Hot nozzle assembly for hot runner

Abstract

The application provides a hot nozzle assembly of a hot runner, and belongs to the technical field of injection molds. The application solves the problem of poor product quality caused by temperature fluctuation. The application comprises a body in a tubular shape and vertically arranged, a nozzle head fixed to the lower end of the body, a valve needle arranged in the body and capable of controlling the opening and closing of the nozzle head, and a heating ring arranged outside the body. A guide ring is fixed in the body and located inside the heating ring. At least two positioning portions in a strip shape are radially and protrusively arranged on the inner side of the guide ring. The valve needle passes through the positioning portions. The positioning portions have side top surface one and side top surface two, which are located at the two sides of the positioning portions along the width direction. The side top surface one and the side top surface two are connected in a sharp angle shape. The front end surface of the positioning portion is in a transversely arranged cylindrical curved surface. The application has the advantages of reducing temperature fluctuation and improving product quality.

Description

TECHNICAL FIELD

[0001] The injection mold technology field relates to hot runners, in particular to a hot nozzle assembly of a hot runner. BACKGROUND

[0002] At present, the injection mold commonly used in the injection industry is a hot runner injection mold. Compared with ordinary molds, the plastic products molded by hot runners have higher quality. The hot runner is a device that keeps the plastic in the runner and the gate in a molten state by heating. The hot runner generally includes a hot nozzle assembly, a distribution plate, a temperature control box, and other corresponding accessories. The hot nozzle assembly is divided into open type and needle valve type according to the specific needs. The needle valve type hot nozzle assembly generally includes a body in the shape of a pipe and fixedly connected at the upper end of the distribution port of the distribution plate (the distribution port is in communication with the main flow channel in the distribution plate), and a nozzle head fixedly connected at the lower end of the body. The outer side of the body is provided with a heating ring to heat the flowing melt to keep it in a molten state (specifically, the heating ring generates heat after being powered on, and the heat is transferred to the melt through the body). The lower end of the nozzle head has a gate that is connected to the mold cavity. A valve needle is arranged in the body and can move axially along the body and insert into the gate to block it or move out of the gate to open it. Further, since the valve needle is relatively long, the valve needle needs to be positioned and guided to ensure that the valve needle can stably block or open the gate. For the positioning and guiding of the valve needle, one way is to fix a guide ring with a plurality of positioning parts protruding radially on the inner side of the pipe body. The positioning parts are in the shape of a strip. The valve needle passes between the positioning parts and is positioned and guided by the outer peripheral wall of the valve needle in contact with the positioning parts. The adjacent two positioning parts, the outer peripheral wall of the valve needle and the inner peripheral wall of the guide ring form a flow hole for the melt to pass through. For example, a positioning structure for a needle valve type hot runner hot nozzle is disclosed in patent application No. 202022383284.0.

[0003] In practice, in order to ensure the cooperation accuracy between the valve needle and the gate, the temperature at the gate cannot be too high, otherwise the deformation of the gate is easy to cause the effective sealing of the valve needle to be unable to be formed. Therefore, in the existing valve needle type hot nozzle assembly, there is a gap between the lower end of the heating ring and the gate of the nozzle head, so as to avoid the influence of the heating ring on the temperature at the gate. However, this also means that the flow of the melt plastic from the lower end of the heating ring to the gate is not heated by the heating ring (that is, the temperature of the melt plastic may be reduced after passing through this section), so that the temperature of the melt plastic actually entering the cavity is fluctuated, thereby causing the product quality to be poor. In view of the technical problem of unstable product quality caused by temperature fluctuation, the person skilled in the art can easily think of 1, controlling the distance between the lower end of the heating ring and the gate to reduce the heat loss of the melt plastic in the flow from the lower end of the heating ring to the gate; 2, setting a heat preservation mechanism at the position from the lower end of the heating ring to the gate; 3, setting a heating mechanism corresponding to the position of the cavity in the mold to heat the melt plastic entering the cavity again. SUMMARY

[0004] The purpose of the present application is to solve the problem of poor product quality caused by temperature fluctuation in the prior art.

