CN111730818A

CN111730818A - Sprue structure for injection mold and injection mold

Info

Publication number: CN111730818A
Application number: CN202010575394.9A
Authority: CN
Inventors: 丁丹辉; 陈宏�
Original assignee: Menshen Packaging Shanghai Co Ltd
Current assignee: Menshen Packaging Shanghai Co Ltd
Priority date: 2020-06-22
Filing date: 2020-06-22
Publication date: 2020-10-02

Abstract

The invention relates to a gate structure for an injection mold and the injection mold, wherein the gate structure comprises a primary runner, a limiting gate, a secondary runner and a non-limiting gate, one end of the primary runner is a pouring opening, the other end of the primary runner is connected with an inlet of the limiting gate, an outlet of the limiting gate is connected with the secondary runner, an inlet of the non-limiting gate is connected with the secondary runner, an outlet of the non-limiting gate is connected with a cavity, the sectional area of the primary runner is larger than that of the secondary runner, the sectional area of the inlet of the limiting gate is larger than that of the outlet, and the sectional area. Compared with the prior art, the invention accelerates and rubs the plastic melt material by limiting the sprue, so that the temperature of the melt material is raised, an ideal flowing state is achieved, the secondary flow channel is quickly filled, and the function of preventing the melt material from flowing backwards is achieved; the melt in the non-restriction sprue guide secondary runner fills the molding cavity and is not easy to generate plastic vortex, flocculation and other phenomena, and the molding quality of the final injection molding product is effectively improved.

Description

Sprue structure for injection mold and injection mold

Technical Field

The invention relates to the field of mold injection molding processes, in particular to a gate structure for an injection mold and the injection mold.

Background

The gate is a portion connecting the runner and the molding cavity in the injection mold. The sprue has the function that molten plastic from the runner enters the forming cavity at the highest speed and is filled in the forming cavity, and after the forming cavity is filled, the sprue can be rapidly cooled and closed, so that the plastic which is not cooled in the forming cavity is prevented from flowing back. The configuration and location of the gate directly affects whether the melt can be properly injected and molded with high quality.

The prior sprue is generally a short groove with a fine cross section. In general, as molten plastic flows into the runner, the melt is first cooled and solidified near the mold surface to form a solidified layer, and then flows forward through the solidified layer, so that ideally, after the mold cavity is filled with plastic, the gate can be rapidly cooled and closed. However, for some molds with long runners, the flowability of the plastic is poor, so that the molten plastic cannot be stably filled in the molding cavity, and thus, the molded product has the defects of flow marks, bubbles, bonding lines, ripples, uneven shrinkage and the like, and particularly, the yield is low for the product made of transparent materials.

Disclosure of Invention

The invention aims to overcome the defects in the prior art and provide a gate structure for an injection mold and the injection mold, which can increase the fluidity of internal molten plastic during injection molding, enhance the molding stability of a product and remarkably improve the internal and external appearance quality of the molded product.

The purpose of the invention can be realized by the following technical scheme:

the utility model provides a runner structure for injection mold, includes one-level runner, restriction runner, second grade runner and non-restriction runner, one end of one-level runner for pour the mouth, the entry of restriction runner is connected to the other end, the exit linkage second grade runner of restriction runner, the entry linkage second grade runner of non-restriction runner, the exit linkage becomes the die cavity, the sectional area of one-level runner be greater than the sectional area of second grade runner, the entry sectional area of restriction runner is greater than the exit sectional area, the entry sectional area of non-restriction runner is less than the exit sectional area.

Furthermore, the section of the secondary flow passage is semicircular.

Furthermore, the section of the primary flow channel is arc trapezoid.

Furthermore, the limiting sprue is a cone, an outlet of the limiting sprue is arranged at the top end of the cone, and an inlet of the limiting sprue is arranged at the bottom end of the cone.

Further, the non-limiting sprue is a flat sector, an outlet of the non-limiting sprue is arranged at the unfolding end of the sector, and an inlet of the non-limiting sprue is arranged at the folding end of the sector.

Further, the inlet of the non-limiting gate is connected with the center of the side wall of the secondary flow channel.

Furthermore, the ratio of the cross sections of the primary flow channel and the secondary flow channel is 7: 5-8: 5.

