| 摘要 |
A cap for a jar, the cap being of sheet metal and (considered in its attitude of use) comprising a top panel (2), a skirt (4) depending from the periphery of the top panel, and an internal continuous circumferential bead (6) on the lower edge of the skirt. Hitherto such a bead has been deformed inwards at intervals to provide internal lugs to engage an interrupted thread, or a continuous bead, on a jar, but the lugs have not performed reliably. In the present cap the bead (considered in plan) consists of alternate arcuate portions (8) and straight portions (10), the arcuate portions being at a uniform radius from a common centre (12), and the straight portions being tangent to a common imaginary circle (14) around that common centre. Dies for the manufacture of the caps include inserts for shaping the straight portions (10). |