[0005] The purpose of the present application can be realized by the following technical solutions:

[0006] The hot nozzle assembly of the hot runner comprises a body in a tubular shape and vertically arranged, a nozzle head fixed at the lower end of the body, a valve needle penetrating in the body and capable of controlling the opening or closing of the nozzle head, and a heating ring arranged outside the body. The body is fixed with a guide ring inside and the guide ring is located inside the heating ring. At least two positioning parts in strip shape are arranged radially on the inside of the guide ring, and the valve needle penetrates between each positioning part. The positioning part has a side top surface one and a side top surface two, and the side top surface one and the side top surface two are located at the two edges of the positioning part in the width direction. The side top surface one and the side top surface two are connected in a sharp angle, and the front end surface of the positioning part is a horizontally arranged cylindrical curved surface.

[0007] The same as prior art, the valve needle outer peripheral wall, the guide ring inner peripheral wall and the side wall between the two adjacent positioning portions also form flow holes, and the melt plastic flows downward through the flow holes. In the present application, the positioning portion has a side top surface one and a side top surface two, the side top surface one and the side top surface two are located at two sides of the positioning portion along the width direction and are connected in a sharp angle, and the front end surface of the positioning portion is further provided as a horizontally arranged cylindrical curved surface, so that a roof-like structure is formed on the positioning portion. This structure is very beneficial to the flow of the melt plastic, thereby accelerating the flow speed of the melt plastic. In this way, the melt plastic can quickly pass through the range not covered by the heating ring from the lower end of the heating ring to the gate of the nozzle head, thereby reducing the temperature fluctuation of the melt plastic from the body to the cavity, and ensuring the product quality.

[0008] In the hot nozzle assembly of the hot runner described above, the front end surface of the positioning portion is slightly inwardly concave along the horizontal direction.

[0009] By setting the front end surface of the positioning portion as a slightly inwardly concave arc along the horizontal direction, the flow speed of the melt plastic can be accelerated by the roof-like structure formed above, and the positioning and guiding functions can be ensured by the position of the inwardly concave arc abutting against the valve needle outer peripheral wall.

[0010] In the hot nozzle assembly of the hot runner described above, the side top surface one and the side top surface two are both smoothly connected to the inner peripheral wall of the guide ring by a circular arc.

[0011] The side top surface one and the side top surface two are connected in a sharp angle, which means that the side top surface one and the side top surface two are both inclined. The side top surface one and the side top surface two are both smoothly connected to the inner peripheral wall of the guide ring by a circular arc, which means that the side top surface one and the side top surface two are both partially extended to the inner peripheral wall of the guide ring. This means that the flow speed of the melt plastic can be accelerated at the connection position between the side top surface one and the inner peripheral wall of the guide ring or the connection position between the side top surface two and the inner peripheral wall of the guide ring.

[0012] In the hot nozzle assembly of the hot runner described above, the number of the positioning portions is three, and each positioning portion is uniformly distributed along the center line of the guide ring.

[0013] In the hot nozzle assembly of the hot runner mentioned above, the body comprises, from top to bottom, a holding section one, an acceleration section, a holding section two and a connecting section, the inner wall of the acceleration section has a taper, the maximum inner diameter of the acceleration section is the same as the inner diameter of the holding section one and the minimum inner diameter of the acceleration section is the same as the inner diameter of the holding section two, the inner diameter of the connecting section is larger than the inner diameter of the holding section two and the body has an abutting surface connecting the inner wall of the holding section two and the inner wall of the connecting section, the guide ring is arranged in the connecting section, the upper end of the nozzle head has a connecting part with a thread connected in the connecting section and the guide ring is fixed between the connecting part and the abutting surface, the length of the holding section one is about 1 / 2-2 / 3 of the body, the length of the acceleration section is about equal to the length of the holding section two and is 2-3 times the thickness of the guide ring.

