Sheet-fed printing press for simultaneous recto-verso printing of sheets, in particular for the production of security documents

A sheet-fed printing press adapted to carry out recto-verso printing of individual sheets, the sheet-fed printing press comprising:

• a plurality of printing units each adapted to carry out simultaneous recto-verso printing of the sheets, each printing unit including two printing cylinders cooperating with one another and forming a printing nip where both sides of the sheets are simultaneously printed, a first printing cylinder of the two printing cylinders collecting ink patterns from at least two plate cylinders associated with the first printing cylinder and a second printing cylinder of the two printing cylinders collecting ink patterns from at least two plate cylinders associated with the second printing cylinder and wherein the first printing cylinder is located above the second printing cylinder such that the sheets travel laterally through each printing unit from a first lateral side located upstream of the printing nip to a second lateral side opposite to the first lateral side and located downstream of the printing nip,
• wherein at least two of said printing units are located one after the other,
• wherein at least two sheet transfer elements are provided downstream of the printing nip of a first printing unit of the at least two of said printing units and upstream of the printing nip of a second printing unit of the at least two of said printing units to transfer the sheets from the first printing unit to the second printing unit,
• wherein the plate cylinders are each inked by an associated inking apparatus with at least one ink fountain,
• wherein the inking apparatuses are positioned with at least a portion of each respective ink fountain being located over or under at least a portion of the associated plate cylinder so that a flow of ink from the ink fountain to the plate cylinder is in a substantially vertical direction.