JP7715980B2 - double container - Google Patents

Description

The present invention discloses a double container.

Double containers with a container body having an outer shell and an inner bag are known. For example, Patent Document 1 discloses a method of forming a double container (a so-called delaminating container) in which an outer shell preform and an inner bag preform are stacked on top of each other and biaxially stretch blow molded, so that the inner bag shrinks as the contents decrease.

JP 2019-10741 A

However, if the outer shell and inner bag of such a double-layered container are made from different materials, or if the contents remain inside the inner bag after use, it is desirable to separate the outer shell and inner bag when recycling the double-layered container.

The present invention was made in light of these circumstances, and provides a double-layered container in which the inner bag can be easily pulled out from the outer shell.

The present invention provides a double-walled container comprising a container body, the container body comprising a mouth, a body, and a bottom, the mouth being a cylindrical portion with an open end, the body being disposed adjacent to the mouth on a side farther from the open end than the mouth and having a larger outer diameter than the mouth, the bottom being configured to close the lower end of the body, the container body comprising an inner bag and an outer shell disposed to cover the inner bag, and the bottom of the inner bag having an alternating thickness profile in which thin-walled sections and thick-walled sections that are thicker than the thin-walled sections alternate in the circumferential direction.

The body of the container body has a larger outer diameter than the mouth, so it is not easy to pull the inner bag out through the mouth simply by pulling on it. However, by twisting the inner bag to reduce the diameter of the body, it becomes easier for the body of the inner bag to pass through the mouth of the outer shell. On the other hand, with conventional double-layered containers, it is difficult to reduce the diameter of the bottom simply by twisting the inner bag, making it difficult to pull the bottom out through the mouth.

In the double-walled container of the present invention, the bottom of the inner bag has an alternating thickness shape, in which thin-walled and thick-walled sections alternate in the circumferential direction. This shape makes it easier for the thin-walled sections to bend selectively when the inner bag is twisted, resulting in the bottom of the inner bag deforming like an accordion and becoming more likely to contract in diameter. Therefore, in the double-walled container of the present invention, twisting the inner bag easily contracts the bottom, making it easy to pull out the inner bag from the outer shell.

Various embodiments of the present invention will be described below as examples, and the embodiments described below can be combined with each other.
Preferably, the double container described above has a bottom recessed area and a peripheral area surrounding the bottom recessed area at the bottom of the inner bag, and the alternating thickness shape is provided on at least one of the peripheral surface of the bottom recessed area and the peripheral area.
Preferably, in the double container described above, the alternating thickness shape is provided so as to span the peripheral surface and the peripheral edge region.
Preferably, in the double-walled container described above, the alternating thickness shape is provided so as to span the peripheral region and the side surface of the inner bag.
Preferably, in the double container described above, the thin-walled portion is formed by providing a groove on one or both of the inner surface and the outer surface of the inner bag.
Preferably, the double-walled container described above is a double-walled container in which, when the thickness of the inner bag at the thin-walled portion in a cross section perpendicular to the height direction of the inner bag is T1 and the thickness of the inner bag at the thick-walled portion is T2, the minimum value of T1/T2 is 0.8 or less.

This is a front view of the double container 1 of one embodiment of the present invention, showing the state in which the mouth attachment member 8 is separated from the container body 2. The dashed-dotted line in the figure indicates the boundary where the curvature of the surfaces that make up the surface shape changes. The same applies to the other figures. 2A is a cross-sectional view taken along line AA in FIG. 1, and FIG. 2B is a cross-sectional view taken along line BB in FIG. 2A. FIG. 2 is an enlarged perspective view of the vicinity of the mouth portion 5 of FIG. 1. FIG. 4A is a perspective view of the mouth-mounted member 8 with a portion cut away, and FIG. 4B is a perspective view of the mouth-mounted member 8 as seen obliquely from below. 5A is a front view of the spout attachment member 8 attached to the container body 2, and FIG. 5B is a cross-sectional view taken along line BB in FIG. 5A. 6A is a cross-sectional view taken along line BB in FIG. 1, FIG. 6B is a front view of the inner bag 4 near the bottom of the container body 2, and FIG. 6C is a cross-sectional view taken along line CC in FIG. 6B. 7A is a perspective view of the vicinity of the bottom of the container body 2 as seen obliquely from below, and FIG. 7B is a perspective view of the inner bag 4 with the outer shell 3 removed from FIG. 7A. 8A is a perspective view of the vicinity of the bottom of the container body 2 as seen obliquely from above, and FIG. 8B is a perspective view of the inner bag 4 in a state where the outer shell 3 is removed from FIG. 8A. FIG. 2 is a perspective view showing a state in which the inner preform 14 and the outer preform 13 are separated. Figure 10A is a front view of the inner preform 14, Figures 10B to 10C are cross-sectional views taken along lines B-B and CC in Figure 10A, respectively, Figure 10D is an enlarged view of the cross-section D-D in Figure 10A, and Figure 10E is a perspective view of the inner preform 14 seen obliquely from above. FIG. 1 is a perspective view of a preform 15 formed by covering an outer preform 13 on an inner preform 14.

