at the holding section 3a2, and the top of the protruding part 3b has a turbulence surface 3b1. The turbulence surface 3b1 is specifically a circular plane. The turbulence surface 3b1 is perpendicular to the central axis of the body 1 and the center of the turbulence surface 3b1 is collinear with the central axis of the body 1.

[0027] As Figure 1 、 Figure 2 andFigure 4 As shown, the other end of the nozzle core 3 is located within the nozzle holder 2, and a diversion portion 3d is protrudingly provided at this end of the nozzle core 3. The outlets of the respective diversion holes 3c are evenly distributed around the diversion portion 3d. A gate 2a is provided within the nozzle holder 2. An outlet passage 2f is provided at the end of the nozzle holder 2 away from the body 1, and the outlet passage 2f is in communication with the gate 2a. The end of the diversion portion 3d is pointed and is located within the gate 2a near the communication position between the gate 2a and the outlet passage 2f. There is a heat insulation gap 4 between the outer peripheral wall of the nozzle core 3 located within the nozzle holder 2 and the inner wall of the nozzle holder 2. A ring-shaped flange 3g is further provided at the end of the nozzle core 3 located within the nozzle holder 2. The outlets of the respective diversion holes 3c are all located inside the ring-shaped flange 3g. Specifically, the nozzle holder 2 at the gate 2a sequentially includes a first straight section 2b, a first contraction section 2c, a second straight section 2d, and a second contraction section 2e along the axial direction. The inner wall of the gate 2a at the first contraction section 2c has a taper. The maximum inner diameter of the gate 2a at the first contraction section 2c is the same as the inner diameter of the gate 2a at the first straight section 2b. The minimum inner diameter at the first contraction section 2c is the same as the inner diameter of the gate 2a at the second straight section 2d. The inner wall of the gate 2a at the second contraction section 2e has a taper. The maximum inner diameter of the gate 2a at the second contraction section 2e is the same as the inner diameter of the gate 2a at the second straight section 2d. The ring-shaped flange 3g is located within the first contraction section 2c. The inner diameter of the ring-shaped flange 3g is between the maximum inner diameter and the minimum inner diameter of the gate 2a at the first contraction section 2c. The heat insulation gap 4 is between the outer peripheral wall of the nozzle core 3 and the inner peripheral wall of the gate 2a at the first straight section 2b. The gate 2a at the second contraction section 2e is in communication with the outlet passage 2f.

[0028] During use, as Figure 5 shown, the other end of the body 1 is connected to the manifold 5 of the hot runner system. Specifically, the manifold 5 has a main runner and a diversion port communicating with the main runner. The other end of the body 1 is fixedly connected to the diversion port position and forms a butt joint therewith, and the outlet passage 2f of the nozzle holder 2 is in butt joint with the cavity on the mold. A heating coil 6 is fixed outside the body 1. The molten plastic sequentially enters the body 1 through the main runner and the diversion port, and then is injected into the cavity of the mold through the nozzle holder 2. As Figure 6 ​As shown, when the molten plastic enters the inlet cavity 3a from within the body 1, since the flow divider core 3 at the inlet cavity 3a includes an acceleration section 3e and 3f axially in sequence, the cavity wall of the inlet cavity 3a at the acceleration section 3e has a taper. The maximum inner diameter of the inlet cavity 3a at the acceleration section 3e is the same as the inner diameter of the body 1, and the minimum inner diameter of the inlet cavity 3a at the acceleration section 3e is the same as the inner diameter of the inlet cavity 3a at the holding section 3f. This causes the flow rate of the molten plastic to increase when passing through the acceleration section 3e (since the flow cross-sectional area at the maximum inner diameter of the inlet cavity 3a at the acceleration section 3e is larger than that at the minimum inner diameter, then the flow rate will increase correspondingly when the passing quantity remains unchanged). That is to say, the molten plastic will enter the inlet cavity 3a at the holding section 3f at a larger flow rate after passing through the acceleration section 3e. At the same time, the protruding portion 3b is located within the inlet cavity 3a at the holding section 3f and its top has a turbulence surface 3b1. After the accelerated molten plastic enters the inlet cavity 3a at the holding section 3f, a part of it will directly impact on the turbulence surface 3b1. Since the accelerated molten plastic has a large kinetic energy, it will sputter widely in all directions and impact the remaining molten plastic after hitting the turbulence surface 3b1. This will, to a certain extent, disrupt the flow of the molten plastic and put it in a state similar to being stirred, so that the molten plastic can be fully mixed before being divided by each flow dividing hole 3c, thereby ensuring that the temperature of the molten plastic becomes uniform.

