A capacitive position sensor has a two-layer electrode structure. Drive electrodes extending in a first direction on a first plane on one side of a substrate. Sense electrodes extend in a second direction on a second plane on the other side of the substrate so that the sense electrodes cross the drive electrodes at a plurality of intersections which collectively form a position sensing array. The sense electrodes are provided with branches extending in the first direction part of the way towards each adjacent sense electrode so that end portions of the branches of adjacent sense electrodes co-extend with each other in the first direction separated by a distance sufficiently small that capacitive coupling to the drive electrode adjacent to the co-extending portion is reduced. Providing sense electrode branches allow a sensor to be made which has a greater extent in the first direction for a given number of sense channels, since the co-extending portions provide an interpolating effect. The number of sense electrode branches per drive electrode can be increased which allows a sensor to be made which has ever greater extent in the first direction without having to increase the number of sense channels.

Capacitive position sensor

A brushless DC motor having a hydrodynamic bearing system includes a stator core having windings arranged thereabout, the stator core rotating about a first center line. The motor further includes a rotor having permanent magnets positioned about an inner diameter thereof, said rotor being rotatable about a second center line. The first center line of the stator core is eccentric to and parallel to the second center line of the rotor such that the magnets exert forces on the stator core which eliminate whirl instability in the rotor.

Brushless DC motor having a stable hydrodynamic bearing system

An oscillating tool, particularly a cast cutter (40) having a support housing (46) with a cutting blade (70) interconnected to the housing (46) proximate one end thereof for oscillatory rotational movement about an axis (56). A torsion shaft (54) is fixedly interconnected at a first end (102) to the housing (46) so as to prevent rotational oscillation at the first end of the torsion shaft (54). The torsion shaft (54) further has a free second end (100) enabling oscillatory rotational movement of the second end (100) generally about the axis (56) of the cast cutter blade (70). A hollow tubular rotor support member (58) substantially more rigid than the torsion shaft (54) is attached to the torsion shaft (54) proximate the second free end (100) of the torsion shaft (54). The hollow tubular rotor support member (58) is concentrically positioned about the torsion shaft (54) and extends from proximate the second end (100) of the torsion shaft (54) along a major portion of the torsion shaft (54) toward the first end (102) of the torsion shaft (54). The cutting blade (70) is interconnected to the hollow tubular rotor support member (58) and torsion shaft (54) arrangement proximate the second end (100) of the torsion shaft (54) for oscillatory rotational movement therewith. A magnetically interactive rotor (60) is fixedly attached to the hollow tubular rotor support member (58) at a location axially removed from the cutting blade (70) for oscillatory rotational therewith. A magnetically interactive stator (66) axially adjacent but radially removed from the rotor (60) induces rotational oscillation of the rotor (60) and consequently the tubular member (58). Accordingly a rotational oscillatory movement of the cutting blade (70) is provided.

Cast cutter apparatus

A flat type DC motor applicable for disc drive of an electronic still camera in which vibrations of the rotor axle are prevented without increasing manufacturing costs by providing the magnetic field between the stator and rotor to by asymmetrical so that the magnetic attracting force of the rotor to the stator is also asymmetrical. The asymmetrical attracting force causes the axle of the rotor to be urged in the same radial direction relative to the axle bearing in the stator, thus, movements of the axle in radial directions in the clearance between the axle and bearing of the stator are eliminated and the rotor rotates without vibrating.

Structure of a flat-type brushless DC motor

An electric rotary actuator for producing rotation through a limited angle comprises a rotor winding made of a plurality of thin loop coils arranged in a continuous cylindrical framework as part of a rotor shell. The rotor shell lies in an annular flux gap defined by a stator magnet assembly and a flux return means. Each pair of adjacent axially extending limbs of adjacent loop coils lies opposite to and cooperates with a respective stator pole face. This winding arrangement helps to optimize the torsional resonance characteristics of the rotating mass.

Limited angle electric rotary actuator

A limited rotation motor has a stator and a rotor mounted for limited rotation relative to the stator. The stator is constructed to conduct bias flux through magnetic circuits that extend across air gaps between the stator and the rotor and a drive system produces drive flux which is conducted through magnetic circuits that extend across air gaps between the stator and rotor to drive the rotor. The stability of radial rotor position in its support bearings is enhanced by an imbalance in the bias flux magnetic circuits which continually produces a resultant radial force on the rotor so that a well defined radial position of the rotor is maintained over the range of limited rotation that the rotor moves in response to the drive system.

Pierre J. Brosens

Papers

Limited rotation motor