CA1143424A - Axial air-gap permanent magnet motor or generator with disc-type rotor - Google Patents

Abstract

A B S T R A C T

A disc-type motor characterized by increased efficiency is disclosed. The motor includes first and second parallel spaced stator members made of magnetic material in fixed relation, each of the stator members having a flat circular shape and an even plurality of pie-shaped permanent-magnet poles thereon, illustratively eight in number. The facing poles on the stator members have opposite polarities. The motor further includes a disc-like rotor made of a non-conducting material rotatably mounted between the two stator members.
Conducting wires are wound in a non-overlapping (single-layer) flat spiral configuration to form a number of coils equal to twice the number of poles per stator member, half adhered to each face of the rotor disc. Each coil encloses a pie-shaped area about equal to the area of one of the stator poles. On each face of the rotor the coils magnetically oppose one another, and the coils on one face of the disc are angularly offset from the coils on the other face of the disc. The motor further includes a commutator connected to the rotor, the commutator including twice as many bars of conducting material as there are coils on each rotor face, with certain of the commutator bars electrically inter-connected.

Description

3~LZ~

-`

Background of the Invention:
-This invention relates to electro-mechanical ~achinery, and more part1cularly to such machinery utilizing a disc-type rotor.

~ ~ .
,_,~ J~

~3~
1 Electrical machines, such as motor or generators, utilizing disc-type rotors are well known in the art. Such machines utilizing wires conventionally wound on the disc rotors are frequently unsatis-factory in that the rotors are undesirably bulky and irregular wind-ing arrangements are requirecl~ The arrangement oE conventional wires into a suitable winding pattern usually results in the cross-over of wires in the magnetic gap thereby resulting in a larye gap and a consequential reduction in flux in the air gap.
To overcome the aforementioned disadYantages, printed circuit-type machines in which a conductive pattern is coated on the faces oE a thln disc of insulating material to form the armature have been provided. An example of such a printed-type armature can be found in ~.S. Patent No. ~,970,238 issued to Swiggett on January 31, 1961. These types of motors provide a number of advantages. For example, these machines exhibit virtually no ma~netic flux distortion and no eddy current induc-tion. The printed circuit armature machines are urther advan-tageous in that they may include a large number of poles without increasing eddy loss and while increasing the back e.m.f. The printed circuit machines, however, suffer from the disadvantage that, when fabricating a high power machine, the thickness of the copper windings must be increased which is difficult to accomplish by etching techniques. Furthermore, the limitations of etching techniques are such that the minimum obtainable separations between armature conductors are on the or~er of twenty to thirty thousandths of an inch. This of course, limits the number of turns of wire which can be provided in a given area. In addition, etching techniques require thin metal conductors and this increases the resistance of the armature winding. The combination of relatively few turns in a given area combined with relatively .

3~;~4 1 high armature resistance results, of course, in a relatively low power machine. A further drawback to the printed circuit armature machine is that, because the conductive pattern is coated on the two faces of the disc-like armature, connections must be made between the conductors on both faces or sides of the disc. This involves clips or pads which extend over the outer and inner peripheral edges of the disc and these clips or pads must be soldered or welded to the conductors. The extremely large number of connectors required adds substantially to thé cost of ~anufacture and, in addition, substantially increases the likeli-hood of an open circuit (due to a weld or solder failure) in the winding.

.
9ummary of the Invention:

It is, therefore, an important object of the present invention to provide an improved electro-mechanical machine by means of which the aforesaid drawbacks and dlsadvantages may be most efficaciously avoided or minimized.

It is a further object of the invention to provide such a machlne which is characterized by increased efficiency.
It is yet another object of this invention to provide an electro-mechanical machine which is characterized by reduced distortion in its magnetic field.

It is still another objeet of the invention to provide an eleetro-meehanical machine having a dise-type rotor in whieh the armature coils on one face of the disc are eonneeted in simple rnanner to the coils on the other faee.

