Accurately placed stress concentrating aperture in flexible packages

摘要

An "easy open" feature for a sealed flexible pouch and method and apparatus for accurately positioning said feature in the sealed border region of said flexible pouch. The feature comprises a stress concentrating aperture exhibiting a strong tendency to initiate a directional tear while maintaining integrity of the sealed pouch until an opening force is applied. In a preferred embodiment the pouches are cut from a moving web by a rotary shear cutter while a web punching means operatively connected with each cutter blade is engaged in the moving web. Because the web undergoes no movement relative to the cutting means or the punching means until both operations have been completed, the aperture is precisely positioned with respect to the severed edge of the pouch. In a particularly preferred embodiment, the sealed edge of the pouch is subjected to a high level of tension and is unsupported in the area of contact with the punching means during the aperturing operation. This concentrates the stress applied by the punching means and helps to form an aperture in the seal, even where tough and/or stretchy pouch materials which are prone to stretch and deform rather than rupture are employed. While the precise shape of the aperture is not critical, it is preferably non-circular in order to provide at least one area of stress concentration within the aperture and thereby facilitate tearing at relatively low levels of applied stress.