Double container

Abstract

To provide a double container of which the inner bag can be easily pulled out from the outer shell.SOLUTION: In a double container with a container body, the container body includes a mouth part, a body part, and a bottom part, the mouth part is a tubular part having an open end, the body part is arranged adjacent to the mouth part on a side farther from the open end than the mouth part, and has a larger outer diameter than the mouth part, the bottom part is configured to close the lower end of the body part, the container body includes an inner bag and an outer shell arranged to cover the inner bag, on the bottom part of the inner bag are provided a thin wall part and alternate thick-wall shapes that are thicker than the thin wall part and appear alternately in the circumferential direction.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention discloses a double container.

Background Art

[0002] Conventionally, a double container having a container body with an outer shell and an inner bag is known. For example, Patent Document 1 discloses performing biaxial stretch blow molding in a state where an outer shell preform and an inner bag preform are overlapped to form a double container (so-called laminated peelable container) configured such that the inner bag contracts as the content decreases.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, when the outer shell and the inner bag of such a double container are formed of different materials, or when the content adheres to the inner bag after use, etc., when recycling the double container, it is desirable to separate the outer shell and the inner bag.

[0005] The present invention has been made in view of such circumstances, and provides a double container capable of easily pulling out the inner bag from the outer shell.

Means for Solving the Problems

[0006] According to the present invention, there is provided a double container including a container body, wherein the container body includes a mouth portion, a body portion, and a bottom portion. The mouth portion is a cylindrical portion having an open end. The body portion is disposed adjacent to the mouth portion on a side farther from the open end than the mouth portion and has an outer diameter larger than that of the mouth portion. The bottom portion is configured to close the lower end of the body portion. The container body includes an inner bag and an outer shell disposed so as to cover the inner bag. An alternating wall thickness shape in which a thin wall portion and a thick wall portion having a larger wall thickness than the thin wall portion alternately appear in the circumferential direction is provided at the bottom of the inner bag.

[0007] Since the outer diameter of the body portion of the container body is larger than that of the mouth portion, it is not easy to pull out the inner bag through the mouth portion simply by pulling the inner bag. However, by twisting the inner bag to reduce the diameter of the body portion, the body portion of the inner bag can easily pass through the mouth portion of the outer shell. On the other hand, in a conventional double container, even if the inner bag is simply twisted, the bottom portion is not easily reduced in diameter and it is not easy to pull out the bottom portion from the mouth portion.

[0008] In the double container of the present invention, an alternating wall thickness shape in which a thin wall portion and a thick wall portion alternately appear in the circumferential direction is provided at the bottom of the inner bag. When such a shape is provided, bending is likely to occur selectively in the thin wall portion when the inner bag is twisted, and as a result, the bottom portion of the inner bag is easily deformed into a bellows shape and reduced in diameter. Therefore, in the double container of the present invention, when the inner bag is twisted, the bottom portion is easily reduced in diameter, so that the inner bag can be easily pulled out from the outer shell.

[0009] Hereinafter, various embodiments of the present invention will be exemplified. The embodiments shown below can be combined with each other. Preferably, in the double container described above, a bottom concave region and a peripheral region surrounding the bottom concave region are provided at the bottom of the inner bag, and the alternating wall thickness shape is provided on at least one of the circumferential surface of the bottom concave region and the peripheral region. Preferably, in the double container described above, the alternating wall thickness shape is provided so as to span the circumferential surface and the peripheral region. Preferably, the double container described above, wherein the alternating wall thickness shape is provided so as to span the peripheral region and the side surface of the inner bag, is a double container. Preferably, the double container described above, wherein the thin wall portion is formed by providing a concave groove on one or both of the inner and outer surfaces of the inner bag, is a double container. Preferably, in the double container described above, when the wall thickness of the inner bag at the thin wall portion in a cross section perpendicular to the height direction of the inner bag is T1 and the wall thickness of the inner bag at the thick wall portion is T2, the minimum value of T1 / T2 is 0.8 or less, and it is a double container.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Embodiments for Carrying Out the Invention

[0011] Hereinafter, embodiments of the present invention will be described. Various characteristic matters shown in the following embodiments can be combined with each other. Also, an invention can be established independently for each characteristic.

[0012] 1. Double container 1 As shown in FIG. 1, the double container 1 according to an embodiment of the present invention includes a container body 2 and a mouthpiece mounting member 8.

