One or more techniques and/or systems are disclosed for a hydraulic system that is used with a vehicle hitch, to raise and lower an implement attached to the hitch. The system has a lifting side, that raises the hitch, and a downforce side that applies downward pressure. Hydraulic actuators are used to apply the up or down force using supply lines coupled to both sides. A downforce pressure control valve controls an amount of hydraulic pressure is supplied to the downforce side. A mode select valve is fluidly coupled to the downforce pressure control valve and is used to select hitch operation between a double acting hitch position, a single acting hitch position, and a neutral position. A work port check valve is between the downforce side and the mode select valve to stop the fluid from flowing back into the system when de-energized or in the neutral position.

The invention relates to a method and device for controlling a combined rotary/push movement of a load-receiving means of an industrial truck, in particular a three-way stacker, both the rotary movement and the push movement being brought about by means of respective hydraulic elements (32, 34), which are supplied with hydraulic fluid by a single hydraulic pump (22) which is driven by an associated pump motor (24), and a performance characteristic of the hydraulic pump (22) being controlled according to a predetermined progression over time during the rotary/push movement; the industrial truck comprising a valve assembly (30) which is designed to be operated such that, below a threshold value for the hydraulic pressure provided by the hydraulic pump (22), only the rotary movement of the load-receiving means is brought about, while, above the threshold value, both the rotary movement and the push movement are brought about. Here, sensor means (36a, 36b) are provided which detect a temperature of the pump motor (24) and/or of the hydraulic pump (22), and the predetermined progression over time of the performance characteristic of the hydraulic pump (22) during the rotary/push movement is adapted according to a predetermined relationship depending on the temperature of the pump motor (24) and/or of the pump (22) detected by the sensor means (36a, 36b).

A hydraulic system (600) and method for reducing boom dynamics of a boom (30), while providing counter-balance valve protection, includes a hydraulic actuator (110), first and second counter-balance valves (300, 400), first and second independent control valves (700, 800), and first and second blocking valves (350, 450). The actuator includes first and second corresponding chambers. In a first mode, the second counter-balance valve is opened by the first control valve, and the first counter-balance valve is opened by the second control valve. In a second mode, at least one of the counter-balance valves is closed. A meter-out control valve (800, 700) may be operated in a flow control mode, and/or a meter-in control valve (700, 800) may be operated in a pressure control mode. Boom dynamics reduction may occur while the boom is in motion (e.g., about a worksite). By opening the counter-balance valves, sensors at the control valves may be used to characterize external loads. The control valves may respond to the external loads and at least partially cancel unwanted boom dynamics. The system may further detecting faults in actuators with counter-balance valves and prevent any single point fault from causing a boom falling event and/or mitigate such faults.

In a hydraulic drive of a tool, a piston is adapted to be acted upon by a pump via a pressure limiting seat valve and a parallel switching seat valve of a valve arrangement. A restriction is provided in a pressure line upstream of the pressure limiting seat valve which is connected to a tank on the flow-off side. A drain line leads from a working chamber of the piston via the switching seat valve to the tank. A closing side is adapted to be acted upon by pressure and an opening side is adapted to be acted upon by a force generated when the pressure limiting seat valve responds. The pump is adapted to be switched off when the maximum operating pressure has been reached, so that the piston will execute a return stroke. A pressure-increasing restriction is provided on the flow-off side of the pressure limiting seat valve.

When option attachment has not been attached, a reserve flow/direction control valve 8 is made to operate as a center bypass cut valve. When an option attachment has been attached, switching control is performed. In the switching control, when the option attachment is not used, the reserve flow/direction control valve 8 is made to operate as a center bypass cut valve for adjusting composite opening area of a center bypass and thereby controlling the flow rate of hydraulic fluid flowing into an actuator. When the option attachment is used, the reserve flow/direction control valve 8 is made to operate so as to supply the hydraulic fluid to an option hydraulic actuator 14.

The disclosure relates to a valve, e.g., a proportional valve, comprising a main piston for actuating a main volumetric flow and a pilot piston for actuating a pilot volumetric flow. The main piston and the pilot piston are guided in a valve housing in a longitudinally movable manner, and the pilot piston can be actuated using a magnetic device. The position of the main piston can be set using the pilot piston which, based on the movement position thereof, signals the fluid pressure acting on the main piston into a pilot chamber via a fluidic connection or cuts of the fluid connection and connects the pilot chamber to a tank or low-pressure side via another fluidic connection into which a valve is introduced that closes in a leak-proof manner as soon as a fluidic connection is produced between the main piston and the pilot chamber.

The disclosure relates to a valve, comprising a main piston for actuating a main volumetric flow and a pilot piston for actuating a pilot volumetric flow. The main piston and the pilot piston are guided in a valve housing in a longitudinally movable manner, and the pilot piston can be actuated using a magnetic device. The position of the main piston can be set using the pilot piston in that a fluid pressure acting on the main piston is signalled via a fluidic connection into a pilot chamber comprising the pilot piston which keeps the main piston in the closed position thereof, said closed position cutting of the main volumetric flow.