JPS6280009A - Control device for parison thickness at head for blow molding - Google Patents

Abstract

PURPOSE:To obtain the flow molding product with uniform section by controlling the thickness of a parison, while sliding the insert facing a slit along the groove of a flow pin by an actuator, and enlarging or minimizing a part of the slit. CONSTITUTION:During the extrusion of molten resin, when a cylinder 11 is operated and a movable ring 9 is pulled up, an insert 12 elevated along the groove 8 of a flow pin 7. Therefore, the taper part 13 of the insert 12 is moved upward in parallel, whereby the slit 17 at the portion with the piece is partially enlarged. The flow speed of the molten resin passing through the slit 17 of the enlarged portion becomes larger. The molten resin is extruded in the atmosphere, while it has elastic strain larger than that of the molten resin passing through the slit 17 of outer portion. Because the swell ratio of the extruded parison 22 is varies with the difference of elastic strain, the swell of the molten resin passing through the slit of the enlarged portion becomes larger, thereby molding the part 23 with large thickness. When the cylinder 11 is operated and the insert 12 is restored to its original position, the thickness of the parison 22 becomes uniform.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention is a blow molding head that extrudes molten resin as a pipe-shaped parison to mold various containers such as tanks and drums. I made it possible to change the thickness. This invention relates to a parison wall thickness control device for a blow molding head.

[Prior Art] An example of a conventionally used blow molding head will be explained with reference to FIG.
A die C is attached to the lower end of the head body a.

A core d is attached to the center of the head body a, and a flow pin e is fitted to the upper outer periphery of the core d. A slit is formed between the head body a and the outer periphery of the flow pin e, the upper end of the slit f is connected to the molten resin inlet, and the lower end of the slit is formed between the die C and the lower end of the core d. The nozzle output loss slit 9 is connected to the nozzle output loss slit 9, which is a perfect circle with a uniform width as shown in FIG.

The molten resin that has entered the molten resin tube passes through the slit [, and is extruded from the nozzle output loss slit q as a parison h. Since the pressure of the molten Fa resin between the molten resin inlet of the slit and the rear side of the slit shown in Fig. The thickness of the parison h extruded from the departmental rotor is not uniform! As shown in Figure T7, the parison h has an uneven thickness. In order to prevent such deviation in the wall thickness of the parison h, the die C is
By cutting a part of the inside of the core d, or by cutting a part of the outer periphery of the core d as shown in Fig. 10 to widen a part of the nozzle production loss slit Q, a thick part is formed in the parison h as shown in Fig. 11. i
was used to form a parison without thin-walled parts.

Furthermore, as shown in Fig. 12, the die C is made into a flexible ring, and force is applied to the die C by actuators j placed on both sides of the die C, thereby deforming the circular die into an oval die. , a method for controlling the wall thickness in the circumferential direction of the parison h by deforming the circular nozzle exit loss slit 9 formed around the core d into a shape with a different thickness to form a thick wall portion i. It is being

[Problems to be Solved by the Invention] The method of controlling the wall thickness of the parison h by cutting either or both of the die C and the core d, as explained in FIGS. 8 to 11, It was necessary to test the thickness of the eel several times, and the parison H had to be thick from the beginning to the end, making it impossible to control the thickness in the length direction.

In addition, in the blow molding head using the flexible ring die C shown in FIG. 12, the die C returns to its original shape when subjected to an external force from the actuator J.
This device is more advanced than the above-mentioned devices because it can control the wall thickness in the vertical direction of the parison H, but it is necessary to make a die C that fits each type of molded product, and unless it is made of a special alloy, it will not be elastic. The production cost is high and the number of man-hours is increased because of the lack of the molded product.Furthermore, since the thick interior of the molded product always has two symmetrical parts, there are problems such as unnecessary thick parts depending on the type of molded product. .

In the present invention, the parison extruded from the blow molding head is extruded by thickening the corresponding part so that the molded product does not become locally thin during molding, so that the blow molded product without uneven thickness can be produced by 1q. It is something.

[Means for Solving the Problems] The present invention provides a flow pin provided within a head body, a slit formed between the head body and the outer periphery of the flow pin,
The flow pin includes a groove provided in the vertical direction on the outer periphery of the flow pin, a piece fitted in the groove and facing the slit, and a cutter that slides the piece along the groove to enlarge or reduce a part of the slit. Control of parison wall thickness of blow molding head [
This is one device.

[Function] When the piece facing the slit is slid along the groove by the actuator, the piece recedes or protrudes, enlarging or contracting a portion of the slit, and controlling the wall thickness of the parison.

[Implementation example j Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

In FIG. 1, a molten resin tube 2 is provided on the upper side of the head body 1, and a cylindrical plunger is fixed in the hollow interior of the head body 1 so as to be concentric with the head body 1. A guide 3 is provided, and the lower end of the plunger guide 3 is formed with a taper 4 whose diameter becomes smaller at the bottom. Inside the plunger guide 3, there is a mandrel 5.
The shaft 5 is moved vertically by a vertical parison control cylinder 6.

