Abstract: A conveyor drive mechanism has a continuous drive loop trained over first, second, and third pulleys, with the first and second pulleys disposed in driving relationship to a support bed or conveyor, and a driving facility which supplies drive torque in either direction to the third pulley, to move the drive loop and conveyor in the selected direction. Counterpoised anti-backlash motors impart equal, opposed counter-torques to the first and second pulleys to impose a predetermined level of continuous tension in the active area of the drive loop, even during reversal of the direction of the torque transmitted by the driving facility.