A valve (18), for a valve assembly (10) for regulating the pressure of a fluid guided in a hydraulic system for supplying pressure to at least one hydraulic consumer (12a, 12b), includes a pilot control stage (48) and a main control stage (38) for at least partially clearing or blocking a fluid path from a supply connection (P) to an outflow connection (T). A relief stage (54) for pressure relief of a fluid chamber is arranged between the pilot control stage (48) and the main control stage (38). The relief stage (54) compares the existing load pressure at load terminal (LS) dedicated to the hydraulic consumer (12a, 12b) with the outflow pressure at the outflow connection (T), clearing the pressure relief if both pressures are approximately the same. The relief stage (54) can be directly connected to the load connection (LS) and can be charged with load pressure.

A floating control system for a fixed displacement pump system is disclosed, which relates to the technical field of floating mechanisms and includes: a fixed displacement pump, floating control valves, a floating mechanism, boom function valves, an actuator and a control device, where the fixed displacement pump, the floating control valves and the floating mechanism are connected in sequence, the fixed displacement pump, the boom function valves and the actuator are connected in sequence, the floating control valves include a pressure reducing valve and a floating switching valve, and the boom function valves include a fixed differential overflow valve and a proportional directional valve; and the fixed differential overflow valve and the proportional directional valve are connected in parallel between the fixed displacement pump and an oil return tank, the floating switching valve and the fixed differential overflow valve are connected through a feedback oil path.

An open and closed circuit parallel drive system and a control method based on a four-chamber hydraulic cylinder are provided. The system includes: a closed pump-controlled drive unit and an open valve-controlled drive unit. The four-chamber hydraulic cylinder is driven by the open valve-controlled drive unit with a large load power, and the operating velocity and displacement of the four-chamber hydraulic cylinder are controlled by the closed pump-controlled drive unit with a small load power, thereby improving the linearity and stability of the four-chamber hydraulic cylinder control and reducing the system installed power and throttling loss.