A flow pin 7 is fixed to one lower end of the mandrel 5, and the outer periphery of the flow pin 7 is provided with a vertical groove 8, as shown in FIG. Further, a movable ring 9 is provided between the small diameter portion of the lower part of the mandrel 5 and the flow pin 7 so as to be able to closely slide in the vertical direction, as shown in FIGS. 1 and 2. A connecting bar 10 of the movable ring 9 is slidably passed through the mandrel 5 and is moved vertically together with the movable ring 9 by a circumferential parison control cylinder 11 provided as an actuator. A piece 12 is fixed to the movable ring 9, and this piece 12 is slidably fitted into the groove 8 of the flow pin 7 described above. A taper 13 having the same slope as the taper 4 at the lower end of the plunger guide 3 is formed on the lower outer surface of the bridge 12.

Ring plunger 1 is installed on the outside of plunger guide 3.
The ring plunger 14 is fitted in such a way that it can slide tightly, and the ring plunger 14 is moved vertically by the injection cylinder 15. ring plunger 14
An annular passage 16 is formed between the head body 1 and the head body 1, the upper end of the annular passage 16 is connected to the molten resin inlet 2, and the lower end of the annular passage 16 is connected to the lower outer periphery of the head body 1 and the flow pin 7. It is connected to a slit 17 formed between them.

A core 18 is fixed to the lower surface of the flow pin 7, and a die 19 is sealed to the lower side of the head body 1 by a retaining ring 20. The slit 17 is connected to the nozzle output loss slit 21 by the core 18 and the die 19.

When the ring plunger 14 is raised by the injection cylinder 15 shown in FIG.
The volume of the lower annular passage 16 is increased, and the molten resin is stored there. When the ring plunger 14 is pushed down, the molten resin is forced out through the slit 17 and the nozzle exit slit 21, forming a parison 22 having a predetermined thickness and diameter. During this extrusion process, when the taper 4 of the plunger guide 3 and the taper 13 of the piece 12 are lined up, the slit 17 becomes a uniform gap over the entire circumference,
The parison 22 is extruded with the width of the nozzle output loss slit 21 regulated by the core 18 and die 19, ensuring uniform thickness distribution.

During extrusion of the molten resin, when the circumferential parison control cylinder 11, which is an actuator, is activated and the movable ring 9 is pulled up via the connecting bar 10, the piece 12 fixed to the movable ring 9 moves into the groove 8 of the flow pin 7. rise along. Therefore, the taper 13 of the piece 12 is translated upward, and the slit 17 where the piece 12 is located is partially enlarged as shown in FIG. The flow velocity of the molten resin passing through the slit 17 in the enlarged part increases, and the molten resin passes through the slit 17 in the other part that is not enlarged.
The molten resin passes through the nozzle output loss slit 21 and is extruded into the atmosphere while having a larger elastic strain than the molten resin passing through the nozzle output loss slit 21.

Since the swell ratio of the parison 22 pushed out into the atmosphere differs depending on the magnitude of elastic strain, the slit 1 in the enlarged part
The swell of the molten resin passing through 7 becomes larger, and a thick portion 23 is formed as shown in FIG. When the circumferential parison control cylinder 11 is actuated to return the piece 12 together with the movable ring 9 to its original position, the parison 22 becomes uniform in thickness.

In the illustrated embodiment, two pieces 12 are mounted on the movable ring 9.
is fixed, and the two pieces 12 move vertically at the same time, but the movable ring 9 is not provided, and each piece 12 has a connecting bar 10 and a circumferential parison control cylinder 11 which is an actuator. If set, piece 12
Each can be moved individually. Further, the number of pieces 12 and grooves 8 is not limited to two, but can be increased or decreased.

[Effect of the invention 1] Conventionally, it was necessary to cut a part of the die or core or use a flexible ring die for each type of molded product, but the present invention can adjust the wall thickness of various molded products with one device. can be controlled.

Furthermore, since the size of the slit is changed on the inner side of the parison, the surface of the parison is smooth and the molded product has a beautiful appearance and high commercial value.

Furthermore, it is also possible to provide a plurality of grooves on the outer periphery of the flow pin and move the pieces fitted in each groove independently, thereby making it possible to optimally control the wall thickness depending on the molded product.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of an embodiment of the present invention, FIG. 2 is a sectional view taken along II-I of FIG. 1, and FIG. 3 is a sectional view taken along
4 is a sectional view taken along IV-IV in FIG. 1, FIG. 5 is a vertical sectional view of an example of the conventional device, FIG. 6 is a sectional view taken along Vl-Vl in FIG. -VN sectional view, Figure 8 is a side view of the conventional device, Figures 9 and 10 are IX-■ sectional views in Figure 8, Figure 11 is XI-XI sectional views in Figure 8, and Figure 12. is a sectional view similar to FIG. 9 of another example of the conventional device. In the figure, 1 is the head body, 1 is the flow pin, 8 is the groove, 11
is the circumferential parison control cylinder, 12 is the piece,
17 indicates a slit. Figure 1

Claims (1)

[Claims] 1) A flow pin provided within the head body, a slit formed between the head body and the outer periphery of the flow pin, a groove provided in the vertical direction on the outer periphery of the flow pin, and a flow pin fitted into the groove and facing the slit. A parison wall thickness control device for a blow molding head, comprising: a piece; and an actuator that slides the piece along the groove to enlarge or contract a part of the slit.