JPS5953849B2 - Piece edge stretch forming method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for stretching and molding the mouth edge of a piece as a primary molded product formed by injection molding into a biaxially stretched polyethylene terephthalate resin. The object is to exhibit the excellent physical properties and durability of polyethylene phthalate resin by stretch-molding the polyethylene phthalate resin.

Polyethylene terephthalate resin has excellent physical properties and durability, but the excellent physical properties and durability of polyethylene terephthalate resin can only be fully demonstrated when it is stretch-molded. It is what it is.

For this reason, when molding a polyethylene terephthalate resin into a cylindrical piece with a bottom, it is first formed by injection molding, and then this piece is assembled into a blow mold and then stretch-blow molded. I is generally molded by so-called injection blow molding, in which the molded material is molded into an increased thickness.

When blow-molding this bulge, the piece is generally assembled into the blow mold at its neck, so while the body of the burlap is fully stretch-molded, the neck of the bulwark is completely stretched. It was not subjected to stretching, and therefore, even with a single increase in thickness, the material properties of the neck were significantly inferior to those of the body.

For example, conventional polyethylene terephthalate resin 2
Axial stretch molded bottles have the serious disadvantage that the neck part becomes white due to penetration of alcohol and becomes mechanically brittle, and in the case of bottles with screw caps, pressure contact with the screw caps may occur. The rim of the bottle, which is supposed to be sealed, tends to deform, the sealing performance deteriorates, and many thin cracks occur, resulting in poor seal retention. In addition, in order to solve this problem with the neck, it has been considered to stretch-form the neck, but there are many unresolved problems, especially the difficulty of maintaining accurate dimensional accuracy after stretch-molding. There was a problem.

Particularly in cases where a thread is formed on the outer circumferential surface of the neck, it is considered extremely difficult to stretch-form the thread with the same precision as injection molding.

The present invention was devised to eliminate the drawbacks of the above conventional examples, and by forcibly stretching the mouth edge of the piece in the radial direction, the mouth edge has the excellent properties of polyethylene terephthalate resin. It is designed to have good physical properties and durability.

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

In the present invention, in the neck P1 of the piece P, there is provided a drawing rod E whose tip end E1 has a pointed shape with a gently sloped surface, and an island with a constant outer diameter continuing from the tip E1 of the drawing rod E. By forcefully inserting the neck portion P1 into the position until it faces the mouth edge P2, which is the tip of the neck portion P1, the mouth edge P2 is inserted into the constant outer diameter portion E of the stretching rod E.
It extends in the radial direction to a value set by the outer diameter value of No. 2.

In this way, the present invention can insert the stretching rod E into the mouth edge P2.
Since it is stretch-molded in the radial direction, the diameter of the mouth edge P2 before stretch-forming is the constant outer diameter of the stretch rod E! It goes without saying that the value must be smaller than the outer diameter of the material by a value corresponding to the desired amount of stretching. Also, the stretching rod E
When forming the mouth edge P2 by stretching, a pushing force is applied from the stretching rod E to the piece P. However, in order to prevent the piece P from being displaced by the movement of the stretching rod E, the piece P is
must be held immovable.

Various methods are conceivable for holding this piece P, but in order to prevent the neck P1 from changing due to the stretching force of the stretching rod E acting on the neck P1 adjacent to the lip P2, It is preferable that P1 be held by the holding fitting H over its entire circumference.

Since this holding fitting H is to hold the neck P1 uniformly over the entire circumference, it must have a ring structure, that is, a structure having a hole into which the neck P1 is snugly fitted. In addition, when a screw is formed on the outer circumferential surface of the neck P1 as in the illustrated embodiment, the retaining metal H is arranged so that a gap is not formed between the surface of the neck P1 and the holding metal H due to the screw. It is good to form a screw structure on the neck holding surface of the neck.

Since the neck portion P1 is held by the holding metal fitting H, the mouth edge portion P2 will protrude above this holding metal fitting H. Therefore, in order to stretch-form the mouth edge portion P2, the stretching effect is not applied. When heating to the temperature where it comes out, this heating causes the mouth edge P to
The neck portion adjacent to P2 is not heated to a large extent and therefore is less likely to be deformed during stretch forming of the mouth edge P2.

As described above, the method of the present invention heats the mouth edge P2 protruding from the holding fitting H that holds the neck P1 to a temperature that produces a stretching effect, and then inserts the stretching rod E into the piece P to form a portion with a constant outer diameter. The opening edge P2 is inserted until E2 is positioned opposite the opening edge P2, and the opening edge P2 is stretched in the radial direction using the stretching rod E.

By the way, by forcibly inserting the stretching rod E into the neck portion P1 as described above, it is possible to stretch-form the mouth edge portion P2 in the radial direction. If the mouth edge P2 is stretched in the radial direction, the shape of the stretched mouth edge P2 is not necessarily constant, and may be deformed in some cases.

For this reason, as in the illustrated embodiment, the molding die K mounted on the holding metal fitting H is positioned opposite to the mouth edge P2, and the constant outer diameter portion of the stretching rod E is placed opposite to the mouth edge P2. Form a stepped tile on top, and this step! The shape of the mouth edge P2 that is stretch-molded by the mold surface K2 of the mold K is regulated.

That is, the mouth edge P2 is stretched in the radial direction by stretch forming using the stretching rod E, and upon completion of this stretch forming, the mouth edge P2 is stretched by the mold surface K2 of the molding die K. The deformation in the radial direction and the upward deformation are restricted by the stepped portion E3, and the shape is determined by the molding die K and the stepped portion E3.

In other words, the mouth edge P2 is connected to the molding die K and the step E3.
forced into the type space formed by and . They will be forced into it.