[0014] Because the inner wall of the acceleration section of the body has a taper, the maximum inner diameter of the acceleration section is the same as the inner diameter of the holding section one and the minimum inner diameter of the acceleration section is the same as the inner diameter of the holding section two, the flow rate of the melt plastic increases when passing through the acceleration section (the flow cross-sectional area at the maximum inner diameter of the acceleration section is larger than the flow cross-sectional area at the minimum inner diameter of the acceleration section, so the flow rate increases accordingly when the amount of passing through is unchanged), that is, the melt plastic enters the holding section two at a larger flow rate after passing through the acceleration section, thereby forming a first acceleration of the melt plastic, and in combination with the second acceleration when passing through the flow hole, the speed of the melt plastic through the range not covered by the heating ring from the lower end of the heating ring to the nozzle head is further improved, the temperature fluctuation of the melt plastic from the body into the cavity is reduced, and the product quality is ensured.

[0015] In the hot nozzle assembly of the hot runner mentioned above, the length of the holding section one is about 1 / 2-2 / 3 of the body, the length of the acceleration section is about equal to the length of the holding section two and is 2-3 times the thickness of the guide ring.

[0016] Because the length of the holding section one is about 1 / 2-2 / 3 of the body, the length of the acceleration section is about equal to the length of the holding section two and is 2-3 times the thickness of the guide ring, on the one hand, the length of the holding section one is relatively long, so that the melt plastic can be fully heated to maintain the temperature, on the other hand, it also means that the distance between the maximum inner diameter of the acceleration section and the flow hole is not too long, and the melt plastic is directly accelerated again by the setting of the action surface one and the action surface two at the flow hole after being accelerated by the acceleration section.

[0017] Compared with the prior art, the hot nozzle assembly of the hot runner has the positioning portion provided with side top surface one and side top surface two, the side top surface one and the side top surface two are located at two sides of the positioning portion along the width direction and connected in a sharp angle, and the front end surface of the positioning portion is provided as a horizontally arranged cylindrical curved surface, so that a roof-like structure is formed on the positioning portion, which is very beneficial to the flow of the melt plastic, thereby accelerating the flow speed of the melt plastic, so that the melt plastic can pass through the range not covered by the heating ring from the lower end of the body to the gate of the nozzle head more quickly, the temperature fluctuation of the melt plastic from the body to the cavity is reduced, and the product quality is ensured. BRIEF DESCRIPTION OF DRAWINGS

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

[0019] Figure 2 is Figure 1 is an enlarged view of the lower end of the body in

[0020] Figure 3 is Figure 2 is a sectional view of A-A in

[0021] Figure 4 is a perspective view of the guide ring.

[0022] Figure 5 is a top view of the guide ring.

[0023] In the drawings, 1, the body; 1a, the retaining section one; 1b, the acceleration section; 1c, the retaining section two; 1d, the connecting section; 1e, the abutting surface; 2, the nozzle head; 2a, the gate; 2b, the connecting portion; 3, the valve needle; 4, the heating ring; 5, the guide ring; 5a, the positioning portion; 5a1, the side top surface one; 5a2, the side top surface two; 5a3, the front end surface; 6, the flow hole; 7, the flow distribution plate; 7a, the main flow channel; 7b, the flow distribution port. DETAILED DESCRIPTION

[0024] The following is a specific embodiment of the present application and further describes the technical solution of the present application in conjunction with the drawings, but the present application is not limited to these embodiments.

[0025] As Figures 1-5As shown in the figure, the hot nozzle assembly of the hot runner comprises a tubular body 1, a nozzle head 2 fixed at the lower end of the body 1, a valve needle 3 movably arranged in the body 1 along the axial direction, and a heating ring 4 arranged outside the body 1. The lower end of the nozzle head 2 has a gate 2a. The lower end of the heating ring 4 is spaced apart from the gate 2a. The valve needle 3 can be inserted into the gate 2a to block the gate 2a by moving downward or can be withdrawn from the gate 2a by moving upward. A guide ring 5 is fixed in the body 1 and located inside the heating ring 4. The inside of the guide ring 5 is provided with at least two strip-shaped positioning portions 5a protruding radially. The valve needle 3 passes between the positioning portions 5a. The outer peripheral wall of the valve needle 3 is in contact with the end of each positioning portion 5a close to the center line of the guide ring 5 to form a positioning guide. The over-flow hole 6 is formed between the outer peripheral wall of the valve needle 3, the inner peripheral wall of the guide ring 5, and the side wall of the adjacent two positioning portions 5a. In this embodiment, the number of positioning portions 5a is three, and each positioning portion 5a is uniformly distributed along the center line of the guide ring 5, so that the number of over-flow holes 6 formed is three.

