Extruded blow molded body

Abstract

An extruded blow-molded body is obtained that can be formed into a double-walled container from which the inner container can be easily removed from the outer container. [Solution] The invention comprises a bottomed cylindrical inner preform 10 for forming an inner container X1 and a bottomed cylindrical outer preform 20 for forming an outer container X2. The inner preform 10 is inserted into the outer preform 20 with the inner opening 11 of the inner preform 10 fitted into the outer opening 21 of the outer preform 20. The inner preform 10 has a cylindrical inner body 12 and an inner bottom 13 which is formed in a convex curved shape that is convex downward from the inflection point 12a at the lower end of the inner body 12, with the center of the bottom surface being the lowest point of the bottom 13a. The lowest point of the bottom 13a is located on the central axis O of the inner preform 10, and the radius r of the outer surface of the inner bottom 13 is greater than the height dimension h from the lowest point of the bottom 13a to the inflection point 12a, and smaller than the radius of curvature R1 of the outer surface of the inner bottom 13.

Description

Technical Field

[0001] The present invention relates to an extrusion blow molded body.

Background Art

[0002] There is known a double container having a mouth part, a body part, and a bottom part connected in this order, composed of an outer container and an inner container, and capable of taking out the inner container from inside the outer container into a separated state (see, for example, Patent Document 1). A preform for forming such a double container includes a bottomed cylindrical inner preform for forming the inner container and a bottomed cylindrical outer preform for forming the outer container. A double container is obtained by biaxially stretch blow molding this preform.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the conventional double container, when separating by pulling out the inner container from the outer container, there is a problem that it is difficult to take out the bottom part of the inner container because it gets caught on the mouth part of the outer container.

[0005] The present invention has been made in view of the above circumstances, and an object thereof is to provide an extrusion blow molded body capable of forming a double container from which the inner container can be easily taken out from the outer container.

Means for Solving the Problems

[0006] To solve the above problems, the present invention employs the following means. That is, the extruded blow molded body of the present invention is an extruded blow molded body for forming a double container comprising an inner container that deforms in volume as the contents contained therein decrease, and an outer container in which the inner container is housed, comprising a bottomed cylindrical inner preform for forming the inner container and a bottomed cylindrical outer preform for forming the outer container, wherein the inner preform is inserted into the outer preform with the mouth of the inner preform fitted into the mouth of the outer preform, and the inner preform has a cylindrical body and a bottom that is convex downward from the inflection point at the lower end of the body and is formed in the shape of a convex curved surface with the center of the bottom surface being the lowest point of the bottom, the lowest point of the bottom is located on the central axis of the inner preform, and the radius of the outer surface of the bottom is greater than the height dimension from the lowest point of the bottom to the inflection point and smaller than the radius of curvature of the outer surface of the bottom.

[0007] In this invention, the convex curved shape of the bottom of the inner preform is greater than the curvature of a perfect circle, resulting in a curved shape that approaches flatness. Therefore, the stretching distance of the bottom of the inner preform is increased during extrusion blow molding, making the bottom of the inner preform thinner. As a result, the bottom of the inner container in the double-walled container obtained by blow molding the resulting extrusion blow molded body is also molded to be thin. With this configuration, when separating the double-walled containers, the thin bottom of the inner container deforms easily when the inner container is pulled out from inside the outer container. Therefore, the bottom of the inner container does not get caught on the opening of the outer container, and the inner container can be easily removed from the outer container. [Effects of the Invention]

[0008] According to this invention, an extruded blow-molded body is obtained that can be formed into a double-walled container from which the inner container can be easily removed from the outer container. [Brief explanation of the drawing]

[0009] [Figure 1] This is a longitudinal cross-sectional view of the lower part of an extruded blow-molded body shown as one embodiment, with the section broken. [Modes for carrying out the invention]

[0010] The extruded blow-molded body according to the embodiment will be described below with reference to the drawings. As shown in Figure 1, the extruded blow molded body 1 is used to mold a double container X which comprises an inner container X1 that deforms in volume as the contents it contains decrease, and an outer container X2 in which the inner container X1 is housed.

[0011] The double-walled container X is formed by blow molding an extruded blow-molded body 1, which causes the portion below the mouth to be, for example, biaxially stretched. In the double-walled container X, the inner container X1 is highly flexible and is spaced apart on the inner surface of the outer container X2.

[0012] The extruded blow molded body 1 comprises a bottomed cylindrical inner preform 10 for molding the inner container X1 and a bottomed cylindrical outer preform 20 for molding the outer container X2. The extruded blow molded body 1 is obtained by separately extruding blow molding the inner preform 10 and the outer preform 20, and then inserting the inner preform 10 into the outer preform 20. The inner preform and the outer preform may each be molded as a single layer or laminated together. Furthermore, the outer preform 20 is not limited to extruded blow molding but may also be injection molded. The opening (hereinafter referred to as the inner opening) 11 of the inner preform 10 is inserted into the opening (hereinafter referred to as the outer opening) 21 of the outer preform 20, and the bottom (hereinafter referred to as the inner bottom) 13 of the inner preform 10 is inserted into the bottom (hereinafter referred to as the outer bottom) 23 of the outer preform 20.

