JPS6142815Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a mold for injection molding an intermediate material for biaxially stretched bottles.

In order to increase the mechanical strength of the bottle, a cylindrical intermediate material with a bottom and an open top is injection molded in advance.
The intermediate material is placed in a blow mold and stretched biaxially to form a bottle. Since the bottle wall becomes extremely thin due to the biaxial stretching, it is particularly important to make the wall thickness uniform when forming the intermediate material.

The proposed method is capable of forming an intermediate material with uniform wall thickness, a high packing effect, and a biaxially stretched bottle that does not cause injury to fingers at the outer periphery of the top surface of the bottle mouth. It was established.

To explain the drawings below, 1 and 1 are molds with cavity recesses 2 and 2, and these molds form a pair of left and right, and the cavity recesses 2 and 2 are placed opposite each other so that they can be opened and closed left and right. There is. The cavity recess is a cylindrical intermediate material 7 for forming biaxially stretched bottles with a closed bottom end and an open top end as shown in FIG.
A gate 3 is opened at the center of the bottom of the cavity. Recesses 4, 4 for holding the core mold are formed on the inner surface of the upper end of the mold with the cavity recess, and the cavity recess is formed continuously below the holding recess.

A core mold 5 is vertically disposed within the cavity recess, with its upper portion being held by the holding recesses 4, 4. The core mold has an upper part 5a held by the holding recess as a large outer diameter part, and a core part 5c vertically disposed within the cavity recess as a small outer diameter part.
A first downward step portion 5b is provided on the boundary line between them. A cavity 6 is formed between the outer surface of the core portion and the surface where the cavity recess described above is formed, and by injecting the molten synthetic resin material into the cavity from the gate 3 described above, a biaxially stretched bottle is formed. A cylindrical intermediate material 7 for molding is formed.

The first downward step portion 5b forms the inner circumference 8 of the top surface of the intermediate material mouth, and the outer circumference 1 of the top surface of the mouth
0 is formed by the second downward step 2b formed in the cavity molds 1, 1. The second downward stepped portion is formed slightly lower than the first downward stepped portion 5b, and in order to be formed in this way, the upper end portions 2a, 2a of the cavity recess are formed slightly lower than the first downward stepped portion 5b.
are continuously formed below the holding recesses 4, 4, and the upper end portions 2a, 2a of the cavity recesses 2a, 2a.
and second downward step portions 2b, 2 on the boundary line with the upper portions 2c, 2c of the cavity recess continuing below the upper end.
b was formed. Upper part 2 of the cavity recess
c, 2c have a larger inner diameter than the upper end portions 2a, 2a, and the upper portions 2c, 2c form the outer surface forming wall of the mouth and neck portion of the intermediate material. With the above configuration, the upper end portions 2a, 2a form a step forming wall 9 between the inner peripheral portion and the outer peripheral portion of the mouth top surface.

The intermediate material 7 formed by injection molding into the cavity is heated to a temperature suitable for biaxial stretching, placed in a blow molding mold, and stretched in the longitudinal direction with a push rod. After blowing in compressed air and stretching in the transverse direction to form a biaxially stretched bottle 11 shown in FIG. 4, the mold is opened and the bottle is taken out.

This proposal has the above-mentioned configuration, and the core mold upper part 5
The recessed portion 4, 4 for holding the cavity is formed on the inner surface of the upper end of the mold with the recessed portion for cavity.
Since the core portion 5c, which has a smaller outer diameter than the upper portion, is vertically disposed within the cavity recesses 2, 2, it is easy to reliably hold the core mold so that it will not tilt due to the injection pressure of the molten resin material that has entered the cavity, and therefore an intermediate material with no uneven thickness can be produced, and therefore a biaxially stretched bottle with no uneven thickness can be produced. Also, a first downward step 5b is formed on the boundary line between the core mold upper portion 5a and the core portion 5c, and a second downward step 2b is formed on the boundary line between the upper end 2a of the cavity recess and the upper portion 2c continuing below the upper end, and the first downward steps 5b, 5c are
Since the inner peripheral portion 8 of the intermediate material mouth top surface is formed by the second downward step portions 2b, 2b, and the outer peripheral portion 10 of the intermediate material mouth top surface is formed by the second downward step portions 2b, 2b, the mating surfaces of the mold with the cavity recess and the core mold are not located on the inner and outer peripheral edges of the mouth top surface, so that it is easy to form a radius on the inner and outer peripheral edges of the mouth top surface to prevent the formation of edges, and even if burrs are generated on the mating surfaces of the mold, they are formed on the mouth top surface of the bottle mouth neck, so there is little risk of the burrs injuring fingers. Furthermore, since the upper end portion 2a of the cavity recess is formed continuously below the holding recess 4, and the second downward step portion 2b is formed between the upper end portion and the upper portion below it, the inner peripheral portion 8a of the bottle mouth top surface becomes higher than the outer peripheral portion 10a, and the rib 9
Since a is provided around the periphery, when a cap with packing is screwed onto the neck of the bottle, the packing is not pressed against the entire top surface of the bottle mouth, but only against the inner periphery of the top surface, which reduces the contact area and results in a bottle with a high packing effect.

[Brief explanation of the drawing]

Fig. 1 is a longitudinal sectional view of the proposed mold, Fig. 2 is an enlarged sectional view of its main parts, Fig. 3 is a longitudinal sectional view of the intermediate material formed by the mold, and Fig. 4 is a longitudinal sectional view of the intermediate material formed by the mold. FIG. 3 is a half-sectional view of the biaxially stretched bottle that is formed. 1... Mold with cavity recess, 5... Core mold.

Claims (1)

[Scope of utility model registration request] Molds 1, 1 with a pair of left and right cavity recesses 2, 2 for injection molding a cylindrical intermediate material for biaxially stretched bottle molding with a closed bottom end and an open top end, and upper end portions of both molds. It consists of a core mold 5 whose upper part is held by the holding recesses 4, 4 formed on the inner surface, and is suspended in the cavity recess. A first downward step 5b is formed on the boundary line between the upper part of the core mold held by the core mold and the core part 5c which is a vertically installed part of the core mold and is vertically installed in the cavity recess. In the case of the mold, the upper end portions of the cavity recesses 2, 2 are continuously formed below the above-mentioned holding recesses 4, 4, and the upper end portions 2a, 2a of the cavity recesses and an upper portion continuing below the upper ends are formed. 2c,
2c, and by injection molding into the cavity, the inner peripheral part 8 of the top surface of the intermediate material opening is formed by the first downward step part 5b.
The outer circumferential portion 10 of the top surface of the intermediate material mouth is further extended by the second downward step portion 2b to the upper end portion 2 of the cavity recess.
A mold for injection molding an intermediate material for a biaxially stretched bottle, characterized in that the step-forming wall 9 between the inner peripheral part 8 and the outer peripheral part 10 can be formed respectively.