An ultrasonic cleaner for cleaning the tip of a sampling nozzle by reversed phase driving of two vibrating plates (Translated)

Abstract

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 its 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 for high-efficiency cleaning of the nozzle is proposed. The cleaning head is composed of two vibration plates at its tip to concentrate the sound pressure in the cleaning area, and the shape of the head enables the vibration phase of the ultrasonic-irradiation surfaces of the plates to be reversed with a single bolt-clamped Langevin-type ultrasonic transducer (BLT). The BLT with the proposed cleaning head has three resonant frequencies: that of the BLT, fBLT, that of the lower plate, fL-P, and that of the upper plate, fU-P. At fBLT, the BLT 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 increasing order of magnitude, i.e., fL-P, fBLT, and fU-P, it is possible to reverse the phases of the two vibration plates by driving the BLT at fBLT. It was experimentally confirmed that the sound pressure can be concentrated in the cleaning area of the cleaning head by driving the BLT at fBLT.