[0013] As shown in FIG. 1, the container body 2 includes a mouth portion 5, a body portion 6, and a bottom portion 7. The mouth portion 5 is a cylindrical (preferably cylindrical) portion having an open end 5c. The mouth portion 5 includes an engaging portion 5a to which a mouthpiece mounting member 8 such as a cap or a pump can be mounted. When the mouthpiece mounting member 8 is screw-type, the engaging portion 5a is a male screw portion, and when the mouthpiece mounting member 8 is a stopper type, it is an annular protrusion protruding in the circumferential direction. The mouthpiece mounting member 8 preferably has a check valve (not shown), and although the discharge of the content is possible, outside air is prevented from flowing into the container body 2. A flange 5b is provided on the mouth portion 5. The flange 5b can be used to support the mouth portion 5 when mounting the mouthpiece mounting member 8 to the mouth portion 5.

[0014] The body portion 6 is disposed adjacent to the mouth portion 5 on the side away from the opening end 5c of the mouth portion 5. The body portion 6 has a larger outer diameter than the mouth portion 5 (in this specification, the "outer diameter" means the circumscribed circle diameter when the cross section is not circular). The body portion 6 is cylindrical, and the bottom portion 7 is provided at the lower end of the body portion 6 and closes the lower end of the body portion 6. The body portion 6 includes a shoulder portion 6b whose outer diameter increases as it moves away from the mouth portion 5, and a body portion main body 6c provided on the bottom portion 7 side of the shoulder portion 6b and having a substantially constant outer diameter.

[0015] The diameter of the mouth portion 5 excluding the engaging portion 5a is, for example, 20 to 40 mm, preferably 25 to 35 mm, specifically, for example, 20, 25, 30, 35, 40 mm, and may be within the range between any two of the values exemplified here. The length of the mouth portion 5 is, for example, 15 to 35 mm, specifically, for example, 15, 20, 25, 30, 35 mm, and may be within the range between any two of the values exemplified here.

[0016] As shown in FIG. 2, the container body 2 includes an inner bag 4 and an outer shell 3 disposed so as to cover the inner bag 4. Except for the protruding portion 4c described later, the other parts of the inner bag 4 are accommodated in the outer shell 3. In the following description, the parts of the inner bag 4 corresponding to the mouth portion 5, the body portion 6, and the bottom portion 7 of the container body 2 are respectively referred to as the mouth portion 5, the body portion 6, and the bottom portion 7 of the inner bag 4. The same applies to the outer shell 3.

[0017] When a check valve is provided in the mouth portion mounting member 8, the inner bag 4 contracts as the content of the inner bag 4 is discharged. When a check valve is not provided in the mouth portion mounting member 8, the inner bag 4 does not contract even after the content of the inner bag 4 is discharged, so it is not easy to pull out the inner bag 4 through the mouth portion 5 of the outer shell 3. Since the present invention facilitates pulling out the inner bag 4 through the mouth portion 5 of the outer shell by twisting and reducing the diameter of the inner bag 4, when a check valve is not provided in the mouth portion mounting member 8, the significance of applying the present invention is particularly remarkable. However, even when a check valve is provided in the mouth portion mounting member 8, the inner bag 4 may not appropriately reduce its diameter when contracting, so even when a check valve is provided in the mouth portion mounting member 8, the significance of applying the present invention is remarkable.

[0018] The body portion 6 or the bottom portion 7 is provided with an outside air introduction hole 16. The outside air introduction hole 16 is a through hole penetrating the outer shell 3, and outside air can be introduced into the intermediate space between the outer shell 3 and the inner bag 4 through the outside air introduction hole 16. When the double container 1 is a so-called squeeze-type container configured to discharge the contents by compressing the outer shell 3, it is preferable to provide a check valve for controlling the inflow and outflow of air through the outside air introduction hole 16. The check valve is preferably configured to close the outside air introduction hole 16 when the outer shell 3 is compressed and to open the outside air introduction hole 16 when the compression force is removed. In this case, when a compression force is applied to the outer shell 3, the compression force is likely to be applied to the inner bag 4, and after the contents are discharged, outside air is quickly introduced into the intermediate space, and the shape of the outer shell 3 is quickly restored.

[0019] When a check valve is provided in the outside air introduction hole 16, the outside air introduction hole 16 is preferably disposed in a recess 6d provided in the body portion 6. In this case, it is possible to avoid interference between the check valve and the shrink film when the body portion 6 is covered with the shrink film. Further, it is preferable to provide a groove 6e extending from the recess 6d toward the mouth portion 5. The groove 6e extends to a position not covered with the shrink film. Thereby, it is possible to avoid the recess 6d being sealed with the shrink film.