The following describes embodiments of the present invention. The various features shown in the following embodiments can be combined with each other. Furthermore, each feature can be an independent invention.

1. double container 1
As shown in FIG. 1, a double container 1 according to one embodiment of the present invention comprises a container body 2 and a mouth attachment member 8 .

As shown in FIG. 1, the container body 2 has a mouth 5, a body 6, and a bottom 7. The mouth 5 is a tubular (preferably cylindrical) portion with an open end 5c. The mouth 5 has an engagement portion 5a to which a mouth attachment member 8, such as a cap or pump, can be attached. The engagement portion 5a is a male threaded portion if the mouth attachment member 8 is a screw-type, or a ring-shaped protrusion that protrudes circumferentially if the mouth attachment member 8 is a stopper-type. The mouth attachment member 8 preferably has a check valve (not shown) that allows the contents to be discharged but prevents outside air from entering the container body 2. The mouth 5 has a flange 5b. The flange 5b can be used to support the mouth 5 when the mouth attachment member 8 is attached to the mouth 5.

The body 6 is positioned adjacent to the mouth 5, farther from the open end 5c than the mouth 5. The body 6 has a larger outer diameter (in this specification, "outer diameter" refers to the circumscribed circle diameter if the cross section is not circular) than the mouth 5. The body 6 is cylindrical, and the bottom 7 is located at the lower end of the body 6 and closes the lower end of the body 6. The body 6 has a shoulder 6b whose outer diameter increases with increasing distance from the mouth 5, and a body main body 6c which is located closer to the bottom 7 than the shoulder 6b and has a substantially constant outer diameter.

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

As shown in FIG. 2, the container body 2 includes an inner bag 4 and an outer shell 3 arranged to cover the inner bag 4. The inner bag 4 is housed within the outer shell 3, except for the protruding portion 4c, which will be described later. In the following description, the portions of the inner bag 4 that correspond to the mouth 5, body 6, and bottom 7 of the container body 2 will be referred to as the mouth 5, body 6, and bottom 7 of the inner bag 4, respectively. The same applies to the outer shell 3.

If the mouth attachment member 8 is provided with a check valve, the inner bag 4 contracts as the contents of the inner bag 4 are dispensed. If the mouth attachment member 8 is not provided with a check valve, the inner bag 4 does not contract even after the contents of the inner bag 4 are dispensed, making it difficult to withdraw the inner bag 4 through the mouth 5 of the outer shell 3. The present invention facilitates withdrawal of the inner bag 4 through the mouth 5 of the outer shell by twisting the inner bag 4 to reduce its diameter, so the significance of applying this invention is particularly evident when the mouth attachment member 8 is not provided with a check valve. However, even when the mouth attachment member 8 is provided with a check valve, the inner bag 4 may not reduce in diameter appropriately when it contracts, so the significance of applying this invention is also evident when the mouth attachment member 8 is provided with a check valve.

An air inlet hole 16 is provided in the body 6 or bottom 7. The air inlet hole 16 is a through-hole that penetrates the outer shell 3, allowing air to be introduced into the intermediate space between the outer shell 3 and the inner bag 4. If the double container 1 is a so-called squeeze-type container that ejects the contents by compressing the outer shell 3, it is preferable to provide a check valve that controls the flow of air through the air inlet hole 16. The check valve is preferably configured to close the air inlet hole 16 when the outer shell 3 is compressed and to open the air inlet hole 16 when the compressive force is released. In this case, when a compressive force is applied to the outer shell 3, the compressive force is more easily applied to the inner bag 4, and after the contents are ejected, air is quickly introduced into the intermediate space, allowing the outer shell 3 to quickly restore its shape.

