A SYSTEM COMPRISING DIFFERENTIAL HYDRAULIC CYLINDERS AND A HYDRAULIC MACHINE COMPRISING THE SYSTEM
A system (1) for moving a tool such as a boom, dipper, bucket or hook of a hydraulic machine such as an excavator, crane or forklift and a hydraulic machine such as an excavator, crane or forklift comprising the system, said system comprising a first bidirectional hydraulic variable displacement pump (11), coupled for liquid flow, via a first flow line (25) to a first differential hydraulic cylinder; a first generator (15); a second generator (17) arranged, when said second generator is in a first operational mode, to be driven by said first generator for generating electrical energy, and when said second generator is in a second operational mode, arranged for driving, together with said first generator, said first bidirectional hydraulic variable displacement pump; a third bidirectional hydraulic pump (19), a first bidirectional hydraulic motor and a first tank (23), wherein said third bidirectional hydraulic pump is arranged to be driven by said first bidirectional hydraulic motor for supplying liquid from said tank to said first flow line and/or adding liquid to said tank from said first flow line; a third flow line, wherein said third hydraulic pump is controlled such that a difference of a flow rate of said liquid in said third flow line and a flow rate of said liquid in said first flow line is within a predetermined range, preferably wherein said flow rates are equal.