[0020] As shown in Fig. 2, it is preferable that an uneven shape 9 in which concave stripes 9a and convex stripes 9b alternately appear in the circumferential direction of the mouth part 5 is provided on at least one of the inner surfaces of the mouth part 5 and the position adjacent to the mouth part 5 in the body part 6. The uneven shape 9 is provided on the inner surface of the inner bag 4. The number of the concave stripes 9a is, for example, 4 to 30, and preferably 10 to 20. The concave stripes 9a and the convex stripes 9b preferably extend non-parallel to each other in the circumferential direction of the mouth part 5. The direction in which the concave stripes 9a and the convex stripes 9b extend is preferably 0 to 60 degrees, and more preferably 0 to 30 degrees, with respect to the axial direction of the mouth part 5. Specifically, this angle is, for example, 0, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60 degrees, and may also be within the range between any two of the numerical values exemplified here. The uneven shape 9 may be provided only on the mouth part 5, or may be provided at a position adjacent to the mouth part 5 in the body part 6, but is preferably provided across the mouth part 5 and the body part 6. The uneven shape 9 may be formed by reducing the wall thickness of the concave stripe 9a compared to other parts of the mouth part 5 of the inner bag 4, or by increasing the wall thickness of the convex stripe 9b, or by reducing the wall thickness of the concave stripe 9a and increasing the wall thickness of the convex stripe 9b.

[0021] Since the wall thickness of the convex stripe 9b is larger than that of the concave stripe 9a, when the twist applied to the mouth part 5 is transmitted to the body part 6, the convex stripe 9b transmits force more easily than the concave stripe 9a. As a result, the convex stripe 9b rotates faster than the concave stripe 9a, and thus, a crease is formed in the inner bag 4 on the concave stripe 9a and its extension line, making it easy to fold the inner bag 4 in a pleated shape. Therefore, by providing the uneven shape 9, the body part 6 is folded in a pleated shape, and as a result, the diameter of the body part 6 is quickly reduced. It should be noted that it is preferable not to provide an uneven shape on the outer surface of the inner bag 4. This is because if an uneven shape is provided on the outer surface of the inner bag 4, the inner bag 4 and the outer shell 3 engage with each other in the rotation direction of the inner bag 4, making it difficult for the inner bag 4 to rotate relative to the outer shell 3.

[0022] Let the wall thickness of the inner bag 4 at the rib 9b of the mouth part 5 (the radius of the circumscribed circle of the inner bag 4 - the radius of the inscribed circle passing through the apex of the rib 9b) be T, and the depth of the groove 9a (the radius of the inscribed circle passing through the bottom of the groove 9a - the radius of the inscribed circle passing through the apex of the rib 9b) be D. Then, the maximum value of D / T is, for example, 0.2 to 0.8, and preferably 0.3 to 0.5. Specifically, this value is, for example, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, and it may also be within the range between any two of the numerically illustrated values. The wall thickness of the inner bag 4 at the part of the mouth part 5 other than the concavo-convex shape 9 is, for example, 1 to 2 mm, specifically, for example, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0 mm, and it may also be within the range between any two of the numerically illustrated values. The depth of the groove 9a at the part where the depth of the groove 9a is maximum is, for example, 0.3 to 1.0 mm, specifically, for example, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0 mm, and it may also be within the range between any two of the numerically illustrated values.

[0023] The distance from the open end 5c of the mouth part 5 to the upper end of the concavo-convex shape 9 is, for example, 0 to 30 mm, specifically, for example, 0, 5, 10, 15, 20, 25, 30 mm, and it may also be within the range between any two of the numerically illustrated values. The distance from the upper end to the lower end of the concavo-convex shape 9 is, for example, 10 to 40 mm, specifically, for example, 10, 15, 20, 25, 30, 35, 40 mm, and it may also be within the range between any two of the numerically illustrated values.

[0024] As shown in FIGS. 6 to 8, a protrusion 4e is provided at the bottom 7 of the inner bag 4. An annular convex portion 3b is provided at the bottom 7 of the outer shell 3, and a through hole 3c is provided in the region inside the annular convex portion 3b. By inserting the protrusion 4e into the through hole 3c, the inner bag 4 is positioned with respect to the outer shell 3. Since the annular convex portion 3b and the region inside it are hardly stretched during biaxial stretch blow molding, the wall thickness is increased in both the outer shell 3 and the inner bag 4.

[0025] When the outer diameter of the annular convex portion 3b is D1 and the inner diameter of the mouth portion 5 of the outer shell 3 is D2, it is preferable that D1 / D2 is 0.9 or less. Since the thickness of the inner bag 4 increases in the annular convex portion 3b and the region inside thereof, the smaller D1 / D2 is, the easier it is for the bottom portion 7 of the inner bag 4 to have its diameter reduced. D1 / D2 is, for example, from 0.1 to 0.9, and specifically, for example, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, and it may also be within the range between any two of the numerical values exemplified herein.

