US Patent 7484712 Hoist assembly

A hoist assembly for raising and lowering a load attached to a cable having a drum with a groove spirally disposed about its outer surface mounted within a frame. The groove having a predetermined pitch and configured to receive the cable wound about the drum. The drum has a cable take-off point where the cable ceases contacting the drum and is tangent to the drum. A head block is mounted to the frame and configured to receive the cable as it wound and unwound on the drum while maintaining tangential alignment with said take-off point.