Patent ID: 6840744

Claim:
A system for continuous delivery of a measured flow of liquid to a processing apparatus, the system comprising: a reservoir for holding a bulk supply of the liquid; an intermediate vessel; a first pump for supplying liquid from the intermediate vessel to processing equipment at a first rate; a second pump for supplying liquid from the reservoir to the intermediate vessel at a second rate, the second rate being faster than the first rate; and a controller comprising: a sensor adapted to determine when the weight of liquid in the intermediate vessel has reached a minimum position to initiate operation of the second pump to refill the vessel and adapted to terminate operation of the second pump when the weight of liquid in the intermediate vessel has reached a maximum position; and a monitor adapted to continuously monitor the weight of liquid in the intermediate vessel to determine a mass flow rate of liquid from the intermediate vessel and adapted to adjust the first pump while the liquid in the intermediate vessel falls from the maximum position to the minimum position such that the mass flow rate of liquid from the intermediate vessel substantially matches a required flow rate of the processing equipment.