JPH0569473A - Injection blow molding method for hollow molding whose both ends are opened - Google Patents

Abstract

PURPOSE:To easily perform both cutting of a gate and removal of a sprue at a time for blow molding by forming the sprue to one side of opening end of a parison so that the sprue can be cut by the member of a core mold side. CONSTITUTION:A sprue forming part is provided in the tip of the cavity of an injection mold by connecting it to the inner edge thereof. A shoulder part 17 for forming a gate in the interval of the inner edge of the tip of the cavity is formed to the tip of a core mold 3. A gate cutting member 16 equipped with the shoulder part 17 is connected to a return means in the inside of the core mold and provided freely movably in the axial direction. A parison 9 having a sprue 19 in the end part is injection-molded. This parison 9 is closed by a blow mold 5 together with the core mold. The gate cutting member 16 is moved in the axial direction to perform both cutting of the gate and removal of the sprue 19.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of blow molding an injection-molded parison into a hollow molded product having both ends open.

[0002]

2. Description of the Related Art A molding method of this type described in Japanese Patent Publication No. 51-144 discloses that an injection mold and a core mold to be closed are divided into a fixed side and a movable mold, and they are butted against each other. Resin is injected and filled into the cavity through the gap.

Further, the parison is transferred to the blow mold after molding by removing the parison from the fixed core mold and adhering it to the movable core mold. In the blow mold, a blow core whose cross-sectional shape is almost the same as that of the fixed core die is inserted, and at the same time the parison is blow molded into a hollow molded product,
By using the blowing pressure at that time, the sprue connected around the inside of the parison is cut. The residual sprue is removed after release.

[0004]

In such a conventional technique, since the injection is performed from the inside of the molded product, a weld line is apt to be formed, and the sprue is cut by the blowing pressure.
It is necessary to mold the connecting portion between the sprue and the parison to be thin. For this reason, it is necessary to set the clearance between the pair of core-shaped butting surfaces to be the gate with high accuracy.

Further, a large pressure is required to cut the sprue so as to punch out the entire circumference of the sprue, and if one portion of the sprue remains without being cut, it becomes a protrusion inside the hollow molded product. In addition, a cover or a cap that fits with another object may cause a fitting failure, and the airtightness may be lost after the fitting.

Furthermore, since the outer diameter of the sprue including the connecting portion is almost the same as the inner diameter of the opening of the hollow molded product, it is necessary to manually take out the sprue individually, and therefore the sprue remaining after the mold release is required. There is a problem that not only is it time-consuming to remove and the treatment after the removal, but it is not suitable for mass production of a molded product having an opening with a small inner diameter.

The present invention has been conceived in order to solve the conventional problems described above, and an object thereof is to form a sprue at one opening end of a parison so that it can be cut by a member on the core mold side. This makes it easier to cut the gate and remove the sprue during blow molding, omitting the removal of the sprue after mold release, and enables mass production. New injection molding of hollow molded products with open ends. To provide a method.

[0008]

According to the present invention having the above object, a core mold having a blow passage and a return means inside is provided while a sprue molding portion is provided at the tip of a cavity of an injection mold and connected to an inner edge thereof. A gate-cutting member having a required length, which has a shoulder portion for forming a gate between the tip and the inner edge of the cavity, is provided movably in the axial direction by being connected to the returning means, and its core mold and injection The mold and the parison are injection-molded, and the parison having the sprue at the end is transferred to the blow mold together with the core mold to close the mold, and then the gate cut member is moved in the axial direction to move the gate. It is to cut and remove sprue.

Further, for the axial movement of the gate cut member, is an operating means provided by air or hydraulic pressure provided in the core mold to move the gate cut member forward and backward? Alternatively, a pulling device is installed opposite to the end of the blow mold, and the pulling device pulls the pulling device to the outside.

[0010]

[Operation] In the above method, a fine annular gate is formed between the inner edge of the tip of the cavity and the peripheral edge of the shoulder of the gate cutting member by closing the injection mold and the core mold, and the gate is inserted through this gate. The cavity and the sprue molding part are connected.

The resin injected into the injection mold is filled in the cavity from the sprue molding portion through the gate. Then, the parison is formed from the core mold to the periphery of the shoulder, and the sprue is formed around the gate cut member by connecting to the tip of the parison.

When the gate cut member is moved in the axial direction after the parison is closed in the blow mold together with the core mold, the gate is cut by the peripheral edge of the shoulder portion of the gate cut member, and the sprue is the tip of the parison. Move away from the inner edge. Furthermore, the sprue is pushed outward by the shoulder and removed.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below by taking as an example the case where a pulling device is provided opposite to a blow mold to remove sprue.

FIG. 1 schematically shows an injection stretch blow molding machine used for carrying out the present invention. Reference numeral 1 is a transfer member rotatably provided between a pair of mold clamping plates 2. Two core molds 3 are radially attached to each of the three sides.

