Deep-drawn container and method for manufacturing a deep-drawn container

Abstract

To provide a deep-drawn container with excellent rigidity. [Solution] A deep-drawn container in the shape of a truncated pyramid with a bottom, having a side wall 10 and a bottom wall 20, and having a storage space S formed inside, wherein a stepped portion 30 is formed between the lower end periphery of the side wall 10 and the periphery of the bottom wall 20, having two sides 31 and 32 that are recessed toward the storage space S and extend in the circumferential direction, and the boundary portion R1 between the lower end periphery of the side wall 10 and the stepped portion 30, and the boundary portion R2 between the periphery of the bottom wall 20 and the stepped portion 30 are curved surfaces with a radius of curvature of 0.5 mm or more and 3.5 mm or less.

Description

Technical Field

[0001] The present invention relates to a deep drawing container and a method for manufacturing the same.

Background Art

[0002] At the cash register of a convenience store, self-service sales of coffee beverages and the like may be made. As a container for such coffee beverages and the like, for example, a resin deep drawing container is used.

[0003] Patent Document 1 discloses a tapered cup-shaped container for sealing that houses coffee beverages and the like. The tapered cup-shaped container for sealing has a side wall formed in a tapered shape, a bottom wall, and a flange portion extending radially outward from the upper end edge of the side wall. This tapered cup-shaped container for sealing is formed through three forming steps. The three forming steps include a first step of forming a sheet-shaped circular blank into a straight cylindrical shape with a bottom, a second step of performing deep drawing on the first straight cylindrical body with a bottom obtained here to obtain a second straight cylindrical body with a bottom, and a third step of forming the second straight cylindrical body with a bottom into a tapered cylindrical shape with a bottom. In any of the steps, a die having an inner peripheral surface along the outer surface shape of the obtained cylindrical body and a punch having an outer peripheral surface of a similar shape are used.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Incidentally, when deep-drawn containers are formed using the die and punch described above, there is a problem in that the thickness of the side walls decreases and the rigidity weakens as the drawing ratio increases. To solve this problem, deep-drawn containers are sometimes formed by plug-assisted molding. When formed by plug-assisted molding, the thinning of the lower end of the side walls is suppressed in particular, so the rigidity of the deep-drawn container can be improved compared to when plugs are not used.

[0006] However, in deep-drawn containers, the thinning of the side walls is unavoidable due to the stretching of the resin sheet. Therefore, when deep-drawn containers are subjected to vertical pressure, there is still a problem with the bottom and side walls being prone to buckling. There is a demand for deep-drawn containers with superior rigidity. [Means for solving the problem]

[0007] To solve the above problems, the deep-drawn container of the present invention is a frustoconical deep-drawn container with a bottom and a bottom wall, and a storage space formed inside, wherein a stepped portion is formed between the lower end periphery of the side wall and the periphery of the bottom wall, having two sides that are recessed toward the storage space and extend in the circumferential direction, and the boundary portion between the lower end periphery of the side wall and the stepped portion, and the boundary portion between the periphery of the bottom wall and the stepped portion are curved surfaces with a radius of curvature of 0.5 mm or more and 3.5 mm or less.

[0008] According to the above configuration, a step is formed between the lower edge of the side wall and the edge of the bottom wall, creating a small curved surface with a radius of curvature of 0.5 mm to 3.5 mm at the boundary with the lower edge of the side wall and the boundary with the edge of the bottom wall. Therefore, the force that would deform the deep-drawn container due to pressure applied in the vertical direction is easily absorbed by the bottom wall as it acts to compress it. Buckling of the side walls is suppressed because the bottom wall, which is connected via the step, deforms before the side walls. A deep-drawn container with excellent rigidity can be obtained.

[0009] In the above configuration, it is preferable that the width of the side surface of the stepped portion is 1.0 mm or more and 4.0 mm or less. With the above configuration, because the size of the stepped section is small, the volume of the storage space inside the deep-drawn container can be secured even when the stepped section is formed. The buckling strength of the side wall is improved, and the reduction in the volume of the storage space is suppressed.

