Structure for synchronous motor, especially stepper motor

Claim 1

In a synchronous motor, comprising, a pair of stators surrounding an armature space each stator being provided with a respective stator winding, each stator being comprised of a first pole teeth plate, a stator housing and a second pole teeth plate with the teeth of the first plate of each stator being interdigitated with the teeth of the second plate of the same stator but not with the teeth of the other stator and extending generally in axial direction of the motor radially outwardly of the armature space but radially inwardly of the respective stator winding, the angular spacing between a point on a pole tooth of the first plate of one stator and the corresponding point on the neighboring pole tooth of the second plate of the same stator constituting one pole pitch, the stators being arranged coaxially but angularly offset relative to each other by half the pole pitch, the first plates being identical to each other and arranged back-to-back with the second plates being separated from each other by the two first plates, each first plate having at its outer periphery a first engaging portion, each stator housing having a complementary second engaging portion, the first engaging portion of each first plate cooperating with the complementary second engaging portion of the housing of the same stator to establish the angular relationship between such first plate and such stator housing, each first engaging portion on a first plate being angularly offset relative to the neighboring tooth of the same first plate by half the pole pitch, each second engaging portion on a stator housing being angularly offset relative to the neighboring tooth of the second plate of the same stator by half the pole pitch, each first plate having at least two third engaging portions, on each first plate the first engaging portion and the neighboring tooth of the same plate together defining an angle which is bisected by a line relative to which the third engaging portions of the same plate are symmetrically disposed, the third engaging portions of one first plate congruently registering with the third engaging portions of the other first plate, with the first engaging portion of one first plate being angularly offset relative to the first engaging portion of the other first plate by half the pole pitch.