US Patent 7134645 Winch assembly for use with synthetic ropes

A winch assembly is disclosed that eliminates rope crushing, even when synthetic ropes are used. Tension is applied to the rope by at least one traction sheave so that the tension at the drum is reduced. By using multiple sheaves with large wrap angles traction can be applied to the rope over a much larger area, reducing shear stress and minimizing internal wear due to relative motion of rope components. The winch drum and at least one traction sheave are driven independently, preferably by AC induction motors using frequency control. The winch assembly may operate in conjunction with a hydraulic tensioner so that lower horsepower motors can be used to maintain constant tension in moving systems.