Double container and method for manufacturing same

Abstract

Provided is a double container that makes it possible to mitigate force required for pulling out an inner bag.　According to the present invention, a double container comprising a container body is provided. The container body comprises an inner bag and an outer shell disposed in a manner covering the inner bag. The inner bag is configured to be able to be pulled out from the container body, the outer shell comprises a flange part, and the container body comprises a mouth part, a trunk part, and a bottom part. The mouth part comprises an upper mouth section and a lower mouth section. The upper mouth section is a portion between the opening end of the container body and the lower surface of the flange part, and the lower mouth section is a portion between the upper mouth section and the trunk part. A portion where the outer diameter of the container body starts to expand at the lower side from the lower surface of the flange part is the origin of the lower mouth section. The bottom part is a portion that closes the lower end of the trunk part. The outer shell comprises an inner tapered part configured such that the inner diameter of the outer shell decreases toward the origin in at least a portion of the lower mouth section.

Description

Double container and its manufacturing method

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

[0002] Patent document 1 discloses a double container that is configured such that a mouth attachment member that is circumferentially engaged with the inner bag is rotated relative to the outer shell, thereby rotating the inner bag relative to the outer shell, thereby twisting the inner bag and reducing its diameter, and then the mouth attachment member is pulled so that the inner bag can be pulled out of the container body.

[0003] JP 2024-018821 A

[0004] (First Aspect) If a large force is required to pull the inner bag out of the container body, it becomes difficult to separate the inner bag from the container body, so it is desirable that the force required for this pulling out be small.

[0005] The present invention has been made in view of the above circumstances, and aims to provide a double-layered container that can reduce the force required to pull out the inner bag.

[0006] (Second aspect) However, when a mouth attachment member is attached to a protruding portion of the inner bag that protrudes from the opening end of the outer shell, as in Patent Document 1, if the rigidity of the protruding portion is insufficient, the protruding portion may be twisted by the rotational force applied to the mouth attachment member, making it difficult to transmit the rotational force to the portion of the inner bag that is contained within the outer shell, and making it difficult to twist the inner bag.

[0007] The present invention has been made in view of the above circumstances, and aims to provide a double-layered container in which the inner bag can be easily twisted, and a method for manufacturing the same.

[0008] (Third Viewpoint) In the double-walled container of Patent Document 1, the engagement protrusions of the inner bag and the engagement protrusions of the outer shell are engaged to prevent the inner bag from accidentally rotating relative to the outer shell. In Patent Document 1, the inner bag has engagement protrusions formed on the cam protrusions, and when the inner bag is formed using an inner preform formed by direct blow molding, the engagement protrusions of the inner bag are likely to be thin. If the engagement protrusions of the inner bag are thin, they are likely to break, causing problems such as leakage of the contents.

[0009] The present invention has been made in consideration of these circumstances, and provides a double container that can prevent the inner bag from being damaged while also preventing the inner bag from accidentally rotating relative to the outer shell.

[0010] (Fourth aspect) In the configuration of Patent Document 1, the mouth attachment member is attached to the protruding portion of the inner bag and not to the outer shell, so when the mouth attachment member is grasped, it is prone to rattle against the outer shell.

[0011] If the spout attachment member rattles relative to the outer shell, the double container will feel uncomfortable when in use, so it is desirable to suppress rattle of the spout attachment member relative to the outer shell.

[0012] The present invention has been made in view of the above circumstances, and provides a double container that can suppress rattle of the mouth attachment member relative to the outer shell.

[0013] (First Aspect) According to the present invention, the following inventions are provided: [1] A double-layered container comprising a container body, the container body comprising an inner bag and an outer shell arranged to cover the inner bag, the inner bag configured to be removable from the container body, the outer shell comprising a flange, the container body comprising a mouth, a body, and a bottom, the mouth comprising an upper mouth and a lower mouth, the upper mouth being a portion between the open end of the container body and the underside of the flange, the lower mouth being a portion between the upper mouth and the body, the portion below the underside of the flange where the outer diameter of the container body begins to expand being the base of the lower mouth, the bottom being a portion that closes the lower end of the body, the double-layered container comprising an inner tapered portion in at least a part of the lower mouth configured so that the inner diameter of the outer shell narrows towards the base. [2] The double container according to [1], wherein the outer shell has an outer tapered portion in at least a portion of the lower opening, where the outer diameter of the outer shell narrows toward the base. [3] The double container according to [2], wherein, where L and Lo are the lengths of the lower opening and the outer tapered portion, respectively, in the axial direction of the opening of the container body, Lo / L is 0.50 to 1.0. [4] The double container according to any one of [1] to [3], wherein, where L and Li are the lengths of the lower opening and the inner tapered portion, respectively, in the axial direction of the opening of the container body, Li / L is 0.50 to 1.0. [5] The double container according to any one of [1] to [4], wherein, where L and La are the lengths of the lower opening and the opening, respectively, in the axial direction of the opening of the container body, L / La is 0.25 or more. [6] A preform used in biaxially stretched blow molding, the preform being constructed by placing an outer preform over an inner preform, the outer preform having a flange portion, and the outer preform having an inner tapered portion at an adjacent portion adjacent to the bottom surface of the outer preform, closer to the bottom side of the flange portion than the bottom surface of the outer preform, configured so that the inner diameter of the outer preform narrows toward the bottom of the outer preform.[7] The preform according to [6], wherein the outer preform has an outer tapered portion in the adjacent region, configured so that the outer diameter of the outer preform decreases toward the bottom of the outer preform. [8] The method for manufacturing a double-walled container according to any one of [1] to [5], comprising a biaxial stretch molding process for biaxially stretching a preform, wherein the preform is configured by placing the outer preform over the inner preform, the outer preform having a flange portion, and the outer preform has an inner tapered portion in an adjacent region adjacent to the bottom of the outer preform and closer to the bottom of the outer preform than the underside of the flange portion, configured so that the inner diameter of the outer preform decreases toward the bottom of the outer preform. [9] The method according to [8], wherein the outer preform has an outer tapered portion in the adjacent region, configured so that the outer diameter of the outer preform decreases toward the bottom of the outer preform.

[10] The method according to [8] or [9], wherein Lp is the length of the lower opening in the axial direction of the mouth of the container body, and Lp is the length of a portion of the lower opening whose outer surface shape does not change from the shape of the preform before and after the biaxial stretch molding process, and Lp / L is 0.50 to 1.00.

[0014] (Second Aspect) According to the present invention, the following inventions are provided: [1] A double container comprising a container body and a spout attachment member, wherein the container body comprises an inner bag and an outer shell arranged to cover the inner bag, the spout attachment member is attached to a protruding portion of the inner bag that protrudes from the open end of the outer shell, the spout attachment member is circumferentially engaged with the protruding portion, the inner bag has a recess in a portion facing the outer shell, and the recess is formed by being recessed so that the inner bag protrudes inward at the recess. [2] The double container according to [1], wherein the inner bag comprises a first tube disposed within the outer shell and a second tube having a larger outer diameter than the first tube and disposed closer to the open end of the inner bag than the first tube, the second tube having a peripheral wall and a lower wall disposed below the peripheral wall and configured to narrow the diameter of the peripheral wall toward the first tube, the inner bag is disposed so that the lower surface of the second tube abuts against the outer shell, and the recess is disposed at a corner between the lower wall and the peripheral wall. [3] The double container according to [2], wherein the corner is disposed within the outer shell. [4] The double container according to any one of [1] to [3], wherein the inner bag comprises a ridge on its outer peripheral surface that protrudes radially outward, the ridge being disposed adjacent to the recess and closer to the bottom than the recess. [5] A double-walled container according to any one of [1] to [4], wherein the inner bag has a convex ridge on its outer surface that protrudes radially outward, the recess includes a first small recess, a second small recess that is spaced apart from the first small recess in the circumferential direction of the inner bag, and a reinforcing rib between the first and second small recesses, the reinforcing rib being configured so that the inner bag protrudes outward beyond the first and second small recesses, and the reinforcing rib is located at a position adjacent to the opening end of the inner bag relative to the convex ridge.[6] A double container comprising a container body, the container body comprising an inner bag and an outer shell arranged to cover the inner bag, the inner bag comprising a convex rib protruding radially outward on its outer peripheral surface, the outer shell comprising a concave rib, the convex rib and the concave rib being engageable by relative rotation of the inner bag and the outer shell in one direction, and disengageable by relative rotation of the inner bag and the outer shell in the other direction, the outer shell comprising an engaging convex portion protruding radially inward on its inner peripheral surface, the convex rib having a one-side abutment surface that abuts against the engaging convex portion when the inner bag is rotated relative to the outer shell in the one direction, the inner bag comprising a movement suppressing portion protruding radially outward on its outer peripheral surface, the movement suppressing portion preventing the one-side abutment surface from moving further in the one direction beyond the end of the concave rib when the inner bag is rotated relative to the outer shell in the one direction, and the outer shell including a suppressing abutment surface that can abut against the movement suppressing portion when the inner bag is rotated relative to the outer shell in the one direction. [7] A double container as described in [6], wherein the convex rib has a second abutment surface that abuts the engaging convex portion when rotated relative to the other direction, the inner bag has a protrusion on its outer surface that protrudes radially outward, the protrusion is positioned at a position farther from the convex rib than the engaging convex portion when the convex rib is engaged with the concave rib, and the movement suppression portion is provided at a position adjacent to the opening end side of the inner bag than the protrusion.[8] A preform formed by covering an outer preform with an inner preform, wherein the inner preform has a convex rib on its outer peripheral surface that protrudes radially outward, and the outer preform has a concave rib, wherein the convex rib and the concave rib can be engaged by relative rotation of the inner preform and the outer preform in one direction and can be disengaged by relative rotation of the inner preform and the outer preform in the other direction, the inner preform has a concave portion at a position facing the outer preform, the concave portion is formed by being recessed so that the inner preform protrudes inward at the concave portion, the concave portion includes a first small concave portion, a second small concave portion spaced apart from the first small concave portion in the circumferential direction of the inner preform, and a reinforcing rib between the first and second small concave portions, wherein the reinforcing rib is configured so that the inner preform protrudes outward further than the first and second small concave portions, and the reinforcing rib is provided at a position adjacent to the open end side of the inner preform relative to the convex rib. [9] A preform formed by covering an outer preform with an inner preform, wherein the inner preform has a convex rib that protrudes radially outward on its outer peripheral surface, and the outer preform has a concave rib, and the convex rib and the concave rib can be engaged by relative rotation of the inner preform and the outer preform in one direction, and can be disengaged by relative rotation of the inner preform and the outer preform in the other direction, the outer preform has an engaging convex portion that protrudes radially inward on its inner peripheral surface, and the convex rib has a one-side abutment surface that abuts against the engaging convex portion when the inner preform is rotated relative to the outer preform in the one direction, and the inner preform has a movement suppressing portion that protrudes radially outward on its outer peripheral surface, and the movement suppressing portion prevents the one-side abutment surface from moving further in the one direction beyond the end of the concave rib when the outer preform and the inner preform are rotated relative to the outer preform in the one direction, and the outer preform includes a suppressing abutment surface that can abut against the movement suppressing portion when the outer preform is rotated relative to the outer preform in the one direction.

[10] The preform according to [9], wherein the ridge has an other-side abutment surface that abuts against the engaging protrusion when the outer preform and the inner preform are rotated relative to each other in the other direction, the inner preform has a protrusion on its outer peripheral surface that protrudes radially outward, the protrusion is disposed at a position farther from the ridge than the engaging protrusion when the ridge is engaged with the recess, and the movement suppressing portion is disposed at a position adjacent to the open end side of the inner preform than the protrusion.

[11] The method for manufacturing a double container according to any one of [1] to [7], wherein the container body of the double container is manufactured by biaxial stretch blow molding.

