Sheet metal working machine

A sheet metal working machine comprising a hydraulic drive system configured to drive a plurality of working tools of the sheet metal working machine independently to perform machining on a piece, said hydraulic drive system comprising:

• a plurality of hydraulic cylinders, wherein each hydraulic cylinder is associated with a respective working tool and provided with a respective piston configured to define a thrust chamber and a return chamber inside said hydraulic cylinder and associated with the corresponding working tool for moving the working tool along a respective working axis;
• a first pump of reversible type connected to said thrust chambers of said hydraulic cylinders and arranged to send fluid at a supply pressure to at least one of said thrust chambers so as to push said respective piston along a working direction and enable the working tool associated therewith to interact with the piece, or to suck fluid from at least one of said thrust chambers, to enable said respective piston to move along a return direction and the working tool to disengage and move away from the piece;
• a plurality of valves, wherein each valve is associated with a respective one of said hydraulic cylinders, interposed between said first pump and said thrust chamber of said respective one of said hydraulic cylinders, and activable to put said first pump into flow connection with said thrust chamber so as to drive said hydraulic cylinder;
• a hydraulic accumulator connected to said return chambers of said hydraulic cylinders and arranged for maintaining fluid at a defined preload pressure in said return chambers;
• a second pump of reversible type coupled and connected to said first pump, wherein said first and second pumps are configured to be driven by a same electric motor controlled by a control unit of the sheet metal working machine and arranged to drive said first and second pumps in both rotation directions and such that said first and second pumps deliver a defined fluid flow rate at a defined supply pressure;
• and
• a first differential valve interposed between said second pump and said thrust chambers and activable when the supply pressure exceeds a first working pressure in at least one of said thrust chambers so as to connect said second pmp to a fluid reservoir.