Sheet folding method and apparatus utilizing convex folder and guide

摘要

An envelope blank is conveyed through a folding mechanism that folds one or more flaps of the blank. In folding a side flap the leading edge of the blank adjacent to the score line follows in a helical path a convex face of a plowshare. The plowshare face applies at the leading edge of the blank adjacent to the score line a force which bends the side flap through an angle of 180° to a position where the flap is folded to overlap the blank. The folding of the flap is initiated by the convex face of the plowshare so that the flap folding forces are applied to the score line where the flap has the least resistance to bending. The folding forces are removed from the flap free edge which is supported to follow the movement of the flap leading edge.