The invention relates to rotors of electrical motors or magnetic couplings which exhibit a spherical magnetic airgap between the rotor and the driving stator or an outer magnetic ring driven by a motor. Such spherical motors or spherical magnetic couplings are becoming more and more important in modern pump design. The rotors or spherical motors or couplings are held in position by magnetic forces pressing the rotor against a stationary mounted ball. The impellers of pumps which form a unit with the driven rotor produce hydraulic thrust counteracting the magnetic thrust. When the electricity is switched off, the magnetic force of the driven stator stops immediately. In contrast, the hydraulic thrust, caused by the difference of pressure generated by the rotating impeller, decreases slowly as the rpm of the impeller decreases. The result is a tendency of the hydraulic forces to lift the impeller and the rotor away from the step bearing. The same change in the direction of axial thrust occurs in magnetic couplings, if the hydraulic forces can exceed the magnetic forces during operation. It is therefore necessary to support the rotor not only in the direction of the magnetic forces, but also to prevent movement in the opposite direction by means of a spherical bearing consisting of a cap and a ball. The fact that the rotor is supported by a step bearing makes it necessary, for the stator to point downwardly after installation. This is a serious drawback. Several methods are known for preventing movement in the opposite direction of the driving magnetic forces using mechanical means, such as the use of rings gliding on an undercut area of the ball. Their disadvantage is wear as well as unavoidable deformation during assembly.
USPTO Backgrounds
USPTO Backgrounds