Screening Characteristics of Oscillating Screen under Reciprocating, Elliptical and Circular Motion (I)

Abstract

This paper is the results of experimental studies on the screening rate under the reciprocating, elliptical and circular motions. The four-bar linkages was adopted to oscillate the screen in that motion respectively. The opening size of screen was 6.90mm-screen, and the sample of soy-bean used for the screening test was of the uniformed size, viz. 5.66mm<particle size<6.73mm-screen, which had been screened on a standard testing sieve in a Rotap shaker.
The main results were as follows:
1) The most suitable frequency varied as feeding rates and the oscillating types of screen, and the screening rate of the most suitable frequency decreased with the increase of the feeding rate.
2) Although the screening rate varied with flowing velocity, in the case of small feeding rates, the screening rate of grains under the reciprocating motion was slightly greater than that of elliptical and circular motions, while in the case of larger amount of feeding rates, the screening rates of grains under the elliptical and circular motions were greater than that of reciprocating motion. In the latter case, the flowing velocity of grains on the screen surface was about 30-40cm/sec.
3) Varying the frequencies, the relationship between the screening time and screening rate was given by the logarithmic probability function in the earlier period and by the exponential function in the later period.
4) Varying the length of sereens, the relationship between the screening time and the screening rate was given by the exponential function in the earlier period and by the logarithmic proba bility function in the later period. These characteristics of the screening were similar to the experimental results with the Ro-tap shaker