The invention relates to a driving mechanism (11) for the traction-exerting component (13) of a conveyor device (1), with a frame (10); at least one reversing wheel (15a, 15b) and one driving wheel (17) supported on said frame; an endlessly revolving, flexible traction-exerting component (13) guided around the reversing and driving wheels (15a, 15b; 17) and having a pulled strand and a returning strand; a tensioning device (18); as well as a setting device comprising the tensioning device. The tensioning device (18) has two support bodies arranged one behind the other in the direction of revolution of the traction-exerting component (13), said support bodies being adjustable against one another, and tensioning elements each supported on said support bodies. With its pulled strand, the traction-exerting component (13) is guided around one of the tensioning elements, and with its returning strand around the other tensioning element, as well as around the reversing and driving wheels (15a, 15b; 17), whereby tensioning forces directed against each other are admitted to the tensioning elements, which are arranged spaced from each other; and whereby the spacing is adjustable to a limited extent via the at least one setting element.