Screw-top bottle-can and method for producing the same
A method for producing a screw-top bottle-can and a screw-top bottle-can are provided so that a screw-thread can be formed without damaging an inner coating and a resealing operation can be improved. A shoulder part is formed by reducing a diameter of an opening part of a closed-end cylindrical body, a cylindrical part having an intermediate diameter between a major thread diameter and a minor thread diameter and a tapered part which is tapered from an upper end of the cylindrical part toward an opening-end part are formed above the shoulder part, and forming a screw-thread from the tapered part to the cylindrical part so as to form a starting part of the screw-thread at a middle part of the tapered part.
1. A method for producing a screw-top bottle-can, comprising:
forming a shoulder part by reducing a diameter of an opening part of a closed-end cylindrical body;
forming a cylindrical part having an intermediate diameter between a major diameter and a minor diameter of a screw-thread and a tapered part which is tapered from an upper end of the cylindrical part toward the opening-end part above the shoulder part; and
forming the screw-thread from the tapered part to the cylindrical part so as to form a starting part of the screw-thread at a middle of the tapered part, so that the tapered part is formed to have a maximum outer diameter which is equal to or smaller than the minor diameter of a groove portion which is adjacent to a first ridge of the screw-thread.
2. The method for producing a screw-top bottle-can according to claim 1 , wherein
in a vertical section along a can-axis direction at the starting part of the screw-thread,
the screw-thread is formed so that a bend part between the tapered part and the cylindrical part is arranged in a region between a second ridge of the screw-thread and a groove portion above the second ridge.
3. The method for producing a screw-top bottle-can according to claim 1 , wherein the tapered part is inclined at 10° to 30° with respect to a can-axis direction.
4. The method for producing a screw-top bottle-can according to claim 2 , wherein the tapered part is inclined at 10° to 30° with respect to the can-axis direction.
5. A screw-top bottle-can which is produced by the method for producing according to claim 1 .
6. A screw-top bottle-can according to claim 1 , wherein the tapered part extends from the groove portion.
7. A screw-top bottle-can according to claim 1 , wherein the tapered part and the groove portion together define a concave outer surface.
8. A screw-top bottle-can according to claim 7 , wherein the maximum outer diameter of the tapered part is smaller than the minor diameter of the groove portion adjacent the first ridge of the screw-thread.
9. A screw-top bottle-can according to claim 1 , wherein the maximum outer diameter of the tapered part is smaller than the minor diameter of the groove portion adjacent the first ridge of the screw-thread.