Flip-flop screening machine

A flip-flop screening machine comprising:

• longitudinal supports each of which comprises a front wall and a rear wall, the longitudinal supports being configured to carry screen panels, the longitudinal supports being provided as a powered longitudinal support and as a non-powered longitudinal support, the longitudinal supports being arranged in a transverse direction of a direction in which a screened material is conveyed,
• wherein,
• at least every second of the longitudinal supports is provided as the powered longitudinal support,
• each powered longitudinal support is configured to perform at least one of oscillations and vibrations with movements in a transverse direction of a longitudinal axis of the powered longitudinal support so as to alternately compress and stretch the screen panels, and,
• each powered longitudinal support comprises over a substantial part of a length or over an entire length thereof a separate oscillatory or vibratory drive which is arranged between the front wall and the rear wall.