JPH0428217B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an apparatus for biaxially stretching a thermoplastic resin such as polyethylene terephthalate to form a hollow plastic container.

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 stated in the publication, in order to improve its physical and mechanical properties, a preform is molded by injection molding or pipe extrusion molding, and after being heated to the appropriate temperature for stretching, it is inserted into a blow molding mold. Biaxial stretching is performed using a stretching rod and pressurized fluid. When heating the preform to the appropriate temperature for stretching again, if heating is performed from the outer surface of the preform using an electric heater or the like, a temperature difference will occur between the inner and outer surfaces of the preform immediately after heating because the preform is a thin cylinder with a bottom. If stretching is carried out in a state where there is a temperature difference between the inner and outer surfaces of the preform, problems such as non-uniform wall thickness will occur.

Therefore, conventionally, a soaking time is provided to balance the temperature of the inner and outer surfaces of the preform before inserting it into the blow molding die after heating.

Problems to be Solved by the Invention However, the time required for the temperature of the inner and outer surfaces to reach an equilibrium state (soaking time) naturally differs depending on the thickness of the preform, but the conventional method described above is Since only a constant soaking time can be provided at all times, the molding speed may be regulated depending on the soaking time.

Therefore, it is preferable to be able to appropriately select the soaking time while setting each molding speed to the maximum, but in the above case, since the soaking time is constant,
I couldn't do that.

Therefore, the present invention was devised to solve the above-mentioned problems, and an object of the present invention is to provide a new hollow container molding machine that can change the soaking time depending on the thickness of the preform.

Means for Solving the Problems Means for achieving the above object will be explained based on drawings corresponding to embodiments.

The present invention has a heating wheel 1 and a blow wheel 7.
A plurality of soaking wheels 3, 4, and 5 for transporting the preform P are provided between them, and by selectively combining the soaking wheels, the transport path of the preform is switched, and the soaking time is set to 2. It is possible to set more than one level.

Effect: In the case of a thick preform P, if you remove the soaking wheel 5 for the short pass in advance,
The preform P heated by the heating wheel 1 is supplied to the blow molding die 8 of the blow wheel 7 via the soaking wheel 5 and the soaking wheel 4. Therefore, the soaking time becomes longer and the preform P becomes thicker.
However, the heat is uniform inside and outside.

In addition, in the case of a thin preform P, if a soaking wheel 5 for the short pass is installed, the preform P heated by the heating wheel 1 will pass through the soaking wheel 5 for the short pass and the soaking wheel 4. It is supplied to the mold 8 of the blow wheel 7. Therefore, the soaking time is shortened, and a soaking time that satisfies the soaking conditions for thin preforms can be set.

Embodiments Hereinafter, preferred embodiments of the present invention will be described based on the drawings.

Reference numeral 1 denotes a heating wheel for the preform.Holding parts for receiving and rotatably holding the mandrel supporting the preform are arranged on its circumferential surface at equal intervals, and the preform P is heated as the heating wheel rotates. While rotating, it is heated by heaters 2 placed around it. 3,
Reference numerals 4 and 5 denote heating wheels for thermally balancing the inner and outer surfaces of the preform, and holding portions are arranged at equal intervals on the circumferential surface of the wheels, similar to the heating wheels. As shown in the figure, the soaking wheel 3 is arranged to receive the preform from the heating wheel 1 and pass it to the soaking wheel 4, while the soaking wheel 5 forms a short pass and its outer diameter is the same as that of the soaking wheels 3 and 4. It is formed to be smaller than the heating wheel 1 and is removably installed so as to relay the heating wheel 1 and the soaking wheel 4. Therefore, in this embodiment, in the case of a thick preform, the soaking wheel 5
The preform P is transferred from the heating wheel 1 to the soaking wheels 3 and 4, and in the case of a thin preform, by installing the soaking wheel 5, the preform P is transferred from the heating wheel 1 to the soaking wheels 5. It is designed to be conveyed to the soaking wheel 4 through the.

6 is a conveyance wheel that relays between the soaking wheel 4 and the blow molding die 8 of the blow wheel 7.
Further, reference numerals 9 and 12 are conveyance wheels that relay between the blow wheel 7 and the supply/discharge wheel 10 and between the supply/discharge wheel 10 and the heating wheel 1, respectively. Furthermore, 11 is a conveyor for carrying out the molded hollow container W, and 13 is a star wheel for receiving the preforms P from the chute 14 and feeding them at equal intervals to a supply/discharge wheel.

The hollow container forming machine configured as described above operates as follows.

A preform P formed by injection molding, pipe extrusion molding, or the like is supplied from a chute 14 via a star wheel 13 to a mandrel held by a supply/discharge wheel 10. The preform P supported by the mandrel is supplied together with the mandrel from the supply/discharge wheel 10 via the conveyance wheel 12 to the holding part of the heating wheel 1, and is heated by the heater 2 while rotating with the rotation of the heating wheel 1. . If the preform P is thick,
Since the soaking wheel 5 has been removed beforehand, the preform passes through a long course from the heating wheel 1 to the soaking wheels 3 and 4, during which the temperatures of the inner and outer surfaces of the preform are brought into equilibrium. Further, when the preform P is thin, by installing the soaking wheel 5, the preform P is conveyed to the soaking wheel 4 via the soaking wheel 5, so that the soaking time is shortened.
After that, the soaked preform is transferred to the conveyor wheel 6.
is supplied to the blow molding die 8 and biaxially stretched by a well-known method. The biaxially stretched plastic hollow container is taken out from the mold 8 by a conveyor wheel 9, separated from the mandrel by an inlet/outlet wheel 10, and transferred to an outlet conveyor 11.
is discharged.

In the above embodiment, three soaking wheels were provided so that the soaking time for each stage could be selected. There are various aspects, such as the ability to obtain three stages of soaking time by providing a heat soaking wheel that relays the heat soaking wheel 3 and the heating wheel at the front part of the heating wheel in the rotational direction. However, the present invention is not limited to the above embodiments.

Effects As a result of the present invention configured as described above, the soaking time can be selected depending on the wall thickness of the preform, so that the preform can be placed in the blow molding mold at the appropriate stretching temperature when the temperature difference between the inner and outer surfaces of the preform is eliminated. can be supplied. Therefore, the molding speed is not restricted by the soaking time of the preform, and molding can be performed at the highest speed suitable for each preform, thereby increasing production efficiency. Furthermore, the present invention has remarkable effects compared to conventional ones, such as a simple configuration because the soaking time can be changed by simply attaching and detaching the soaking wheel.

[Brief explanation of drawings]

The drawing is a plan view of an embodiment of a plastic hollow container forming machine according to the present invention. 1: heating wheel, 2: heater, 3, 4,
5: Soaking wheel, 6, 9, 12: Conveyance wheel, 7: Blow wheel, 8: Blow molding mold,
10: Supply and discharge wheel.

Claims (1)

[Claims] 1. In a molding device that biaxially stretches a thermoplastic resin to mold a hollow container, the temperature of the inner and outer surfaces of the preform is controlled while the heated preform is conveyed between a heating wheel and a blow wheel. A hollow plastic container characterized in that a plurality of equalizing wheels are provided, and by selectively combining the equalizing wheels, the preform soaking time can be set in two or more stages. Molding equipment. 2. The plastic hollow container molding apparatus according to claim 1, wherein a heat soaking wheel forming a short path among the heat soaking wheels is detachably provided.