JPH0550464A - Hot runner type injection mold - Google Patents

Abstract

PURPOSE:To provide a hot runner type injection mold which can prevent generation of gate marks in a projected form or stringing on a gate part of a molding at the time of mold break. CONSTITUTION:A core pin 7 for closing of a gate at the time of completion of a dwell process is incorporated into a core side mold 3 in which a product part cavity 2 is formed. The core pin 7 is supported slidably by facing on a resin casting pot of a runner bushing 5 and energized toward a runner bushing 5 side by a spring 12. Energizing force of the spring 12 is established lower than the primary injection pressure and dwell pressure of a molding machine. Therefore, since the core pin 7 is pushed downward at the time of the injection process and dwell process and the dwell pressure is released, the core pin 7 is pushed upward by receiving the energizing force of the spring 12 and closes the gate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hot runner type injection molding die.

[0002]

2. Description of the Related Art Conventionally, even after the resin has been injected into the product cavity, the resin in the runner bush is melted by the heat of the torpedo incorporated in the runner bush to solidify the product in the product cavity. There is a hot runner type injection molding die that can take out only.

[0003]

However, in the above hot runner system, after cooling is completed, the resin solidified at the gate is in contact with the resin in the molten state due to the heat of the torpedo in the runner bush, When the mold is opened, the resin in a molten state remains on the gate, and a convex gate mark and string are generated on the gate portion of the molded product. Therefore, it is necessary to finish the gate portion after taking out the molded product, resulting in an increase in the number of working steps.

The present invention has been made in view of the above circumstances, and an object thereof is to prevent hot marks and thread pulls from being generated in a gate portion of a molded product when the mold is opened. It is to provide a runner type injection molding die.

[0005]

In order to achieve the above object, the present invention provides a core-side mold having a product cavity and a runner bush for supplying a molten resin to the product cavity through a gate. A cavity side mold provided with a core pin that is provided slidably in the core side mold so as to face the runner bush and that opens and closes the gate according to the sliding; The technical means comprises an urging means for urging the core pin toward the runner bush so that the core pin closes the gate when the holding pressure after resin injection is released.

[0006]

According to the present invention having the above-described structure, the molten resin in the runner bush is injected into the product cavity through the gate, and the holding pressure is released at the end of the holding pressure process, so that the core pin is released. Receives the biasing force of the biasing means and operates to close the gate. As a result, the resin solidified in the product cavity and the resin in the molten state in the runner bush are blocked, so that the molten resin can be prevented from remaining in the gate when the mold is opened.

[0007]

EXAMPLE An example of a hot runner type injection molding die of the present invention will be described with reference to FIGS. 1 and 2. FIG. 1 is a sectional view of a hot runner injection molding die. This hot runner type injection molding die 1 has a product part cavity 2
The core side mold 3 in which the mold is formed, the mold side mold 6 including the runner bush 5 for injecting the molten resin into the product part cavity 2 through the gate 4 (see FIG. 2), and the end of the pressure holding step. It is composed of a core pin 7 (described below) for closing the gate 4 at times.

In the runner bush 5, a torpedo 8 for transmitting heat to the entire runner bush 5 is incorporated. The core side mold 3 is formed with a vertical hole 9 for accommodating the core pin 7. The central axis of the vertical hole 9 is
The runner bush 5 is provided so as to coincide with the center of the runner bush 5, and the inner diameter is gradually increased from the upper side (the upper side in FIG. 1) to the lower side. The upper end of the vertical hole 9 communicates with the product cavity 2.

A cylindrical bush 10 is inserted into the vertical hole 9 at the upper end thereof, and is fixed by a screw plug 11 screwed into the vertical hole 9 from the rear of the bush 10 (downward in FIG. 1).

The core pin 7 includes a tip side shaft portion 7a and a large diameter portion 7
It has a stepped cylindrical shape composed of b and the rear end side shaft portion 7c, is inserted from the lower side of the vertical hole 9, and the front end side shaft portion 7a is slidably inserted into the bush 10.

After inserting the core pin 7 into the vertical hole 9, a spring 12 (biasing means of the present invention) is attached to the outer periphery of the rear end side shaft portion 7c of the core pin 7. This spring 12
Is incorporated between the large-diameter portion 7b of the core pin 7 and the spacer 14 fixed to the lowermost portion of the vertical hole 9 by the bolt 13 to urge the core pin 7 upward. Spring 1
The urging force of No. 2 is set to be smaller than the primary injection pressure and the holding pressure of the molding machine (not shown).

Therefore, the core pin 7 is pushed down by the primary injection pressure and the holding pressure during the injection process and the pressure holding process, and the holding pressure is released at the end of the pressure holding process. It is pushed up by the urging force of 12. At this time, the core pin 7 is pushed up to a position where the upper end surface contacts the end surface of the runner bush 5, and the upper end portion of the tip side shaft portion 7a closes the gate 4 of the product portion gait (shown in FIG. 1). Status). It should be noted that a predetermined gap S is provided between the spacer 14 and the rear end side shaft portion 7c of the core pin 7, and the gap S is the gap S.
Sliding range.

Next, the operation of this embodiment will be described. With the start of injection, the molten resin in the runner bush 5 flows into the product cavity 2 via the gate 4 while pushing down the core pin 7 (see FIG. 2). After shifting from the injection process to the pressure-holding process, the pressure-holding process is released at the end of the pressure-holding process.
However, under the biasing force of the spring 12, the upper end surface of the core pin 7 is pushed up until it comes into contact with the end surface of the runner bush 5, as shown in FIG.

As a result, the tip side shaft portion 7a of the core pin 7 is formed.
Since the gate 4 of the product cavity 2 closes, the inside of the runner bush 5 and the product cavity 2 are cut off, and the resin solidified in the product cavity 2 after cooling is completed and the heat of the torpedo 8 in the runner bush 5 This makes it possible to prevent contact with the molten resin. As a result,
When the mold is opened, no convex gate marks are left on the gate portion of the molded product, and it is possible to prevent the occurrence of thread pulling.

In this embodiment, the upper end surface of the core pin 7 contacts the end surface of the runner bush 5 when the holding pressure is released, but as shown in FIG.
The tip shape of the core pin 7 is changed so that the runner bush 5
The same action and effect can be obtained even if the structure is fitted with.

Although the spring 12 is adopted as the urging means of the present invention, rubber, air, hydraulic pressure or the like may be used instead of the spring 12.

[0017]

According to the present invention, when the mold is opened, it is possible to prevent the generation of a convex gate mark or thread pull on the gate portion of the molded product. As a result, it is possible to omit the finishing process of the gate portion after taking out the molded product, and it is possible to reduce the number of working steps.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a hot runner type injection molding die.

FIG. 2 is a sectional view showing an operating state of a core pin.

FIG. 3 is a cross-sectional view of essential parts showing a modified example of the present invention.

[Explanation of symbols]

 1 Hot runner type injection molding mold 2 Product part cavity 3 Core side mold 4 Gate 5 Runner bush 6 Cabinet side mold 7 Core pin 12 Spring (biasing means)

Claims (1)

[Claims] 1. A core-side mold in which a) a product-portion cavity is formed, b) a mold-side mold including a runner bush for supplying molten resin to the product-portion cavity through a gate, and c) the A core pin that is slidably provided in the mold on the core side so as to face the runner bush and that opens and closes the gate in accordance with the sliding; d) Releasing the holding pressure after resin injection into the product cavity. A hot runner type injection molding die comprising: a biasing unit that biases the core pin toward the runner bush so that the core pin closes the gate when the core pin is closed.