| 主权项 |
1. A manufacturing method of a screw-threaded bottle-can, comprising:
an intermediate-formed product forming process forming an intermediate-formed product having a shoulder part which is gradually tapered upward from an upper end of a trunk part, a neck part which is extended upward from an upper end of the shoulder part having a cylindrical shape, a surplus-thickness part which is swelled out as a protrusion streak or swelled in as a recessed groove round an upper end part of the neck part, a pipe part which is extended upward from an upper end of the surplus-thickness part, and a tapered part which is tapered from an upper end of the pipe part toward an aperture-end part; and a screw-forming process using a screw-forming tool provided with: an inner mold having a right-hand screw-type protrusion and an inner-mold swell part swelling outward around a lower part of the right-hand screw-type protrusion; and an outer mold having a left-hand screw-type protrusion and an outer-mold swell part swelling outward around a lower part of the left-hand screw-type protrusion, arranging the inner mold inside the pipe part and the surplus-thickness part and arranging the outer mold outside the pipe part and the surplus-thickness part, interposing the surplus-thickness part and a vicinity of the pipe part between the inner mold and the outer mold, and rolling the screw-forming tool in the interposing state, in a circumferential direction of the pipe part while revolving in a left-hand direction by seeing from the aperture end toward a bottom part of the intermediate-formed product so that a screw-thread part and a jaw part swelling outward around a lower part of the screw-thread part are formed on the intermediate-formed product; wherein in the intermediate-formed product forming process, an outer diameter of the pipe part is formed to have an intermediate outer diameter between an outer diameter of a screw-ridge and an outer diameter of a screw-bottom of the screw-thread part after the screw-forming process; the screw-forming tool is provided to form larger clearances than a plate-thickness of the intermediate-formed product between the right-hand screw-type protrusion of the inner mold and a screw-bottom of the left-hand screw-type protrusion of the outer mold and between a screw-bottom of the right-hand screw-type protrusion of the inner mold and the left-hand screw-type protrusion of the outer mold in the interposing state in the screw-forming process; in the screw-thread part after the screw-forming process, an average height is set as “h” of the screw-ridge from the adjacent screw-bottom in a prescribed area including a maximum diameter part; a screw-starting part is set at a position of 0° in which a height of the screw-ridge from the adjacent screw-bottom is 0.5h above the screw-thread part; and a second-step starting part is set at a position of 360° from the screw-starting part; in the right-hand screw-type protrusion of the inner mold, a part forming the second-step starting part of the screw-thread part is set as a second-step-starting forming part; in the screw-forming process, the screw-forming tool and the intermediate-formed product are arranged so that a bend part between the tapered part and the pipe part in a vertical cross-section of the intermediate-formed product along a can-axis direction in the screw-starting part is arranged between a screw-ridge of the second-step-starting forming part of the inner mold and a screw-bottom above the screw-ridge; the screw-ridge is formed so that an outer diameter thereof is increased in a range of 360° from the screw-starting part to the second-step starting part, and so that a height of the screw-ridge from the adjacent screw-bottom is more than 0.5h and less than “h” in a range of 90° from the screw-starting part; and the screw-starting part is formed at an intermediate position of the tapered part of the intermediate-formed product, and the screw-thread part is formed from the tapered part to the pipe part. |
