Patent ID: 6254523
Filing Date: 2001-07-03
Classification: B31F,Y10S

Abstract:
A method of imparting directional permanency of folding to a sheet, having parallel opposing edges extending along a longitudinal dimension of the sheet and a plurality of pairs of parallel ruled folding lines which are orthogonal to the longitudinal dimension, by forming ridge-like and valley-like folds in the sheet, said method comprising the steps of:a first step of conveying the sheet along a linear path extending to and including a planar working position;a second step of disposing pairs of folding working tools in initial positions aligned with corresponding pairs of the respective ruled folding lines on a surface of the sheet which becomes an inner surface when the sheet is folded along the respective ruled folding lines;a third step of moving said pairs of folding working tools perpendicular to the planar working position to engage and fold the sheet along the respective pairs of the ruled folding lines;a fourth step of shifting the folding working tools engaging the sheet, parallel to the linear path, to shorten distances between the respective pairs of the folding working tools in accordance with a ratio based on an apparent amount of shortening of the longitudinal dimension caused by the shifting, in synchronization with the third step;a fifth step of retracting the respective pairs of the folding working tools from the sheet after the fourth step;a sixth step of returning the respective pairs of the folding working tools to their initial positions; andrepeating the first through the sixth steps; andwherein the sheet is a corrugated cardboard, and at least some of the ruled lines are intermittent cutting lines formed by cutting the sheet intermittently across corrugations and are each composed of cuts of a predetermined length formed in the sheet and non-cut portions of a shorter length than the predetermined length, said cuts and non-cut portions alternating across one dimension of the corrugated cardboard, transverse to the corrugations, and, extending obliquely from each end of each cut, an additional cut of a shorter length then said predetermined length.