JPH0428215B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method and an apparatus for molding a hollow plastic container by biaxially stretching a thermoplastic resin such as polyethylene terephthalate. The present invention relates to a cooling method and apparatus for a plastic container molding method in which heat setting is performed by heating and holding for a period of time.

Conventional technology Polyethylene terephthalate, polyethylene,
When molding containers such as hollow bottles with thermoplastic resin such as polypropylene, for example, Japanese Patent Application Laid-Open No. 54-93062
As described in the above publication, it is common to carry out biaxial stretching molding in order to improve the physical and mechanical properties. However, plastic containers obtained by biaxial stretching have poor thermal stability;
If coffee, juice, etc. are filled immediately after high-temperature sterilization, the bottle will be heated by the filled liquid and cause softening and shrinkage deformation. To prevent this, conventionally, after molding, heat setting is performed by heating and holding at a constant temperature in the mold for a certain period of time.

In the conventional bottle molding method in which heat setting is performed within the mold, a parison heated to a stretching temperature is inserted into a blow molding mold that has been heated to a predetermined temperature in advance, and biaxially stretched molding is performed. When the bottle is stretch-molded, the side wall of the bottle is brought into close contact with the inner surface of the mold by the pressurized fluid of blow molding, and the internal pressure is maintained for a certain period of time to heat set the bottle side wall depending on the temperature of the inner wall of the mold. Subsequently, a cooling fluid is circulated inside the bottle or the mold is rapidly cooled to a temperature at which the bottle can be taken out, and then the mold is opened and taken out.

Problems to be Solved by the Invention In the conventional method described above, it is necessary to raise the temperature of the mold for heat setting, and on the other hand, after heat setting, it is necessary to cool the mold to a temperature at which it can be taken out without deformation. In this case, the pressurized fluid had to be removed and a cooling fluid had to be supplied instead, which lengthened the molding cycle time and caused extremely low production efficiency.

The present invention was devised in view of the above circumstances, and provides a novel method and apparatus for reducing cooling time and increasing production efficiency by dividing a mold into a heating mold and a cooling mold. The purpose is to provide the following.

Means for Solving the Problems In the first invention, a heating mold and a cooling mold are circulated together, a preform is received in the heating mold and biaxially stretched, and then a preform is formed for a predetermined period of time. The hollow container is held under pressure and heat set, and then the hollow container immediately after heat setting is transferred from the heating mold to the cooling mold, and the side wall of the container is brought into close contact with the inner surface of the mold by pressurized fluid in the cooling mold. I tried to cool it down.

The second invention is an apparatus used to carry out the first invention, and in the invention, a heating mold for biaxially stretching and heat-setting the preform P is placed on the blow wheel 6 which is rotationally driven. A plurality of cooling molds 7 and cooling molds 8 for cooling the hollow container after heat setting were arranged alternately. And blow wheel 6
A transfer wheel 9 for transferring the hollow container from the heating mold 7 to the cooling mold 8 was arranged around each of the molds.

Function: The preform P heated to an appropriate temperature is inserted into a heating mold using the transfer wheel 5, biaxially stretched in the heating mold 7, and then held under pressure for a predetermined period of time for heat setting. When the heating mold reaches the transfer location by the rotation of the blow wheel 6, the hollow container after heat setting is taken out from the heating mold 7 by the transfer wheel 9 and inserted into the subsequent cooling mold 8. . The container is rapidly cooled by blowing pressurized fluid into the cooling mold to bring the side wall of the container into close contact with the inner surface of the mold. The cooled container is removed from the cooling mold by means of a transfer wheel 9.

EXAMPLES Hereinafter, the apparatus of the present invention and the molding method for molding a hollow bottle will be described in detail based on the examples shown in the drawings.

In the figure, reference numeral 1 is a heating wheel for the preform, and holding parts 2 for receiving and rotatably holding a mandrel supporting the preform are arranged at equal intervals on its circumferential surface, and the preform P is a heating wheel. As it rotates, it is heated by heaters 3 disposed around it while rotating on its own axis. Reference numerals 4 and 4' denote a heating wheel that is provided following the heating wheel and constitutes a region for equalizing the temperature of the preform, and holding parts are arranged at equal intervals on its circumferential surface, similar to the heating wheel. It is now possible to transport preforms. 5 is a soaking wheel 4' and a blow wheel 6
This is a conveyor wheel that relays between the blow molding molds 7.

Reference numeral 6 denotes a blow wheel which constitutes the main part of the present invention, and includes a heating mold 7 for biaxially stretching and heat-setting a preform on its circumference, and a hollow bottle formed by the heating mold. A plurality of cooling molds 8 for receiving and cooling the water are alternately arranged and rotated by a drive source (not shown). The heating mold 7 is constantly heated to a predetermined temperature (which varies depending on the type of molding material, etc.), and the preform is stretched in the mold by a stretching rod and a pressure fluid.
It is designed to be axially stretched. After molding, the internal pressure is maintained for a certain period of time and the bottle side wall is heat set by the temperature of the inner wall of the mold. The cooling mold 8 is kept at room temperature or at a temperature (approximately 70° C.) having an appropriate temperature difference from the heating mold 7.
A pressurized fluid is blown into the bottle to bring the side wall of the bottle into close contact with the inner surface of the mold for rapid cooling.

In this embodiment, the biaxial stretching and heat setting process in the heating mold 7 is performed during approximately one rotation of the blow wheel 6, and cooling is performed in the cooling mold 8 during approximately one rotation of the blow wheel 6. It's getting old. However, the invention is not limited to this, and various embodiments can be considered, such as performing the biaxial stretching and heat setting process in the heating mold 7 in half a rotation, and performing the cooling process in the cooling mold 8 in the remaining half rotation. It will be done.