An injection mold 4 and a blow mold 5, each having two cavities, are separately attached to both of the mold clamping plates 2 at two positions where the core mold 3 is stopped.
An injection device 6 is arranged at the position of the injection mold 4,
At the center of the end of the blow mold 5, a pulling device 7 for a gate cut member, which will be described later, is provided oppositely.

The injection mold 4 is provided with a runner 8 which communicates with a sprue molding portion, which will be described later, and two parisons 9 can be molded simultaneously by this runner 8. The parison 9 is transferred to the blow mold 5 together with the core mold 3 by the transfer member 1 which stops its rotation every 120 °, and after closing the blow mold 5 the blow mold 5 is blown into the bellows-shaped hollow molded product 10. Molded.

FIG. 2 shows the mold closed state of the core mold 3 and the injection mold 4. The injection mold 4 is internally connected to the inner edge of the tip of the cavity 11 for parison molding, and the sprue molding part is formed. Have twelve.

Inside the core mold 3, a return spring 13 is actuated to axially move back and forth, and a central shaft member 14 is provided.
And an air blowing passage 15 are provided, and the shaft member 1 thereof is provided.
A gate cut member 16 provided at the tip of the core mold 3 is connected to the core mold 4.

The gate cut member 16 is a cylindrical body of a required length having a shoulder 17 that forms a gate between the tip of the core and the inner edge of the tip of the cavity 11. The gate cut member 16 projects from the blow mold 4. Engagement device 18 with a plurality of grated ends
Have integrally.

When the core die 3 and the injection die 4 are closed, a fine annular gate is formed between the inner edge of the tip of the cavity 11 and the peripheral edge of the shoulder 17, and the cavity 11 is connected to the cavity 11 via the gate. It communicates with the sprue forming part 12.

Therefore, the resin injected from the injection device 6 into the injection mold 4 enters the sprue forming part 12 through the runner 8, passes through the annular gate, and is filled in the cavity 11. The parison 9 is formed from the core mold 3 to the peripheral edge of the shoulder portion 17, and the sprue 19 in the shape of a short cylinder is connected to the tip portion of the parison 9 and the gate cut member 1
6 is formed around the cylindrical body.

The parison 9 and the sprue 19 are formed by rotating the transfer member 1 so that the core mold 3 and the gate cut member 16 are formed.
Is transferred to the blow mold 5 together with.

FIG. 3 shows a mold closed state of the core mold 3 and the blow mold 5. When the mold is closed, the sprue 19 and the pulling device 7 are provided ahead of the shoulder portion 17 of the gate cut member 16.
Is located outside of the end face of the die opposite to the above.

The pulling device 7 is provided in the tubular main body 73, which has a tip end formed on an abutment edge 71 with the end face of the mold and a part formed on a cylinder 72, and a tubular main body 73 inserted through the cylinder 72. A hollow piston 74, an air-actuated taper pin 75 that is provided in the piston so that the piston 74 can act as a cylinder, and a bent tip is positioned in a slit 76 in the rear portion of the contact edge 71, and a tubular body 73 is provided. A pair of clamping members 77 pivotally mounted on the outside of the clamping member 77 and their return springs 78, and an air actuating member slidably fitted on the outside of the tubular main body 73 and abutting on the rear end of the clamping member 77. And an engaging ring 81 having an engaging edge 80 for receiving the engaging element 18 of the gate cut member 16 is connected to the tip of the piston 74.

After the mold is closed, the pulling device 7 moves forward until the contact edge 71 at the tip comes into contact with the end surface of the blow mold 5. This contact suppresses the end of the parison 9 and
The sprue 19 protruding from the mold end surface is taken into the tip end portion of the tubular main body 73, and the step portion of the engaging element 18 is located inside the engaging edge 80. Then, when the taper pin 75 is advanced, the tip of the taper pin 75 is inserted into the slot of the engaging element 18 to expand the engaging element 18, as shown in FIG. As a result, the gate cut member 16 is connected to the piston 74.

In this state, air is blown into the parison 9 from the blowing passage 15 to form the bellows type hollow molded article 10. When the piston 74 is moved backward after molding, only the gate cut member 16 is pulled outward against the return spring 13, and the gate is cut by the peripheral edge of the shoulder portion 17, so that the sprue 12 is removed as shown in FIG. It is cut off from the inner edge of the tip of the parison 9.

After the gate cut is completed, when the opening / closing ring 79 is moved forward by the air sent between the opening / closing ring 79 and the tubular main body 73, the rear end portions of the pair of holding members 77 are pressed, and the bent front ends are released from the slit 76. It moves onto the sprue 19 and clamps the sprue 19. When the taper pin 75 is moved backward in parallel with this, the engagement element 18 is recessed to the original state and disengaged from the engagement edge 80, and the connection between the gate cut member 16 and the tension device 7 is released. Simultaneously with this release, only the gate cut member 16 is returned to the original position by the return spring 13.

