Method and device for creating a hinge-like bendable zone in a sheet of paper, paperboard, cardboard or foil

a,b, a,b a,ba,b, a,b a,baaa,b, a,b a,ba,b, a,bIn a method for producing a hinge-like bend line (or ) in a sheet of paper, paperboard, cardboard or foil, particularly a brochure cover, by rotatively driven tools, the bending line (or ) is produced by roll bending without scoring the material in the form of a scoring bead. The roll bending is preferably realized by the cooperation of a tool edge of a first rotary tool member with a conical outside surface of a second rotary tool member. The roll bending process lowers the bending resistance of the sheet in the region of the bending point (or ), wherein the sheet is simultaneously pre-bent in a certain direction along the bending point, e.g., in order to take into account the position of the brochure cover on the book block at the spine edges (the sheet is pre-bent inward in a U-shaped fashion).