The present invention relates to paperboard containers having a hinged lid.
Paperboard containers having hinged lids are conventional, such as so-called cigarette hard packs, as disclosed for example, in Focke et al U.S. Pat. No. 4,753,383, and which is depicted in the accompanying FIGS. 3-5. That container, designed to hold cigarettes, is erected from a cardboard blank to form a pack portion 6 and a lid 8 integrally hinged to the pack portion. A separate inner frame 10 is glued within the pack portion and projects beyond an upper edge thereof. The four vertical corners 12 of the container are of a rounded configuration. In order to provide sufficient friction between the pack portion and lid to keep the lid closed, the pack portion includes a pair of retention flaps 14 extending along the front corners 12 of the base.
Each retention flap 14 is formed by making a cut in a front corner of the inner frame such that the flap projects laterally beyond the corner. Outer edges 19 of those retention flaps are intended to bear against the inner faces of side walls 18 of the lid 8 to frictionally retain the lid in a fully closed condition. Each side wall 18 of the lid is comprised of outer and inner panels 20, 22 lying against one another. According to the disclosure of that patent, a front edge 24 of the inner panel engages behind the respective flap 14 so as to stress the latter toward a position in which the flap is projected laterally outwardly.
It has been observed that the outer edges 19 of the flaps, after a short period of use, become frayed which is undesirable from at least an aesthetic standpoint. That fraying is especially undesirable if the pack is of a type in which the flaps are overlaid with an outer foil layer of decorative (e.g., colored) material, because the fraying can result in a delamination of the foil layer.
The present inventor has realized that the fraying of the flap edge 19 is caused when a sharp corner defined by a lower end 26 of the front edge 24 (depicted in FIG. 5) rubs across the flap outer edge 19 each time that the lid 8 is opened and closed. That rubbing quickly causes a fraying and/or delamination of the retaining flaps.