Patent Publication Number: US-10308402-B2

Title: Spout stopper and packaging container

Description:
TECHNICAL FIELD 
     The present invention relates to a spout stopper and a packaging container. 
     BACKGROUND ART 
     A technique is known in which a spout stopper (spout) having a screw portion is provided at a pour-out port of a container body for a product such as beverage, liquid seasoning, or cosmetic and the pour-out port is closed by a cap having a screw portion formed so as to be able to be brought into threaded engagement with the screw portion of the spout stopper. With the spout stopper and the cap, capping is enabled to be repeatedly performed, by bringing the screw portions into threaded engagement with each other even after the cap is removed for opening. 
     Patent Literature 1 discloses a cap body including a contact ring and an inner ring that are provided on the inner surface of the cap body at the sealing side and are brought into engagement with an end of a pour-out port body (spout stopper) at a pour-out port to enhance sealability. 
     Patent Literature 2 discloses a stopper including a spout having an end portion that is formed so as to spread at the same angle as the inclination angle of an inclined plate of a paper container, whereby when a content liquid is poured out, running-down of the liquid is less likely to occur and shutting-off of the liquid is good. 
     For mounting a spout stopper made of a resin material to a container body, an ultrasonic welding method is often used in which ultrasonic vibration is applied to a flange of the spout stopper to weld the flange. 
     Patent Literature 3 discloses a spout stopper (stopper with a pull ring) in which a cut-off portion (annular opening) is provided near the inner edge of a flange surface, whereby vibration occurring during ultrasonic welding is inhibited from being transmitted to a half-cut portion (annular thin brittle line) of a partition (blocking plate) that closes the spout stopper, thereby preventing occurrence of a crack. 
     Patent Literature 4 discloses a technique in which, in the above-described spout stopper having the cut-off portion, in order to inhibit projections, which are provided at equal intervals in the circumferential direction of a side wall for holding a container body between a flange and the projections, from being deformed by the energy of ultrasonic vibration, ribs are provided on the inner surface of the cut-off portion and at positions corresponding to the projections, whereby the energy of the ultrasonic vibration is dispersed and absorbed. 
     CITATION LIST 
     Patent Literature 
     [PTL 1] Japanese Laid-Open Patent Publication No. 2004-331221 
     [PTL 2] Japanese Laid-Open Patent Publication No. 2008-018971 
     [PTL 3] Japanese Laid-Open Patent Publication No. 2004-067101 
     [PTL 4] Japanese Laid-Open Patent Publication No. 2011-105383 
     SUMMARY OF THE INVENTION 
     Problems to be Solved by the Invention 
     However, in the case of mounting the spout to the container body by welding, a low-density polyethylene resin is often used as the material of the spout, and a polypropylene resin or a high-density polyethylene, which is a material harder than the low-density polyethylene resin, etc. is often used as the material of the cap. In the case where such materials are used, when a contact ring is formed in the cap, a trace of engagement of the contact ring is likely to remain on a contact portion of the spout with the contact ring. Particularly, a trace of engagement of the contact ring remaining on the spout remains as a circumferential V-shaped groove at the upper end of the spout, and causes deterioration of performance of shutting off a content liquid being poured out. 
     The present invention has been made in view of the above-described problem, and an object of the present invention is to provide a spout stopper that prevents a decrease in sealing performance to a cap without deterioration of liquid-shutting-off performance of a stopper body, and a packaging container using the spout stopper. 
     In addition, such a stopper is often fixed to a packaging container by welding and used. Thus, for the purpose of enhancing sealability between the spout stopper and the packaging container after welding, a low-density polyethylene resin (LDPE, L-LDPE) is often used as the material of the spout. In such a case, a polypropylene resin or a high-density polyethylene resin, which has higher rigidity than the low-density polyethylene resin, etc. is used as the material of the cap, whereby sealability between the spout and the cap can be enhanced. 
     However, when the rigidity of the cap is higher than the rigidity of the spout, if an excessive torque is applied to the spout and the cap, the spout having lower rigidity falls down in the inner peripheral direction due to a load received from an internal screw of the cap, so that “overrun” that the internal screw climbs over a screw portion of the spout may occur. When overrun occurs, threaded engagement with the cap becomes imperfect, so that the content liquid is likely to leak. In addition, by an external screw of the spout being partially scraped by the screw portion of the cap due to the overrun, play (a gap) may occur in the threaded engagement, resulting in a decrease in the sealing performance of the spout stopper. 
     The present invention has been made in view of the above-described problem, and an object of the present invention is to provide a spout stopper that can inhibit occurrence of overrun even when an excessive torque is applied to a cap and a stopper body, and a packaging container using the spout stopper. 
     Moreover, in the case of such a stopper, in threaded attachment between the screw portions, unless the cap is threadedly attached to the spout such that the screw axes of the cap and the spout coincide with each other, and then the cap is rotated, the screw portions are less likely to be brought into threaded engagement with each other in a state where the screw portions are properly in mesh with each other. In a state where the screw axes of the cap and the spout do not coincide with each other so that the cap is tilted relative to the spout, if a user attempts to forcedly rotate the cap, a threaded engagement failure is likely to occur, for example, threaded engagement cannot be successfully achieved, or the cap is fixed to the spout in an incomplete state where screw threads thereof are not properly in mesh with each other. 
     In addition, the screw portion of the cap is likely to come into contact with a liquid-running-down prevention shape at the spout end or the like before coming into contact with the screw portion of the spout. Thus, even when the user attempts to threadedly attach the cap to the spout stopper such that the central axes of the cap and the spout coincide with each other, the attitude of the cap is changed by the screw portion of the cap coming into contact with the liquid-running-down prevention shape, so that the cap may not be properly brought into threaded engagement with the spout, causing a threaded engagement failure. 
     The present invention has been made in view of the above-described problem, and an object of the present invention is to provide a spout stopper that can prevent occurrence of a threaded engagement failure of screw portions of a cap and the spout stopper, and a packaging container using the spout stopper. 
     Furthermore, as in Patent Literature 3 or 4, there is a proposal to provide a cut-off portion and a rib in order to inhibit deformation of each portion of a spout stopper during ultrasonic welding. However, suitable design for the cut-off portion and the rib has not been sufficiently examined. 
     The present invention has been made in view of the above-described problem, and an object of the present invention is to provide a spout stopper that can favorably inhibit each portion from deforming due to ultrasonic welding, and a packaging container using the spout stopper. 
     Solution to the Problems 
     An aspect of the present invention for solving the above-described problem is a spout stopper including: a stopper body including a cylindrical side wall; and a cap to be mounted from an upper end side that is one end of the side wall, wherein a projection is formed at an upper end edge of the side wall so as to project outward from the side wall, and a top surface at an upper end of the side wall is in surface contact with a predetermined contact surface inside the cap over an entire circumference thereof in a state where the cap is mounted on the side wall. 
     Another aspect of the present invention for solving the above-described problem is a spout stopper including a stopper body including a cylindrical side wall having an external screw formed on an outer circumferential surface thereof; and a cap including a cylindrical side wall having an internal screw formed on an inner circumferential surface thereof, the cap being to be mounted from an upper end side that is one end of the side wall of the stopper body, wherein a disc-shaped flange is formed at a lower end of the side wall of the stopper body so as to extend outward from a lower end edge of the side wall of the stopper body, and the external screw is formed in a range along a screw axis direction from a connection position at which the side wall of the stopper body is connected to the flange to a distance that is not less than ⅓ of a distance between the connection position and the upper end edge and not greater than ⅔ of the distance between the connection position and the upper end edge. 
