A hydrostatic drive includes a diesel engine and a hydrostatic adjustable machine which supplies multiple consumers in normal operation as a pump. The machine has a pressure/flow regulator to which is communicated, according to the load-sensing principle, the highest load pressure of the consumers, in particular when the machine is operated as a pump. In order to realize a start/stop function of the diesel engine, a previously charged high-pressure reservoir supplies the hydrostatic machine, which then acts as a starter motor for the diesel engine. In order to switch from pump to starter motor, the hydro-machine is adjusted over zero. In order for this switch to take place quickly and reliably, the pressure/flow regulator is deactivated by means of a switching valve and the adjustment device is supplied with an adjustment pressure medium via the switching valve, which medium is taken from the high-pressure reservoir or from an auxiliary reservoir.

The present disclosure relates to a hydraulic control circuit for crane slewing gear having directional valves arranged in work lines and controllable separately for the inflow and outflow to the hydraulic motor for the carrying out of a rotational movement of the slewing gear, wherein an inflow valve serves the control of the oil inflow from a hydraulic pump via the work line to the hydraulic motor and an outflow valve is provided via which the hydraulic motor can be relieved to the tank, wherein the work lines are each connected via at least one check valve to a common inlet of the outflow valve to relieve the hydraulic motor independently of the direction of rotation of the slewing gear via an outflow valve into the tank.

Some embodiments of the disclosure provide an advance and retreat automatic control method based on hydraulic sensing conversion and an advance and retreat automatic control system based on hydraulic sensing conversion, which includes an automatic advance and retreat device based on hydraulic sensing conversion, a motor, an oil cylinder, and/or an electric generator. When the digging motor encountered an overlarge resistance force, a pressure on the digging motor is instantaneously increased and exceeds a setting pressure value, hydraulic oil enters a hydraulic operated directional valve and pushes a valve rod to make the walking motor is reverse and retreat, an ultrahigh pressure state of the digging motor is released to restore to a normal pressure value to make reciprocated impact, the valve rod of the hydraulic operated directional valve is reset, and the walking motor is forwards rotated for advancing.

Methods of controlling an actuator during operation using a hydraulic circuit, and related apparatus, are described. The circuit has a first path section along which fluid is supplied to a first chamber of the actuator using a first valve and a second path section along which fluid is extracted from a second chamber of the actuator using a second valve. Pressure data associated with a pressure of the fluid supplied to the first side of the actuator are obtained, a pilot pressure pPilot is produced based on the data and the first and second valves are configured based on the pilot pressure pPilot.

An arrangement for operating a hydraulic consumer including a hydraulic control valve having a main slide valve defining a hydraulic volume flow in the direction of hydraulic connections provided for operation of the hydraulic consumer, a pressure compensation valve and an orifice plate, the pressure compensation valve controlled on the basis of a pressure difference that drops at the orifice plate when the volume flow passes through, such that the pressure compensation valve adopts an at least partially closing control position when the hydraulic pressure upstream of the orifice plate in the direction of the volume flow is greater than downstream of the orifice plate, including a restoring spring force of a spring element preloading the pressure compensation valve into a fully open position, and a sensor arrangement sensing the pressure difference and transmitting a pressure difference value derived therefrom to a control unit evaluating the pressure difference value.

A hydrostatic drive includes a diesel engine and a hydrostatic adjustable machine which supplies multiple consumers in normal operation as a pump. The machine has a pressure/flow regulator to which is communicated, according to the load-sensing principle, the highest load pressure of the consumers, in particular when the machine is operated as a pump. In order to realize a start/stop function of the diesel engine, a previously charged high-pressure reservoir supplies the hydrostatic machine, which then acts as a starter motor for the diesel engine. In order to switch from pump to starter motor, the hydro-machine is adjusted over zero. In order for this switch to take place quickly and reliably, the pressure/flow regulator is deactivated by means of a switching valve and the adjustment device is supplied with an adjustment pressure medium via the switching valve, which medium is taken from the high-pressure reservoir or from an auxiliary reservoir.

The present disclosure relates to a hydraulic control circuit for crane slewing gear having directional valves arranged in work lines and controllable separately for the inflow and outflow to the hydraulic motor for the carrying out of a rotational movement of the slewing gear, wherein an inflow valve serves the control of the oil inflow from a hydraulic pump via the work line to the hydraulic motor and an outflow valve is provided via which the hydraulic motor can be relieved to the tank, wherein the work lines are each connected via at least one check valve to a common inlet of the outflow valve to relieve the hydraulic motor independently of the direction of rotation of the slewing gear via an outflow valve into the tank.

A hydraulic system is disclosed for use with a machine. The hydraulic system may have a closed-loop, meterless hydraulic circuit with a first pump fluidly connected to a first actuator. The hydraulic system may also have a closed-loop, metered hydraulic circuit with a second pump fluidly connected to a second actuator. The hydraulic system may further have a combiner valve configured to selectively direct fluid from the closed-loop metered hydraulic circuit to the closed-loop meterless hydraulic circuit.

A fluid pressure control circuit connected to first and second pumps includes: a switching valve configured to allow for and disconnect a communication between the first and second pumps; and first and second unloading valves configured to unload working fluid discharged from the respective first and second pumps. The switching valve and the first and second unloading valves are disposed in separate valve sections.

A control arrangement for supplying a plurality of hydrostatic actuators includes a pump with an output connected to a circulating line that opens into a tank. The control arrangement has a metering port and an individual pressure compensator for each actuator. The individual pressure compensators are connected in series by the circulating line. Some of the pressure medium are configured to be branched off from the circulation channel for the respective actuator by the individual pressure compensators and fed to the metering port disposed downstream of the individual pressure compensator. The pressure medium that is not required is forwarded from each individual pressure compensator into the circulating line and is fed back from the last individual pressure compensator to the tank by the circulating line. The actuators are prioritized based on the order of their individual pressure compensators and move independently of the load pressure without expensive load sensing lines.