JPH0431026A - Blow molding machine with flat die - Google Patents

Abstract

PURPOSE:To prevent a die gap along the long diameter direction from expansion by disposing a core at a lower end center section of a die housing, also disposing a die lower section plate forming a molten resin path at the lower section of die housing coaxially and making the width dimension in the horizontal direction of the die lower section plate longer than the width dimension in the horizontal direction of the die housing. CONSTITUTION:Molten resin 12 fed forcibly between a mandrel 3 and a die housing 2 by an injection device is extruded as a parison 9 out of a slit 20 formed with a core 5 at the lower end of the mandrel 3 and the end of a die lower section plate 6. When the molten resin 12 is passed through the narrow slit 20 correspondingly with the high speed injection and is moved through a die lip zone 21 in a manner of expanding to the side 5 opposite to the core. From the above reason, the width dimension in the horizontal direction of the die lower section plate 6 should be 2.5 - 4 times as much as the reference value (a), desirably 3 times. Thus the deformation generated by the distortion in the long diameter section direction of die lip zone 21 generated by pressure of molten resin 12 can be controlled to 0.1mm or less.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a device for preventing die lip deformation of a flat die having a flat annular shape in a blow molding machine.

[Conventional technology] FIG. 3 shows a plan view of a conventional flat die.

Conventionally, when molding hollow resin containers by blow molding, it is easy to adjust the wall thickness in the circumferential direction of the parison, and
Flat dies are used for forming deep double-walled products because they prevent rupture.

Blow molding equipment having this flat die has been widely used for general-purpose resins.

To explain such conventionally used blow molding equipment, there is a mandrel in the center of the die body.
A core is fixed to its lower end.

A die housing surrounds the outer periphery of the core at the bottom of the main body, and a flat annular slit (die lip gap) is formed between the core and the die housing.

The lower end of the molten resin passage is connected to a slit, and when the plunger of the resin injection device is pushed forward, the molten resin in the molten resin passage is forced out of the main body through the slit, and a parison is formed.

[Problem to be solved by the invention] When using such a blow molding machine to inject engineering plastics (commonly known as engineering plastics) at high speed, the pressure loss at the slit between the lower die housing and the core becomes large. , resin pressure for example 5
You may have to apply more than 00kg/Cgo.

For this reason, the lower die housing, which determines the wall thickness of the parison, also swells at its longer diameter portion, resulting in a problem that the lower die lip gap is not uniform in the circumferential direction.

Therefore, in order to solve these problems, it is necessary to manufacture the die from a material with a highly rigid structure and high strength. In particular, the rigidity of the die lip is particularly important because the dimensions of the die gap ultimately determine the wall thickness of the parison. However, for this purpose, if the horizontal width of the die housing is made extremely thick, the weight of the whole die becomes enormous.Furthermore, heating up the die requires an enormous heater capacity, and the heating time is also long. New problems have arisen, such as the question of how to become a product.

[Means for Solving the Problems] In order to solve such problems, in the present invention, a core is disposed at the center of the lower end of the die housing, and the lower part of the die is spaced apart from the core and forms a molten resin passage. A plate is disposed coaxially under the die housing, and the horizontal width of the die lower plate is longer than the horizontal width of the die housing.

[Working] A die lower plate, which forms a die gap with the core disposed at the center of the lower end of the die housing and has a width larger than the horizontal width of the die housing, is attached to the lower part of the die housing. arranged coaxially with. The horizontal width of the die housing, which is difficult to deform, is set to 1.5 to 2.5 times the inner short axis of the die lip area as the reference dimension, and the horizontal width of the die lower plate, which is most easily deformed, is Since the width dimension is 2.5 to 4 times the reference dimension, the weight of the entire die is light.

[Example] Figures 1 and 2 show an example of the present invention.
FIG. 1 is a longitudinal cross-sectional view of the flat die, and FIG. 2 is a plan view in the direction of arrows ``■-■''.

In FIG. 1, a die 1 in a blow molding machine is connected to a die housing 2. Mandrel 3. It is composed of a core 5, a die lower plate 6, and a die gap adjustment device 7.

First, a die lower plate 6 is attached to the lower part of the die housing 2 with stud bolts 10.

A mandrel 3 is disposed at the center of the die housing 2, and a core is fixedly disposed at the bottom of the mandrel 3, and a slit (for injecting the parison 9) is provided between the die lower plate 6 and the core 5. The die gap) 20 is formed.

Further, on the outer periphery of the lower region of the die housing 2, a bolt box 22, a presser bolt 23, and a lock nut 24 are provided.
A die gap adjusting device 7 consisting of a die gap adjusting device 7 is placed on the die lower plate 6 at appropriate intervals. A thread is carved on the inner peripheral surface of the bolt box 22, and after engaging with the presser bolt 23, the presser bolts 23 arranged symmetrically with respect to the central axis of the die lower plate 6 are connected to each other as a set. By moving the die gap 20, the die gap 20 can be adjusted to a desired value.