[0015] (Third Aspect) According to the present invention, the following inventions are provided: [1] A double container comprising a container body, the container body comprising an inner bag and an outer shell arranged to cover the inner bag, the inner bag comprising a convex rib protruding radially outward on its outer peripheral surface, the outer shell comprising a concave rib, the convex rib and the concave rib are configured to be engageable by relative rotation of the inner bag and the outer shell in one direction and to be disengageable by relative rotation of the inner bag and the outer shell in the other direction, the outer shell comprising an engaging convex portion protruding radially inward on its inner peripheral surface, the convex rib having a first other-side abutment surface that abuts on the engaging convex portion during relative rotation in the other direction, the first other-side abutment surface being an end face located at a longitudinal end of the convex rib or a side face of a concave portion provided in the convex rib. [2] The double container according to [1], wherein the first other-side abutment surface has a first other-side inclination angle, which is an inclination angle with respect to a tangent to the outer peripheral surface at a base of the first other-side abutment surface, of 5 to 45 degrees. [3] The double container according to [2], wherein the ridge has a first one-side abutment surface that abuts on the engaging protrusion when the ridge is rotated relatively in one direction, the first one-side abutment surface is an end face located at an end of the ridge in the longitudinal direction, and the first one-side inclination angle, which is an inclination angle with respect to a tangent to the outer peripheral surface at a base of the first one-side abutment surface, is greater than the first other-side inclination angle. [4] A double container described in any one of [1] to [3], wherein the engaging convex portion has a second one-side abutment surface that abuts against the convex rib when rotated relative to the one direction, and a second other-side abutment surface that abuts against the convex rib when rotated relative to the other direction, and the second one-side inclination angle, which is the inclination angle of the second one-side abutment surface with respect to the connecting line connecting the base of the second one-side abutment surface and the base of the second other-side abutment surface, is smaller than the second other-side inclination angle, which is the inclination angle of the second other-side abutment surface with respect to the connecting line. [5] A double container according to any one of [1] to [4], wherein the convex rib has a first one-side abutment surface that abuts the engaging convex portion when rotated relative to the one direction, the first one-side abutment surface is an end surface located at the longitudinal end of the convex rib, and the central surface between the first one-side abutment surface and the first other-side abutment surface has a shape similar to the portion of the outer shell that faces the central surface.[6] The double container according to [5], wherein the central surface is not provided with a protrusion protruding from the central surface. [7] The double container according to any one of [1] to [6], wherein the ridge is hollow. [8] The double container according to any one of [1] to [7], wherein a cam rail is provided on the inner peripheral surface of the outer shell, the recess is provided at the end of the cam rail, the lower surface of the ridge and the upper surface of the cam rail are inclined so as to approach the open end as they progress counterclockwise or clockwise when viewed from the open end side of the container body, and when the inner bag and the outer shell are rotated relative to each other in the other direction, the cam mechanism formed by the ridge and the cam rail acts to move the inner bag in a direction to come out of the container body. [9] The double-walled container according to [8], wherein the inner bag has a protrusion on its outer peripheral surface that protrudes radially outward, the protrusion being positioned farther from the ridge than the engaging protrusion when the ridge is engaged with the recess, and the protrusion is arranged to overlap the cam rail in the axial direction, which is the direction in which the central axis of the mouth of the container body extends.

[10] The double-walled container according to any one of [1] to [9], wherein the container body is manufactured by biaxial stretch blow molding.

[0016] (Fourth Aspect) According to the present invention, the following inventions are provided. [1] A double container comprising a container body and a spout attachment member, wherein the container body comprises an inner bag and an outer shell arranged to cover the inner bag, the spout attachment member is attached to a protrusion of the inner bag that protrudes from the open end of the outer shell, the inner bag and the outer shell abut at abutting surfaces on the inner bag side and the outer shell side, and the abutting surface on the outer shell side is inclined to face inward of the outer shell. [2] The double container according to [1], wherein the inner bag comprises a first tube arranged within the outer shell and a second tube having an outer diameter larger than that of the first tube and arranged closer to the open end of the inner bag than the first tube, the second tube comprising a peripheral wall and a bottom wall provided below the peripheral wall and configured to narrow the diameter of the peripheral wall toward the first tube, and the abutting surface on the inner bag side is the bottom surface of the second tube. [3] The double container according to [2], wherein the lower wall is disposed within the outer shell. [4] The double container according to any one of [1] to [3], wherein the inner bag has a convex rib on its outer surface, and the outer shell has a concave rib on its inner peripheral surface, the convex rib and the concave rib are configured to be engageable by relative rotation of the inner bag and the outer shell in one direction and to be disengageable by relative rotation of the inner bag and the outer shell in the other direction, and when the convex rib and the concave rib are engaged, the abutting surface of the inner bag is pressed against the abutting surface of the outer shell. [5] A double container as described in [4], wherein a cam rail is provided on the inner surface of the outer shell, the recessed ribs are provided at the end of the cam rail, and the lower surface of the convex rib and the upper surface of the cam rail are inclined so as to approach the opening end as they proceed counterclockwise or clockwise when viewed from the opening end side of the container body, and when the inner bag and the outer shell are rotated relative to each other in the other direction, the action of the cam mechanism formed by the convex rib and the cam rail causes the inner bag to move in the direction of coming out of the container body.

[0017] (First Aspect) The inventors discovered that the force required to separate the inner bag increases when the thickness of the inner bag is large at the height where the undercut portion, which forms when the inner bag is pulled out of the container body, begins. They then discovered that by providing the outer shell with an inner tapered portion configured so that the inner diameter of the outer shell narrows toward the base of the lower opening, the thickness of the undercut portion can be reduced, thereby reducing the force required to pull out the inner bag, leading to the completion of the present invention. (Second Aspect) In the double-walled container of the present invention, the inner bag has a recess in a portion facing the outer shell. This recess is recessed so that the inner bag protrudes inward, and therefore functions as a rib to reinforce the protruding portion. This makes it easier for rotational force applied to the opening attachment member to be transmitted to the portion of the inner bag contained within the outer shell, making it easier to twist the inner bag.

[0018] (Third Aspect) In the double-walled container of the present invention, instead of providing a separate engaging protrusion on the rib, the end faces at the longitudinal ends of the rib abut against the engaging protrusion on the outer shell, thereby preventing the inner bag from accidentally rotating relative to the outer shell. Since the end faces of the rib are less likely to be thin compared to the engaging protrusion in Patent Document 1, according to the present invention, the occurrence of breakage of the inner bag is reduced.

[0019] (Fourth aspect) In the double container of the present invention, the contact surface on the outer shell side is inclined so as to face the inside of the outer shell, so that the protruding portion of the inner bag is easily positioned by the contact surface on the outer shell side, and rattling of the mouth attachment member relative to the outer shell is suppressed.

[0020]

[0033] FIG. 1 is a perspective view of a double container 1 according to a first embodiment of the present invention. The dashed-dotted lines in the figure represent boundary lines where the curvature of the surfaces constituting the surface shape changes. This also applies to other figures. This is an exploded perspective view of the double container 1 of FIG. 1. FIGS. 3A and 3B are a plan view and a front view, respectively, of the container body 2 of FIG. 2. FIG. 4A is a longitudinal cross-sectional view of the double container 1 of FIG. 1 with the overcap 42 closed. FIG. 4B is an enlarged view of region B in FIG. 4A. FIG. 4A is an exploded view of region A in FIG. 5 with the overcap 42 slightly open. FIG. 6A is an enlarged view of region A in FIG. 5. FIG. 6B is a view corresponding to FIG. 6A of the reference example. FIG. 8A is an exploded view of the container body 2 of FIG. 5. FIG. 8B is an enlarged view of region B in FIG. 8A. FIG. 10A is a cross-sectional view of region C in FIG. 5. FIG. 10B is an enlarged view of region B in FIG. 10A. FIG. 10C is an enlarged view of region C in FIG. 10B. 17 is an exploded perspective view of the container body 2 in FIG. 2 . A front view of the inner bag 4. A perspective view showing a state in which the inner preform 14 and the outer preform 13 are separated. A perspective view of a preform 15 formed by covering the inner preform 14 with the outer preform 13. A front view showing a state in which the inner preform 14 is supported by a pair of rails 45. A vertical cross-sectional view of the preform 15. A cross-sectional view showing a state in which the preform 15 is attached to the blow core 21 and brought close to the heater 32. A cross-sectional view showing a state after the preform 15 has been transferred to the molding die 23 from the state in FIG. 17 . A cross-sectional view showing a state after the bottom support die 22 supports the bottom 15c of the preform 15 from the state in FIG. 18 . A cross-sectional view showing a state after the stretch rod 25 has been extended and the bottom support die 22 has been retracted from the state in FIG. 19 , thereby first axially stretching the preform 15. A front view of the inner bag 4 of the double container 1 of the second embodiment of the present invention. A perspective view corresponding to FIG. 11 of the double container 1 of the third embodiment of the present invention. 12 is a front view of the double container 1 of Fig. 22. FIG. 23 is a cross-sectional view of the double container 1 in a state in which the ridges 4g of the inner bag 4 and the recesses 3m of the outer shell 3 are engaged, taken along a line A-A in Fig. 23. FIG. 24 is a perspective view of the double container 1 of a fourth embodiment of the present invention, taken along a line A-A in Fig. 11.Figure 26A is a front view of the double container 1 of Figure 25, corresponding to Figure 12. Figure 26B is a cross-sectional view of the double container 1 in a state in which the ridges 4g and recesses 3m of the inner bag 4 are engaged, taken at a section corresponding to section D-D in Figure 26A. It is a plan view of the inner bag 4 shown in Figure 25. It is a perspective view of the preform 15 used in manufacturing the double container 1 shown in Figure 25, taken at a section corresponding to Figure 11. It is a cross-sectional view of the preform 15 in a state in which the ridges 14g and recesses 13m of the inner preform 14 are engaged, taken at a section corresponding to Figure 26B.

[0021] The following describes embodiments of the present invention. The various features described in the following embodiments can be combined with each other. Each feature constitutes an invention independently. Elements in the following embodiments that are not defined in the claims are optional and can be omitted. Numerical values ​​disclosed in the following description may have any number of "0"s (e.g., one or two) added to the end. For example, "1.4" may have one or two "0"s added to the end to make it "1.40" or "1.400." Furthermore, when drawings with subnumbers (e.g., Figures 1A and 1B) are included, a reference to the drawing without the subnumber (e.g., Figure 1) refers to all drawings with the subnumbers (e.g., Figures 1A and 1B in the above example).

[0022] The embodiments shown below include at least the inventions of the following aspects. The first and third embodiments relate to the invention of the second aspect [1] and the inventions of the first, third, and fourth aspects, the second embodiment relates to the inventions of the first, third, and fourth aspects, and the fourth embodiment relates to the inventions of the first to fourth aspects.

[0023] 1. First Embodiment A double-sided container 1 according to a first embodiment of the present invention will be described using Figures 1 to 20. In the following description, terms related to directions, such as "upper" and "lower," refer to directions when the bottom 7 is in contact with the ground. Furthermore, in the following description, the "axial direction" refers to the direction in which the central axis C (shown in Figure 2) of the mouth 5 extends, e.g., the direction in which the inner bag 4 is pulled out of the container body 2. The "circumferential direction" refers to the direction of rotation about the central axis C of the mouth 5, e.g., the direction in which the inner bag 4 is rotated at the mouth 5 relative to the outer shell 3. Unless otherwise specified, "clockwise" and "counterclockwise" refer to directions as viewed from the top of the double-sided container 1.

[0024] 1. Structure of double container 1 As shown in Fig. 1, the double container 1 of the first embodiment of the present invention comprises a container body 2 and a spout attachment member 8. Each component will be described in detail below.

[0025] <Configuration of Container Body 2> As shown in FIGS. 2 and 3, the container body 2 includes a mouth 5, a body 6, and a bottom 7. The mouth 5 is a tubular (preferably cylindrical) portion having an opening end 5c. The opening end 5c is the opening end of the container body 2 and also the opening end of the inner bag 4 shown in FIG. 5. The mouth 5 includes an engagement portion 4m to which a mouth attachment member 8 can be attached. The engagement portion 4m is provided on the protruding portion 4c of the inner bag 4. As shown in FIGS. 11 and 12, the mouth 5 includes an axial engagement portion 4ma that axially engages with the mouth attachment member 8, and a circumferential engagement portion 4mb that circumferentially engages with the mouth attachment member 8. The axial engagement portion 4ma and the circumferential engagement portion 4mb are provided to protrude radially outward from the peripheral wall 4b1. As shown in FIG. 8, a recess 4c13 is provided on the inner peripheral surface of the axial engagement portion 4ma. It is preferable that the mouth attachment member 8 does not engage with the outer shell 3.

[0026] The body 6 is disposed adjacent to the mouth 5 on a side farther from the open end 5c than the mouth 5. The body 6 has a larger outer diameter (in this specification, "outer diameter" means the circular equivalent diameter when the cross section is not circular) than the mouth 5. The body 6 is cylindrical, and the bottom 7 is provided 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. The body 6 also has a body main body 6c on the bottom 7 side of the shoulder 6b. The body main body 6c has a shape in which the outer diameter is approximately constant toward the bottom 7, or a shape in which the diameter decreases toward the bottom 7, for example.

[0027] As shown in Figure 3, the mouth 5 has an upper mouth 5a and a lower mouth 5b. The upper mouth 5a is the portion between the open end 5c of the container body 2 and the lower surface 5d1 of the flange 5d. The lower mouth 5b is the portion between the upper mouth 5a and the body 6. The base 5b1 of the lower mouth 5b is the portion below the lower surface 5d1 of the flange 5d where the outer diameter of the container body 2 begins to expand.

[0028] The shoulder 6b has an uneven shape 6d in which concave and convex ribs 6d1 and ribs 6d2 are alternately arranged in the circumferential direction. The convex ribs 6d2 extend at an inclination counterclockwise from the boundary 6e between the shoulder 6b and the body main body 6c toward the base 5b1 of the mouth 5. The extending direction of the convex ribs 6d2 coincides with the direction in which the inner bag 4 is rotated when the inner bag 4 is pulled out of the container main body 2. In other words, in this embodiment, as will be described later, the inner bag 4 is rotated counterclockwise when the inner bag 4 is pulled out, so the convex ribs 6d2 are also provided so as to incline counterclockwise. By providing the uneven shape 6d on the shoulder 6b, the inner bag 4 is more likely to be folded regularly when rotated relative to the outer shell 3, making it easier to reduce the diameter of the inner bag 4.

