| 摘要 |
<p>Appts. for heat sealing the tops of thermoplastic bottles comprises a heated hollow metal cylinder with a bore having a convergent entry sized so that the mouth of the entry is larger than the outside dia. of the bottle neck, but the bore is smaller. The cylinder is located on the bottle neck, heated to melt the adjacent bottle mouth, and loaded with a weight to cause the cylinder to descend until stopped by a collar at the base of the neck. The bore is narrow enough to cause the bottle neck to converge and fuse solid. Pref. the cylinder is of metal which is a good conductor e.g. bronze, and heated by a coaxial induction coil. Used for sealing containers required to withstand rough storage and long shelf life, e.g. agricultural chemicals. One application is sealing of polyethylene bottles contg. potash. The seal is more secure than threaded or snap fit closures. There is no risk of melt droplets being dislodged into the bottle contents, unlike use of hot probes to fuse the inner wall of the bottle neck to receive a welded plug.</p> |
