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A hydraulic lifting mechanism, particularly suitable for a battery-powered industrial truck, including a hydraulic lifting cylinder, a hydraulic unit, operating as a pump in the load lifting operational mode, and supplying the lifting cylinder with pressure medium, and operating as a motor in the lo

A hydraulic lifting mechanism, particularly suitable for a battery-powered industrial truck, including a hydraulic lifting cylinder, a hydraulic unit, operating as a pump in the load lifting operational mode, and supplying the lifting cylinder with pressure medium, and operating as a motor in the load lowering operational mode during which mode it is actuated by the pressure medium exiting from the lifting cylinder, and a DC generator coupled with the hydraulic unit operating as an electromotor in the load lifting operational mode and as a generator in the load lowering operational mode. A control valve arrangement is provided at the halfway point in the pressure path between the hydraulic cylinder and the hydraulic unit, which is controlled by a lifting mechanism control. In addition, the lifting mechanism control controls a regenerative brake circuit supplied by the DC generator in the load lowering operational mode. The control valve arrangement includes a proportional valve which is opened by the lifting mechanism control in the load lowering operational mode in accordance with a ramp-like function. The regenerative brake circuit is switched on depending on the output current of the DC generator working as a generator, if the generator output current exceeds a predetermined value. Undesirable dropping of the load in the lowering operational mode is hereby prevented during transition to regenerative braking.

대표청구항 ▼

A hydraulic lifting mechanism for a battery-powered industrial truck, having a hydraulic lifting cylinder; a hydraulic unit operating pump in a load lifting operational mode, in which a pressure medium is supplied to the lifting cylinder, and operating as a motor in a load lowering operational mode,

A hydraulic lifting mechanism for a battery-powered industrial truck, having a hydraulic lifting cylinder; a hydraulic unit operating pump in a load lifting operational mode, in which a pressure medium is supplied to the lifting cylinder, and operating as a motor in a load lowering operational mode, in which the pressure medium exiting from the lifting cylinder powers the hydraulic unit; a DC generator coupled to the hydraulic unit which operates as an electromotor in the load lifting operational mode and as a generator in the load lowering operational mode; a regenerative brake circuit supplied by the DC generator in the load lowering operational mode; a control valve arrangement located in a pressure path between the hydraulic cylinder and the hydraulic unit; and a lifting mechanism control controlling the regenerative brake circuit and the control valve arrangement; characterized in that the control valve arrangement comprises a proportional valve, wherein the lifting mechanism control opens the proportional valve in accordance with a ramp-like function in the load lowering operational mode and activates the regenerative brake circuit, depending on an output current of the DC generator operating as a generator, if the generator output current exceeds a predetermined value.