METHOD FOR MOLDING OPENING CURL OF BOTTLE CAN WITH CAP

To provide a method for molding a curl, which can maintain sufficient rigidity and strength even when miniaturization such as thinning or reduction of an opening size is executed.SOLUTION: A diameter reduction process is performed so as to set an angle between an inclined wall part 5 and the center axis L0 of a screw cylindrical part within the range of 20°-30°. A process for drawing the tip edge 10 side of a bent part inside in a radial direction to butt it to the outer surface of the inclined wall part 5 is performed so as to set a size measured between the outermost diameter part 9 of a curl 1 and a place where the tip edge 10 butts the inclined wall part 5 in the radial direction within the range of 40%-60% of a curl width W which is half a difference between the outer diameter and the inner diameter of the curl 1 and the butting angle θ10 of the tip edge 10 to the inclined wall part 5 within the range of ±20°at the center of 90°.SELECTED DRAWING: Figure 1 【課題】薄肉化し、あるいは開口径を小さくするなどのいわゆる小型化した場合であっても、剛性や強度を十分に維持することのできるカール部の成形方法を提供する。【解決手段】傾斜壁部５とねじ円筒部の中心軸線Ｌ0との間の角度が２０度以上かつ３０度以下の範囲の角度となるように縮径加工し、湾曲させた部分の先端エッジ部１０側を半径方向で内側に巻き込ませて傾斜壁部５の外面に突き当てる加工は、カール部１の最外径部９と先端エッジ部１０が傾斜壁部５に突き当たっている箇所との間の半径方向で測った寸法が、カール部１の外径と内径との差の半分であるカール幅Ｗの４０％以上かつ６０％以下の範囲に入り、かつ先端エッジ部１０の傾斜壁部５に対する突き当て角度θ10が９０度を中心にした±２０度の範囲に入る角度となるように行う。【選択図】図１