, ~

~ : , ~ 3~Z~

It is yet a further object of this invention to provide an electro-mechanical machine with wire-wound arma-ture in which each winding has a transverse thickness equal to the thickness of a single wire of the coil.
The invention is directed to an electro-mechanical machine comprising a stator means and a rotor means having generally flat faces in axially opposed relation. One of the stator means and rotor means has on a face thereof a circular array of 2N magnetic poles of alternately opposite polarity and the other of the stator means and rotor means has on a face thereof a circular array of coils in axial opposed rel-ation to the poles and a switching device synchronized with the roior means. In the electro-mechanical machine of the invention, the circular array of coils comprises a plurality of groups of coils with each group of coils being arranged on a respective segment of the face of the other of the stator means and rotor means and the coils of each group being in series with one another. Further in the invention described, the switching device is operatively connected to the groups of coils.
~ In the electro-mechanical machine described, there may be first and second stator members, each having an array of 2N magnetic poles of alternately opposite polarity where N is the number of pairs of such poles, each pole of one stator member being oppositeandspace~ from an opposite-polar-ity pole of the other stator member. The rotor means may be a disc armature rotor between the stator members and there may be a circular array of coils on each face of the disc rotor, each coil array being between the stator pole arrays.
The switching device may be a commutator rotatable together !-~
: ,~
~ : ' 3~f~

with the rotor and having 4N segments arranged in N sequell-tial sets of 4 sequential segments each, the N corresponding se~ments of each set being interconnected. The coil array on one rotor face may be angularly displaced relative to the coil array of -the other rotor face by one-half of the angular pitch between two adjacent coils. The coils on one-half of one face of the rotor may be connected together in series and to one pair of segments of the commutator segment sets. The coils on the other half of the one face of the rotor may be connected together in series and to the remaining pair of ; segments of the segment sets. The coils on one-half of the other face of the rotor may be connected together in series and to a segment of the one pair and a segment of the remain-ing pair. The coils on the other half of the other rotor face may be connected together in series and to the other seg-ment of the one pair and the other segment of the remaining pair. In the electro-mechanical machine described, the comm-utator may have at least one pair of brushes contacting the commutator, the brushes of each pair belng separated by an angle of substantially (n + 1/2) 36Q degrees, where n is an integer including zero. In the machine described, each array of coils may comprise 2 N coils on each face, arranged as arrays of N coils on each respective one-half face.
Brief Desc_~tion of the Drawings The foregoing and other objects and features of the present invention will be more clearly understood from the following detailed description thereof when read in conjunc-tion with the accompanyin~ drawings in which:
Figure 1 is an axial cross-sectional view of an electro-mechanical machine according to the invention;

- 4a -..i. ~
~::

~1~3~Z4 Figures 2A and 2B illustrate the two sides of an 8 pole armature wound according to the invention;
Figure 3, which appears on the same sheet as Figure 5, is a schematic diagram of a commutator arranged for use with the armature illustrated in Figures 2A and 2B;
Figures 4A and 4B illustrate both sides of a 12 pole armature disc wound according to the invention; and Figure 5 is a schematic diagram of a commutator arranged for use with the armature illustxated in Figuxes 4A and 4B.

~ .
:

~ :
: :

~ 4b -~39L24 Description of the Preferred Embodiment Turning now to Figure 1, there is illustrated a cross-sectional plan view of an electro-mechanical machine utilizing a disc-type armature. A housing-half 2 is connec-t-ed, by any conventional means, for example screws, one of which is indicated at 4, to another housing-half 6 to form the machine housing indicated generally at 8. Rotatably mounted within the housing 8 by means of front bearings 12 and rear bearings 14 is a shaft lO. Washers 1~ and 18 are positioned between the shaft 10 and the front and rear bear-ings, respectively. Within the housing 8 and mounted about the shaft 10 is an armature hub indicated generally at 20 which includes hub-half 22 and hub-half 24. The hub halves 22 and 24 are connected to one another and to the shaft so as to rotate therewith, as by a roll pin 26 passing through the two hub halves and the shaft lO. Suitably secured be-tween the two hub halves 22 and 24 to rotate therewith is a dlsc-shaped~rotor 28 made of a non-conducting, non-magnetic material, such as, for example, a phenolic. Secured to the rotor 28 as by adhesive or the like are a plurality of con-~ducting wires forming armature coils 30, which will be more fully discussed below. Fixedly connected to the machine housing 8 are first and second spaced stator members, indi-cated at 30 and 32. Each of the stator members 30 and 32 includes a plurality of flat pie-shaped permanent magnets, indicated at 34, which may, for example, be constructed of ceramic Eerrite. Each of the permanent magnets 34 is mag-neti~ed through thickness, so one face is of one polarity and the other face of opposite polarity. The magnets may be fixedly secured to a metal backing plate in the form of a r~

.