[0029] The outer surface of the base 5b1 preferably has a curved shape that convexly extends inward. The radius of curvature is preferably 3 mm or greater. Setting this radius of curvature to such a value prevents the base 5b1 from getting caught on the outer shell 3 when the inner bag 4 is pulled out. The radius of curvature is, for example, 3 to 10 mm, preferably 3 to 7 mm, and specifically, for example, 3, 4, 5, 6, 7, 8, 9, or 10 mm, and may be within a range between any two of the values ​​exemplified here.

[0030] The trunk main body 6c is provided with a pair of grooved ribs 6f1, 6f2. The grooved ribs 6f1, 6f2 extend in the circumferential direction and are spaced apart from each other in the direction of the central axis C. The provision of the grooved ribs 6f1, 6f2 increases the rigidity of the trunk main body 6c.

[0031] As shown in Figures 4 to 8, the container body 2 includes an inner bag 4 and an outer shell 3 disposed to cover the inner bag 4. As shown in Figure 5, the inner bag 4 includes a protruding portion 4c protruding from the open end 3a of the outer shell 3. The mouth attachment member 8 is attached to the protruding portion 4c. The inner bag 4 has an inner bag body 4d housed within the outer shell 3, excluding the protruding portion 4c. The inner bag 4 is configured to be removable from the container body 2. In the following description, the portions of the inner bag 4 corresponding 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.

[0032] <Details of mouth portion 5 of inner bag 4> As shown in Figures 8, 11 and 12, the inner bag 4 includes a first tube 4a and a second tube 4b. The first tube 4a is disposed within the outer shell 3. The second tube 4b has a larger outer diameter than the first tube 4a and is disposed closer to the open end 5c of the inner bag 4 than the first tube 4a. The entire second tube 4b may be disposed outside the outer shell 3, or part or all of the second tube 4b may be disposed within the outer shell 3, with the remainder disposed outside the outer shell 3.

[0033] As shown in Figures 8 and 12, the second tube 4b includes a peripheral wall 4b1 and a lower wall 4b2 disposed below the peripheral wall 4b1 and configured to reduce the diameter of the peripheral wall 4b1 toward the first tube 4a. The inner bag 4 is disposed so that the lower surface 4b4 of the second tube 4b abuts against the outer shell 3. The abutment of the lower surface 4b4 against the outer shell 3 prevents the inner bag 4 from entering the outer shell 3. The peripheral wall 4b1 preferably extends parallel to the axial direction. The lower wall 4b2 is preferably disposed within the outer shell 3.

[0034] The angle α of the peripheral wall 4b1 relative to the bottom wall 4b2 is preferably 90 degrees or greater, and more preferably 95 degrees or greater. In this case, the bending of the inner bag 4 at the corner 4b3 between the bottom wall 4b2 and the peripheral wall 4b1 is relatively gentle, making it less likely to crack when an impact is applied, thereby improving impact resistance. This angle is, for example, 90 to 135 degrees (105 degrees in this embodiment), preferably 95 to 115 degrees, and specifically, for example, 90, 95, 100, 105, 110, 115, 120, 125, 130, or 135 degrees, or may be in a range between any two of the values ​​exemplified here.

[0035] The length L1 between the lower surface 4b4 at the corner 4b3 and the lower surface 4m3 of the axial engagement portion 4ma is preferably 2 mm or more. In this case, local bending of the inner bag 4 is further suppressed. The length L1 is, for example, 2 to 10 mm, and preferably 3 to 6 mm (4.5 mm in this embodiment). Specific examples of the length L1 include 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0, 7.5, 8.0, 8.5, 9.0, 9.5, and 10.0 mm, and may be in a range between any two of the values ​​exemplified here. The length of the peripheral wall 4b1 from the lower surface 4b4 at the portion parallel to the axial direction is preferably within the above-mentioned numerical range, and the portion between the lower surface 4b4 and the lower surface 4m3 is preferably parallel to the axial direction.

[0036] As shown in Figures 4, 9, and 11-12, the inner bag 4 has a recess 4h in a portion facing the outer shell 3. The recess 4h is recessed so that the inner bag 4 protrudes inward at the recess 4h. When the spout attachment member 8 is attached to the protrusion 4c as in this embodiment, if the protrusion 4c is not sufficiently rigid, the rotational force applied to the spout attachment member 8 may twist the protrusion 4c, making it difficult to transmit the rotational force to the portion of the inner bag 4 housed within the outer shell 3 and making it difficult to twist the inner bag 4. In the configuration of this embodiment, the recess 4h functions as a rib that reinforces the protrusion 4c. This makes it easier to transmit the rotational force applied to the spout attachment member 8 to the portion of the inner bag 4 housed within the outer shell 3, making it easier to twist the inner bag 4.

[0037] Furthermore, in the double-walled container 1 of this embodiment, before attaching the mouth attachment member 8, a leak test for the inner bag 4 may be performed by sucking air out of the inner bag 4 through the mouth 5 to shrink the inner bag 4. During this test, air must be introduced into the intermediate space between the inner bag 4 and the outer shell 3 to prevent the outer shell 3 from shrinking along with the inner bag 4. If the outer shell 3 does not have an air inlet hole for introducing air into the intermediate space, as in this embodiment, deformation of the mouth 5 of the inner bag 4 may form a gap between the inner bag 4 and the outer shell 3 at the mouth 5, allowing air to be introduced into the intermediate space. Such deformation of the mouth 5 of the inner bag 4 is undesirable because it can lead to defects. In this embodiment, the inner bag 4 has a recess 4h at a location facing the outer shell 3. Air can be introduced into the intermediate space between the inner bag 4 and the outer shell 3 through the recess 4h, thereby suppressing deformation of the mouth 5 of the inner bag 4.

[0038] In this embodiment, the recess 4h is provided at the corner 4b3 between the bottom wall 4b2 and the peripheral wall 4b1. In this case, the recess 4h functions as a reinforcing rib, increasing the rigidity of the second tube 4b, making it easier to rotate the inner bag 4 relative to the outer shell 3 when pulling out the inner bag 4. The corner 4b3 is also located inside the outer shell 3. In this case, a gap is unlikely to form between the inner bag 4 and the outer shell 3, so the provision of the recess 4h, which makes it easier for air to be introduced into the intermediate space between the inner bag 4 and the outer shell 3, is of significant technical significance.

[0039] <Details of the Mouth Portion 5 of the Outer Shell 3> As shown in FIG. 4 , the open end 3a of the outer shell 3 is provided with a base surface 3a1, an annular protrusion 3a2, and an inner bag support surface 3a3. The base surface 3a1 is preferably annular. The annular protrusion 3a2 is disposed inside the base surface 3a1 and protrudes axially from the base surface 3a1. As shown in FIG. 4 , the base surface 3a1 faces the open end 41a1 of the outer tube 41a of the mouth-attaching member 8, and the annular protrusion 3a2 protrudes toward the inside of the outer tube 41a of the mouth-attaching member 8. With this configuration, even if foreign matter, such as the contents of the inner bag 4, enters the gap 44 between the base surface 3a1 and the open end 41a1, the annular protrusion 3a2 prevents the foreign matter from penetrating between the inner bag 4 and the outer shell 3. Furthermore, it is preferable that the apex 3a4 of the annular protrusion 3a2 be higher than the open end 41a1. In this case, the penetration of the contents is further prevented.

[0040] As shown in FIG. 8 , the inner bag support surface 3a3 is the surface against which the lower surface 4b4 of the second tube 4b abuts. The inner bag support surface 3a3 is preferably annular. The lower surface 4b4 abuts against the inner bag support surface 3a3, thereby supporting the inner bag 4 on the outer shell 3 and preventing the inner bag 4 from penetrating into the outer shell 3. The inner bag support surface 3a3 is disposed inside the base surface 3a1 and the annular protrusion 3a2. The inner bag support surface 3a3 is preferably located lower than the base surface 3a1. In this case, a portion of the peripheral wall 4b1 near the lower wall 4b2 is covered by the outer shell 3, which inevitably covers the lower wall 4b2 and the corners 4b3 as well. This protects the corners 4b3, which have relatively low impact resistance, with the outer shell 3, further improving the impact resistance of the inner bag 4.

[0041] As shown in Figure 7, the outer peripheral surface of the outer shell 3 is provided with an expanded diameter portion 3o and a flange portion 5d, in that order from the opening end 3a of the outer shell 3. The expanded diameter portion 3o is formed by expanding the diameter of the opening end 3a. A recess 3g is preferably provided on the inner peripheral surface of the expanded diameter portion 3o. The lower surface of the recess 3g serves as the inner bag support surface 3a3.

[0042] <Details of the Tapered Portion> The double-walled container 1 of this embodiment is designed to have the inner bag 4 pulled out of the container body 2. If the force required for this pulling is excessive, it becomes difficult to pull the inner bag 4 out of the container body 2. Therefore, it is desirable to reduce the force required to pull out the inner bag 4 (the force required to twist the inner bag 4 when twisting the inner bag 4 while pulling it out). Research into reducing this force was conducted and found that during biaxial stretch blow molding, the thickness of the lower opening 5b of the outer shell 3 decreases toward the base 5b1, resulting in the formation of an undercut portion 4u that becomes an undercut when the inner bag is pulled out of the container body. The undercut portion 4u is located closer to the outer shell 3 than the vertical line v shown in Figures 6A and 6B. The greater the thickness of the inner bag 4 at height position H, where the undercut portion 4u begins, the greater the force required to pull out the inner bag 4.

[0043] In the reference example shown in Figure 6B, which does not have an inner tapered portion 3p, the height position H where the undercut portion 4u starts is close to the underside 5d1 of the flange 5d. At this height position, the thickness of the inner bag 4 is relatively large, so a relatively large force is required to pull out the inner bag 4. On the other hand, in the present embodiment shown in Figure 6A, the outer shell 3 is provided with an inner tapered portion 3p in at least a portion of the lower opening 5b, which is configured so that the inner diameter of the outer shell 3 decreases toward the base 5b1 of the lower opening 5b. Therefore, the height position H where the undercut portion 4u starts moves in a direction closer to the base 5b1. Because the thickness of the inner bag 4 decreases toward the base 5b1, the provision of the inner tapered portion 3p reduces the force required to pull out the inner bag 4.

[0044] The outer shell 3 preferably has an outer tapered portion 3q in at least a part of the lower opening 5b, the outer diameter of the outer shell 3 narrowing toward the base 5b1. In this case, the inner tapered portion 3p is more likely to be formed.

[0045] If the lengths of the lower opening 5b, the inner tapered portion 3p, and the outer tapered portion 3q in the axial direction of the mouth 5 of the container body 2 are L, Li, and Lo, respectively, then Li / L and Lo / L are preferably each 0.50 to 1.00 (in this embodiment, both are 1.00). In this case, the torque required to pull out the inner bag 4 is more effectively reduced. Li / L and Lo / L are each preferably 0.75 to 1.00, and specific examples of these values ​​are 0.50, 0.55, 0.60, 0.65, 0.70, 0.75, 0.80, 0.85, 0.90, 0.95, and 1.00, and may be within a range between any two of the values ​​exemplified here.

[0046] The inner tapered portion 3p has an angle η1 at its maximum relative to the central axis C of, for example, 1 to 20 degrees (4 degrees in this embodiment), and preferably 1 to 10 degrees. Specific examples of this angle η1 are 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, and 20 degrees, and may be in a range between any two of the values ​​exemplified here. The outer tapered portion 3q has an angle η2 at its maximum relative to the central axis C of, for example, 2 to 25 degrees (7 degrees in this embodiment), and preferably 4 to 12 degrees. Specifically, the angle η2 is, for example, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, or 25 degrees, or may be in a range between any two of the values ​​exemplified here. The angle η2 is preferably larger than the angle η1, and the value of (angle η2 - angle η1) is, for example, 1 to 10 degrees, or may be, for example, 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 degrees, or may be in a range between any two of the values ​​exemplified here.

[0047] 3, where La is the length of the mouth 5 of the container body 2 in the axial direction of the mouth 5, L / La is preferably 0.25 or greater (0.36 in this embodiment). The greater the proportion of the lower opening 5b in the mouth 5, the more likely it is that the pull-out force of the inner bag 4 will increase. Therefore, the greater L / La, the more significant the technical significance of applying the present invention. L / La is, for example, 0.25 to 0.60, and specifically, for example, 0.25, 0.30, 0.35, 0.40, 0.45, 0.50, 0.55, or 0.60, and may be in a range between any two of the values ​​exemplified here. L is, for example, 5 to 20 mm (9.7 mm in this embodiment), preferably 8 to 15 mm, and specifically, for example, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 mm, and may be in a range between any two of the numerical values ​​exemplified here. La is, for example, 15 to 50 mm (26.8 mm in this embodiment), preferably 20 to 40 mm, and specifically, for example, 15, 20, 25, 30, 35, 40, 45, or 50 mm, and may be in a range between any two of the numerical values ​​exemplified here.

