Abstract: Described herein is a device for cleaning a sewer of a kind which, under action of the flowing sewage, is carried along the sewer by the sewage with a velocity less than the average velocity of sewage flow and which comprises a hollow cleaning ball immersing into the sewage and rolling on the bed or ceiling of the sewer. The outer surface of the cleaning ball has protrusions, the outer surface of the protrusions lie on an imaginary spherical surface. For adapting the effective weight of the cleaning ball to different levels of sewage in the sewer, several water through holes are distributed on the spherical wall of the cleaning ball which open into a sewage space within the hollow cleaning ball at a wall surface on which filth guiding ribs are. The filth guiding ribs end close to the openings of the water through holes.

Abstract: The bottom portion of a drain or sewer, partially filled with flowing liq, is cleaned by placing a cleaning member therein. The cleaning member rolls freely along the bottom portion of the sewer at a lower speed than the flowing liquid. The interior of the cleaning member contains a braking material and throttle structure which tend to reduce the rolling speed of the cleaning member. The cleaning member has an asymmetrical outer surface formed by a plurality of non-intersecting ribs which are asymmetrical with respect to all meridian planes defined by a plurality of rolling meridians along which the cleaning member can roll. This asymmetrical outer surface structure induces a corresponding asymmetric liquid flow around the cleaning member and downstream thereof; thereby laterally deflecting the downstream flow and suspended contaminants out of the rolling path of the cleaning member.