JPH0423619B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for forming a threaded cap of a biaxially stretched blow-molded synthetic resin bottle, and the present invention relates to a method for forming a threaded cap of a biaxially stretched blow-molded synthetic resin bottle, in which the thread can be easily formed around the cap while causing the cap to undergo sufficient stretching. The purpose is to establish

Polyethylene terephthalate resin (hereinafter simply referred to as
The bottle (made of PET resin) is molded by biaxially stretching and blowing a primary molded product in the shape of a cylinder with a bottom. At the time of molding, this threaded portion was fixed to a part of the mold, so that the threaded portion was not stretched at all, and the bottle remained as it was after being molded.

For resins such as PET resins, which exhibit excellent properties such as content resistance, gas barrier properties, and mechanical strength only after being sufficiently stretched, the unstretched parts, even if it is only the mouth part, If this remains, it will reduce the value of the product.Also, since the mouthpiece is molded thickly to ensure strength, a large amount of resin material is required, especially for wide-mouthed bottles. There were drawbacks and inconveniences such as being uneconomical and increasing weight.

The present invention relates to a screw cap molding method developed to eliminate the above-mentioned conventional drawbacks, in which a threaded cap is formed on the inner periphery of the stretched synthetic resin bottle after biaxial stretch blow molding is completed. It is configured to displace while pressing a jig having a mold surface corresponding to a threaded groove provided on the circumference of the mouth tube mold surface of the body mold.

An embodiment of the present invention will be described below with reference to the drawings.

First, reference numeral 1 in the figure is a bottle molding die, and a mold surface is formed to mold a bottle 6 having a bottomed cylindrical shape. The diameter is slightly smaller than the diameter of the body 7 of the bottle body 6, and the mouthpiece mold surface 2 of the molding die 1 is also formed corresponding to the mouthpiece 8, and this mouthpiece mold surface 2 A spiral groove 3 is provided around the periphery.

Next, reference numeral 4 is a primary molded product, which has a bottomed cylindrical shape molded from PET resin, but the opening upper end 5 that forms the mouthpiece 8 of the bottle body 6 is thin so that it can be easily stretched. Moreover, it has a substantially funnel shape with a large diameter at the opening end.

Opening upper end 5 of primary molded product 4 having such a configuration
The end is fixed to the mouth mold surface 2 of the bottle mold 1 and biaxial stretch blow molding is performed.

By this biaxial stretching blow, the primary molded product 4 is formed into a bottle 6, but in this case, the body 7 of the bottle 6 is
Of course, the mouth tube 8 is subjected to sufficient stretching, but the mouth tube 8 is also stretched to a certain extent, and a thread 9 is formed corresponding to the screw groove 3 provided around the mouth tube mold surface 2. Ru.

However, as can be seen from the enlarged view of FIG. 3, this thread 9 cannot be formed into a completely grooved shape by mere stretch blowing. That is, the open upper end 5 of the primary molded product 4 is deformed as it bites into the threaded groove 3 during blow molding.
The amount of biting is shallow and is not formed to a sufficient extent to function as the thread 9, and the amount of stretching is also insufficient.

Therefore, immediately after the primary molded product 4 is biaxially stretched and blown as described above to complete the forming of the bottle 6, dislocation is carried out along the inner periphery of the cap 8 while pressing a predetermined jig 10 against the inner periphery of the cap 8. Let it happen.

This jig 10 has a screw thread on the circumferential surface of a main body part 11 having a linear cylindrical shape having a diameter smaller than the inner diameter of the molded mouth pipe 8 (approximately 1/2 in the illustrated embodiment). It has a structure in which a screw blade 12 having the same lead angle as that of the groove 3 is provided around the circumference, and the screw blade 12 is pressed against the inner periphery of the mouth tube 8 immediately after molding in a manner corresponding to the screw groove 3. In this state, it is dislocated along the inner circumference of the mouth tube 8.

Due to such rolling of the jig 10, the thread 9 portion previously formed on the mouth tube 8 is further deformed as the thread blade 12 becomes the mold surface corresponding to the thread groove 3, and the thread groove 3 is further deformed. As a result, sufficient elongation is applied to the mouth tube 8, and a sufficient shape as the thread 9 can be obtained.

Note that the numerical relationship between the diameter of the jig 10 and the inner diameter of the mouth tube 8, the position at which the jig 10 starts pressing against the inner peripheral surface of the mouth tube 8, the amount of displacement of the jig 10, etc. are to be obtained in the mouth tube 8. It will be selected depending on the form of the thread 9.

As is clear from the above description, the method for molding a threaded cap for a synthetic resin bottle of the present invention requires a molding die 1.
A mouth mold surface 2 is also provided in a part of the bottle, so that stretching is applied to the mouth tube 8 of the bottle 6 to be biaxially stretched blow-molded. Since the threaded groove 3 is provided around the circumference, the original shape of the threaded thread 9 is formed on the mouthpiece 8 when the mouthpiece 8 is stretched, and the jig has a screw blade 12 that becomes the mold surface corresponding to the threaded groove 3. Mouth tube 8 in a still soft state immediately after molding 10
By pressing against the inner periphery and dislocating it, the mouth tube 8
can be sufficiently stretched, and a sufficient number of threads 9 can be provided around the mouth tube 8.

Therefore, according to the screw cap molding method of the present invention, it is possible to give sufficient elongation to the cap of the bottle, so it is possible to obtain a bottle with excellent contents resistance, etc., and the cap has a thin wall. However, it has excellent strength, can provide a satisfactory thread around the mouthpiece, reduces the amount of resin material, reduces the weight of the bottle itself, and is easy and accurate to mold. It has many excellent functions and effects, such as being easy to configure.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a mold and a primary molded product showing an embodiment of the present invention. FIG. 2 is a sectional view of the mold and blow bottle. FIG. 3 is an enlarged sectional view of the mouthpiece. Explanation of symbols, 1; Molding die, 2; Flap mold surface, 3; Thread groove, 4; Primary molded product, 5; Opening upper end, 6; Bottle body, 8; Mouthpiece, 9; Thread , 10; jig, 12; screw blade.

Claims (1)

[Claims] 1. The open end of the primary synthetic resin molded product is fixed to a bottle molding mold with a threaded groove formed around the face of the mouth mold, and biaxial stretch blow molding is performed, and the bottle is obtained after completion of the blow molding. A synthetic resin that is dislocated along the inner periphery of the mouth tube while pressing a jig having a mold surface corresponding to the mouth tube mold surface with a diameter smaller than the diameter of the mouth tube. A method for forming a screw cap for a bottle body.