| 摘要 |
A moulded screw-cap for a container has a plurality of screw-thread ridges 24 formed internally of the skirt 19 of the cap each ridge having helical first portion 25 extending away from the top 18 and a second portion 26 of substantially zero helix angle. The circumferential distance A between the nose 28 of portion 26 and the line 29 of the lower face of portion 25 of each ridge 24 is less than the circumferential distance between the thread ridges on the container. A transition portion 27 is provided between portions 25 and 26 and, during application of the cap to a container allows the portions 26 to drop into the gaps between adjacent thread ridges on the container sufficiently to bring the upper surfaces of portion 26 into correct position for engagement with complementary inclined surfaces of the projections on the container, so that no downward pressure need be applied to the cap.
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