Method for the treatment of rigid plastic containers

摘要

A method and an apparatus for treating mouth areas of rigid plastic containers in order to prevent cracking during the capping of the containers. The width of the mouth opening of the container is prior to capping temporarily increased by means of a mandrel, which at a relatively low speed is introduced into the mouth opening. This results in a cold working and stretching of the plastic material adjacent to the opening and when the mandrel after a short while is with-drawn from the mouth opening the plastic material around the same is given a molecular orientation in the circumferential direction. The preferred apparatus includes fixing elements for holding a container so that its mouth opening is aligned with the mandrel, which is cylindrical with a somewhat greater diameter than the mouth opening and axially displaceable into the mouth opening.