| 摘要 |
Preform which can be folded alone a zone to a container is produced by gripping a sheet between a female die and a complementary male die so that thd folding zone of the preform lies on the top of a V-shaped part separating the two dies, the top angle of the V-shaped part being increased before or at the beginning of the movement of the dies towards each othter, and then decreased to its original value after the dies have contacted. Extra and deviating elongation during the formation of the V-shaped zone is avoided. The mechanical strength of the preform at the folded part is the same as at the other parts. |