When the tubular main body 73 is moved backward and the contact edge 71 is moved away from the end surface of the mold in the state as it is, the sprue 19 is clamped by the holding member 77 to form a cylindrical body of the gate cut member 16, as shown in FIG. Is extracted from the.

After the sprue removing operation is completed, the mold is opened. The hollow molded product 10 is transferred together with the core mold 3 to the release position by the rotation of the transfer member 1.

Although the gate cutting member 16 is moved forward using the tensioning device 7 in the above embodiment, the inner space of the core accommodating the return spring 13 serves as a pressurizing chamber, and the gate cutting member 16 is moved. May move forward.

[0031]

As described above, according to the present invention, the sprue molding portion 12 is provided at the tip of the cavity 11 of the injection mold 4 so as to be connected to the inner edge thereof, while the blowing passage 15 and the returning means are provided inside. A gate cutting member 16 having a required length, which has a shoulder 17 for forming a gate between the tip of the mold 3 and the inner edge of the cavity 11, is provided movably in the axial direction by connecting to the returning means. The core mold 3 and the injection mold 5 are closed, and the parison 9 having the sprue 19 at the end is injection-molded.
After transferring the parison 9 together with the core mold 3 to the blow mold 5 and closing the mold, the gate cutting member 16 is moved in the axial direction to perform gate cutting and removal of the sprue 19. Therefore, the parison 9 is molded into the parison. The sprue is cut more reliably than when it is blown, and the sprue does not remain inside the hollow molded product.

Further, since the gate is formed by the inner edge of the tip of the cavity and the shoulder peripheral edge of the gate cutting member at the tip of the core die, the gate can be set more easily than in the case where a pair of core dies are butted against each other. Since the gate cut can be performed by pushing down the resin of the gate, the shape of the inner edge of the tip is not damaged by the gate cut.

Furthermore, the mold structure is not particularly complicated because only the gate cutting member and its returning means are provided on the core mold side, and the sprue after the gate cutting is also inserted through the gate cutting member. Since it can be removed outside the blow mold, it is not necessary to remove sprue artificially, and sprue formation and removal can be performed regardless of the size of the opening of the parison, so the inner diameter of the opening end is small. It also has the advantage that molded products can be mass-produced using the same means.

[Brief description of drawings]

FIG. 1 is a schematic vertical sectional side view of an injection blow molding machine capable of carrying out the injection blow method of the present invention.

FIG. 2 is a sectional view of a mold schematically showing a mold closed state of a core mold and an injection mold in the injection blowing method of the present invention.

FIG. 3 is a sectional view of a die schematically showing a mold closed state of a parison and a core die and a blow die.

FIG. 4 is a cross-sectional view of a part of a blow mold and a device schematically showing a connection state between a gate cut member and a tension device.

FIG. 5 is a cross-sectional view of a blow mold and a tensioning device, also schematically showing a gate cut state.

FIG. 6 is a cross-sectional view of a blowing mold and a tensioning device, which also schematically shows a sprue removal state.

FIG. 7 is a cross-sectional view of a blow mold and a tensioning device, also schematically showing the mold open state.

[Explanation of symbols]

 1 Transfer Member 3 Core Type 4 Injection Die 5 Blow Die 7 Tensioner 8 Runner 9 Parison 10 Hollow Molded Product 11 Cavity 12 Sprue 13 Return Spring 15 Blowoff Flow Path 16 Gate Cut Member 17 Shoulder 18 Engagement 19 Sprue 71 This Contact edge 73 Tubular body 74 Piston 75 Taper pin 76 Slit 77 Clamping member 79 Opening / closing ring 80 Engagement edge

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location B29C 45/57 8824-4F 49/42 2126-4F // B29L 22:00 4F

Claims (2)

[Claims] 1. A sprue molding portion is provided at the tip of a cavity of an injection mold by connecting it to an inner edge, and a spout flow path and a returning means are provided inside the tip of a core die and between the tip and an inner edge of the cavity. A gate cutting member having a required length and having a shoulder portion for forming a gate is provided movably in the axial direction by connecting to the returning means, and the core mold and the injection mold are closed to end the sprue. It is characterized in that the parison in the section is injection-molded, the parison is transferred to the blow mold together with the core mold and the mold is closed, and then the gate cutting member is moved in the axial direction to perform gate cutting and sprue removal. An injection blow molding method for a hollow molded product having both ends opened. 2. The injection blow molding method for a hollow molded product having both ends opened according to claim 1, wherein the axial movement of the gate cut member is performed by using a tension device opposite to the end of the blow mold as the gate cut member. An injection blow molding method for a hollow molded product having both ends opened, which is characterized by being connected.