Nesting blow molding die

Abstract

This invention provides a nesting type blow molding die for blow molding resin containers, consisting of three stages: upper, middle, and lower. The upper and lower stages are used interchangeably, and multiple types of middle stages with different inner surface shapes are provided, enabling the molding of resin containers with different shapes, such as cylindrical, elliptical, and polygonal prisms for the container body. [Solution] A nesting mold used for blow molding of resin containers, wherein the molded resin container comprises an upper part, a body part, and a bottom part, and has an upper connecting surface and a lower connecting surface between the upper part and the body part, and between the body part and the bottom part, respectively, and the nesting mold is composed of an upper mold, a middle mold, and a lower mold, the upper mold and the middle mold are joined at the upper surface of the upper connecting surface, and the middle mold and the lower mold are joined at the upper surface of the lower connecting surface.

Description

Technical Field

[0001] The present invention relates to a nested mold used for blow molding of resin containers.

Background Art

[0002] Conventionally, as a nested mold for a resin container to be blow molded, as shown in FIG. 8, there are three types: an upper mold for molding the upper part of the container, a middle mold for molding the body part of the container, and a lower mold for molding the bottom part of the container. A plurality of types of the middle mold are prepared according to the capacity of the container, etc., and by replacing this middle mold, a mold technology for blow molding a plurality of types of resin containers having different lengths (capacities) is known (see Patent Document 1).

[0003] In the above-described nested mold composed of upper, middle, and lower three stages, it can only be applied to containers having the same or similar cross-sectional shapes in the horizontal directions of the upper part, bottom part, and body part of the container. As a result, it could only be applied to the molding of resin containers having different body lengths.

[0004] On the other hand, for example, in order to mold containers having different shapes, such as a circular cross-sectional shape in the horizontal directions of the upper part and bottom part of the container and a square cross-sectional shape in the horizontal direction of the body part, if a conventionally known nested mold composed of upper, middle, and lower three stages is simply used, due to the necessity of connecting the upper part, body part, and bottom part of the molded container flush, an edge will form at the boundary between the molds, resulting in problems such as burrs forming at the edge part of the molded product, the edge part being too sharp and having weak strength, or conversely, the edge part not being formed neatly and distortion occurring (see FIG. 7).

[0005] The boundary line (ridge line) connecting the upper part and body part, and the body part and bottom part of the resin container needs to be an R surface in order to exhibit the function as a resin container, even if it is slightly small. However, in the mold configuration shown in FIG. 7 above, a neat R surface without burrs cannot be formed at the boundary line (ridge line).

[0006] Furthermore, in the nesting mold described in Patent Document 1 shown in Figure 8, the rounded edges (R-shaped lines) of the boundary lines (ridges) connecting the top and body of the resin container, and the body and bottom, are realized by the rounded edges formed in the upper mold and lower mold, respectively. Therefore, it can only be applied to molding containers of different lengths by simply changing the middle mold. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2011-37038 [Overview of the project] [Problems that the invention aims to solve]

[0008] The present invention aims to provide a nesting blow molding die that uses a three-tiered nesting die for blow molding resin containers, using the upper and lower tiers as common dies and providing multiple types of middle tiers with different inner surface shapes, thereby enabling the molding of resin containers with different shapes, such as circular, elliptical, and quadrilateral polygonal cross-sections of the container body, and enabling the molding of the boundary lines (ridges) connecting the top and body, and the body and bottom of the resin container, into desired R-shaped surfaces without burrs. [Means for solving the problem]

[0009] To achieve the above objective, the present invention provides a nesting mold for blow molding of resin containers, wherein the resin container molded by the nesting mold comprises an upper part, a body part, and a bottom part, and between the upper part and the body part, and between the body part and the bottom part, Consists of horizontal planes Having an upper connecting surface and a lower connecting surface, The aforementioned nesting mold consists of an upper mold, a middle mold, and a lower mold. The upper mold and the middle mold are joined at the upper surface of the upper connecting surface. The middle mold and the lower mold are joined at the upper surface of the lower connecting surface. [Effects of the Invention]

[0010] According to the present invention, a nested mold consisting of three stages (upper, middle, and lower) is used for blow molding of resin containers. By using the upper and lower molds as a common type and preparing multiple types of middle molds with different inner surface shapes, it is possible to easily mold resin containers with the same shape for the top and bottom of the container, but with different shapes for the cross-section in the lateral direction, such as circular, elliptical, and polygonal, as well as different lengths for the body.

