Improved Cable-Drive Pretensioner

An improved mechanism has been devised to facilitate the adjustment of tension in a cable in a cable-and-pulley drive. Cable-and-pulley drives are being used increasingly in robots and other high-performance, computer-controlled machines. Typically, a cable is looped around various drive pulleys with its ends anchored in proximity to each other on two coaxial cylinders (see figure). During operation of the cable drive, the cylinders are locked against rotation relative to each other to maintain a preset tension. To adjust the tension, it is necessary to unlock the cylinders and rotate them relative to each other.