     Another aspect of the present invention for solving the above-described problem is a spout stopper including: a stopper body including a cylindrical side wall; and a cap to be mounted from an upper end side that is one end of the side wall, wherein an outer circumferential surface of the side wall includes an external screw portion on which an external screw is formed, and a guide portion that is a region at an upper end side with respect to the external screw portion and on which the external screw is not formed, an inner circumferential surface of the cap includes an internal screw portion on which an internal screw to be brought into threaded engagement with the external screw is formed, and a distance along a screw axis direction between a formation start position that is an upper end of the internal screw and a formation end position that is a lower end of the internal screw is shorter than a guide portion length that is a distance from the upper end edge of the side wall to a formation start position at an upper end side of the external screw. 
     Another aspect of the present invention for solving the above-described problem is a spout stopper including: a cylindrical side wall; a partition closing an interior of the side wall and having a half-cut formed at an outer peripheral portion; a disc-shaped flange provided so as to extend outward from a lower end edge of the side wall; a groove-shaped cut-off portion provided on a surface of the flange opposite to the side wall so as to be concentric with the side wall; and a plurality of ribs provided on an inner surface of the cut-off portion, wherein an interval between each of the plurality of ribs and the rib adjacent thereto along a circumferential direction of the cut-off portion is not less than 0.5 mm and not greater than 5.0 mm. 
     Another aspect of the present invention is a packaging container including a container body and the above spout stopper mounted on the container body. 
     Advantageous Effects of the Invention 
     The spout stopper according to the present invention can prevent a decrease in sealing performance to the cap without deterioration the liquid-shutting-off performance of the stopper body, can inhibit occurrence of overrun even when an excessive torque is applied to the cap and the stopper body, can prevent a threaded engagement failure of the screw portions of the cap and the stopper body, and can inhibit each portion from deforming due to ultrasonic welding. 
     The present invention can provide a packaging container using such a spout stopper. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a cross-sectional view showing a spout stopper according to an embodiment of the present invention. 
         FIG. 1B  is a cross-sectional view showing a spout stopper according to an embodiment of the present invention. 
         FIG. 2  is a perspective view showing a packaging container according to the embodiment of the present invention. 
         FIG. 3  is a cross-sectional view showing a spout stopper according to a modification of the present invention. 
         FIG. 4A  is a cross-sectional view showing the spout stopper according to the embodiment of the present invention. 
         FIG. 4B  is a cross-sectional view showing the spout stopper according to the embodiment of the present invention. 
         FIG. 5A  is a cross-sectional view showing the spout stopper according to the embodiment of the present invention. 
         FIG. 5B  is a cross-sectional view showing the spout stopper according to the embodiment of the present invention. 
         FIG. 6A  is a cross-sectional view showing a state where a cap is being threadedly attached to the spout stopper according to the embodiment of the present invention. 
         FIG. 6B  is a cross-sectional view showing a state where a cap is being threadedly attached to the spout stopper according to the embodiment of the present invention. 
         FIG. 6C  is a cross-sectional view showing a state where a cap is being threadedly attached to the spout stopper according to the embodiment of the present invention. 
         FIG. 6D  is a cross-sectional view showing a state where a cap is being threadedly attached to the spout stopper according to the embodiment of the present invention. 
         FIG. 7  is a cross-sectional view showing the spout stopper according to the embodiment of the present invention. 
         FIG. 8A  is a bottom view showing the spout stopper according to the embodiment of the present invention. 
         FIG. 8B  is an enlarged view showing the spout stopper according to the embodiment of the present invention. 
         FIG. 8C  is a partial cross-sectional view showing the spout stopper according to the embodiment of the present invention. 
         FIG. 9A  is a bottom view showing a spout stopper according to a modification of the embodiment of the present invention. 
         FIG. 9B  is an enlarged view showing a spout stopper according to a modification of the embodiment of the present invention. 
         FIG. 9C  is a partial cross-sectional view showing a spout stopper according to a modification of the embodiment of the present invention. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     A spout stopper  3  and a packaging container  5  according to an embodiment of the present invention will be described with reference to  FIGS. 1A, 1B and 2 .  FIGS. 1A and 1B  show a cross-sectional view of the spout stopper  3  that includes a stopper body  1  and a cap  2 .  FIG. 2  shows a perspective view of the packaging container  5  that includes: the spout stopper  3  including the stopper body  1  and the cap  2 ; and a container body  4 . In the present specification, “threaded engagement” means that screw threads of the cap and of a side wall of the stopper body are caused to be in mesh with each other and are rotated relative to each other in the circumferential direction, thereby fitting (mounting) the cap and the stopper body to each other. In addition, “screw axis” means a virtual line that is present on the center of a circumference forming the screw thread and extends in a direction in which the cap moves in bringing the cap and the stopper body into threaded engagement with each other. 
     First, the spout stopper  3 , the stopper body  1 , and the cap  2  will be described. 
     As shown in  FIGS. 1A and 1B , the spout stopper  3  includes the stopper body  1  and the cap  2 . The stopper body  1  includes a cylindrical side wall  11 . The side wall  11  has a top surface  109  formed at the upper end side which is one end. The cap  2  includes a cylindrical side wall  21 , a top plate  24 , and a contact surface  27  formed so as to be perpendicular to the screw axis of the cap  2 . The cap  2  is mounted from the upper end side of the side wall  11  of the stopper body  1 . A projection  15  is formed at the upper end edge of the side wall  11  so as to project outward from the side wall  11 . The top surface  109  at the upper end of the side wall  11  is in surface contact with the contact surface  27  of the cap  2  in a state where the cap  2  is mounted on the side wall  11  of the stopper body  1 . Since the projection  15  is formed so as to project outward from the upper end edge of the side wall  11  of the stopper body  1 , liquid-shutting-off performance exerted when a content liquid is poured out can be improved to prevent the content liquid from running down on the outer circumferential surface of the side wall  11  at the time of pouring-out to make the stopper body  1  dirty. The upper end of the side wall  11  of the stopper body  1  refers to the upper side of the side wall  11  in the sheet of  FIGS. 1A and 1B . 
     A disc-shaped flange  16  is formed at the lower end edge of the side wall  11  of the stopper body  1  so as to extend outward. The flange  16  is a location where the container body  4  and the spout stopper  3  are joined to each other in producing the packaging container  5  including the container body  4  and the spout stopper  3  mounted on the container body  4  as shown in  FIG. 2 . As the joining method, ultrasonic welding may be used. 
     A cylindrical first outer diameter portion  13  and a cylindrical second outer diameter portion  14  having a larger outer diameter than the first outer diameter portion  13  are provided below the projection  15 , which is provided at the upper end of the side wall  11  of the stopper body  1 . On an outer circumferential surface  17  of the second outer diameter portion  14 , an external screw  12  is formed which can be brought into threaded engagement with an internal screw  22  of the cap  2  described later. 
