Importance

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Abstract

A magnetic induction drive for a rotatable driven member in a sealed housing, in particular, a shaft-mounted blade in a blender cup or a shaft-mounted blade in an ice shaver, uses a comparatively thin circular drive plate of a magnetizable material with circumferentially arrayed poles enclosed within a housing secured to a drive shaft. A brushless d.c. motor in a base separate from the housing has a rotor formed as an array of pie-shaped permanent magnet regions that interact with an electronically controlled, rotating electromagnetic field produced by a ring of stator coils. A second such permanent magnet is coupled to rotate coaxially and in unison with the rotor, with poles of opposite polarity aligned and adjacent one another. A steel disc is sandwiched between and bonded to the rotor and the second permanent magnet. The magnetic field (lines of flux) of the second magnet extends axially away from the rotor to induce magnetic poles of opposite polarity in the drive plate. This second magnet-to-plate magnetic coupling operates across a closely-spaced gap that includes the bottom wall of the base, the upper wall of the housing, and air gaps between these walls, and the plate and the second magnet. A gear train assembly can be coupled to the drive shaft to increase or decrease the amount of torque transmitted from the drive plate to the driven member.

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First Claim