[0048] 8, the inner bag 4 and the outer shell 3 abut against each other at a contact surface 4i on the inner bag 4 side and a contact surface 3i on the outer shell 3 side. In this embodiment, the lower surface 4b4 of the inner bag 4 abuts against the inner bag support surface 3a3 of the outer shell 3, so that the lower surface 4b4 is the abutment surface 4i and the inner bag support surface 3a3 is the abutment surface 3i.

[0049] The abutment surface 3i (or the inner bag support surface 3a3) is preferably inclined toward the inside of the outer shell 3. In other words, the abutment surface 3i is inclined so as to approach the open end 3a as it extends radially outward. When the spout attachment member 8 is attached to the protruding portion 4c of the inner bag 4 but not to the outer shell 3, as in this embodiment, the spout attachment member 8 is likely to rattle relative to the outer shell 3 when gripped. If the spout attachment member 8 rattles relative to the outer shell 3, the usability of the double-walled container 1 will be adversely affected, so it is desirable to suppress rattle of the spout attachment member 8 relative to the outer shell 3. In this embodiment, the abutment surface 3i on the outer shell 3 side is inclined toward the inside of the outer shell 3, so that the protruding portion 4c of the inner bag 4 is easily positioned by the abutment surface 3i on the outer shell 3 side, and rattle of the spout attachment member 8 relative to the outer shell 3 is suppressed.

[0050] The angle β of the contact surface 3i relative to a reference plane P perpendicular to the central axis C of the mouth 5 is, for example, 5 to 45 degrees (15 degrees in this embodiment), preferably 10 to 30 degrees. Specifically, the angle β may be, for example, 5, 10, 15, 20, 25, 30, 35, 40, or 45 degrees, and may be within a range between any two of the values ​​exemplified here. The contact surfaces 4i and 3i are preferably parallel. When the contact surfaces 4i and 3i are inclined relative to the reference plane P and parallel to each other, the contact area tends to be larger than when the contact surfaces 4i and 3i are parallel to the reference plane P, making it less likely that a gap will form between the inner bag 4 and the outer shell 3. Therefore, the technical significance of providing a recess 4h in the inner bag 4 to ensure an air flow path is significant.

[0051] 10 to 12, a ridge 4g that protrudes radially outward is provided on the outer peripheral surface 4j of the inner bag 4 (more specifically, the inner bag body 4d). As shown in Fig. 12, the lower surface of the ridge 4g is inclined so as to approach the open end 5c as it progresses in the counterclockwise direction.

[0052] As shown in Figure 10, multiple ridges 4g are provided on the outer peripheral surface 4j of the inner bag 4, and the multiple ridges 4g are arranged circumferentially offset from one another. In this embodiment, two ridges 4g are arranged circumferentially offset by 180 degrees. The angle at which each ridge 4g extends is preferably 180 degrees or less, and more preferably 90 degrees or less. This angle is, for example, 15 to 180 degrees, and preferably 30 to 90 degrees (approximately 45 degrees in this embodiment). Specifically, this angle may be, for example, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 105, 110, 115, 120, 125, 130, 135, 140, 145, 150, 155, 160, 165, 170, 175, or 180 degrees, or may be in a range between any two of the values ​​exemplified here.

[0053] As shown in Fig. 12, the ridges 4g are arranged adjacent to the recesses 4h and closer to the bottom than the recesses 4h (i.e., below the recesses 4h). As shown in Figs. 3 and 5, the ridges 4g are arranged at the mouth 5 (preferably the upper mouth 5a). As will be described later, the inner bag 4 is formed by biaxially stretching blow molding the inner preform 14. In biaxially stretching blow molding, the portion above the lower surface 5d1 of the flange 5d is hardly deformed, so as shown in Fig. 15, the inner preform 14 is provided with recesses 14h and ridges 14g corresponding to the recesses 4h and ridges 4g. During mass production, for example, the inner preforms 14 are transported in an aligned state by supporting the portion 14b2 corresponding to the lower wall 4b2 on each of a pair of rails 45 of the part feeder, but the portion of the portion 14b2 that is circumferentially aligned with the recess 14h or the ridge 14g is difficult to support with the rail 45, so if the circumferential positions of the recess 14h and the ridge 14g are misaligned, the portion of the portion 14b2 that is easy to support with the rail 45 becomes narrower, making it difficult to transport the inner preforms 14 stably with the part feeder. On the other hand, in this embodiment, the ridge 4g is positioned adjacent to the recess 4h, so the circumferential positions of the recess 14h and the ridge 14g are aligned, making it easy to transport the inner preforms 14 stably with the part feeder.

[0054] As shown in FIG. 11 , the inner peripheral surface of the outer shell 3 is provided with a recess 3m that can engage with the ridge 4g. The recess 3m is preferably provided at the end of the cam rail 3l. The upper surface of the cam rail 3l is inclined so as to approach the opening end 3a as it progresses counterclockwise. The ridge 4g and the recess 3m are configured to be engageable by relative rotation of the inner bag 4 and the outer shell 3 in one direction, and to be disengageable by relative rotation of the inner bag 4 and the outer shell 3 in the other direction. With the ridge 4g and the recess 3m engaged, it is preferable that the contact surface 4i of the inner bag 4 be pressed against the contact surface 3i of the outer shell 3, as shown in FIG. 8 . In this case, rattle of the mouth attachment member 8 relative to the outer shell 3 is further suppressed.

[0055] A plurality of cam rails 3l are provided on the inner peripheral surface of the outer shell 3, and the plurality of cam rails 3l are offset from one another in the circumferential direction. In this embodiment, two cam rails 3l are arranged offset by 180 degrees in the circumferential direction. The angle at which each cam rail 3l extends is preferably 360 degrees or less, and more preferably 270 degrees or less. This angle is, for example, 90 to 360 degrees, and preferably 120 to 240 degrees (180 degrees in this embodiment). Specifically, this angle may be, for example, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 210, 220, 230, 240, 250, 260, 270, 280, 290, 300, 310, 320, 330, 340, 350, or 360 degrees, or may be in a range between any two of the values ​​exemplified here.

[0056] The recessed strip 3m is preferably provided on each cam rail 31. The angle at which the recessed strip 3m extends is the same as the angle at which the protruding strip 4g extends.

[0057] Before the inner bag 4 is pulled out of the container body 2, the lower surface of the ridge 4g abuts against the upper surface of the cam rail 3l within the groove 3m. The ridge 4g and the cam rail 3l form a cam mechanism 31. When the inner bag 4 is rotated counterclockwise relative to the outer shell 3, the cam mechanism 31 causes the inner bag 4 to be displaced in a direction that allows it to come out of the container body 2. At this time, the inner bag 4 is twisted and its diameter is reduced. The cam mechanism 31 has an inclined structure that is inclined in the same direction as a right-handed screw.

[0058] <Details of Rotation Restriction Structure> The container body 2 is preferably provided with a rotation restriction structure that restricts relative rotation between the inner bag 4 and the outer shell 3. Examples of this rotation restriction structure include a structure that increases the frictional force between the inner bag 4 and the outer shell 3, and a structure that engages the inner bag 4 and the outer shell 3 in a concave-convex manner in the circumferential direction. In this embodiment, as shown in Figures 10 and 11, the outer shell 3 has an engaging protrusion 3j on its inner circumferential surface 3n that protrudes radially inward. The engaging protrusion 3j is preferably arranged along the cam rail 3l, and more preferably arranged within or adjacent to the recessed groove 3m.

[0059] As shown in FIG. 10 , the ridge 4g includes a first abutment surface 4g1 that abuts against the engaging protrusion 3j when the ridge 4g is rotated relative to the engaging protrusion 3j in one direction (i.e., the engaging direction), a second abutment surface 4g2 that abuts against the engaging protrusion 3j when the ridge 4g is rotated relative to the engaging protrusion 3j in the other direction (i.e., the disengaging direction), and a central surface 4g3 between the first abutment surface 4g1 and the second abutment surface 4g2. The first abutment surface 4g1 and the second abutment surface 4g2 are end surfaces located at the longitudinal ends of the ridge 4g. The central surface 4g3 has a shape similar to that of the portion 3r of the outer shell 3 that the central surface 4g3 faces. No protrusion is provided on the central surface 4g3. At the central surface 4g3, the ridge 4g protrudes a constant height from the outer peripheral surface 4j. The height of the ridge 4g decreases monotonically from the center in the longitudinal direction of the ridge 4g toward the bases 4g4 and 4g5 at both ends in the longitudinal direction of the ridge 4g.

[0060] In a configuration in which a separate protrusion is provided on the central surface 4g3 of the rib 4g and this protrusion abuts against the engaging protrusion 3j, the protrusion is likely to become thin during molding, resulting in breakage and leakage of the contents. In contrast, in this embodiment, instead of providing a separate protrusion on the central surface 4g3, the end faces at the longitudinal ends of the rib 4g abut against the engaging protrusion 3j of the outer shell, thereby preventing the inner bag 4 from unexpectedly rotating relative to the outer shell 3. Since the end faces of the rib 4g are less likely to become thin than when a separate protrusion is provided on the central surface 4g3, this embodiment prevents breakage of the inner bag 4. The rib 4g may be hollow or solid. However, when the rib 4g is hollow, the technical significance of abutting the end faces at the longitudinal ends of the rib 4g against the engaging protrusion 3j of the outer shell is significant. When the inner bag 4 is formed using an inner preform 14 formed by direct blow molding, the rib 4g is typically hollow.

[0061] The other-side contact surface 4g2 has a second-side inclination angle θ2, which is the inclination angle of the base 4g4 of the other-side contact surface 4g2 relative to the tangent 4j2 of the outer peripheral surface 4j, of 5 to 45 degrees (19 degrees in this embodiment), preferably 10 to 40 degrees. The outer peripheral surface 4j is preferably circular in cross section, and the portion extending from the circular outer peripheral surface 4j is preferably the rib 4g. The second-side inclination angle θ2 is preferably 10 to 30 degrees, specifically, for example, 5, 10, 15, 20, 25, 30, 35, 40, or 45 degrees, and may be in a range between any two of the values ​​exemplified here. The smaller the second-side inclination angle θ2, the less likely the rib 4g is to be thinned. Furthermore, if the second-side inclination angle θ2 is greater than 45 degrees, the rib 4g is too thinned, which may easily deform when the other-side contact surface 4g2 is pressed against the engaging protrusion 3j, resulting in insufficient restriction of relative rotation.

[0062] The one-side inclination angle θ1, which is the inclination angle of the one-side abutment surface 4g1 at the base 4g5 relative to the tangent 4j1 of the outer peripheral surface 4j, is greater than the other-side inclination angle θ2. In this case, the thickness of the one-side abutment surface 4g1 tends to be relatively thin, allowing for a reduction in the torque required for engagement between the rib projection 4g and the rib recess 3m. The one-side inclination angle θ1 is, for example, 50 to 80 degrees (64 degrees in this embodiment), preferably 55 to 75 degrees. Specifically, the one-side inclination angle θ1 may be, for example, 50, 55, 60, 65, 70, 75, or 80 degrees, or may be in a range between any two of the values ​​exemplified here. The difference between the one-side inclination angle θ1 and the other-side inclination angle θ2 is, for example, 30 to 60 degrees (44 degrees in this embodiment), preferably 35 to 55 degrees. Specifically, this difference may be, for example, 30, 35, 40, 45, 50, 55, or 60 degrees, or may be in a range between any two of the values ​​exemplified here.

[0063] The engaging protrusion 3j has a one-side contact surface 3j1 that contacts the protrusion 4g when the engaging protrusion 3j is rotated relative to the rib 4g in one direction (i.e., the engaging direction), and a second-side contact surface 3j2 that contacts the protrusion 4g when the engaging protrusion 3j is rotated relative to the rib 4g in the other direction (i.e., the disengaging direction). The one-side contact surface 3j1 contacts the one-side contact surface 4g1, and the other-side contact surface 3j2 contacts the other-side contact surface 4g2.

[0064] The one-side inclination angle δ1, which is the inclination angle of the one-side contact surface 3j1 with respect to the connecting line 3j6 connecting the base 3j5 of the one-side contact surface 3j1 and the base 3j4 of the other-side contact surface 3j2, is, for example, 20 to 50 degrees (31 degrees in this embodiment), preferably 25 to 45 degrees. Specifically, the one-side inclination angle δ1 is, for example, 20, 25, 30, 35, 40, 45, or 50 degrees, and may be in a range between any two of the values ​​exemplified here. The other-side inclination angle δ2, which is the inclination angle of the other-side contact surface 3j2 with respect to the connecting line 3j6, is 50 to 80 degrees (60 degrees in this embodiment), preferably 55 to 75 degrees. Specifically, the other-side inclination angle δ2 is, for example, 50, 55, 60, 65, 70, 75, or 80 degrees, and may be in a range between any two of the values ​​exemplified here. The engaging protrusions 3j are preferably solid bodies, and in this case, the larger the inclination angle, the greater the torque required for engagement or disengagement. In this embodiment, the one-side inclination angle δ1 is smaller than the other-side inclination angle δ2, so a configuration is realized in which the torque required for engagement between the protrusions 4g and the recesses 3m is relatively low, and the torque required for disengagement between the protrusions 4g and the recesses 3m is relatively high. The difference between the one-side inclination angle δ1 and the other-side inclination angle δ2 is, for example, 15 to 50 degrees (29 degrees in this embodiment), preferably 20 to 40 degrees. This difference may be, for example, 20, 25, 30, 35, 40, 45, or 50 degrees, or may be within a range between any two of the values ​​exemplified here.