[0026] In the bottom portion 7 of the container body 2 (that is, the bottom portions 7 of the inner bag 4 and the outer shell 3 respectively), a bottom concave region 7a and a peripheral region 7b surrounding the bottom concave region 7a are provided. The bottom concave region 7a is a region where the bottom portion 7 is recessed toward the inside of the container body 2. The peripheral region 7b serves as the grounding surface of the container body 2. As shown in FIG. 6A, on the peripheral surface 7a1 of the bottom concave region 7a, as approaching the peripheral region 7b, the thicknesses of the inner bag 4 and the outer shell 3 respectively gradually become thinner. The peripheral surface 7a1 is an inclined surface inclined so as to move away from the center of the bottom portion 7 toward the peripheral region 7b. In other words, the peripheral surface 7a1 constitutes a part of a cone that constricts toward the bottom surface 7a2 of the bottom concave region 7a. The bottom surface 7a2 of the bottom concave region 7a is substantially flat. For this reason, the bottom concave region 7a has a substantially frustum - of - cone shape.

[0027] The bottom surface 7a2 of the bottom concave region 7a is difficult to be stretched during biaxial stretch blow molding and is likely to have a large thickness. Therefore, the smaller the diameter D3 of the bottom surface 7a2 (in other words, the diameter of the region surrounded by the boundary line between the bottom surface 7a2 and the peripheral surface 7a1) is, the easier it is for the bottom portion 7 of the inner bag 4 to have its diameter reduced. It is preferable that D3 / D2 is 0.9 or less. D3 / D2 is, for example, from 0.1 to 0.9, and specifically, for example, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, and it may also be within the range between any two of the numerical values exemplified herein.

[0028] As shown in FIGS. 6 to 8, an alternating wall thickness shape 10 is provided at the bottom 7 of the inner bag 4, where a thin wall portion 10a and a thick wall portion 10b having a greater wall thickness than the thin wall portion 10a appear alternately in the circumferential direction of the inner bag 4. By providing the alternating wall thickness shape 10 at the bottom 7, when the inner bag 4 is twisted, the thin wall portion 10a bends, causing the bottom 7 to deform into a bellows shape and making it easier for the bottom 7 to have its diameter reduced.

[0029] As shown in FIG. 6C, since the circumferential surface 7a1 has a greater wall thickness than the side surface 4d of the inner bag 4 in the vicinity of the bottom 7, it is particularly important to provide the alternating wall thickness shape 10 on the circumferential surface 7a1 in order to make it easier to reduce the diameter of the bottom 7. Also, since the peripheral region 7b is less deformable than the side surface 4d of the inner bag 4 in the vicinity of the bottom 7, it is particularly important to provide the alternating wall thickness shape 10 on the peripheral region 7b. Therefore, the alternating wall thickness shape 10 is preferably provided on at least one of the circumferential surface 7a1 of the bottom concave region 7a and the peripheral region 7b, and more preferably provided so as to straddle the circumferential surface 7a1 and the peripheral region 7b. It is also preferable that it is provided so as to straddle the peripheral region 7b and the side surface 4d of the inner bag 4. By providing the alternating wall thickness shape 10 in this way, the bottom 7 becomes even more easily reducible in diameter.

[0030] As shown in FIG. 7B, the thin wall portion 10a and the thick wall portion 10b are preferably provided so as to extend radially from the center of the bottom 7. Also, the number of thin wall portions 10a is, for example, 4 to 30, and preferably 10 to 20.

[0031] The thin wall portion 10a can be formed by providing a concave groove 11 on one or both of the inner surface and the outer surface of the inner bag 4. The concave groove 11 on the inner surface of the inner bag 4 and the concave groove 11 on the outer surface face each other. The portion between two adjacent concave grooves 11 becomes the thick wall portion 10b.

[0032] When the wall thickness of the inner bag 4 at the thin-wall portion 10a in a cross-section perpendicular to the height direction of the inner bag 4 (a cross-section like that in Fig. 6C) is T1 and the wall thickness of the inner bag 4 at the thick-wall portion 10b is T2, the minimum value of T1 / T2 is preferably 0.8 or less. The minimum value of T1 / T2 is the minimum value calculated for T1 / T2 at each height position by moving the position of the cross-section along the height direction of the inner bag 4. The smaller T1 / T2 is, the smaller the thickness of the thin-wall portion 10a becomes compared to the thick-wall portion 10b, and the easier it is for the bottom portion 7 to be deformed into a bellows shape. This value is preferably 0.1 or more. If this value is too small, the thickness at the thin-wall portion 10a becomes too small and pinholes are likely to occur. This value is, for example, from 0.1 to 0.8, specifically, for example, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, and it may also be within the range between any two of the numerical values exemplified herein.

