Device for separating an uppermost sheet from a supply stack by means of air blowers

Device (1) for separating an uppermost sheet (S1) from a supply stack (S) in the area of a sheet transport unit (4) operating with a partial vacuum and having a sheet bending mechanism (41), for the purpose of grasping the separated uppermost sheet and feeding it to a processing station in a sheet processing device, said device (1) comprising:

• a first air blower (3.1) for spreading out several sheets of an upper sheet stack area (SR);
• a second air blower (3.2) for separating the uppermost sheet (S1) and holding back an adhering sheet (S), following the uppermost sheet (S1) said first and second air blowers (3.1, 3.2) being located downstream in front of the supply stack and transverse to a sheet transport path (42) and act against a sheet transport direction (T), in said sheet transport path, and the upper area of the sheet stack, which may be positioned at the same predetermined height by a lifting device (5), and wherein air jets with different pressures, directions, and diameters may be generated by said first and second air blowers (3.1;
• 3.2) supplied from an air pressure source (6) with at least one air nozzle (31) located in the area of a center line (Y, Z) of the stack (2) and the transport path (42), and with several inner air nozzles (32) located on both sides of the center line said first air blower (3.1) being outside of the inner air nozzles (32);
• and a third air blower (3.3), having two nozzle elements (33.1, 33.2), respectively on either side of the first air blower (3.1), in the area of the center line (Y, Z) of the stack (S) and the transport path (42), supplied from a high pressure air source (7), each of said nozzle elements (33.1, 33.2) having a vertically overlapping arrangement, with upper air nozzles (D1, D1′) directed toward a middle front edge area of the second and third sheets of the stack (S) for the purpose of separating and holding back the adhering second sheet (S2) following the uppermost stack sheet (S1), and lower air nozzles (D2, D2′) directed toward the middle front edge area of the sheets located thereunder in order to spread them apart and lift them, wherein said two nozzle elements (33.1, 33.2) provide air jets (ST) generated with a high excess air pressure and small diameter, which on the one hand support the separation of the uppermost sheet (S1) from the stack as well as hold back the adhering sheet (S2) following the uppermost sheet, and on the other hand are used to spread apart the sheets in the upper area of the sheet stack.