Injection molding mold

Abstract

The present invention provides an injection molding die in which the gate remains separated when the molded body is ejected. [Solution] An injection molding die having a movable side having an ejector, a cavity, and a gate, and a fixed side having a runner formed thereon, is provided on the movable side at a position in contact with the runner and gate on the fixed side, which protrudes toward the fixed side to separate the material filled in the runner and gate by the injection process from the material filled in the cavity by the injection process. On the fixed side, a return pin is provided at a position opposite to the cut pin on the movable side, which retracts toward the fixed side in response to the protruding movement of the cut pin, and returns the cut pin to its original position after the molded body has been ejected. The surface of the return pin facing the cut pin is provided with an inclined portion that is recessed toward the runner side, so that the portion separated from the molded body by the cut pin can be integrated with the runner and discharged out of the mold.

Description

Technical Field

[0001] The present invention relates to a mold for injection molding, and relates to a mold for injection molding that can separate a gate from a molded body within the mold before the molded body is taken out.

[0002] Injection molding fills a hollow part called a cavity engraved in a mold with a thermoplastic polymer material melted by heating at high pressure, cools and solidifies it to obtain a molded body. It has high productivity and is widely used. In some cases, it is also used for molding thermosetting polymer materials.

[0003] In injection molding, a polymer material melted in the cylinder of an injection molding machine is pressed into a cavity from a nozzle at the tip of the cylinder through a sprue, a runner, and a gate. After the molded body is cooled to some extent, an ejector pin or an ejector sleeve is operated to push it out from the cavity.

[0004] Therefore, the molded body pushed out from the mold is integrated with the sprue, the runner, and the gate, and a process of cutting the boundary between the gate and the molded body to separate the molded body is required. This process can be automated, but in some cases, it may be necessary to manually perform it using tools such as nippers, which hinders the reduction of manufacturing costs.

[0005] As one of the technologies that eliminate the post-treatment of the gate of the molded body, a submarine gate can be cited. This is a method of providing the tip of the gate so as to penetrate the mold and incorporating the gate into the side surface of the cavity. The merits obtained include: (1) the molding cycle time can be shortened, and (2) the tip of the gate is automatically separated from the molded body simultaneously when the product is pushed out. On the other hand, the demerits include that since the area of the gate is smaller than that of a general side gate, the pressure loss during filling the molten material is large, and the possibility of generating a short shot increases.

[0006] On the other hand, as a gate cutting method applicable to general-purpose side gates, Patent Document 1 discloses a gate cutting method that uses a mold in which a molding space and a side gate into which a soft material with a Shore A hardness of 90 or less is injected between a clamped core and a cavity, a first extrusion means that pushes the injection-molded body molded in the molding space toward the core near the connection between the molding space and the side gate when the mold is opened, and a second extrusion means that is formed in a manner connected to the injection-molded body and pushes residual material remaining in the side gate or the injection channel including the side gate toward the cavity near the connection when the mold is opened, characterized in that when the mold is opened, the injection-molded body and the residual material are cut and separated at their connection point by the first extrusion means and the second extrusion means.

[0007] However, the gate-cutting method disclosed herein is somewhat complex in its configuration and has room for improvement in terms of cost and versatility. [Prior art documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2021-120183 [Overview of the Initiative] [Problems that the invention aims to solve]

[0009] Therefore, the object of the present invention is to provide an injection molding die in which the gate is separated when the molded body is ejected. [Means for solving the problem]

[0010] This invention was made as a result of a thorough re-examination of the structure of injection molding dies in order to solve the aforementioned problems.

[0011] An injection molding die according to one aspect of the present invention has a movable side having at least one of an ejector pin or an ejector sleeve, a cavity, and a gate, and a fixed side having a runner formed thereon, wherein a cut pin is provided on the movable side at a position in contact with the runner and the gate on the fixed side, protruding toward the fixed side to separate the material filled in the runner and the gate by the injection process from the material filled in the cavity by the injection process, and a return pin is provided on the fixed side at a position opposite to the cut pin on the movable side, retracting toward the fixed side in response to the protruding movement of the cut pin, and returning the cut pin to its original position after the ejection of the molded body, wherein the surface of the return pin facing the cut pin is provided with an inclined portion toward the runner side.

[0012] Furthermore, an injection molding die according to one aspect of the present invention is characterized in that, when the cut pin is protruding, the distance between the runner-side end of the cut pin and the ridge where the fixed-side surface of the runner and the through hole through which the return pin slides intersects is 0.1 mm or more.

[0013] Furthermore, an injection molding die according to one aspect of the present invention is characterized in that the side surface of at least one of the cut pin or the fixed return pin that is positioned in the cavity forms a part of the inner wall of the cavity. [Effects of the Invention]

[0014] In the injection molding die according to the present invention, as described above, a cut pin is positioned to contact the gate and the runner, making it possible to separate the material filled in the cavity from the material filled in the gate during the injection process. This eliminates the need to cut the gate of the molded body ejected from the die, contributing to improved productivity.

