A device (22) fitted with ribs is placed on a cylindrical rod (20) so that it is fixed to it in bending. The device (22) is formed of at least three ribs connected to each other at their ends, and at least one pair of elements in the form of a star connecting the ribs together, at least close to its central region. This device enables the rod (20) to apply an approximately radial force to the center of the rod through an actuator onto webs (24) bearing on its ends, minimizing the mass for a given spacing of the webs (24). The device is particularly applicable to the control of aircraft control surfaces.