JPS5837896B2 - Injection blow molding method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an injection blowing method in which the temperature of the core pin is controlled to be below a predetermined temperature from the point at which the shaped article is taken out until it reaches the injection mold.

In injection blow molding, the injection core is also used as the blow core, so if continuous molding is performed, the temperature of the core pin will rise.
The injection-shaped parison adheres to the core pin, making blow molding impossible.

Therefore, in conventional methods, temperature control was performed by circulating heat transfer oil or the like inside the core pin, and air was blown onto the core pin to perform forced cooling from the outside.

However, the use of heat transfer oil is limited to core pins with a large diameter, and when forming a container with a small diameter (small diameter core pins used in this case are difficult to use due to the internal structure).

In addition, the external forced cooling method has disadvantages in that it is difficult to uniformly cool the entire core pin, and a cooling step must be provided during certain cycles.

This invention does not require special measures for a certain molding device, the molding cycle is the same as the conventional one, the core pin can be cooled within the time it takes to transfer the core pin to the injection mold, and the core pin is cooled from inside the core pin. Not only is it possible to achieve uniform cooling, but it can be performed regardless of the diameter of the core pin.

The present invention will be explained in detail below using illustrated examples.

FIG. 1 shows one embodiment of an injection blow molding machine, in which 1 is an injection mold, 2 is a blow mold, and 3 is a core pin, which is reciprocated between the two molds by a rotating device 4.

An air valve 6 is provided at the tip of the core pin 3, which is integrally formed with a rod 5 inserted into the core pin 3.
The air used to blow mold the parison γ on the outside of the core pin into a hollow shaped product 8 passes through a spiral air passage 9 provided around the rod 5, and is opened and closed by an air valve 6. It is ejected from the blow hole 10.

The method of the present invention in which the core pin 3 is cooled by air jetted from the tip will be explained in order according to the steps shown in FIGS. 3 and 4.

Fig. 3: In the injection mold 1, a parison 7 is formed around the pin 3a, while in the injection mold 2, the air valve 6 of the core pin 3b is opened and air is blown out from the injection hole 10 to form a hollow molded product. Show off 8.

Then stop blowing out the air.

FIG. 4 The parison 7 is released from the injection mold together with the core pin 3a by moving the rotating device 4, and the hollow molded product 8 is extracted from the core pin 3b after being released from the blowing mold 2.

5 and 6 The core pin 3a is transferred to the blowing mold 2 and the core pin 3b is transferred to the injection mold 1 using the rotating device 4 as shown in FIGS.

At this time, the air valve 6 is opened in the core pin 3b to blow out air while it reaches the injection mold 1, and the core pin 3b is cooled from inside by the air flowing through it.

FIG. 7: Move the rotating device 4 to its original position, close the mold, and perform injection and/or lower blowing again.

As described above, this invention is used to control the temperature of the core pin during the transition from the hollow shaped product removal position to the injection mold, so there is no need to provide a control process during the hollow shaped process. Moreover, since temperature control is performed by blowing out air used for blowing, no special device for temperature control is required.

Furthermore, since the temperature is controlled from within the core pin, the temperature is uniform, and there is no non-uniformity that occurs when control is performed from the outside, and there is no possibility of parison adhesion even if continuous shaping is performed.

[Brief explanation of drawings]

The drawings illustrate the injection blow molding method according to the present invention; FIG. 1 is a partial vertical sectional view of the machine, FIG. 2 is a vertical sectional view of the main part of the core, and FIGS. FIG. 3 is a schematic vertical sectional view sequentially explaining the steps of the invention. 1...Injection mold, 2...Blowing mold, 3
, 3a, 3h...Core pin, 5...Tatsudo, 6...Air valve, 7...Parison, 8...Hollow shape item, 9...air passage, 10...blow hole.

Claims (1)

[Claims] 1 A core pin with an air blow hole at the tip is transferred to a blowing mold together with a parison formed in an injection mold to blow into a hollow or shaped product, and after the hollow or shaped product is taken out, the core pin is pressed again. When the core pin is transferred to the injection mold, air is blown out from the tip while the core pin reaches the injection mold position from the molded product take-out position to control the core pin temperature from the inside to a predetermined temperature or less. Injection blow molding method.