Synthetic resin cap, closing device, and container-filled beverage

1. A synthetic resin cap, comprising:

a cap body having a top plate and a cylindrical section extending downward from the periphery thereof and having, in an inner peripheral surface thereof, a threaded section that engages with a thread of a container opening; and

a circular inner seal projection formed integrally with the cap body on an inner surface of the top plate and fitting into the container opening, wherein

an angle of circumference along which the threaded section is formed is from 680° to 720°;

the threaded section is divided by dividing sections into a plurality of divided threaded sections each having substantially an equal circumferential formation angle;

the dividing sections are provided around an entire circumference of the threaded section at substantially equal intervals selected from 45° to 90° in the circumferential direction; and

the divided threaded section which is immediately below the divided threaded section at the nearest position to the top plate and the divided threaded section which is immediately above the divided threaded section at the farthest position from the top plate are formed continuously by a connecting section which has substantially the same circumferential formation angle as that of the dividing sections.

2. The synthetic resin cap according to claim 1 , wherein a circular opening edge seal projection that contacts an opening edge of the container opening is formed on the top plate, and, when the synthetic resin cap is attached to the container opening, the opening edge seal projection is made able to bend and be deformed in the expanding radial direction until it contacts the cap body.

3. A closing device, comprising:

a container having a container opening; and

a synthetic resin cap fitted in the container opening and having:

a cap body having a top plate and a cylindrical section extending downward from a periphery thereof and having, in an inner peripheral surface thereof, a threaded section that engages with a thread of the container opening; and

a circular inner seal projection formed integrally with the cap body on an inner surface of the top plate and fitting into the container opening, wherein

an angle of circumference along which the threaded section is formed is from 680° to 720°;

the threaded section is divided by dividing sections into a plurality of divided threaded sections each having substantially an equal circumferential formation angle;

the dividing sections are provided around an entire circumference of the threaded section at substantially equal intervals selected from 45° to 90° in the circumferential direction; and

the divided threaded section which is immediately below the divided threaded section at the nearest position to the top plate and the divided threaded section which is immediately above the divided threaded section at the farthest position from the top plate are formed continuously by a connecting section which has substantially the same circumferential formation angle as that of the dividing sections.

4. A container-filled beverage in which a beverage is filled inside a closing device comprising:

a container having a container opening; and

a synthetic resin cap having:

a cap body having a top plate and a cylindrical section extending downward from a periphery thereof and having, in an inner peripheral surface thereof, a threaded section that engages with a thread of the container opening; and

a circular inner seal projection formed integrally with the cap body on an inner surface of the top plate and fining into the container opening, wherein

an angle of circumference along which the threaded section is formed is from 680° to 720°;

the threaded section is divided by dividing sections into a plurality of divided threaded sections each having substantially an equal circumferential formation angle;

the dividing sections are provided around an entire circumference of the threaded section at substantially equal intervals selected from 45° to 90° in the circumferential direction; and

the divided threaded section which is immediately below the divided threaded section at the nearest position to the top plate and the divided threaded section which is immediately above the divided threaded section at the farthest position from the top plate are formed continuously by a connecting section which has substantially the same circumferential formation angle as that of the dividing sections.

5. A synthetic resin cap according to claim 2 , further comprising a positioning protrusion protruded from the top plate on the outer surface side of the inner seal projection, and wherein the positioning protrusion contacts an opening edge of the container opening at the bottom face thereof.

6. The synthetic resin cap according to claim 1 , wherein a formation angle of a top surface of the threaded section with respect to the top plate is from 20° to 45°.

7. The synthetic resin cap according to claim 1 , wherein a protruding length of the inner seal projection is from 1 mm to 5 mm.

8. The synthetic resin cap according to claim 2 , wherein the opening edge seal projection includes:

an erect cylindrical section which extends substantially vertically downward from the inner surface of the top plate; and

an expanding cylindrical section which widens in diameter from a bottom edge of the erect cylindrical section.

9. The closing device according to claim 3 , wherein:

a diameter of the inner seal projection gradually increases in a protruding direction thereof; and

a maximum outer diameter of the inner seal projection is greater than an inner diameter of the container opening.