Pump impeller and coupling magnet structures

In a magnetically coupled pump having a rotary impeller and a magnet well in which a cylindrical coupling magnet attached to the impeller rotates with the cylinder axis in alignment with the axis of rotation of the impeller and the outer cylindrical periphery of the magnet rotating in a narrow clearance space confronting wall portions of said well, improvements comprising:

• a coupling magnet in attachment to the impeller as aforesaid and formed in one homogeneous piece as a cylindrical tube of a magnetic composition of the ceramic type including barium ferrite, and guard means embracing the cylindrical aspect of the magnet body at least along portions of the axial length thereof, and comprising effectively non-magnetic band means extending in a circumferential direction about the cylinder axis to substantially encircle said body within a predetermined peripheral boundary subjoining the outer cylindrical surface thereof so as to lie wholly within said clearance space and serving to confine fragmented portions of the magnet body resulting from fracture and faulting within the body against displacement into the clearance space.

In a centrifugal pump having an impeller with a driven coupling magnet sealed within a pump housing to rotate under the influence of an externally rotating driving magnet, the improvements which comprise:

• sealing the driven magnet against fragmentation and chemical attack by means of a thin-walled plastic shell enveloping the external surfaces of the magnet and providing said impeller with an axial hub extension at one axial side thereof, the annular bore of the driven magnet being tightly fitted upon said extension with an axial end wall portion thereof closely juxtaposed to said axial side of the impeller wherein said juxtaposed side and wall portion are provided with complementary interengaging formations keying the impeller and magnet against relative rotative displacement.