Dec’. 1_0, 1946. J.R.MA¢1NTYRE 2,412,461 SYN CHRONOUS MOTOR Filed May 25, 1945 2 Sheets-Sheet 1 „mnVßmR?@.MA/„nMaß@ mbby à/Vef wm mÍA@ Dvec. 1_0, 1_946. J. R. MACINTYRE 2,412,461 SYNCHRONOUS MOTOR Filed May 25, 1945 2 Sheets-Sheet 2 lmventorz' John E. Macih \ ' - His es v Í` «w ß ttor‘rwey. 2,412,4ti Parental Dee. 1o, 194s UNITED STATE-s PATENT ' 2,412,463‘; ' SYNCHRONOUS l John R. Macintyre, South Peabody, signor to General ration of New York Application May 25, Serial No. 595323 1 2 My invention relates to synchronous motors netic core fl, andouter and inner stator magnetic and is suitable for use in the construction of small motors such as are used for timing de `pole piece sections oi such a motorin which there is high utilization of the material in the rotor and a high utilization of the radial space'occupied by adjacent stator and rotor parts for the production of torque. In the usual motor the torque producing pole piece parts of stator and rotor are located in concen tric circles separated by an air gap, and the rotor structure lying between its pole pieces and the axis of rotation is used merely as supporting structure. In accordance with my invention the ' and rotor are positioned in spaced parallel planes perpendicular to the axis of rotation and utilize and S, in the same radial i The outer pole piece section ~5 _ may be mechanically secured to the inner pole piece sec tion 6, by means of the nonmasnetic ring 3l, which is `welded to both pole piece sections. This welded assembly may be magnetically secured to andwithin cup l by a close iit at their contacting surfaces,'the outer periphery of section 5 having a bent-over rim section ‘lf to facilitate this. The welded assembly of the inner stator pole piece section 6 and outer pole piece section 5 is staked to the inner end of core 4, and the opposite 'end of the core is staked to the center of the end loi plane. _ vices. One object of the invention is the design active torque producing ‘pole pieces of both'stator as @emp-any, a corpo cup l. A coil 8 surrounds the core I and is housed within the magnetic parts described as shown. A dish-shaped spring washer 9 holds the coil a very substantial portion of the entire radial ñrmly in place so that it cannot rattle. Provi space between the axis of rotation and the pe sion is made for exciting coil 8 from an alternat riphery of the rotor. By such an arrangement 20 ing current circuit Èby leads l0 brought out the available torque producing surfaces of stator through a bushing Il in the end wall of member and rotor for a motor of given external dimen i. The electrical resistance of the washer 9 and sions may `be appreciably increased with a corres the metal ring 3d are such as to limit the power spending increase in the ratio of motor output loss due to circulatingy currents to a minimum. to motor size. Other advantageous features of 25 If necessary 'this can be accomplished by suitable my invention will be mentioned as the description slotting to increase the length and hence the re proceeds. sistance of the circulating current path. The features of the invention` which are be-> The pole piece sections 5 and 6 have inter lieved to be novel and patentable will be pointed leaved ilngers or pole pieces l2 and i3, respec~ out in the claims appended hereto. For a better 30 tively. In the example shown there are eight understanding of my invention, reference is made pole pieces in each section, the pole pieces i 3 of in the following description to the accompany the inner section S extending radially outward ing drawings in which Fig.,1 shows a- cross-sec between inwardly extending radial pole pieces l2 tional view of my improved motor as constructed in the outer section 5 in the same plane. The with a suitable gear reduction and supporting 35 air gaps H between the pole pieces l2 and I3 are casing. Fig. 2 represents an end view of such a radially ‘symmetrical and are somewhat greater motor with a one-way clutch included in the gear near the periphery than* near the center. The teeth or pole »pieces i3 are slightly wider at their 3reduction represents unit anrepresented exploded perspective in dotted view lines.of the outer than at their inner ends and the teeth rotor and stator pole piece assemblies of the motor 40 l2 areends approximately twice as wide at the outer of Fig. 1, Fig. 4 is a perspective view of a shaded ends as at their inner ends. The radial gap at pole form of stator- pole piece assembly that may the ends of the 'teeth are made at least as large 'be used and 5 is a schematic illustration of as the greatest width or” the peripheral gap. The gaps between the stator pole pieces are sufficient rotor in a given torque position. 