| 摘要 |
PROBLEM TO BE SOLVED: To make it easy to curve uniformly, prevent a large partial bend or the like, make a reverse turn smooth, and make the reverse turn and capping steady, by giving a plurality of stress-lessening parts, in which quadrangular holes and flat-quadratic-prism-shaped recesses are formed one after another in an area extending from the root of a locking ring to the peripheral edge of its front end. SOLUTION: The plastic cap 1 comprises a guarantee ring 12 continuing, via a bridge 10b, to the lower part of the cylindrical portion of a cap main body 10, and a skirtlike locking ring 12 extending downward from its peripheral edge. Also it is given a plurality of stress-lessening parts 30, in which quadrangular holes 30a and flat-quadratic-prism-shaped recesses are formed one after another in an area extending from the root 20a of the locking ring 20 to the peripheral edge 20b of the front end of it. Thus, in the peripheral edge 20b of the front end of the locking ring 20, quadrangular cuts by the flat-quadratic- prism-shaped recesses are made, and a part whose width is thinner than the width of the peripheral edge 20b of the front edge is formed. It lessens a stress applied when the locking ring 20 is turned reversely, increases the degree of freedom in curvature in reverse turn, and makes it easy to curve uniformly. |
