JPH0469865B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a mold for forming the neck of a synthetic resin bottle, which is used when manufacturing synthetic resin bottles by injection blow molding, injection stretch blow molding, or the like.

[Conventional technology]

Generally, in synthetic resin bottles filled with carbonated beverages, when the cap is opened, the contents may boil up and squirt out due to internal pressure. Particularly when the temperature is high or when the package is opened immediately after being transported, this phenomenon occurs violently and there is a risk of staining hands or clothes.

This kind of gushing phenomenon will not occur if the high-pressure gas inside the bottle is gradually exhausted, so it is best to let it escape naturally during the process of opening the cap. Due to its high precision, even if the cap is loosened, air will not escape from the screw gap.

Therefore, for example, as shown in FIG.
The gas is discharged from this groove 15 when the cap is loosened.

For example, as a mold for forming the neck of a synthetic resin bottle that makes it possible to process such a groove 15,
The one disclosed in Publication No.-7074 is known.

FIG. 7 shows a mold for forming the neck of a synthetic resin bottle disclosed in this publication, and in the figure, reference numeral 1
Reference numerals 7 and 19 indicate a pair of split molds in which a spiral groove 21 is formed on the inner peripheral molding surface.

The split mold 17 has an elongated through hole 23 on the side surface.
is bored vertically through the spiral groove 21 , and a template 25 is inserted into the through hole 23 such that its front end surface is located at the inner diameter position of the spiral groove 21 .

Such a mold for forming the neck of a synthetic resin bottle is fitted into a recess 29 formed on the upper end surface of the injection mold 27, and a guide member 31 is inserted into the inner peripheral surface of the split molds 17, 19. used in the state.

In such a conventional synthetic resin bottle neck mold, the step 33 of the guide member 31 restricts the upper end surface of the bottle 11 to be molded. up and down,
A stepped portion 33 formed on the guide member 31 is positioned by abutting against a stepped portion 35 formed on the split molds 17 and 19.

In addition, in such a synthetic resin bottle neck mold, the step 33 of the guide member 31 restricts the upper end surface of the bottle 11 to be molded, so in order to improve gas discharge efficiency, it is necessary to It is necessary to make the distance H between the step portion 35 formed in the molds 17, 19 and the upper end of the elongated through hole 23 as short as possible, and conventionally, this distance H has been set to, for example, 1 mm or less. There is.

[Problem that the invention seeks to solve]

However, in such a synthetic resin bottle neck mold, the step 33 formed on the guide member 31 is different from the step 3 formed on the split molds 17 and 19.
5, a crack occurs in the thin part between the step 35 of the split mold 17 and the upper end of the elongated through hole 23, causing the split molds 17, 19 to crack.
There is a problem that the service life of the product decreases and the quality of the product decreases.

In addition, in the conventional synthetic resin bottle neck forming mold, the template 25 is fixed to the through hole 23 of the split mold 17 by adhesive or welding, but in this case, the position of the template 25 changes. There is a possibility that

Furthermore, in the conventional mold for forming the neck of a synthetic resin bottle, it is necessary to form the through hole 23 after forming the spiral groove 21 on the inner peripheral surface of the split molds 17 and 19 by grinding. There was a problem in that burrs were generated in the spiral groove 21 when the groove 23 was drilled, and the number of processing steps was increased to remove the burrs.

[Purpose of the invention]

The present invention was made in order to solve the above problems, and provides a neck molding tool for synthetic resin bottles that can reduce the occurrence of cracks in the split mold and reduce the number of processing steps. The purpose is to provide a type.

[Means for solving problems]

The mold for forming the neck of a synthetic resin bottle according to the present invention includes a pair of split molds in which a spiral groove is formed on the inner circumference molding surface. A protrusion is formed on the ridge.

[Action of the invention]

In the present invention, a protrusion is formed in the spiral groove of a pair of split molds in which a spiral groove is formed on the inner peripheral molding surface, and the protrusion is formed integrally with the split mold by longitudinally cutting the helical groove. A groove for discharging gas is formed in the threaded part of the molded synthetic resin bottle.

[Embodiments of the invention]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, details of the present invention will be described with reference to an embodiment shown in the drawings.

Figures 1 and 2 show an embodiment of the mold for forming the neck of a synthetic resin bottle according to the present invention, and in these figures, reference numerals 37 and 39 indicate a pair of split molds. .

Inner peripheral molding surface 41 of these split molds 37, 39
A spiral groove 43 is formed therein.

Therefore, in this embodiment, the split molds 37, 3
Projections 45, 46, 47, and 48 are formed integrally with the split molds 37 and 39, extending vertically through the spiral groove 43 of No.9.

These protrusions 45, 46, 47, 48 are formed in two pieces on each of the pair of split molds 37, 39, and the protrusions 45, 46 formed on one of the split molds 37 The protrusions 47 and 48 formed on the other split mold 39 are formed to face each other in order to facilitate separation of the product (bottle) from the mold.

That is, the protrusions 45 and 48 are formed to face each other on an axis 53 perpendicular to the dividing surface 51, and the protrusions 46 and 47 are formed on an axis 55 perpendicular to the dividing surface 51. They are formed facing each other.

In addition, these protrusions 45, 46, 47, 48
is formed to protrude somewhat inward from the inner diameter of the spiral groove 43.

FIG. 3 shows a spiral groove 43 and protrusions 45, 46 on the inner molding surface 41 of a pair of split molds 37, 39.
47 and 48 are shown formed by electrical discharge machining. In the figure, reference numeral 57 indicates an electrode whose upper end is fixed to the head of an electrical discharge machine (not shown).

