JPS6016894B2 - Method for stretch-molding the neck of a stretch-molded bottle molding piece - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a capital stretch molding method for a piece that is injection molded as a primary molded product of a polyethylene terephthalate resin dust body to be stretch blow molded.
More specifically, the purpose is to simplify the stretch-molding operation and maintain dimensional accuracy in the longitudinal direction of the neck portion to be stretch-molded.

Polyethylene terephthalate resin has come to be used in many wide fields due to its excellent physical properties and durability. It was not until the manufactured product was stretch-molded that it became effective.

For this reason, when molding a dust body made of polyethylene terephthalate resin, the molding method first involves injection molding to form the primary molded product into a bottomed cylindrical shape so that sufficient stretching can be easily applied. Shape the pieces,
A so-called injection flow molding method was adopted in which this piece was stretch-blow molded.

It is true that the body of the weight body molded by this injection flow molding method undergoes sufficient stretching and exhibits many of the excellent physical properties and durability of polyethylene terephthalate resin. Compared to the other parts, the capital, which is the rough fixing part of the piece to the mold during blow molding, cannot be stretched at all, making it impossible to fully demonstrate the twisted physical properties and durability of polyethylene terephthalate resin. There wasn't.

For this reason, for example, if a dust body contains high-concentration alcohol as a liquid content, the alcohol will not cause any damage to the arms, but the alcohol will permeate the neck, causing it to turn white and become mechanically brittle. Various inconveniences have occurred, such as the formation of a large number of thin cracks, which completely impairs the sealing effect.

The present invention was devised to eliminate the disadvantages of the above-mentioned ink bodies made of polyethylene terephthalate resin. In this method, a cylindrical body having a large outer diameter is inserted and the neck portion is stretched in the radial direction.

The method of the present invention will be explained below with reference to the drawings.

The method of the present invention is carried out by an elongated body E inserted into the neck P2 of the piece P. The stretched body E has a cylindrical shape with a height not smaller than the height of the neck P2 of the piece P which is injection molded into a bottomed cylindrical shape and an outer diameter that matches the desired amount of stretching of the neck P2. Constant diameter part E2
and a tapered surface part E, which is integrally molded into a pointed shape that gradually decreases the outer diameter at the tip of the fixed position 2, and this elongated body E also has a horn that generates ultrasonic waves. Also serves as.

The outer surface of the stretched body E is an extremely smooth surface, so that when the stretched body 8 enters the neck P2 while pushing and expanding the neck P2, as much friction as possible is created between the neck P2 and the stretched body E. This ensures that no resistance occurs.

The height of the constant diameter portion B2 of the elongated body B is preferably equal to the height of the neck portion P2 or slightly larger than the height of the capital P2, and as in the illustrated embodiment, a step is provided at the base end of the constant diameter portion E2. Part E
3, the insertion limit of the elongated body E into the neck P2 can be easily set, and the mouth edge of the neck P2 can be press-molded into a desired shape.

In addition, it is desirable that the slope angle of the tapered surface portion E be as gentle as possible from the viewpoint of reducing the frictional resistance between the neck portion P2 and the stretched body B. In order to give
Set to an appropriate value depending on the thickness of No. 2, amount of stretching, etc.

The method of the present invention is carried out using the entrusted stretched body E, and first, the injection-molded piece P is held immovably at a location from the body part P to the bottom part.

With respect to this piece P, the elongated body E is arranged so as to coincide with the central axis of the piece P and to be movable along this central axis.

In this way, the disposed elongated body E is slowly advanced so as to enter the neck P2 from the mouth edge while still generating ultrasonic waves.

When the stretched body E enters into the neck P2 and starts to come into contact with the capital P2, the neck P2 is heated by the ultrasonic waves emitted by the stretched body E to a temperature that produces a stretching effect, and at the same time, the stretched body By the movement of E into the neck portion P2, the neck portion P2 is stretched in such a manner that both tapered portions E are pushed and expanded in the radial direction.

During the stretch-forming operation of the neck P2, the capital P2 super-moves while contacting the surface of the stretched body E, so it seems that a large frictional resistance is generated between the stretched body E and the neck P2. The stretched body E generates ultrasonic waves while stretching the neck P2.
The frictional resistance generated between the stretched body E and the capital P2 is extremely small, so that the neck P2 can be stretched extremely smoothly.

In this way, the elongated body E advances into the neck portion P2, and the elongated body E completes the stretching of the neck portion P2 at the position where the constant diameter lamp 2 of the elongated body E faces the entire capital P2.

In this way, the method of the present invention only requires that the stretching body E, which is generating ultrasonic waves, enter the neck P2. It is preferable to heat the entire capital P2 or the inner surface portion thereof to some extent before the elongated body E moves into the capital P2.

In this way, by heating the neck portion P2 in advance, the heating rate of the neck portion P2 by ultrasonic waves becomes faster, and the speed at which the elongated body E penetrates into the neck portion P2 can be increased accordingly.

As described above, the present invention inserts the elongated body B, which also serves as a horn for generating ultrasonic waves, into the neck P2, so that the frictional resistance between the neck P2 and the elongated body E is extremely small. Since P2 is stretched and deformed only in the direction that increases its diameter, there is no deviation in height due to the stretching operation. Even with P2, stretch molding can be performed while maintaining high dimensional accuracy.

As is clear from the above description, the present invention uses ultrasonic waves as a heating source for stretch-molding the neck portion P2, and the source of the ultrasonic waves of the brackets is the stretched body itself.
2 can be heated extremely efficiently and effectively, and the frictional resistance between the neck P2 and the elongated body E can be made extremely small, thus maintaining extremely high dimensional accuracy. It has many excellent effects such as being able to be stretch-molded.

[Brief explanation of the drawing]

FIG. 1 is a partial vertical sectional view showing the positional relationship of the stretched body to the piece before the stretching operation. FIG. 2 is a partial vertical sectional view showing the positional relationship between the piece and the stretched body upon completion of stretch forming. Explanation of symbols P: Piece, P,: Body, P2: Neck, E: Stretched body, E,: Tapered surface, E2: Constant diameter portion, E3: Stepped portion. Lottery ′ Figure 2

Claims (1)

[Claims] 1. A method for stretch-molding the neck of a piece P that is injection-molded into a cylindrical shape with a bottom as a primary molded product of a polyethylene terephthalate resin bottle to be stretch-blow-molded, in which the neck P_2 of the piece P that is injection-molded is A point whose outer diameter gradually decreases at the tip of the cylindrical constant diameter portion E_2, which has a height not smaller than the height of the neck portion P_2 and has an outer diameter that matches the desired amount of extension of the neck portion P_2. An elongated body E, which is integrally formed with a tapered surface portion E_1 having a shape and also serves as a horn that generates ultrasonic waves, is inserted from the tapered surface portion E_1 while emitting ultrasonic waves, and the neck portion P_2 is moved in the radial direction. A method for stretch-molding the neck of a piece for forming a stretch-molded bottle.