US Patent 8651790 Warehouse storage system

A system and method for the safe storage of items wherein a storage structure is provided having a first section in which storage units are stored in vertically oriented cells with each storage unit being stacked one upon another and wherein at least one transfer vehicle is provided for selectively engaging and conveying the storage units along an overhead grid track system between the first section and a second section wherein the at least one transfer vehicle may be used to either lift or lower a storage unit and move the storage unit to and from a storage position in one of the vertical storage cells of the first section of the storage structure.