JPH06170924A - Blow molding machine with flat die - Google Patents

Abstract

(57) [Summary] (Modified) [Purpose] To provide a flat die that can easily obtain a parison with an appropriate thickness and can smoothly perform resin replacement. [Composition] The resin inlets 22 are opened at symmetrical positions, and a manifold 25 is formed on each surface of the metal core 16 which is branched from the respective resin inlets 22 to the left and right in the circumferential direction and curved in the extrusion direction while reducing the passage cross-sectional area. The end of the manifold 25 and the end of the manifold 25 from the other resin inlet are joined together. The merging portion 21 is opened to form a dam lip portion 28 that forms a shallow passage along the circumferential direction of the core metal 16, and the manifold 25 is deep in the entire tubular passage between the dam lip portion 28 and the manifold 25. A land portion is formed that is shallower than this and forms a passage deeper than the dam lip portion 28. Further, a die lower plate 6 having a die gap between cores forming a cored bar under the die housing and having a horizontal dimension larger than that of the die housing 6
Put on.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a die lip deformation preventing device for a flat die having a flat ring 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 with a die having a ring-shaped resin discharge port, and this is sandwiched between molds. After that, a hollow product is formed by blowing gas such as air into the parison to cool it.

A general structure of a conventional parison injection die used in such a blow molding machine is a die lip mounted on the tip of the mandrel by inserting a mandrel into a die housing to form a cylindrical resin passage. The hollow parison is ejected from a ring-shaped resin discharge port formed by facing 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, and it is generally formed in a circular ring shape to inject a parison with a cylindrical cross section. However, depending on the shape of the mold cavity, it may be flat. A parison with a cross section is desirable in some cases, and in recent years, it has been applied to flat-plate structures such as vehicle doors and panels, or bumpers and spoilers. In such cases, the shape of the resin discharge port is oval or the like. As a flat shape, the flat parison has been formed by injection molding.

[0004]

By the way, in the conventional parison injection die in the blow molding machine, the shape of the resin discharge port is constant according to the preset product.
Therefore, each time the product shape changes, the required parison shape also changes, and accordingly, the shape of the resin discharge port is changed so that a parison suitable for each product, such as a deep product or a thin product, can be injected. Treatment is required. In such a case, conventionally, in order to obtain a parison suitable for a molded product,
It is common to replace the entire die each time a molded product is different, or mold by a dedicated blow molding machine for each molded product.

If the shape and size of the molded product are different, it is not easy to replace the heavy die, and it is dangerous if the entire die is replaced for each different molded product. In addition, there is a drawback in that the operation rate of the blow molding machine is reduced if molding is performed using a dedicated blow molding machine for each molded product.

In order to solve such a problem, there is one in which only the lower die housing and the lower mandrel are replaced to change the parison size. Normally, in a flat die with a basic shape, the pressure loss of the resin passing through the resin flow path on the major diameter side and the minor diameter side of the lower part of the die is the same in the circumferential direction, so a uniform parison is formed. Is possible. However, when the lower part of the die, that is, the lower die housing and the lower mandrel is replaced with a die larger or smaller than usual, the lengths of the resin flow paths on the major diameter side and the minor diameter side of the flat die necessarily change. For this reason, the pressure loss of the resin passing through the resin flow path differs in the circumferential direction, and the parison extruded from the die has poorer performance on the major diameter side, and the resin flows only on the minor diameter side, resulting in a non-uniform parison. There is a problem that it is difficult to mold the desired parison.

Further, since the flat die has a flat shape, in order to prevent the high stress generated at the end of the die housing member on the long diameter side and the large displacement (deflection) occurring on the short diameter side of the die housing member, The housing member needs to be made of a material having a high rigidity and a high strength. Therefore, if the wall thickness of only the lower part of the die housing is increased, the weight of the entire die becomes enormous, and in addition, enormous heater capacity is required to heat up the die and the heating time is long. There was a problem.

The present invention has been made to solve the above-mentioned drawbacks of the prior art, and it is to provide a flat die which can easily obtain a parison having an appropriate thickness and can smoothly perform resin change. To aim.

[0009]

In order to achieve the above object, in a blow molding machine having a flat die according to the present invention, a cored bar having a core at the center of the lower end of the die housing is inserted into the die housing. Forming a resin passage,
A manifold in which resin inlets from the extruder side are opened symmetrically in the resin passages, and each resin inlet is branched to the left and right in the circumferential direction on the surface of the core metal to reduce the passage cross-sectional area while curving in the extrusion direction. And forming a dam lip portion that forms a shallow passage along the circumferential direction of the core metal by opening the joining portion and joining the manifold end and the manifold end from the other resin inlet, respectively.
A flat die in which a land portion having a passage shallower than the manifold depth and deeper than the dam lip portion is formed is used for the entire resin passage between the dam lip portion and the manifold, and a die for forming a molten resin passage is formed apart from the core. The lower plate is coaxially arranged in the lower portion of the die housing, and the width dimension of the die lower plate in the horizontal direction is longer than the horizontal dimension of the die housing.

