An agricultural machine including a connecting structure designed to be hitched to a tractor, the connecting structure including a coupling support, a carrier beam and a transmission unit； the transmission unit including a driving pulley, a driven pulley, a transmission element drive-mounted on the driving and driven pulleys, the transmission unit including a transmission element tensioning system； a work unit articulated to the carrier beam via at least one folding axis, the work unit being fitted with at least one work tool, which is driven in rotation. In this machine, the tensioning system applies an unfolding force to the work unit during at least one part of the deployment from a transport position.
