Patent ID: 7819335

Claim:
An ultrasonic liquid delivery device comprising: a housing having an internal chamber, at least one inlet in fluid communication with the internal chamber for receiving liquid into the internal chamber and at least one exhaust port in fluid communication with the internal chamber whereby liquid within the chamber exits the housing at said at least one exhaust port; an ultrasonic waveguide separate from the housing and disposed at least in part within the internal chamber of the housing to ultrasonically energize liquid within the internal chamber prior to said liquid being exhausted from the housing through the at least one exhaust port; an excitation device operable to ultrasonically excite said ultrasonic waveguide; and a control system for controlling operation of the liquid delivery device between an excitation mode in which the excitation device is operated at an ultrasonic excitation frequency to ultrasonically excite the ultrasonic waveguide and a ring down mode in which the excitation device is inoperable to excite the ultrasonic waveguide such that the ultrasonic waveguide is allowed to ring down, the control system being operable to monitor a ring down frequency of said ring down with a feedback sensor and further being responsive to said ring down of the ultrasonic waveguide to adjust the excitation frequency of the excitation device in the excitation mode thereof based at least in part on the ring down frequency.