Anti-spin interference fit of press-seal insert and method of assembly

Abstract

This relates to press-on closure assemblies for containers. It is known to provide containers which are formed of plastic or glass with a neck finish including an end sealing surface and a recessed, generally cylindrical, but possibly tapered, surface disposed between two opposed axially spaced shoulders. A separately formed insert is pressed over the neck finish and positioned between the two shoulders in opposed relation to the recessed surface of the neck finish. The insert has lugs or threads for interlocking engagement with a closure which may be removed by rotation. The closure and the insert are preassembled and pressed onto the container neck finish with a gasket or sealing material carried by the closure engaging the end sealing surface. The past problem is the rotation of the insert relative to the container neck finish, thereby preventing removal of the closure. It is proposed to form the insert of a thermoplastic resin and heating the insert immediately before the application thereof to the container neck finish. This results in softening of the insert facilitating its telescoping over the container neck finish. However, most particularly, the thermoplastic resin of the insert is heated to a temperature whereat a desired reaction takes place with the resultant shrinkage of the insert to a size less than the original size wherein in lieu of conventional non-reliable press fit, there is a shrink fit which is greater than is possible with the press fit.