[0013] The inner preform 10 and the outer preform 20 are arranged coaxially with the common axis. Hereinafter, this common axis will be referred to as the central axis O, the inner opening 11 side and the outer opening 21 side along the central axis O will be referred to as the upper side, and the inner bottom 13 side and the outer bottom 23 side along the central axis O will be referred to as the lower side. When viewed from above or below, the direction intersecting the central axis O will be referred to as the radial direction, and the direction revolving around the central axis O will be referred to as the circumferential direction.

[0014] The materials of the inner preform 10 and the outer preform 20 are synthetic resin materials, and they may be made of the same material or different materials. Examples of synthetic resin materials include PET (polyethylene terephthalate), PP (polypropylene), PE (polyethylene), nylon (polyamide), and EVOH (ethylene-vinyl alcohol copolymer). The materials of the inner preform 10 and the outer preform 20 can be appropriately selected so that the inner container X1 can be separated and sorted from the outer container X2.

[0015] The inner opening 11 is fitted inside the outer opening 21. Between the outer circumferential surface of the inner preform 10 and the inner circumferential surface of the outer preform 20, a gap is provided along the entire length in the vertical direction in the portion located below the inner opening 11 and the outer opening 21.

[0016] The inner opening 11 has a fitting portion 15 that can be rotated together with at least one other side in the circumferential direction and fits into a mounting portion of, for example, a cap (not shown). The fitting portion 15 has a plurality of ribs 15a provided on the outer circumferential surface of the fitting portion 15 at circumferentially offset positions and fitting into the mounting portion, and a downward-facing stepped surface 15b provided on the outer circumferential surface of the fitting portion 15 and fitting into the mounting portion. The inner opening 11 has a flange-shaped mounting portion 16 that rests on the upper end surface of the outer opening 21.

[0017] The inner opening 11 is a portion of the inner preform 10 that includes the same position in the vertical direction as the lower surface of the neck ring 21a, which will be described later, in the outer preform 20, and is located above it. In the extruded blow molded body 1, the portion that includes the same position in the vertical direction as the lower surface of the neck ring 21a, and is located above it, is a portion whose shape does not change before and after blow molding.

[0018] The outer mouth portion 21 is fitted outside the inner mouth portion 11. The outer mouth portion 21 forms a neck ring 21a. The neck ring 21a protrudes radially outward from the outer mouth portion 21 and extends continuously over the entire circumferential length. The neck ring 21a is located below the peripheral wall portion of a cap (not shown).

[0019] The outer preform 20 has a cylindrical outer barrel portion 22 and an outer bottom portion 23 that protrudes downward from the lower end of the outer barrel portion 22 and is formed in a convex curved surface shape with the center of the bottom surface being the bottom lowest point 23a.

[0020] The inner peripheral surface and the outer peripheral surface of the outer barrel portion 22 extend along the central axis O in a longitudinal sectional view along the central axis O. At least the inner peripheral surface of the inner peripheral surface and the outer peripheral surface of the outer barrel portion 22 extends parallel to the central axis O. In the illustrated example, the inner peripheral surface and the outer peripheral surface of the outer barrel portion 22 extend parallel to the central axis O. Here, the "parallel" means that even a draft from a mold that is not completely parallel to the central axis O is regarded as parallel.

[0021] The bottom lowest point center C2, which is the center of curvature of the outer bottom portion 23, is located on the central axis O. The radius of curvature R2 of the outer bottom portion 23 is smaller than the radius of curvature R1 at which the inner bottom portion 13 is formed.

[0022] The inner preform 10 has a cylindrical inner barrel portion 12 and an inner bottom portion 13 that protrudes downward from the inflection point 12a at the lower end of the inner barrel portion 12 and is formed in a convex curved surface shape with the center of the bottom surface being the bottom lowest point 13a. The inflection point 12a is the point where the straight inner barrel portion 12 begins to curve toward the inner bottom portion 13.

[0023] The inner peripheral surface and the outer peripheral surface of the inner barrel portion 12 extend along the central axis O in a longitudinal sectional view along the central axis O. At least the inner peripheral surface of the inner peripheral surface and the outer peripheral surface of the inner barrel portion 12 extends parallel to the central axis O. In the illustrated example, the inner peripheral surface and the outer peripheral surface of the inner barrel portion 12 extend parallel to the central axis O. Here, the "parallel" includes the draft from the mold.

