JPH06262649A - Runnerless mold - Google Patents

Abstract

PURPOSE:To facilitate the separation of a runner part and a molding by forming the runner of a manifold so that the cross-sectional area of the leading end surface thereof has a throttled shape and providing a sub-runner between the runner and a cavity and providing a runner lock permitting the adhesion of the molding material in the sub-runner to the surface of a movable mold. CONSTITUTION:The manifold 1 fixed to a fixed mold A holds an injected molding material to a molten state in a sprue 4 and a runner 5. The leading end part of the runner 5 is formed into such a shape that the cross-sectional area thereof is throttled and the sub-runner 14 communicating with a cavity 12 is provided so as to be continued to the runner 5 and an undercut runner lock 15 is provided to the molding surface of the movable mold B of the sub-runner 14. When the molds A, B are opened after the molding material in the cavity is solidified, a molded product and the sub-runner 14 are bonded to the movable mold B to be separated from the runner 5. By providing the sub-runner 14, the temp. control of the manifold 1 and the cavity 12 becomes easy.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a runnerless molding die used for injection molding of synthetic resin molding material, etc., and an object thereof is to provide a mold in which the molding material of the runner part and the molded product can be easily separated. And

[0002]

2. Description of the Related Art In injection molding, a runnerless molding die is often used to reduce waste of molding material. The runner-less molding die eliminates the loss of the molding material in the flow path (sprue, runner) where the molten molding material is injected into the cavity that forms the molded product. Independently of the above, the fluidity of the molding material is maintained and it is used for the next molding shot. A conventional runnerless molding die has a structure as shown in FIG. A is a fixed mold, and B is a movable mold. Further, (1) is fixed to the fixed side mold A by a manifold. (2) is a heater hole or heat medium flow path for temperature control, (3) is an air gap for insulating the manifold from other molds, (4) is a sprue, and (5) is a runner.
(6) shows a cavity and (7) shows a gate. (8) and (9) are protruding pins.

In such a conventional runnerless mold, when the molding material is injected into the cavity and then the mold is opened, the molding material in the cavity and the molding material in the runner portion are separated at the gate portion, and therefore, the cavity is Since they are close to the runner and there is a temperature difference between them, it is difficult to control the temperature of each other, resulting in problems such as insufficient solidification (or hardening) of the molded product or solidification (or hardening) of the runner. May occur. Therefore, a part of the runner is provided outside the manifold and a certain distance is provided between the cavity and the manifold to facilitate temperature control of both. However, in this case, when the mold is opened, the runner opening of the manifold cannot be separated from the cavity side runner well, and the resin may leak from the runner opening, which causes the material to fill the cavity in the next shot. In some cases, there was variation in the amount, which could cause molding failure, or even make it impossible to perform mold clamping.

[0004]

DISCLOSURE OF THE INVENTION The present invention provides a runner-less molding die which is easy to separate a molded product from a manifold runner portion in injection molding, has excellent continuous moldability, and is resistant to molding defects. Is.

[0005]

SUMMARY OF THE INVENTION The present invention includes a manifold for holding an injected molding material in a molten state in a sprue and a runner, and a cavity for forming a molded article, and a runner tip portion of the manifold has a small cross-sectional area. It has a narrowed shape, a sub-runner is provided between the runner of the manifold and the cavity, and a runner lock for attaching the molding material in the sub-runner to the movable-side mold is formed on the movable-side mold surface of the sub-runner. The present invention relates to a runnerless molding die characterized in that A runnerless mold of the present invention will be described with reference to the drawings. FIG. 1 is a schematic sectional view of a runnerless molding die of the present invention. FIG. 2 is an enlarged cross-sectional view of the molding material flow path from the runner to the cavity,
(A) is a state in which the molding material is filled in the cavity, (b)
Shows a state where the mold is opened, and (c) shows a state in which the molded product and the Labrana portion are projected. A is a fixed mold, and B is a movable mold. (1) is a manifold, which is fixed to the fixed mold A. (2) is a heater hole or heat medium flow path for temperature control, (3) is an air gap for insulating the manifold, (4) is a sprue, and (5) is a runner. (11) is the tip of the runner of the manifold, which has a small cross-sectional area. (12) is a cavity, (13) is a gate, (14) is a sub-runner continuing from the runner of the manifold, and (15) is an undercut-shaped runner lock provided on the movable mold surface of the sub-runner.
(16), (17) and (18) show protruding pins, respectively. Next, the case of injection molding using the runnerless molding die of the present invention will be described. The manifold (1) is controlled at a temperature at which the molding material in the manifold does not solidify (or harden) and maintains sufficient fluidity. This temperature control is performed by the heater or the heat medium in the heater hole or the heat medium flow path (2). After the mold is clamped at the time of molding, the molten molding material is injected by the molding machine cylinder, passes through the sprue (4), runner (5), and sub-runner (14), and then fills the cavity (12) through the gate (13). To be done. After the molding material in the cavity is solidified (or cured), the mold is opened. At this time, the material of the molded product and the sub-runner (14) in the cavity (12) adheres to the movable mold B and is separated from the material of the runner (3) of the manifold. The material of the sub-runner (14) is completely attached to the movable mold B by the runner lock (15),
Since the runner tip (11) of the manifold has a shape with a narrowed cross-sectional area, the material of the runner and the material of the sub-runner can be separated without problems, and the runner tip (11)
There is no leakage of material. Next, the protruding pins (16), (1
By 7), the material of the molded product and the sub-runner part is taken out from the mold. Then, the mold is clamped and the next shot is molded. At this time, the molding material in the manifold is filled in the cavity. Although the gate shape shows a side gate in the drawing, a submarine gate or the like can also be adopted.

[0006]

In the runnerless molding die of the present invention,
Since the tip end of the manifold runner has a narrowed cross-sectional area, a sub runner is provided between the manifold runner and the cavity, and the sub runner has a runner lock formed on the movable die surface, The molding material in the manifold is separated from the molding material of the molded product and the sub runner portion without any problem, and there is no material leakage from the runner. Further, since the sub-runner is provided, the manifold and the cavity have a certain distance, so that the temperature control of the both becomes easy. By providing a heat medium passage or a heater hole between the manifold and the cavity, or using a mold material having a relatively small heat conductivity, the temperature control can be further facilitated.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a runnerless molding die of the present invention.

FIG. 2 is an enlarged cross-sectional view of a molding material flow passage from the runner to the cavity in FIG. 1, where (a) is a state in which the cavity is filled with the molding material, (b) is a mold open state, and (c) is a mold opening state. Shows a state in which the molded product and the Labrana part are projected.

FIG. 3 is a schematic sectional view of a conventional runnerless molding die.

[Explanation of symbols]

 A Fixed-side mold B Movable-side mold 1 Manifold 2 Heater hole or heat medium flow path 3 Air gap 4 Sprue 5 Runner 6 Cavity 7 Gate 8, 9 Projecting pin 11 Manifold runner tip 12 Cavity 13 Gate 14 Sub-runner 15 Runner lock 16,17,18 protruding pin

Claims (1)

[Claims] 1. A sprue and a runner have a manifold for holding the injected molding material in a molten state and a cavity for forming a molded product, and the runner tip end portion of the manifold has a shape in which a cross-sectional area is narrowed down. A sub-runner is provided between the runner and the cavity,
The runner-less molding die is characterized in that a runner lock for adhering the molding material in the sub-runner to the movable-side mold is formed on the movable-side mold surface of the sub-runner.