[0010] In the above configuration, it is preferable that the thickness of the lower part of the side wall is greater than the thickness of the upper part of the side wall. With the above configuration, where the lower part of the side wall near the bottom wall is relatively thick, the buckling strength of the side wall is improved.

[0011] In the above configuration, it is preferable that the thickness of the side wall at its vertical center is greater than the thickness of the side wall at its upper part. With the above configuration, in which the central part of the side wall in the vertical direction is relatively thick, the buckling strength of the side wall is further improved.

[0012] In the above configuration, it is preferable that the material be made of polyethylene terephthalate resin. According to the above configuration, it has transparency and a superior appearance. To solve the above problems, the present invention provides a method for manufacturing a deep-drawn container, wherein a sheet made of polyethylene terephthalate resin with a sheet thickness of 0.6 mm or more and 1.0 mm or less is molded by a plug-assisted molding method.

[0013] According to the above configuration, thinning of the lower part of the side wall is suppressed, resulting in a deep-drawn container with high buckling strength and excellent rigidity. [Effects of the Invention]

[0014] According to the present invention, a deep-drawn container with excellent rigidity can be obtained. [Brief explanation of the drawing]

[0015] [Figure 1] This is a perspective view of the deep-drawn container of this embodiment. [Figure 2] This is a cross-sectional view of a deep-drawn container and a magnified view of a part of it. [Figure 3]This is a diagram for explaining the measurement locations when measuring the side wall thickness and the bottom wall thickness.

Embodiments for Carrying Out the Invention

[0016] <Regarding the Shape of the Deep Drawn Container> As shown in FIG. 1, the deep drawn container 1 of the present embodiment (hereinafter, may be referred to as the container 1) is formed in a frustum of a cone shape with a bottom, having a side wall 10 and a bottom wall 20. The inside partitioned by the side wall 10 and the bottom wall 20 is a storage space S for beverages, food, etc. Further, an opening 11 is formed at the upper edge of the side wall 10. In the following description, with the bottom wall 20 on the lower side and the opening 11 on the upper side, the bottom wall 20 side will be described as the lower side of the container 1 and the opening 11 side will be described as the upper side of the container 1.

[0017] As shown in FIG. 2, the side wall 10 is formed in a tapered shape that continuously expands in diameter upward. The inclination angle of the side wall 10 is preferably about 2° to 30°, more preferably about 2° to 10°. Also, when the ratio of the area (mm 2 ) of the flange portion 40 including the opening 11 of the container 1 to the surface area (mm 2 ) of the container 1 is defined as the draw ratio, the draw ratio is preferably 0.5 or more and 1.2 or less, and more preferably 0.7 or more and 1.0 or less.

[0018] Since the container 1 is a deep drawn container, the thickness of the side wall 10 may be partially different. The thickness of the side wall 10 is preferably 0.1 mm or more at any part of the side wall 10, and more preferably 0.2 mm or more. Also, it is preferable that the thickness at the lower part of the side wall 10 is thicker than the thickness at the upper part of the side wall 10. Further, it is more preferable that the thickness at the central part in the vertical direction of the side wall 10 is thicker than the thickness at the upper part of the side wall 10 and the thickness at the lower part of the side wall 10 is thicker than the thickness at the central part in the vertical direction of the side wall 10. Generally, in a deep drawn container, the central part tends to be thinner than the upper and lower parts of the side wall, but if the thickness of the central part is thicker than the upper part, the side wall buckling strength will be further improved.

[0019] The thickness of the bottom wall 20 is preferably 0.3 mm or more, and more preferably 0.35 mm or more, at any part of the bottom wall 20. When the thickness of the bottom wall 20 is 0.35 mm or more, the buckling strength of the bottom wall is improved when a vertical pressure is applied to the container 1.

