Hydraulic system

Claim 1

In a hydraulic system having an adjustable pump, a plurality of multiway control valves each having inlet and outlet ports and shiftable control passages, conduits for delivering pressure fluid from said pump via said control valves to a plurality of loads, means for adjusting the flow of the pressure fluid to the working conditions of said loads, the adjusting means including measuring throttles provided respectively in the passages of said multiway control valves which are assigned to high pressure conduits for said loads, an additional passage provided in each of the multiway control valves and being connected to the outlet of the assigned measuring throttle, a regulating flow return conduit connected to respective multiway control valves to communicate with the additional passage when the control valves are switched-over into a working position; an additional throttle provided in the outlet end of the regulating return conduit, flow regulating means controlled by the pressure difference between the outlet of the pump and the pressure in the regulating return conduit, and a hydraulically controlled actuator connected to the outlet of the pump via the flow regulating means and being mechanically coupled to the pump to adjust the discharge of the latter in response to the working conditions of the load, an arrangement of said flow regulating means comprising a flow regulating valve having a housing and, within the housing, a stepped differential piston defining a first part of a larger diameter and a second part of a smaller diameter; a first pressure space adjoining the end face of the first piston part and being connected to the pressure conduit at the outlet of said pump; a second pressure space adjoining the second piston part and being connected to said regulating return conduit; an adjusting spring arranged in said second pressure space to bias said differential piston toward said first pressure space; a first annular groove formed in said second piston part; a control port formed in said housing in the range of said annular groove; a second annular groove formed in said housing between the end face of the second piston part and said first annular groove; a bypass conduit connecting said first pressure space to said second annular groove; and said control port being connected to said actuator.