Patent attributes
A liquid dispenser is provided which dispenses a predetermined amount of a liquid from a reservoir. It includes a negative pressure system to supply a negative pressure which acts on the liquid in the liquid reservoir while no liquid is being dispensed. The negative pressure system includes a negative pressure source, an electropneumatic regulator communicating with the negative pressure source to regulate the pressure inside the liquid reservoir to a desired negative pressure level, a pressure sensor provided between the electropneumatic regulator and reservoir, and a control means for controlling the electropneumatic regulator responsive to a signal from the pressure sensor to regulate the pressure inside the reservoir to the desired negative pressure level. It can assure a negative pressure which is stable even just after it is switched on and can thus work stably even right after the switch-on.
