J.Pagi - Ground Nuts and Cotton Marketing Ltd., Tel Aviv, Israel

Particle passage and screen clogging are interrelated, in the sense that the oscillatory motion that allows a high passage rate for particles of size near that of the apertures, results in rapid clogging of the apertures. Accurate sizing depends on the passage of the near size particles and can be obtained only with frequent release of the trapped particles.

The relation between screen motion and size range of trapped particles was investigated. Time intervals at which trapped particles should be released were evaluated and a proper release method was selected. On the basis of these data a screen was developed using two independent motions simultaneously. One is a horizontal oscillatory motion adequate for efficient particle passage through the screen apertures. The other is a vertical motion for the release of trapped particles by inertia force at intervals adjusted to the clogging rate of the screen. This screen can be operated continuously without cumulative clogging, giving nearly perfect sizing accuracy. Tests demonstrated considerable improvement in accuracy over that achieved with conventional screens.