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 compressed-air system having a safety function and a method for operating such a compressed-air system. The compressed-air system contains two working valves, which each can selectively assume an aerating position that aerates a load and a venting position that vents the load. Both working valves are redundantly connected on the output side to the load by means of a separating device. The separating device allows one or the other of the working valves to be separated, while the aeration of the load is maintained, in order to subject the one or the other working valve to an examination of the switching function of the one or the other working valve.

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.

A hydraulic circuit for a construction machine including a direction control valve group including direction control valves provided in tandem to a center bypass passage, a bleed-off valve provided to the center bypass passage downstream of the direction control valve group, and a control valve controlling an amount of pressure oil to be supplied to the direction control valve.

A hydraulic circuit for a construction machine including a center bypass passage including a group of directional control valves arranged in tandem; and a bleed-off valve arranged in the center bypass passage on a downstream side of the group, wherein each directional control valve includes a first internal passage causing the pressurized oil supplied to the directional control valve to flow out to the center bypass passage and a second internal passage supplying the pressurized oil to a cylinder port, wherein a parallel passage is formed by the center bypass passage and the first internal passage by causing the pressurized oil discharged from the hydraulic pump to flow to the center bypass passage on the downstream of the directional control valve, wherein the second internal passage supplies the pressurized oil from the center bypass passage through an opening of a spool and/or the bypass passage to the cylinder port.

A pressure cylinder includes a working cylinder and an intensification cylinder that is divided by a separator block. A working piston is arranged in the working cylinder and connected to a working rod that extends to an end portion. An intensification piston and an intensification rod are arranged in the intensification cylinder. A pump is configured to provide a pressurized hydraulic fluid to the pressure cylinder. A fluid reservoir is configured to supply a hydraulic fluid to the pump. A first valve is configured to selectively regulate hydraulic fluid flow between the pressure cylinder and the fluid reservoir and the pump. A second valve is configured to selectively regulate fluid flow between a first valve and the advance intensification chamber. A controller is in communication with the first valve and the second valve. The controller is configured to coordinate movement of the working piston and the intensification piston.

A compressed-air system having a safety function and a method for operating such a compressed-air system. The compressed-air system contains two working valves, which each can selectively assume an aerating position that aerates a load and a venting position that vents the load. Both working valves are redundantly connected on the output side to the load by means of a separating device. The separating device allows one or the other of the working valves to be separated, while the aeration of the load is maintained, in order to subject the one or the other working valve to an examination of the switching function of the one or the other working valve.

A pressure cylinder includes a working cylinder and an intensification cylinder that is divided by a separator block. A working piston is arranged in the working cylinder and connected to a working rod that extends to an end portion. An intensification piston and an intensification rod are arranged in the intensification cylinder. A pump is configured to provide a pressurized hydraulic fluid to the pressure cylinder. A fluid reservoir is configured to supply a hydraulic fluid to the pump. A first valve is configured to selectively regulate hydraulic fluid flow between the pressure cylinder and the fluid reservoir and the pump. A second valve is configured to selectively regulate fluid flow between a first valve and the advance intensification chamber. A controller is in communication with the first valve and the second valve. The controller is configured to coordinate movement of the working piston and the intensification piston.

The present invention provides an electro-pneumatic arrangement to act as a mechanical timer (delay) in ON-OFF valve actuators. The arrangement comprises: two directional valves (1 and 2) with three ways and two positions, actuated by solenoid; a three-way, two-position directional valve (3), actuated by a pneumatic pilot; a set of compressed air conditioning with filter and pressure regulating valve (4); a valve metering (precise flow rate adjustment) (5), a check valve (6); and an accumulator vessel (7).

An energy recovery system and control strategy for a hydraulic excavator boom is provided. The energy recovery system includes an oil tank, an accumulator, and a first energy recovery cylinder, an energy utilization cylinder, and a second energy recovery cylinder that are sequentially arranged below a boom and connected to the boom, the first energy recovery cylinder, the energy utilization cylinder, and the second energy recovery cylinder are connected to the oil tank and the accumulator through an oil conveying system, the oil conveying system includes a rod cylinder oil inlet and outlet pipe system, a rodless cylinder oil inlet pipe system of the energy recovery cylinder, a rodless cylinder oil inlet pipe system of the energy utilization cylinder, a rodless cylinder oil return pipe system of the energy utilization cylinder, and a rodless cylinder oil return pipe system of the energy recovery cylinder.