Variable performance pump

A variable width impeller centrifugal pump comprising a. a rotatable impeller having vanes thereon and holes therethrough and having two concentric cylindrical fits on the back side thereof;

• b. an impeller shroud having slots thereon through which the vanes of said impeller pass. c. a pump housing having an inlet and outlet section encompassing the impeller and impeller shroud, said pump housing having one cylindrical fit integral with said housing, said housing having an opening therein on the back side thereof;
• d. a piston arrangement integral with said impeller shroud adapted for axial and rotatable movement having two extending means thereon to axially move within the three cylindrical fits said extending means being movable between the cylindrical fit on said housing and one of said cylindrical fits on said impeller, the others of said extending means being movable within the other of said cylindrical fits on said impeller so that an area on the impeller side of said piston is sealed by said impeller cylindrical fits, said area communicating with said inlet by means of said holes through said impeller, said piston also being partially sealed by said cylindrical fit on said housing so that leakage through said fit on said housing provides pressure to the piston on the side opposite said impeller;
• e. means for controlling the pressure on the piston side away from the impeller, said means communicating with the inside of said housing through the opening in the rear of said housing.