1~43424 ring made as of soft iron or steel, the two back-up rings being indicated at 36 and 38, respectively. The two back-up rings are fixedly connected to the housing 8 by any conven-tional means, for example, by countersunk screws, indicated at 40 and 42, respectively. Alternatively, the stators may be formed of ceramic ferrite dlscs, suitably ; :
::`

~: : : ::

, ~ ~

34;~4 magnetized to form the field poles.
Fixedly connected to the shaft 10 and rotating there-with is a commutator indicated generally at 44. The commutator 44 includes a plurality of segments or bars of a conductive material, such as, for example, copper, suitably isolated from one another by, for example, mica. The commutator is, of course, also electrically isolated from the armature shaft 10 on which it is mounted. Two of the copper bars of the commutator are indicated at 46 and 48. Fixed to the rear housing 6 is a brush holder mount ~0 to which is attached a brush holder 52 and a brush holder clip 54. A brush 56 is positioned between the brush holder 52 and the brush holder clip 54 and is main-tained in electrical contact with the commutator bar 46 by a spring 58 positioned between the brush 56 and the brush holder clip 54.
~ Other brushes, as needed, are similarly mounted in relation to `~ the commutator.
The permanent magnets 34 of the stator may advantageously be made of a ceramic ferrite and the back-up ring may be made of a magnetic material such as a soft iron or steel. It should be noted that the magnets 34 may be adhered, by means of an elastic cement, for example, to the soft steel back-up ring before the stator is magnetized.
It is here appropriate to note that the stator pole magnets 34 are, as previously indicated, in this example, made of ceramic ferrite material. Ceramic ferrite permanent magnets are utilized rather than alnico magnets, although, as is well known, alnico magnets have substantially greater strength than do ceramic ferrite magnets, since alnico is relatively expensive and is, therefore, not economically feasible for low-cost,battery-powered, motors. It is further noted that the individualpole pieces have 3~43~

a pie-shaped configuration so that the pole area for each is maximized. It is also possible to utiliæe a continuous ring of ceramic ferrite, magnetizing adjacent sections in alternate polarity, thereby further increasing the magnetic area, al-though this is less desirable since such a continuous ceramic ferrite structure is frangible and subject to breakage, even when adhered by means of an eIastic gl~le to the magnetic back-up ring. Utilizing individual pie-shaped pole pieces is pre-ferable since there is little reduction in total pole area and substantial reduction in the likelihood of stator break-age.
Turning now to Figures 2A and 2B, there are illus-trated the two sides of a winding pattern for an eight-pole rotor. A preferred arrangement in this embodiment is four groups of armature coils, which attains a reduced size of commutator brush circle and a more uniform coil distribution on the rotor disc. It will be noted that in this illus-tration only four wires are utilized, each wire forming the group of coils on one-half of each ~ace of the rotor disc 28.
As seen in Figure 2A, on the front face of the rotor one wire forms the four right-hand coils, and extends from a point A successively through four coils to point B.
A second wire extends from point C successively through four coils to point D. The coils are arranged so that current will flow in the same direction through the side-by-side conductors of adjoining coils. On the rear face of the rotor, as seen in Figure 2B, the coils are staggered 90 electrical degrees (one-half of the pitch angle of the stator poles) clockwise with respect to those on the front face. On this rear face, one wire starts at point B and extends through ., D~

3~2~

four successive coils to point C, while a further wire starts at point A and e~tends through four successive coils to point D. As shown below, points A, B, C, D are connected to respective sets of commutator segments. By winding each group of coils from a single piece of wire, a maximum of 8 connections to the commutator becomes necessary, regardless of the number of field poles.
In this preferred embodiment, all coils have the same number of turns (e.g. 8 turns). However, this is not essential; the coils may have different numbers of turns, although it is preferable that each of the pair of diametric-ally opposite coils on the same rotor face should have the same number of turns.
In manufacture, it has been found most efficient to wind the wire on a form to form an individual coil which conforms to the shape of the stator pole area. The wires are wound so that there is no overlap of the turns and they are therefore only a single layer thick. Each coil is then suitably adhered or otherwise secured to the rotor disc and connected as stated to the points A, B, C, D. It will thus be seen that the armature is a thin structure made up only of the thickness of the insulating disc plus -the thickness !

