US Patent 7172523 Automatic mechanically controlled continuously-variable-ratio drive

A continuously-variable-ratio drive, having an input shaft; a flywheel integral with the input shaft; a drive pulley idle with respect to the input shaft and defined by two half-pulleys defining a groove of variable size for a V belt; and a centrifugal control assembly. The control assembly has a centrifugal actuating device which intervenes above a first threshold value of the angular speed of the input shaft to connect the drive pulley angularly to the flywheel by means of a friction clutch; and a speed adjusting device which is active over a second threshold value of the angular speed of the input shaft to adjust the size of the groove of the drive pulley and therefore the work diameter of the belt.