[0065] 4 and 5, the mouth attachment member 8 preferably has a discharge port 8d for discharging the contents in the inner bag 4. In addition, the mouth attachment member 8 preferably includes a nozzle 8c.

[0066] The cap 8a preferably includes a cap body 41 and an overcap 42. The cap body 41 is configured to be able to engage with the protrusion 4c and includes a discharge port 8d. The overcap 42 is configured to be able to open and close the discharge port 8d. FIG. 4 shows a closed state in which the discharge port 8d is closed, and FIG. 5 shows an open state in which the discharge port 8d is open. In this embodiment, the cap body 41 and the overcap 42 are connected by a hinge 43, but they do not have to be connected. The overcap 42 is preferably able to engage with the cap body 41 by a screw or a snap fit.

[0067] The cap body 41 includes an outer tube 41a, an inner tube 41b, a nozzle 8c, and an upper wall 41d. The inner tube 41b is disposed inside the outer tube 41a. The outer tube 41a and inner tube 41b are connected via the upper wall 41d. The nozzle 8c is disposed above the upper wall 41d. A flow hole 41i is provided in the upper wall 41d, and the flow passages of the inner tube 41b and the nozzle 8c are connected through the flow hole 41i. The tip of the nozzle 8c forms the discharge port 8d. The inner tube 41b is inserted into the protruding portion 4c and is in close contact with the inner surface 4f1 of the cylindrical seal portion 4f. As a result, the inner tube 41b and the cylindrical seal portion 4f are frictionally engaged in the circumferential direction. An engagement portion 8b is provided on the inner peripheral surface of the outer tube 41a.

[0068] The overcap 42 comprises an outer tube 42a, an inner tube 42b, and an upper wall 42d. The inner tube 42b is disposed inside the outer tube 42a. The outer tube 42a and the inner tube 42b are connected via the upper wall 42d. The upper wall 42d does not have a discharge port for discharging the contents of the inner bag 4.

[0069] When the discharge port 8d is closed by the overcap 42, the inner tube 42b is inserted into the nozzle 8c of the cap body 41 and is in close contact with the inner surface of the nozzle 8c. The bottom surface of the outer tube 42a abuts against the upper wall 41d of the cap body 41. From this state, by gripping the outer tube 42a and applying an upward force to the overcap 42, the overcap 42 can be separated from the cap body 41 to open the discharge port 8d.

[0070] <Attaching the Mouth Attachment Member 8> As shown in Figure 5, the mouth attachment member 8 can be attached to the mouth 5 while supporting the enlarged diameter portion 3o or the flange portion 5d. The mouth attachment member 8 is preferably a plug-type member. With the enlarged diameter portion 3o or the flange portion 5d supported, the mouth attachment member 8 is placed over the protruding portion 4c. When a downward force is applied to the mouth attachment member 8 in this state, the engaging portion 8b overcomes the axial engaging portion 4ma and engages with the axial engaging portion 4ma and the circumferential engaging portion 4mb, thereby attaching the mouth attachment member 8 to the mouth 5. The engaging portion 8b axially engages with the axial engaging portion 4ma and circumferentially engages with the circumferential engaging portion 4mb. The circumferential engagement between the circumferential engaging portion 4mb and the engaging portion 8b may be a concave-convex engagement or a frictional engagement.

[0071] <Removal of inner bag 4> The mouth attachment member 8 is engaged with the protruding portion 4c of the inner bag 4 in the circumferential and axial directions, and is configured to rotate relative to the outer shell 3 so that the inner bag 4 twists as the mouth attachment member 8 rotates. The action of a cam mechanism 31 provided between the inner bag 4 and the outer shell 3 causes the inner bag 4 to move in a direction to come out of the container body 2 as the inner bag 4 rotates.

[0072] With this configuration, by rotating the mouth attachment member 8, the inner bag 4 can be twisted and moved in a direction that allows it to come out of the container body 2, and then by pulling the mouth attachment member 8, the inner bag 4 can be pulled out of the container body 2.

[0073] 1-2. Manufacturing Method of Double Container 1 The container body 2 can be manufactured by biaxially stretching blow molding the preform 15 shown in Fig. 14. The double container 1 can also be manufactured by attaching the mouth attachment member 8 to the container body 2.

[0074] <Configuration of Inner Preform 14 , Outer Preform 13 , and Preform 15 > The preform 15 includes the inner preform 14 that becomes the inner bag 4 and the outer preform 13 that becomes the outer shell 3 .

[0075] As shown in Figure 13, the inner preform 14 is cylindrical with a bottom, and includes a mouth 14a, a body 14b, and a bottom 14c. A protrusion 14d is provided on the mouth 14a. As shown in Figures 13 and 14, the protrusion 14d is a portion of the preform 15 that protrudes from the open end 13f of the outer preform 13. The protrusion 14d does not deform during molding, and becomes the protrusion 4c in its original shape. The protrusion 14d is provided with an engaging portion 14m that becomes the engaging portion 4m. The bottom 14c is provided so as to close the lower end of the body 14b.

[0076] The inner preform 14 also has a recess 14h at a location facing the outer preform 13. The recess 14h is preferably recessed so that the inner preform 14 protrudes inward at the recess 14h. The inner preform 14 has a ridge 14g on its outer circumferential surface 14j that protrudes radially outward. The ridge 14g is positioned adjacent to the recess 14h, closer to the bottom 14c than the recess 14h. With this configuration, as shown in Figure 15, the inner preform 14 can be supported by a pair of rails 45 of the parts feeder, facilitating stable transport.

[0077] 13, the outer preform 13 is cylindrical with a bottom and includes a mouth 13a, a body 13b, and a bottom 13c. The bottom 13c is provided to close the lower end of the body 13b.

[0078] 16 , the outer preform 13 has a flange portion 15e. The outer preform 13 has an inner tapered portion 13p in an adjacent region 13g adjacent to the bottom 13c of the outer preform 13 on the side closer to the bottom 13c of the outer preform 13 than the lower surface 15e1 of the flange portion 15e, configured so that the inner diameter of the outer preform 13 decreases toward the bottom 13c of the outer preform 13. The outer preform 13 also has an outer tapered portion 13q in the adjacent region 13g, configured so that the outer diameter of the outer preform 13 decreases toward the bottom 13c of the outer preform 13. In this case, the inner tapered portion 3p is formed in the outer shell 3, and the force required to pull out the inner bag 4 is likely to be reduced.

[0079] If the length of the adjacent portion 13g in the direction in which the central axis C1 of the mouth portion 13a of the outer preform 13 extends (hereinafter referred to as the "outer preform axial direction") is designated as pL, then pL is preferably the same as the length L of the lower mouth portion 5b. pL is the length in the outer preform axial direction, for example, of 5 to 20 mm (9.7 mm in this embodiment), preferably 8 to 15 mm, and specifically may be, for example, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 mm, and may be within a range between any two of the numerical values ​​exemplified here.

[0080] If the lengths of the inner tapered portion 13p and the outer tapered portion 13q in the axial direction of the outer preform are pLi and pLo, respectively, then pLi / pL and pLo / pL are preferably each 0.50 to 1.00. In this case, the torque required to pull out the inner bag 4 is more effectively reduced. pLi / pL and pLo / pL are each preferably 0.75 to 1.00, and specifically, for example, 0.50, 0.55, 0.60, 0.65, 0.70, 0.75, 0.80, 0.85, 0.90, 0.95, and 1.00, and may be in a range between any two of the values ​​exemplified here.

[0081] The angle ε1 of the inner tapered portion 13p at the portion of the adjacent portion 13g where the angle with respect to the central axis C1 is greatest is, for example, 2 to 30 degrees (13 degrees in this embodiment), and preferably 5 to 20 degrees. Specifically, this angle ε1 may be, for example, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, or 30 degrees, or may be in a range between any two of the values ​​exemplified here.

[0082] The outer tapered portion 13q has an angle ε2 at the adjacent portion 13g where the angle with respect to the central axis C1 is maximum, which is, for example, 2 to 25 degrees (7 degrees in this embodiment), and preferably 4 to 12 degrees. Specifically, this angle ε2 may be, for example, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, or 25 degrees, or may be in a range between any two of the values ​​exemplified here.

[0083] It is preferable that angle ε1 is larger than angle ε2, and the value of (angle ε1 - angle ε2) is, for example, 1 to 25 degrees, specifically, for example, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, and 25 degrees, and may be in a range between any two of the numerical values ​​exemplified here.

[0084] 14, a preform 15 can be formed by covering the inner preform 14 with the outer preform 13. In the preform 15, the mouth portion 14a faces the mouth portion 13a, and the body portion 14b faces the body portion 13b.

[0085] 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. In this embodiment, the portion of the flange portion 15e closer to the bottom portion 15c than the lower surface 15e1 is mainly stretched during biaxial stretch blow molding. The portion of the flange portion 15e closer to the opening end 15f than the lower surface 15e1 is hardly deformed during molding, and the outer surface shape of the adjacent portion 13g is also hardly deformed during biaxial stretch molding. With regard to the portion that is hardly deformed during biaxial stretch molding, the content described in relation to the container body 2 can also be applied to the preform 15, as long as it does not contradict the intent.

[0086] <Materials and Manufacturing Methods of the Inner Preform 14, the Outer Preform 13, and the Preform 15> The inner preform 14 and the outer preform 13 can be formed from a thermoplastic resin such as polyester (e.g., PET) or polyolefin (e.g., polypropylene, polyethylene). The outer preform 13 can be formed by direct blow molding or injection molding. The inner preform 14 is preferably formed by direct blow molding using a molten cylindrical parison. Direct blow molding has the advantage of easily achieving thinner walls and multi-layered structures compared to injection molding. A seal portion is formed on the bottom 14c of the inner preform 14 formed by direct blow molding, by welding the inner surfaces of the parison together. This seal portion has relatively low strength and is prone to tearing during biaxial stretch blow molding. Therefore, to increase the strength of the seal portion, the seal portion is preferably a protruding seal portion 14t that protrudes from the bottom 14c of the inner preform 14.

[0087] <Biaxially stretched blow molding process> The biaxially stretched blow molding process will be described using Figures 17 to 20. In the biaxially stretched blow molding process, the preform 15 is attached to the blow core 21 so that the insertion portion 21b of the blow core 21 is positioned within the preform 15, and the preform 15 is then biaxially stretched blow molded into the shape of the container body 2.

[0088] In one example, the biaxial stretch blow molding process includes a mounting step, a heating step, and a stretching step. Each step will be described below.

[0089] <Attachment Process> In the attachment process, as shown in Fig. 17 , the preform 15 is attached to the blow core 21 so that the insertion portion 21b of the blow core 21 is disposed within the preform 15. The blow core 21 includes a base portion 21a, an insertion portion 21b, and a through hole 21c. The insertion portion 21b is provided so as to protrude from the base portion 21a. The insertion portion 21b is inserted into the preform 15.

[0090] <Heating Process> The heating process can be performed using a heating device 35 shown in FIG. 17. In the heating process, the preform 15 is heated and softened to a softened state. In one example, the heating process can be performed by placing the preform 15 in close proximity to a heater 32 while the preform 15 is attached to a blow core 21, as shown in FIG. 17. The heating process is performed by covering the flange portion 15e of the preform 15 with a heat shield 33 and heating the portion of the flange portion 15e closer to the bottom 15c than the lower surface 15e1. This softens the heated portion. On the other hand, the portion of the flange portion 15e closer to the open end 15f than the lower surface 15e1 receives little or no heat from the heater 32 and is not softened. In one example, the preform 15 can be heated while being rotated. In one example, the heater 32 is composed of multiple rod-shaped heaters arranged along the side of the preform 15, but other configurations are also possible.

[0091] <Stretching Step> The stretching step can be performed using a blow molding device 36 shown in Figures 18 to 20. In the stretching step, the softened preform 15 is stretched to form the shape of the container body 2. In one example, the stretching step includes a first stretching step and a second stretching step.

[0092] <First Stretching Step> In the first stretching step, the preform 15 is stretched along a first axial direction (i.e., the vertical direction). The first axis is, for example, a direction parallel to the central axis C of the mouth portion 5, i.e., the vertical direction in FIG. 18. In one example, this step can be performed by setting the heated preform 15 in a molding die 23 as shown in FIGS. 18 and 19, and then, as shown in FIGS. 19 and 20, supporting the bottom 15c of the preform 15 with a bottom support die 22. A stretch rod 25 inserted through a through hole 21c in the blow core 21 is pressed against the inner bottom surface of the inner preform 14 to stretch it. At this time, it is preferable to retract the bottom support die 22 in synchronization with the extension of the stretch rod 25. This allows the preform 15 to be stably stretched.

