Abstract: The tensioning device comprises a support plate attached to a pivot defining a fixed axis; an intermediate tubular element accommodating the pivot and able to rotate about the fixed axis; a pulley for a belt and supported by the tubular element, surrounding the pivot and able to rotate about an axis of rotation which is not coincident with the fixed axis; and an elastic element interposed between the pivot and the intermediate tubular element so as to urge elastically the intermediate tubular element against the belt. To ensure a high degree of perpendicularity between the pivot and the support plate and, therefore, accurate engagement between the tensioning device and the belt, the support plate and the pivot are integrally formed.

Abstract: A tensioner for belts including a stationary structure (3), an arm (4) movable with respect to a shaft (7) of the stationary structure, a torsion spring (6), a pair of dampening cones (8), (9) associated with the stationary structure and the arm, a compression spring (10) acting on the dampening cones. The mean radius of the cones is smaller than the maximum radial dimension of the torsion spring. The value "1" of the arm is correlated to the mean radius of the cones determining a frictional dampening between the cones smaller than that existing between the shaft and the rotating arm.