45 to prevent any appreciable leakage flux directly I will refer ilrst to the form of motor repre between these pole pieces in the operation ci the sented -in Figs. l to 3 wherein like parts are in= the overlapping tooth relationship of stator and dicated by like reference characters. The casing may comprise a magnetic cup part i with an end motor, and the generally sector shaped pole pieces and gaps are otherwise dimensloned with a view of avoiding saturation at any point and of ob closure 2, these parts being riveted together at 50 taininga maximum useful tordus nur. their rims by hollow rivets 3 which may then serve as screw or bolt holes for securing the motor assembly to' other apparatus. The motor stator magnetic circuit includes the right portion of the cup member l as shown in Fig. 1, a central mag The rotor l5 shown at the left in Fig. 3 is es sentially a disk withl eight radial slots I6 forming eight radial pole piece sectors l?. A’l’he rotor is rotatively mounted with a bushing i8 and a shaft 55 I9 on-the center axis of the casing and motor i 2,412,461 3 4 _ stator land is positioned closely adjacent to the Where a certain direction of rotation -is desired, plane of thestator pole pieces with a suflîciently small intervening axial air gap to cause the greater part of the flux which passes between sisting of a ratchet wheel 22 on one of theV driven a one-way lock may be provided in the gear re-- duction unit as represented in Figs. 1 and 2, con shafts and a ratchet pawl 23 cooperating there y the stator pole pieces to do so through the rotor. with to prevent rotation in the counterclockwise ' A thrust be'aring for the rotor shaft at the core end comprises `a steel ball 20 ilxed in the center of housing I8 against the end of shaft I9 and bears against a suitable bearing surface 2| in serted in the adjacent end of the core piece. This bearing surface ZI may be a small piece of fab direction as viewed in Fig. 2. The pawl is piv oted at 24 and has a tail 25 which approaches the ratchet Wheel 22 when the pawl 23 moves away therefrom, and in case the pawl is not in locking position when locking action is called for, ricated plastic material such as is sold‘under the trade-mark Textolite. The shaft I@ is other wise supported for rotation in bearings in plates the tail 25 will be, or will move the pawl to lock ing position. This locking device perse is not my invention, and any suitable one-way locking 2l’ which are riveted together in spaced relation and support the gear reduction unit for the motor securely in the left end of the housing as viewed in Fig. 1. The rotor sectors i1 may be bent -slightly as represented so as to bring their radial mechanism may be used which will serve the pur pose. Thus the motor is self-starting and runs in a given direction at a 16-pole speed. Gener ally, the gear reduction wili be such as to reduce the speed to one rpm at the terminal or out edges slightly closer to the stator pole pieces than 20 put shaft 25. It will be apparent that due to endwise mag the intermediate portions of the sectors. This netic attraction between stator and rotor, there assures a small motor air gap with sufficient clearance at the axis to accommodate the thrust bearing 2li and also makes the rotor more> diñi cult> to demagnetize. To facilitate the manufacture fof the rotor sec tors I1 and their proper alignment with the stator pole pieces, the inner ends of the slots I6 may terminate in enlarged drill holes 36. In the formY will be an end thrust on the ball bearing âêl-‘â l. This bearing determines the air gap between sta 25 tor and rotor and will be designed for minimum wear and long life. The bearing plates 2l', which rotatively support the motor rotor shaft I9 and ` all of the shafts of the gear reduction unit, are preferably made of an oil impregnated metal, such as is sold under the trade name “oilite” of synchronous motor represented in Figs. 1 to 3 The motor and gear reduction unit requires no the rotor is preferably made of permanent mag additional lubrication, and the motor unit is in net material, such as the copper-nickel-cobalt tended to run continuously for several years with alloy described in United States Letters Patent out attention. The motor has been found to be No. 2,170,047 to Dannöhl et al., and is polarized in a peripheral direction to have poles of opposite 35 exceptionally quiet in operation with relatively polarity facing themselves across the radial slots smooth torque pulsations. This is attributed to the combination of low speed, high torque rotor I6 at the edges of the sectors as indicated by the inertia, and the range of overlapping ci the rotor polarity marks on certain of the rotor .sectors in and stator poles during synchronous torque pnl Fig. l3. 