Centrifugal pump

Claim 1

A MULTI-STAGE CENTRIFUGAL PUMP FOR PUMPING FLUID FROM A MAIN PUMP INLET THROUGH SUCCESSIVE STAGES TO A MAIN PUMP OUTLET, A SHAFT, A PLURALITY OF PUMP IMPELLERS EACH HAVING AN IMPELLER INLET IN THE FRONT SIDE AND IMPELLER PASSAGES EXTENDING FROM THE IMPELLER INLET TO THE PERIPHERY OF THE IMPELLER, SAID IMPELLERS EACH HAVING AN IMPELLER HUB SLIDABLY AND NON-ROTATABLY MOUNTED ON THE SHAFT FOR FREE AXIAL FLOAT THEREON WITH THE HUBS ON ADJACENT IMPELLERS AXIALLY SPACED APART ALONG THE SHAFT, A PORTION OF THE HUB EXTENDING AXIALLY TOWARD THE IMPELLER INLET AND HAVING ONE END DISPOSED AT A LEVEL ADJACENT THE IMPELLER INLET, A PUMP CASING SURROUNDING THE IMPELLERS AND INCLUDING A PLURALITY OF INLET WALLS EACH SPACED AXIALLY FROM THE FRONT SIDE OF A RESPECTIVE IMPELLER AND A PLURALITY OF DIFFUSER WALLS EACH SPACED AXIALLY FROM THE REAR SIDE OF A RESPECTIVE IMPELLER, INTERMEDIATE ONES OF THE DIFFUSER WALLS HAVING SLEEVE PORTIONS IMMEDIATELY SURROUNDING THE SHAFT BETWEEN THE ADJACENT ONES OF THE HUBS AND EXTENDING FROM THE DIFFUSER WALL TOWARD THE HUB ON THE IMPELLER OF THE NEXT SUCCEEDING PUMP STAGE, EACH IMPELLER AND THE ADJACENT INLET WALL OF THE PUMP CASING HAVING OPPOSED SEAL FACES AROUND THE IMPELLER INLET TO LIMIT RECIRCULATION OF FLUID THEREBETWEEN, AND A HUB THRUST BEARING MEANS FOR EACH IMPELLER SURROUNDING THE SHAFT AND DEFINING OPPOSED AXIALLY FACING BEARING FACES BETWEEN SAID ONE END OF EACH HUB PORTION AND THE END OF THE ADJACENT SLEEVE PORTION FOR LIMITING MOVEMENT OF THE IMPELLERS IN A DIRECTION TOWARD THE PUMP INLET TO CONTROL WEAR ON SAID IMPELLERS AND SAID INLET WALLS OF THE PUMP CASING WHEN SAND OR OTHER ABRASIVE MATERIAL IS PRESENT IN THE WATER BEING PUMPED, THE OUTER SURFACES OF THE HUB PORTIONS AND SLEEVE PORTIONS DEFINING THE INNER BOUNDARY OF THE FLOW PASSAGE THROUGH THE IMPELLER INLET AND SAID HUB THRUST MEANS HAVING ITS OUTER PERIPHERY ADJACENT THE OUTER SURFACES OF THE HUB PORTIONS AND SLEEVE PORTIONS AND BEING LOCATED AT A LEVEL ADJACENT THE INLET OF THE IMPELLER WHEREBY FLUID FLOWING THROUGH THE IMPELLERS TENDS TO CARRY ANY FOREIGN MATTER THEREIN PAST THE HUB THRUST BEARING.