     As shown in  FIGS. 1A and 1B , the cap  2  includes: the cylindrical side wall  21  having an inner circumferential surface  23  on which the internal screw  22  is formed; and the top plate  24  that covers the side wall  21  from the upper end side. The side wall  21  and the top plate  24  are connected to each other by a thick portion  26  that is provided from the upper end side of the side wall  21  to the outer periphery of the top plate  24  of the upper end side. On the inner circumferential surface  23  of the side wall  21 , the internal screw  22  is formed which can be brought into threaded engagement with the external screw  12 , which is formed on the side wall  11  of the stopper body  1 . Inside the cap  2 , a cylindrical inner ring  25  is formed adjacently with the thick portion  26  such that an end thereof is in contact with the top plate  24 . The contact surface  27  perpendicular to the screw axis is formed at the lower end of the thick portion  26 . 
     As shown in  FIG. 1B , the height of the contact surface  27  is set such that the top surface  109  of the side wall  11  is in surface contact with the contact surface  27  over the entire circumference thereof in a state where the cap  2  is mounted on the side wall  11  of the stopper body  1 , and the side wall  11  becomes elastically deformed upon reception of a compressive load. In addition, the outer circumferential surface of the inner ring  25  is formed such that a part thereof projects over the entire circumference, and is in contact with the inner circumferential surface  19  of the side wall  11  in a state where the cap  2  is mounted on the side wall  11  of the stopper body  1 . 
     In the present embodiment, in mounting the cap  2  onto the side wall  11  of the stopper body  1 , after the cap  2  is put on the side wall  11  from the upper end of the side wall  11 , the cap  2  is rotated relative to the side wall  11  in the circumferential direction, thereby bringing the external screw  12  and the internal screw  22  into threaded engagement with each other. When the threaded engagement between the external screw  12  and the internal screw  22  is completed, the top surface  109  at the upper end of the side wall  11  is in surface contact with the contact surface  27  of the cap  2 , the side wall  11  of the stopper body  1  becomes elastically deformed, and also the outer circumferential surface of the inner ring  25  is in contact with the inner circumferential surface  19  of the side wall  11 , as described above. 
     In the present embodiment, the area of the top surface  109  is increased by the projection  15 , whereby a large contact area with the contact surface  27  can be ensured as compared to the conventional art, and sealing performance can be improved. 
     In addition, when the cap  2  is mounted on the side wall  11  of the stopper body  1 , since the contact surface  27  is formed such that the side wall  11  becomes elastically deformed, the top surface  109  is in surface contact with the contact surface  27  at high contact pressure, so that the sealing performance can be improved. 
     The side wall  11  of the stopper body  1  receives a downward force shown by an arrow A in  FIG. 1B  at the top surface  109  and the projection  15  from the contact surface  27 , and receives an outward force shown by an arrow B in  FIG. 1B  at an inner circumferential surface  19  from the inner ring  25 . Thus, as a force obtained by combining these forces, the side wall  11  receives an obliquely downward force shown by an arrow P in  FIG. 1B , and becomes elastically deformed in a direction in which the side wall  11  is pressed and widened. As a result, the side wall  11  of the stopper body  1  is in contact with the cap  2  such that the top surface  109  and the inner circumferential surface  19  are pressed against the contact surface  27  and the outer circumferential surface of the inner ring  25 , respectively, by a restoring force of the side wall  11 . Therefore, the sealing performance of the stopper body  1  can be further improved. This force falls within a range of elastic deformation, and the side wall  11  immediately returns to the original shape after the cap  2  is opened. 
     Since the contact pressure of the side wall  11  of the stopper body  1  with respect to the contact surface  27  is increased, a torque (hereinafter, referred to as an opening torque) required for rotation of the cap  2  is increased, so that the cap  2  can be prevented from being loosened. In general, in the case where the lead angle of each screw is made large, the number of rotations required until threaded engagement is completed can be decreased, but the cap becomes easily loosened. However, even with a stopper body having a large lead angle, loosening of the cap can be prevented by applying the present invention. Thus, a stopper body can be provided with which the cap is less likely to become loosened while the number of rotations required until threaded engagement is completed is decreased. 
     The rigidity of the cap  2  is preferably higher than the rigidity of the side wall  11  of the stopper body  1 . For example, a low-density polyethylene resin (LDPE, L-LDPE) may be used as the material of the side wall  11  of the stopper body  1 , and a polypropylene resin or a high-density polyethylene resin, etc. may be used as the material of the cap  2 . By using the materials having such a relationship, an amount of elastic deformation of the side wall  11  of the stopper body  1  is increased, so that the side wall  11  can be used like a packing, and the sealing performance can be further enhanced. 
       FIG. 3  shows a modification of the present embodiment. In the present embodiment, the lower end of the thick portion  26  is formed as the contact surface  27  parallel to the top plate  24 . However, as shown in  FIG. 3 , a part of the top plate may be formed as a contact surface without providing a portion corresponding to the thick portion  26 . The mode of contact between the side wall of the stopper body and the cap is not limited to the above-described embodiment and the modification thereof, and it is needless to say that the position and the shape of the contact surface can be arbitrarily selected as long as the side wall comes into contact with the cap over the entire circumference and a trace of contact that leads to deterioration of the performance of shutting off the content liquid does not remain on the side wall. The shape of the upper end of the side wall of the stopper body may be variously set, for example, in accordance with design of the projection or the like for preventing running-down of liquid. In addition, the shape of the cap can be variously set. Therefore, in accordance with such variety, for example, an upper surface (curved surface or flat surface) that is not exactly the uppermost end such as the top surface at the upper end of the side wall of the stopper body and that is connected to the uppermost end and includes a chamfered portion near the outer side of the uppermost end, or an outer end portion of a projection in the case where the projection is provided, may come into contact with a chamfered portion (curved surface or flat surface) that is not exactly a horizontal surface and is near the upper end of the inner circumferential surface of the side wall of the cap. 
     The external screw  12  of the side wall  11  of the stopper body  1  and the internal screw  22  of the cap  2  may be single-thread screws or multiple-thread screws. 
     In the present embodiment, screw threads are formed on the cap  2  and the side wall  11  of the stopper body  1 , and a screw-cap type stopper body is used in which the screw threads are brought into threaded engagement with each other. However, the stopper body may be of any type, as long as the stopper body can be sealed by the top surface  109  of the side wall  11  and the contact surface  27  of the cap  2  being brought into surface contact with each other. For example, the present invention is applicable to a plugging cap in which a stopper body plugged into a container port and a cap for closing the stopper body are connected to each other by a hinge. 
     The embodiment of the present invention will be described further with reference to  FIGS. 4A and 4B . 
       FIG. 4A  shows a cross-sectional view of the spout stopper  3  in a state where the cap  2  is in threaded engagement, and  FIG. 4B  shows an enlarged view of a main part thereof. The stopper body  1  includes a partition  104  that is formed at the lower end of the side wall  11  and separates the upper end side and the lower end side of the interior of the side wall  11  from each other. Here, the upper end of the side wall  11  refers to one end at the side at which the cap  2  is threadedly attached (at the upper side in the sheet of  FIGS. 4A and 4B ). 
     The partition  104  includes a pull ring  103 . The user of the spout stopper  3  can pull out the partition  104  with the pull ring  103 , thereby causing the upper end side and the lower end side of the side wall  11  to communicate with each other to form an opening. 
