Patent ID: 8393875

Claim:
A pressure-controlled liquid supply system comprising: a pump configured to pump a liquid from a liquid source to a destination system; a cycle tank coupled to the pump and configured to hold liquid temporarily before being supplied to the destination system; a pump control device coupled between the pump and the cycle tank such that the liquid passes through the pump control device, the pump control device comprising: a pressure opening device configured to allow pumped liquid to pass through when an inlet pressure of the pumped liquid exceeds an opening pressure of the pressure opening device, thereby creating a pressure differential; a venturi in parallel with the pressure opening device to allow a flow of liquid around the pressure opening device and through the venturi, wherein a pressure differential across the venturi creates a flow through the venturi and a reduced pressure zone at or proximate a throat region of the venturi, the reduced pressure zone having a lower pressure than an outlet pressure at an outlet of the pump control device when a flow is present through the venturi; and a pressure switch fluidly coupled to the venturi at or proximate the throat region and responsive to a throat pressure, the pressure switch being configured to switch the pump off when the throat pressure exceeds a shut off pressure and to switch the pump on when the throat pressure falls below a turn on pressure, the shut off pressure being greater than the turn on pressure.