JPS6215329B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for forming a biaxially stretch-molded bottle made of polyethylene terephthalate resin, and its purpose is to easily and reliably stretch-mold a neck that cannot or cannot be easily stretch-molded. It is something to do.

Another purpose is to prevent the neck from being compressively deformed during stretch molding.

Another object of the present invention is to form a screw on the outer circumferential surface of the neck at the same time as the stretch-forming of the neck.

Polyethylene terephthalate resin has come to be used in many fields due to its excellent physical properties and durability. This is achieved only by biaxial stretching.

For this reason, in the case of a bottle structure, the molding method is almost exclusively limited to injection blow molding.

The order of molding a bottle made of polyethylene terephthalate resin is that the primary molded piece, which is a cylindrical piece with a bottom, is injected and extrusion molded, and the neck of this piece is held in a blow mold. The bottle is then blow-molded by stretching it in the axial direction with a stretching pin and pressurizing fluid into the piece, but as is clear from this molding sequence, the neck of the bottle is not stretched at all. .

For this reason, the neck of the bottle has inferior physical properties and durability compared to other parts. For example, if a high concentration of alcohol is placed inside the molded bottle, the neck will be subjected to biaxial stretching due to the alcohol. A phenomenon occurs in which only the untreated neck area becomes white and mechanically brittle.

As mentioned above, the present invention was devised to solve the serious disadvantages of polyethylene terephthalate resin bottles, and only the neck portion is stretch-molded prior to biaxially stretching the bottle. Embodiments of the invention will be described with reference to the drawings.

Figures 1 to 3 show the basics of the method of the present invention. Figure 1 shows the state of the neck P2 before stretching and forming, Figure 2 shows the state of the neck P2 after stretching and forming, and FIG. 3 shows a state in which the piece P whose neck portion P2 has been stretch-molded is stretch-blow-molded into a bottle body.

As can be seen from FIGS. 1 to 3, the present invention provides that, prior to stretch blow molding of the body P1 of the piece P, the tip E1 is formed into a pointed shape with a gently sloped surface in the neck P2. The stretched rod E is inserted into the constant outer diameter portion E2 to stretch the neck P2 in the radial direction, and then the stretched neck P2 is used to immovably hold the piece P in the blow mold and the stretched pin F is inserted. While stretching the piece P, pressurized fluid is injected into the piece P to form it into a bottle.

In this way, the neck portion P2 is stretched in such a manner that it is pushed and expanded in the radial direction by the entry of the stretching rod E, so naturally the outer diameter of the constant outer diameter portion E2 following the tip portion E1 of the stretching rod E is as follows. Needless to say, it is set to a value larger than the diameter of the neck P2 and according to the desired amount of stretching.

Furthermore, the neck P2 that undergoes stretching needs to be formed thicker according to the amount of stretching, and therefore the neck P2 of the piece P to which the present invention is applied is thicker than the neck of a conventional piece. is getting bigger.

Furthermore, the neck portion P2 is stretched when the stretching rod E enters into the interior, and when the stretching rod E enters the neck portion P2, there is a gap between the neck portion P2 and the surface of the stretching rod E. Since it is desirable that there be as little frictional resistance as possible, the surface of the stretching rod E should be as smooth as possible and should have less frictional resistance, and the inclination angle of the circumferential surface of the tip E1 should be as gentle as possible. is desirable.

In this case, in addition to the above-mentioned measures, measures such as applying an appropriate lubricant to the surface of the drawing rod E or locally cooling and solidifying only the inner surface of the neck portion P2 to make it easier to slide on the drawing rod E may be taken. There is no problem in using both.

During the stretch-molding operation of the neck portion P2 using the stretch rod E, the piece P must not be displaced in the advancing direction of the stretch rod E due to intrusion into the neck portion P2 of the stretch rod E, so the piece P must be The piece P must be held in such a way that the piece P is held in such a way that the piece P is held in such a way that it is wrapped in as wide a range as possible from the bottom of the piece P to the trunk P1, by the stretching action of the neck P2 by the stretching rod E. This is desirable in terms of preventing deformation of P1.

By the way, as mentioned above, the frictional resistance between the neck P2 and the stretching rod E can be made sufficiently small by various means.
It is impossible to completely eliminate the frictional resistance between the neck P2 and the stretching rod E, and therefore, when the neck P2 is stretched by the stretching rod E, there is a risk that the neck P2 will be compressed and deformed even slightly.