The lower end of this electrode 57 has split molds 37 and 3.
A cylindrical discharge portion 5 having a smaller diameter than the inner peripheral molding surface 41 of 9.
A spiral protrusion 61 having a shape corresponding to the spiral groove 43 is formed in the discharge portion 59, and the protrusion portions 45, 46, 4 shown in FIG.
Recessed portions 63 are formed at positions corresponding to 7 and 48.

Further, the pair of split molds 37 and 39 are placed on a table 65, and this table 65 is
It is movable in a direction perpendicular to the dividing surface 51 of the pair of divided molds 37 and 39.

In this embodiment, the concave portion 63 is located in the discharge portion 59 of the electrode 57 at a position corresponding to the protruding portions 45, 46, 47, and 48 shown in FIG. , 39 are formed opposite to each other on axes 53, 55 perpendicular to the dividing surfaces 51 of the pair of divided molds 37, 39, while a table 65 moves in a direction perpendicular to the dividing surfaces 51 of the pair of divided molds 37, 39. Since this is possible, by moving the table 65 in the direction of arrow A in the figure during electrical discharge machining, the spiral groove 43 and the protrusions 45, 4 can be formed in the split molds 37, 39.
6, 47, and 48 can be easily processed with high precision.

FIG. 4 shows a state in which a synthetic resin bottle 67 is manufactured using the split molds 37 and 39 subjected to electric discharge machining in this way, and in the figure, reference numeral 3
7 and 39 indicate a pair of split molds in which a spiral groove 43 and protrusions 45, 46, 47, and 48 are formed on an inner peripheral molding surface 41.

The split molds 37 and 39 are fitted into a recess 71 formed on the upper end surface of the injection mold 69, and a guide member 75 guided by a sliding guide member 73 is inserted into the inner peripheral molding surface 41. It is used in the same condition.

In this embodiment, a stepped portion 77 is formed on the guide member 75, and the guide member 75 is positioned by bringing this stepped portion 77 into contact with the upper end surface 79 of the split molds 37, 39. .

Therefore, in the synthetic resin bottle neck forming mold configured as described above, the spiral groove 43 of the pair of split molds 37 and 39 in which the spiral groove 43 is formed on the inner circumferential molding surface 41 is Protrusions 45, 46, 47, 4 are formed longitudinally through the groove 43 and integrated with the split molds 37, 39.
8, the protrusions 45, 46, 4
7 and 48, a groove 83 for discharging gas is formed in the threaded portion 81 of the molded synthetic resin bottle 67, as shown in FIG.

Therefore, it is no longer necessary to drill an elongated through hole 23 in the side surface of the split mold 17 for inserting the template 25, unlike the conventional synthetic resin bottle neck mold. Therefore, it is possible to reliably eliminate the occurrence of cracks near the through hole 23.

In addition, in the synthetic resin bottle neck forming mold configured as described above, the spiral groove 43 and the protrusions 45, 46, 47, 48 are formed in the split molds 37, 39 by electrical discharge machining. This makes it extremely easy to process, and the number of processing steps can be significantly reduced compared to conventional methods.

Furthermore, in the synthetic resin bottle neck forming mold configured as described above, the protrusions 45, 46, 47,
48 are respectively formed in a pair of split molds 37 and 39, and the protrusion 4 formed in one of the split molds 37 is
5 and 46 and the protrusions 47 and 48 formed on the other split mold 39 are formed to face each other, so that the table 65 can be moved during electrical discharge machining of the split molds 37 and 39. , electrical discharge machining can be made very easy.

In the embodiment described above, the protrusions 45, 46, 47, 4 are provided on both of the pair of split molds 37, 39.
8 has been described, but the present invention is not limited to such an example, and for example,
Of course, the protrusion may be formed only on one of the split molds.

〔Effect of the invention〕

As described above, in the present invention, the spiral grooves of the pair of split molds in which the spiral grooves are formed on the inner peripheral molding surface,
Since the protrusion is formed integrally with the split mold by extending vertically through the spiral groove, there are advantages in that the occurrence of cracks in the split mold can be reduced and the number of processing steps can be reduced.

[Brief explanation of the drawing]

Fig. 1 shows an embodiment of the mold for forming the neck of a synthetic resin bottle according to the present invention, and is a side view of a pair of split molds seen from the split surface side, and Fig. 2 is a cross-sectional view of the split mold of Fig. 1. A top view, Figure 3 is an explanatory diagram showing the state in which the split mold shown in Figure 1 is being subjected to electrical discharge machining, and Figure 4 is a resin molding of a bottle using the split mold shown in Figure 1. Fig. 5 is a side view showing a bottle molded by resin molding as shown in Fig. 4, Fig. 6 is a side view showing a conventional synthetic resin bottle, and Fig. 7 is a side view showing a conventional synthetic resin bottle. FIG. 2 is a longitudinal cross-sectional view showing a neck molding die for a resin bottle. 37, 39...Divided mold, 41...Inner peripheral molding surface, 43...Spiral groove, 45, 46, 47, 48...
...projection.

Claims (1)

[Scope of Claims] 1. A protrusion is formed in the spiral grooves of a pair of split molds in which a spiral groove is formed on the inner peripheral molding surface, extending longitudinally through the spiral grooves and integrally with the split molds. A synthetic resin bottle neck mold featuring: 2. The protrusions are formed on each of a pair of split molds, and the protrusions formed on one split mold are opposed to the protrusions formed on the other split mold. A mold for forming the neck of a synthetic resin bottle according to claim 1. 3. The mold for forming the neck of a synthetic resin bottle according to claim 1 or 2, wherein the spiral groove and the protrusion are formed by electrical discharge machining.