JP2795367B2 - Blow molding machine with flat dies - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for preventing die lip deformation of a flat die having a flat annular shape in a blow molding machine.

[0002]

2. Description of the Related Art In a blow molding machine, a molten resin supplied from an extruder is formed into a cylindrical molten resin cylinder called a parison by a die having a ring-shaped resin discharge port, and this is sandwiched between molds. Thereafter, a gas such as air is blown into the parison and cooled to form a hollow product.

[0003] The general structure of a conventional parison injection die used in such a blow molding machine is such that a mandrel is inserted into a die housing to form a cylindrical resin passage, and a die lip attached to the tip end of the mandrel. The hollow parison is injected from a ring-shaped resin discharge port formed so as to face a nozzle opened on the lower surface of the die housing. The shape of the resin discharge port of such a die is determined according to the molded product. Generally, the die is formed in a circular ring shape and a parison having a cylindrical cross section is injected. However, depending on the shape of the mold cavity, the die is flat. A parison having a cross section may be desirable, and in recent years, it has been applied to a flat plate-like structure such as a vehicle door or panel, or a bumper or a spoiler. As a flat shape, a flat parison has been formed by injection molding.

[0004]

The parison injection dies in a conventional blow molding machine have a fixed resin discharge port shape according to a preset product.
Therefore, every time the product shape changes, the required parison shape also changes, and accordingly the shape of the resin discharge port is changed so that individual products, for example, parisons corresponding to deep and thin objects can be injected. Action is required. In such a case, conventionally, in order to obtain a parison suitable for a molded product,
It is common practice to replace the entire die each time a molded product is different, or to use a dedicated blow molding machine for each molded product.

[0005] If the shape and size of the molded product are different, if the entire die is to be replaced every time the molded product is different, replacement of a heavy die is not easy and involves a risk. Further, there is a drawback that the operation rate of the blow molding machine is reduced when the molding is performed by a dedicated blow molding machine for each molded product.

In order to solve such a problem, there is a method in which only the lower die housing and the lower mandrel are replaced to change the parison size. Normally, a flat die having a basic shape is configured so that the pressure loss of the resin passing through the resin flow path at the lower major axis and the minor axis at the lower part of the die is the same in the circumferential direction. Is possible. However, when the lower part of the die, that is, the lower die housing and the lower mandrel are replaced with dies which are larger or smaller than usual, the lengths of the resin flow paths on the long diameter side and the short diameter side of the flat die necessarily change. As a result, the pressure loss of the resin passing through the resin flow path varies in the circumferential direction, and the parison extruded from the die has a poor diameter on the long diameter side, and the resin flows only on the short diameter side, resulting in an uneven parison. There was a problem that the desired parison molding was difficult.

[0007] Further, since the flat die has a flat shape, it is necessary to prevent the high stress generated at the longer diameter end of the die housing member and the large displacement (deflection) generated at the shorter diameter side of the die housing member. It is necessary to manufacture the housing member from a material having a high rigidity and a high strength. For this reason, increasing the thickness only in the lower region of the die housing results in an enormous weight of the entire die, and furthermore, an enormous heater capacity is required to heat up the die, and a long heating time is required. There was a problem.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned drawbacks of the prior art, and a blow molding machine having a flat die capable of easily obtaining a parison having an appropriate thickness and smoothly changing a resin. The purpose is to provide.

[0009]

In order to achieve the above object, in a blow molding machine having a flat die according to the present invention, a resin passage is formed by inserting a core having a core in the center of the lower end of a die housing. A resin inlet from the side of the extruder is opened in the resin passage, and the cross section of the passage is branched right and left in the circumferential direction from the surface of the core metal on the resin inlet side, and the cross-sectional area of the passage toward the anti-resin inlet side of the core is reduced. Forming a manifold that is reduced and curved in the extrusion direction, joins the ends of the manifold to form a junction, and further separates the lower end of the die housing from the core to form a molten resin passage; The die lower plate has a horizontal width dimension longer than the horizontal width dimension of the die housing.

[0010]

According to the above construction, the resin flows into the cylindrical passage in the die for each shot from the resin inlet, but flows down along the manifold and simultaneously overflows the land. The junction of the manifold is formed at the dam lip portion, from which the resin flows down, and at the same time, the resin flows down from the land to the dam lip portion. The height of the land from the dam lip is gradually reduced in the direction of the manifold path, and the amount of overflow from the manifold becomes substantially equal along the path from the resin inlet, and the resin is uniformly distributed over the entire circumference of the die. Around the parison, a parison with a uniform thickness is drooped from the resin discharge port. In order to prevent the die gap from being deformed by the resin pressure at the time of injection at the lower part of the die housing,
A die lower plate is provided in which one side of the width dimension is 1.5 to 2.5 times the value when the inner minor axis of the die lip area is set as a reference dimension, and the other side is 2.5 to 4 times the reference size. This reduces the weight of the entire die.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to specific embodiments of a blow molding machine having a flat die according to the present invention.

