Thread formation for closure structures

摘要

A closure structure which includes a container neck having an external thread to be engaged by an internal thread of a closure body for drawing the closure body tightly down onto the container neck. The external thread of the container neck includes a pad on a bottom thread turn. A sealing element of the closure body is drawn downwardly onto a sealing surface of the container neck to effect a seal. The pad is sized to have a depth which causes the internal thread of the closure body to be drawn downwardly during the final portion of the screwing-on of the closure body to the container neck. The presence of the pad reduces axial clearance between the external thread of the container neck and the internal thread of the closure body to prevent axial displacement of the closure body from the container neck to prevent leakage due to the sealing element of the closure body being axially displaced from the sealing surface of the container neck.