Dockside container handling crane with high speed hoist system

In a dockside container handling crane of the type comprising a crane frame and a movable boom extending generally laterally therefrom, said container crane further comprising a cable hoist system having a hoist drum with a plurality of cables wound therearound and operatively engaging a corresponding plurality of headblock sheaves adapted to be raised and lowered to vertically adjust a container-engaging spreader apparatus, the improvement comprising a hoist cable speed enhancing system positioned between said headblock sheaves and the terminal ends of said hoist cables, said hoist cable speed enhancing system comprising:

• (a) a frame;
• (b) a stationary sheave set supported by said frame and comprising a plurality of sheaves;
• (c) a vertically adjustable sheave head supported by said frame and comprising a plurality of sheaves and being adapted for vertical movement within said frame toward and away from said stationary sheave set;
• (d) means for selectively actuating said sheave head so as to motivate said sheave head toward or away from said stationary sheave set;
• (e) each of said plurality of cables from said hoist drum extending between and wrapping around two or more sheaves in each of said sheave set and said sheave head, respectively, and terminating;
• and
• (f) a hydraulic cylinder positioned on each side of said frame and to each of which an equal number of said plurality of cables are fixedly connected at their termination, and actuation means for each of said hydraulic cylinders so that selective actuation will act to vertically adjust a corresponding side of said spreader apparatus supported by said headblock sheaves;
• whereby the speed of extension or retraction of said plurality of cables by said hoist drum is increased by said actuating means by selectively motivating said second sheave head either toward or away, respectively, from said stationary first sheave head.