Importance

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Abstract

The small a.c. motor which is intended in particular for the oscillating drive of a toothbrush fastened to the armature shaft, has as the armature a cylindrical permanent magnet (4) magnetized diametrically, a stationary coil surrounding this permanent magnet at a clearance along its whole length, its turns running essentially rectangularly, and a tubular stator case (1) surrounding the coil and of rectangular cross-section, to which the outer periphery of the coil being adapted. The coil is composed of two equal part-coils (2,3) and orientated with its axis perpendicular to the axis of the armature and its planes of winding lie essentially in parallel with the large sidefaces of the stator (1). The two part-coils (2,3) rest against one another at faces orientated in parallel with their planes of winding in a plane passing through the armature axis, and their edges running diametrically to the armature have in the center semi-circular recesses (2a,2b,3a,3b,) for the passage of the armature shaft (5). Also on the armature there is a flywheel (4a) for adjusting the rotational inertia of the rota so that the natural frequency of the oscillation of the armature is lower than the supply frequency. In modifications the stator case may also be square octagonal, or cylindrical, the outer periphery of the coil being adapted to the inner periphery of the stator. In case of a cylindrical stator radically projecting stator pole pieces may be provided, lying opposite one another on its periphery.

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First Claim