Axial thrust compensation for centrifugal pump

Claim 1

A centrifugal pump of the type having a casing, an axial fluid inlet (6) in said casing, a rotatable impeller (1, 2, 3) in said casing having an inlet area on its front surface opposite said fluid inlet (6) of the casing, said rotatable impeller (1, 2, 3) subjected to the fluid pressure in said fluid inlet (6) of the casing and possessing a shrouded area on the front surface extending radially outward from said inlet area subjected to increased fluid pressure imparted by said impeller (1, 2, 3) when said pump is operating, said rotatable impeller (1, 2, 3) forming a unit with an annular rotor (4, 21) driven by magnetic forces, the impeller rotor unit (1, 2, 3, 4, 21) being centered in the bore (18) of the rotor (4, 21) and supported in the axial direction to counterbalance axial magnetic forces by bearing means (13, 24) by which said impeller is mounted for rotation and which are located adjacent to the rear plate (3) that divides the impeller (1, 2, 3) from the rotor (4, 21), magnetic means for effecting a magnetic couple with an inductive drive means (4, 21), which is separated by a magnetically permeable separating wall (12) which forms a narrow gap (16) with the rotor (4, 21); the improvement comprises channels (17) arranged in said rear plate (3) and communicating on the periphery of the impeller (1, 2, 3) with the pressure side compartment (5) of the pump and on the inner side with the gap (16).