[0093] The preform 15 can be transferred from the heating device 35 to the blow molding device 36 while being supported by the blow core 21. The molding die 23 is composed of a split mold that can be opened and closed, and includes a cavity surface 23a corresponding to the outer surface shape of the container body 2 and a flange abutment surface 23d against which the lower surface 15e1 of the flange portion 15e abuts. The first stretching step can be performed with the lower surface 15e1 of the flange portion 15e abutting against the flange abutment surface 23d.

[0094] <Second Stretching Step> In the second stretching step, air is blown into the inner preform 14 from the state shown in Fig. 20 to stretch (i.e., expand) the preform 15 in the second axial direction (i.e., the lateral direction) and shape it into the shape of the cavity surface 23a, thereby obtaining the container body 2 shown in Fig. 2. Air can be blown in through the through holes 21c provided in the blow core 21.

[0095] If the length of the portion of the lower opening 5b of the container body 2 whose outer surface shape does not change from the shape of the preform 15 before and after the biaxial stretch molding process is Lp, then Lp / L is preferably 0.50 to 1.00. By providing the outer preform 13 with an inner tapered portion 13p and / or an outer tapered portion 13q, it becomes easier to form the inner tapered portion 13p and / or the outer tapered portion 13q in the lower opening 5b of the container body 2. Lp / L is preferably 0.75 to 1.00, and specifically, for example, 0.50, 0.55, 0.60, 0.65, 0.70, 0.75, 0.80, 0.85, 0.90, 0.95, or 1.00, and may be within a range between any two of the numerical values ​​exemplified here.

[0096] In one example, by matching the shape of the portion 23e of the cavity surface 23a that faces the adjacent portion 13g to the shape of the adjacent portion 13g, the shape of the adjacent portion 13g can be matched to the shape of the lower opening portion 5b of the container body 2.

[0097] 2. Second Embodiment As shown in Figure 21, the second embodiment is the same as the first embodiment except that it does not include a recess 4h. This embodiment is suitable for use when a seal structure must be formed between the inner bag 4 and the outer shell 3 at the opening 5. In this embodiment, it is preferable to employ a configuration in which the abutment surfaces 4i and 3i are inclined and parallel to the reference plane P. In this case, the abutment area is likely to be larger than when the abutment surfaces 4i and 3i are parallel to the reference plane P, making it less likely that a gap will form between the inner bag 4 and the outer shell 3. This makes it possible to prevent air leakage through the gap between the inner bag 4 and the outer shell 3.

[0098] This embodiment is suitable for use when the double-walled container 1 is a so-called peelable container in which the inner bag 4 contracts as the contents are dispensed. In this case, the opening attachment member 8 is preferably provided with a discharge valve that prevents outside air from entering the inner bag 4 while allowing the contents to be dispensed from the inner bag 4. It is also preferable to provide an outside air inlet hole for introducing outside air into the intermediate space between the inner bag 4 and the outer shell 3, and to provide an outside air inlet valve in this outside air inlet hole that allows outside air to be introduced into the intermediate space while preventing outside air from being discharged from the intermediate space. This configuration makes it possible to realize a squeeze-type peelable container.

[0099] 3. Third Embodiment A third embodiment of the present invention will be described using Figures 22 to 24. This embodiment is similar to the first embodiment, and the contents described in the first embodiment can also be applied to this embodiment as long as they do not contradict the spirit of the first embodiment. The main difference between this embodiment and the first embodiment is the configuration of the inner bag 4. The following description will focus on these differences.

[0100] As shown in Fig. 22 , in this embodiment, the inner bag 4 has a protrusion 4k on its outer peripheral surface 4j that protrudes radially outward. As shown in Figs. 22 and 24 , the protrusion 4k is positioned farther from the ridge 4g than the engaging protrusion 3j when the ridge 4g is engaged with the recess 3m. The protrusion 4k is arranged to overlap the cam rail 3l in the axial direction, which is the direction in which the central axis C (shown in Fig. 2 ) of the mouth 5 of the container body 2 extends.

[0101] In the configuration of the first embodiment, when the inner bag 4 and the outer shell 3 are rotated relative to each other in the other direction (the direction of rotation when pulling out the inner bag 4), and the convex rib 4g overcomes the engaging convex portion 3j, the convex rib 4g is pressed radially inward by the engaging convex portion 3j, causing the entire convex rib 4g to be displaced further inward than the inner edge of the cam rail 3l.As a result, the convex rib 4g may fall off the cam rail 3l, making it difficult to pull out the inner bag 4 from the container body 2.

[0102] To prevent this problem from occurring, in this embodiment, the inner bag 4 is provided with a protrusion 4k. Because the protrusion 4k is located downstream of the engaging protrusion 3j in the other direction of rotation, the protrusion 4k does not need to overcome the engaging protrusion 3j when disengaging the rib 4g from the groove 3m. Therefore, even if the rib 4g is displaced radially inward, the protrusion 4k undergoes little or no radial displacement. Furthermore, because the protrusion 4k is located so as to overlap the cam rail 3l in the axial direction, even if the entire rib 4g is displaced further inward than the inner edge of the cam rail 3l, the rib 4g is prevented from falling off the cam rail 3l by being supported by the cam rail 3l.

[0103] The protrusions 4k are preferably elongated ridges, and more preferably inclined like the ridges 4g. In this case, when the inner bag 4 and the outer shell 3 are rotated relative to each other in the other direction, both the ridges 4g and the protrusions 4k move along the cam rails 3l, allowing the inner bag 4 to rotate more stably relative to the outer shell 3.

[0104] The ridge 4g and the protrusion 4k may be separate protrusions, or may be separate portions of a single protrusion. The entire ridge 4g and the protrusion 4k may be interpreted as the ridge 4o defined in the claims. In this case, a recess 4g6 is provided in the ridge 4o, and the engaging protrusion 3j engages with the recess 4g6. In this case, the other-side abutment surface 4g2 is the side surface of the recess 4g6. The ridge 4g is the upstream portion of the ridge 4o in the other direction of rotation, and the protrusion 4k is the downstream portion of the ridge 4o in the other direction of rotation.

[0105] In the first embodiment, as shown in FIG. 11 , the inner bag 4 was provided with an axial engagement portion 4ma composed of an annular protrusion 4n and a circumferential engagement portion 4mb composed of multiple protrusions 4mb1 arranged along the circumferential direction at a position farther from the open end 5c than the axial engagement portion 4ma. However, in this embodiment, as shown in FIG. 22 , the annular protrusion 4n is also provided with multiple protrusions 4mb2 arranged along the circumferential direction, and the protrusions 4mb2 are configured to engage with the spout attachment member 8 in the circumferential direction. That is, in this embodiment, the circumferential engagement portion 4mb is composed of the protrusions 4mb1 and 4mb2. This further prevents the spout attachment member 8 from spinning freely relative to the inner bag 4. This configuration is also applicable to the first embodiment.

[0106] 4. Fourth Embodiment A fourth embodiment of the present invention will be described using Figures 25 to 29. This embodiment is similar to the third embodiment, and the details described in the third embodiment can also be applied to this embodiment as long as they do not contradict the spirit of the third embodiment. The main difference between this embodiment and the third embodiment is the configuration of the inner bag 4 and the outer shell 3. The following description will focus on these differences.

[0107] 25, the recess 4h includes small recesses 4h1 and 4h2 (first and second small recesses) and a reinforcing rib 4h3. The small recess 4h2 is spaced apart from the small recess 4h1 in the circumferential direction of the inner bag 4. The circumferential length of each of the small recesses 4h1 and 4h2 is shorter than the length of the recess 4h in the third embodiment.

[0108] As shown in Figure 26A, the circumferential length L3 of the small recess 4h1 is equal to the circumferential length L4 of the small recess 4h2. The lengths L3 and L4 are, for example, 3 mm to 15 mm (7 mm in this embodiment), and preferably 5 mm to 10 mm. Specifically, the lengths L3 and L4 are 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15 mm, and may be within a range between the two values ​​exemplified here. However, the lengths L3 and L4 may be different from each other.

[0109] Length L3 is, for example, the length of the bottom surface (upper end surface in FIG. 26A ) of small recess 4h1 extending in the circumferential direction of inner bag 4. Similarly, length L4 is, for example, the length of the bottom surface (upper end surface in FIG. 26A ) of small recess 4h2 extending in the circumferential direction of inner bag 4.

[0110] 27, in a plan view of the inner bag 4, the line segment from the center Q1 of the inner bag 4 to the center Q2 of the bottom surface of the small recess 4h1 is defined as a first line segment P1, and the line segment from the center Q1 of the inner bag 4 to the center Q3 of the bottom surface of the small recess 4h2 is defined as a second line segment P2. The recess 4h is formed by being recessed so that the inner bag 4 protrudes inward at the recess 4h, so while the small recesses 4h1 and 4h2 shown in Fig. 25 are the front side, Fig. 27 shows the back side of the small recesses 4h1 and 4h2.

[0111] The angle θ3 between the first line segment P1 and the second line segment P2 is, for example, 10 to 100 degrees (50 degrees in this embodiment), and preferably 40 to 60 degrees. Specifically, the angle θ3 may be, for example, 10, 15, 20, 25, 30, 35, 40, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 60, 65, 70, 75, 80, 85, 90, 95, or 100 degrees, or may be within a range between any two of the values ​​exemplified here.

[0112] The distance from the small recess 4h1 to the one-side abutment surface 4g1 is shorter than the distance from the small recess 4h2 to the one-side abutment surface 4g1. The distance from the small recess 4h1 to the other-side abutment surface 4g2 is longer than the distance from the small recess 4h2 to the other-side abutment surface 4g2.

[0113] The reinforcing rib 4h3 is provided between the small recesses 4h1 and 4h2. The reinforcing rib 4h3 functions to improve the strength of the area around the ridge 4g. The reinforcing rib 4h3 is configured so that the inner bag 4 protrudes outward beyond the small recesses 4h1 and 4h2. The reinforcing rib 4h3 is provided at a position adjacent to the opening end 5c of the inner bag 4 relative to the ridge 4g.

[0114] In this embodiment, the recess 4h includes small recesses 4h1 and 4h2 and a reinforcing rib 4h3. This allows the recess 4h to more reliably function as a reinforcing rib. In particular, the reinforcing rib 4h3 is located closer to the opening edge 5c than the ridge 4g, improving the strength of the inner bag 4 near the ridge 4g. This reduces the likelihood of deformation of the ridge 4g and the area around it when the inner bag 4 is twisted. This reduces the likelihood of the ridge 4g falling off the recess 3m when, for example, removing the inner bag 4 from the container body 2.

[0115] 25 , in this embodiment, the inner bag 4 has a movement suppressing portion 4p on its outer peripheral surface 4j that protrudes radially outward. The movement suppressing portion 4p suppresses relative rotation of the inner bag 4 in the direction opposite to the direction of relative rotation when the inner bag 4 is pulled out. This prevents the inner bag 4 from being accidentally rotated in the opposite direction.

[0116] As shown in Figure 26A, the movement suppressing portion 4p is provided at a position adjacent to the opening end 5c of the inner bag 4 relative to the protrusion 4k. The movement suppressing portion 4p is provided at a position adjacent to the bottom side of the inner bag 4 relative to the recess 4h. The movement suppressing portion 4p is adjacent to the protrusion 4k in the height direction of the inner bag 4. The movement suppressing portion 4p extends in the circumferential direction of the inner bag 4. The longitudinal length of the movement suppressing portion 4p is shorter than the longitudinal length of the protrusion 4k. The movement suppressing portion 4p includes an abutment surface 4p1, a rear end surface 4p2, and a central surface 4p3.

[0117] The abutment surface 4p1 can abut against the abutment surface 3s described below. The abutment surface 4p1 is formed at the longitudinal end of the movement suppression portion 4p. The rear end surface 4p2 is formed on the opposite side of the abutment surface 4p1. The rear end surface 4p2 is flush with the rear end surface of the protrusion 4k. The rear end surface of the protrusion 4k is the end surface of the protrusion 4k opposite the other side abutment surface 4g2. The central surface 4p3 is a surface connecting the abutment surface 4p1 and the rear end surface 4p2. The central surface 4p3 extends in the longitudinal direction of the movement suppression portion 4p. The central surface 4p3 is flush with the outer surface of the protrusion 4k. The outer surface of the protrusion 4k is the surface of the protrusion 4k that is located radially outward of the inner bag 4.

[0118] 25 , the outer shell 3 includes an abutment surface 3s (restraint abutment surface) that can abut the movement suppressing portion 4p when the outer shell 3 is rotated relatively in one direction. The abutment surface 3s is provided closer to the opening end 3a of the outer shell 3 than the engaging protrusion 3j. The abutment surface 3s is provided at a position farther from the groove 3m than the engaging protrusion 3j.

