A lifting mechanism for a raking structure in a solids-liquid separation tank comprising a fixed column adapted to extend vertically within the tank, a movable column being adapted to support a raking structure for the tank, and a lift device for raising and lowering said movable column telescopically with respect to said fixed column. The lift device includes an elongate flexible tension member; a first series of load points on the fixed column at spaced intervals on the fixed column; and a second series of lift points on the movable column below said first series of points and at spaced intervals on the movable column, the tension member being alternately threaded between load and lift points of said first and second series of points, with the tension member thus being led over one of said load points, down and below one of said lift points and back up and over the next load point. A power driven drum is provided means for selectively pulling and paying out said tension member for drawing the lift points up toward the load points for raising the movable column, and for allowing the lift points to move down away from the load points for lowering the movable column, respectively.