Patent ID: 7527768

Claim:
A liquid dispenser for dispensing a predetermined amount of a liquid from a reservoir, including a negative pressure system to supply a negative pressure which acts on the liquid in the reservoir while no liquid is being dispensed, the negative pressure system comprising: an ejector communicating with an air compressor; an electropneumatic regulator provided downstream of the ejector, communicating with the ejector to regulate the negative pressure inside the reservoir to a desired negative pressure level; a pressure sensor provided between the electropneumatic regulator and the reservoir; and a control means for controlling the electropneumatic regulator configured to be responsive to a signal from the pressure sensor to regulate the negative pressure inside the reservoir to the desired negative pressure level; the liquid dispenser further comprising: a pressure regulator branched from the ejector and communicating with the compressor, said regulator configured to reduce a pressure of pressurized gas from the compressor to a pre-determined pressure level, said pressure regulator further configured to provide a pressure to discharge the liquid from the reservoir; and a delivery valve connecting the electropneumatic regulator, the pressure regulator, and the reservoir with one another, wherein the delivery valve is configured to respond to the signal from the pressure sensor such that the reservoir communicates with at least one of the negative pressure system and the pressure regulator.