Interrupted thread cap structure

Abstract

A container neck is used with a tamper-evident, snap-on, screw-off closure. The neck has a multiple of four first helical threads on a neck stretch portion, and at least one external ratchet tooth on a locking wall portion below the neck stretch. The closure has an upper skirt having second helical threads mating with the first helical thread of the neck and a lower skirt with at least one internal ratchet tooth shaped and positioned to engage the external ratchet tooth when the closure is applied to the neck. The teeth formed on the skirt interior and neck exterior are arranged to provide at least one circumferentially extending stretch of the tamper-evident band where the teeth are not engaged. A line of weakness extending vertically through the disengaged stretch of the tamper-evident band is ruptured when the closure is unscrewed from the neck. The number of helical threads is preferably eight and, in any event, a multiple of four. In one modification the threads are interrupted and the gaps between thread segments are vertically aligned while in another modification the thread segments are staggered. In sill another modification there is a space where vertically aligned segments are omitted to provide space for the down-turned tab of a foil disc sealing the lip on the container. Where the container is made of PET or other accurately molded substance the points of the neck ratchet teeth are rounded to avoid injury to the user.