Discharge control for hydraulic classification

Claim 1

IN THE HYDRAULIC CLASSIFICATION OF SOLID PARTICLES BY HINDERED SETTLING IN A LIQUID FILLED CLASSIFIER COLUMN WHEREIN ACCUMULATING SOLIDS OF DESIRED CHARACTER FOR SEPARATION CREATE A LIQUID-SOLIDS MIXTURE HAVING AN INCREASED DENSITY RELATIVE TO THE LIQUID ALONE, IN THE CLASSIFIER COLUMN AT A PREDETERMINED REGION OF SUCH ACCUMULATION, THE METHOD OF WITHDRAWING A PULP OF SAID ACCUMULATING SOLIDS FROM SAID REGION WHICH COMPRISES ESTABLISHING A HYDROSTATIC COLUMN OF LIQUID EXTENDIG UPWARDLY FROM SAID REGION, SUPPLYING ADDITIONAL LIQUID TO AN UPPER LOCALITY OF SAID HYDROSTATIC COLUMN UNDER CONSTANT PRESSURE FOR CONTINUOUS FLOW OF SAID LIQUID DOWN THE HYDROSTATIC COLUMN INTO THE LIQUID BODY IN THE CLASSIFIER COLUMN, SAID INCREASED DENSITY AT SAID REGION BEING EFFECTIVE TO ELEVATE LIQUID IN THE HYDROSTATIC COLUMN TO A CORRESPONDING DISTANCE ABOVE THE UPPER LEVEL OF LIQUID IN THE CLASSIFIER COLUMN AND SAID SUPPLY OF WATER INTO THE HYDROSTATIC COLUMN BEING EFFECTIVE TO PROVIDE ADDITIONAL ELEVATION OF SAID LIQUID IN THE HYDROSTATIC COLUMN TO A PREDETERMINED CONTROL REGION, AND INITIATING AND CONTROLLING DISCHARGE OF PULP FROM SAID FIRST-MENTIONED REGION OF ACCUMULATION OF SOLIDS IN ACCORDANCE WITH PRESENCE AND ABSENCE, RESPECTIVELY, OF LIQUID IN THE HYDROSTATIC COLUMN AT A PREDETERMINED LEVEL IN SAID LAST-MENTIONED CONTROL REGION.