The guiding of the belts (28) of the formation of the ball into the baling presses, round (1) is a recurrent problem, due to variations in the characteristics of the materials and to the dimensional variations during the manufacture of the machines, but also by the arrival of irregular products to be processed in the press chamber and, finally, because of the irregular shapes and different slopes of the agricultural land. This invention proposes a solution to overcome the lateral displacements of the belts (28), to their excessive friction and their deterioration against the devices which limit the displacements. A device of the dynamic range (55, 70, 72, 74) monitors the position parameters of the belts and acts on the main elements of the chassis (11, 12) which support a plurality of rollers (35, 37, 39, 41, 43) receiving the belts, in order to modify simultaneously the position of these rollers, so as to maintain the belts (28) to their position and avoid excessive lateral friction.