'I'he radial length of the sectors I1 con -forms to the radial length of active stator pole 40 sations. It will be observed that the useful torque producing pole face length in the rotor is the pieces, and the rotor is of the proper diameter radial length of a rotor sector I1 measured from so that when assembled the rotor sectors I1 can the opening 36 to the periphery multiplied by magnetically bridge across the gaps I4 of the stator when in overlapping position. sixteen, and is roughly double that which would It will now be evident that when the stator coil 45 be practicable in a conventional motor of the 8 is energized with alternating current, the sta same diameter where the useful ñux gap is across tor pole pieces I2 and I3 will alternate in mag-A a radial gap at the periphery of the rotor and netic polarity, the poles I2 being south poles when where the greater portion of the nonperipheral poles I3 are north poles and vice versa, creating portion of the rotor is used only as a spider sup a magnetic ñeld which pulsates at a rate propor porting structure.~ In the stator the useful pole tional to the applied frequency. -Thus if the fre face area is even greater in proportion since it is quency be 60 cycles, the synchronous speed of the v the total stator pole face area adjacent the rotor 16 pole rotor operating in cooperation _with the section. Thus the sector-shaped pole pieces of 16 pole iield will be 450 rpm. The polarized rotor, the stator have a radial length more thanvthree although having eight sectors, is` in reality a 16 55 times their mean peripheral width with a cor pole rotor, as the sectors have a pole at each of responding'ly large useful pole face surface. their two edges. At standstill with the ñeld de The structure or material used in the gear case energized, the rotor will, if sumciently free, seek Y to the left of the rotordn Fig. 1 should be such a position whereAits sectors I1 bridge gaps be as not" to provide any appreciable magnetic leak tween the stator pole pieces because the sectors 60 -age ñux path from the cup shell into the hub l of the rotor being permanent magnets will move. ysection of the rotor such as would rob the 'motor to a position of least reluctance. When the field is energized, it would appear that the rotor might lock, as theoretically the opposing torques of re pulsion and attraction can be equal in certain 65 rotor positions. However, such is not the case because of the unbalanced magnetic and me chanical conditions which will always exist. The . rotor will vibrate momentarily moving` ?rst` in one direction and then in the other because of 70 its low inertia and the high magnetic forces active upon it. Therefore, it will jump into syn chronous speed almost instantaneously, although of useful ñux. _ Where a shaded pole type of motor is desired, the stator pole piece structure may be formed as in Fig. 4. The stator pole pieces designated I2a and I3a in Fig. 4 correspond to the pole pieces I2 _and I3 of Fig. 3 but are provided with axially , extending pole faces 21, 28, 29,7and 30 formed by turning the edges sol as to extend toward the rotor. A copper disk 3l having slots 33 extend ing to the periphery to accommodate the pole place _extensions 21 and 29, and openings 32 to ‘ accommodate pole face extensions 28' and 3D, is -provided. The flux which threads the latter or the direction of rotation is uncertain unless the rotor is permitted to go in one direction only. 75 trailing pole face extensions is thus shaded or , 2,412,461 retarded by the copper conductor surrounding ' all of the torques for this rotorposition and pro such extensions. but that which threads the leading pole face extensions 21 and 29 is not duce» starting and synchronous operation in a counterclockwise direction. There are of course a great variety of rotor positions and stator pole shaded. In order to equalize the flux in the un shaded and shaded portions of the stator poles, polarity conditions that could be similarly repre the shaded »pole face extensions 23 and IU are made slightly longer than the extensions 21 and 29 in an axial direction; hence, the air gap be tween theshaded pole face extensions and rotor sented but it is believed that the example given will be suiiicient to an understanding of the op eration of this form oi motor, , The operation of the shaded pole hysteresis is made correspondingly less than for the un 10 form of motor of Fig. 4 is essentially the same as shaded extensions. vThe shaded pole construction in any shaded pole hysteresis motor except for >may use a hysteresis> steel disk rotor without , polar slotting as represented at 34a, Fig. 4. The the greatly increased amount of active stator pole piece and rotor area available for torque pro shaded pole form of'motor will not require the ducing action afforded by the novel construction. one-'way locking device 22-23 of Fig. 2, since 15 In accordance with the provisions of the pat it will rotate only in the direction-of the rotating ent statutes I have described the principle of op field produced by the shading poles. ' eration of my invention, together with the ap Fig. 5 is intended