of two layers of the wire utilized, one layer of wire being on each side of the disc.
The arrangement permits the armature conductors to pass very close to the stator magnet surfaces on both sides of the rotor disc, permitting relatively large air gaps between the Eield magnets, in excess of 1/4 inch in some cases. This results in a larger copper area in the armature, with resultant increase in horsepower for a given size and z~

corresponding increase in efficiency. It also reduces the armature reaction problems of reversible motors. The exposed coil windings on the disc somewha-t increase the windage, but heat extraction is greater and higher continuous-duty ratings are possible for the same size wire. However, when high speeds are desired, windage may be reduced by cementing a thin (e.g. .002 inch) fiber glass or other smooth plastic disc to each face of the rotor disc. This thin armature structure also provides the advantage -that a mlnimum number of bars must be used in the commutator.
Turning now to Figure 3, there is illustrated a schematic diagram of a commutator for use with the armature illustrated in Figures 2A and 2B. It will be seen that the commutator 44 is arranged to have twice as many segments or bars as there are field poles. In this illustration there are four segments for each pair of stator poles and every fourth one of the sixteen segments forming the commutator (i.e., those indicated by the respective letters A, B, C and D) are electrically connected to one another by respective conductors, indicated at 70, 72, 74 and 76. Such connectors may be readily made by use of stamped jumper rings 62 (Fig.
1). While the coils of each group are preferably connected in series between the respective pair of commutator segments, it will be understood that they may be connected in parallel or in series-parallel. The commutator segments A, B, C, D
are respectively connected to points A, B, C, D on the rotor windings of Figures 2~ and 2B. The index markings in Figures 2A, 2B and 3 are utilized to enable the appropriate alignment of the commutator, the armature and the stator for maximum efficiency of operation of the machine. The maximum brush ~3~2~

width is preferably approximately 60% to 80% of the commu-tator bar width. Al-though such an arrangement gives a varying resistance as the armature rotates, the torque remains quite stable.
As seen in Figure 3, the two commutator brushes 22 are positioned at an angle such that one brush straddles segments A-B when tha other straddles segments D C. If there are ~ pole pairs, then the brush separation is ~n ~ 1/2) 360, where n is any integer from zero to N. For higher currents, several pairs of brushes may be used, each additional pair being spaced from the first pair by 90 or a multiple thereof.
Since brushes spaced by such intervals will contact inter-connected segments, such brushes may be connected in parallel. This not only permits larger currents and power, but reduces commutator arcing and ring fire.
Turning now to Figures 4A and 4B, there is illus~
trated an armature winding pattern for use with the disc rotor 2~ illustrating - 9a -' ~

~ 1~13~
a 12 pole configuration. In this structure, as well as with the structure illustrated in Figs. 2A and 2B, it will be noted that only four wires are used to wind the armature, one wire forming half the coils on each side of the disc. In this instance, the coils of each of the four groups are connected in series-parallel ~with 3 in series in parallel to another 3 in series) rather than in series as in the preceding embodiment. In this structure also, only non-overlapping spiral windings are utilized for the coils, resulting in coils having a thickness equal to that of a single wire.
Turning to Fig. 5, there is illustrated a commutator which is adapted for use with the armature illustrated ln Figs. 4A
and 4B. The commutator includes 24 segments (again twice the number of poles) and, in this embodiment, as was the case of the commutator embodimen~ illustrated in Fig. 3, every fourth bar of the commutator is connected together by means, for example, of electrical conductors indicated at 100. Again, one of the four coil groups is connected to segments A-B, another to C-D, a third to B-C and a fourth to D-A.
Although the preferred embodiment of the invention has been described with respect to 8 and 12 pole configurations, it will be understood that other numbers of poles may be used, with , ~as few as six poles or even more than twelve, depending on the size and speed of the motor. For example, 8 to lO poles may be used for small fractional horsepower motors, and larger numbers of poles for slower speed motors, which would increase horsepower and decrease weight.
The present invention provides a compact, low-weight, high-efficiency motor particularly applicable to moderate to low voltage portable battery or D.C. applications. Due to the low 3~2~

weight relative to power and the small amount of copper required, these motors are economical to produce. Efficiencies of 70 to 85%, depending on speed, are attainable. Power can be further increased by use of square rather than the customary round wire, with little change in weight.
Also, the same machine may serve either as a motor or a generator.
It will be understood that the foregoing description of the preferred embodiments of the present invention is for purposes of illustration only, and that the various structural and operational features as herein disclosed are susceptible to a number of modifications and changes none of which entail any departure from the spirit and scope of the present invention as defined in the appended claims.