If a check valve is provided in the outside air inlet 16, it is preferable to place the outside air inlet 16 in a recess 6d provided in the body 6. In this case, it is possible to prevent the check valve from interfering with the shrink film when the body 6 is covered with the shrink film. It is also preferable to provide a groove 6e extending from the recess 6d toward the mouth 5. The groove 6e extends to a position that is not covered by the shrink film. This prevents the recess 6d from being sealed with the shrink film.

As shown in FIG. 2, the inner surface of at least one of the mouth portion 5 and the body portion 6 adjacent to the mouth portion 5 preferably has an uneven pattern 9 in which grooves 9a and ridges 9b alternate in the circumferential direction of the mouth portion 5. The uneven pattern 9 is provided on the inner surface of the inner bag 4. The number of grooves 9a is, for example, 4 to 30, and preferably 10 to 20. The grooves 9a and ridges 9b preferably extend non-parallel in the circumferential direction of the mouth portion 5. The direction in which the grooves 9a and ridges 9b extend is preferably 0 to 60 degrees, and preferably 0 to 30 degrees, relative to the axial direction of the mouth portion 5. Specific examples of this angle include 0, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, and 60 degrees, and may be within a range between any two of the values exemplified here. The uneven shape 9 may be provided only in the mouth 5, or may be provided in a position on the body 6 adjacent to the mouth 5, but is preferably provided across both the mouth 5 and the body 6. The uneven shape 9 may be formed by reducing the thickness of the recesses 9a or by increasing the thickness of the protrusions 9b compared to other parts of the mouth 5 of the inner bag 4, or by reducing the thickness of the recesses 9a and increasing the thickness of the protrusions 9b.

Because the thickness of the ridges 9b is greater than the thickness of the recesses 9a, when the twist applied by the mouth 5 is transmitted to the body 6, the force is more easily transmitted to the ridges 9b than to the recesses 9a, and the ridges 9b rotate faster than the recesses 9a. As a result, creases are formed in the inner bag 4 along the recesses 9a and their extensions, making it easier for the inner bag 4 to fold into pleats. For this reason, providing the recessed and raised surface 9 causes the body 6 to fold into pleats, thereby quickly reducing the diameter of the body 6. It is preferable not to provide a recessed or raised surface on the outer surface of the inner bag 4. If a recessed or raised surface is provided on the outer surface of the inner bag 4, the inner bag 4 and outer shell 3 will engage in the rotational direction of the inner bag 4, making it more difficult for the inner bag 4 to rotate relative to the outer shell 3.

Let T be the thickness of the inner bag 4 at the ridge 9b of the mouth 5 (the radius of the circumscribing circle of the inner bag 4 minus the radius of the inscribed circle passing through the apex of the ridge 9b), and let D be the depth of the recess 9a (the radius of the inscribed circle passing through the bottom of the recess 9a minus the radius of the inscribed circle passing through the apex of the ridge 9b). The maximum value of D/T is, for example, 0.2 to 0.8, with 0.3 to 0.5 being preferable. Specific examples of this value are 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, and 0.8, and may be within a range between any two of the values given here. The thickness of the inner bag 4 at the mouth portion 5 other than the uneven 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, or 2.0 mm, or may be within a range between any two of the numerical values exemplified here. The depth of the recessed ribs 9a at the portion where the depth is greatest 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, or 1.0 mm, or may be within a range between any two of the numerical values exemplified here.

The distance from the opening edge 5c of the mouth portion 5 to the upper end of the uneven shape 9 is, for example, 0 to 30 mm, specifically, for example, 0, 5, 10, 15, 20, 25, or 30 mm, or may be within a range between any two of the numerical values exemplified here. The distance from the upper end to the lower end of the uneven shape 9 is, for example, 10 to 40 mm, specifically, for example, 10, 15, 20, 25, 30, 35, or 40 mm, or may be within a range between any two of the numerical values exemplified here.

