Pulse motor

Claim 1

A thin, reversible, pulse-actuated motor for use in a timepiece, said motor comprising: a circular rotor formed as a single member of small axial dimension rotatable about an axis and having a plurality of angularly spaced permanent-magnet poles of alternating magnetic polarity, the arc distances between the centers of the successive rotor poles being equal; a planar stator rotatably receiving said rotor and coplanar therewith, said stator having: a pair of arc-segmental pole pieces directly opposite one another across said axis, one of said pole pieces extending arcuately around said rotor over an arc length in excess of 180° and being circumferentially spaced from the other of said pole pieces by a pair of air gaps, each of said pole pieces defining a pair of arcuate stator poles connected together by a thin arcuate connecting member; respective yokes connecting the stator poles of said pair of pole pieces which are separated by each of said gaps, each of said yokes having: a first shank integral with the respective stator of said pole pieces, a second shank parallel to the respective first shank and integral with the respective stator pole of said other pole piece, and a member bridging the first and second shanks of each yoke; and a respective exciting coil on each of said second shanks, said coils being the only coils of said motor and being energizable, said pole pieces being spaced from said rotor by constant and equal distances, the arc lengths of each of said stator poles being less than 360°/n where n is the number of rotor poles.