Order preparation system, and method implementing the system

An order preparation system comprising, in a warehouse:

• a plurality of racks (Ra) each configured to receive storage units (U) intended for items, the racks being arranged in a plurality of vertical planes,
• at least one order preparation zone (PC) arranged at a distance from the racks,
• a conveying facility configured to transport one or more storage units received in the racks to said at least one order preparation zone, in a first transport direction, or conversely to transport one or more storage units from the order preparation zone to the racks, in a second transport direction, said conveying facility successively comprising, along the first transport direction:
• a first conveying system (CV1) which is arranged in a shelving aisle arranged between two adjacent racks, configured to transport storage units (U) from at least one of the two racks comprising several first conveying devices (SH) arranged at a plurality of heights, said first devices being independent of each other for the horizontal transport of storage units along said shelving aisle,
• a second conveying system (CV2), comprising at least one second conveying device (AC) configured for the vertical transport of storage units from the first conveying device to a third conveying system, in the first transport direction,
• the third conveying system (CV3), configured for the transport of storage units from the second conveying system to said at least one order preparation zone (PC), in the first transport direction, and wherein the third conveying system comprises a plurality of self-guided trolleys (CHR) circulating in open space on a rolling surface of the warehouse, said self-guided trolleys comprising rolling means configured to ensure movement of the self-guided trolley along a horizontal plane of the rolling surface.