Further, the length of the secondary flow channel is 3-5 times of the maximum width of the sectional area of the secondary flow channel.

An injection mould comprising at least one gate structure as described above for an injection mould.

Furthermore, the injection mold comprises a plurality of molding cavities, each molding cavity is connected with one gate structure, and pouring openings of primary runners of all the gate structures are connected.

Compared with the prior art, the invention has the following beneficial effects:

1. the invention designs a four-section structure of a primary runner, a limiting sprue, a secondary runner and a non-limiting sprue; the plastic melt is accelerated and rubbed through the limiting sprue with the inlet larger than the outlet, so that the temperature of the melt is increased, the viscosity is reduced, the shearing speed is increased, an ideal flowing state is achieved, the secondary flow channel is quickly filled, and the function of preventing the melt from flowing backwards is achieved; the melt in the non-restriction runner guide second grade runner that is less than the export through the entry fills the die cavity, and this structure is difficult for producing phenomenons such as plastics vortex, wadding in disorder, can make the melt evenly fill each part of die cavity, has effectively improved the shaping quality of final injection moulding product.

2. The section of the secondary flow passage is semicircular, the semicircular section enables the ratio of the surface area to the volume of the secondary flow passage to be minimum, and pressure loss and temperature loss are small in the flow passages with the same volume, so that flow and pressure conduction of molten materials are facilitated.

3. The non-limiting gate is a flat sector, so that the internal stress of a formed product can be reduced, the generation of ejection lines is reduced, and the gate is particularly suitable for flat products and transparent products.

Drawings

Fig. 1 is a perspective view of a gate structure.

Fig. 2 is a schematic plan view of a gate structure.

FIG. 3 is a schematic cross-sectional view of a primary flow path.

FIG. 4 is a schematic cross-sectional view of a secondary flow channel.

Fig. 5 is an overall schematic view of an injection mold.

Reference numerals: 1. a primary runner, 2, a limiting sprue, 3, a secondary runner, 4, a non-limiting sprue and 5, and a molding cavity.

Detailed Description

The invention is described in detail below with reference to the figures and specific embodiments. The present embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation manner and a specific operation process are given, but the scope of the present invention is not limited to the following embodiments.

Example one

As shown in fig. 1 and 2, the present embodiment provides a gate structure for an injection mold, including a primary runner 1, a restricted gate 2, a secondary runner 3, and a non-restricted gate 4. One end of the primary runner 1 is a pouring opening, the other end of the primary runner is connected with an inlet of the limiting sprue 2, and an outlet of the limiting sprue 2 is connected with the secondary runner 3. The secondary flow passage 3 is connected to a cavity 5 through a non-limited outlet, specifically, an inlet of the non-limited gate 4 is connected to the center of the side wall of the secondary flow passage 3, and an outlet is connected to the cavity 5.

The limiting sprue 2 is a cone, an outlet of the limiting sprue 2 is arranged at the top end of the cone, and an inlet of the limiting sprue 2 is arranged at the bottom end of the cone. The inlet sectional area of the restricting gate 2 is larger than the outlet sectional area. The limiting sprue 2 of the structure enables the plastic melting material sent by the runner to generate abrupt flow velocity increase through abrupt change of the section size, generates great friction to enable the melting material temperature to rise, improves the shearing rate and reduces the viscosity, enables the melting material to become an ideal flowing state, and further can quickly and evenly fill the secondary runner 3.

The unrestricted gate 4 is a flat sector, the outlet of the unrestricted gate 4 is located at the flared end of the sector and the inlet of the unrestricted gate 4 is located at the converging end of the sector. The inlet sectional area of the unrestricted gate 4 is smaller than the outlet sectional area. The non-limiting gate 4 is connected to the molding cavity 5, and a large amount of melt flows into the molding cavity 5 through the non-limiting gate 4 in a short time during injection molding, and uniformly fills the respective portions of the molding cavity 5. The structure is not easy to generate plastic vortex, flocculation and other phenomena, and the molding quality of the final injection molding product is effectively improved. The flat fan-shaped shape can also reduce the internal stress of the formed product and reduce the generation of shot lines, and is particularly suitable for flat plate-shaped products and transparent material products.