     Between the inner ring  25  and the side wall  21 , a contact portion  28  is provided which is a region with which an upper end portion of the side wall  11  of the stopper body  1  is in surface contact over the entire circumference thereof. Thus, higher sealability is obtained. The contact portion  28  only needs to be provided such that the upper end portion of the side wall  11  and a portion of the side wall  11  near the upper end portion is in contact with the contact portion  28  in a threadedly attached state, and the contact portion  28  may be provided at any of a portion, near the upper end, of the outer circumferential surface of the inner ring  25  or the inner circumferential surface of the side wall  21  in the cap  2 , or a top surface portion between the outer circumferential surface of the inner ring  25  and the inner circumferential surface of the side wall  21 . 
     As shown in  FIG. 4B , a range (L 2 ) where the external screw  12  is formed is a range along the screw axis direction of the stopper body  1  from a connection position at which the side wall  11  is connected to the flange  16  to a distance that is not less than ⅓ of the distance (L 1 ) between the connection position and the upper end edge and not greater than ⅔ of the distance (L 1 ). The connection position at which the side wall  11  is connected to the flange  16  is the position of the upper surface of the flange  16 . When the height of the upper surface of a portion opposing the lower end of the side wall  21  of the cap  2  is higher than the height of the upper surface of a portion outward of this portion as shown in  FIGS. 4A and 4B , the connection position is the position of the upper surface of the portion opposing the lower end of the side wall  21  which portion is the higher portion. In addition, the lower end position at which the external screw  12  is formed may not be exactly the connection position at which the side wall  11  is connected to the flange  16 . For example, as a matter of course, a portion of the external screw  12  which portion is in a range where the external screw  12  cannot be engaged with the internal screw  22  may not be formed. In this case, the lower end position of the external screw  12  may be a position higher than the connection position with the flange  16  by about 1 pitch of the screw thread. 
     Overrun that the external screw  12  and the internal screw  22  climb over each other is likely to occur by the internal screw  22  being pushed inward in the case where the rigidity of the stopper body  1  is lower than the rigidity of the cap  2 , and such overrun is likely to occur by the cap  2  being pressed and widened outward in the case where the rigidity of the stopper body  1  is higher than the rigidity of the cap  2 . In order to inhibit such overrun, the rigidity of the stopper body  1  and the cap  2  is preferably set as follows. For example, the rigidity of the material used for the cap  2  may be higher than the rigidity of the material used for the side wall  11  of the stopper body  1 . For example, a polypropylene resin or a high-density polyethylene resin may be used as the material of the cap  2 , and a low-density polyethylene resin may be used for the side wall  11  of the stopper body  1 . In addition, preferably, the flexural modulus of the material of the cap  2  is, for example, not less than 1000 MPa and not greater than 1500 MPa, and the flexural modulus of the material of the side wall  11  of the stopper body  1  is, for example, not less than 100 MPa and not greater than 200 MPa. If the flexural modulus of the material of the cap  2  is less than 1000 MPa, the cap  2  easily deforms. Thus, when an excessive rotation load is applied to the cap  2 , the diameter of the internal screw  22  increases, so that the internal screw  22  easily climbs over the external screw  12  to cause overrun. In addition, if the flexural modulus of the material of the cap  2  is greater than 1500 MPa, the inner ring  25  is less likely to elastically deform, and creep deformation of the inner ring  25  occurs, so that the sealability decreases. If the flexural modulus of the material of the side wall  11  of the stopper body  1  is less than 100 MPa, the side wall  11  easily deforms. Thus, the internal screw  22  easily pushes the side wall  11  of the stopper body  1  inward, so that the internal screw  22  climbs over the external screw  12  to cause overrun. In addition, if the flexural modulus of the material of the side wall  11  is greater than 200 MPa, the side wall  11  is less likely to deform and has a certain degree of strength, so that it is difficult to pull out the partition  104  with the pull ring  103  to form an opening. 
     Since the external screw  12  is provided in the range from the connection position at which the side wall  11  is connected to the flange  16  to the distance that is not less than ⅓ of the distance (L 1 ) between the connection position and the upper end edge and not greater than ⅔ of the distance (L 1 ), that is, in a range close to a lower portion of the side wall  11  in which range the rigidity is increased by the flange  16  and the partition  104 , even when the external screw  12  is pushed by the internal screw  22 , the side wall  11  can be less likely to deform inward, and overrun can be less likely to occur. 
     In the case where the range where the external screw  12  is formed is a range from the connection position at which the side wall  11  is connected to the flange  16  to a distance from that is less than ⅓ of the distance (L 1 ) between the connection position and the upper end edge of the side wall  11 , the external screw  12  is brought into engagement with the internal screw  22  of the cap  2  only at a lower end portion of the cap  2  in which lower end portion the diameter easily increases, and also the number of turns of the external screw  12  is reduced, so that sufficient engagement is less likely to be achieved. In addition, in the case where the range where the external screw  12  is formed is a range from the connection position at which the side wall  11  is connected to the flange  16  to a distance that is greater than ⅔ of the distance (L 1 ) between the connection position and the upper end edge of the side wall  11 , the portion of the side wall  11  on which portion the external screw  12  is not formed is shortened, and thus no longer sufficiently serves as a guide for causing the rotation axis of the cap  2  and the screw axis of the screw to coincide with each other in inserting the cap  2  to the stopper body  1 , so that the screws are less likely to be properly engaged with each other. 
     The stopper body  1  that is produced by injection molding may be tapered so as to spread from the upper end to the lower end of the side wall  11 , in order to improve pulling-out of the stopper body  1  from a mold. Thus, the thickness of the side wall  11  is larger at the lower end than at the upper end, and the rigidity of the side wall  11  is higher at the lower end side. Therefore, in the case where the stopper body  1  is tapered, when the external screw  12  of the stopper body  1  is formed in the above-described range, an effect of inhibiting occurrence of overrun is obtained also by the taper. Similarly, the cap  2  may be tapered so as to spread from the upper end thereof toward the lower end thereof. In this case as well, when the range where the external screw  12  is formed is a range from the connection position at which the side wall  11  is connected to the flange  16  to a distance that is not less than ⅓ of the distance (L 1 ) between the connection position and the upper end edge of the side wall  11 , the screws are sufficiently in mesh with each other, and occurrence of overrun can be inhibited. 
     In a spout stopper according to the conventional art, a method of increasing the number of turns of an external screw on a side wall is adopted in order to enhance the rigidity of the side wall to inhibit overrun. However, in the present embodiment, by forming the external screw  12  in the above-described range, occurrence of overrun can be inhibited. Thus, the number of turns of the external screw  12  on the side wall can be made smaller than that in the conventional art. Thus, as compared to the conventional spout stopper, the user of the spout stopper  3  can easily threadedly engage or disengages the cap  2  with a smaller number of rotations. 
     At the upper end side of the side wall  11 , a region where the external screw  12  is not formed is increased. As a result, this region serves as a guide in fitting the cap  2 , so that threaded attachment/threaded engagement of the cap  2  along the screw axis becomes easy. In addition, even when the content liquid adheres to this region, the content liquid is easily wiped off. 
     The embodiment of the present invention will be described further with reference to  FIGS. 5A, 5B, 6A, 6B, 6C and 6D . 
       FIG. 5A  shows a cross-sectional view of the spout stopper  3  in a state where the cap  2  is in threaded engagement, and  FIG. 5B  shows an enlarged view of a main part thereof. The stopper body  1  includes a guide portion  113  that is a region at the upper end side with respect to the external screw  12  and on which no external screw is formed. 