[0020] As shown in FIG. 2, at the upper part of the side wall 10, a diameter-expanding portion 12 that expands the diameter discontinuously from the lower part is formed. Further, at the upper end edge of the side wall 10, a flange portion 40 that extends radially outward from the upper end edge is formed. When a plurality of containers 1 are stacked, the flange portion 40 of the lower container 1 abuts on the lower surface of the diameter-expanding portion 12 of the upper container 1 to form a stacked state.

[0021] As shown in the enlarged view on the right side of FIG. 2, a stepped portion 30 is formed between the lower peripheral edge of the frustum-shaped side wall 10 and the peripheral edge of the circular bottom wall 20. The stepped portion 30 has a shape in which the boundary portion between the lower end portion of the side wall 10 and the peripheral portion of the bottom wall 20 is recessed toward the accommodation space S side. The stepped portion 30 has two side surfaces 31 and 32 that extend in the circumferential direction of the container 1.

[0022] The side surface 31 extends substantially parallel to the side wall 10. Further, the side surface 32 extends substantially parallel to the bottom wall 20. As shown in the enlarged view of FIG. 2, the width W1 of the side surface 31 and the width W2 of the side surface 32 of the stepped portion 30 are formed to be approximately the same. The width W1 of the side surface 31 and the width W2 of the side surface 32 are both preferably 1.0 mm or more and 4.0 mm or less, and more preferably 1.2 mm or more and 3.0 mm or less.

[0023] Further, the boundary portion R1 between the lower peripheral edge of the side wall 10 and the side surface 32, and the boundary portion R2 between the peripheral edge of the bottom wall 20 and the side surface 31 are formed as curved surfaces. The radius of curvature of the boundary portion R1 and the boundary portion R2 is preferably 0.5 mm or more and 3.5 mm or less, and more preferably 1.0 mm or more and 2.5 mm or less. When the widths W1 and W2 of the side surfaces 31 and 32 of the stepped portion 30 and the radii of curvature of the boundary portions R1 and R2 are within this range, the buckling strength of the side wall 10 is improved when a vertical pressure is applied to the container 1.

[0024] Container 1 is molded from a conventionally known resin material. Examples of resin materials include conventionally known thermoplastic resins and thermosetting resins. Container 1 in this embodiment is made of polyethylene terephthalate resin.

[0025] <Regarding the manufacturing method of deep-drawn containers> Next, we will explain how to manufacture container 1. Container 1 is formed by conventionally known plug-assisted molding.

[0026] In the manufacturing method of the container 1 of this embodiment, first, a resin sheet made of polyethylene terephthalate resin is prepared. The sheet thickness of the resin sheet is preferably 0.6 mm or more and 1.0 mm or less, and more preferably 0.75 mm or more and 0.85 mm or less.

[0027] The resin sheet is heated and softened, then set onto a mold that has a recess in the shape of container 1 and multiple vacuum suction holes. Next, the mold is pushed up to stretch the resin sheet, and air is sucked out through the vacuum suction holes to create a vacuum. Simultaneously with the vacuum suction, pressure is applied from above with a plug to hold it in place. As a result, the resin sheet adheres tightly to the recess of the mold and is molded to the shape of the recess.

[0028] After the resin sheet is molded, it is cooled and solidified. Finally, any unnecessary parts are trimmed to obtain container 1. <About the function of deep-drawn containers> The function of container 1, along with its effects, will be described below.

[0029] A stepped portion 30 is formed between the side wall 10 and the bottom wall 20 of the container 1. The boundary portion R1 between the lower edge of the side wall 10 and the stepped portion 30 is a curved surface with a radius of curvature of 0.5 mm or more and 3.5 mm or less. Similarly, the boundary portion R2 between the edge of the bottom wall 20 and the stepped portion 30 is also a curved surface with a radius of curvature of 0.5 mm or more and 3.5 mm or less. When such a small stepped portion 30 is formed at the lower end of the side wall 10 of the container 1, when pressure is applied to the container 1 in the vertical direction, wrinkles form around the periphery of the stepped portion 30. By forming wrinkles around the periphery of the stepped portion 30, the vertical pressure is absorbed by the bottom wall 20, and deformation of the side wall 10 of the container 1 is suppressed. The stepped portion 30 acts to suppress deformation and crushing of the side wall 10 of the container 1. Furthermore, if the radius of curvature at the boundary portions R1 and R2 of the stepped portion 30 is in the range of 0.5 mm to 3.5 mm, a side wall buckling strength of 17 kgf or more can be obtained.