[0015] Furthermore, in the injection molding die according to the present invention, by setting the distance between the runner-side end of the cut pin when the cut pin protrudes and the ridge where the fixed-side surface of the runner and the through-hole through which the return pin slides intersect to 0.1 mm or more, the portion separated from the molded body by the cut pin and the runner are discharged while still connected. This prevents the gate and the portion of the runner that contacts the cut pin from being left behind in the mold during a series of molding cycles. Therefore, the molding cycle is not interrupted.

[0016] Furthermore, in the injection molding die according to the present invention, the side surface of at least one of the cut pin or return pin that is positioned in the cavity can be configured to form a part of the inner wall of the cavity, thereby suppressing the occurrence of marks on the gate portion of the molded body. This effect can be improved by operating the cut pin after the injection process, before the material filled in the gate and cavity has cooled and solidified sufficiently. [Brief explanation of the drawing]

[0017] [Figure 1] Perspective view showing an example of a molded body. [Figure 2] This diagram schematically shows an example of a cross-section of the cavity and gate portion of an injection molding die according to the present invention. [Figure 3] This diagram schematically shows an example of a cross-section near the cavity and gate of a mold, where molten material has filled cavity 3 via the runner and gate. [Figure 4] This diagram schematically shows an example of a cross-section where the cut pin protrudes from the movable side towards the fixed side, separating the gate from the molded body. [Modes for carrying out the invention]

[0018] Next, embodiments of the present invention will be described with reference to specific drawings.

[0018] FIG. 1 is a perspective view showing an example of a molded body described in the embodiment of the present invention. Here, a case of a mold for obtaining a cylindrical molded body with open upper and lower ends shown in FIG. 1 will be described.

[0019] FIG. 2 is a diagram schematically showing an example of a cross-section near the runner, cavity, and gate portions of an injection mold according to the present invention. In FIG. 2, 1 is the movable side, 2 is the fixed side, 3 is the cavity, 4 is the protruding sleeve, 5 is the runner, 6 is the gate, 7 is the cut pin, 8 is the return pin, 9 is an inclined portion provided so that the runner side is recessed on the side facing the cut pin of the return pin, and 10 is the parting line.

[0020] FIG. 3 is a diagram schematically showing an example of a cross-section near the runner, cavity, and gate portions of the mold in a state where the cavity 3 is filled with the molten material via the runner 5 and the gate 6, that is, after the injection process.

[0021] FIG. 4 is a diagram schematically showing an example of a cross-section in a state where the cut pin 7 protrudes from the movable side 1 toward the fixed side 2 and separates the gate 6 from the molded body. As shown in FIG. 4, the region surrounded by the broken line, that is, a part 11 of the gate 6 and the runner 5 separated from the molded body by the cut pin 7, has an inclined portion where the runner side is recessed on the side facing the cut pin 7 of the return pin 8, so it does not separate from the runner side. For this reason, this part remains in the mold, and as described above, it does not cause any trouble such as being sandwiched or clogged in the sliding parts of the mold when the mold is opened and closed.

[0022] Further, by setting the distance between the end of the cut pin 7 on the runner 5 side and the ridge where the surface of the fixed side 2 of the runner 5 intersects with the through-hole through which the return pin 8 slides, that is, g in FIG. 4, to 0.1 mm or more, the above-described effect can be surely exhibited. By configuring the right side surface of the cut pin in FIG. 4 to form the inner wall of the cavity 3, it is possible to make the gate mark of the molded body less conspicuous.

[0023] As described above, according to the present invention, when the molded body is pushed out, it is possible to provide a mold in which the gate is separated, eliminating the need for a gate treatment process and contributing to an improvement in the productivity of injection molding. The present invention is not limited to the above-described embodiment, and any design changes including various modifications and corrections that can be conceived by those having ordinary knowledge in the field of the present invention and that do not depart from the gist of the present invention are of course included in the present invention.

Explanation of Reference Numerals

[0028] 1 ··· movable side 2 ··· fixed side 3 ··· cavity 4 ··· protruding sleeve 5 ··· runner 6 ··· gate 7 ··· cut pin 8 ··· return pin 9 ··· inclined portion 10 ··· parting line 11 ··· part of the gate and runner separated from the molded body by the cut pin

Claims

1. An injection molding die comprising a movable side having at least one of an ejector pin or an ejector sleeve, a cavity, and a gate, and a fixed side having a runner formed thereon, wherein a cut pin is provided on the movable side at a position in contact with the runner and the gate on the fixed side, protruding toward the fixed side to separate the material filled in the runner and the gate by the injection process from the material filled in the cavity by the injection process, and a return pin is provided on the fixed side at a position opposite to the cut pin on the movable side, retracting toward the fixed side in response to the protruding movement of the cut pin, and returning the cut pin to its original position after the ejection of the molded body, wherein the surface of the return pin facing the cut pin is provided with an inclined portion that recesses toward the runner side.

2. The injection molding die according to claim 1, characterized in that, when the cut pin protrudes, the distance between the runner-side end of the cut pin and the ridge where the fixed-side surface of the runner and the through hole through which the return pin slides intersects is 0.1 mm or more.

3. The injection molding die according to claim 1 or 2, characterized in that at least one of the cut pin and the return pin has a cavity-side surface that constitutes the inner wall surface of the cavity.

Images