JPH0732459A - Method of controlling wall-thickness of parison - Google Patents

Abstract

PURPOSE:To control wall-thickness positively without any obstacle by providing a movable housing being freely shifted by a hydraulic cylinder, and setting a resin pressure sensor at the resin discharge port of the housing, and thus causing the movable housing to shift by the hydraulic cylinder keeping resin pressure constant. CONSTITUTION:There is formed a dam-lip portion that defines a passage in the peripheral direction of a core metal 16 with a convergence 27 opened for putting the ends of manifold 20 together. Employed on the resin passage 18 between the dam-lip portion and the manifold 20 is a dies 10 having a round portion 29 formed thereon to have a passage being shallower than the depth of the manifold and deeper than the dam-lip portion. A bank of sensors 35 are arranged at the side of a die housing 12 side near a resin discharge port 28 at the bottom of the dies. By the data of resin pressure obtained by these sensors, a movable housing 37 forming the resin discharge port 28 is moved by a hydraulic cylinder 36 in the radial direction, thereby uniforming a distribution of resin pressure in the peripheral direction. Thus, a uniform wall-thickness of parison can be obtained in the peripheral direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling the thickness of a parison which allows a parison to be uniformly injected in the circumferential direction of a die in a blow molding machine.

[0002]

2. Description of the Related Art Conventionally, a parison circumferential wall thickness control device for making the wall thickness of a blow molded product uniform has been used.

[0003]

However, in order to make the wall thickness of the molded product ideal, it is necessary to control the wall thickness of the parison in the circumferential direction. It was not possible to reliably control the wall thickness in the circumferential direction without any obstacle.

An object of the present invention is to provide a method for controlling the wall thickness of a parison, which pays attention to the above-mentioned conventional problems and can reliably control the wall thickness in the circumferential direction of the parison without any obstacle.

[0005]

In order to achieve the above object, a method for controlling the thickness of a parison according to the present invention is to insert a core metal into a die housing to form a resin passage, and to form an extruder in the resin passage. Open the resin inlet from the side,
A manifold is formed that branches from the surface of the core metal on the resin inlet side to the left and right in the circumferential direction, has a passage cross-sectional area that decreases toward the anti-resin inlet side of the core metal, and is curved in the extrusion direction, and joins the manifold ends. To form a merging portion, and the merging portion is opened to form a dam lip portion that forms a shallow passage along the circumferential direction of the core metal, and the entire resin passage between the dam lip portion and the manifold is formed. Based on the resin pressure data obtained by arranging a plurality of pressure sensors on the die housing side near the resin discharge port under the die, using a die in which a land having a passage shallower than the manifold depth and deeper than the dam lip is formed. By moving the movable housing that forms the resin discharge port in the radial direction with a hydraulic cylinder, the resin pressure distribution in the circumferential direction is made uniform, and even distribution in the circumferential direction is achieved. And so as to obtain a down wall thickness.

[0006]

According to the above construction, the resin flows into the cylindrical passage in the die for each shot from the resin inflow port, which flows down along the manifold and simultaneously overflows to the land portion. The merging portion of the manifold is formed in the dam lip portion, from which the resin flows down, and at the same time, the land portion also flows down to the dam lip portion. The land height from the dam lip portion gradually decreases in the manifold path direction, and the overflow flow rate from the manifold becomes almost equal along the path direction from the resin inlet, and the resin is evenly distributed over the entire circumference of the die. It is injected around. At the time of injection, the ejection die gap is adjusted while comparing the wall thickness swell amounts of the parison based on the resin pressure data from a plurality of pressure sensors arranged at equal intervals near the parison ejection port.

[0007]

EXAMPLES Specific examples of blow molding dies according to the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a structural view of a blow molding die according to an embodiment, FIG. 2 is a cross sectional view taken along line A--A in FIG. 1, and FIG. 3 is a cross sectional view taken along line B--B in FIG. FIG. 4 is a vertical cross-sectional view of a double-coat hanger type blow molding die provided with a resin pressure sensor, and FIG. 5 is a vertical cross-sectional view of a conventional blow molding die provided with a resin pressure sensor.
The die 10 has a die housing 12 made of a rectangular block, and a through hole 14 having a substantially circular cross section is formed along the vertical center line thereof. The through-hole 14 has a structure in which the inner diameter is gradually reduced from the middle of the through-hole 14 to the lower end surface of the housing 12.
2 is opened at the lower end surface.