[0030] The width W1 of the side surface 31 of the stepped section 30 is 1.0 mm or more and 4.0 mm or less, and the width W2 of the side surface 32 is also 1.0 mm or more and 4.0 mm or less. If the radius of curvature at the boundary portions R1 and R2 of the stepped section 30 is within the above range, the widths W1 of the side surface 31 and W2 of the side surface 32 of the stepped section 30 can also be set smaller, making the stepped section 30 smaller. As a result, the internal volume of the storage space S of the container 1 can be increased. A container 1 that can achieve both rigidity and storage volume can be obtained. The buckling strength of the side wall 10 is improved, and the decrease in the volume of the storage space S can be suppressed.

[0031] Container 1 is formed by plug-assisted molding. As a result, there is little variation in the thickness of the side walls 10, and the entire container has a uniform thickness. Although there is little variation in the thickness of the side walls 10, when considering the thickness of the side walls 10 as a whole, the thickness of the lower part of the side walls 10 of container 1 in this embodiment is greater than the thickness of the upper part of the side walls 10. This improves the buckling strength of the side walls 10.

[0032] Furthermore, in general, deep-drawn containers tend to be thinner in the central part of the side wall compared to the upper and lower parts due to the stretching of the resin sheet. In this regard, if the thickness of the side wall 10 in the vertical center is greater than the thickness of the side wall 10 in the upper part, and the thickness of the side wall 10 in the lower part is greater than the thickness of the side wall 10 in the vertical center, the side wall buckling strength will be further improved.

[0033] Furthermore, if the thickness of the bottom wall 20 is 0.3 mm or more, the buckling strength of the bottom wall 20 is improved. According to this embodiment, in addition to the above, the following effects can also be obtained. Container 1 is made of polyethylene terephthalate resin. Therefore, it is transparent and has a superior appearance.

[0034] The upper part of the side wall 10 of container 1 has an enlarged diameter section 12 that expands discontinuously from the lower part. In addition, the upper edge of the side wall 10 has a flange section 40 that extends radially outward from the upper edge. Therefore, when multiple containers 1 are stacked, the flange section 40 of the lower container 1 abuts against the lower surface of the enlarged diameter section 12 of the upper container 1, creating a stacked state. Multiple containers 1 can be stored stably.

[0035] The above embodiment can be modified as follows. Note that the above embodiment and the following modifications can be combined and applied to the extent that they do not contradict each other technically. The shape of the container 1 is not limited to that of the above embodiment. It is sufficient that a stepped portion 30 is provided between the side wall 10 and the bottom wall 20, with a curved surface having a radius of curvature within the above numerical range. For example, it may be a frustoconical shape or a frustoconical shape.

[0036] The side wall 10 does not have to be tapered. The width W1 of the side surface 31 and the width W2 of the side surface 32 of the stepped section 30 do not have to be between 1.0 mm and 4.0 mm.

[0037] The thickness of the side wall 10 at the bottom may be less than the thickness of the side wall 10 at the top. The thickness of the side wall 10 at its vertical center may be thinner than the thickness of the side wall 10 at its upper part. The molding method for container 1 does not have to be plug-assisted molding. Air slip molding may also be used.

[0038] The technical concept understood from the above embodiments is described below. (a) A deep-drawn container having side walls and a bottom wall, with a storage space formed inside, wherein a stepped portion is formed between the lower end periphery of the side wall and the periphery of the bottom wall, having two sides that are recessed toward the storage space and extend in the circumferential direction, the boundary portion between the lower end periphery of the side wall and the stepped portion, and the boundary portion between the periphery of the bottom wall and the stepped portion are curved surfaces with a radius of curvature of 0.5 mm or more and 3.5 mm or less, and the buckling strength of the side wall is 17.0 kgf or more.