Claims (33)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. An electro-mechanical machine comprising first and second stator members, each having an array of 2N magnetic poles of alternately opposite polarity where N is the number of pairs of such poles, each pole of one stator member being opposite and spaced from an opposite-polarity pole of the other stator member; a disc armature rotor between said stator members; a circular array of coils on each face of said disc rotor, each said coil array being between said stator pole arrays; a commutator rotatable together with said rotor and having 4N segments arranged in N sequential sets of four sequential segments each, the N corresponding segments of each set being interconnected; and wherein the coil array on one rotor face is angularly displaced relative to the coil array of the other rotor face by one-half of the angular pitch between two adjacent coils; the coils on one-half of one face of said rotor are connected together in series and to one pair of segments of said commutator segment sets; the coils on the other half of said one face of said rotor are connected together in series and to the remaining pair of segments of said segment sets; the coils on one-half of the other face of said rotor are connected together in series and to a segment of said one pair and a segment of said remaining pair; and the coils on the other half of said other rotor face are connected together in series and to the other segment of said one pair and the other segment of said remaining pair.

2. An electro-mechanical machine comprising first and second stator members, each having an array of 2N magentic - Page one of Claims - 12 poles of alternately opposite polarity where N is the number of pairs of such poles, each pole of one stator member being opposite and spaced from an opposite-polarity pole of the other stator member; a disc armature rotor between said stator members; a circular array of coils on each face of said disc rotor, each said coil array being between said stator pole arrays; and wherein said circular array of coils comprises a plurality of groups of coils with each group of coils being arranged on a respective segment of the rotor and the coils of each group being in series with one another;
a commutator rotatable together with said rotor and having 4N segments; and at least one pair of brushes contacting said commutator, the brushes of each pair being separated by an angle of substantially (n + 1/2) degrees, where n is an integer including zero.

3. A machine as claimed in claim 2 wherein said segments are arranged in N sequential sets of four sequential segments each, the N corresponding segments of each set being inter-connected.

4. A machine as claimed in claim 1 further comprising at least one pair of brushes contacting said commutator, the brushes of each pair being separated by an angle of substantially (n + 1/2) degrees, where n is an integer including zero.

5. A machine as claimed in any of claims 1 or 2 wherein said stator members are substantially planar and parallel and said array of poles is substantially circular.

- Page two of Claims - 13

6. A machine as claimed in any of claims 1 or 2 wherein said array of coils is substantially circular.

7. A machine as claimed in any of claims 1 or 2 wherein each of said coils is a one-layer spiral with non-overlapping turns mounted flat on said disc rotor.

8. A machine as claimed in any of claims 1 or 2 wherein each of said coils is made of square wire.

9. A machine as claimed in any of claims 1 or 2 wherein each of said coils spans an arc substantially the same as that of each of said stator poles.

10. A machine as claimed in any of claims 1 or 2 wherein each said array of coils comprises 2N coils.

11. A machine as claimed in any of claims 1 or 2 wherein each said array of coils comprises 2N coils, and wherein the coils are arranged in four groups, the coils on each half of each face of said rotor being interconnected.

12. An electro-mechanical machine comprising: first and second flat spaced parallel stator members, each having a circular array of 2N magnetic poles of alternately opposite polarity, where N is the number of pairs of such poles, each pole of one stator member being opposite and spaced from an opposite-polarity pole of the other stator member;
a disc armature rotor between said stator members; a circular array of 2N coils on each face of said disc rotor, each said coil array being between said stator pole arrays, each of said coils being a one-layer spiral with non-overlapping - Page three of Claims - 14 turns mounted flat on said disc rotor and being made of square wire, a commutator rotatable together with said rotor, and having 4N segments, wherein said segments are arranged in N sequential sets of four sequential segments each, the N corresponding segments of each set being interconnected, the coils on one-half of one face of said rotor are connected together in series and to one pair of segments of said commutator segment sets, the coils on the other half of said one face of said rotor are connected together in series and to the remaining pair of segments of said segment sets, the coils on one-half of the other face of said rotor are connected together in series and to a segment of said one pair and a segment of said remaining pair, the coils on the other half of said other rotor face are connected together in series and to the other segment of said one pair and the other segment of said remaining pair, and the coil array on one rotor face is angularly displaced relative to the coil array of the other rotor face by one-half of the angular pitch between two adjacent coils; and at least one pair of brushes contacting said commutator, the brushes of each pair being separated by an angle of substantially (n + 1/2) degrees, where n is an integer including zero.