[0029] After that, the molten plastic enters each flow dividing hole 3c and is divided. Since the cross-section of the flow dividing hole 3c is approximately a regular hexagon, when the molten plastic passes through the flow dividing hole 3c, the six inner side walls of the flow dividing hole 3c form a resistance to the ripples of the molten plastic expanding radially outward and thereby generate a reaction force on the molten plastic. In this way, a secondary turbulence stirring effect on the molten plastic is formed within the flow dividing hole 3c, so that the temperature of the molten plastic becomes even more uniform. Moreover, the distances from the six inner side walls of the flow dividing hole 3c to its central axis are not completely the same, which makes the turbulence effect on the molten plastic more obvious. After the molten plastic flows out of each flow dividing hole 3c, it flows into the gate 2a and finally is injected into the cavity of the mold through the discharge channel 2f.

[0030] The specific embodiments described herein are merely illustrative of the spirit of the present invention. Those skilled in the art to which the present invention pertains can make various modifications or supplements to the described specific embodiments or use similar ways to substitute, but will not deviate from the spirit of the present invention or exceed the scope defined by the appended claims.

Claims

1. The hot nozzle assembly of a hot runner system, comprising a long tubular body (1), a nozzle sleeve (2) fixedly connected to one end of the body (1), and a manifold nozzle core (3) fixed between the two. The end of the manifold nozzle core (3) away from the nozzle sleeve (2) is provided with an inlet cavity (3a), and the manifold nozzle core (3) has a protruding portion (3b) in the inlet cavity (3a). The manifold nozzle core (3) is provided with a plurality of distribution holes (3c) distributed around the protruding portion (3b), characterized in that, The flow dividing nozzle core (3) at the inlet cavity (3a) sequentially includes an acceleration section (3e) and a holding section (3f) along the axial direction. The cavity wall of the inlet cavity (3a) at the acceleration section (3e) has a taper. The maximum inner diameter of the inlet cavity (3a) at the acceleration section (3e) is the same as the inner diameter of the body (1), and its minimum inner diameter is the same as the inner diameter of the inlet cavity (3a) at the holding section (3f). The protruding part (3b) is located in the inlet cavity (3a) at the holding section (3f), and its top has a flow disturbing surface (3b1). The cross-section of the flow dividing hole (3c) is polygonal. The protruding part (3b) has an outer taper. The flow disturbing surface (3b1) is a circular plane. The flow disturbing surface (3b1) is perpendicular to the central axis of the body (1), and the center of the flow disturbing surface (3b1) is collinear with the central axis of the body (1).

2. The hot nozzle assembly of the hot runner system according to claim 1, characterized in that, A part of the flow dividing nozzle core (3) is located in the sprue bushing (2). There is a heat insulation gap (4) between the outer peripheral wall of the flow dividing nozzle core (3) located in the sprue bushing (2) and the inner wall of the sprue bushing (2). The end of the flow dividing nozzle core (3) located in the sprue bushing (2) has an annular convex edge (3g). The outlets of the flow dividing holes (3c) are located inside the annular convex edge (3g).

3. The hot nozzle assembly of the hot runner system according to claim 2, characterized in that, A sprue (2a) is provided in the sprue bushing (2). The sprue bushing (2) at the sprue (2a) sequentially includes a first straight section (2b), a first contraction section (2c), a second straight section (2d), and a second contraction section (2e) along the axial direction. The inner wall of the sprue (2a) at the first contraction section (2c) has a taper. The maximum inner diameter of the sprue (2a) at the first contraction section (2c) is the same as the inner diameter of the sprue (2a) at the first straight section (2b). The minimum inner diameter of the sprue (2a) at the first contraction section (2c) is the same as the inner diameter of the sprue (2a) at the second straight section (2d). The inner wall of the sprue (2a) at the second contraction section (2e) has a taper. The maximum inner diameter of the sprue (2a) at the second contraction section (2e) is the same as the inner diameter of the sprue (2a) at the second straight section (2d). The annular convex edge (3g) is located in the first contraction section (2c). The heat insulation gap (4) is located between the outer peripheral wall of the flow dividing nozzle core (3) and the inner wall of the sprue (2a) at the first straight section (2b). The inner diameter of the annular convex edge (3g) is between the maximum inner diameter and the minimum inner diameter of the sprue (2a) at the first contraction section (2c).

4. The hot nozzle assembly of the hot runner system according to claim 1, characterized in that, The cross-section of the flow dividing hole (3c) is hexagonal, and the distances from the six inner side walls of the flow dividing hole (3c) to its central axis are not completely the same.

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