When performing blow molding using a resin that solidifies quickly, such as engineering plastic, it is necessary to inject the molten resin 12 at high speed using an injection device, but this increases the resin pressure during extrusion, causing the short diameter portion to Although the distance between the diamond gaps 20 along the direction does not change, a phenomenon has occurred in which the distance between the die gaps 20 along the major axis direction increases.

Therefore, in the present invention, as shown in FIG. 2, the peripheral part of the die lower plate 6 facing the core 5 shown by the chain line is referred to as the die lip area 21, and the die lip area is generated when the molten resin 12 passes through the slit 20. In order to prevent expansion and deformation of the slit 20 along the major axis direction C of the die housing 2 and the die lower plate 6,
The horizontal width dimension of the die lower plate 6 is determined as follows.

That is, for example, the width dimension of the die housing 2 (from the core 5 side end surface of the die lip region 21 to the outer end surface of the die housing 2) is set to 1. The width of the die lower plate 6 in the horizontal direction (from the core side end surface of the gui-rip area 21 to the outer end surface of the die lower plate 6) should be set to 5 to 2.5 times, preferably twice the reference value a. 2.5 to 4 times, preferably 3 times. At this time, the vertical thickness dimension of the die lower plate is the standard value a
The optimal value is 0.5 to 1.0 times, preferably 0.7 times.

The dimensional structure of the die lower plate 6 described above is determined by the resin pressure during extrusion when the molten resin 12 is injected at high speed by an injection device. In this case, by using the die lower plate 6 of appropriate dimensions depending on the physical properties of the resin and the resin pressure during extrusion, the die lip area 21 can be effectively made to have high rigidity and high strength, and the long diameter part of the die lip 21 can be effectively made high in rigidity and strength. It becomes possible to suppress the strain in the die gap 20 along the direction C to 0.1 mm or less, and the interval between the die gaps 20 can be kept constant along the inner circumferential surface of the die lip region 21.

Next, the operation of the blow molding machine configured as described above will be explained.

The molten resin 12 press-fitted between the mandrel 3 and the die housing 2 by an injection device is extruded as a parison 9 through a slit 2o formed by the core 5 at the lower end of the mandrel 3 and the end of the die lower plate 6. Under such circumstances, if blow molding is attempted using, for example, an engineering plastic with a higher viscosity than a general-purpose resin as the molten resin 12, combined with high-speed injection, a large amount of pressure will be generated when the molten resin 12 passes through the narrow slit 20. A loss occurs, and the resin pressure causes the die lip region 21 to bulge and move toward the side opposite to the core 5.

Therefore, if the width dimension in the horizontal direction and the thickness dimension in the vertical direction of the die lower plate 6 are set as described above, the deformation due to the strain in the long diameter direction C of the die lip region 21 due to the pressure of the molten resin 12 can be reduced to 0. This can be prevented to 1 mm or less. In this way, the parison 9 with the desired thickness is
It hangs downward from the slit 2o of the die 1 and is blow molded.

In addition, if you want to change the thickness of the parison 9 without making it symmetrical, use a presser port 23, for example 23a, arranged symmetrically with respect to the central axis of the die lower plate 6.
23b, 23c and 23d, and 23e and 23f, respectively, and then lock nuts 24a, 24b, 24c, and 24d, which are fitted onto the presser bolt 23, respectively.
By rotating and tightening, the desired die gap 2 can be achieved.
0 is easily obtained.

[Effect of the invention] As is clear from the above explanation, in the present invention,
In order to prevent the expansion and deformation of the die gap along the long diameter direction of the die lip area that occurs when the molten resin passes through the slit, the entire die housing is not made of a highly rigid structure and high strength material. It is sufficient to simply attach a separate die lower plate to the lower part of the die housing at the location where deformation is most likely to occur. Even if the molten resin pressure increases, there is no need to increase the thickness of the entire die housing, which reduces the weight of the entire die, and there is no need to increase the heater capacity when heating up the die, which increases the temperature. It also takes less time.

[Brief explanation of drawings]

1 and 2 show an embodiment of the present invention,
FIG. 1 is a longitudinal cross-sectional view of a flat die, FIG. 2 is a plan view taken along arrows 1--2, and FIG. 3 is a plan view of a conventional flat die. 1... Dice, 2... Dice housing, 3
... Mandrel, 5... Core, 6... Die lower plate, 7... Die gap adjustment device, 9... Parison, 12... Molten resin, 20... Slit.

Claims (1)

[Claims] A core is disposed at the center of the lower end of the die housing, a die lower plate that is spaced apart from the core and forms a molten resin passage is coaxially disposed at the lower part of the die housing, and the width of the die lower plate in the horizontal direction is A blow molding machine having a flat die, characterized in that the dimension is longer than the horizontal width dimension of the die housing.