A folding roller and machine comprising said roller

A folding roller with a rotation axis, comprising at least one gripping member extending longitudinally along the folding roller and at least one piezoelectric actuator for controlling a pivoting movement of the at least one gripping member about a pivoting axis thereof parallel to the rotation axis of the folding roller;

• and wherein said at least one piezoelectric actuator comprises an active piezoelectric element contained in an amplification member of deformations of the active piezoelectric element caused by a voltage applied to said active piezoelectric element.

A folding machine comprising at least a first feed path for feeding at least a first web material toward a folding unit, and members for forming packs of folded sheets produced from the web material;

• wherein the folding unit includes a first folding roller with a rotation axis;
• wherein the first folding roller comprises at least one gripping member extending longitudinally along the first folding roller, and at least one piezoelectric actuator for controlling a pivoting movement of the at least one gripping member about a pivoting axis thereof parallel to the rotation axis of the first folding roller;
• and wherein the at least one piezoelectric actuator comprises an active piezoelectric element contained in an amplification member of deformations of the active piezoelectric element caused by a voltage applied to said active piezoelectric element.