[0119] Figure 26B shows a cross section taken along line D-D in Figure 26A when the inner bag 4 and the outer shell 3 are engaged with each other. The cross section in Figure 26B is located closer to the opening end 5c than the ridge 4g and the protrusion 4k. In the state shown in Figure 26B, for example, the one-side abutment surface 4g1 contacts the end 3m1. The end 3m1 is the end of the groove 3m opposite the engaging ridge 3j. In this state, the abutment surface 4p1 contacts, for example, the abutment surface 3s. Therefore, even if an attempt is made to further rotate the inner bag 4 in one direction while the inner bag 4 is engaged with the outer shell 3, the movement suppression portion 4p catches on the abutment surface 3s, preventing the inner bag 4 and the outer shell 3 from rotating in one direction. For example, even if the inner bag 4 is accidentally rotated in one direction when removing the inner bag 4 from the container body 2, the one-side abutment surface 4g1 is less likely to move further in one direction than the end 3m1 (see Figure 25).

[0120] 28 and 29 , a preform 15 used in manufacturing the double container 1 according to the fourth embodiment will be described. As shown in FIG. 28 , the inner peripheral surface 13n of the outer preform 13 is provided with a recessed rib 13m that can engage with the protruding rib 14g. The recessed rib 13m corresponds to the recessed rib 3m of the outer shell 3. The protruding rib 14g and the recessed rib 13m can be engaged by relative rotation of the inner preform 14 and the outer preform 13 in one direction. The protruding rib 14g and the recessed rib 13m are configured to be disengaged by relative rotation of the inner preform 14 and the outer preform 13 in the other direction. The outer preform 13 has an engaging protrusion 13j on the inner peripheral surface 13n that protrudes radially inward. The engaging protrusion 13j corresponds to the engaging protrusion 3j of the outer shell 3.

[0121] The inner preform 14 has a protrusion 14k on its outer circumferential surface 14j that protrudes radially outward. When the ridge 14g is engaged with the groove 13m, the protrusion 14k is positioned farther from the ridge 14g than the engaging protrusion 13j. The ridge 14g has a first abutment surface 14g1 that abuts against the engaging protrusion 13j when the inner preform 14 is rotated relative to the groove 13m, and a second abutment surface 14g2 that abuts against the engaging protrusion 13j when the inner preform 14 is rotated relative to the groove 13m.

[0122] The recess 14h includes a small recess 14h1 corresponding to the small recess 4h1, a small recess 14h2 corresponding to the small recess 4h2, and a reinforcing rib 14h3 corresponding to the reinforcing rib 4h3. The reinforcing rib 14h3 is provided between the small recesses 14h1 and 14h2.

[0123] The reinforcing rib 14h3 is configured so that the inner preform 14 protrudes outward beyond the small recesses 14h1 and 14h2. The reinforcing rib 14h3 is provided at a position adjacent to the open end 15f side of the inner preform 14 relative to the ridge 14g.

[0124] In this embodiment, the recess 14h includes small recesses 14h1 and 14h2 and a reinforcing rib 14h3. This allows the recess 14h to more reliably function as a reinforcing rib. In particular, the reinforcing rib 14h3 is located closer to the opening end 15f than the ridge 14g, improving the strength of the inner preform 14 near the ridge 14g. This reduces the likelihood of deformation near the ridge 14g when the preform 15 is biaxially stretch-blow molded to form the container body 2.

[0125] As shown in Figure 28, the inner preform 14 has a movement suppressing portion 14p on its outer peripheral surface 14j that protrudes radially outward. The movement suppressing portion 14p corresponds to the movement suppressing portion 4p. The movement suppressing portion 14p suppresses the one-side abutment surface 14g1 from moving further in one direction than the end 13m1 of the groove 13m when the outer preform 13 and the inner preform 14 are rotated relative to each other in one direction. The end 13m1 is the end of the groove 13m opposite the engaging protrusion 13j. The end 13m1 corresponds to the end 3m1. The movement suppressing portion 14p includes an abutment surface 14p1 corresponding to the abutment surface 4p1, a rear end surface 14p2 corresponding to the rear end surface 4p2, and a central surface 14p3 corresponding to the central surface 4p3.

[0126] The abutment surface 14p1 can abut against the abutment surface 13s (described later). The abutment surface 14p1 is formed at a longitudinal end of the movement suppressing portion 14p. The rear end surface 14p2 is formed on the opposite side of the abutment surface 14p1. The central surface 14p3 is a surface connecting the abutment surface 14p1 and the rear end surface 14p2.

[0127] The outer preform 13 includes an abutment surface 13s (restraint abutment surface) that can abut the movement suppressing portion 4p when the outer preform 13 is rotated relative to the movement suppressing portion 4p in one direction. The abutment surface 13s corresponds to the abutment surface 3s. The abutment surface 13s is provided at a position adjacent to the open end 13f of the outer preform 13 relative to the engaging protrusion 13j. The abutment surface 13s is provided at a position farther from the groove 13m than the engaging protrusion 13j.

[0128] Figure 29 shows a cross-sectional view corresponding to Figure 26B, in which the inner preform 14 and the outer preform 13 are engaged with each other. The cross-section in Figure 29 is located closer to the opening end 15f than the rib 14g and the protrusion 14k. In the state shown in Figure 29, for example, the one-side abutment surface 14g1 contacts the end 13m1. In this state, the abutment surface 14p1 contacts the abutment surface 13s. Therefore, even if an attempt is made to further rotate the inner preform 14 in one direction when the inner preform 14 and the outer preform 13 are engaged with each other, the movement suppressing portion 14p catches on the abutment surface 13s, preventing the inner preform 14 and the outer preform 13 from rotating relative to each other in one direction. As a result, the one-side abutment surface 14g1 is prevented from moving further in one direction beyond the end 13m1 (overrun of the rib 14g).

[0129] In the fourth embodiment, an example has been described in which the recess 4h includes the small recesses 4h1 and 4h2, but the recess 4h may include three or more small recesses. In other words, the recess 4h may include one or more other small recesses in addition to the small recesses 4h1 and 4h2. Similarly, the recess 14h of the inner preform 14 may include one or more other small recesses in addition to the small recesses 14h1 and 14h2.

[0130] In the fourth embodiment, an example has been described in which the abutment surface 4p1 is in contact with the abutment surface 3s when the one-side abutment surface 4g1 is in contact with the end portion 3m1, but the abutment surface 4p1 may be spaced apart from the abutment surface 3s within a range that can prevent the one-side abutment surface 4g1 from moving further in one direction than the end portion 3m1. Furthermore, the abutment surface 4p1 may be in contact with the abutment surface 3s when the one-side abutment surface 4g1 is spaced apart from the end portion 3m1. Similarly, in the inner preform 14, the abutment surface 14p1 may be spaced apart from the abutment surface 13s when the one-side abutment surface 14g1 is in contact with the end portion 13m1. The abutment surface 14p1 may be in contact with the abutment surface 13s when the one-side abutment surface 14g1 is spaced apart from the end portion 13m1.

[0131] In the fourth embodiment, an example was described in which the movement suppressing portion 4p is adjacent to the protrusion 4k in the height direction of the inner bag 4. However, the movement suppressing portion 4p may be spaced apart from the protrusion 4k in the height direction of the inner bag 4. In the above description, the inner bag 4 is described as having the ridge 4g, the protrusion 4k, and the movement suppressing portion 4p on its outer circumferential surface 4j, but the protrusion 4k may include the movement suppressing portion 4p. In other words, the protrusion 4k may perform both the function of making the ridge 4g less likely to fall off the cam rail 3l and the function of suppressing the one-side abutment surface 4g1 from moving further in one direction than the end 3m1. Similarly, in the inner preform 14, the protrusion 14k may include the movement suppressing portion 14p.

[0132] The configuration of the movement suppressing portion 4p is not limited to the configuration described above. The movement suppressing portion 4p only needs to be able to suppress the one-side contact surface 4g1 from moving further in one direction than the end portion 3m1. For example, the movement suppressing portion 4p may be provided at a position adjacent to the bottom side of the inner bag 4 relative to the protrusion 4k. In this case, the contact surface 3s may be provided at a position adjacent to the bottom side of the outer shell 3 relative to the engaging protrusion 3j. Similarly, in the inner preform 14, the movement suppressing portion 14p may be provided at a position adjacent to the bottom 14c side of the inner preform 14 relative to the protrusion 14k.

[0133] 5. Other Embodiments The direction of relative rotation of each component may be reversed from that of the above embodiment. That is, while the above embodiment is configured such that rotation of the clockwise thread loosens the inner bag 4, the inner bag 4 may be configured such that rotation of the counterclockwise thread loosens the inner bag 4. In this case, the lower surface of the ridge 4g and the upper surface of the cam rail 3l are inclined so as to approach the opening end 5c as they move clockwise when viewed from the opening end side of the container body 2. Furthermore, it is preferable that the ridge 6d2 extend from the boundary 6e toward the base 5b1 of the mouth 5 at an inclination in the clockwise direction.

[0134] 1: double container, 2: container body, 3: outer shell, 3a: opening end, 3a1: base surface, 3a2: annular convex portion, 3a3: inner bag support surface, 3a4: apex, 3g: recess, 3i: contact surface, 3j: engaging convex portion, 3j1: one side contact surface, 3j2: other side contact surface, 3j4: base, 3j5: base, 3j6: connecting line, 3l: cam rail, 3m: groove, 3m1: end, 3n: inner peripheral surface, 3o: enlarged diameter portion, 3p: inner tapered portion, 3q: outer tapered portion, 3r: portion, 3s: contact surface (restraint contact surface), 4: inner bag, 4a: first tube, 4b: second tube, 4b1: peripheral wall, 4b2: bottom wall, 4b3: corner portion, 4b4: Lower surface, 4c: protrusion, 4c13: recess, 4d: inner bag body, 4f: sealing cylinder, 4f1: inner surface, 4g: ridge, 4g1: one side abutment surface, 4g2: other side abutment surface, 4g3: central surface, 4g4: root, 4g5: root, 4g6: recess, 4h: recess, 4h1: small recess (first small recess), 4h2: small recess (second small recess), 4h3: reinforcing rib, 4i: abutment surface, 4j: outer circumferential surface, 4j1: tangent, 4j2: tangent, 4k: projection, 4m: engaging portion, 4m3: lower surface, 4ma: axial engaging portion, 4mb: circumferential engaging portion, 4mb1: protrusion, 4mb2: protrusion, 4n: annular protrusion, 4o: protrusion, 4p: moving Motion suppressing portion, 4p1: contact surface, 4p2: rear end surface, 4p3: central surface, 4u: undercut portion, 5: mouth portion, 5a: upper mouth portion, 5b: lower mouth portion, 5b1: base, 5c: opening end, 5d: flange portion, 5d1: lower surface, 6: body portion, 6b: shoulder portion, 6c: body portion main body, 6d: uneven shape, 6d1: concave groove, 6d2: convex groove, 6e: boundary, 6f1: groove-shaped rib, 6f2: groove-shaped rib, 7: bottom portion, 8: mouth portion mounting member, 8a: cap, 8b: engagement portion, 8c: nozzle, 8d: discharge port, 13: outer preform, 13a: mouth portion, 13b: body portion, 13c: bottom, 13f: opening end, 13g: adjacent portion, 1 3j: engaging protrusion, 13m: groove, 13m1: end, 13n: inner peripheral surface, 13p: inner tapered portion, 13q: outer tapered portion, 13s: abutment surface (restraint abutment surface), 14: inner preform, 14a: mouth portion, 14b: body portion, 14b2: portion, 14c: bottom portion, 14d: protrusion, 14g: protrusion, 14g1: one side abutment surface, 14g2: other side abutment surface, 14h: recess, 14h1: small recess (first small recess), 14h2: small recess (second small recess), 14h3: reinforcing rib, 14j: outer peripheral surface, 14k: protrusion, 14m: engaging portion, 14p: movement suppression portion, 14p1: abutment surface, 14p2: rear end surface,14p3: central surface, 14t: protruding seal portion, 15: preform, 15a: mouth portion, 15b: body portion, 15c: bottom portion, 15e: flange portion, 15e1: lower surface, 15f: opening end, 21: blow core, 21a: base portion, 21b: insertion portion, 21c: through hole, 22: bottom support mold, 23: molding mold, 23a: cavity surface, 23d: flange abutment surface, 23e: portion, 25: stretch rod, 31: cam mechanism, 32: heater, 33: heat shield portion, 35: heating device, 36: blow molding device, 41: cap body, 41a: outer tube, 41a1: opening end, 41b: inner tube, 41d: upper wall, 41i: flow hole, 42: overcap, 42a: outer tube, 42b: inner tube, 42d: upper wall, 43: hinge, 44: gap, 45: rail, C: central axis, C1: central axis, H: height position, P: reference plane, P1: first line segment, P2: second line segment, Q1: center, Q2: middle, Q3: middle, v: vertical line,

Claims

1. A double container comprising a container body, wherein the container body comprises an inner bag and an outer shell arranged to cover the inner bag, the inner bag being configured to be removable from the container body, the outer shell having a flange, the container body having a mouth, a body, and a bottom, the mouth having an upper mouth and a lower mouth, the upper mouth being the portion between the open end of the container body and the underside of the flange, the lower mouth being the portion between the upper mouth and the body, the portion below the underside of the flange where the outer diameter of the container body begins to expand being the base of the lower mouth, the bottom being a portion that closes the lower end of the body, and the outer shell having an inner tapered portion in at least a part of the lower mouth configured so that the inner diameter of the outer shell narrows towards the base.