     As shown in  FIG. 5B , the distance (L 3 ) along the screw axis direction between an internal screw portion formation start position that is the upper end of the internal screw  22  and an internal screw portion formation end position that is the lower end of the internal screw  22  is shorter than the length (L 4 ) of the guide portion  113  that is the distance from the upper end edge of the side wall  11  of the stopper body  1  to an external screw portion formation start position at the upper end side of the external screw  12 . 
     Alternatively, as shown in (c) of  FIG. 6 , in a state where the cap  2  is fitted to the side wall  11  of the stopper body  1  along the screw axis, the distance (D 1 ) between the inner circumferential surface  23  of the side wall  21  of the cap  2  and the screw thread ridge of the external screw  12  formed on the side wall  11  of the stopper body  1  is shorter than the distance (D 2 ) between the screw thread ridge of the internal screw  22  of the cap  2  and an outer circumferential surface  18  of the guide portion  113 . 
       FIGS. 6A, 6B, 6C and 6D  show cross-sectional views each showing a state where the cap  2  is being threadedly attached to the side wall  11  of the stopper body  1 . 
     Initially, the user puts the cap  2  on the side wall  11  of the stopper body  1  from the upper end ( FIG. 6A ). At this time, the attitude of the cap  2  may be tilted relative to the screw axis direction due to contact between the projection  15  and the internal screw  22 , etc. 
     Next, the user starts insertion of the cap  2  toward the screw axis direction ( FIG. 6B ). At the illustrated stage, the internal screw  22  and the external screw  12  are not in contact with each other. In addition, since the internal screw  22  faces the guide portion  113 , if an amount of tilt of the cap  2  is greater than a predetermined amount, the internal screw  22  receives resistance by coming into contact with the guide portion  113 , and the amount of tilt of the cap  2  is gradually reduced with advance of the insertion. 
     The guide portion  113  may include, at the lower end side with respect to the projection  15 , a portion having an outer diameter increasing toward the external screw  12 . For example, the guide portion  113  may include: a first outer diameter portion  13  formed at the lower end side of the projection  15 ; and a second outer diameter portion  14  that is formed at the lower end side of the first outer diameter portion  13  and at the upper end side of the external screw  12  and has a larger outer diameter than the first outer diameter portion  13 . In this case, after moving past the first outer diameter portion  13 , the lower end of the cap  2  moves past the second outer diameter portion  14  having a larger outer diameter. Thus, at start of insertion of the cap  2 , the cap  2  can be easily inserted since the distance between the lower end of the cap  2  and the first outer diameter portion  13  is large, and during subsequent advance of the insertion, the amount of tilt of the cap  2  can be smoothly reduced since the distance between the lower end of the cap  2  and the second outer diameter portion  14  is small. 
     The user continues to insert the cap  2  to a position at which the inner circumferential surface  23  of the side wall  21  of the cap  2  faces the screw thread ridge of the external screw  12  of the side wall  11  of the stopper body  1  ( FIG. 6C ). Since the tilt of the cap  2  has been reduced, the insertion smoothly advances. Even if the tilt has not been completely eliminated, when the inner circumferential surface  23  moves past the screw thread ridge of the external screw  12 , the inner circumferential surface  23  comes into contact with the screw thread ridge to receive resistance. Substantially simultaneously with this, the screw thread ridge of the internal screw  22  comes into contact with the outer circumferential surface  17  at the second outer diameter portion  14  to receive resistance. Because of these facts, the amount of tilt of the cap  2  is further reduced with advance of the insertion. 
     The user continues to insert the cap  2  to a position at which the lower end side of the internal screw  22  is in contact with the upper end side of the external screw  12  ( FIG. 6D ). Accordingly, the internal screw  22  and the external screw  12  are in contact with each other. At this stage, the tilt of the cap  2  relative to the side wall  11  has been eliminated. Thus, when the user rotates the cap  2 , the cap  2  and the side wall  11  of the stopper body  1  can be easily brought into threaded engagement with each other without occurrence of a threaded engagement failure. 
     In the spout stopper according to the present embodiment, the distance (L 3 ) between the formation start position, which is the upper end of the internal screw  22 , and the formation end position, which is the lower end of the internal screw  22 , is shorter than the guide portion length (L 4 ), which is the distance from the upper end edge of the side wall  11  of the stopper body  1  to the formation start position at the upper end side of the external screw  12 . Thus, a distance (L 4  or longer) of insertion of the cap  2  from the time when the lower end of the cap  2  moves past the vicinity of the upper end of the side wall  11  of the stopper body  1  to the time when the internal screw  22  of the cap  2  and the external screw  12  of the side wall  11  of the stopper body  1  come into contact with each other can be longer than a distance (about L 3 ) of movement of the cap  2  occurring with subsequent advance of threaded engagement. That is, after the insertion of the cap  2  advances such that the tilt of the cap  2  is assuredly reduced, the internal screw  22  of the cap  2  and the external screw  12  of the side wall  11  of the stopper body  1  can be brought into mesh with each other. In addition, since the distance of insertion is long, the user can be prevented from erroneously determining contact between the projection  15  and the internal screw  22  as contact between the external screw  12  and the internal screw  22  when the projection  15  and the internal screw  22  come into contact with each other at start of insertion, and starting rotation of the cap  2  to cause a threaded engagement failure. 
     In the spout stopper according to the present embodiment, the distance (D 2 ) between the screw thread ridge of the internal screw  22  of the cap  2  and the outer circumferential surface  17  of the guide portion  113  is preferably longer than the distance (D 1 ) between the inner circumferential surface  23  of the side wall  21  of the cap  2  and the screw thread ridge of the external screw  12  formed on the side wall  11  of the stopper body  1 . Accordingly, as shown in  FIG. 6C , it is possible to perform alignment of the screw axes with high accuracy (accuracy D 1 ) by interference between the lower end of the cap  2  and the internal screw  22  of the side wall  11  of the stopper body  1 . In addition, undesired interference with the side wall  11  of the stopper body  1  can be inhibited at a location other than the lower end of the cap  2  by a certain clearance D 2  (&gt;D 1 ), and thus it is possible to more smoothly bring the external screw  12  and the internal screw  22  into mesh with each other in bringing the external screw  12  and the internal screw  22  into threaded engagement with each other. 
     In the case where each screw portion is formed as a multiple-thread screw, multiple screw threads simultaneously start coming into mesh with each other at time of threaded engagement. Thus, in general, with the multiple-thread screws, an allowable value for an amount of tilt of the cap for preventing occurrence of a threaded engagement failure is smaller as compared to the case with single-thread screws. Therefore, a particularly significant effect is obtained when the present invention is used for a spout stopper in which multiple-thread screws are formed. 
     Even if the cap and the upper end of the side wall come into contact with each other to tilt the cap in fitting the cap to the side wall, this tilt can be corrected. Thus, limitation on the shape of the upper end of the side wall is reduced. For example, a projecting amount of the projection for preventing running-down of liquid can be increased within the range of the inner diameter of the cap, and the outer diameter of the upper end of the side wall can be larger than the outer diameter of the external screw. 
     The embodiment of the present invention will be described further with reference to  FIGS. 7, 8A, 8B, and 8C .  FIG. 7  shows a cross-sectional view of the stopper body  1 .  FIG. 8A  shows a bottom view of the stopper body  1 ,  FIG. 8B  shows an enlarged view of ribs  108 , and  FIG. 8C  shows a cross-sectional view of the rib  108  taken along a line B-B′ (see  FIG. 8B ) in the circumferential direction. The cross-section shown in  FIG. 7  is a vertical cross-section along a line A-A′ shown in  FIG. 8A . 
