Method for bending sheets

Claim 1

A process for bending a sheet metal element into an elongated self-supporting sheet metal construction panel, having inside and outside surfaces, a longitudinal axis and a transverse sectional shape continuous in the direction of the longitudinal axis, said transverse sectional shape comprising at least one trapezium section having rectilinearly arranged walls forming inner and outer beams and webs connecting the beams with the webs forming nonparallel walls and a web connecting an inner and outer beam, the height of the trapezium section being the distance between an inner and an outer beam, comprising the steps of providing a pair of rolls including a stationary roll and an adjustable roll, and at least one adjustable bending roll disposed in front or behind said pair of rolls, each of said rolls having a profile surface which corresponds to the sectional shape of the sheet metal, feeding said panel through said rolls and bending said sheet metal panel, from one end to the other in its longitudinal direction to bend, the beams and webs of said panel continuously about an axis normal to the height of said trapezium section thereby placing said sheet metal element in compressive stress, and simultaneously forming continuous longitudinal beads within said panel parallel to said longitudinal axis between those beams and webs in which the bending occurs by said pair of rolls and where upsetting of material subjected to compressive stress occurs, existing beads in any of those beams and webs being enlarged and reinforced in a form-locking manner.