Pulley hook block it is working with a fixed pulley fixed to the structure, a combination of a plurality of fixed pulley and the movable pulley is made, it can be changed effort and force direction. Pulley sheaves can be divided into work and balance wheel, is rotating about a central axis common machinery. When you select the pulley rope groove, rope groove radius often take R = 0.6d, it requires contact surfaces rope and rope groove as large as possible. Pulleys are widely used in cranes, winches, lifts and other machinery, lifting machinery is an important part.