Abstract: A device for tensioning flexible elements wound onto pulley has a pulley (4) onto which the flexible element (2) is (partially) wound is able to perform translatory movements relative and perpendicular to the shaft (8) on which it is rotatably mounted, respectively between an advanced position, where minimum tensioning of the flexible element (2) associated with the pulley (4) occurs, and a retracted position, where maximum tensioning of the flexible element (2) occurs, tensioning means being provided in order to cause said translatory movements of the pulley (4) with respect to the shaft (8).