[0033] The mouthpiece mounting member 8 is preferably configured to be mountable on the mouthpiece 5 and to rotate the inner bag 4 as the mouthpiece mounting member 8 rotates (here, relative rotation with respect to the outer shell 3). According to such a configuration, it is possible to twist the inner bag 4 by rotating the mouthpiece mounting member 8. Since the diameter of the body portion 6 of the container body 2 is larger than that of the mouthpiece 5, it is not easy to pull out the inner bag 4 through the mouthpiece 5 of the outer shell 3 simply by pulling the inner bag 4. However, by twisting the inner bag 4 to reduce the diameter of the body portion 6 of the inner bag 4, the body portion 6 of the inner bag 4 can easily pass through the mouthpiece 5 of the outer shell 3, and the inner bag 4 can be easily pulled out from the outer shell 3.

[0034] Hereinafter, the engagement structure between the mouthpiece mounting member 8 and the inner bag 4 will be described more specifically.

[0035] As shown in Figs. 2 and 3, the inner bag 4 includes a protruding portion 4c that protrudes from the open end 3a of the outer shell 3. The protruding portion 4c includes a protruding cylinder 4c1, an engagement protrusion 4c2, an engagement flange 4c3, and an abutment flange 4c4.

[0036] The engaging projection 4c2 projects radially outward from the circumferential surface of the protruding cylinder 4c1. The engaging flange 4c3 is an annular portion that is disposed at a position farther from the opening end 3a than the engaging projection 4c2 and has a larger diameter than the protruding cylinder 4c1. The abutting flange 4c4 is an annular portion that is disposed at a position abutting against the opening end 3a and has a larger diameter than the protruding cylinder 4c1. By the abutting flange 4c4 abutting against the opening end 3a, the inner bag 4 is prevented from falling off into the outer shell 3. On the other hand, the inner bag 4 may be prevented from falling off into the outer shell 3 by causing the engaging projection 4c2 to abut against the opening end 3a without providing the abutting flange 4c4.

[0037] As shown in FIGS. 3 to 5, the mouthpiece mounting member 8 includes an outer cylinder 8a, an intermediate cylinder 8b, an inner cylinder 8c, an engaging portion 8d, a claw portion 8e, a top plate 8f, and a nozzle 8g.

[0038] The engaging portion 8d is provided on the inner surface of the outer cylinder 8a. The engaging portion 8d is an engaging portion that engages with the engaging portion 5a of the mouth portion 5. By engaging the engaging portion 8d with the engaging portion 5a, the mouthpiece mounting member 8 is mounted on the mouth portion 5.

[0039] The intermediate cylinder 8b has a smaller diameter than the outer cylinder 8a and is disposed above the outer cylinder 8a. The inner cylinder 8c is a so-called inner ring that has a smaller diameter than the intermediate cylinder 8b and is disposed inside the outer cylinder 8a and the intermediate cylinder 8b. The upper surface of the intermediate cylinder 8b is covered with the top plate 8f. The nozzle 8g is provided on the top plate 8f.

[0040] The claw portion 8e is provided on the inner surface of the intermediate cylinder 8b. A plurality (eight in this embodiment) of claw portions 8e are provided at intervals in the circumferential direction. The number of claw portions 8e is, for example, from 1 to 20, and preferably from 4 to 12. The claw portion 8e includes an upper surface 8e1 and a lower inclined surface 8e2. A through hole 8h is provided in the top plate 8f at a position facing the claw portion 8e.

[0041] The mouth-mounted member 8 with such a shape can be manufactured using a split mold that opens and closes in the vertical direction. Since the through-hole 8h and the upper surface 8e1 can be formed using the protrusions provided on the upper mold, the claw portion 8e can be formed without forcibly ejecting the lower mold. Therefore, it is not necessary to set the protruding amount of the claw portion 8e to an amount that can be forcibly ejected, and the protruding amount suitable for engagement with the inner bag 4 (e.g., 1 mm or more) can be achieved.

