Patent ID: 7007465

Claim:
Mobile handling device with a hydraulic circuit, the hydraulic circuit (L) comprising: a lifting cylinder ( 1 ) arranged in a lifting device suitable for handling a variable load and a first accumulator ( 6 ) for recovering or recycling lowering load energy; a variable hydraulic machine ( 3 ) with two ports ( 10 , 11 ), which is capable via a drive unit (D) of emitting full system pressure in two flow directions to said ports, one port ( 11 ) being connected to said first accumulator ( 6 ) and the other port being connected to said lifting cylinder ( 1 ); a first stop valve ( 2 ) arranged in the line between one port ( 10 ) of the hydraulic machine ( 3 ) and the lifting cylinder ( 1 ), and a second stop valve ( 5 ) arranged in the line between the hydraulic machine's second port ( 11 ) and the first accumulator ( 6 ); a second accumulator ( 20 ), which is connected via at least one non-return valve ( 31 ) to the line between the hydraulic machine ( 3 ) and the lifting cylinder ( 1 ), wherein the maximal flow capacity for said hydraulic machine ( 3 ) preferably is less than the maximal output flow from said lifting cylinder ( 1 ) at a rapid lowering motion; a line ( 6 - 42 ) connected to the first accumulator ( 6 ) and running to a first tank ( 42 ) via an overflow valve ( 8 ) and a by-pass line ( 70 ) around said overflow valve, which by-pass line comprises a variable pump ( 71 ) and a non-return valve ( 72 ), said non-return valve preventing oil running from the first accumulator to the variable pump ( 71 ); and a position sensor ( 90 ) connected to the lifting cylinder ( 1 ) and registering the position of the piston within the cylinder ( 1 ), a first pressure sensor ( 92 ) registering the gas pressure in the first accumulator ( 6 ), a second pressure sensor ( 91 ) registering the oil pressure in the first accumulator ( 6 ), and a computerized control unit ( 94 ), wherein information from said sensors ( 90 , 91 , 92 ) is used in said control unit ( 94 ) for controlling the variable pump ( 71 ) to ensure that a certain minimal pressure always is retained in said first accumulator ( 6 ).