Therefore, if it is necessary to completely prevent compression deformation in the neck P2, as shown in FIGS. 4 and 5, the outer circumferential surface of the neck P2 should be It is preferable to provide a holding piece H that locks and holds the mouth edge P4 provided around the upper end from below.

In this case, the holding piece H that locks and holds the mouth edge P4 from below needs to be displaced in the radial direction in synchronization with the displacement of the neck P2 once the neck P2 is stretched in the radial direction and begins to be displaced. However, as a means of displacing the holding piece H in synchronization with the neck P2, for example, it may be pushed back by the pressing force from the neck P2 acting on the holding piece H. If this is done, the frictional resistance between the neck portion P2 and the stretching rod E will increase, so it cannot be said to be a very good means.

Therefore, desirably, since the aperture of the neck P2 is known, the lowering position of the stretching rod E at which the stretching operation of the neck P2 starts can also be determined, and the starting point is the point at which the stretching operation of the neck P2 starts. A member is provided that moves downward integrally with the extension rod E, and this member is provided with a portion having an inclination angle that matches the inclination angle of the inclined surface of the tip portion E1, and this inclination angle portion allows the holding piece to be moved in accordance with the cam operation. It is better to move H backwards.

In this manner, during the stretch-forming operation of the neck portion P2 by the stretch rod E, the neck portion P2 is not displaced integrally with the stretch rod E, so that in the case of the embodiment shown in FIGS. 4 and 5, accurate dimensions can be maintained. Stretch molding of the neck P2 can be achieved.

Further, at the same time as the neck portion P2 is stretched and formed by the stretching rod E, a screw P5 is formed by pressure molding on the outer peripheral surface of the neck portion P2.
can be molded.

That is, as shown in FIG. 6, the neck part P2 to be stretch-molded is arranged in a ring-shaped molding die N in which a thread molding surface N1, which is the inner circumferential surface, is formed with a screw type, and then stretched by a stretching rod E. Stretch-molded neck P2
However, the dimensions such as the wall thickness of the mold N and the neck P2 are set so that the neck P2 is pressed against the screw molding surface N1 of the mold N just before the completion of the stretch molding, and the amount of stretching of the neck P2 is set.

In this way, the inner diameter dimension of the thread molding surface N1 of the molding die N, the wall thickness dimension of the neck portion P2, the wall thickness dimension of the neck portion P2, and the extension amount of the neck portion P2, that is, the outer diameter dimension of the constant outer diameter portion E2 are set. By doing so, the screw P5 is formed on the outer circumferential surface of the neck portion P2 at the same time as the stretching and forming of the neck portion P2 is completed.

The screw P5 formed in this way has a neck portion P
Since it is molded immediately before the stretch molding in step 2, the dimensional accuracy of the screw is high.

Another means of attaching a screw to the stretch-molded neck P2 is to attach a screw P5' to the outer peripheral surface of the neck P2 when the piece P is injection molded, as shown in FIGS. 8 and 9. There is a way to shape it.

In this case, unlike the embodiments shown in FIGS. 6 and 7, there is no need for the molding die N, and it is sufficient to simply stretch the neck portion P2 with the stretching rod E.

However, as mentioned above, during the stretching operation using the stretching rod E, there is a risk that the neck portion P2 will be compressively deformed, albeit slightly.
It is not necessarily the case that stretch molding is carried out with the exact dimensional relationship as when it was injection molded.

For this reason, in the case of the embodiments shown in FIGS. 8 and 9, it is desirable to use the means shown in FIGS. 4 and 5 simultaneously.

By the way, as the stretching rod E for stretch-forming the neck portion P2, as shown in the embodiments shown in FIGS. 1 to 9, the tapered surface of the tip portion E1 is formed by a single inclined surface. However, for example, when the amount of stretching is relatively large, it is preferable to form the inclined surface of the tip end E1 into a stepped shape with two or three steps at the same inclination angle, as shown in FIG.

By forming the tapered surface of the tip end E1 of the drawing rod E in multiple stages in this way, the stretching operation of the neck portion P2 itself can be achieved relatively smoothly, and the drawing rod can be easily stretched compared to the case where the tapered surface is a single inclined surface. Frictional resistance is reduced between E and neck P2.

In addition, in the illustrated embodiment, the piece P is shown as having the inner diameter of the body part P1 larger than the inner diameter of the neck part P2, but this is not limited to the shape of this piece P, and can be any general shape. It goes without saying that the inner diameter of the neck portion P2 and the inner diameter of the body portion P1 may have the same structure.