[0039] (b) A method for manufacturing a deep-drawn container having side walls and a bottom wall and having a storage space formed inside, comprising a molding step of molding a sheet made of polyethylene terephthalate resin with a sheet thickness of 0.6 mm or more and 1.0 mm or less by a plug-assist molding method, wherein in the molding step, a stepped portion having two sides that are recessed toward the storage space and extend in the circumferential direction is formed between the lower end periphery of the side wall and the periphery of the bottom wall, and a curved surface with a radius of curvature of 0.5 mm or more and 3.5 mm or less is formed at the boundary portion between the lower end periphery of the side wall and the stepped portion, and at the boundary portion between the periphery of the bottom wall and the stepped portion. [Examples]

[0040] Next, the embodiments described above will be explained in more detail with reference to examples of the subordinate squeezing container. It should be noted that the present invention is not limited to the configurations described in the Examples section. <Test Example 1> A polyethylene terephthalate (PET) sheet with a thickness of 0.8 mm was prepared. This PET sheet was set in a mold, and container 1 of Test Example 1 was molded by plug-assisted molding. Container 1 of Test Example 1 has stepped sections 30 with widths W1 and W2 of approximately 1.5 mm. The radius of curvature at the boundary R1 between the lower edge of the side wall 10 and the stepped section 30 is approximately 1 mm, and the radius of curvature at the boundary R2 between the periphery of the bottom wall 20 and the stepped section 30 is approximately 1 mm. The diameter of the opening 11 is approximately 120 mm, the height is approximately 110 mm, and the diameter of the bottom surface of the bottom wall 20 is approximately 61 mm. The reduction ratio is 1.067.

[0041] <Test Example 2> Plug-assisted molding was performed in the same manner as in Test Example 1. In Test Example 2, container 1 has a stepped portion 30 with a width W1 of approximately 1 mm and a width W2 of approximately 1 mm. The radius of curvature at the boundary portion R1 between the lower edge of the side wall 10 and the stepped portion 30 is approximately 0.5 mm, and the radius of curvature at the boundary portion R2 between the periphery of the bottom wall 20 and the stepped portion 30 is approximately 0.5 mm. The diameter of the opening 11 is approximately 106 mm, the height is approximately 78 mm, and the diameter of the lower surface of the bottom wall 20 is approximately 69 mm. The aperture ratio is 0.876.

[0042] <Test Example 3> The container 1 in Test Example 3 was formed using plug-assisted molding in the same manner as in Test Example 1. The container 1 in Test Example 3 has stepped sections 30 with widths W1 and W2 of approximately 3.5 mm. The radius of curvature at the boundary R1 between the lower edge of the side wall 10 and the stepped section 30 is approximately 3 mm, and the radius of curvature at the boundary R2 between the periphery of the bottom wall 20 and the stepped section 30 is approximately 3 mm. The diameter of the opening 11 is approximately 106 mm, the height is approximately 78 mm, and the diameter of the lower surface of the bottom wall 20 is approximately 60 mm. The aperture ratio is 0.876.

[0043] <Test Example 4> Plug-assisted molding was performed in the same manner as in Test Example 1. The container 1 in Test Example 4 does not have the stepped portion 30 formed. The diameter of the opening 11 is approximately 106 mm, the height is approximately 78 mm, and the diameter of the lower surface of the bottom wall 20 is approximately 68 mm. The diaphragm ratio is 0.876.

[0044] <Measurement of side wall thickness and bottom wall thickness> As shown in Figure 3, the thickness of the side wall 10 of container 1 in each test example was measured at multiple locations. The measurement locations were a total of 17 locations: four around the flange portion 40 (A1-A4), four around the perimeter 20 mm below the opening 11 (B1-B4), four around the perimeter at the vertical center of the side wall 10 (C1-C4), four around the perimeter 20 mm above the inner surface of the bottom wall 20 (D1-D4), and one at the center of the bottom wall 20 (E1). Locations A1, A2, A3, and A4 were set at positions 90° apart on the side wall 10 of container 1. The same applies to locations B1-B4, C1-C4, and D1-D4.

