US Patent 9826833 Rack assembly and sub-rack thereof

A rack assembly having two side racks, two rails, and at least one sub-rack, wherein the rails are mounted between the side racks and include a front rail and a rear rail lower than the front rail. Each rail has an opening in a side of the rail, with the opening of the front rail defined in a bottom of the front rail and the opening of the rear rail defined in the rear rail at a side facing the front rail. The at least one sub-rack has a rack frame, a connection rod, and at least one supporting member and is slidable along the rails The rack frame has at least one front rod and at least one rear rod wherein each front rod has an extension rod mounted retractably on a top of the front rod and a front wheel.