     The stopper body  1  includes: the cylindrical side wall  11 ; the partition  104  that closes the interior of the side wall  11  and has a half-cut  141  formed in an outer peripheral portion thereof; the disc-shaped flange  16  that is provided so as to extend outward from the lower end edge of the side wall  11 ; a groove-shaped cut-off portion  18  that is provided on a surface of the flange  16  opposite to the side wall  11  so as to be concentric with the side wall  11 ; and a plurality of ribs  108  that are provided on the inner surface of the cut-off portion  18 . Here, the lower end of the side wall  11  refers to the lower side in the sheet of  FIG. 1 . As shown in  FIG. 7  and  FIG. 8A , three projections  119  are formed on the side wall  11  at the upper end side with respect to the flange  16  at circumferentially equal intervals so as to project outward from the side wall  11 . The number of the projections  119  may be larger than three. 
     The partition  104  is connected to the side wall  11  via the half-cut  141  formed annually by decreasing the thickness of the outer periphery. The pull ring  103  is connected to the partition  104  via a pillar. The user of the stopper body  1  can pull the pull ring  103  upward to break the partition  104  along the half-cut  141  and pull out the partition  104  from the side wall  11 , thereby causing the upper end side of the lower end side of the side wall  11  to communicate with each other to form an opening. 
     The flange  16  is a location where the container body  4  and the spout stopper  3  are joined to each other in producing the packaging container  5  including the container body  4  and the spout stopper  3  mounted on the container body  4  as shown in  FIG. 2 . As the joining method, ultrasonic welding may be used. 
     To ultrasonically weld the spout stopper  3  to the container body  4 , the side wall  11  of the stopper body  1  is initially inserted into an opening of the container body  4  from the inner surface side such that the upper surface of the flange  16  is brought into contact with the inner surface of the container body  4  as shown in  FIG. 7 . At this time, the stopper body  1  is provisionally held to the container body  4  by interposing, between the projections  119  and the flange  16 , a portion surrounding the opening of the container body  4 . Then, an anvil and an ultrasonic horn (both are not shown) that have been inserted into the interior (inner side) of the container body  4  are brought into contact with the container body  4  that has overlapped the flange  16 , and ultrasonic vibration is generated to weld the container body  4  and the flange  16  to each other. The vibration generated at this time is transmitted from the flange  16  through the side wall  11  to the partition  104  but a part of the vibration is absorbed by the cut-off portion  18 . 
     The cut-off portion  18  is a groove that is provided on the surface of the flange  16  opposite to the side wall  11  so as to be concentric with the outer periphery of the side wall  11 . The cross-section of the cut-off portion  18  is, for example, an inverted-U shape (dome shape) that is resistant to ultrasonic vibration and has a rounded top surface as shown in  FIG. 7 . The cut-off portion  18  inhibits (disperses) propagation of the ultrasonic vibration to the partition  104 , thereby preventing occurrence of a crack in the half-cut  141  of the partition  104 . 
     As shown in  FIGS. 8A, 8B and 8C , the ribs  108  are provided so as to be aligned on the inner circumferential surface of the cut-off portion  18 . In this case, a length L 5  of each of the plurality of ribs  108  (the circumferential length of the rib  108  at the center of the groove width of the cut-off portion  18 ) along the circumferential direction of the cut-off portion  18  is preferably not less than 0.3 mm, and is further preferably not less than 0.5 mm since production of a mold becomes easy. In addition, L 5  is preferably not greater than 1.5 mm. An interval L 6  between the ribs  108  adjacent to each other (the circumferential length between the ribs  108  adjacent to each other at the center of the groove width of the cut-off portion  18 ) is preferably within the range of not less than 0.5 mm and not greater than 5.0 mm. By setting L 5  and L 6  within these ranges, desired rigidity can be ensured around the cut-off portion  18  while the cut-off portion  18  has a function to inhibit propagation of ultrasonic vibration. Therefore, occurrence of a crack in the half-cut can be inhibited, and deformation such as upward warpage of the outer edge of the flange  16  can be prevented. In addition, the energy of the ultrasonic vibration is absorbed and dispersed to a certain extent by the ribs  108 , so that co-vibration is inhibited near the flange  16  or the cut-off portion  18  of the side wall  11 , and unevenness of concentration of energy is eliminated. As a result, the flange  16  or the side wall  11  can be inhibited from deforming so as to wave. In the example shown in  FIGS. 8A, 8B and 8C , the entire circumference of the cut-off portion  18  is divided into 24 segments by 24 ribs  108 , and, for example, is preferably divided into 6 to 30 segments by 6 to 30 ribs. In the case where L 5  is shorter than 0.3 mm, or in the case where L 6  is longer than 5.0 mm, or in the case where the entire circumference of the cut-off portion  18  is divided into 5 or less segments, the proportion of a region filled with the ribs  108  in the entire circumference of the cut-off portion  18  is low, and sufficient rigidity is less likely to be ensured. In addition, in the case where L 5  is longer than 1.5 mm, or in the case where L 6  is shorter than 0.5 mm, or in the case where the entire circumference of the cut-off portion  18  is divided into 31 or more segments, the proportion of the region filled with the ribs  108  in the entire circumference of the cut-off portion  18  is high, so that an effect of inhibiting propagation of ultrasonic vibration is less likely to be obtained, and also the efficiency of molding decreases. Moreover, when L 5  and L 6  are made shorter than 0.5 mm, it is difficult to produce a mold, and when L 6  is made longer than 5 mm, the above-described warpage or waving occurs. 
     Due to the above, according to the present invention, it is possible to provide the spout stopper  3  that can inhibit each portion from deforming due to ultrasonic welding, and the packaging container  5  using the spout stopper  3 . Furthermore, the productivity can be improved by increasing vibration energy during ultrasonic welding and shortening a vibration cycle. Moreover, cost reduction can be achieved by decreasing the thickness of the half-cut  141 . 
     The shape of the cut-off portion  18  is not limited to the example shown in  FIGS. 8A, 8B and 8C .  FIG. 9A  shows a bottom view of a stopper body  1  according to a modification,  FIG. 9B  shows an enlarged view of ribs  108 , and  FIG. 9C  shows a cross-sectional view of the rib  108  taken along a line B-B′ ( FIG. 9B ) in the circumferential direction. In the example shown in  FIGS. 8A, 8B and 8C , the cross-sectional shape of the cut-off portion  18  along the line A-A′ is a rounded U shape as shown in  FIG. 7 . However, as in the example shown in  FIGS. 9A, 9B and 9C , the cross-sectional shape of the cut-off portion  18  may be a linear shape having a tapered surface and a substantially flat top surface. 
     Although the embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment, and can be carried out as a spout stopper obtained by combining some of the features of the above-described embodiment as appropriate, a spout stopper obtained by partially modifying the above-described embodiment, and packaging containers including these spout stoppers. 
     EXAMPLES 
     &lt;Evaluation 1&gt; 
     In order to check the sealing performance of the stopper body, a rotation torque was measured after a cap and a stopper body according to each of examples and reference examples were brought into threaded engagement with each other. Each reference example described later is a modification for verifying the individual effect of each favorable feature in the above-described embodiment, but does not necessarily depart from the scope of the present invention and can be taken as one embodiment having another feature of the present invention. 
     Example 1-1 
     As Example 1-1, the stopper body  1  according to the above-described embodiment shown in  FIGS. 1A and 1B , in which the projection  15  is formed at the upper end edge of the side wall  11  of the stopper body  1 , was used. 
     Reference Example 1-1 
     As Reference Example 1-1, a stopper body in which a shape corresponding to the projection  15  of the stopper body  1  is not formed was used. The others are the same as in the stopper body  1 . 
     (Test Method) 
     Samples of Example 1-1 and Reference Example 1-1 were prepared. An opening torque (N·cm) was measured immediately after each sample was set (the spout stopper was mounted onto a container body), immediately after a content liquid was filled (after 3 days from the setting, 70° C.), after 1 day from the filling, after 7 days from the filling, and after 14 days from the filling. The test results are shown in Table 1. 
     
