JPH06285965A - Molding apparatus - Google Patents

Abstract

PURPOSE:To obtain a molding apparatus having a structure enabling attainment of a molded article which can eniure uniformity in a wall thickness and satisfy a mechanical strength, when a material of which the amount of extension due to temperature is large relatively. CONSTITUTION:A preform temperature controlling mechanism 30 which enables a change of the temperature of a preform conveyed to an orientation blow molding part 18, in a state wherein the temperature is controlled in a height direction, by selecting zones divided in the height direction and a circumferential direction is provided. By controlling the temperature of a thin wall part of which the temperature tends to be high relatively, accordingly, the temperature can be so set as to enable attainment of a uniform wall thickness for the whole surface of the preform. Therefore, the wall thickness ensuring mechanical strength in the height direction can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molding device.

[0002]

2. Description of the Related Art Generally, a thin-walled container made of synthetic resin called a biaxially stretch blow molded container (hereinafter referred to as a molded product).
For example, the preform obtained by injection molding can be positioned in the cavity of the blow mold, stretched in the axial direction of the container, and expanded in the direction perpendicular to the axial direction by the pressure of the gas blown inside. It is being appreciated.

As a molding device for such a molded product, there is, for example, a structure called a one-stage system or a hot parison system. A well-known one having this structure is one having a turntable capable of intermittent rotation on a base. Then, a split lip support plate and a lip die composed of a split die are provided on the turntable. This lip mold is provided for holding the lip portion of the preform corresponding to the neck portion of the molded product.

[0004] The rotating disc, when rotated, is an injection molding station that executes an injection molding process, a temperature control station that performs a temperature control process of an injection-molded preform, and a stretch blow molding process that performs a preform blow process. The station and the eject station for executing the step of taking out the blow-molded molded article are respectively passed.

By the way, in such a system, there is a structure in which a plurality of injection molding stations are installed. This is a structure used particularly when the wall thickness is extremely large and cannot be covered by the resin filling amount in one injection molding. Therefore, blow molding is performed on a preform having a multi-layer structure by joining the inner layer side and outer layer side preforms obtained by injection molding a plurality of times to form a thick molded product. You can

[0006]

By the way, it is an important subject of the hot parison method how to reduce the temperature unevenness of the preform that occurs when the preform is injection-molded.

The cause of this temperature unevenness is
The plasticized state of the filled resin may be non-uniform, and a temperature difference may already exist in the resin. For this reason, if the mold is uniformly cooled in the preform-forming mold, this temperature difference is somewhat alleviated, but remains in the preform.

Further, due to unevenness of the resin flow at the time of preform injection molding, that is, unevenness of the resin flow state due to the ease and difficulty of the flow of the resin when flowing through the mold, portions where the resin easily flows and portions where the resin does not easily flow The present inventor presumed that a temperature difference would appear in the preform due to the difference in the cooling time between the two.

Of course, such temperature unevenness in the preform is alleviated by the temperature shift in the resin while being uniformly heated in the circumferential direction in the temperature adjusting step, but it is completely alleviated. Time may not be taken in the temperature control process. This is particularly noticeable when the preform is thick.

When it is necessary to heat an injection-molded preform for a relatively long time in the temperature control process like PC (polycarbonate), the time (molding cycle) allotted to the temperature control process is set. Since it was consumed almost in the heating step, it was not possible to obtain time for alleviating such temperature unevenness.

In particular, when a large-capacity bottle, which is a thick molded product, is intended to have a durable strength, for example, polycarbonate (hereinafter referred to as PC) is used.
When a is used, the amount of elongation tends to be different due to the extremely low co-stretchability of this material, such as polyethylene terephthalate, that is, the uniform stretch constraint that occurs between molecules. is there. Therefore, when a material having low co-stretchability such as PC is selected as a material for the bottle, an extremely thin wall thickness is obtained at a high temperature portion, resulting in mechanical strength, particularly impact strength. May decrease, or the blow pressure may cause a burst.

