Magnetostrictive Ultrasonic Bacteria Destroying Apparatus with a Metallic Horn

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  • Saneyoshi Jun'ichi
    Research Laboratory of Precision Machinery and Electronics, Tokyo Institute of Technology
  • Mori Eiji
    Research Laboratory of Precision Machinery and Electronics, Tokyo Institute of Technology
  • Ide Masao
    Electrical Communication Engineering Department, Musashi Institute of Technology

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Other Title
  • 金属ホーンを用いた磁歪式超音波細菌破壊装置
  • キンゾク ホーン オ モチイタ ジワイシキ チョウオンパ サイキン ハカイ ソウチ

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Abstract

A new system of the low frequency ultrasonic apparatus for bacteria destruction was developed for laboratory use. The plot of this system is not to produce an intense ultrasonic field in liquid but to vibrate a small part of the bottom of a metallic spherical flask violently. The driving system consists of a 20 kc rectangular magneto-strictive transducer and a resonant metallic exponential horn of half wave length, and they are soldered together. The vessel containing the liquid for treatment, made of stainless steel sheet of 0. 7 mm thickness, is placed on the narrow end of the metallic horn and is pressed against it with adequate pressure. Hence, the vessel is detachable and can be pasteurized conveniently. The introduction of the horn as a mechanical impedance transformer improved the efficiency. The voltage proportional to the velocity or the displacement of the horn end is indicated on a voltmeter as the measure of the destroying activity. This voltage is produced by means of "motional impedance bridge" which is inserted between the power amplifier and the transducer. This voltage must be the more direct measure of the activity than the sound pressure in the vessel or the driving current of the transducer. The frequency of 20 kc was selected so as to avoid the deterioration of the contents in the cell and the discomfortable sustained noise. The actual test for the destruction of coli bacteria are described also.

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