the bearing lever 53 and thereby the second belt clamping roller 57 also inwardly since the directly driven bearing lever 52 in the clamping position assumes a defined position while the other bearing lever 53 is deviated more or less due to the spring force independence on the belt length and thickness the spring wire 55 between the lever 52 53 is angled so that a certain displacement between the engaging points is possible the bending angle and the wire length are selected so that despite the permissible displacement compensation the driving operation of the spring wire 55 is not negatively affected the application of the clamping force to the not directly actuated bearing lever 53 is performed through a torsion spring 59 this spring is held on a pin 60 on the transmission cover 57 and its one end 61 is supported against a formation 63 in the transmission cover 57 and pressed by it simultaneously against the transmission cover 57 so that the torsion spring 59 can not spring from the pin while the other end 62 is supported on the axial 58 of the second clamping roller 47 and presses it thereby outwardly therefore no additional components are needed.