Patent ID: 7395664
Filing Date: 2008-07-08
Classification: F15B

Abstract:
1. Hydraulic system for utility vehicles, in particular agricultural tractors, for supplying primary and/or auxiliary pressure medium consumers ( 6 , 11 , 12 ) with pressure medium, comprising a pump ( 1 ), sucking from a pressure medium tank ( 3 ), the pressure of said pressure medium being controlled as a function of the load pressure of the pressure medium consumers and exceeding the load pressure by a predetermined control pressure differential, whereby in order to produce a first control pressure differential for operating a primary pressure medium consumer its load pressure acts upon a pressure and flow controller ( 13 ) assigned to the pump and in order to produce a second, higher control pressure differential for operating auxiliary pressure medium consumers ( 11 , 12 ) a pressure exceeding their load pressure is produced by means of an amplifier device ( 29 ), which acts upon the pressure and flow controller, characterized in that the amplifier device ( 29 ) consists of a proportionally controllable pressure reducing valve ( 39 ) with a control piston ( 46 ), a pressure inlet ( 42 ) connected to a pressure pipe ( 41 ), an inlet ( 43 ) connected to a load pressure reporting pipe ( 28 a ) conducting the load pressure of the auxiliary pressure medium consumers ( 11 , 12 ) and an outlet leading to the pressure and flow controller ( 13 ), whereby the control piston ( 46 ) is subjected on the one side to the variable force of an electromagnet ( 47 ) and the load pressure prevailing at the inlet ( 43 ) of the auxiliary pressure medium consumers ( 11 , 12 ) and on the other side to the force of an adjustable spring ( 48 ) and the pressure prevailing at the outlet ( 44 ).