13. A machine as claimed in any of claims 1, 2 or 12 wherein each of said stator members comprises a fero-magnetic backing plate, said array of magnetic poles being provided by a corresponding plurality of permanent magnets arranged in said array on said backing plate, each of said magnets occupying a pie-shaped area with a relatively small separation between it and adjacent magnets, each of said magnets being magnetized over its entire area in a direction - Page four of Claims - 15 perpendicular to said plate, adjacent magnets being magnetized in opposite directions, and each magnet of the first stator member being opposed to and magnetized in the same direction as a magnet of said second stator member, with a gap between said two opposed magnets, the coils of said rotor being movable circumferentially through said gaps.

14. An electro-mechanical machine comprising: first and second flat spaced parallel stator members, each having a circular array of 2N magnetic poles of alternately opposite polarity, where N is the number of pairs of such poles, each pole of one stator member being opposite and spaced from an opposite polarity pole of the other stator member, a disc armature rotor having a circular array of coils on each face thereof between the stator members, wherein the coils are formed by four groups of coils with each group arranged as an array of N series coils on a respective one-half of a face of the rotor, and commutator means rotatable with the rotor and being operatively connected to the four coil groups.

15. A machine as claimed in claim 14 wherein the 2N
coils are symmetrically arrayed on each face of the rotor and the coil array on one rotor face is angularly offset relative to the coil array of the other rotor face by one-half of the angular pitch between two adjacent coils.

16. A machine as claimed in claim 14 or 15 wherein the commutator means has N sequential sets of four sequential segments each, the N corresponding (i.e. first, second, third or fourth) segments of each set being interconnected.

- Page five of Claims - 16

17. A machine as claimed in claim 14 or 15, wherein each of the coils is a one-layer spiral with non-overlapping turns arranged flat on the rotor face.

18. A machine as claimed in claim 14 or 15, wherein the coils are made of square wire.

19. An electro-mechanical machine comprising: first and second stator members having substantially flat active surfaces in spaced, opposed relationship; a substantially circular array of magnetic poles of alternately opposite polarity mounted on the active surface of each stator member, each pole of one stator member being opposite and spaced from an opposite polarity pole of the other stator member a substantially flat armature rotor mounted intermediate said arrays of poles for rotation about an axis perpendicular to said active surfaces, said disc having a substantially circular array of coils on each face thereof with the coils on each face being arranged in a plurality of groups of coils on respective segments of the face and each group of coils being connected in a series circuit; and commutator means including terminals associated with the circuit formed by each group of coils and means rotatable with said rotor for connecting and disconnecting said terminals from a source of power in a predetermined sequence and with a predetermined, reversing polarity.

20. A machine as claimed in claim 19 wherein the coils are symmetrically arrayed on each face of said rotor and the coil array on one rotor face is angularly offset relative to - Page six of Claims -the coil array of the other rotor face by one-half of the angular spacing between two adjacent coils.

21. A machine as claimed in claim 19 or 20 wherein each face of said rotor includes 2N coils arranged in M
groups, said commutator means having N sequential sets of M sequential segments each, the N corresponding segments of each set being interconnected.

22. An electro-mechanical machine comprising: a stator means and a rotor means having generally flat faces in axially opposed relation, one of said stator means and rotor means having on a face thereof a circular array of 2N magnetic poles of alternately opposite polarity and the other of said stator means and rotor means having on a face thereof a circular array of coils in axial opposed relation to said poles and a switching device synchronized with said rotor means; and wherein said circular array of coils comprises a plurality of groups of coils with each group of coils being arranged on a respective segment of the face of said other of the stator means and rotor means and the coils of each group being in series with one another; and said switching device is operatively connected to said groups of coils.

23. An electro-mechanical machine as claimed in claim 22 wherein said switching device is a commutator having a plurality of segments operatively connected to the coil arrays; and further comprising at least one pair of brushes contacting said commutator, the brushes of each pair being separated by an angle of substantially (n + 1/2) degrees - Page seven of Claims -wherein n is an integer including zero.

