Patent ID: 8104601

Claim:
A system for sorting or retrieving a plurality of items, comprising: a plurality of destination areas for receiving the items, wherein the destination areas are arranged in a first array of columns or rows; a plurality of vehicles for delivering the items to or from the destination areas, wherein each vehicle comprises an on-board motor for driving the vehicle; and a track system for guiding the delivery vehicles to the destinations, wherein the track system forms a loop that the vehicles can circulate around, and the track system comprises: a generally horizontal upper track section; a generally horizontal lower track section positioned at a lower height than the upper track; a plurality of generally vertical track sections intersecting the upper track and the lower track; and a plurality of intersections where the horizontal sections intersect the vertical sections, wherein the intersections provide paths between a generally horizontal path of travel along one of the upper or lower track, and a generally vertical path of travel along one of the vertical track sections; a first gate at an intersection of the upper track and a first one of the vertical track sections, wherein in a first position, the gate provides a first path through the intersection along one of either the upper track or the first vertical track while impeding travel along the other of the upper track and the first vertical track, and wherein in a second position, the gate provides a second path through the intersection substantially orthogonal to the first path to allow one of the delivery vehicles to change path direction; wherein each vehicle comprises a drive element that interacts with the track system to maintain the general orientation of the vehicle relative to the horizon as the vehicle moves between a vertical track and a horizontal track.