Material handling system

A material handling apparatus for storing or retrieving a plurality of items, comprising:

• a plurality of storage racks spaced apart from one another forming an elongated aisle wherein each storage rack comprises a plurality of storage locations for storing containers containing items;
• a plurality of delivery vehicles wherein each vehicle comprises:
• a horizontal drive system operable to drive the vehicle along a horizontal surface,
• a vertical drive operable to drive the vehicle vertically;
• and
• a transfer mechanism operable to transfer an item between the vehicle and one of the storage locations;
• a conveyor spaced apart from the plurality of storage racks and having a generally horizontal conveyor surface configured to receive a container from one of the delivery vehicles and convey the container in a forward direction toward a workstation where an operator can remove one of the items from the container or in a reverse direction to convey the container away from the workstation and back toward the one delivery vehicle;
• a guide adjacent the conveyor configured to guide the delivery vehicles vertically upwardly to an upper position adjacent the conveyor surface;
• a central controller comprising a microprocessor programmed to provide control signals to control the delivery vehicles to perform the steps of:
• driving a first one of the vehicles on a horizontal surface toward a first of the storage racks;
• driving the first vehicle vertically upwardly to a first storage location in the first storage rack;
• transferring a first container from the first storage location onto the first delivery vehicle;
• driving the first vehicle downwardly with the first container to the horizontal surface;
• driving the first vehicle with the first container along the horizontal surface to the guide;
• operating the vertical drive to move the first delivery vehicle with the first container vertically upwardly along the guide to the upper position;
• transferring the first container onto the conveyor surface;
• and
• actuating the conveyor to convey the first container away from the first vehicle and toward the workstation.