[0042] In this embodiment, since the engaging portion 5a is a male screw portion and the engaging portion 8d is a female screw portion, the mouth-mounted member 8 can be mounted on the mouth portion 5 by relatively rotating the mouth-mounted member 8 with respect to the mouth portion 5 in the tightening direction (usually the clockwise direction when viewed from above) (hereinafter, the relative rotation with respect to the mouth portion 5 is also simply referred to as "rotation"). When the mouth-mounted member 8 is rotated in the tightening direction, while the engaging portion 8d is screwed onto the engaging portion 5a, the claw portion 8e gradually approaches the protruding portion 4c, and at a certain point, the lower inclined surface 8e2 abuts against the engaging flange 4c3. In this state, when the mouth-mounted member 8 is further rotated in the tightening direction, the claw portion 8e overrides the engaging flange 4c3 and reaches the state shown in FIG. 5. In this state, the claw portion 8e is disposed between the engaging flange 4c3 and the abutting flange 4c4. The engaging flange 4c3 is accommodated in the gap between the claw portion 8e and the top plate 8f. As shown in FIG. 5B, the protruding cylinder 4c1 is disposed between the claw portion 8e and the inner cylinder 8c. At this point, if the screws of the engaging portion 5a and the engaging portion 8d are not fully tightened, the claw portion 8e is guided by the circumferential inclined surface 4c5 provided on the engaging protrusion 4c2 to override the engaging protrusion 4c2, and the mouth-mounted member 8 can be further rotated in the tightening direction. After the screws of the engaging portion 5a and the engaging portion 8d are fully tightened, the mouth-mounted member 8 cannot be rotated in the tightening direction and cannot move in the axial direction of the mouth portion 5.

[0043] In this state, the engaging protrusion 4c2 is engaged with the claw portion 8e of the mouth-mounted member 8 in the rotational direction of the mouth-mounted member 8, and the engaging flange 4c3 is engaged with the claw portion 8e of the mouth-mounted member 8 in the axial direction of the mouth portion 5. That is, the claw portion 8e is engaged with the engaging protrusion 4c2 and the engaging flange 4c3.

[0044] Therefore, after the contents in the inner bag 4 are used up, when the mouth - mounting member 8 is rotated in the loosening direction (usually counter - clockwise when viewed from above), the inner bag 4 rotates as the mouth - mounting member 8 rotates. As a result, the inner bag 4 is twisted and its diameter is reduced.

[0045] When the mouth - mounting member 8 is further rotated in the loosening direction and the screwing engagement between the engaging portion 8d and the engaging portion 5a is released, the mouth - mounting member 8 becomes movable in the direction away from the open end 3a (that is, in the axial direction of the mouth portion 5). Since the engaging flange 4c3 is engaged with the mouth - mounting member 8 in the axial direction of the mouth portion 5, when the mouth - mounting member 8 is moved in the axial direction of the mouth portion 5, the inner bag 4 also moves together with the mouth - mounting member 8, and the inner bag 4 is pulled out from the outer shell 3.

[0046] As described above, according to the configuration of the present embodiment, by simply rotating the mouth - mounting member 8 in the loosening direction, after the inner bag 4 is twisted and its diameter is reduced, it can be smoothly pulled out from the outer shell 3, so that the inner bag 4 and the outer shell 3 can be separated smoothly with a simple operation.

[0047] 2. Manufacturing method of the double - container 1 As shown in FIGS. 9 to 11, the container body 2 can be formed by heating a pre - form 15 formed by covering an inner pre - form 14 that becomes the inner bag 4 with an outer pre - form 13 that becomes the outer shell 3 and performing biaxial stretch blow molding.

[0048] As shown in FIG. 9, the inner pre - form 14 is a bottomed cylindrical shape and includes a mouth portion 14a, a body portion 14b, and a bottom portion 14c. A protruding portion 14d is provided at the open end of the mouth portion 14a. The protruding portion 14d remains in its original shape without deformation during molding and becomes the protruding portion 4c. Therefore, the matters described for the protruding portion 4c also apply to the protruding portion 14d. The bottom portion 14c is provided so as to close the lower end of the body portion 14b. A positioning pin 14c1 is provided on the bottom portion 14c.

[0049] As shown in FIG. 10, an uneven shape 19 is provided on the inner surface of the inner preform 14. The uneven shape 19 remains in its original shape or is stretched during molding to become the uneven shape 9 of the container body 2. The description of the uneven shape 9 applies to the uneven shape 19 as well, unless it is contrary to the purpose thereof.

[0050] As shown in FIGS. 9 to 10, in the vicinity of the bottom 14c of the inner preform 14, an alternating wall thickness shape 20 is provided in which a thin wall portion 20a and a thick wall portion 20b having a larger wall thickness than the thin wall portion 20a alternately appear in the circumferential direction. The alternating wall thickness shape 20 is stretched during biaxial stretch blow molding to become the alternating wall thickness shape 10. The number of the thin wall portions 20a is, for example, 4 to 30, and preferably 10 to 20. The thin wall portions 20a are preferably provided in a direction along the longitudinal direction of the inner preform 14.