As shown in fig. 3 and 4, the primary flow channel 1 is a main flow channel, and has a circular trapezoid cross section. The primary channel 1 is a conventional channel distribution, and its shape and size will affect the fluidity of the molten material therein. The cross section of the secondary flow channel 3 is semicircular, the semicircular cross section enables the ratio of the surface area to the volume of the secondary flow channel 3 to be minimum, and pressure loss and temperature loss are small in the flow channel with the same volume, so that flow and pressure conduction of molten materials are facilitated. The sectional area of the first-stage runner 1 is larger than that of the second-stage runner 3, the ratio of the sectional areas is generally 7:5 to 8:5, and the sectional area of the first-stage runner 1 in this embodiment is 15.66mm²The sectional area of the secondary flow passage 3 is 9.82mm². The secondary runner 3 is short in length so that the melt after being accelerated inside can rapidly enter the molding cavity 5 through the non-limiting gate 4. The length of the secondary flow channel 3 is generally 3 to 5 times of the maximum width of the cross-sectional area, and the length is 17mm in this embodiment.

Example two

As shown in fig. 5, the present embodiment provides an injection mold including the gate structure disclosed in the first four embodiments. The product of the injection mold has an irregular wall thickness and a circular outer diameter, and 100% of PMMA raw material is used. Therefore, the product has the requirements of transparency and high appearance quality, and cannot have appearance problems of flow marks, bubbles, cold materials and the like.

In this embodiment, four molding cavities are arranged in a matrix, and four gate structures are arranged in a cross shape, so that the balance of the whole runner is realized. The pouring openings of the primary runners of all the sprue structures are connected and located in the center of the mold, so that molten materials can uniformly enter each sprue structure through one pouring opening, and therefore the plastic molten materials can be quickly and uniformly filled into the molding cavity, and qualified products are obtained.

The foregoing detailed description of the preferred embodiments of the invention has been presented. It should be understood that numerous modifications and variations could be devised by those skilled in the art in light of the present teachings without departing from the inventive concepts. Therefore, the technical solutions available to those skilled in the art through logic analysis, reasoning and limited experiments based on the prior art according to the concept of the present invention should be within the scope of protection defined by the claims.

Claims

1. The utility model provides a runner structure for injection mold, characterized in that, includes one-level runner (1), restriction runner (2), second grade runner (3) and non-restriction runner (4), the one end of one-level runner (1) for pouring the mouth, the entry of restriction runner (2) is connected to the other end, exit linkage second grade runner (3) of restriction runner (2), the entry linkage second grade runner (3) of non-restriction runner (4), exit linkage shaping chamber (5), the sectional area of one-level runner (1) be greater than the sectional area of second grade runner (3), the entry sectional area of restriction runner (2) is greater than the exit sectional area, the entry sectional area of non-restriction runner (4) is less than the exit sectional area.

2. A gate structure for injection mold according to claim 1, wherein the secondary runner (3) has a semicircular cross section.

3. A gate structure for injection mold according to claim 1, wherein the cross section of the primary runner (1) is arc trapezoid.

4. A gate structure for an injection mold according to claim 1, wherein the restricting gate (2) is a cone, an outlet of the restricting gate (2) is provided at a top end of the cone, and an inlet of the restricting gate (2) is provided at a bottom end of the cone.

5. A gate structure for an injection mold according to claim 1, wherein the unrestricted gate (4) is a flat sector, the outlet of the unrestricted gate (4) being located at the flared end of the sector and the inlet of the unrestricted gate (4) being located at the converging end of the sector.

6. Gate structure for an injection mould according to claim 1, characterised in that the inlet of the non-restricted gate (4) is connected to the centre of the side wall of the secondary runner (3).

7. The gate structure for injection mold according to claim 1, wherein the ratio of the cross-sectional area of the primary runner (1) to the cross-sectional area of the secondary runner (3) is 7:5 to 8: 5.

8. The gate structure for injection mold according to claim 1, wherein the length of the secondary runner (3) is 3 to 5 times the maximum width of its cross-sectional area.

9. An injection mold comprising at least one gate structure for an injection mold according to any one of claims 1 to 7.

10. An injection mould according to claim 9, characterized in that it comprises a plurality of mould cavities (5), each mould cavity (5) being associated with a gate structure, the pouring openings of the primary runners (1) of all gate structures being connected.