Therefore, the stretch-molded trailing edge portion P2 is formed into the shape set by the molding die K and the stepped portion E3, and the shape does not vary at all due to the stretch-molding.

In addition, when the piece P has a screw formed on the outer circumferential surface of the neck portion P1 as in the illustrated embodiment, simply stretching the mouth edge portion P2 outward will cause the stretch-molded mouth The edge P2 protrudes outward from the outer peripheral surface of the neck P1, making it impossible to screw the screw cap onto the neck P1. therefore,
If a screw is formed on the outer peripheral surface of the neck P1, the neck P1
1, the upper end of the outer periphery, ie, the outer periphery of the mouth edge P2, is removed by the amount of stretching to form a stepped portion P3.

In this way, since the outer peripheral surface of the mouth edge P2 is located inward from the outer peripheral surface of the neck portion P1 by an amount commensurate with the amount of stretching, when the mouth edge P2 is stretch-molded, The outer circumferential surface of the stretch-molded mouth edge portion P2 can be arranged so as not to be located further outward than the outer circumferential surface of the neck portion P1.

At this time, a regulating protrusion K1 having a circumferential protruding structure is provided at the lower end portion of the molding die K facing the mouth edge P2, as in the illustrated embodiment.
By providing this, the mouth edge P2 can be reliably stretched in the radial direction.

However, in this case, it is necessary for the molding die K to have a split die structure in view of the mold release operation. In the above explanation,
Although stretch molding has been described for the mouth rim P2 of the piece P, it is not necessarily limited to the mouth rim P2 of the piece P, and may be performed on the mouth rim P2 of a bottle that has already been stretch-molded. It's good.

As described above, in the present invention, since the mouth edge P2 forming the bottle opening can be stretch-molded, the mouth edge P2 can be made to have the excellent physical properties and durability of polyethylene terephthalate resin as well as the body of the bottle. This makes it possible to prevent problems such as deterioration of the sealing effect and deterioration of mechanical strength in the polyethylene terephthalate resin bottle.

In particular, when a screw is formed on the outer circumferential surface of the neck P1, the mouth edge P1 can be removed without deforming the entire neck P1.
2 can be stretch-molded, and the shape of the stretch-molded mouth edge P2 can be precisely regulated, and it can be made so as not to cause any hindrance to the screwing operation of the screw cap that is screwed onto the neck portion P1. .

As is clear from the above description, the present invention can improve the physical properties and durability of the mouth edge of a biaxially stretched polyethylene terephthalate resin bottle to the same level as the body, and the molding operation is simple and easy to implement. It is easy, and the molding operation can be performed at any time, whether it is at the time of the piece or when it is molded into the bottle, so it can be performed on a bottle that has already been formed. It has many excellent effects, such as being able to be used in a variety of situations.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view of a main part showing the structure of a neck of a polyethylene terephthalate resin bottle or piece, which is shaped to be convenient for carrying out the method of the present invention. FIG. 2 is a vertical cross-sectional view of essential parts showing the positional relationship among the piece or bottle, the holding fitting, the molding die, and the stretching rod before the mouth edge is stretch-molded. FIG. 3 is a longitudinal cross-sectional view of the main part upon completion of stretch forming of the mouth edge. FIG. 4 is a longitudinal cross-sectional view of the main part showing the stretched mouth edge. Explanation of symbols, P: piece, P1: neck, P2: rim of mouth,
P3: Stepped portion, H: Holding metal fitting, K: Molding die, K1: Regulating protrusion, K2: Molding die surface, E: Stretching rod, E1: Tip, E
2: Constant outer diameter part.

Claims (1)

[Scope of Claims] 1. In a piece P as a primary injection molded product made of a biaxially stretched polyethylene terephthalate resin bottle, the neck P_1 of the piece P is held around the entire circumference by a supporting metal fitting H, and Mouth edge part P_2 which is the upper end part of neck part P_2 located upwardly protruding from the holding metal fitting H
is heated to a temperature that produces a stretching effect, and then a stretching rod E whose tip end E_1 has a pointed shape with a gently sloped surface is placed in the neck P_1, and a fixed portion following the tip end E_1 of the stretching rod E is placed inside the neck P_1. A method for stretch-molding a mouth edge of a piece by inserting the piece until the outer diameter portion E_2 is positioned opposite to the mouth edge P_2. 2 In the piece P as a primary molded product formed by injection molding into a biaxially stretched polyethylene terephthalate resin bottle, the neck P_1 of the piece P, which has a thread formed on its outer peripheral surface, is held by a holding metal fitting H over the entire circumference. At the same time, a neck portion P_ projecting upward from the holding fitting H
The mouth edge P_2, which is the upper end of the neck part P_1 and is connected to the neck part P_3 via the stepped part P_3, is heated to a temperature that produces a stretching effect so that the outer peripheral surface is located inward by the amount of stretching than the outer peripheral surface of the neck part P_1. , After that, on the holding fitting H, the inside diameter of the mold surface K_2 is approximately equal to the extent that it does not become larger than the diameter of the neck part P_1, and the lower end of the mold surface K_2 is molded into a circumferential protruding strip shape, and is located on the stepped part P_3. Molding die K with regulating protrusion K_1
Then, in the neck P_1, a step part E is placed on the constant outer diameter part E_2, the tip part E_1 of which has a pointed shape with a gently sloped surface, and the same height as the mouth edge part P_2.
A stretching rod E that is tightly fitted into the mold surface K_2 of the molding die K via the
A method for stretch-molding a mouth edge of a piece, in which a constant outer diameter portion E_2 following _1 is positioned opposite to the mouth edge P_2 and inserted until the stepped portion E_3 is positioned on the upper end surface of the mouth edge P_2.