A drive unit is in working connection with a power takeoff by way of a wrap spring, which has a predetermined number of turns between its two ends and which serves as a load torque interlock. The wrap spring has a first actuating area assigned to a selected direction of rotation on at least one of its two ends and a second actuating area assigned to the opposite direction of rotation, where the first actuating area can be brought into nonrotatable working connection with the drive unit and the second actuating area into nonrotatable working connection with the power takeoff. By the application of a drive torque produced by the drive unit on the first actuating area, a first change in the diameter of the turns in the direction away from a braking device can be obtained, with the result that the frictional connection between the turns and the braking device is at least weakened. By the absorption of a restoring torque which originates from the power takeoff and acts in the opposite direction of rotation on the second actuating area after the drive has been turned off, a second change in the diameter of the turns in the direction toward the braking device can be obtained, with the result that the frictional connection between the turns and the braking device is increased.