As shown in Figures 6 to 8, a protrusion 4e is provided on the bottom 7 of the inner bag 4. An annular protrusion 3b is provided on the bottom 7 of the outer shell 3, and a through-hole 3c is provided in the area inside the annular protrusion 3b. The protrusion 4e is inserted into the through-hole 3c, positioning the inner bag 4 relative to the outer shell 3. The annular protrusion 3b and its area are barely stretched during biaxial stretch blow molding, resulting in a large wall thickness for both the outer shell 3 and the inner bag 4.

If the outer diameter of the annular protrusion 3b is D1 and the inner diameter of the mouth 5 of the outer shell 3 is D2, then D1/D2 is preferably 0.9 or less. Because the thickness of the inner bag 4 is greater at the annular protrusion 3b and its inner region, the smaller D1/D2 is, the easier it is for the bottom 7 of the inner bag 4 to be reduced in diameter. D1/D2 is, for example, 0.1 to 0.9, and specifically may be, for example, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, or 0.9, or may be within a range between any two of the values exemplified here.

The bottom 7 of the container body 2 (i.e., the bottoms 7 of the inner bag 4 and outer shell 3) is provided with a bottom recessed region 7a and a peripheral region 7b surrounding the bottom recessed region 7a. The bottom recessed region 7a is a region of the bottom 7 recessed toward the inside of the container body 2. The peripheral region 7b forms the contact surface of the container body 2. As shown in FIG. 6A, at the peripheral surface 7a1 of the bottom recessed region 7a, the thickness of the inner bag 4 and outer shell 3 gradually decreases toward the peripheral region 7b. The peripheral surface 7a1 is an inclined surface that slopes away from the center of the bottom 7 toward the peripheral region 7b. In other words, the peripheral surface 7a1 forms part of a cone that tapers toward the bottom surface 7a2 of the bottom recessed region 7a. The bottom surface 7a2 of the bottom recessed region 7a is approximately flat. As a result, the bottom recessed region 7a has a substantially truncated cone shape.

The bottom surface 7a2 of the bottom recessed region 7a is difficult to stretch during biaxial stretch blow molding and is prone to becoming thicker. Therefore, the smaller the diameter D3 of the bottom surface 7a2 (in other words, the diameter of the area surrounded by the boundary line between the bottom surface 7a2 and the peripheral surface 7a1), the easier it is for the bottom 7 of the inner bag 4 to be reduced in diameter. D3/D2 is preferably 0.9 or less. D3/D2 is, for example, 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, or 0.9, and may be within a range between any two of the values exemplified here.

As shown in Figures 6 to 8, the bottom portion 7 of the inner bag 4 has an alternating thickness shape 10 in which thin portions 10a and thick portions 10b that are thicker than the thin portions 10a alternate in the circumferential direction of the inner bag 4. By providing the bottom portion 7 with the alternating thickness shape 10, when the inner bag 4 is twisted, the thin portions 10a bend, causing the bottom portion 7 to deform like an accordion, making it easier for the diameter of the bottom portion 7 to be reduced.

As shown in Figure 6C, the peripheral surface 7a1 is thicker than the side surface 4d of the inner bag 4 near the bottom 7. Therefore, providing the alternating thickness shape 10 on the peripheral surface 7a1 is particularly important for making it easier to reduce the diameter of the bottom 7. Furthermore, the peripheral region 7b is less likely to deform than the side surface 4d of the inner bag 4 near the bottom 7. Therefore, providing the alternating thickness shape 10 on the peripheral region 7b is particularly important. Therefore, it is preferable to provide the alternating thickness shape 10 on at least one of the peripheral surface 7a1 and the peripheral region 7b of the bottom recessed region 7a, and it is even more preferable to provide it so that it straddles the peripheral surface 7a1 and the peripheral region 7b. It is also preferable to provide it so that it straddles the peripheral region 7b and the side surface 4d of the inner bag 4. By providing the alternating thickness shape 10 in this manner, the bottom 7 is even easier to reduce in diameter.

As shown in Figure 7B, the thin-walled portions 10a and thick-walled portions 10b are preferably arranged to extend radially from the center of the bottom portion 7. The number of thin-walled portions 10a is, for example, 4 to 30, and preferably 10 to 20.