       
         
           
               
               
               
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                 Opening torque 
                 Immediately 
                 After 
                 After 1 day 
                 After 7 days 
                 After 14 days 
               
               
                 (N · cm) 
                 after setting 
                 filling 
                 from filling 
                 from filling 
                 from filling 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                 Example 1-1 
                 Maximum 
                 71 
                 54 
                 51 
                 50 
                 50 
               
               
                   
                 Minimum 
                 54 
                 36 
                 35 
                 33 
                 34 
               
               
                   
                 Average 
                 62 
                 43 
                 41 
                 40 
                 41 
               
               
                 Reference 
                 Maximum 
                 75 
                 51 
                 48 
                 46 
                 45 
               
               
                 Example 1-1 
                 Minimum 
                 58 
                 35 
                 33 
                 31 
                 29 
               
               
                   
                 Average 
                 63 
                 40 
                 38 
                 37 
                 36 
               
               
                   
               
            
           
         
       
     
     From Table 1, it is found that regarding the stopper body according to Reference Example 1-1, the opening torque tends to decrease after the filling. On the other hand, regarding the stopper body  1  according to the example, a great decrease in the opening torque is not observed even after 14 days from the filling. From the results, it was confirmed that the stopper body  1  according to Example 1-1 can maintain a state where the cap is less likely to become loosened, over a long period of time as compared to the stopper body according to Reference Example 1-1, and thus has higher sealing performance. 
     &lt;Evaluation 2&gt; 
     Example 2-1 
     Example 2-1 of the present invention is the spout stopper  3  according to the above-described embodiment whose cross-sectional view is shown in  FIG. 4A . In Example 2-1, the external screw  12  is formed in a range from the connection position with the flange  16  to a height that is 60% of the distance between the connection position and the upper end edge. A polypropylene having a flexural modulus of 1470 MPa was used for the cap  2 , and a low-density polyethylene having a flexural modulus of 120 MPa was used for the stopper body  1 . 
     Example 2-2 
     In Example 2-2, the range where the external screw  12  is formed in Example 2-1 is changed, and the external screw  12  is formed in a range from the connection position with the flange  16  to a height that is 58.7% of the distance between the connection position and the upper end edge. L 1  described above was set to 12.70 mm, and L 2  described above was set to 7.45 mm. 
     Example 2-3 
     In Example 2-3, the range where the external screw  12  is formed in Example 2-1 is changed, and the external screw  12  is formed in a range from the connection position with the flange  16  to a height that is 55% of the distance between the connection position and the upper end edge. L 1  described above was set to 14.34 mm, and L 2  described above was set to 7.89 mm. 
     Reference Example 2-1 
     In Reference Example 2-1, the range where the external screw  12  is formed in Example 2-1 is changed, and the external screw  12  is formed in a range from the connection position with the flange  16  to a height that is 70% of the distance between the connection position and the upper end edge. 
     Reference Example 2-2 
     In Reference Example 2-2, the range where the external screw  12  is formed in Example 2-1 is changed, and the external screw  12  is formed in a range from the connection position with the flange  16  to a height that is 75% of the distance between the connection position and the upper end edge. 
     (Measurement of Overrun Occurrence Torque Value) 
     A torque by which overrun occurred was measured by using Examples 2-1 to 2-3 and Reference Examples 2-1 and 2-2. The cap was brought into threaded engagement with the side wall in an unused state, and a rotation load was applied until overrun occurred (the first time). After the overrun occurred, the threaded engagement of the cap was loosened, and a rotation load was applied again until overrun occurred (the second time). The measurement results obtained by carrying out this process for 10 spout stopper samples are shown in Table 2. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 2 
               
             
            
               
                   
                   
               
               
                   
                 First time (N · cm) 
                 Second time (N · cm) 
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                   
                 L2/L1 
                 Average 
                 Maximum 
                 Minimum 
                 Average 
                 Maximum 
                 Minimum 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                 Example 2-1 
                 0.60 
                 181.7 
                 188 
                 168 
                 171.1 
                 176 
                 166 
               
               
                 Example 2-2 
                 0.587 
                 181.4 
                 188 
                 168 
                 171.3 
                 176 
                 165 
               
               
                 Example 2-3 
                 0.55 
                 182.6 
                 190 
                 168 
                 171.8 
                 175 
                 168 
               
               
                 Reference 
                 0.70 
                 179.6 
                 187 
                 166 
                 174.3 
                 183 
                 163 
               
               
                 Example 2-1 
               
               
                 Reference 
                 0.75 
                 180.4 
                 189 
                 173 
                 166.5 
                 178 
                 155 
               
               
                 Example 2-2 
               
               
                   
               
            
           
         
       
     
     From the measurement results, it was confirmed that regarding Examples 2-1 to 2-3, the torque by which overrun occurred for the first time was higher, that is, overrun was less likely to occur, as compared to Reference Examples 2-1 and 2-2. In addition, a tendency that the torque by which overrun occurred for the second time decreased was observed in each case, but it was confirmed that regarding Examples 2-1 to 2-3, the amount of the decrease was smaller as compared to Reference Examples 2-1 and 2-2, and the torque value was similar to those of Reference Examples 2-1 and 2-2, so that overrun was not likely to occur as compared to Reference Examples 2-1 and 2-2. 
     (Evaluation of Liquid Leak at Occurrence of Overrun) 
     Performance regarding content liquid leak after occurrence of overrun was evaluated by using a packaging container to which each of Examples 2-1 to 2-3 and Reference Examples 2-1 and 2-2 was mounted. The partition of the stopper body according to each of Examples 2-1 to 2-3 and Reference Examples 2-1 and 2-2 was removed, and 1.8 liters of water was filled into the packaging container. Then, a rotation load was applied to the cap brought into threaded engagement with each side wall, until overrun occurred. The application of the load was stopped at the time when overrun occurred, and the cap and the spout stopper of the packaging container were directed downward to check presence/absence of water leak. Thereafter, the threaded engagement of the cap was loosened, then a rotation load by which overrun did not occur was applied this time to bring the cap into threaded engagement, and the cap and the spout stopper of the packaging container were directed downward with the cap being in threaded engagement, to check presence/absence of water leak. The evaluation results are shown in Table 3. 
     
