Patent ID: 7788916

Claim:
A hydraulic system for utility vehicles with a regulated hydraulic pump for the supply of pressure medium to internal and external pressure medium consumers via load sensing spool valves, the system comprising: a priority valve through which the external consumers are supplied with pressure medium; an input device that allows an operator to selectively set priorities to the internal and the external pressure medium consumers, such that the flow rate of the hydraulic pump is distributable to the operating pressure medium consumers to a degree desired by the operator, wherein the input device allows an operator to selectively set “no consumer priority”, “internal consumer priority” or “external consumer priority,” wherein the input device allows an operator to also set the pressure medium demand of the external consumers to be used when “external consumer priority” is set on the input device, and wherein the priority valve limits the pressure medium supply to the external pressure medium consumer, so long as the pressure medium demand of the internal and external pressure medium consumers exceeds the maximum flow rate of the hydraulic pump and “no consumer priority” or “internal consumer priority” is set on the input device; a driver operated input for setting the pressure medium demand of each of the internal consumers via the respective spool valves; a flow sensor for providing a signal indicative of the maximum flow rate being delivered by the pump, and a control unit that receives a signal denoting any pressure medium consumer priority set on the input device, the pressure medium demand of each of the internal consumers set on the driver operated input and the flow sensor signal, the control unit repeatedly calculating from the sensor signal the maximum flow rate being delivered by the pump, and, if “external consumer priority” is set on the input device, reducing the value of demand set on the driver operated input for the internal consumers so that the sum of the internal and external demands corresponds to the maximum flow rate being delivered by the pump, and, if “no consumer priority” or “internal consumer priority” is set on the input device and the sum of the set internal and external demands exceed the maximum flow rate being delivered by the pump, allowing the priority valve to limit the flow to the external consumers.