The author has developed five kinds of techniques on electrostatic separation of particle size utilizing the balance of the electrostatic and gravitational force. The first is an inclined plate conveyer system. A plate conveyer consisted of parallel electrodes was constructed and four-phase electrostatic traveling wave was applied to the electrodes to transport particles on the conveyer. Particles were separated with size under the voltage application of appropriate frequency based on the feature that small particles were transported upward against the gravity but large particles were apt to fall down. The second technique is an inclined tube system. The principle is common with that of the inclined plate system. The third technique utilizes a circular electrostatic conveyer similar with the mass spectroscopy but utilizes the feature that small particles fly high altitude compared to that of the large particle. The forth technique, a vortex system, also utilizes the difference of flying locus of small and large particles. The last technique is the combination of the linear conveyer and an electrostatic separation roller located at the end of the conveyer. Small particles were attached onto the roller charged by a charger roller. Although the yield was reduced to realize the high separation performance with the former four techniques, relatively high yield was realized without reducing the separation performance with the roller system. This technique is expected to be utilized to the separation of toner and carrier particles used in electrophotography.
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