Abstract: In a screening machine comprising two screening frames (13 and 31) each having mutual oppositely located feed and discharge ends on which there is arranged an elastic screening lining (54) and which are caused to oscillate by independent oscillating drives wherein the two screening frames (13 and 31) are associated with each other at different heights in such a way that the lower region of the upper screening frame (31) and the upper region of the lower screening frame (13) lie in a common plane, that the elastic screening lining (54) is secured to the two screening frame (13, 31) in the common plane thereof and that the upper screening frame (31) is independently driven in a circular configuration at the feed end and the lower screening frame (13) is indepndently driven in a circular configuration at the discharge end.

Abstract: A screening machine in which screens or portions of screens of elastic material and having substantially the shape of conical frustums are arranged one below the other. The circular edges of the screens are supported by holders which are mounted to a rotating shaft by means of bearings. The bearings of alternate holders being mounted on eccentric crank pins to drive such holders, without their rotating, in a substantially circular horizontal oscillatory motion to impart to each screen a rapid vibratory motion in which every section thereof participates. The vibratory motion results from a portion moving into and out of tension in conjunction with the rotation of eccentric crank pins.