Abstract: A filter assembly contains a filter drum provided with a stationary air pervious cylindrical filter jacket. The axis of the filter drum preferably extends approximately horizontally. A rotating hollow shaft extends through the filter drum and in radial direction is rigidly connected for rotation to at least one suction nozzle. This suction nozzle serves for sucking-off solid materials through the rotating hollow shaft, these solid materials being separated at the inside of the filter jacket. The hollow shaft carries at least one carriage or slide which is rigidly mounted for rotation in radial direction upon the hollow shaft. For performing oscillating movements in axial direction upon the hollow shaft, this carriage or slide is connected to a device for guiding the at least one suction nozzle along the undulated or wave-shaped path over the inside of the filter jacket.