A compensator spool of a load sensing valve device includes a pressure chamber, a compensator throttle portion, a pressure introduction chamber, a pressure introduction port, a maximum load pressure introduction chamber, and a selector valve. A groove is formed around the pressure introduction port, and a groove moves relatively between a passage communicating with an actuator to reduce an opening area of the pressure introduction port when the compensator spool moves.

A hydraulic actuator circuit is disclosed for use with first and second shock absorbers, which each may include a piston disposed within a housing. The piston helps define upper and lower working chambers. The circuit may have a motor, a first pump, driven by the motor, and is associated with the first shock absorber and the motor. A second pump, driven by the motor, may be associated with the second shock absorber. A first accumulator communicates with both of the first and second pumps. A first switch valve may assist in controlling fluid flow into the chambers of the first shock absorber. A second switch valve may assist in controlling fluid flow into the chambers of the second shock absorber.

Disclosure herein are hydraulic systems and method of use thereof. The hydraulic systems can include a hydraulic cylinder and a manifold. The hydraulic cylinder can have a first end and a second end. The hydraulic cylinder can include a first port, a second port, and a third port. The first port can be located proximate the first end. The second port cane be located proximate the second end. The third port can be located in between the first port and the second port. The manifold can include a first valve and a second valve. The first valve can be in fluid communication with the first port and the third port. The second valve can be in fluid communication with the second port and the third port.

Industrial truck with a drive part and a load part with two wheel arms that is height-adjustable relative to the drive part, wherein each of the wheel arms has a wheel arm lever, which has at least one load roller and is pivotably articulated on the wheel arm, and a rod, via which a height adjusting movement of the load part is coupled with a pivoting movement of the wheel arm lever, wherein the rod has a hydraulic cylinder, with which a length of the rod is adjustable and which has an operating volume, characterized in that the two rods are push rods, and the industrial truck has a pressure accumulator, which is connectable with the operating volumes of the two hydraulic cylinders.

Industrial truck with a drive part and a load part with two wheel arms that is height-adjustable relative to the drive part, wherein each of the wheel arms has a wheel arm lever, which has at least one load roller and is pivotably articulated on the wheel arm, and a rod, via which a height adjusting movement of the load part is coupled with a pivoting movement of the wheel arm lever, wherein the rod has a hydraulic cylinder, with which a length of the rod is adjustable and which has an operating volume, characterized in that the two rods are push rods, and the industrial truck has a pressure accumulator, which is connectable with the operating volumes of the two hydraulic cylinders.

A drift control method for a machine that includes a controller, a cutting tool, a motor having a motor shaft for driving a machine function, a control valve, and an operator control for commanding a machine function. The drift control method includes sensing a neutral position of the operator control, and when in the neutral position, further storing a first position of the motor shaft or cutting tool in the controller, detecting a change in position of the motor shaft or cutting tool with a sensor, determining a direction as a function of the change in position, and hydraulically controlling the motor shaft or cutting tool to the first position.

A drift control method for a machine that includes a controller, a cutting tool, a motor having a motor shaft for driving a machine function, a control valve, and an operator control for commanding a machine function. The drift control method includes sensing a neutral position of the operator control, and when in the neutral position, further storing a first position of the motor shaft or cutting tool in the controller, detecting a change in position of the motor shaft or cutting tool with a sensor, determining a direction as a function of the change in position, and hydraulically controlling the motor shaft or cutting tool to the first position.

An aircraft store ejector systems and subsystems thereof. Embodiments can include a two-reservoir re-pressurization system wherein a remote reservoir is used to maintain desired pressure in a local ejector reservoir. The system can include a release valve having a vent valve and valve piston. The release valve can control release of pressurized gas to a pitch control valve. The pitch control valve can be configured to distribute the pressurized gas between two or more ejector piston assemblies. One or more of the ejector piston assemblies can include multiple concentric piston stages and piston chambers, the piston chambers configured to contain a volume of gas. The ejector piston assemblies can be configured to compress the volume of gas within the piston chambers as the piston stages are extended out from the aircraft. Such compression can provide a return force to the piston stages.

The present disclosure relates to a hydraulic drive system having a hydraulic circuit architecture operable in first and second modes. In a first mode, a main hydraulic pump (22) is used to drive a hydraulic actuator (24) via a closed hydraulic circuit, and a charge pump (42) provides charge flow to the closed hydraulic circuit. In a second mode the main pump set to zero displacement and the charge pump (42) is used to drive the hydraulic actuator (24).

A cylinder has a piston part, a cylinder part, and a pipe section connected to the piston or cylinder parts. A portion of the pipe section encloses a pressure compartment which receives a fluid to apply a pressure on a pressure surface so the piston part is displaced in a first stroke direction. A first return pressure compartment receives a fluid to apply a pressure on a first return pressure surface so that the piston part is displaced in a second return stroke direction. The first return pressure compartment is positioned on the outside of the pipe section, and the area of the first return pressure surface is substantially equal to the area of the return pressure surface so that a volume-neutral operation of the cylinder is provided. Also described is a hydraulic system, an excavator comprising the cylinder and a procedure for operation of the cylinder.