Patent ID: 7520986

Claim:
A filtration device comprising: a filtration tank, having a filter bed for supporting a layer of particulate filtration media; a vertically oriented hollow cleansing tank having an opening at the lower end thereof, provided in the filtration tank; a screw conveyor within the cleansing tank, for conveying the filtration media upwards; the screw conveyor has a shaft, which is suspended within the filtration tank from above; the upper portion of the shaft is driven, and the lower portion of the shaft is supported by an axial support section, which is fixed in the opening at the lower end of the cleansing tank; and a frictional wear compensating mechanism is provided at a portion of the axial support section where the shaft and the axial support section contact each other; and a contaminant expulsion mechanism, for expelling contaminants separated from the filtration media during cleansing to the exterior of the filtration tank.