As is clear from the above description, the present invention allows a bottle made of polyethylene terephthalate resin to be molded with its neck portion stretch-molded, so that only the neck portion of the bottle is inferior to the body portion in terms of properties and durability. This is an extremely excellent method for forming biaxially stretched bottles made of polyethylene terephthalate resin, as the entire body can be made to have excellent, uniform properties and durability, and the operation is simple and easy to carry out. .

[Brief explanation of the drawing]

Figures 1 to 3 are longitudinal sectional views showing the most basic form of the method of the present invention, with Figure 1 showing the mutual positional relationship before stretch forming, and Figure 2 showing the state of the neck after stretch forming. , FIG. 3 shows the state in which the piece with the neck portion stretch-molded is stretch-blow-molded. 4 and 5 show one means for preventing compressive deformation of the neck portion during stretch forming, with FIG. 4 being a longitudinal sectional view and FIG. 5 being a plan view.
FIGS. 6 and 7 show the case where a screw is formed on the outer peripheral surface of the neck at the same time as the neck is stretch-molded.
Figure 6 is a longitudinal cross-sectional view showing the state before stretch forming, Figure 7
The figure is a longitudinal sectional view showing the completion of stretch forming and screw forming. Figures 8 and 9 show the case in which a screw is formed on the outer circumferential surface of the neck part during piece molding.
The figure is a longitudinal cross-sectional view at the time of completion of stretch forming. FIG. 10 is a front view of main parts showing another embodiment of the stretching rod. Explanation of symbols, P; Piece, P1; Body, P2;
Neck, P3; Shoulder, P4; Edge of mouth, P5/P
5′; screw, E; stretching rod, E1; tip, E2;
Fixed outer diameter portion, F: Stretch pin, H: Holding piece, N: Molding die, N1: Thread molding surface.

Claims (1)

[Claims] 1. A piece P, which is a primary molded product molded by injection molding from polyethylene terephthalate resin, has a neck P2 formed with a large thickness, and a tip E1 is formed into a point with a gently sloped surface. A stretching rod E shaped like a straight rod with a predetermined diameter is inserted into the constant outer diameter portion E2 to stretch the neck portion P2 in the radial direction, and then the stretched neck portion P2 is held immovably to form the piece P. A method of forming a biaxially stretch-molded bottle made of polyethylene terephthalate resin by biaxially stretch-blow molding the bottle. 2. Insert the holding piece H from below the mouth edge P4, which is protrudingly provided on the upper end of the outer peripheral surface of the neck P2, which is formed with a large wall thickness, of the piece P, which is a primary molded product made by injection molding of polyethylene terephthalate resin. A straight rod-like extension rod E having a predetermined diameter and a pointed end portion E1 with a gently sloped surface is inserted into the neck portion P2 up to the constant outer diameter portion E2, and the neck portion P2 is moved in the radial direction. At the same time, in synchronization with the movement of the stretching rod E into the neck P2, the holding piece H is moved backward in the radial direction while keeping it locked with the mouth edge P4, and then Holding the stretched neck P2 immovably, the piece P
A method of forming a biaxially stretch-molded bottle made of polyethylene terephthalate resin by biaxially stretch-blow molding the bottle. 3. The neck P2, which is a large-thickness molded piece P which is a primary molded product molded by injection molding with polyethylene terephthalate resin, is formed into a mold N1 with the mold surface, which is the inner peripheral surface, as the screw molding surface N1. arranged coaxially within the neck portion P2;
A straight rod-shaped stretching rod E having a predetermined diameter and a pointed end portion E1 having a gently sloped surface is inserted into the constant outer diameter portion E2 to stretch the neck portion P2 in the radial direction, and at the same time, the thread forming surface is A biaxially stretch-molded bottle made of polyethylene terephthalate resin, in which a screw P5 is press-molded by pressing N1, and then the piece P is biaxially stretch-blow-molded into the bottle while holding the stretch-molded neck P2 immovably. Molding method. 4. A method for molding a biaxially stretched polyethylene terephthalate resin bottle as set forth in claims 1 and 2, wherein a screw P6 is previously molded on the outer peripheral surface of the neck portion P2. 5 Claim 1, in which the circumferential surface of the tip end E1 of the stretching rod E is shaped like a step, inclined at approximately the same angle.
A method for forming a biaxially stretched bottle made of polyethylene terephthalate resin shown in 2 and 3.