24. A machine as in claim 23 wherein said stator means comprises first and second stator members in spaced relation, each pole of one stator member being opposite and spaced from an opposite-polarity pole of the other stator member;
said rotor means comprises a disc rotor between said stator members and having two generally flat faces, said commutator being rotatable together with said rotor; and wherein a respective array of coils is provided on each face of said disc rotor, said coil arrays being between said stator pole arrays.

25. A machine as in claim 24 wherein preselected ones of said commutator segments which are separated from one another by a predetermined number of said commutator segments are interconnected.

26. A machine as in claim 22 or 23 wherein said rotor means is a substantially planar member having two circular arrays of coils, the coils of each group have N coils and said switching device comprises commutator means rotatable with said rotor.

27. An electro-mechanical machine as in claim 22 or 23 wherein: said one of said stator means and rotor means has first and second spaced apart parallel faces, each having a circular array of 2N magnetic poles of alternately opposite polarity; each pole of one face being opposite and spaced from an opposite polarity pole of the other face; and said other of said stator means and said rotor means having a circular array of coils on each face thereof between said - Page eight of Claims - 19 spaced faces.

28. A machine as in claim 22 or 23, wherein said one of said stator means and said rotor means is the stator means and said other is a disc armature rotor, said switching device comprising commutator means rotatable with said rotor.

29. An electro-mechanical machine as in claim 22 or 23 wherein:
said one of said stator means and rotor means has first and second spaced apart parallel faces, each having a circular array of 2N magnetic poles of alternately opposite polarity;
each pole of one face being opposite and spaced from an opposite polarity pole of the other face;
said other of said stator means and said rotor means being flat and having a circular array of coils on each face thereof between said spaced faces wherein said coils define a plurality of conductive pathways, each of which is arranged to form a continuous array of coils on a respective portion of a face of said other of said stator means and said rotor means; and wherein said circular arrays of coils comprise pathways each forming a continuous array of N coils on a respective one half of a face of said other stator means and said rotor means.

30. An electro-mechanical machine comprising: a stator and a rotor having generally flat faces, a rotor face being mounted in spaced, opposed relationship to a stator face for rotation relative thereto; a substantially circular - Page nine of Claims -array means of magnetic poles of alternately opposite polarity mounted on one of said stator and rotor faces; a substantially circular array of coils mounted on the other of said stator and rotor faces wherein said circular array of coils comprises a plurality of groups of coils with each group of coils being arranged on a respective segment of the face of said other of the stator and rotor and the coils of each group being in series with one another; a pair of power terminals;
and switching means synchronized to the rotation of said rotor for connecting and disconnecting said groups of coils between said power fterminasl in a predetermined sequence and with a predetermined reversing polarity.

31. An electro-mechanical machine as in claim 30 wherein:
said stator and rotor having generally flat faces and being in opposed facing relation; and said other of said stator and said rotor having two substantially circular arrays of coils, each array being arranged to interact with said magnetic pole array.

32. An electro-mechanical machine as in claim 31 wherein:
said one of said stator and said rotor comprises two substantially parallel faces spaced apart to form a gap therebetween, each face having a circular array of magnetic poles of alternately opposite polarity and each magnetic pole of the circular array of one of said faces being aligned opposite an opposite polarity magnetic pole of the circular array of the other of said faces; and said other of said stator and said rotor is positioned between said two members.

- Page ten of Claims -

33. An electrom-mechanical machine comprising:
a stator having an array of 2N magnetic poles of alternately opposite polarity where N is the number of pairs of such poles;
a disc rotor facing said stator member;
two arrays of coils on said disc rotor, each said coil array facing said stator pole array;
a commutator rotatable together with said rotor and having 4N segments arranged in N sequential sets of four sequential segments each, the N corresponding segments of each set being interconnected;
one coil array being angularly displaced relative to the other coil array by a fraction of the angular pitch between two adjacent coils;
the coils of one-half of one coil array being connected together in series and to one pair of segments of said four sequential segments;
the coils of the other half of said one coil array being connected together in series and to the remaining pair of segments of said sequential segments;
the coils of one-half of the other coil array being connected together in series and to a segment of said one pair and a segment of said remaining pair; and the coils of the other half of said other coil array being connected together in series and to the other segment of said one pair and the other segment of said remaining pair.

- Page eleven of Claims -