Therefore, in view of the problems in the above-mentioned conventional molding apparatus, the object of the present invention is to make the wall thickness uniform and the mechanical strength even when a material having a relatively large difference in elongation amount due to temperature is used. It is an object of the present invention to provide a molding apparatus that can obtain a molded product that satisfies the above conditions.

[0013]

In order to achieve this object, the invention according to claim 1 is a molding apparatus provided with a stretch blow molding section for stretch blow molding a preform to form a hollow body. The preform conveyed to the blow molding unit is divided in the height direction and the circumferential direction, and a temperature control mechanism capable of controlling the temperature by selecting each of the divided zones is provided.

According to a second aspect of the present invention, in the molding apparatus according to the first aspect, the temperature adjusting mechanism has a structure capable of independently changing the temperature of the selected zone.

The invention according to claim 3 is the invention according to claim 1 or 2.
One of the described molding apparatuses is characterized in that the temperature adjustment mechanism has a structure formed by blowing air.

The invention according to claim 4 is the invention according to claim 1 or 2.
In one of the molding apparatuses described above, the temperature control mechanism is characterized in that low-pressure blow air is blown into the preform to bring the preform into contact with the inner surface of the preform, thereby enabling temperature control for each zone.

[0017]

In the present invention, the zones selected and divided in the height direction and the circumferential direction of the preform are temperature-controlled immediately before the stretch blow molding at the stretch blow molding station.

Therefore, the temperature of the portion of the preform that has reached the desired stretching temperature or higher or the portion that does not reach the desired stretching temperature is set to the desired temperature by the selected temperature control zone.

In particular, when the preform made of PC is stretch-blown, the stretch temperature can be obtained by cooling in a temperature control zone in order to prevent excessive stretch (burst) of a portion having a desired stretch temperature or higher.

When the temperature control mechanism is air, the diffused air also changes the ambient temperature of a desired portion to some extent, so that the temperature changes to a moderate extent to some extent, and a rapid change is prevented.

When the temperature control mechanism is of the contact type, the temperature of the preform portion corresponding to the divided zone to be temperature controlled can be controlled reliably.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below with reference to the drawings.

FIG. 1 is a plan view showing a machine base 20 of a blow molding apparatus 10 as an example of the molding apparatus according to the present invention. The blow molding apparatus 10 has injection molding mechanisms installed at two locations, and has a structure for molding a preform for obtaining a thick molded product by two-stage injection molding. This is because the injection molding process is performed separately because the injection amount of the resin in one injection molding does not reach the predetermined wall thickness.

A turntable 22 is provided on the machine base 20.

The turntable 22 is provided so as to be intermittently rotatable with respect to the machine base 20 in the direction of the arrow in the figure, and stops at the next station in the process of intermittent rotation. As each station in this embodiment, a first injection molding station 12 that executes the injection molding process of the portion corresponding to the inner layer of the preform, and a second injection molding station that executes the injection molding process of the portion corresponding to the outer layer of the preform. Injection molding station 14, a temperature control station 16 for performing a temperature control step of a preform constituted by adhering inner and outer layers, a stretch blow molding station 18 for performing a stretch blow molding step of the preform, and a stretch blow molding. The eject station 20 that executes the step of taking out the molded product corresponds to this.

The rotary disk 22 is provided with a lip-type transfer plate 24 for holding the lip portion of the preform corresponding to the neck portion of the molded product corresponding to each station, while being transferred to each station. ing. In the present embodiment, a molded product having a large wall thickness is targeted, and since such a molded product is a large-capacity bottle, the number of preforms held by the lip type transfer plate 24 is one. For this reason, the lip type transfer plate 24 is provided with a lip type support plate 24A and a lip type 24B, which are split dies, according to the number of preforms.

The stretch blow molding station 18 described above.
2, a blow cavity mold 26 having a split mold structure is arranged, and the blow cavity mold 26 is configured to be opened and closed by a hydraulic cylinder 28.

On the other hand, the stretch blow molding station 18 is provided with a preform temperature control mechanism 30.

