A high performance stepper motor comprises a stator having a plurality of pole positions. Each of the pole positions includes a plurality of stator elements or teeth on opposite sides of a stator-to-stator air gap with nonmagnetic material located in the spaces between the extremities of the teeth. Energization means in the form of a plurality of windings adapted to be connected to a multiphased drive source are associated with the stator means at the various pole positions respectively. Motive means comprising a rotor or a slider includes a plurality of motive elements which comprise teeth or slugs. In order to further achieve low inertia and a high force-to-mass ratio of the passive means, the motive means comprises discontinuities in the magnetic material thereof including nonmagnetic material between the extremities of the motive elements so as to reduce flux leakage in the direction of movement of the passive means through the air gap while simultaneously reducing the mass of the motive means.

A high performance stepper motor comprises a stator having a plurality of pole positions. Each of the pole positions includes a plurality of stator elements or teeth on opposite sides of a stator-to-stator air gap with nonmagnetic material located in the spaces between the extremities of the teeth. Energization means in the form of a plurality of windings adapted to be connected to a multiphased drive source are associated with the stator means at the various pole positions respectively. Motive means comprising a rotor or a slider includes a plurality of motive elements which comprise teeth or slugs. In order to achieve low inertia and a high force-to-mass ratio, the motive means is located within and confined to the air gap of the stator. The motive elements comprise magnetic material and have extremities juxtaposed to the extremities of the stator elements on both sides of the air gap so as to establish flux paths transverse to the air gap and movement of the motive means relative to the stator means with the resulting force acting on the motive elements at both sides of the air gap. In order to further achieve low inertia and a high force-to-mass ratio of the passive means, the motive means comprises discontinuities in the magnetic material thereof including nonmagnetic material between the extremities of the motive elements so as to reduce flux leakage in the direction of movement of the passive means through the air gap while simultaneously reducing the mass of the motive means. By utilizing a passive means of this type, the energization means may be limited to one side of the air gap to achieve manufacturing economies and topological advantages while at the same time achieving high performance.

A serial impact printing element is mounted on the slider of a high performance linear stepper motor. The slider moves through the stator-to-stator air gap of the linear motor stator comprising an active stator portion having windings associated therewith and a passive stator portion without windings. In order to achieve high performance of the motor, the slider is relatively short as compared with the stator, and longitudinal flux leakage through and the weight of the slider are minimized by the use of nonmagnetic discontinuities therein. The impact printing element includes a wheel having a plurality of circumferentially spaced character elements which are rotated to the printing position by means of a rotary stepper motor. Since there are no windings on the passive portion of the stator, the character elements of the wheel are able to pass in close proximity to the passive portion thereby allowing the center of gravity of the rotary motor to be low so as to achieve stability of the impact printing element during high speed operation.