Method for cleaning tip of sampling nozzle by reversed phase driving of two vibration plates

As a method for cleaning the nozzle of clinical analyzers with high cleaning efficiency, ultrasonic cleaning was selected because the cleaning mechanism can be miniaturized and the effect on dispensing accuracy is negligible. As for nozzle cleaning, it is necessary to meet two requirements: (i) suppress the wetting range of the nozzle inserted in the chamber of the ultrasonic cleaner and (ii) generate cavitation at a depth of a few millimeters from the liquid surface. To meet those requirements, a new ultrasonic cleaner with an L-shaped cleaning head as a small and high-efficiency cleaning nozzle is proposed. The shape of the cleaning head, which enables the vibration phase of the ultrasonic irradiation surfaces to be reversed even with a single ultrasonic transducer (BLT), is composed of two vibration plates at the tip of the cleaning head to concentrate the sound pressure in the cleaning area. The BLT with cleaning head has three resonant frequencies: fBLT, fL-P, and fU-P. At fBLT, the ultrasonic transducer expands and contracts in the longitudinal direction.At fL-P and fU-P, deformation of each vibration plate is large. By setting the resonance frequencies in the increasing order of magnitude fL-P, fBLT, and fU-P, the phases of the two vibration plates are reversed by driving at fBLT. It was confirmed by experiment that the sound pressure can be concentrated in the cleaning area by driving the cleaning head at fBLT.