That is, the temperature adjusting mechanism 30 is provided to change the temperature adjusted at least for the zones divided in the height direction of the preform before the stretch blow molding, The structure is shown in the drawings starting from FIG.

In FIG. 3, the temperature adjusting mechanism 30 in this embodiment is provided to partially lower the temperature in the preform height direction, and the cooling temperature adjusting member 3 is provided.
2, an air cylinder 34, a sliding drive unit 36, and an air blowing mechanism 38.

The cooling temperature adjusting member 32 is provided to partially cool the outer peripheral surface of the preform conveyed to the stretch blow molding station 18. The cooling temperature adjusting member 32 is composed of a split mold that can surround the outer peripheral surface of the preform. Then, the cooling temperature adjusting member 32
Is a butterfly plate 40 attached to one of its parting surfaces.
By being hingedly connected to the support column 42, it can be opened and closed as shown in FIG. 5 with the position of the butterfly plate 40 as a fulcrum. Therefore, when the cooling temperature adjusting members 32 are closed and the parting surfaces are in close contact with each other, they can face the outer peripheral surface of the preform. Further, the cooling temperature adjusting member 32
An inner plate 32A is fixed to the inner peripheral surface of the inner plate 32A, and the inner plate 32A is divided into a plurality of zones in the height direction and the circumferential direction of the preform as shown in FIG. In this embodiment, the inner plate 32A fixed to one cooling temperature adjusting member 32 is divided into 9 zones. Further, the inner plate 32A is formed with nozzles 32A1 that open on the surface thereof at a plurality of locations per block.
An opening (not shown) formed on the cooling temperature adjusting member 32 side communicates with the. The nozzle 32A1 is a part of the air blowing mechanism 38 and is connected to the hose 38A connected to the opening. This hose 38A
The nozzle 32A1 and the nozzle 32A1 form one component of the air blowing mechanism 38. That is, the hose 38A is connected to an air pump (not shown) via the connector 38B provided on the connector mounting substrate 48 fixed on the base 36A of the sliding drive unit 36 described later, and is connected to the nozzle 32A from the air pump. It is designed to send air for cooling. The air blowing from the nozzle 32A1 can select the blowing position by a signal from a control unit (not shown), and in the present embodiment, when the temperature is controlled, the temperature is relatively higher than that of other portions. The block that faces the thin wall portion that tends to be selected is selected as the air blowing position.

Regarding the selection of the air blowing position, for example, the molding sequence may be set in advance on the basis of the shape of the molded product to be executed, in particular, the distribution condition of the wall thickness, or it may be experimentally tested in advance. The temperature distribution of the molded product is inspected and set.

On the other hand, one end of the driven arm 44 in the extension direction is attached to the cooling temperature adjusting member 32 on the side where one part of the butterfly plate 40 is attached, and the other end of the driven arm 44 in the extension direction is air. It is attached to the actuator 34A of the cylinder 34. The portion of the cooling temperature adjusting member 32 to which one end of the driven arm 44 is attached is the cooling temperature adjusting member 3
This is the position that forms the point of action for the swing fulcrum when opening and closing 2. Therefore, when a driving force is applied from the air cylinder 34 via the driven arm 44 at this position, the cooling temperature adjusting member 32 can be opened / closed in conjunction with the forward / backward movement of the actuator 34A.

In the air cylinder 34, the timing for opening and closing the cooling temperature adjusting member 32 is set as follows. That is,
After the preform is conveyed to the stretch blow molding station 18 and set, when the cooling temperature adjusting member 32 can face the outer peripheral surface of the preform by the sliding drive unit 36 described later, as shown by the solid line in FIG. The actuator 3 in the direction in which the cooling temperature adjusting member 32 can be closed.
4A is moved, and at other times, the actuator 34A is moved in the direction in which the cooling temperature adjusting member 32 is opened, as indicated by the chain double-dashed line in FIG.