[0011] Alternatively, conversely, by using a single common middle mold and preparing multiple upper and lower molds with different inner surface shapes, it is possible to easily mold multiple types of resin containers with the same body shape but different top and bottom shapes.

[0012] Furthermore, by applying the desired R-shape processing to the intermediate mold at the boundary lines (ridges) connecting the upper connection surface and the body of the resin container, and the body and the lower connection surface, the ridges can be molded into smooth, burr-free R-shapes. [Brief explanation of the drawing]

[0013] [Figure 1] A longitudinal cross-sectional view of a nesting mold and a molded resin container according to one embodiment of the present invention. [Figure 2] An example of a resin container that can be molded according to the present invention. [Figure 3] Longitudinal cross-sectional view of a mold for increasing the length of a resin container. [Figure 4] Exploded view (longitudinal cross-sectional view) of a nesting mold. [Figure 5] Plan view and longitudinal cross-sectional view of the upper mold. [Figure 6] Plan view and longitudinal cross-sectional view of the middle mold. [Figure 7] Comparative example of simply applying conventional technology [Figure 8] Diagram showing conventional nesting molds. [Best Mode for Carrying Out the Invention]

[0014] Hereinafter, embodiments of the present invention will be described in detail. First, a resin container such as PET that can be molded by the present invention (hereinafter referred to as a container) has an upper part 1, a body part 2, and a bottom part 3 as shown in FIG. 2, and between the upper part 1 and the body part 2, and between the body part 2 and the bottom part 3, respectively Consists of horizontal planes having a predetermined width It is a container having an upper connection surface 7 (corresponding to a so-called shoulder) and a lower connection surface 8.

[0015] As an example, the body part 2 of the container shown in FIG. 2(a) is a quadrangular prism, the body part 2 of the container shown in FIG. 2(b) is a cylinder, and the shapes of the upper part 1 and the bottom part 3 of the container shown in FIG. 2(a) and the upper part 1 and the bottom part 3 of the container shown in FIG. 2(b) are the same. The body part 2 is not limited to a cylinder or a quadrangular prism, and may be an elliptical cylinder, a triangular prism, a prism with five or more sides, or any other shape (the cross-section of the body part 2 in the lateral direction may be any shape such as a circle, an ellipse, or a polygon).

[0016] The boundary ridge line between the upper connection surface 7 of the container and the body part 2 and the boundary ridge line between the lower connection surface 8 and the body part 2 are formed as an R surface 9 that has the strength required for the container and takes into account the user's touch and the design.

[0017] FIG. 1 is a longitudinal sectional view of a nested mold used for molding the container shown in FIG. 2 and the container molded by this mold.

[0018] The nested mold is composed of three types: an upper mold 4, a middle mold 5, and a lower mold 6, and is configured as a mold that is symmetrically divided into two parts so that the molded container can be taken out of the mold.

[0019] As shown in the figure, the upper mold 4 and the middle mold 5 are joined at the upper surface of the upper connection surface 7 of the container, and the middle mold 5 and the lower mold 6 are joined at the upper surface of the lower connection surface 8 of the container. Further, the middle mold 5 is subjected to R surface processing so that the boundary ridge line between the upper connection surface 7 of the container and the body part and the boundary ridge line between the lower connection surface 8 and the body part become the R surface 9, respectively.

[0020] The resin container molded using the nesting mold according to the present invention is, for example, molded by injection blow molding. This involves heating a test tube-shaped preform (parison) created by injection molding to soften it, then setting it in the mold, blowing high-pressure air into the internal space of the preform to inflate it, and molding it to conform to the inner surface shape of the mold. However, the molding method is not limited to this.

[0021] As shown in Figure 1, the configuration consisting of an upper mold 4, a middle mold 5, and a lower mold 6 allows for the use of a single type (common) with the same internal shape for the upper mold 4 and the lower mold 6, while replacing the middle mold 5 with one with a different internal shape. This enables the molding of containers with different shapes, such as cylindrical and rectangular prism shapes, for the body 2, as shown in Figures 2(a) and (b). Furthermore, the boundary ridge between the upper connection surface 7 and the body 2, and the boundary ridge between the lower connection surface 8 and the body 2, are molded as smooth R-shaped surfaces 9, resulting in a clean container without burrs on the ridges.