FIG. 1 and FIG. 2 show the structure of a flat die according to one embodiment. As shown in the figure, the die 10 has a die housing 12 whose outer peripheral surface is formed in a rectangular shape in plan view and whose inner peripheral surface is formed in an oval or elliptical shape. Dice housing 12a
And a lower die housing 12b, which are detachably connected by fastening bolts or the like. A through-hole 14 having a substantially circular cross section is formed along a vertical center line of the die housing 12. Such a through-hole 14 is opened at the lower end surface of the housing 12 in a state where the equivalent diameter is gradually reduced from the middle to the lower end surface of the housing 12.

A through-hole 14 is provided in the housing 12.
The core 16 having a smaller diameter is inserted and the core 1
6 and an inner peripheral surface of the through hole 14.
Is formed. The lower end of the cored bar 16 is formed by drawing the tip in accordance with the reduced diameter portion of the through-hole 14.

At the lower end of the die 10, a metal core 16 is provided.
The core 15 is mounted so as to be able to enter and exit from. The leading end of the core 15 faces the opening of the through-hole 14, and the through-hole 1
A mandrel lip 29 forming a circular ring-shaped resin discharge port 17 with the opening 4 is integrally provided.
Therefore, the die gap of the resin discharge port 17 can be arbitrarily changed by changing the amount of the core 15 in and out.

The die gap can be changed by using the die housing 1.
2 is enabled by driving a control cylinder 30 fixed to a support plate 25 on a support post 24 erected on the control cylinder 30.
The parison control rod 32 connecting the
6.

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 removed from the surface of the core 16 on the resin inlet 21 side in the circumferential direction. A manifold 20 having a semicircular cross-section, which branches right and left and curves in the extrusion direction at a predetermined curvature while gradually reducing the cross-sectional area of the core metal 16 toward the anti-resin inlet 21 at a predetermined rate. ing. The end of the manifold 20 is formed so as to merge with the symmetrical manifold 20 on the opposite side at a position substantially 180 degrees from the resin inlet 21.

A dam lip portion 31 is formed corresponding to the junction 27 to form a shallow passage along the circumferential direction of the cored bar 16. 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-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 joined and merged so that the symmetrical manifolds 20 are in contact with a line along the axis of the metal core 16. As a result, the stream lines of the molten resin flowing down the manifold 20 become parallel at the junction.

The entire resin passage extending from the lower edge of the manifold 20 to the dam lip portion 31 is formed by the manifold 2.
0 shallower than the cross-sectional depth of the passage, and the dam lip 3
Land portion 33 forming a passage deeper than the flow path depth of one portion
Is formed. This is formed by adjusting the shaving depth of the outer periphery of the cored bar 16 as described above.

A lower die plate 6 is attached to the lower part of the die housing 12 by studs 8. A resin discharge port (die gap) 17 for extruding the parison 9 between the die lower plate 6 and the core 15.
Is formed. A die gap adjusting device 37 including a bolt box 35, a holding bolt 36, and a lock nut 34 is mounted on the lower die plate 6 at appropriate intervals around the lower peripheral portion of the die housing 12. . A screw is engraved on the inner peripheral surface of the bolt box 35, and after engaging with the holding bolt 36,
The desired die gap 17 can be adjusted to a desired die gap 17 by mutually moving a pair of presser bolts 36 symmetrically arranged with respect to the center axis of the die lower plate 6.

When blow molding is performed using a resin having a high solidification rate such as engineering plastics, it is necessary to inject the molten resin at a high speed by an injection device (not shown), which increases the resin pressure during extrusion. Although the distance between the die gaps 17 in the minor diameter direction does not change, there is a phenomenon that the distance between the die gaps 17 along the major diameter direction increases.

Therefore, in the present invention, as shown in the figure, a peripheral portion of the lower die plate 6 indicated by a chain line facing the core 15 is referred to as a die lip region 40, which is generated when the molten resin passes through a die gap 17 portion. In order to prevent the die gap 17 from expanding and deforming along the major axis direction C of the die lip region 40, the width of the die housing 12 and the lower die plate 6 and the width of the lower die plate 6 in the horizontal direction are as follows. decide.

That is, a reference value a (the inner short axis of the die lip region 40 having an oval cross-sectional shape) with respect to the width dimension of the die housing 12 (from the core 15 side end surface of the die lip region 40 to the die housing 12 outer end surface). 1.5
2.5 times, desirably 2 times, and the horizontal width of the lower die plate 6 (from the end face of the die lip area 40 on the core 15 side to the outer end face of the lower die plate 6).
Is 2.5 to 4 times, preferably 3 times the reference value a. At this time, the thickness of the die lower plate 6 in the vertical direction is optimally 0.5 to 1.0 times, preferably 0.7 times the reference value a.