Further, the air cylinder 34 has the sliding drive unit 3
6 is attached to the mounting base 50 fixed to the upper surface of the support piece 46 fixed to the base 36A of FIG. 6, and is interlocked with the movement of the sliding drive unit 36, and is indicated by the arrow in FIG. You can move back and forth.

That is, the slide drive unit 36 is retracted from the preform arrangement position and the rotary conveyance range of the molded product, and is cooled in the direction perpendicular to the opening / closing direction of the blow cavity mold 26 shown in FIG. It is a mechanism for moving the temperature control member 32 back and forth to move it back and forth with respect to the position where the preform is arranged. This advance / retreat operation is to prevent the preform from being disturbed, and when the preform is conveyed and set in the stretch blow molding station 18, the cooling temperature adjusting member 32 is moved to the outer periphery of the preform. It can be moved to the position where it faces the surface. Therefore, the slider 36B is fixed to the lower surface of the base 36A of the sliding drive unit 36.
6B is provided to be interlockable with the linear drive member 36C. In this embodiment, for example, a hydraulic cylinder is used as the linear drive member 36C, and the piston of this hydraulic cylinder is connected to the slider 36B.

Next, the operation will be described.

The temperature adjusting mechanism 30 keeps the preform evacuated from the position where the preform is arranged and the cooling temperature adjusting member 32 is opened until the preform is conveyed to the stretch blow molding station 18. Is set as the position of. Therefore, in the sliding drive unit 36, the linear drive member 36C moves the base 36A in a direction away from the preform setting position, and the base 36A is moved.
The upper air cylinder 34 is also interlocked with this and is placed at a position away from the preform setting position.

Further, the air cylinder 34 moves the driven lever 44 in the direction of opening the cooling temperature adjusting member 32. At this time, the operation of the air blowing mechanism 38 is temporarily stopped, but the air blowing may be continued as long as the blown air does not cause dust and the like to be scattered around.

On the other hand, when the preform is conveyed to the stretch blow molding station 18 and set, the cooling operation for the preform is executed.

That is, in this case, the cooling temperature adjusting member 32 that is still open moves toward the position where the preform is set. Therefore, in the slide drive unit 36, the base 36A moves in the direction of entering the set position of the preform through the drive from the linear drive member 36C. Further, the air cylinder 34 on the base 36A is also interlocked with this, and moves to the set position of the preform 100 shown by the chain double-dashed line in FIG. When the cooling temperature adjusting member 32 is arranged at the set position of the preform, the air cylinder 34 moves the driven lever 44 in the direction of closing the cooling temperature adjusting member 32, whereby the inner portion of the cooling temperature adjusting member 32 is moved. The plate 32A faces the outer peripheral surface of the preform. When air is blown from the air blowing mechanism 38 in this state, the temperature of the outer peripheral surface of the preform 8 on which the air is blown is lowered. Therefore, in this part, that is, in the part where the temperature is higher than the other parts, the temperature is changed to a temperature lower than the controlled temperature, and it is possible to suppress an excessive stretching amount during stretch blow molding. become.

Further, if the air outlet is made small and spot cooling (temperature control) is performed, it becomes possible to cool a local portion. Furthermore, as shown by reference numeral 32A2 in FIG. 4, it is possible to provide a slit-shaped opening and provide a filter inside thereof to diffuse the air. It will hit the air. This makes it possible to moderate the temperature change with the surrounding area.

FIG. 4 shows a case where a filter is used by diverting a part of the divided blocks.

Therefore, when the filter is used, all blocks provided with air outlets may be targeted or may be mixed locally.

As described above, according to this embodiment, the temperature of a desired portion can be controlled by a simple method of blowing air. In addition, the temperature control performed before such stretch blow molding can be performed within the injection molding time, considering that the stretch blow molding time is significantly shorter than the injection molding time. It is possible to optimize the wall thickness of the molded product without increasing the length.