2. A double container according to claim 1, wherein the outer shell has an outer tapered portion in at least a portion of the lower opening, configured so that the outer diameter of the outer shell narrows toward the base.

3. A double-walled container according to claim 2, wherein, when the lengths of the lower opening and the outer tapered portion in the axial direction of the mouth of the container body are L and Lo, respectively, Lo / L is 0.50 to 1.

00.

4. A double container according to claim 1, wherein, when the lengths of the lower opening and the inner tapered portion in the axial direction of the mouth of the container body are L and Li, respectively, Li / L is 0.50 to 1.

00.

5. A double container according to claim 1, wherein, when the lengths of the lower opening and the opening in the axial direction of the opening of the container body are L and La, respectively, L / La is 0.25 or more.

6. A preform for use in biaxial stretch blow molding, comprising an inner preform covered with an outer preform, the outer preform having a flange portion, and the outer preform having an inner tapered portion at a location adjacent to the bottom surface of the outer preform and closer to the bottom side of the flange portion than the bottom surface of the outer preform, the inner diameter of the outer preform narrowing toward the bottom of the outer preform.

7. A preform according to claim 6, wherein the outer preform has an outer tapered portion at the adjacent portion configured such that the outer diameter of the outer preform decreases towards the bottom of the outer preform.

8. A method for manufacturing a double-layered container according to any one of claims 1 to 5, comprising a biaxial stretch molding step of biaxially stretch molding a preform, wherein the preform is constructed by placing an outer preform over an inner preform, the outer preform having a flange portion, and the outer preform having an inner tapered portion at a location adjacent to the bottom surface of the outer preform and closer to the bottom side of the outer preform than the underside of the flange portion, the inner diameter of the outer preform narrowing towards the bottom of the outer preform.

9. The method of claim 8, wherein the outer preform comprises an outer tapered portion at the adjacent portion configured such that the outer diameter of the outer preform decreases toward the bottom of the outer preform.

10. A method according to claim 8, wherein, when the length of the lower opening in the axial direction of the mouth of the container body is L, and the length of a portion of the lower opening whose outer surface shape does not change from the shape of the preform before and after the biaxial stretch molding process is Lp, Lp / L is 0.50 to 1.

00.

11. A double container comprising a container body and a mouth attachment member, wherein the container body comprises an inner bag and an outer shell arranged to cover the inner bag, the mouth attachment member is attached to a protruding portion of the inner bag that protrudes from the open end of the outer shell, the mouth attachment member is circumferentially engaged with the protruding portion, the inner bag has a recess in a portion facing the outer shell, and the recess is formed by being recessed so that the inner bag protrudes inward at the recess.

12. A double container as claimed in claim 11, wherein the inner bag comprises a first tube disposed within the outer shell and a second tube having an outer diameter larger than that of the first tube and disposed closer to the open end of the inner bag than the first tube, the second tube having a peripheral wall and a lower wall disposed below the peripheral wall and configured to reduce the diameter of the peripheral wall toward the first tube, the inner bag being disposed so that the lower surface of the second tube abuts against the outer shell, and the recess is disposed at the corner between the lower wall and the peripheral wall.

13. A double container according to claim 12, wherein the corner portion is disposed within the outer shell.

14. A double-layered container according to any one of claims 11 to 13, wherein the inner bag has a ridge on its outer surface that protrudes radially outward, and the ridge is positioned adjacent to the recess and closer to the bottom than the recess.

15. A double container according to any one of claims 11 to 13, wherein the inner bag has a ridge on its outer surface that protrudes radially outward, the recesses include a first small recess, a second small recess that is spaced apart from the first small recess in the circumferential direction of the inner bag, and a reinforcing rib between the first and second small recesses, the reinforcing rib being configured such that the inner bag protrudes outward beyond the first and second small recesses, and the reinforcing rib is located adjacent to the ridge on the open end side of the inner bag.

16. A double container comprising a container body, wherein the container body comprises an inner bag and an outer shell arranged to cover the inner bag, the inner bag having a convex rib protruding radially outward on its outer peripheral surface, the outer shell having a concave rib, the convex rib and the concave rib are configured to be engageable by relative rotation of the inner bag and the outer shell in one direction and to be disengageable by relative rotation of the inner bag and the outer shell in the other direction, the outer shell having an engaging convex portion protruding radially inward on its inner peripheral surface, the convex rib having a one-side abutment surface that abuts against the engaging convex portion when the inner bag is rotated relative to the outer shell in the one direction, the inner bag having a movement suppressing portion protruding radially outward on its outer peripheral surface, the movement suppressing portion suppressing the one-side abutment surface from moving further in the one direction beyond the end of the concave rib when the inner bag is rotated relative to the outer shell in the one direction, and the outer shell including a suppressing abutment surface that can abut against the movement suppressing portion when the inner bag is rotated relative to the outer shell in the one direction.

17. A double container as described in claim 16, wherein the convex rib has an other-side abutment surface that abuts against the engaging convex portion when rotated relative to the other direction, the inner bag has a protrusion on its outer surface that protrudes radially outward, the protrusion is positioned at a position farther from the convex rib than the engaging convex portion when the convex rib is engaged with the concave rib, and the movement suppression portion is provided at a position adjacent to the opening end side of the inner bag than the protrusion.

18. A preform formed by covering an outer preform with an inner preform, wherein the inner preform has a convex rib on its outer peripheral surface that protrudes radially outward, and the outer preform has a concave rib, wherein the convex rib and the concave rib can be engaged by relative rotation of the inner preform and the outer preform in one direction and can be disengaged by relative rotation of the inner preform and the outer preform in the other direction, the inner preform has a concave portion in a portion facing the outer preform, and the concave portion is formed by being recessed so that the inner preform protrudes inward at the concave portion, and the concave portion includes a first small concave portion, a second small concave portion spaced apart from the first small concave portion in the circumferential direction of the inner preform, and a reinforcing rib between the first and second small concave portions, wherein the reinforcing rib is configured so that the inner preform protrudes outward further than the first and second small concave portions, and the reinforcing rib is provided at a position adjacent to the open end side of the inner preform relative to the convex rib.

19. A preform formed by covering an outer preform with an inner preform, wherein the inner preform has a convex rib that protrudes radially outward on its outer peripheral surface, and the outer preform has a concave rib, the convex rib and the concave rib are configured to be engageable by relative rotation of the inner preform and the outer preform in one direction and to be disengageable by relative rotation of the inner preform and the outer preform in the other direction, the outer preform has an engaging convex portion that protrudes radially inward on its inner peripheral surface, the convex rib has a one-side abutment surface that abuts against the engaging convex portion when the inner preform is rotated relative to the outer preform in the one direction, the inner preform has a movement suppressing portion that protrudes radially outward on its outer peripheral surface, and the movement suppressing portion suppresses the one-side abutment surface from moving further in the one direction beyond the end of the concave rib when the outer preform and the inner preform are rotated relative to the outer preform in the one direction, and the outer preform includes a suppressing abutment surface that can abut against the movement suppressing portion when the outer preform is rotated relative to the inner preform in the one direction.

20. A preform as claimed in claim 19, wherein the convex rib has an other-side abutment surface that abuts against the engaging convex portion when the outer preform and the inner preform are rotated relative to each other in the other direction, the inner preform has a protrusion on its outer peripheral surface that protrudes radially outward, the protrusion is positioned at a position farther from the convex rib than the engaging convex portion when the convex rib is engaged with the concave rib, and the movement suppression portion is provided at a position adjacent to the open end side of the inner preform than the protrusion.

21. A method for manufacturing a double container according to any one of claims 11 to 13, wherein the container body of the double container is manufactured by biaxially stretched blow molding.

22. A double container comprising a container body, wherein the container body comprises an inner bag and an outer shell arranged to cover the inner bag, the inner bag having a convex rib protruding radially outward on its outer peripheral surface, the outer shell having a concave rib, the convex rib and the concave rib are configured to be engageable by relative rotation of the inner bag and the outer shell in one direction and to be disengageable by relative rotation of the inner bag and the outer shell in the other direction, the outer shell having an engaging convex portion protruding radially inward on its inner peripheral surface, the convex rib having a first other-side abutment surface that abuts the engaging convex portion when rotated relative to the other direction, and the first other-side abutment surface being an end face located at the longitudinal end of the convex rib or a side face of a concave portion provided in the convex rib.

23. A double container according to claim 22, wherein the first other-side abutment surface has a first other-side inclination angle, which is the inclination angle with respect to the tangent of the outer peripheral surface at the base of the first other-side abutment surface, of 5 to 45 degrees.

24. A double container as described in claim 23, wherein the convex rib has a first one-side abutment surface that abuts against the engaging convex portion when rotated relative to the one direction, the first one-side abutment surface is an end surface located at the longitudinal end of the convex rib, and the first one-side inclination angle, which is the inclination angle with respect to the tangent of the outer peripheral surface at the base of the first one-side abutment surface, is greater than the first other-side inclination angle.

25. A double container as described in claim 22, wherein the engaging convex portion has a second one-side abutment surface that abuts against the convex rib when rotated relatively in the one direction, and a second other-side abutment surface that abuts against the convex rib when rotated relatively in the other direction, and the second one-side inclination angle, which is the angle of inclination of the second one-side abutment surface with respect to a connecting line connecting the base of the second one-side abutment surface and the base of the second other-side abutment surface, is smaller than the second other-side inclination angle, which is the angle of inclination of the second other-side abutment surface with respect to the connecting line.

26. A double container as described in claim 22, wherein the convex rib has a first one-side abutment surface that abuts against the engaging convex portion when rotated relative to the other in the one direction, the first one-side abutment surface is an end surface located at the longitudinal end of the convex rib, and the central surface between the first one-side abutment surface and the first other-side abutment surface has a shape similar to that of the portion of the outer shell that faces the central surface.

27. A double container according to claim 26, wherein the central surface is free of any protrusions projecting from the central surface.

28. A double container according to claim 22, wherein the ridges are hollow.

29. A double container as described in claim 22, wherein a cam rail is provided on the inner peripheral surface of the outer shell, the recessed ribs are provided at the ends of the cam rail, the lower surface of the ridges and the upper surface of the cam rail are inclined so as to approach the opening end of the container body as they proceed counterclockwise or clockwise when viewed from the opening end side, and when the inner bag and the outer shell are rotated relative to each other in the other direction, the cam mechanism formed by the ridges and the cam rail acts to move the inner bag in a direction that allows it to escape from the container body.

30. A double container as described in claim 29, wherein the inner bag has a protrusion on its outer surface that protrudes radially outward, the protrusion is positioned at a position farther from the ridge than the engaging protrusion when the ridge is engaged with the groove, and the protrusion is arranged so as to overlap the cam rail in the axial direction, which is the direction in which the central axis of the mouth of the container body extends.

31. A method for manufacturing a double container according to any one of claims 22 to 30, wherein the container body is manufactured by biaxially stretched blow molding.

32. A double container comprising a container body and a mouth attachment member, wherein the container body comprises an inner bag and an outer shell arranged to cover the inner bag, the mouth attachment member is attached to a protruding portion of the inner bag that protrudes from the open end of the outer shell, the inner bag and the outer shell abut at abutting surfaces on the inner bag side and the outer shell side, and the abutting surface on the outer shell side is inclined so as to face the inside of the outer shell.

33. A double container as claimed in claim 32, wherein the inner bag comprises a first tube disposed within the outer shell, and a second tube having an outer diameter larger than that of the first tube and disposed closer to the open end of the inner bag than the first tube, the second tube comprising a peripheral wall and a lower wall disposed below the peripheral wall and configured to reduce the diameter of the peripheral wall toward the first tube, and the abutting surface on the inner bag side is the lower surface of the second tube.

34. A double container according to claim 33, wherein the lower wall is disposed within the outer shell.

35. A double container according to any one of claims 32 to 34, wherein the inner bag has a convex rib on its outer surface, and the outer shell has a concave rib on its inner peripheral surface, the convex rib and the concave rib can be engaged with each other by relative rotation of the inner bag and the outer shell in one direction, and can be disengaged by relative rotation of the inner bag and the outer shell in the other direction, and when the convex rib and the concave rib are engaged, the abutting surface on the inner bag side is pressed against the abutting surface on the outer shell side.

36. A double container as described in claim 35, wherein a cam rail is provided on the inner peripheral surface of the outer shell, the recessed ribs are provided at the ends of the cam rail, the lower surface of the ridges and the upper surface of the cam rail are inclined so as to approach the opening end of the container body as they proceed counterclockwise or clockwise when viewed from the opening end side, and when the inner bag and the outer shell are rotated relative to each other in the other direction, the cam mechanism formed by the ridges and cam rail acts to move the inner bag in a direction that allows it to escape from the container body.

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