[0026] Further, as shown in Figure 4 and Figure 5 , the positioning portion 5a has side top surface one 5a1 and side top surface two 5a2. The side top surface one 5a1 and the side top surface two 5a2 are located at both sides of the positioning portion 5a along the width direction. The side top surface one 5a1 and the side top surface two 5a2 are symmetrically arranged. The side top surface one 5a1 and the side top surface two 5a2 are connected in a sharp angle, and the side top surface one 5a1 and the side top surface two 5a2 are smoothly connected to the inner peripheral wall of the guide ring 5 through a circular arc. Further, the front end surface 5a3 of the positioning portion 5a is a horizontally arranged cylindrical curved surface. The front end surface 5a3 here refers to the end surface of the positioning portion 5a close to the center line of the guide ring 5. The front end surface 5a3 of the positioning portion 5a is slightly concave inward along the horizontal direction, and the outer peripheral wall of the valve needle 3 is attached to the position of the concave inward. In this embodiment, the position of the concave inward is at the middle position of the front end surface 5a3 of the positioning portion 5a.

[0027] As shown in Figure 1 and Figure 2As shown, the body 1, from top to bottom, includes a holding section 1a, an acceleration section 1b, a holding section 2c, and a connecting section 1d. The inner walls of the holding sections 1a, 2c, and 1d are all cylindrical. The inner wall of the acceleration section 1b is tapered. The maximum inner diameter of the acceleration section 1b is the same as the inner diameter of the holding section 1a, and the minimum inner diameter of the acceleration section 1b is the same as the inner diameter of the holding section 2c. The length of the acceleration section 1b is approximately equal to the length of the holding section 2c and is 2-3 times the thickness of the guide ring 5. The inner diameter of the connecting section 1d is larger than the inner diameter of the holding section 2c, and the body 1 has a contact surface 1e that connects the inner wall of the holding section 2c to the inner wall of the connecting section 1d. The guide ring 5 is located inside the connecting section 1d. The upper end of the nozzle head 2 has a connecting part 2b that is threaded into the connecting section 1d, and the guide ring 5 is fixed between the connecting part 2b and the contact surface 1e.

[0028] When using, such as Figure 1 As shown, the upper end of the body 1 is fixedly connected to the manifold 7 of the hot runner. Specifically, the manifold 7 has a main channel 7a and a branch port 7b connected to the main channel 7a. The upper end of the body 1 is fixedly connected to the branch port 7b and forms a docking with it. The gate 2a at the lower end of the nozzle head 2 forms a docking with the cavity on the mold. The upper end of the valve needle 3 extends out of the manifold 7 and is actually driven by a hydraulic cylinder. During injection molding, the hydraulic cylinder drives the valve needle 3 to move upward so that its lower end is dislodged from the gate 2a (the movement of the valve needle 3 is positioned and guided by the three positioning parts 5a of the guide ring 5). The molten plastic enters the body 1 from the main channel 7a through the branch port 7b and is finally injected into the cavity of the mold through the gate 2a.

[0029] Because the inner wall of the acceleration section 1b of the main body 1 is tapered, the maximum inner diameter of the acceleration section 1b is the same as the inner diameter of the holding section 1a, and the minimum inner diameter of the acceleration section 1b is the same as the inner diameter of the holding section 1c, the flow velocity of the molten plastic will increase when it passes through the acceleration section 1b (the flow cross-sectional area at the maximum inner diameter of the acceleration section 1b is larger than the flow cross-sectional area at the minimum inner diameter of the acceleration section 1b, and the flow velocity will increase accordingly when the amount passing through remains unchanged). In other words, after passing through the acceleration section 1b, the molten plastic will enter the holding section 1c with a larger flow velocity, thus forming a primary acceleration of the molten plastic. Since the length of the holding section 1a is approximately 1 / 2 to 2 / 3 of the body 1, and the length of the acceleration section 1b is approximately equal to the length of the holding section 1c and is 2 to 3 times the thickness of the guide ring 5, on the one hand, the relatively long length of the holding section 1a allows the molten plastic to be fully heated to maintain the temperature, and on the other hand, it also means that the distance between the maximum inner diameter of the acceleration section 1b and the flow hole 6 will not be too long. The molten plastic will be accelerated again at the flow hole 6 shortly after being accelerated by the acceleration section 1b.