In the above-mentioned embodiment, the temperature control is performed on the assumption that the temperature-controlled part is cooled, but the present invention is not limited to such control. For example, in the height direction and the circumferential direction of the preform, the temperature at the thin portion where the temperature tends to be relatively high when the temperature is controlled is taken as a reference, and for the thick portion where the temperature rise is less than this position. The temperature may be changed to the temperature required for stretching by heating by heating. In this case, of course,
Hot air is supplied from the air blowing mechanism. Further, as a method of adjusting the temperature control condition of the desired temperature control portion, there are a method of adjusting the flow rate of the blown air for each zone, a timer setting of the blowing time of the air, and the like.
Furthermore, the amount of air supplied from the air blowing mechanism is not limited to a constant amount, and may be changed according to the amount of heat radiation or the amount of heat to be changed. Further, the inner plate provided inside the cooling temperature control member may have a structure that can be replaced according to the external dimensions of the preform.

Further, the structure of the temperature control mechanism is not limited to the air blowing structure, and may be, for example, a cooling temperature control member which comes into contact with the surface of the preform. In this case, as shown in FIG. 7, a temperature control member having an inner surface shape larger than the shape of the preform is arranged on the outer periphery of the preform, and low-pressure air is blown into the preform so that the preform is heated to this temperature. The temperature is adjusted by inflating to the inner surface of the temperature adjusting member and bringing the outer surface of the preform into contact with the inner surface of the temperature adjusting member. According to such a method, the thermal conductivity can be cooled more effectively than air.

In the example shown in FIG. 7, as a matter of course, temperature control is performed in each block in order to locally set the desired temperature condition.

Furthermore, the present invention can be applied to the one-stage system described in the embodiments, for example, to a structure in which the temperature control station described in the embodiments is not provided.

[0050]

As described above, according to the present invention, the zone divided in the height direction and the circumferential direction of the preform is selected and the temperature is independently changed before the stretch blow molding. If the surface temperature at the position where it should not be stretched has reached a temperature at which it can be easily stretched, or when the surface temperature at the position to be stretched is at a temperature at which it is difficult to stretch, change the temperature at that position. be able to. Therefore, the amount of extension is suppressed particularly in a portion where the temperature is high. Therefore, it is possible to avoid a situation in which the position where the temperature is high is stretched by a predetermined extension amount or more and the wall thickness becomes too thin, thereby making the wall thickness of the molded product uniform. It becomes possible to prevent the mechanical strength from decreasing.

[Brief description of drawings]

FIG. 1 is a plan view for explaining an overall configuration of a base used in a molding apparatus according to the present invention.

FIG. 2 is a plan view schematically showing the structure of a stretch blow molding station of the molding apparatus shown in FIG.

3 is a perspective view showing an overall configuration of a temperature changing mechanism used in the stretch blow molding station shown in FIG.

FIG. 4 is a perspective view showing the structure of a part of the temperature changing mechanism shown in FIG.

5 is a plan view of the temperature changing mechanism shown in FIG.

6 is a side view of the temperature changing mechanism shown in FIG.

FIG. 7 is a side view showing a modified example of the temperature changing mechanism shown in FIG.

[Explanation of symbols]

 10 Molding Equipment 16 Temperature Control Station 18 Stretch Blow Molding Station 30 Temperature Control Mechanism 32 Cooling Temperature Control Member 100 Preform

Claims (4)

[Claims] 1. A molding apparatus comprising a stretch blow molding section for stretch blow molding a preform to form a hollow body, wherein the preform conveyed to the stretch blow molding section is divided in a height direction and a circumferential direction. The molding apparatus is provided with a temperature control mechanism capable of controlling the temperature of each of the divided zones. 2. The molding apparatus according to claim 1, wherein the temperature control mechanism has a configuration capable of independently changing the temperature of the selected zone. 3. The molding apparatus according to claim 1, wherein the temperature adjusting mechanism has a structure formed by blowing air. 4. The molding apparatus according to claim 1 or 2, wherein the temperature control mechanism blows low pressure blow air into the preform to bring the preform into contact with the inner surface of the preform to control the temperature of each zone. A molding device characterized in that