Patent ID: 11905153
Assignee: JUNGHEINRICH AKTIENGESELLSCHAFT
Field: Handling (Mechanical engineering)
Classification: CPC B  F | IPC B

Claim 5:
6. A method of operating a hydraulic system of an industrial truck that includes a lift mast having at least one mast lift stage driven by at least one mast lift cylinder, a free lift stage having a load receiving means driven by at least one free lift cylinder such that the load receiving means is displaceable along the lift mast, the hydraulic system supplying a hydraulic fluid to and unloading the hydraulic fluid from the at least one mast lift cylinder and the at least one free lift cylinder, a control for the hydraulic system programmed to operate the hydraulic system, and a displacement sensor provided on the mast lift stage and on the free lift stage for determining a measured value of respective retraction speeds of the mast lift stage and the free lift stage, the method comprising:
simultaneously actuating the at least one mast lift cylinder and the at least one free lift cylinder in a load lowering operation via the control for the hydraulic system such that the mast lift stage and the free lift stage are simultaneously retracted; and
regulating a first volumetric flow through the first lowering valve and a second volumetric flow through the second lowering valve via the control for the hydraulic system such that, based on the measure value, the at least one mast lift stage and the load receiving means reach a lower end position at least approximately simultaneously at the end of the lowering operation when the load receiving means is completely lowered.