The thin-walled portion 10a can be formed by providing grooves 11 on either or both of the inner and outer surfaces of the inner bag 4. The grooves 11 on the inner surface of the inner bag 4 and the grooves 11 on the outer surface face each other. The area between two adjacent grooves 11 forms the thick-walled portion 10b.

In a cross section perpendicular to the height direction of the inner bag 4 (such as the cross section in Figure 6C), if the thickness of the inner bag 4 at the thin-walled portion 10a is T1 and the thickness of the inner bag 4 at the thick-walled 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 obtained when the cross section is moved along the height direction of the inner bag 4 and T1/T2 is calculated at each height position. The smaller the T1/T2 ratio, the thinner the thin-walled portion 10a is compared to the thick-walled portion 10b, making the bottom portion 7 more likely to deform like an accordion. This value is preferably 0.1 or greater. If this value is too small, the thickness at the thin-walled portion 10a will be too small, making pinholes more likely to occur. This value is, for example, 0.1 to 0.8, and specifically may be, for example, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, or 0.8, or may be within a range between any two of the values exemplified here.

The mouth attachment member 8 is preferably configured to be attachable to the mouth 5, and is configured so that the inner bag 4 rotates in conjunction with rotation of the mouth attachment member 8 (here, relative rotation with respect to the outer shell 3). With this configuration, the inner bag 4 can be twisted by rotating the mouth attachment member 8. Because the body 6 of the container body 2 has a larger outer diameter than the mouth 5, it is not easy to pull the inner bag 4 through the mouth 5 of the outer shell 3 simply by pulling on it. However, by twisting the inner bag 4 and reducing the diameter of the body 6 of the inner bag 4, the body 6 of the inner bag 4 can more easily pass through the mouth 5 of the outer shell 3, making it easier to pull the inner bag 4 out of the outer shell 3.

The engagement structure between the mouth attachment member 8 and the inner bag 4 is explained in more detail below.

As shown in Figures 2 and 3, the inner bag 4 has a protruding portion 4c that protrudes from the open end 3a of the outer shell 3. The protruding portion 4c has a protruding tube 4c1, an engaging protrusion 4c2, an engaging flange 4c3, and an abutting flange 4c4.

The engagement protrusion 4c2 protrudes radially outward from the circumferential surface of the protruding tube 4c1. The engagement flange 4c3 is an annular portion located farther from the opening end 3a than the engagement protrusion 4c2 and having a larger diameter than the protruding tube 4c1. The abutment flange 4c4 is an annular portion located in a position abutting the opening end 3a and having a larger diameter than the protruding tube 4c1. The abutment flange 4c4 abuts against the opening end 3a, preventing the inner bag 4 from falling into the outer shell 3. Alternatively, the abutment flange 4c4 may be omitted and the engagement protrusion 4c2 may be abutted against the opening end 3a to prevent the inner bag 4 from falling into the outer shell 3.

As shown in Figures 3 to 5, the mouth-attached member 8 includes an outer tube 8a, an intermediate tube 8b, an inner tube 8c, an engaging portion 8d, a claw portion 8e, a top plate 8f, and a nozzle 8g.

An engagement portion 8d is provided on the inner surface of the outer tube 8a. The engagement portion 8d engages with the engagement portion 5a of the mouth portion 5, and the mouth-attached member 8 is attached to the mouth portion 5 by engaging the engagement portion 8d with the engagement portion 5a.

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

Claws 8e are provided on the inner surface of the intermediate cylinder 8b. Multiple claws 8e (eight in this embodiment) are provided and spaced apart circumferentially. The number of claws 8e is, for example, 1 to 20, and preferably 4 to 12. Each claw 8e has an upper surface 8e1 and a lower inclined surface 8e2. A through hole 8h is provided in the top plate 8f at a position opposite the claw 8e.

A mouth attachment member 8 of this shape can be manufactured using a split mold that opens and closes vertically. The through-hole 8h and upper surface 8e1 can be formed using protrusions on the upper mold, allowing the claw portion 8e to be formed without forcibly removing the lower mold. Therefore, the protrusion amount of the claw portion 8e does not need to be set to an amount that allows for forcible removal, and can be set to an amount that is suitable for engagement with the inner bag 4 (e.g., 1 mm or more).

