Automatic, mechanical, continuously variable transmission, particularly for a heavy-duty vehicle

An automatic, mechanical, continuously variable transmission (1) comprising an input shaft (2);

• a flywheel (10) integral with the input shaft;
• a drive assembly (5) idle with respect to the input shaft (2) and having a drive pulley (6) defined by a first half-pulley (6a) and a second half-pulley (6b) which define a groove (8) of variable width for a V belt (C) ;
• friction clutch means (12) interposed axially between said first half-pulley (6a) and said flywheel (10);
• a centrifugal actuating assembly (42) comprising a centrifugal actuating device (40) controlling said clutch means (12) and for setting said clutch means (12) to a torque-transmission condition in response to an angular speed value of said input shaft (2) greater than a first threshold value, so as to connect said drive pulley (6) angularly to said flywheel (10), and a speed regulating device (41) for moving said second half-pulley (6b) axially with respect to said first half-pulley (6a) to adjust the width of the groove (8) of the drive pulley (6) in response to variations in the speed of said input shaft (2), said speed regulating device (41) being active above a second threshold value of the angular speed of the input shaft (2) higher than said first threshold value;
• characterized in that said actuating device (40) comprises push means (54, 61) which exert axial thrust on said first half-pulley (6a) at each speed value of said input shaft (2) above said first threshold value.