[0030] When the melt plastic passes through each overflow hole 6 from the holding section two 1c, since each positioning part 5a has side top surface one 5a1 and side top surface two 5a2, which are located at both sides of the positioning part 5a along the width direction and connected with each other in a sharp angle, and the front end surface of each positioning part 5a is set as a horizontally arranged cylindrical curved surface, a roof-like structure is formed on each positioning part 5a, which is very beneficial to the flow of the melt plastic, thus increasing the flow speed of the melt plastic. In this way, the melt plastic can pass through the range of the lower end of the heating ring 4 to the gate 2a of the nozzle head 2, which is not covered by the heating ring 4, more quickly, reducing the temperature fluctuation of the melt plastic from the body 1 to the entering of the cavity, thus ensuring the product quality.

[0031] The specific embodiments described herein are merely illustrative of the principles of this application. Numerous modifications or adaptations will be readily apparent to those skilled in the art of this application without departing from the spirit or scope of the application as defined by the following claims.

Claims

1. A hot nozzle assembly of hot runner, comprising a body (1) in tubular shape and vertically arranged, a nozzle head (2) fixed at the lower end of the body (1), a valve needle (3) penetrating in the body (1) and capable of controlling the opening or closing of the nozzle head (2), and a heating coil (4) arranged outside the body (1), wherein a guide ring (5) is fixed in the body (1) and located inside the heating coil (4), and at least two positioning portions (5a) in strip shape are radially protruded and arranged at the inner side of the guide ring (5), and the valve needle (3) penetrates between the positioning portions (5a). The positioning part (5a) has side top surface one (5a1) and side top surface two (5a2), and the side top surface one (5a1) and the side top surface two (5a2) are located at both sides of the positioning part (5a) along the width direction, the side top surface one (5a1) and the side top surface two (5a2) are connected in a sharp angle shape, the front end surface (5a3) of the positioning part (5a) is horizontally arranged and protrudes in a cylindrical curved surface towards the center line of the valve needle (3), the front end surface (5a3) of the positioning part (5a) is slightly concave inward along the horizontal direction in an arc shape, and the concave arc is located at the middle position of the front end surface (5a3) of the positioning part (5a) along the axial direction of the valve needle (3).

2. The hot nozzle assembly of a hot- flowpit for a hot- flowpit die as recited in claim 1, wherein, The side top surface one (5a1) and the side top surface two (5a2) are both smoothly connected with the inner wall of the guide ring (5) through an arc.

3. The hot nozzle assembly of a hot- flowpath die of claim 1 or 2, wherein, The number of the positioning part (5a) is three, and each positioning part (5a) is uniformly distributed along the center line of the guide ring (5).

4. The hot nozzle assembly of a hot- flowpath die of claim 1 or 2, wherein, The body (1) sequentially includes a holding section one (1a), an acceleration section (1b), a holding section two (1c) and a connecting section (1d) from top to bottom, the inner wall of the acceleration section (1b) has a taper, the maximum inner diameter of the acceleration section (1b) is the same as the inner diameter of the holding section one (1a), and the minimum inner diameter of the acceleration section (1b) is the same as the inner diameter of the holding section two (1c), the inner diameter of the connecting section (1d) is larger than the inner diameter of the holding section two (1c), and the body (1) has an abutting surface (1e) connecting the inner wall of the holding section two (1c) and the inner wall of the connecting section (1d), the guide ring (5) is arranged in the connecting section (1d), the upper end of the nozzle head (2) has a connecting part (2b) screwed in the connecting section (1d), and the guide ring (5) is fixed between the connecting part (2b) and the abutting surface (1e), the length of the holding section one (1a) is 1 / 2-2 / 3 of the body (1), the length of the acceleration section (1b) is equal to the length of the holding section two (1c), and is 2-3 times the thickness of the guide ring (5).

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