to show the manner in which paratus which I now consider to represent the the rotor and stator pole pieces overlap and to best embodiment thereof, :but I desire to have it illustrate theftorque action of the form of motor 20 understood that the apparatus shown is only il of Fig. 3. `In Fig. 5 the stator pole pieces I2 and lustrative and that the invention may be car I3 are shown in full lines and the rotor sectors I1 are represented in dot-dash lines for one par ried out by other means. l What I_ claim as new and desire to secure'by Letters Patent of the United States, is: ticular rotary position taken at random. It is seen here that the peripheral width of a rotor 25 1. An _electric motor structure comprising co sector I'I is roughly twice the width of the stator operating stator and rotor members the stator pole pieces and the same width as the spacing member having a magnetic circuit provided with _ between stator pole pieces of the same polarity an air vgap formed between two equally numbered at any given radius. Thus the distances DI 2, DI 3 sets of pole pieces, one set extending radially in representing the spacing between stator poles I2 30 ward and the other set extending radially out and between stator poles I3, respectively, are ward in the same plane perpendicular to the axis roughly equal to the width DI1 of the rotor sec- ' _ of rotation of the motor with the pole pieces tors II‘I all measured at the same radius. Also the spacing between rotor sectors I1 is roughly the width of the stator pole pieces measured at the same radius» `lïiachrotor sector Il is thus within the influence of at least two stator poles and possibly three stator poles rin all- rotor po sitions and is always within the influence of stator poles of opposite magnetic polarity, and each rotor magnetic pole is always within the inñuence of at least one stator magnetic pole. This lib eral range of overlapping is advantageous in quick and powerful .starting from any rotor position and in smoothing out the torque pulsations at syn-> chronous speed, resulting in quiet operation.A In Fig. 5 the outer group of stator poles _I2 is represented as having an N polarity and the in of one set interleaved between the pole pieces oi' the other set, said pole pieces lbeing sector shaped and of a radial length at least three times their mean peripheral width, a single-phase al-> ternating-current coll for producing a flux in the magnetic circuit such that when the pole pieces of one set .are at one polarity the pole pieces of 40 the other set are of the opposite polarity, said ner group of stator poles as having an S polarity at the instant assumed. The permanent mag netic polarity of Athe _rotor is represented by small jn and s polarity designations along the edges îfythesectors Il, From the knowledge that like po es repel and unlike poles attract, the torque relations between stator ,and rotor for this posi- ' tion of the rotor and stator pole polarity will be evident. An outer circle of arrows pointing clock wise represents attraction forces drawn between pole pieces .being uniformly spaced and symmet _ rically distributed about the axis of rotation, the rotor including a magnetic member mounted for rotation in a radial plane closely adjacent to the radial plane occupied by said pole pieces, the effective air gap between said rotor member and said pole pieces being less than the eiIectiVe air gap between the pole pieces whereby flux passing between the adjacent stator pole pieces of opposite magnetic polarity, does so primarily through said rotor member, _, 2. :An electric motor structure comprising co operating stator'and rotor members said stator member having two sets of magnetic pole pieces equal in number, one set extending radially out ward from the axis o! rotation of the motor and the other set extending radially inward in the same plane such that the pole pieces of one set extend between the pole pieces of the other set in stator and rotor. An inner circle of arrows ,60 with substantial air gap space between them in> the edges oi the adjacent poles of unlike polarity also pointing clockwise represents repulsion torque forces at the points where they occur, 'I'he length said plane, said pole pieces being equally 'spaced and symmetrically distributed about the axis of motor rotation, mans for producing an alternat ing magnetomotive force between said two sets of pole pieces,- said rotor member including a radially slotted disk rotatively mounted closely adjacent to and in axially spaced relation with respect to the stator pole pieces, .the rotor slots dividing the rotor into equal sectors equal in of these arrows does not necessarily represent rel ative values but rather the angular location of the torque forces. Thus the arrow marked “At- ’ traction” represents the attraction of south stator pole I3 for the northA pole- of