Further, the heating mold 7 may have an intermediate shape and be used as a primary molding mold, and the cooling mold 8 may have a final bottle shape and be used as a secondary molding mold.

Next, the means for transferring the bottle from the heating mold 7 to the cooling mold 8 and the means for taking out the bottle from the cooling mold 8 will be explained.

The transfer wheel 9 for transferring bottles is the transfer wheel 1 for taking out the bottles from the cooling mold 8.
1 and a transfer wheel 5 for inserting the preform into the heating mold 7. The number of transfer levers 10 of the transfer wheel 5 is set to an odd number, and the transfer levers 10 rotate in synchronization with the pitch between the respective molds, thereby receiving and cooling the heating molds. The molds can be fed alternately and sequentially. In the illustrated example,
The number of transfer levers 10 is set to three, but if you want to transfer in a short time, use one, and if you want to transfer for a long time, you can increase the number of transfer levers 10.

The transfer wheel 11 rotates so that the pitch between the transfer levers 12 is equal to the pitch between the cooling molds, and receives the hollow container W formed from the cooling mold 8 into the supply/discharge wheel 15. It's starting to be handed over.

In the figure, 17 is a conveyor for discharging the hollow bolts from the molding machine, and 18 is a chute 1.
Supply and discharge wheel 1 receives preform P from 9
A star wheel 5 is supplied to the heating wheel 1, and a conveyance wheel 16 is a conveyance wheel that relays the supply/discharge wheel and the heating wheel 1.

With the above structure, the preform heated to an appropriate temperature by the heating wheel 1 passes through the soaking wheels 4 and 4', and the temperature of the inner and outer surfaces becomes uniform, and the preform is transferred from the soaking wheel 4' to the transfer wheel. 5
It is inserted only into the heating mold. The heating mold into which the preform is inserted is immediately closed, and the preform is biaxially stretched and heat set using a stretching rod and pressurized fluid. The heating mold continues to rotate, and the mold opens and continues to rotate with the internal pressure released or some internal pressure maintained near where the transfer wheel 11 is installed, and the transfer wheel 9 for transfer is released. Once there, the hollow container is removed from the mold 7 by the transport wheel 9. Thereafter, the preform P is supplied again by the conveyor wheel 5 at the initial position, and the same process is repeated.

On the other hand, the transfer wheel 9 that has taken out the heat-set hollow bottle inserts the hollow container backward into the cooling mold 8 according to the number of levers, and then takes it out in the same way and repeats the insertion operation. The cooling mold 8 into which the bottle is inserted is immediately closed, and pressurized fluid is blown into the hollow bottle again, causing the side wall of the container to tightly contact the inner surface of the mold, which is maintained at room temperature, while rotating. Then, the internal pressure is released before the discharge transfer wheel 11 and the mold is opened. Thereafter, the hollow container W formed by the transfer wheel 11 is taken out and discharged to the conveyor 17 via the supply/discharge wheel 15. The hollow bottle immediately after heat setting is inserted into the cooling mold from which the hollow bottle has been taken out by the transfer wheel 9, and the same process is repeated thereafter.

Effects Since the present invention is configured as described above, it has the following remarkable effects.

() Separate heating and cooling molds allow for rapid cooling with the cooling mold immediately after heat-setting, reducing cooling time and dramatically increasing production efficiency. Improved.

() Since the heating mold is constantly heated without repeating heating and cooling as in conventional methods, there is no wastage of energy and it is economical.

() Since the hollow container is brought into close contact with the inner surface of the mold using pressurized fluid again in the cooling mold, especially in the case of a hollow container with an uneven pattern formed thereon, the pattern is clearly formed.

() Since the cooling mold and the heating mold are arranged alternately, the hollow containers of the heating mold and the cooling mold can be transferred in a short time.
In addition, in the case of molding that does not require heat setting, all the molds are converted to or replaced with regular molds, the function of the transfer wheel 9 is stopped, and the rotational speed of the transfer wheels 9 and 11 is changed so that all the molds are Can be molded into regular containers.

[Brief explanation of drawings]

The drawing is a schematic plan view of a plastic container forming apparatus according to the present invention. 1: heating wheel, 3: heater, 4,4':
Soaking wheel, 5, 9, 11: Transfer wheel,
6: Blow wheel, 7: Heating mold, 8: Cooling mold.

Claims (1)

[Claims] 1. In a method for forming a hollow container by blow molding a preform heated to a stretch forming temperature, a heating mold and a cooling mold are disposed on a rotatably driven blow wheel, and the heating mold is The preform is biaxially stretched in a mold, the hollow container is held under pressure for a predetermined time after molding, and the outer wall of the hollow container is brought into close contact with the inner wall of the heating mold using a pressurized fluid to heat set. While the pressurized fluid in the hollow body is completely evacuated or partially kept in pressure, it is transferred to the cooling mold, and the outer wall of the hollow container is cooled again by the pressurized fluid in the cooling mold. A method for molding hollow plastic containers that is characterized by cooling by cooling the container in close contact with the inner wall of the mold. 2. A plurality of heating molds for shaping and heat-setting the hollow container by biaxial stretching and cooling molds for cooling the hollow container after heat-setting are arranged alternately on the blow wheel which is driven to rotate, and the blow wheel An apparatus for forming hollow plastic containers, characterized in that a transfer wheel for transferring the hollow container from the heating mold to the cooling mold is disposed around the heating mold.