In this embodiment, the engaging portion 5a is a male thread and the engaging portion 8d is a female thread. Therefore, the mouth attachment member 8 can be attached to the mouth portion 5 by rotating the mouth attachment member 8 relative to the mouth portion 5 in the tightening direction (typically clockwise when viewed from above). (Hereinafter, relative rotation with respect to the mouth portion 5 will also be simply referred to as "rotation"). When the mouth attachment member 8 is rotated in the tightening direction, the engaging portion 8d threads into the engaging portion 5a, while the claw portion 8e gradually approaches the protruding portion 4c. At some point, the lower inclined surface 8e2 abuts the engaging flange 4c3. In this state, when the mouth attachment member 8 is further rotated in the tightening direction, the claw portion 8e overcomes the engaging flange 4c3, resulting in the state shown in Figure 5. In this state, the claw portion 8e is positioned 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 Figure 5B, the protruding tube 4c1 is positioned between the claw portion 8e and the inner tube 8c. If the threads of the engaging portion 5a and the engaging portion 8d are not fully tightened at this point, the claw portion 8e will be guided by the circumferentially inclined surface 4c5 on the engaging protrusion 4c2 and will climb over the engaging protrusion 4c2, allowing the mouth attachment member 8 to further rotate in the tightening direction. Once the threads of the engaging portion 5a and the engaging portion 8d are fully tightened, the mouth attachment member 8 will no longer be able to rotate in the tightening direction and will no longer be able to move axially around the mouth 5.

In this state, the engaging protrusion 4c2 engages with the claw portion 8e of the mouth attachment member 8 in the rotational direction of the mouth attachment member 8, and the engaging flange 4c3 engages with the claw portion 8e of the mouth attachment member 8 in the axial direction of the mouth portion 5. In other words, the claw portion 8e engages with the engaging protrusion 4c2 and the engaging flange 4c3.

For this reason, when the contents of the inner bag 4 are used up, the opening attachment member 8 is rotated in the loosening direction (usually counterclockwise when viewed from above), and the inner bag 4 rotates in conjunction with the rotation of the opening attachment member 8. This causes the inner bag 4 to twist and shrink in diameter.

When the mouth attachment member 8 is further rotated in the loosening direction to release the engagement between the engagement portion 8d and engagement portion 5a, the mouth attachment member 8 becomes movable in the direction away from the open end 3a (i.e., in the axial direction of the mouth 5). Because the engagement flange 4c3 engages with the mouth attachment member 8 in the axial direction of the mouth 5, moving the mouth attachment member 8 in the axial direction of the mouth 5 also moves the inner bag 4 together with the mouth attachment member 8, and the inner bag 4 is pulled out of the outer shell 3.

As described above, with the configuration of this embodiment, simply by rotating the mouth attachment member 8 in the loosening direction, the inner bag 4 is twisted and reduced in diameter, and then pulled out from the outer shell 3, making it possible to smoothly separate the inner bag 4 and outer shell 3 with a simple operation.

2. Manufacturing Method of the Double Container 1 As shown in Figures 9 to 11, the container body 2 can be formed by heating and biaxially stretching blow molding a preform 15 formed by covering an inner preform 14 that will become the inner bag 4 with an outer preform 13 that will become the outer shell 3.

As shown in Figure 9, the inner preform 14 is cylindrical and has a bottom, a mouth 14a, a body 14b, and a bottom 14c. A protrusion 14d is provided at the open end of the mouth 14a. The protrusion 14d does not deform during molding and remains in its original shape to become the protrusion 4c. Therefore, the matters described regarding the protrusion 4c also apply to the protrusion 14d. The bottom 14c is provided so as to close the lower end of the body 14b. A positioning pin 14c1 is provided on the bottom 14c.

As shown in Figure 10, the inner surface of the inner preform 14 has an uneven shape 19. The uneven shape 19 remains as is or is stretched during molding to become the uneven shape 9 of the container body 2. The explanation regarding the uneven shape 9 also applies to the uneven shape 19, unless it contradicts the intent of the explanation.