A through hole 14 is formed in the housing 12.
The core metal 16 having a smaller diameter is inserted, and the core metal 1
6 between the outer peripheral surface of 6 and the inner peripheral surface of the through hole 14
Is formed. The lower end of the cored bar 16 is formed with a narrowed end corresponding to the reduced diameter portion of the through hole 14.

A core metal 16 is provided at the lower end of the die 10.
A parison control core 16b is mounted so that it can be moved in and out. A mandrel lip 34, which faces the opening of the through hole 14 and forms a circular ring-shaped resin discharge port 28 between the opening of the through hole 14 and the front end of the parison control core 16b, is integrally provided. . Therefore, the die gap of the resin discharge port 28 can be arbitrarily changed by changing the in / out amount of the parison control core 16b.

The die gap is changed by the die housing 1.
2 is made possible by driving a control cylinder 30 fixed to a support plate 25 on a column 24 standing upright, and therefore a parison control rod 32 for connecting the control cylinder 30 and the parison control core 16b to the core. It penetrates the gold 16.

Further, the molten resin supplied to the resin inlet 21 from the resin passage 22 connected to the extruder 23 provided on the peripheral wall of the die housing 12 is first circumscribed from the surface of the core metal 16 on the resin inlet 21 side in the circumferential direction. A manifold 20 having a semicircular cross section is formed which is branched leftward and rightward, and is gradually curved in the extrusion direction with a predetermined curvature while gradually reducing the passage cross-sectional area toward the anti-resin inlet 21 side of the core metal 16 at a predetermined rate. ing. The end of the manifold 20 is formed so as to join with the symmetrical manifold 20 on the opposite surface side at a position of approximately 180 degrees from the resin inlet 21.

Corresponding to this confluence portion 27, a dam lip portion 31 which forms a shallow passage along the circumferential direction of the core metal 16 is formed. The dam lip portion 31 is provided corresponding to the throttle passage portion of the resin passage 18, and is set so that the gap between the dam lip portion 31 and the through through hole 14 of the housing 12 is narrowed so that the flow passage resistance is uniform over the entire circumference. ing.
In this case, the merging portion 27 is connected and merged so that the manifolds 20 having merging symmetry are in contact with the line along the axis of the cored bar 16. As a result, the flow lines of the molten resin flowing down the manifold 20 become parallel at the merging portion.

Further, the entire tubular passage extending from the lower edge of the manifold 20 to the dam lip portion 31 is the manifold 2.
It is shallower than the passage cross-sectional depth of the portion 0, and the dam lip portion 3
Land portion 29 forming a passage deeper than the depth of the flow passage in one portion
Is formed. This is formed by adjusting the scraping depth of the outer periphery of the cored bar 16 as described above.

In the present invention, with the above structure as a basic structure,
As shown in FIG. 1, a movable housing 34, which constitutes a part of the resin passage 18 and the resin discharge port 28, is engaged with the recess at the lower part of the die housing 12, and the die housing 12
A plurality of hydraulic cylinders 36 (arranged at equal intervals in this embodiment) mounted on the outer periphery of the lower part of the movable housing 34 are moved forward and backward and left and right so that the resin pressure obtained by the resin pressure sensor 35 becomes constant. Can be activated.
A resin pressure sensor 35 for measuring the resin pressure in the resin passage 18 is arranged near the circular ring-shaped resin discharge port 28 of the die 10 on the movable housing 34 side. In this embodiment, for example, as shown in FIG. 2, four resin pressure sensors 35 are radially arranged at equal intervals, and the tip of the resin pressure sensor 35 does not interfere with the molten resin flowing down the resin passage 18. Is attached so as to form the same wall surface as the through hole 14. In the present embodiment, four resin pressure sensors 35 are provided near the resin discharge port 28, but the number is not limited to this, and the number of resin pressure sensors 35 may be changed as necessary.

The operation of the blow molding die portion configured as described above will be described. The resin that has flowed in from the resin inflow port 21 branches left and right in the manifold 20 and flows down to reach the merging portion 27, and at the same time as the branch flow down, it overflows from the lower edge of the manifold 20 to the land portion 29, and the resin passes through the resin passage. It will flow uniformly over the entire circumference of 18. And
Since the groove cross-sectional area of the manifold 20 is set to be gradually reduced, the pressure distribution in the circumferential direction becomes uniform and the dam lip portion 31 flows down in a state of being re-adjusted and the parison 33 is discharged from the resin discharge port 28. It is ejected.

