| 摘要 |
PROBLEM TO BE SOLVED: To make it possible to constitute a device at low cost, regarding a dampening device in a printing machine. SOLUTION: The device has a plurality of water droplet discharging units 20 attached in a manner facing a plate cylinder for discharging water droplet on the plate cylinder. Each of the water droplet discharging units 20 is provided with an ultrasonic wave oscillator 21 for generating ultrasonic wave, a horn 22 connected with the ultrasonic wave oscillator 21, having a length equivalent to the half-wave length of the ultrasonic wave, for transmitting sound waves, and a chamber 23 connected to a part equivalent to a node of the sound wave in the vicinity of center in the horn 22 having a plurality of discharging holes 24 in the vicinity of a part equivalent to an antinode of the sound wave, filled with water. A part of the tip of the horn 22 which abuts against the antinode of the sound wave is made to contact with the water directly for transmitting vibrations and the droplets are discharged from the discharging holes 24.
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