The dimensional configuration of the die lower plate 6 described above is determined by the resin pressure during extrusion when the molten resin is injected at a high speed by an injection device. In this case, the die lip region 40 can be effectively provided with high rigidity and high strength by using the die lower plate 6 having an appropriate size according to the physical properties of the resin and the resin pressure at the time of extrusion.
Die gap 1 along major axis direction C of die lip region 40
7 can be suppressed to 0.1 mm or less, and the interval of the die gap 17 can be kept constant along the inner peripheral surface of the die lip region 40.

The operation of the flat die portion configured as described above will be described. The resin flowing in from the resin inlet 21 branches right and left in the manifold 20 and flows down to reach the junction 27, and at the same time as the branch flows, overflows from the lower edge of the manifold 20 to the land 33, and the resin flows in the resin passage 1
8 flows uniformly over the entire circumference. 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 flows down while being readjusted at the dam lip portion 31 to have a uniform thickness. It is injected as parison 9.

Under such circumstances, for example, when an attempt is made to perform blow molding using an engineering plastic having a viscosity higher than that of a general-purpose resin as the molten resin, the molten resin passes through the narrow die gap 17 together with the high-speed injection. A large pressure loss occurs, and the resin pressure causes the die lip region 40 to move toward the core 15 side. Therefore, according to the width dimension in the horizontal direction and the thickness dimension in the vertical direction of the die lower plate 6 as described above, it is possible to prevent deformation of the die lip region 40 due to strain in the major axis direction C of 0.1 mm or less due to the molten resin pressure. it can.

Thus, the parison 9 having a desired thickness hangs downward from the die gap 17 of the die 10 and is blow-molded. If it is desired to change the thickness of the parison 9 without making the thickness of the parison 9 symmetrical, the holding bolts 36 arranged on the left and right sides with respect to the center axis of the lower plate 6 of the die, for example, 36a and 36b, 36c and 36
d, and after rotating 36e and 36f as appropriate,
The desired die gap 17 can be easily obtained by rotating and tightening the lock nuts 34a, 34b, 34c, 34d screwed to the holding bolts 36, respectively.

[0027]

As is apparent from the above description, in the blow molding machine having the flat die according to the present invention, a resin passage is formed by inserting a core having a core into the center of the lower end of the die housing. A resin inlet from the extruder side is opened in the resin passage, and the cross section of the passage decreases from the surface of the core on the resin inlet side to the left and right in the circumferential direction, and decreases toward the side opposite to the resin inlet of the core. And a manifold curved in the direction of extrusion, and the ends of the manifold are merged to form a merged portion. Further, a die lower plate that is separated from the core to form a molten resin passage is provided below the die housing. It is coaxially arranged and the horizontal width of the lower plate of the die is made longer than the horizontal width of the die housing. Together performed, reduces the material replacement or color change time, the productivity is improved.

Furthermore, in order to prevent expansion and deformation of the die gap along the major axis direction of the die lip region which occurs when the molten resin passes through the die gap portion, a parison having a desired thickness can be injected from the die gap. Furthermore, a die lower plate, which is a separate member, may be simply attached to the lower part of the die housing at the most easily deformed portion without manufacturing the entire die housing with a highly rigid structure and a high-strength material. If the pressure of the molten resin increases, it is not necessary to increase the thickness of the entire die housing, so that the weight of the entire die is reduced. Also, it is not necessary to increase the ease of the heater when heating up the die. Less warming time is required.

[Brief description of the drawings]

FIG. 1 is a sectional front view of a flat die for blow molding according to one embodiment of the present invention.

FIG. 2 is a sectional side view of FIG.

FIG. 3 is an elevation view as viewed from II-II in FIG. 2;

[Explanation of symbols]

 Reference Signs List 6 die lower plate 9 parison 10 dice 12 dice housing 12a upper dice housing 12b lower dice housing 14 through-through hole 15 core 16 core metal 17 resin discharge port 18 resin passage 20 manifold 21 resin inflow 22 resin passage 27 junction part 30 control cylinder 31 Dam lip part 33 Land part 34 Lock nut 35 Bolt box 36 Holding bolt 37 Die gap adjusting device 40 Die lip area

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-6-198722 (JP, A) JP-A-6-170924 (JP, A) JP-A-4-31026 (JP, A) 136827 (JP, A) JP-A-62-267105 (JP, A) JP-A-56-166029 (JP, A) JP-A-5-200838 (JP, A) JP-A-4-113925 (JP, U) (58) Field surveyed (Int. Cl. ⁶ , DB name) B29C 49/04

Claims (1)

(57) [Claims] 1. A resin passage is formed by inserting a metal core having a core in the center of a lower end of a die housing, and a resin inlet from an extruder side is opened in the resin passage. The manifold branches off from the metal core surface to the left and right in the circumferential direction, the cross-sectional area of the passage decreases toward the resin inflow side of the metal core, and a manifold curved in the extrusion direction is formed. And a coaxially arranged lower die plate for forming a molten resin passageway apart from the core, the lower die plate having a horizontal width dimension of the lower die plate in the horizontal direction of the die housing. A blow molding machine having a flat die, the width of which is longer than the width.