[0045] The thickness measurement results are shown in Table 1. The notations for the measurement locations correspond to those shown in Figure 3. In addition, the average value was calculated for four locations around the flange portion 40, four locations 20 mm below the opening 11, four locations around the vertical center of the side wall 10, and four locations 20 mm above the inner surface of the bottom wall 20. The calculated values ​​are shown in the right column of each measured value. The unit of measurement for wall thickness is mm.

[0046] [Table 1]

[0047] <Measurement of buckling strength> The buckling strength of container 1 for each test example was measured. The buckling strength was measured using an Autograph AGS-X (manufactured by Shimadzu Corporation) in accordance with JIS Z0238 (1998). Container 1 was set on a compression test stand with its opening 11 facing upwards. Pressure was applied to container 1 from above at a speed of 10 mm / min. The load at which the bottom wall 20 of container 1 deformed was measured as the bottom wall buckling strength, and the load at which the side wall 10 of container 1 deformed was measured as the side wall buckling strength. The results are shown in Table 2. The unit of buckling strength is kgf.

[0048] [Table 2]

[0049] As shown in Table 2, in Test Examples 1-3, where a stepped portion 30 was formed between the side wall 10 and the bottom wall 20, the buckling strength of the side wall 10 was 17 kgf or more. Also, in Test Examples 1-3, where the thickness of the lower part of the side wall 10 was thicker than the thickness of the upper part of the side wall 10, the buckling strength of the side wall 10 was a high value of 17 kgf or more. In Test Example 1, where the thickness of the vertical center of the side wall 10 was thicker than the thickness of the upper part of the side wall 10, and the thickness of the lower part of the side wall 10 was thicker than the thickness of the vertical center of the side wall 10, the buckling strength of the side wall 10 was a very high value of 18 kgf or more.

[0050] In Test Examples 1-3, where the thickness of the base wall 20 at its center was 0.3 mm or more, the buckling strength of the base wall 20 was high, at 6 kgf or more. Furthermore, in Test Examples 2 and 3, where the thickness of the base wall 20 at its center was 0.35 mm or more, the buckling strength of the base wall 20 was extremely high, at 9 kgf or more. [Explanation of symbols]

[0051] R1, R2…boundary part S... Containment space W1, W2... width 1…Container (deep-drawn container) 10...Side wall 20...Bottom wall 30...Double part 31, 32... side view

Claims

1. A deep-drawn container with a frustum shape and bottom, having side walls and a bottom wall, and having a storage space formed inside, A stepped portion is formed between the lower end periphery of the side wall and the periphery of the bottom wall, having two sides that are recessed toward the storage space and extend in the circumferential direction. A deep-drawn container characterized in that the boundary portion between the lower end periphery of the side wall and the stepped portion, and the boundary portion between the periphery of the bottom wall and the stepped portion, are curved surfaces with a radius of curvature of 0.5 mm or more and 3.5 mm or less.

2. The deep-drawn container according to claim 1, wherein the width of the side surface of the stepped portion is 1.0 mm or more and 4.0 mm or less.

3. The deep-drawn container according to claim 1, wherein the thickness of the lower part of the side wall is greater than the thickness of the upper part of the side wall.

4. The deep-drawn container according to claim 3, wherein the thickness of the side wall at its vertical center is greater than the thickness of the side wall at its upper part.

5. A deep-drawn container according to any one of claims 1 to 4, which is made of polyethylene terephthalate resin.

6. A method for manufacturing a deep-drawn container according to claim 1, characterized in that a sheet made of polyethylene terephthalate resin with a sheet thickness of 0.6 mm or more and 1.0 mm or less is formed by a plug-assist molding method.

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