Method And Apparatus For Automatically Fractionating A Sample Of Particulate Material Into Discrete Size Fractions

Abstract

A fractionating apparatus under microprocessor control including a tumbler having a series of screens of progressively larger openings around its periphery. A sample of particulate material is passed successively through each of the screens by incremental rotation of the tumbler. To aid in classifying the fractions, a spray of fluid is projected against the screens and a rocking motion is imparted to the tumbler. The smallest fraction, not being retained, is entrained in a moving stream of fluid and passed directly to a porous weighing member. When this entire fraction is deposited and weighed, the next larger fraction is accumulated in the weighing member. These individual weights and their sum are recorded and from them size percentages are computed.