[0051] The thin wall portion 20a can be formed by providing a concave groove 21 on one or both of the inner surface and the outer surface of the inner preform 14. When the concave groove 21 is provided on the inner surface of the inner preform 14, the concave groove 11 is formed on the inner surface of the inner bag 4 after molding. When the concave groove 21 is provided on the outer surface of the inner preform 14, the concave groove 11 is formed on the outer surface of the inner bag 4 after molding, and the concave groove 11 is also formed on the inner surface of the inner bag 4 at a position facing the concave groove 11 on the outer surface. This is because the resin at a position facing the concave groove 11 is pressed outward by the air pressure during blowing.

[0052] In a cross-section perpendicular to the height direction of the inner preform 14 (a cross-section like that in FIG. 10D), if the wall thickness of the inner bag 4 at the thin-walled portion 20a is t1 and the wall thickness of the inner preform 14 at the thick-walled portion 20b is t2, the minimum value of T1 / T2 is preferably 0.8 or less. The minimum value of t1 / t2 is the minimum value obtained by moving the position of the cross-section along the height direction of the inner preform 14 and calculating t1 / t2 at each height position. The value of t1 / t2 is correlated with T1 / T2, and T1 / T2 can be reduced by reducing t1 / t2. The value of t1 / t2 is preferably 0.1 or more. This value is, for example, from 0.1 to 0.8, specifically, for example, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, and may also be within the range between any two of the numerical values exemplified here.

[0053] As shown in FIG. 9, the outer preform 13 is a bottomed cylindrical shape and includes a mouth portion 13a, a body portion 13b, and a bottom portion 13c. The bottom portion 13c is provided so as to close the lower end of the body portion 13b. An annular convex portion 13d and a positioning hole (not shown) are provided in the bottom portion 13c.

[0054] As shown in FIG. 11, when forming the preform 15, the protruding portion 14d is brought into contact with the open end of the mouth portion 13a, and the positioning pin 14c1 is inserted into the positioning hole. Thereby, the inner preform 14 and the outer preform 13 are positioned relative to each other. In this state, the mouth portion 14a and the mouth portion 13a face each other, and the body portion 14b and the body portion 13b face each other.

[0055] The mouth portions 13a and 14a become the mouth portion 15a of the preform 15, the body portions 13b and 14b become the body portion 15b of the preform 15, and the bottom portions 13c and 14c become the bottom portion 15c of the preform 15. The body portion 15b and the bottom portion 15c are mainly stretched in the biaxial stretch blow molding. However, since the biaxial stretch blow molding is performed while supporting the annular convex portion 13d, the annular convex portion 13d and the inner region thereof are hardly stretched during the biaxial stretch blow molding. The annular convex portion 13d becomes the annular convex portion 3b after molding.

[0056] The inner preform 14 and the outer preform 13 can be formed by direct blow molding or injection molding of thermoplastic resins such as polyester (e.g., PET) and polyolefin (e.g., polypropylene, polyethylene). The inner preform is preferably composed of a material with a larger molding shrinkage rate than the outer preform. In this case, a gap is formed between the outer shell 3 and the inner bag 4 due to molding shrinkage, facilitating the introduction of outside air into the intermediate space between the outer shell 3 and the inner bag 4.

[0057] In one example, the inner preform 14 is composed of polyolefin (e.g., polypropylene), and the outer preform 13 is composed of PET. Since polyolefin has a larger molding shrinkage rate than PET, such a resin composition makes it easier to form a gap between the outer shell 3 and the inner bag 4. Also, by using different materials for the inner preform 14 and the outer preform 13, welding between them during blow molding is suppressed.

[0058] The inner preform 14 is preferably formed by direct blow molding. According to direct blow molding (blow molding using a molten tubular parison), the inner preform 14 with a laminated structure can be easily formed. The outer preform 13 is preferably formed by injection molding.

[0059] After the preform 15 is subjected to biaxial stretch blow molding, the container body 2 shown in FIG. 1 can be obtained by forming an outside air introduction hole 16 in the outer shell 3. Then, after filling the inner bag 4 with the contents, the double container 1 can be obtained by attaching the mouth - mounting member 8 to the mouth portion 5.

