Control system for a pump

In a pumping system including an adjustable pump furnishing a pumping pressure and a flow at an output side and having a regulating element for adjusting said flow and first and second pressure controlled pistons for adjusting said regulating element, in which said second piston has a diameter larger than said first piston, a control system for maintaining the product of said pumping pressure times flow constant, comprising, in combination, throttle valve means having a throttle valve inlet connected to the output side of said pump, a throttle valve outlet, and a cross-sectional flow area varying as a function of said pump pressure, for creating a pressure difference between said throttle valve inlet and said throttle valve outlet, said pressure difference increasing with the decrease of said cross-sectional area;

• additional throttling means connected to said throttle valve means and having a constant cross-section;
• pressure limiting means connected to the output side of said additional throttling means;
• means for applying said pumping pressure to said first pressure controlled piston;
• control valve means for varying the pressure acting on said second pressure controlled piston as a function of a pressure difference applied to said control valve means;
• and means for applying said pressure difference created by said throttle valve means and said additional throttle means to said control valve means.