Traditionally, permanent magnets have not been a practical means for moving a first object with a second magnetically attached object for applications where the direction of movement of the first object is perpendicular to the direction of magnetization of the magnets unless an electromagnetic field is applied to the permanent magnets to effect their magnetic properties. Because shear forces between two magnets or between a magnet and metal are low compared to tensile forces, the size of the magnet(s) required to achieve shear forces necessary to maintain attachment of two objects during such movement makes them impractical due to size, weight, cost, and safety reasons. For example, magnets strong enough to attach a blade of a blender or food processor would need to be substantially large to maintain attachment of the blade during normal use of the appliance and would therefore be very difficult to remove, expensive, and generally unsafe in a kitchen environment where lots of metal is present such as stove tops, utensils, and even the blade itself.
Magnetic drives involving electromagnetic fields and permanent magnets have been used to magnetically attach a magnetic structure to magnetizable material associated with blades in blenders, for example, as described in U.S. Pat. No. 6,210,033, to Karkos et al. Such magnetic drives require a rotating electromagnetic field to be produced and maintained to enable attachment of the magnetic structure to the magnetizable material during operation of the blender.
Therefore, it is desirable to provide improved systems and methods for moving an object using magnetic structures that do not require electromagnetic fields to be produced.
USPTO Backgrounds
USPTO Backgrounds