[0010]

According to the above construction, the resin flows into the cylindrical passage in the die from the resin inflow port for each shot, but this 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, and the resin flows down from there, and at the same time, the resin also flows down from the land portion to the dam lip portion. The land height from the dam lip portion gradually decreases in the manifold path direction, 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. As it goes around, a parison with a uniform thickness is hung from the resin discharge port. Also, in order to prevent deformation of the die gap due to resin pressure at the time of injection at the bottom of the die housing,
A width of one side of the die lip plate is 1.5 to 2.5 times as large as the standard dimension of the inner minor axis of the die lip region, and the other side is 2.5 to 4 times as large as the standard dimension. This reduces the weight of the die as a whole.

[0011]

The following is a detailed description with reference to specific examples of a blow molding machine having a flat die according to the present invention.

FIG. 1 shows the structure of a flat die according to an embodiment. This is applied to the injection die of a flat type parison, and as shown in the figure, this die 10 has a die housing 12, and a through-hole 14 having a substantially oval cross section is formed along the longitudinal center line thereof. It is set up. Such a through hole 14 is opened in the lower end surface of the housing 12 in a state in which the corresponding diameter is gradually reduced from the middle thereof to the lower end surface of the housing 12. A core metal 16 having a smaller diameter than that of the through hole 14 and having an oval cross section is inserted into the housing 12, and a space between the outer peripheral surface of the core metal 16 and the inner peripheral surface of the through hole 14 is inserted. The resin passage 18 is formed in the. The upper end portion of the cored bar 16 has a cross-sectional structure in close contact with the through-hole 14, and the resin passage 18
Is formed. A resin supply passage 20 is bored inside the core metal 16, and the resin supply passage 20 is branched in the direction of the equivalent diameter of the core metal 16 to open a pair in the resin passage 18. The opening is set in the resin passage 18 on the wide side as shown in the drawing, and this serves as a resin inlet 22. The mandrel 16 is composed of a mandrel 16a at the upper part and a core 16b at the lower part.

On the outer surface of the core metal 16, each resin inflow port 22 is used as a base point, and the semicircle is branched leftward and rightward in the circumferential direction to gradually decrease the cross-sectional area of the passage at a predetermined ratio while curving in the extrusion direction with a predetermined curvature. A manifold 25 having a cross section is formed. The end of this manifold 25 is approximately 18 from the manifold 25 on the opposite side and the resin inlet 22 which are symmetrical.
They are formed so as to join each other at a position of 0 degree. Then, a dam lip portion 28 that forms a shallow passage is formed along the circumferential direction of the cored bar 16 corresponding to this confluence portion 26. The dam lip portion 28 is the resin passage 1
It is provided so as to correspond to the throttle passage portion of No. 8, and the gap between the throttle passage portion and the through hole 14 of the housing 12 is narrowed so that the flow path resistance is uniform over the entire circumference. In this case, the merging portion 26 is the symmetric manifold 2
The five are joined together so as to come into contact with the line along the axis of the core 16. As a result, the resin flow lines flowing down the respective manifolds 25 are parallel at the merging portion.

The entire tubular passage extending from the lower edge of the manifold 25 to the dam lip portion 28 is
It is shallower than the cross-sectional depth of the 5th part, and the dam lip 2
Land portion 30 forming a passage deeper than the depth of the flow passage in 8 parts
Is formed. This is formed by adjusting the scraping depth of the outer surface of the cored bar 16 as described above.

A lower die plate 6 is attached to the lower portion of the die housing 12 by means of stud bolts 8. A slit (die gap) 15 for pushing the parison 9 between the lower die plate 6 and the core 16b.
Is formed. A die gap adjusting device 37 including a bolt box 32, a holding bolt 33, and a lock nut 34 is mounted on the lower die plate 6 at appropriate intervals on the outer periphery of the lower portion of the die housing 12. . A screw is engraved on the inner peripheral surface of the bolt box 32, and after engaging with the holding bolt 33,
The pressing gaps 33 arranged symmetrically with respect to the center axis of the die lower plate 6 are moved as a set so that the desired die gap 15 can be adjusted.

When blow molding is performed using a resin having a high solidification rate such as engineering plastic, 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 15 in the minor axis direction did not change, there was a phenomenon in which the distance between the die gaps 15 along the major axis direction increased.

Therefore, in the present invention, as shown in FIG.
The peripheral portion of the die lower plate 6 facing the core 16b indicated by a chain line is referred to as a die lip region 40, and expansion of the die gap 15 along the major axis direction C of the die lip region 40 caused when the molten resin passes through the die gap 20 part. In order to prevent deformation, the width dimensions of the die housing 12 and the die lower plate 6 and the horizontal width dimension of the die lower plate 6 are determined as follows.

