A device for actuating a curtain/awning in a double glazing includes a pulley supported by support elements connected to connection elements integrally connected to a wall of the double glazing at the movement group. A ring of cord is partially wound around the pulley and is maintained taught by a tensioning element, it too connected to the wall of the double glazing. By applying a tension to the cord ring, a torque is generated tending to rotate the pulley. The torque is transmitted by suitable transmission elements to the group for moving the curtain/awning. The support elements of the pulley are separated from the connection elements for values of tension applied to the cord ring that are greater than a pre-established limit value. The separation cancels the tension of the cord.