[0022] Furthermore, while minute protrusions are formed at the joints between the two molds on the upper connecting surface 7 and lower connecting surface 8 of the container molded with the nesting mold of the present invention, these protrusions are concentric with the neck (mouth) and bottom of the circular container, so leaving them as part of the design does not pose any particular problem.

[0023] Figure 3 shows an example of molding a container with the same lateral cross-sectional shape as the body 2 of the container shown in Figure 1, but with a longer body 2 and increased capacity by using a longer intermediate mold 5. The basic mold configuration is the same as that shown in Figure 1, so a detailed explanation is omitted.

[0024] Figure 3 shows an example using a middle mold 5 that matches the length of the container body 2. However, to adjust the length, the middle mold 5 may be divided into multiple sections in the length direction, as in the conventional technology shown in Figure 8. In this case, tiny protrusions are formed at the joints between the molds, resulting in an uneven surface on the side of the container body 2. Therefore, in the example shown in Figure 3, the middle mold 5 is matched to the length of the container body 2. Multiple lengths of the middle mold 5 may be prepared depending on the length of the container to be molded.

[0025] Figure 4 is an exploded view (vertical cross-sectional view) of the nesting mold according to the present invention. As shown in the figure, the nesting mold is constructed by connecting three types of molds vertically: an upper mold 4, a middle mold 5, and a lower mold 6. The upper mold 4, middle mold 5, and lower mold 6 are each symmetrically divided into two sections as indicated by their centerlines. In the illustrated example, auxiliary molds 6-1 and 6-2 are used to assist the lower mold 6 in order to create various shapes for the bottom surface of the container bottom 3, but the invention is not limited to this configuration.

[0026] Figure 5 shows a plan view and a longitudinal cross-sectional view of the intermediate mold 5. Figure 5(a) is a plan view of the mold that forms the body 2 of the container into a cylindrical shape, and Figure 5(b) is a plan view of the mold that forms the body 2 of the container into a rectangular prism. Figure 5(c) is a longitudinal cross-sectional view of each intermediate mold 5. As described above, the intermediate mold 5 is configured to be symmetrically divided into two parts as shown by the center line. The inner surface shape of the intermediate mold 5 may be such that the transverse cross-section (plan view) includes any shape, such as multiple types of circles, multiple types of ellipses, or multiple types of polygons, to match the shape of the body of the container to be molded.

[0027] Figure 6 shows plan views and longitudinal cross-sectional views of the upper mold 4, which has different internal shapes. Figure 6(a) is a plan view of the mold that forms the upper part 1 of the container into a rectangular shape in plan view, and Figure 6(b) is a plan view of the mold that forms the upper part 1 of the container into a circular shape in plan view. Figures 6(c) to (e) are longitudinal cross-sectional views of the molds that form the shape from the neck of the container to the upper connecting surface 7 into a trapezoid, a convex arc, and a concave arc, respectively, in longitudinal cross-sectional view. As described above, the upper mold 4 is also configured to be symmetrically divided into two parts as shown by the center line.

[0028] By preparing various upper molds 4 with different inner surface shapes as shown in Figure 6, and using one specific (common) middle mold 5 with the same inner surface shape, it is possible to mold various types of resin containers in which the body 2 has the same shape, but the top part 1 of the container has different shapes in both plan view and / or vertical cross-sectional view.

[0029] In addition, while multiple types of lower molds 6 with different inner surface shapes may be prepared for molding the bottom portion 3, similar to the upper mold 4 and middle mold 5, the bottom portion 3 of a container generally does not have a significant impact on the overall design of the container. Therefore, in the embodiment of the present invention, one common mold is used.

[0030] Here, we will explain again the difference between the mold configuration shown in Figure 7, which is a simple example of using the prior art, and the mold configuration according to the present invention. The mold shown in Figure 7 is also composed of three types, an upper mold 4, a middle mold 5, and a lower mold 6, similar to the present invention. The middle mold 5 can be made to form containers of the shapes shown in Figures 2(a) and 2(b) by using molds with various shapes for the inner surface, such as circular or square in the lateral cross-section, to match the shape of the body 2 of the container.

