US Patent 7850411 Storage and retrieval system

A storage and retrieval system includes a continuous track and a plurality of individual storage units stacked in multiple columns or rows. Each storage unit includes wheels for engaging the continuous track for selective movement along the track. A conveyor apparatus is used to selectively move the storage units along the length of the continuous track between uppermost positions of adjacent columns, so as to support the storage unit as the storage unit passes gaps in the upper rail due to intermediate vertical rails extending downwardly intermediate ends thereof.