Spout stopper and packaging container

1. A spout stopper comprising:

a stopper body including a cylindrical side wall having an external screw formed on an outer circumferential surface thereof; and

a cap to be mounted from an upper end side that is one end of the side wall of the stopper body, the cap including a top surface and a side wall having an internal screw formed on an inner circumferential surface thereof, the external screw and the internal screw being configured to be brought into threaded engagement with each other, wherein

a projection is formed at an upper end edge of the side wall of the stopper body so as to project outward from the side wall of the stopper body,

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,

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, and

in a state where the cap is threadedly attached to the side wall of the stopper body, a top surface at the upper end of the side wall of the stopper body and an upper surface of the projection are in surface contact with an inner surface of the top surface of the cap over an entire circumference thereof, and an outer circumferential edge of the projection is in contact with the inner circumferential surface of the side wall of the cap.

2. The spout stopper according to claim 1 , wherein

in the state where the cap is threadedly attached to the side wall of the stopper body,

the side wall of the stopper body becomes elastically deformed, and the top surface at the upper end of the side wall of the stopper body is in surface contact with the cap at a certain contact pressure.

3. The spout stopper according to claim 1 , wherein a material of the cap has higher rigidity than a material of the side wall of the stopper body.

4. The spout stopper according to claim 1 , wherein the material of the cap has higher rigidity than a material of the stopper body.

5. The spout stopper according to claim 1 , wherein

the material of the cap is a polypropylene resin or a high-density polyethylene resin, and

the material of the stopper body is a low-density polyethylene resin.

6. The spout stopper according to claim 1 , wherein

the cap includes an inner ring that is fitted to an inner circumferential surface of the side wall of the stopper body to seal the side wall of the stopper body in the state where the cap is threadedly attached to the side wall of the stopper body, and

an upper end portion of the side wall of the stopper body is in surface contact with the cap over an entire circumference thereof between the inner ring and the side wall of the cap in the state where the cap is threadedly attached to the side wall of the stopper body.

7. The spout stopper according to claim 1 , wherein at least one of the side wall of the stopper body and the side wall of the cap is tapered so as to spread from an upper end thereof toward a lower end thereof.

8. The spout stopper according to claim 1 , wherein

the outer circumferential surface of the side wall of the stopper body includes an external screw portion on which the 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, and

a distance along the 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 of the stopper body to a formation start position at an upper end side of the external screw portion.

9. The spout stopper according to claim 8 , wherein the guide portion includes, at a lower end side with respect to the projection, a portion having an outer diameter increasing toward the external screw portion.

10. The spout stopper according to claim 8 , wherein, in a state where the cap is fitted to the side wall of the stopper body along the screw axis, a distance between a screw thread ridge of the internal screw of the cap and an outer circumferential surface of the guide portion is longer than a distance between the inner circumferential surface of the cap and a screw thread ridge of the external screw portion of the side wall of the stopper body.

11. The spout stopper according to claim 1 , further comprising:

a partition closing an interior of the side wall of the stopper body and having a half-cut formed at an outer peripheral portion;

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 of the stopper body; 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.

12. The spout stopper according to claim 11 , wherein each of the plurality of ribs has a length, along the circumferential direction of the cut-off portion, of not less than 0.3 mm and not greater than 1.5 mm.

13. The spout stopper according to claim 11 , wherein each of the plurality of ribs has a length, along the circumferential direction of the cut-off portion, of not less than 0.5 mm.

14. The spout stopper according to claim 11 , wherein at least three projections are formed on the side wall of the stopper body at an upper end side with respect to the flange at circumferentially equal intervals so as to project outward.

15. The spout stopper according to claim 1 , wherein the external screw and the internal screw are multiple-thread screws.

16. A packaging container comprising:

a container body; and

the spout stopper according to claim 1 , the spout stopper being mounted on the container body.

17. A spout stopper comprising:

a stopper body including a cylindrical side wall having an external screw formed on an outer circumferential surface thereof; and

a cap to be mounted from an upper end side that is one end of the side wall of the stopper body, the cap including a top surface and a side wall having an internal screw formed on an inner circumferential surface thereof, the external screw and the internal screw being configured to be brought into threaded engagement with each other, wherein

a projection is formed at an upper end edge of the side wall of the stopper body so as to project outward from the side wall of the stopper body,

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,

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, and

in a state where the cap is threadedly attached to the side wall of the stopper body, an upper surface of the side wall of the stopper body and an upper surface of the projection are in contact with an inner surface of the top surface of the cap over an entire circumference thereof, and an outer circumferential edge of the projection is in contact with the inner circumferential surface of the side wall of the cap.