[0024] The bottom lowest point center C1, which is the center of curvature of the inner bottom portion 13, is located on the central axis O. In the inner preform 10, in the radial direction orthogonal to the central axis O, the radius r of the outer peripheral surface of the inner bottom portion 13 is set to be larger than the height dimension h from the bottom lowest point 13a of the inner bottom portion 13 to the inflection point 12a (h < r), and is set to be smaller than the radius of curvature R1 of the outer peripheral surface of the inner bottom portion 13 (R1 > r). The radius of curvature R1 of the inner bottom portion 13 is larger than the radius of curvature R2 of the outer bottom portion 23.

[0025] Also, in the inner preform 10, the inner cylindrical portion 12 and the inner bottom portion 13 are smoothly connected in a curved surface shape.

[0026] As described above, according to the extrusion blow molded body 1 according to the present embodiment, the inner preform 10 has a cylindrical inner cylindrical portion 12 and an inner bottom portion 13 formed in a convex curved surface shape that protrudes downward from the inflection point 12a at the lower end of the inner cylindrical portion 12 and has the bottom center as the bottom lowest point 13a. The bottom lowest point center C1, which is the center of curvature of the inner bottom portion 13, is located on the central axis O of the inner preform 10. In the radial direction orthogonal to the central axis O, the radius r of the outer peripheral surface of the inner bottom portion 13 is larger than the height dimension h from the bottom lowest point 13a of the inner bottom portion 13 to the inflection point 12a, and is smaller than the radius of curvature R1 of the outer peripheral surface of the inner bottom portion 13.

[0027] With such a configuration, the convex curved surface shape of the inner bottom portion 13 of the inner preform 10 becomes a curved surface shape that is larger than the curvature of a perfect circle and approaches being flat. Therefore, during extrusion blow molding, the stretching distance of the inner bottom portion 13 of the inner preform 10 becomes longer, so the inner bottom portion 13 of the inner preform 10 becomes thin-walled, and the bottom portion of the inner container X1 in the double container X obtained by blow molding the obtained extrusion blow molded body 1 is also formed to be thin-walled. With the above configuration, when separating the double container X, when pulling up the inner container X1 from inside the outer container X2, the thin-walled bottom portion of the inner container X1 is easily deformed, so the inner container X1 can be easily taken out from the outer container X2 without being caught on the mouth portion of the outer container X2.

[0028] As described above, with the extruded blow molded body 1 according to this embodiment, the inner container X1 can be easily removed from the outer container X2.

[0029] Furthermore, the technical scope of the present invention is not limited to the embodiments described above, and various modifications can be made without departing from the spirit of the invention.

[0030] In this embodiment, the inner body portion 12 and the inner bottom portion 13 of the inner preform 10 are smoothly connected in a curved shape, but the inner body portion 12 and the inner bottom portion 13 may be made to be approximately right angles apart. However, if they are made to be right angles apart, the right-angle portion will be thin and may break, so it is preferable that the inner body portion 12 and the inner bottom portion 13 are connected in a curved shape as in this embodiment.

[0031] Furthermore, the double-walled container may be provided with an air intake hole to introduce outside air between the inner container X1 and the double-walled container as the contents decrease. In this case, the air intake hole may be provided in the outer opening 21, or it may be provided between the upper end surface of the outer opening 21 and the lower surface of the mounting portion 16.

[0032] Furthermore, without departing from the spirit of the present invention, the components in the above embodiments may be replaced with well-known components as appropriate, and the above embodiments and modifications may be combined as appropriate. [Explanation of Symbols]

[0033] 1. Extruded blow molded body 10 Internal preform 11. Inner opening (opening of the inner preform) 12 Inner torso 12a Inflection point 13. Inner bottom 13a Bottom lowest point 20 External preforms 21 Outer opening (opening of the outer preform) 22 Outer casing 23 Outer bottom C1 Center of the lowest point of the inner bottom C2 The center of the lowest point of the outer bottom O Central axis X Double Container X1 Container X2 outer container

Claims

[Claim 1] The inner container deforms and decreases in volume as the contents it holds decrease, An extruded blow molded body for forming a double container comprising an outer container in which the inner container is housed, It comprises a bottomed cylindrical inner preform for forming the inner container and a bottomed cylindrical outer preform for forming the outer container, With the opening of the inner preform fitted into the opening of the outer preform, the inner preform is inserted into the outer preform. The internal preform has a cylindrical body and a bottom that is formed in a convex curved shape, which is convex downward from the inflection point at the lower end of the body, with the center of the bottom surface being the lowest point of the bottom. The lowest point of the bottom is located on the central axis of the inner preform, An extruded blow-molded body wherein the radius of the outer surface of the bottom is greater than the height dimension from the lowest point of the bottom to the inflection point, and smaller than the radius of curvature of the outer surface of the bottom.

Images