[0031] However, since the middle mold 5 is used to mold only the body 2 of the container, the upper part 1 of the container including the upper connecting surface 7 is molded in the upper mold 4, and the bottom part 3 of the container including the lower connecting surface 8 is molded in the lower mold 6, an edge portion 10 is formed at the boundary between the upper mold 4 and the middle mold 5, and at the boundary between the middle mold 5 and the lower mold 6. This can lead to problems such as burrs forming on the edge portion 10 of the molded product, the edge portion 10 becoming too sharp and weakening the strength, or conversely, the edge portion 10 not being molded cleanly and causing distortion.

[0032] To resolve the above problem, even if continuous R-surface processing is applied to the joints between the upper mold 4 and the middle mold 5, and between the middle mold 5 and the lower mold 6, so that the edge portion 10 becomes an R-surface, tiny protrusions are formed at the joints of the two molds, making it impossible to form a clean R-surface.

[0033] In other words, as shown in Figure 7, simply dividing the upper mold 4, middle mold 5, and lower mold 6 at the boundary between the upper connecting surface 7 and the body 2, and the boundary between the body 2 and the lower connecting surface 8, does not allow for the molding of a beautifully finished container.

[0034] In contrast, the present invention makes it possible to neatly mold multiple types of resin containers with different body or upper shapes while using the upper mold 4 and lower mold 6 in common, or by using the middle mold 5 in common, by making the joining points between the upper mold 4 and the middle mold 5, and between the middle mold 5 and the lower mold 6, on the surfaces of the upper connecting surface 7 and the lower connecting surface 8, respectively.

[0035] As described above, according to the present invention, a nested mold used for blow molding a resin container comprising an upper part 1, a body part 2, and a bottom part 3, with an upper connecting surface 7 and a lower connecting surface 8 between the upper part 1 and the body part 2, and between the body part 2 and the bottom part 3, is provided, consisting of an upper mold 4, a middle mold 5, and a lower mold 6. The upper mold 4 and the middle mold 5 are joined at the upper surface of the upper connecting surface 7, and the middle mold 5 and the lower mold 6 are joined at the upper surface of the lower connecting surface 8 to mold the resin container. By using one type (common) with the same specific shape for the inner surfaces of the upper mold 4 and the lower mold 6, and by preparing multiple types of middle molds 5 with different inner surfaces, it is possible to easily mold resin containers of different shapes, such as cylinders, elliptical cylinders, and polygonal cylinders (with circular, elliptical, or polygonal cross-sections in the horizontal direction), not only in terms of length but also in shape.

[0036] Conversely, by using one specific (common) intermediate mold 5 with the same internal shape, and preparing multiple types of upper molds 4 with different internal shapes, it is possible to easily mold multiple types of resin containers with the same body shape 2 but different upper shapes 1.

[0037] Furthermore, by applying the desired R-surface processing to the middle mold 5 at the boundary lines (ridges) connecting the upper connection surface 7 of the resin container and the body 2, and the body 2 and the lower connection surface 8, the ridges can be molded into smooth, burr-free R-surfaces. [Explanation of symbols]

[0038] 1. Top of the container 2. Container body 3 Bottom of container 4. Upper mold 5. Middle mold 6. Lower mold 7 Upper connection surface 8. Lower connection surface 9 R side 10 Edge section

Claims

1. A nesting mold used for blow molding of resin containers, wherein the resin container molded by the nesting mold comprises an upper part, a body part, and a bottom part, and between the upper part and the body part, and between the body part and the bottom part, there is an upper connecting surface and a lower connecting surface, both consisting of horizontal planes. The aforementioned nesting mold consists of an upper mold, a middle mold, and a lower mold. The upper mold and the middle mold are joined at the upper surface of the upper connecting surface. The middle mold and the lower mold are joined at the upper surface of the lower connecting surface. A nesting blow molding die characterized by the following features.

2. The upper mold, the middle mold, and the lower mold are each composed of two parts. The nesting blow molding die according to feature 1.

3. The aforementioned middle section of the mold has rounded edges where the boundary lines between the body, the upper connecting surface, and the lower connecting surface are located. The nesting blow molding die according to feature 1.

4. The lateral cross-section of the middle mold used to form the body portion is circular, elliptical, or polygonal. The nesting blow molding die according to feature 1.

5. The upper mold and the lower mold have an internal surface shape of one specific type, while the middle mold has a cross-sectional surface on its internal surface that includes multiple types of circular, elliptical, or polygonal shapes. The nesting blow molding die according to feature 4.

6. The aforementioned intermediate mold includes multiple types with different lengths. The nesting blow molding die according to feature 1.

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