Skimming mechanism for square tanks

Claim 1

In a non-circular tank for containing a liquid with a constant liquid level and having an inlet, a peripheral outlet and sludge removal means which includes a collector arm extending over the floor of the tank and which rotates about a vertical axis at the center of the tank; a beach and scum trough fixed to and projecting from a wall of the tank, a track carried by the walls of the tank and extending around the tank, radially arranged guide means carried by the collector arm, a wheeled carriage operable on said track and a radial control arm movable lengthwise in said guide means, said carriage and arm being pivotally interconnected to form a support which follows the track around the tank while being rotated around the tank by the rotation of the sludge collector, an outer skimming blade carried by said support and disposed to follow the tank wall and operate over the trough and beach, an inner skimming blade carried directly by the sludge collector arm and extending radially from near the center of the tank, and an intermediate skimming blade carried by said control arm in telescopic relation with said inner blade and extending to the outer blade whereby the three blades provide skimming of the entire surface of the liquid in the tank.