Stuffing box construction

Claim 1

IN A FILTER APPARATUS FOR USE IN COMBINATION WITH ABRASIVE MATERIAL WHEREIN SAID APPARATUS COMPRISES A ROTATABLE DRUM INCLUDING POROUS WALL PORTIONS, SAID DRUM INCLUDING A SHAFT AND A BEARING CARRYING SAID SHAFT, AND WHEREIN IN THE OPERATION OF SAID APPARATUS THE AXIS DEFINED BY SAID SHAFT IS LOCATED BELOW THE LEVEL OF SAID ABRASIVE MATERIAL, THE IMPROVEMENT COMPRISING A STUFFING BOX COMPRISING A HOUSING, A FIRST ANNULAR CHAMBER DEFINED BY SAID HOUSING, A FIRST PLASTIC PACKING INCLUDED WITHIN SAID CHAMBER AND SURROUNDING SAID SHAFT IN CLOSE FITTING RELATIONSHIP THEREWITH, A SECOND PLASTIC PACKING INCLUDED WITHIN SAID SECOND CHAMBER AND SURROUNDING SAID SHAFT IN CLOSE FITTING RELATIONSHIP THEREWITH, SAID SECOND CHAMBER AND PACKING BEING LOCATED BETWEEN SAID FIRST CHAMBER AND SAID BEARING, A PRESSURE SURROUNDING SAID SECOND PACKING, FLEXIBLE TUBULAR MEMBER SURROUNDING SAID SECOND PACKING, MEANS FOR INTRODUCING FLUID UNDER PRESSURE INTO SAID TUBULAR MEMBER FOR INCREASING THE PRESSURE APPLIED BY SAID SECOND PACKING TO SAID SHAFT, AN OPEN SPACE DEFINED BETWEEN SAID PACKINGS, AND MEANS FOR INTRODUCING FLUID UNDER PRESSURE INTO SAID OPEN SPACE.