Stator assembly for stepping motor

Claim 1

In a stepping motor of the type having first and second stator members in spaced apart, overlapping relation to define a gap therebetween in which a rotor disc is mounted on a central axle for rotation and having a coil magnetically coupled to the first and second stator members, the improvement comprising: (a) a magnetically permeable first stator member having a central hub, multiple spoke-like first pole pieces radiating from the hub with at least one of said first pole pieces extending beyond said rotor disc in a first direction forming a first motor arm and a central aperture in the hub through which one end of the rotor axle extends for rotation; (b) a stator bridge assembly comprising a magnetically permeable second stator member having a central hub and multiple spoke-like second pole pieces radiating from the hub in spaced, overlapping relation to the hub and pole pieces of the first stator member with at least one of said second pole pieces extending beyond said rotor disc forming a second motor arm in a second direction from said first motor arm for providing spaced, non-overlapping relation between said first motor arm and said second motor arm for substantially reducing magnetic losses and further comprising a non-magnetically permeable plastic holder member united to the second stator member, said second stator member having a central aperture in the hub axially aligned with the central aperture of the first stator member and said plastic holder member having portions forming a bushing in the central aperture of second stator member for receiving the other end of the rotor axle with remaining portions of the plastic holder member forming a support bridge between the first and second stator members; and (c) means for holding the stator bridge assembly and first stator member together.