US Patent 7931431 Automated material handling system with load transfer vehicles

A material handling system for use in storing and moving goods within multi-level storage warehouses, ocean going vessels and the like wherein storage areas are provided on at least one of the levels and wherein goods are automatically transferred to and from the storage areas and between the various levels by self-propelled load transfer vehicles. The load transfer vehicles move across the surface of the various levels and are also movable under their own power within open vertical trunks between the levels to thereby move goods to any desired area within the system, warehouse or vessel.