The present invention relates generally to fluid power systems, and more particularly to a fluid power system which includes two fluid power circuits and a means for controlling the pressure in one of the circuits in response to the pressure in the other circuit. Still more particularly, the invention relates to such a fluid power system for use in a dewatering filter press.
Dewatering filter presses are used to remove excess water from a slurry. In such filter presses, water pressure acts against a diaphragm to squeeze the water from the slurry while hydraulic pressure acts against a piston to provide a clamping force holding the press closed. In this type of press, the magnitude of the clamping force, and hence the magnitude of the hydraulic pressure in the clamping piston, must be proportional to the water pressure acting against the diaphragm. In the prior art, this is accomplished by using several pressure activated switches that are responsive to the water pressure acting against the diaphragm. This arrangement produces a clamping pressure that is not a linear function of the water pressure but instead is a stair step function of the water pressure.