As shown in Figures 9 and 10, an alternating thickness shape 20 is provided near the bottom 14c of the inner preform 14, in which thin-walled sections 20a and thick-walled sections 20b that are thicker than the thin-walled sections 20a alternate in the circumferential direction. The alternating thickness shape 20 is stretched during biaxial stretch blow molding to form the alternating thickness shape 10. The number of thin-walled sections 20a is, for example, 4 to 30, and preferably 10 to 20. The thin-walled sections 20a are preferably provided in the longitudinal direction of the inner preform 14.

The thin-walled portion 20a can be formed by providing grooves 21 on either or both the inner and outer surfaces of the inner preform 14. If grooves 21 are provided on the inner surface of the inner preform 14, grooves 11 will be formed on the inner surface of the inner bag 4 after molding. If grooves 21 are provided on the outer surface of the inner preform 14, grooves 11 will be formed on the outer surface of the inner bag 4 after molding, and grooves 11 will also be formed on the inner surface of the inner bag 4 at positions opposite the grooves 11 on the outer surface. This is because the air pressure during blowing presses the resin opposite the grooves 11 outward.

In a cross section perpendicular to the height direction of the inner preform 14 (such as the cross section in Figure 10D), if the thickness of the inner bag 4 at the thin-walled portion 20a is t1 and the 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 when t1/t2 is calculated at each height position by moving the cross section along the height direction of the inner preform 14. 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 greater. This value is, for example, 0.1 to 0.8, and specifically, for example, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, or 0.8, and may be within a range between any two of the values exemplified here.

As shown in Figure 9, the outer preform 13 is cylindrical and has a bottom, a mouth 13a, a body 13b, and a bottom 13c. The bottom 13c is arranged to close the lower end of the body 13b. The bottom 13c is provided with an annular protrusion 13d and a positioning hole (not shown).

As shown in Figure 11, when forming the preform 15, the protrusion 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. This positions the inner preform 14 and the outer preform 13 relative to each other. In this state, the mouth portion 14a faces the mouth portion 13a, and the body portion 14b faces the body portion 13b.

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 primarily stretched during biaxial stretch blow molding. However, because biaxial stretch blow molding is performed while the annular convex portion 13d is supported, the annular convex portion 13d and its inner region are hardly stretched during biaxial stretch blow molding. The annular convex portion 13d becomes the annular convex portion 3b after molding.

The inner preform 14 and outer preform 13 can be formed by direct blow molding, injection molding, or other methods using thermoplastic resins such as polyester (e.g., PET) or polyolefin (e.g., polypropylene, polyethylene). The inner preform is preferably made of a material with a greater molding shrinkage rate than the outer preform. In this case, molding shrinkage forms a gap between the outer shell 3 and inner bag 4, making it easier to introduce outside air into the intermediate space between the outer shell 3 and inner bag 4.

In one example, the inner preform 14 is made of polyolefin (e.g., polypropylene), and the outer preform 13 is made of PET. Polyolefin has a greater molding shrinkage rate than PET, so using this type of resin configuration makes it easier for a gap to form between the outer shell 3 and the inner bag 4. In addition, using different materials for the inner preform 14 and outer preform 13 prevents them from welding to each other during blow molding.

The inner preform 14 is preferably formed by direct blow molding. Direct blow molding (blow molding using a molten cylindrical parison) makes it easy to form the inner preform 14 with a laminated structure. The outer preform 13 is preferably formed by injection molding.

After the preform 15 is biaxially stretched and blow-molded, the container body 2 shown in Figure 1 can be obtained by forming an outside air inlet hole 16 in the outer shell 3. After that, the inner bag 4 is filled with contents, and the mouth attachment member 8 is attached to the mouth 5 to obtain the double container 1.

3. Other Embodiments In the above embodiment, the outside air introduction holes 16 are formed after biaxially stretch blow molding, but through holes that serve as outside air introduction holes may be formed in the outer preform 13 in advance.
The outside air introduction hole 16 may be formed in the bottom of the outer shell 3 .
In the present invention, the structure for twisting the inner bag 4 is not particularly limited, and the inner bag 4 does not have to be configured to rotate in conjunction with the rotation of the opening attachment member 8. In this case, for example, the inner bag 4 may be rotated by pinching it with fingers. Therefore, a cap or pump that does not have a structure for engaging with the inner bag 4 may be used as the opening attachment member 8. Furthermore, the container body 2 does not need to have the protrusion 4c. For example, instead of the protrusion 4c, a flange may be provided at the open end of the inner bag 4, and this flange may be abutted against the open end of the outer shell 3, thereby preventing the inner bag 4 from falling out into the outer shell 3.
In the above embodiment, the alternating thickness shapes 10, 20 are realized by forming the recessed ribs 11, 21, but the alternating thickness shapes 10, 20 may also be formed by forming protruding ribs to form thick portions on one or both of the inner and outer surfaces of the inner bag 4 or the inner preform 14. Even in this case, the thin portions are selectively bent as the inner bag 4 twists, so that the bottom 7 is easily deformed into an accordion-like shape and reduced in diameter.
The annular protrusions 3b and 13d may be omitted.

