Development of a Drum-Pressing-Type Endless Wire-Winding Mechanism

Wire-driven mechanisms are advantageous in terms of weight reduction and integration into complex structures. However, conventional wire-winding mechanisms face a problem in which the fleet angle increases when winding with a small shaft diameter to increase traction force. In addition, traction force is reduced owing to the overlapping wires. Drive failure owing to wire slack is another significant issue. In this study, we developed a new wire-winding mechanism that can wind a wire endlessly without reducing the traction force or increasing the fleet angle while being robust to wire slack. Increases in the fleet angle and wire overlap were avoided using grooved guide pulleys. The tension of the wire wound on the winding shaft is maintained by the frictional force generated by a drum that presses the wire against the winding shaft. A torque limiter function can be added by designing the frictional resistance force. Because the frictional force between the wire and winding shaft is independent of the shaft diameter, the winding shaft diameter can be reduced to achieve both high wire tension and miniaturization. Using a closed-loop wire-driven system, the proposed mechanism can continuously wind wires endlessly in principle. We developed a prototype with a 6 mm-diameter winding pulley. Wire-pulling experiments using the prototype demonstrated the validity of the theoretical equation for wire tension. The proposed drum-pressing-type endless wire-winding mechanism can wind wire endlessly with a smaller winding shaft radius than conventional winding mechanisms, is robust against wire slack, and includes a torque–limiter function, demonstrating its practical utility.