       
         
           
               
               
               
               
             
               
                   
                 TABLE 3 
               
               
                   
                   
               
               
                   
                   
                 Number of cases 
                   
               
               
                   
                   
                 with liquid 
               
               
                   
                   
                 leak immediately 
                 Number of cases with liquid 
               
               
                   
                 L2/L1 
                 after overrun 
                 leak when tightening later 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
            
               
                 Example 2-1 
                 0.60 
                 9 out of 16 
                 0 out of 16 
               
               
                 Example 2-2 
                 0.587 
                 9 out of 16 
                 0 out of 16 
               
               
                 Example 2-3 
                 0.55 
                 9 out of 16 
                 0 out of 16 
               
               
                 Reference 
                 0.70 
                 8 out of 8 
                 0 out of 8 
               
               
                 Example 2-1 
               
               
                 Reference 
                 0.75 
                 8 out of 8 
                 0 out of 8 
               
               
                 Example 2-2 
               
               
                   
               
            
           
         
       
     
     From the evaluation results, it was confirmed that in Reference Examples 2-1 and 2-2, water leak was not prevented in all the cases in a state where overrun occurred, but in Examples 2-1 to 2-3, deformation of the side wall was small even in a state where overrun occurred, and water leak was prevented in 7 cases out of 16 cases, so that the sealability improved. In addition, it was confirmed that in each of Examples 2-1 to 2-3 and Reference Examples 2-1 and 2-2, water leak was prevented in all the cases by re-tightening the cap, and the examples can maintain sealability at substantially the same level by re-tightening after overrun, as compared to the conventional products. 
     &lt;Evaluation 3&gt; 
     Each of Examples 3-1 to 3-9 is the spout stopper  3  according to the above-described embodiment whose cross-sectional view is shown in  FIG. 5A , and L 3  and L 4  described above satisfy L 3 &lt;L 4 . In Reference Examples 3-1 and 3-2, L 3 &gt;L 4  is satisfied instead of L 3 &lt;L 4  in the spout stopper according to the embodiment. Among them, D 1  and D 2  described above satisfy D 1 &lt;D 2  in Examples 3-1, 3-2, 3-4, 3-5, 3-7, and 3-8 and Reference Examples 3-1 and 3-2, and satisfy D 1 &gt;D 2  in Examples 3-3, 3-6, and 3-9. In addition, in Examples 3-1, 3-4, and 3-7 and Reference Example 3-1, the guide portion was provided with a portion having an outer diameter increasing toward the lower end, and in Examples 3-2, 3-3, 3-5, 3-6, 3-8, and 3-9 and Reference Example 3-2, the guide portion was not provided with such a portion having an increasing outer diameter. 
     Whether insertion and threaded engagement of the cap to the stopper body smoothly advanced in each spout stopper without the cap being caught was evaluated. In the evaluation, ++ (excellent) was given when the number of times of smooth advance was 10 out of 10 trials, + (good) was given when the number of times was equal to or greater than 7, and poor (−) was given when the number of times was equal to or less than 6. The results are shown in Table 4. 
     
       
         
           
               
               
               
               
               
               
             
               
                   
                 TABLE 4 
               
               
                   
                   
               
               
                   
                   
                   
                   
                 Portion of guide 
                   
               
               
                   
                   
                   
                   
                 portion 
               
               
                   
                   
                   
                 Relationship 
                 having outer 
               
               
                   
                   
                   
                 between 
                 diameter 
               
               
                   
                 L3 
                 L4 
                 D1 and 
                 increasing 
                 Evaluation 
               
               
                   
                 (mm) 
                 (mm) 
                 D2 
                 toward lower end 
                 results 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                 Example 3-1 
                 3.5 
                 5.1 
                 D1 &lt; D2 
                 Presence 
                 ++ 
               
               
                 Example 3-2 
                 3.5 
                 5.1 
                 D1 &lt; D2 
                 Absence 
                 + 
               
               
                 Example 3-3 
                 3.5 
                 5.1 
                 D1 &gt; D2 
                 Absence 
                 + 
               
               
                 Example 3-4 
                 5.0 
                 6.5 
                 D1 &lt; D2 
                 Presence 
                 ++ 
               
               
                 Example 3-5 
                 5.0 
                 6.5 
                 D1 &lt; D2 
                 Absence 
                 + 
               
               
                 Example 3-6 
                 5.0 
                 6.5 
                 D1 &gt; D2 
                 Absence 
                 + 
               
               
                 Example 3-7 
                 5.0 
                 5.5 
                 D1 &lt; D2 
                 Presence 
                 ++ 
               
               
                 Example 3-8 
                 5.0 
                 5.5 
                 D1 &lt; D2 
                 Absence 
                 + 
               
               
                 Example 3-9 
                 5.0 
                 5.5 
                 D1 &gt; D2 
                 Absence 
                 + 
               
               
                 Reference 
                 5.7 
                 3.0 
                 D1 &lt; D2 
                 Presence 
                 − 
               
               
                 Example 3-1 
               
               
                 Reference 
                 5.7 
                 3.0 
                 D1 &lt; D2 
                 Absence 
                 − 
               
               
                 Example 3-2 
               
               
                   
               
            
           
         
       
     
     As shown in Table 4, the evaluation result was ++ or + in the case of L 3 &lt;L 4 , and the evaluation result was—in the case of L 3 &gt;L 4 . Therefore, the effect of the present invention was confirmed. In addition, in the case of L 3 &lt;L 4 , when D 1 &lt;D 2  was satisfied and the guide portion was provided with a portion having an outer diameter increasing toward the lower end, the evaluation result was ++, and this was confirmed as being more preferable. 
     INDUSTRIAL APPLICABILITY 
     The present invention can be used for stopper bodies for various packaging containers such as a packaging container made of paper, a PET bottle, a bottle, and a flexible packaging container. 
     DESCRIPTION OF THE REFERENCE CHARACTERS 
       1  stopper body 
       11  side wall 
       12  external screw 
       13  first outer diameter portion 
       103  pull ring 
       104  partition 
       108  rib 
       109  top surface 
       113  guide portion 
       119  projection 
       13  first outer diameter portion 
       14  second outer diameter portion 
       141  half-cut 
       15  projection 
       16  flange 
       17  outer circumferential surface 
       18  cut-off portion 
       19  inner circumferential surface 
       2  cap 
       21  side wall 
       22  internal screw 
       23  inner circumferential surface 
       24  top plate 
       25  inner ring 
       26  thick portion 
       27  contact surface 
       28  contact portion 
       3  spout stopper 
       4  container body 
       5  packaging container