Abstract: A hydraulic lift apparatus for a battery driven lift truck includes a hydraulic lift cylinder. A hydraulic pump operates as a pump in a load raising mode, so as to feed pressure fluid to the lift cylinder. The hydraulic pump operates as a motor in a load lowering mode. The hydraulic pump is driven by the pressure fluid displaced by the lift cylinder. A direct current machine is coupled to the hydraulic pump, so as to operate as an electric motor in the load raising mode and to operate as a generator in the load lowering mode. A useful brake circuit is energized by the direct current machine in the load lowering mode. A valve assembly is disposed in the pressure fluid path between the lift cylinder and the hydraulic pump. Control apparatus are provided for controlling the valve assembly and including speed regulating apparatus for varying the speed of the direct current machine. At least one secondary hydraulic consumer is adapted to be connected to a hydraulic pressure source via an associated control valve.

Abstract: A hydraulic lift device for battery operated industrial trucks comprising a hydraulic ram, a hydraulic machine operating as a pump in a load raising cycle and as a motor in a load lowering cycle, a separately excited DC machine operating as a motor in the load raising cycle and as a generator in the load lowering cycle, and energy recovering circuitry which is fed by the DC machine in the load lowering cycle. A load holding valve is disposed in the fluid path between the hydraulic ram and the hydraulic machine. Speed of the DC machine is set by a speed control. A separate field current control includes a desired value setting circuit for determining a desired value for the field current (I.sub.FSoll) from a predetermined relationship between the speed (n.sub.Ist) and the armature current (I.sub.ASoll). Power switches are associated with the field winding and the armature, and are actuated by the current control.