(under subclass 293) Rotating cylindrical or drum sifters on horizontal or inclined axes provided with means for agitating the material by gaseous-fluid currents as the major agitating factor.
(1) Note. This subclass will include cases where the sole agitating means may be the air-supplying means, but will also include cases which employ mechanical stirring or conveying means within the sifter, provided the air-supplying means is a major factor and not merely an incident to the use of such mechanical devices or a minor factor. In the latter case the classification is determined by the type of mechanical agitator.
