Bottle can member, bottle, and thread forming device
An effective thread number in the thread section which is disposed on the mouth section of the bottle is formed to be 2.2. That is, the thread section is formed such that the thread section 13 should serve effectively in the mouth section such that an interval between a start position and an end position should be 2.0 to 2.5. In the bottle can member 11 which has such a thread section, an outer diameter of the thread section which is formed on the mouth section is 28 to 38 mm. Also, the thickness of the mouth section is 0.25 to 0.4 mm. The thread section which has the effective thread number 2.0 to 2.5 is formed by eight-thread per inch pitch. By doing this, it is possible to put the cap desirably.
1. A method for manufacturing a DI can member using a bottle can member produced by drawing and ironing a metal plate, comprising the steps of:
forming a mouth section by processing an aperture section of the bottle can member so as to reduce a diameter of the aperture section;
forming an enlarged-diameter section by processing the aperture section so as to enlarge the diameter of the aperture section by a predetermined distance from an end of the mouth section;
forming an expanding section for winding up a lower section of a cap main member by decreasing a diameter of a thread section where a thread is to be formed on the enlarged-diameter section;
forming the thread on the thread section where the thread is to be formed after forming the expanding section, wherein a plurality of threads are formed toward a can bottom direction from the end of the mouth section around an outer periphery of the mouth section of the bottle can member, and a height of a first thread which is disposed near the end of the mouth section of the bottle can member is set to be lower than a height of other threads in a predetermined angle range;
forming a curl section on an end of the mouth section after the thread is formed; and
axially compressing the mouth section during a step of putting a cap on said mouth section, which causes axial crushing of the first thread and radial expansion thereof so that the heights of all threads are approximately equal.
2. A method for manufacturing a DI can member according to claim 1 , wherein the predetermined angle range is a range within 90 degrees from a thread starting section of the thread section.