adjacent rotor sec tor I1 to the left thereof, and the arrow marked “Repulsion” represents the repulsion force be tween north stator pole I2` and the north pole 70 number to the stator pole pieces of one set and oi.' sector I1 adjacent thereto. These forces exist of approximately half the peripheral width of the over the radial length of the pole pieces and will stator pole pieces measured at the same radius, obviously tend to produce clockwise rotation as said rotor disk being made of permanent mag-z . viewed in Fig. 5. If the rotor is blocked for clock net material with its sectors similarly polarized wise rotation, the next half-cycle will reverse 75 in a peripheral- direction such that permanent aeiaeer 7 . tor-shaped stator pole pieces, both sets ex magnet poles of opposite polarity are formed at the two end edges of each sector, the eiîective air gap between the stator and rotor pole pieces tending in a radial direction relative to the axis of rotation of the motor and in the ' same plane perpendicular to such axis of - being less than the effective air gap between the stator pole pieces of opposite polarity. rotation with the pole pieces of one set spaced -from and alternately interleaved with the pole pieces of the other set over a radial distance ap 3. An alternating-current motor structure com prising cooperating stator and rotor members, said vstator member having a magnetic circuit preciably greater than the maximum peripheral pole-piece width, said pole pieces being equally formed of a cup-shaped member with a central core part therein on the axis of rotation of the 10 spaced and symmetrically disposed about the axis motor and with a set oi sector-shaped pole pieces of rotation of the motor, means for producing an alternating ñux between the pole pieces of the ' extending radially inward from the rim of the dirîerent sets, and a magnetic rotor ,mounted for rotation in a plane parallel to and closely ad cup toward the core and a set of an equal num-u ber of sector-shaped pole pieces extendingradi ally outward from the core toward the rim" ofthe 15 jacent the plane of- said pole pieces such' that it magnetically overlaps stator pole pieces of both cup at the outer end oi the core, said pole pieces sets and comprises the principal path. for the having a radial length more than twice their alternating iiux between said sets of pole pieces , mean peripheral width and being symmetrically and whereby thearea oi' said stator pole pieces' spaced and interleaved in the same radial plane with sector-shaped gaps between their radial 20 facing and overlapped by said rotor is available for producing torque ñuxes. edges, an energizing coil within the cup and about 6. A shaded pole alterriating-current- motor the core for producing a single-phase alternat having cooperating stator and rotor members the ing flux between said pole pieces, said rotor mem stator having a magnetic circuit with two equal Vber including a disk-shaped rotor of magnetic material mounted for rotation on the axis of said 25 ly numbered sets of pole pieces in the same plane perpendicular to' the axis of motor rotation the core in a plane parallel to the plane of the stator poles of one set extending lradially inward loe pole pieces and closely adjacent to and opposite said pole pieces such that the eiîective air gap be tween the poles of the other set which extend ra dially outward symmetrically with respect to such tween stator pole pieces and rotor is less than axis, means for producing' .la single-phase alter ' that between stator pole pieces of opposite mag nating ñux >between the diñerent sets of pole l netic polarity whereby the greater portion of the pieces, a magneticrotor mounted for rotation' on stator iiux passing between the pole pieces does such axis and positioned in a plane parallel to so 'through the rotor and a thrust bearing for and closely adjacent the »plane of the stator pole said rotor determining the axial air gap spacing between stator and rotor. ~ 35 pieces whereby the rotor overlaps and magneti cally bridges the stator pole pieces, the pole pieces d. A synchronous alternating-current motor of said stator having their radial edges extended comprising cooperating stator and rotor mem toward the rotor, shading pole conductor means bers, said stator member having a magnetic cir surrounding said radial edges oi all of said pole pieces only on the trailing sides oi said pole cuitformed oi a cup-shaped member with a cen tral core therein and with radially extending pole ,pieces between the core and the cup, there being a set or” pole pieces magnetically connected to the core extending toward the wall or" the cup, said two groups of pole pieces being equally and pieces, the eiîective air gap between stator pole pieces and rotor being less than betweenv stator pole pieces of the diñerent sets whereby ñux pms ing