[0060] 3. Other Embodiments · In the above - described embodiment, the outside air introduction hole 16 is formed after biaxial stretch blow molding, but a through - hole serving as the outside air introduction hole may be formed in the outer preform 13 in advance. · The outside air introduction hole 16 may be formed at the bottom of the outer shell 3. ·In the present invention, the configuration of twisting the inner bag 4 is not particularly limited, so it does not have to be configured such that the inner bag 4 rotates as the mouth - mounting member 8 rotates. In this case, for example, the inner bag 4 may be pinched with fingers and rotated. Therefore, as the mouth - mounting member 8, a cap or a pump having no structure for engaging with the inner bag 4 may be used. Further, the container body 2 does not have to be provided with the protruding portion 4c. For example, instead of the protruding portion 4c, a flange may be provided at the opening end of the inner bag 4, and by bringing this flange into contact with the opening end of the outer shell 3, it is possible to prevent the inner bag 4 from falling off into the outer shell 3. ·In the above - described embodiment, the alternating - wall - thickness shapes 10 and 20 are realized by forming the concave stripes 11 and 21. However, the alternating - wall - thickness shapes 10 and 20 may be formed by forming convex stripes on one or both of the inner surface and the outer surface of the inner bag 4 or the inner pre - form 14 to form thick - wall portions. Even in this case, as the inner bag 4 is twisted, the thin - wall portions are selectively bent, so that the bottom portion 7 is easily deformed into a bellows shape and its diameter is reduced. ·The annular convex portions 3b and 13d can be omitted.

Explanation of Reference Numerals

[0061] 1: Double - walled container 2: Container body 3: Outer shell 3a: Opening end 3b: Annular convex portion 3c: Through - hole 4: Inner bag 4c: Protruding portion 4c1: Protruding cylinder 4c2: Engaging protrusion 4c3: Engaging flange 4c4: Contact flange 4c5: Circumferential inclined surface 4d: Side surface 4e: Protrusion 5: Mouth portion 5a: Engaging portion 5b: Flange 5c: Opening end 6: Body portion 6b: Shoulder portion 6c: Body - portion main body 6d: Recessed portion 6e: groove 7: bottom 7a: bottom concave region 7a1: peripheral surface 7a2: bottom surface 7b: peripheral edge region 8: mouth mounting member 8a: outer cylinder 8b: intermediate cylinder 8c: inner cylinder 8d: engaging portion 8e: claw portion 8e1: upper surface 8e2: lower inclined surface 8f: top plate 8g: nozzle 8h: through hole 9: concavo-convex shape 9a: concave strip 9b: convex strip 10: alternating wall thickness shape 10a: thin wall portion 10b: thick wall portion 11: concave strip 13: outer preform 13a: mouth portion 13b: body portion 13c: bottom 13d: annular convex portion 14: inner preform 14a: mouth portion 14b: body portion 14c: bottom 14c1: positioning pin 14d: protruding portion 15: preform 15a: mouth portion 15b: body portion 15c: bottom 16: outside air introduction hole 19: concavo-convex shape 20: alternating wall thickness shape 20a: thin wall portion 20b: thick wall portion 21: concave strip

Claims

1. A double container comprising a container body, wherein the container body includes a mouth portion, a body portion, and a bottom portion. The mouth portion is a cylindrical portion having an open end. The body portion is disposed adjacent to the mouth portion on a side farther from the open end than the mouth portion and has an outer diameter larger than that of the mouth portion. The bottom portion is configured to close the lower end of the body portion. The container body includes an inner bag and an outer shell disposed so as to cover the inner bag. An alternating wall thickness shape is provided at the bottom of the inner bag, where thin wall portions and thick wall portions having a greater wall thickness than the thin wall portions alternately appear in the circumferential direction. The double container is configured such that after the inner bag is twisted and its diameter is reduced, it can be pulled out from the outer shell. The thin wall portion is formed by providing concave ridges on one or both of the inner and outer surfaces of the inner bag. A double container.

2. The double container according to Claim 1, wherein the thin wall portion is formed by providing concave ridges on both the inner and outer surfaces of the inner bag. A double container.

3. The double container according to Claim 1 or Claim 2, further comprising a mouth portion mounting member, wherein the mouth portion mounting member is configured to be mountable on the mouth portion and is configured such that the inner bag rotates as the mouth portion mounting member rotates. A double container.

4. The double container according to any one of Claims 1 to 3, wherein a bottom concave region and a peripheral region surrounding the bottom concave region are provided at the bottom of the inner bag, and the alternating wall thickness shape is provided on at least one of the circumferential surface of the bottom concave region and the peripheral region. A double container.

5. The double container according to Claim 4, wherein the alternating wall thickness shape is provided so as to span the circumferential surface and the peripheral region. A double container.

6. The double container according to Claim 4 or Claim 5, wherein the alternating wall thickness shape is provided so as to span the peripheral region and the side surface of the inner bag. A double container.

7. The double container according to any one of Claims 1 to 6, wherein when the wall thickness of the inner bag at the thin wall portion in a cross section perpendicular to the height direction of the inner bag is T1 and the wall thickness of the inner bag at the thick wall portion is T2, the minimum value of T1 / T2 is 0.8 or less. A double container.

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