That is, with respect to the width dimension of the die housing 12 (from the end surface of the die lip area 40 on the core 16b side to the outer end surface of the die housing 12), a reference value a (inner minor axis of the die lip area 40 having an oval cross section) 1.
5 to 2.5 times, preferably 2 times, and the horizontal width dimension of the die lower plate 6 (from the end surface of the die lip region 40 on the core 16b side to the outer end surface of the die lower plate 6) is set to the standard value a. 2.5 to 4 times, preferably 3 times. 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 structure 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 the injection device. In this case, by using the die lower plate 6 having an appropriate size depending on the physical properties of the resin and the resin pressure at the time of extrusion, the die lip region 40 can effectively have high rigidity and high strength,
Die gap 1 along the major axis direction C of the die lip region 40
The strain of No. 5 can be suppressed to 0.1 mm or less, and the gap of the die gap 15 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 that has flowed in from the resin inflow port 22 branches left and right in the manifold 25 and flows down to reach the merging portion 26. At the same time as the branching and flowing down, the resin sequentially overflows from the lower edge of the manifold 25 to the land portion 30, and the resin flows in the cylindrical passage. 1
8 will flow uniformly over the entire circumference. Since the groove cross-sectional area of the manifold 25 is set to be gradually reduced, the pressure distribution in the circumferential direction becomes uniform and the dam lip portion 28 flows down in a re-adjusted state to have a uniform wall thickness. It is shot 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 a molten resin, when the molten resin passes through a narrow die gap 15 together with high-speed injection. A large pressure loss is generated, and the resin pressure tends to move the die lip region 40 so as to bulge toward the side opposite to the core 16b. 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, the deformation of the die lip region 40 due to the strain in the major axis direction C due to the molten resin pressure can be prevented to be 0.1 mm or less. it can.

In this way, the parison 9 having a desired thickness hangs downward from the die gap 15 of the die 10 and is blow-molded. Further, if it is desired to change the thickness of the parison 9 without making the wall thickness symmetrical, the pressing bolts 33 arranged in a pair to the left and right with respect to the center axis of the die lower plate 6, for example, 33a and 33b, 33c and 33.
After rotating d, and 33e and 33f respectively,
The desired die gap 15 can be easily obtained by rotating and tightening the lock nuts 34a, 34b, 34c, and 34d that are respectively screwed into the holding bolts 33.

[0023]

As is apparent from the above description, in the blow molding machine having the flat die according to the present invention, the core metal having the core at the center of the lower end of the die housing is inserted into the die housing to make the resin. Forming a passage,
A manifold in which resin inlets from the extruder side are opened symmetrically in the resin passages, and each resin inlet is branched to the left and right in the circumferential direction on the surface of the core metal to reduce the passage cross-sectional area and bend in the extrusion direction. And forming a dam lip portion that forms a shallow passage along the circumferential direction of the core metal by opening the merging portion while merging the manifold end and the manifold end from the other resin inflow port,
A flat die in which a land portion having a passage shallower than the manifold depth and deeper than the dam lip portion is formed is used for the entire resin passage between the dam lip portion and the manifold, and a die for forming a molten resin passage is formed apart from the core. By disposing the lower plate coaxially with the lower part of the die housing and by making the horizontal width dimension of the die lower plate longer than the horizontal width dimension of the die housing, it is possible to easily change the material and the color. In addition to being able to do this, the time required for material changes and color changes is reduced, improving productivity.

Furthermore, in order to prevent expansion deformation of the die gap along the major axis direction of the die lip region that occurs when the molten resin passes through the die gap portion, a parison having a desired uniform wall thickness can be injected from the die gap, Further, it is sufficient to simply attach a separate die lower plate to the lower portion of the die housing at the most easily deformable portion without manufacturing the entire die housing with a highly rigid structure and a high strength material. Even if the molten resin pressure rises, it is not necessary to increase the thickness of the die housing as a whole, so the weight of the die becomes lighter, and it is not necessary to increase the size of the heater when heating up the die. It requires less warm time.

[Brief description of drawings]

FIG. 1 is a cross-sectional configuration diagram of a die according to an embodiment.

FIG. 2 is an elevation view seen from II-II in FIG. 1 (2).

[Explanation of symbols]

 6 die lower plate 9 parison 10 die 12 die housing 14 through hole 15 slit (die gap) 16 core metal 16a mandrel 16b core 18 resin passage 20 resin supply passage 22 resin inlet 25 manifold 26 confluence portion 28 dam lip portion 30 land portion 32 Bolt Box 33 Holding Bolt 34 Lock Nut 37 Die Gap Adjuster 40 Die Lip Area

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location B29C 49/48 6122-4F 49/78 6122-4F // B29L 22:00 4F

Claims (1)

[Claims] 1. A core metal having a core at the center of the lower end of the die housing is inserted into the die housing to form a resin passage, and a resin inlet from the extruder side is opened in a symmetrical position in the resin passage. At the same time, a manifold that branches left and right in the circumferential direction from each resin inlet to the surface of the core metal and curves in the extrusion direction while reducing the passage cross-sectional area is formed. The manifold end and the manifold end from the other resin inlet are joined together. At the same time, the merging portion is opened to form a dam lip portion forming 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 shallower than the manifold depth. Using a flat die having a land portion having a passage deeper than that of the die, a die lower plate which forms a molten resin passage apart from the core is formed. A blow molding machine having a flat die, characterized in that a rate is coaxially arranged in a lower portion of the die housing, and a horizontal width dimension of the die lower plate is longer than a horizontal width dimension of the die housing. .