between said sets of pole pieces does so 'through the rotor, and portions thereof from each pole piece are lagged by said conductor means symmetrically spaced about the axis of the core , causing a rotational shifting of such ilux and cor the cup extending toward the core and an egual number oi pole pieces magnetically connected to responding rotation of the rotor. with outwardly extending pole pieces between the 7. A shaded, pole alternating-current motor' inwardly extending pole pieces in the saine radial piane, said pole pieces being sector-shaped and 50 having cooperating stator and rotor members, the oi such dimensions as to provide~ a high reluc tance air gap between the two sets, an energiz ing coil within the cup and about the core for producing an alternating iiux potential between the sets oi pole pieces, a rotor in the I’onn of a disk having radial slots dividing the dislzinto sectors equal in number to one set of stator pole pieces, said rotor being mounted for stator' having a magnetic circuit formed with a cup-shaped outer part, a core part extending con centrically within the cup from the base there of and a pole piece assembly between the outer end of the core and inner walloi the cup, a coil within the cup and about the core ior producing an alternating linx through the magnetic circuit and pole piece assembly, said pole piece assembly allel to that of the statorpole 'pieces and closely including a plurality of evenly spaced magnetic pole pieces extending inwardly from the cup to adjacent thereto so that its sectors simultane . ward the core and an equal number of evenly -rotation on the axis of the core in a plane par ously overlap stator pole pieces in the two sets, spaced magnetic Ipole pieces extending outward said rotor being made of permanent magnet ma terial with its sectors similarly polarized in a ly from the core symmetrically between the in wardly extending core pieces and in the same plane, a vrotor containing magnetic material ro tatively mounted on the axis of the cup in a plane peripheral direction to form poles of opposite . magnetic polarity atopposite ends of each sector, said sectors having their end edges symmetrically ‘bent toward the stator pole pieces, and a thrust bearing for said rotor spacing the rotor from the stator pole pieces by an eiïective'air gap less than the'air sap between stator pole pieces of the _ '_ diii’erent sets whereby the ñux path between dif ferent sets of stator pole pieces is through the rotor. . ' _ 5.'.iin electric motor having two sets of l parallel and closely adjacent to the plane oi said pole pieces, the leading and trailing edges of said pole pieces having projections facing the rotor with the projections on the trailing edges being longer and extending nearer the rotor than the A others, and shading coil means on the longer pro ` jections, the air gap relations between stator pole pieces and between stator pole piece projections 75 and rotor being such that the greater portion oi 2,412,461 Athe flux between thetpoie pieces passes through on the opposite side oi' the ilux air gap from the the rotor and is approximately evenly divided `.between the longer and shorter pole piece ex tensions. 8. A single-phase alternating-current motor structure comprising cooperating stator and ro tor members separated by a iiux air gap lying in a plane perpendicular to the axis ot motor rota Astator pole pieces having magnetic material ad »jacent and magnetically bridging the stator pole pieces of opposite magnetic' polarity causing the tion, said stator meínber having a group of even ' net Mmaterial and slotted radially so as to divide flux between said two groups of pole pieces to cross said air gap and pass through the rotor. 9. A circular motor rotor member for a syn chronous motor composed of permanent mag ly spaced pole pieces of one magnetic polarity 10 -the peripheral portion thereof into a plurality of equal sectors, said rotor being permanently facing the air gap in circular formation about the axis of rotation, and a second group, equal in magnetized in a peripheral direction so as to pro numberto the ñrst group, of evenly spaced pole pieces of the opposite magnetic polarity facing duce a permanent magnet pole of one polarity at the leading edge of each sector and a. permanent the’aix gap in circular formation about the axisl 15 magnetic .pole of the opposite polarity at the trail of rotation and lying between and in the same ing edge of each of said sectors whereby the rotor radial plane with the ñrst group of pole pieces, has twice as many magnetic poles as there are said pole pieces being sector-shaped and being sectors, which poles alternate in polarity about interleaved a radial distance greater than twice the rotor. ' the mean peripheral pole piece width, a rotor mounted for rotation about the axis of rotation 20' JOHN R. MACINTYRE.