Pump impeller

Claim 1

IN A PUMP, THE COMBINATION OF A CASING HAVING A VOLUTE OUTLET CHAMBER AND A FLARING INLET BORE DEFINED BY A SURFACE OF REVOLUTION, THE LARGE END OF SAID FLARING INLET BORE OPENING INTO SAID VOLUTE OUTLET CHAMBER, AN IMPELLER MOUNTED TO ROTATE WITHIN SAID FLARING INLET BORE, SAID IMPELLER HAVING A FIRST FLARING HUB PORTION CONCENTRICALLY MOUNTED IN SAID FLARING INLET BORE AND FLARING IN THE SAME AXIAL DIRECTION BUT HAVING A SUBSTANTIAL LESSER DIAMETER AND EXTENDING INTO SAID VOLUTE OUTLET CHAMBER, A SECOND OFFSET HUB PORTION MERGING WITH THE FIRST HUB PORTION AND EXTENDING UPSTREAM AND CONVERGING FROM THE FIRST HUB PORTION AND HAVING AN AXIS ANGULARLY OFFSET WITH RESPECT TO THE AXIS OF THE FIRST HUB PORTION, AND MERGING THEREWITH SO AS TO PROVIDE A SMOOTH CONTINUOUS SURFACE WITH SAID FIRST FLARING HUB PORTION, A SINGLE CONTINUOUS SPIRAL SCREW BLADE OF SUBSTANTIALLY CONSTANT THICKNESS ENCIRCLING SAID FIRST AND SECOND HUB PORTIONS AND EXTENDING AXIALLY UPSTREAM FROM SAID SECOND OFFSET HUB PORTION, SAID SCREW BLADE HAVING A LEADING END INCLINED TO SAID AXIS OF SAID FIRST HUB PORTION AND SAID SCREW BLADE HAVING AN OUTER EDGE THAT ON THE ROTATION THEREOF SAID EDGE DEFINES A SURFACE OF REVOLUTION CONCENTRIC WITH SAID FLARING INLET BORE AND CLOSELY ADJACENT THERETO, AND SAID SCREW BLADE HAVING A ROOT PORTION ENGAGING AND MERGING INTO A SMOOTH SURFACE WITH SAID OFFSET AXIALLY EXTENDING SECOND HUB PORTION SO THAT NO ABRUPT SHOULDER IS FORMED BETWEEN SAID ROOT PORTION OF THE SCREW BLADE AND THE SURFACE OF SAID OFFSET SECOND PORTION OF THE HUB.