Maintaining constant torque on rotary rabble in tank - for settling solids from suspension

摘要

The deposited sediment layer in a settling tank for suspensions is kept moving by a rotatably driven rabble. When the resistance to the stirring effect increases, the rabble is at least partly raised from the tank base and returned when resistance becomes normal. The raising is effected by a transmission member between the rabble and its drive unit which resolves the drive torque into a horizontal component (for rotation) and a vertical component (for lift). The transmission member may have a threaded spindle engaged inside a central threaded boss, or a pair of hydraulic piston units whose pressurised chambers are interconnected. The system does not require the hydraulic drive unit with its controls as used in similar known devices. The resistance of the solids layer to the stirrer and hence the drive torque needed are kept constant.