1: Double container 2: Container body 3: Outer shell 3a: Opening end 3b: Annular convex portion 3c: Through hole 4: Inner bag 4c: Projecting portion 4c1: Projecting tube 4c2: Engaging projection 4c3: Engaging flange 4c4: Contact flange 4c5: Circumferential inclined surface 4d: Side surface 4e: Projection 5: Mouth 5a: Engaging portion 5b : Flange 5c : Open end 6 : Body part 6b : Shoulder part 6c : Body part main body 6d : Recessed part 6e : Groove 7 : Bottom part 7a : Bottom recessed area 7a1 : Peripheral surface 7a2 : Bottom surface 7b : Peripheral area 8 : Mouth attachment member 8a : Outer cylinder 8b : Intermediate cylinder 8c : Inner cylinder 8d : Engagement part 8e : Claw part 8e1 : Upper surface 8e2 : Lower inclined surface 8f : Top plate 8g : Nozzle 8h : Through hole 9 : Uneven shape 9a : Concave strip 9b : Convex strip 10 : Alternating thickness shape 10a : Thin wall portion 10b : Thick wall portion 11 : Concave strip 13 : Outer preform 13a : Mouth portion 13b : Body portion 13c : Bottom portion 13d : Annular convex portion 14 : Inner preform 14a : Mouth portion 14b : Body portion 14c : Bottom portion 14c1 : Positioning pin 14d : Protrusion 15 : Preform 15a : Mouth portion 15b : Body portion 15c : Bottom portion 16 : Outside air introduction hole 19 : Uneven shape 20 : Alternating thickness shape 20a : Thin wall portion 20b : Thick wall portion 21 : Concave strip

Claims (7)

A double container comprising a container body,
the container body includes a mouth, a body, and a bottom, the mouth being a cylindrical portion having an open end, the body being disposed adjacent to the mouth on a side farther from the open end than the mouth, and having a larger outer diameter than the mouth, and the bottom being configured to close the lower end of the body,
The container body includes an inner bag and an outer shell disposed to cover the inner bag,
The bottom of the inner bag is provided with an alternating thickness shape in which thin portions and thick portions that are thicker than the thin portions appear alternately in the circumferential direction ,
The double container is configured so that the inner bag is twisted to reduce its diameter and then pulled out from the outer shell,
The thin-walled portion is formed by providing a groove on one or both of the inner surface and the outer surface of the inner bag . The double container according to claim 1,
The thin-walled portion is formed by providing grooves on both the inner and outer surfaces of the inner bag. The double container according to claim 1 or claim 2,
Further provided with a mouth attachment member,
The double container, wherein the mouth attachment member is configured to be attachable to the mouth and the inner bag is configured to rotate in accordance with rotation of the mouth attachment member. The double container according to any one of claims 1 to 3 ,
The bottom of the inner bag is provided with a bottom recessed area and a peripheral area surrounding the bottom recessed area,
The double container, wherein the alternating thickness shape is provided on at least one of the peripheral surface of the bottom recessed region and the peripheral region. The double container according to claim 4 ,
The double container, wherein the alternating thickness shape is provided across the peripheral surface and the peripheral region. The double container according to claim 4 or claim 5 ,
The double-walled container, wherein the alternating thickness shape is provided so as to span the peripheral region and the side surface of the inner bag. The double container according to any one of claims 1 to 6 ,
A double-walled container in which the thickness of the inner bag at the thin-walled portion in a cross section perpendicular to the height direction of the inner bag is T1 and the thickness of the inner bag at the thick-walled portion is T2, and the minimum value of T1/T2 is 0.8 or less.