When the parison 33 having a uniform wall thickness in the circumferential direction is injected, the pressure distribution in the circumferential direction is obtained based on the data of the resin pressure distribution in the circumferential direction obtained by the resin pressure sensor 35 shown in FIG. Move the movable housing 37 back and forth by the hydraulic cylinder 36 so as to be even,
The parison 33 having a uniform wall thickness in the circumferential direction is ejected.
Before the injection of the parison 33, the correlation between the resin pressure data and the swell amount of the wall thickness of the parison 33 is obtained for each type of resin. When the desired thickness of the parison 33 is determined, the control cylinder 30 is moved up and down so as to change the die gap of the resin discharge port 28 under the constant resin extrusion pressure from the extruder 23, and the desired resin pressure is obtained. In this way, the parison 33 having a uniform wall thickness is ejected from the resin discharge port 28 in the circumferential direction. In this embodiment, FIG.
As described above, the case where the resin pressure sensor 35 is provided in the single-coat hanger type blow molding die is described. However, the double-coat hanger type blow molding die shown in FIG. The resin pressure sensor 35 can be used for the blow molding die.

[0018]

As is apparent from the above description, in the thickness control method for a parison according to the present invention, a core metal is inserted into a die housing to form a resin passage, and an extruder is provided in the resin passage. The resin inflow port is opened from the side, and the cross-sectional area of the passage is reduced from the surface of the core metal on the side of the resin inflow side to the left and right in the circumferential direction toward the side opposite to the resin inflow port of the core metal, and it is curved in the extrusion direction. A manifold is formed, the ends of the manifold are joined to form a joining portion, and a joining portion is opened to form a dam lip portion that forms a shallow passage along the circumferential direction of the core metal. The dam lip portion and the manifold are formed. A die in which a land portion having a passage that is shallower than the manifold depth and deeper than the dam lip portion is formed is used for the entire resin passage between the die and the die near the resin discharge port below the die. By moving the movable housing that forms the resin discharge port in the radial direction with a hydraulic cylinder based on the resin pressure data obtained by arranging multiple pressure sensors on the housing side, the resin pressure distribution in the circumferential direction is made uniform, and Since the parison thickness is uniform in the direction, the thickness of the parison can be controlled in real time, so that the parison having the uniform thickness in the circumferential direction can be easily obtained.

[Brief description of drawings]

FIG. 1 is a structure of a blow molding die according to an embodiment of the present invention.

FIG. 2 is a cross sectional view taken along line AA of FIG.

FIG. 3 is a cross-sectional view taken along the line BB of FIG.

FIG. 4 is a vertical sectional view of a double-coat hanger type blow molding die provided with a resin pressure sensor.

FIG. 5 is a vertical cross-sectional view in which a resin pressure sensor is arranged in a conventional blow molding die.

[Explanation of symbols]

 10 dies 12 dies housing 16 core metal 16a parison control core 18 resin passage 20 manifold 27 merging portion 28 resin discharge port 29 land portion 30 control cylinder 33 parison 35 resin pressure sensor 36 hydraulic cylinder 37 movable housing

Claims (1)

[Claims] 1. A core metal is inserted into a die housing to form a resin passage, a resin inlet from the extruder side is opened in the resin passage, and a left and right circumferential direction is provided from a surface of the core on the resin inlet side. To form a manifold having a passage cross-sectional area reduced toward the anti-resin inlet side of the core metal and curved in the extrusion direction, and the manifold ends are joined to form a joining portion. A land is formed that has a dam lip portion that is opened and forms a shallow passage along the circumferential direction of the core metal, and the entire resin passage between the dam lip portion and the manifold has a passage that is shallower than the manifold depth and deeper than the dam lip portion. The resin discharge port is formed based on the resin pressure data obtained by arranging multiple pressure sensors on the side of the die housing near the resin discharge port at the bottom of the die, using a die that has formed parts A method for controlling a wall thickness of a parison, characterized in that the movable housing is moved in a radial direction by a hydraulic cylinder so as to make the resin pressure distribution in the circumferential direction uniform and obtain a uniform parison thickness in the circumferential direction.