US1567657A - Short-circuiting device for commutators - Google Patents

Description

i /0 '5W f /3 fo" Dec. .-29 1925. 1,567,657

E. P. LARsH SHORT CIRCUITING DEVICE FOR- COMMUTATORS Filed De. e. 1921 Patented Dec. 29, 1925.

UNITED STATES EVERETT P. LAR/SH, OF DAYTON', OHIO.

SHORT-CIRCUIFTING DEVICE FOR COMMUTATORS.

Application lcd December 6, 1921. Serial' No. 520,342.

State of Ohio, have invented certain newl and useful Improvements inv Short-Circuiting Devices for Commutators, of which the following is a specification.

This invention relates to electric motors and more particularly to a short circuiting or operation changing device for alternating current motors of the repulsion-induction type, -by which the motor is automatically changed from a repulsion starting condition to an induction running condition and viceversa,4 in accordance with variations of speed.

'lhe'object of the invention is to simplify the structure as well as the means and inode of operation of such circuit changing devices whereby they will not only be cheapenedv in construction, but will be more efficient in use, automatic in operation, uniform in action, automatically controlled, and unlikely to get out of repair.

A further object of the invention is tov provide improved means operated by centrifugal tendency by which the commutator bars are automatically connected with a common electrical conductor which will promptly respond to variations of speed above and below a predetermined rate of rop tation.

A further object of the invention is to provide a short circui-ting or current changing device, which will have va shifting movement insuring perfect electrical Contact, in which this shifting action will be further effected under yielding pressure thereby obviating any chatter or vibration and the incident arcing and burning of the contact surfaces.

A further object of the invention is to provide means for controlling the movement of the short circuiting o r current changing members whereby their movement to effect the alternation of the motor from repulsion to induction operation and vice-` versa\.will be effected by a quick movement 1in either direction.

"A further object of the invention is to provide such a .short circuiting or current changing device which will be compact, of-

few parts, and having no pivot joints, nor

. indirect movement, but in which the current controlling devices are directly operated by 'centrifugal tendency.

lVitli the above primary and other incidental objects in view as will more fully appear in the specification, the invention consists of thev features of construction, the parts and combinations thereof, and the mode of operation, or thein equivalents, as hereinafter described and set forth in the claims.

Referring to the drawings, Fig. l is a longitudinal sectional view of an'electric motor towhich thepresent invention has been applied. Fig. 2 is a detail View showing the particular construction of the circuit closer illustrated in Fig. 1 in its operated or short circuiting position. Figs. 3 and 4 illustrate a modification of the short circuiting device .shown in Figs. l and 2, anfi'illustrate the inoperated and operated positions of the short circuiting element, adapted to make a butt contact with the commutator bar. Figs. 5 and 6 illustrate the inoperative and operative positions of a further modificationof the. construction shown in Figs. 3 and 4. Figs. 7 and 8 illustrate a further modification of thecontrolling means for which pertains wholly to the short circuiting Y means forthe'commutatorbars, by which the motor 1s caused to operate alternately as a yrepulsion motor and an induction motor.`

An alternating current, repulsion-induction motor of the single phase type to which the present invention is particularly adapted is one which as the name indicates, starts as a repulsion motor and as the speed approaches its normal or maximum rate of rotation automatically changes its character, and runsas an induction motor. Briefly described it \consists of a eld or stator of laminated toothed construction having a single winding thereon connected to the sup ply circuit and a progressively wound armature or rotor with a commutator engaged by ftrol, or distance operation.

ings and operates as a repulsion motor until' the rotor or armature-approachcs'a synchronous speed 'or one commensurate with the windings, whereupon the speed controlled devices operate to automatically short circuit tlie armature winding thru the commutator. Thus the motor-is automatically transformed from a repulsion type into an induction motor having what is essentially a squirrel cage rotor. It is the improvement of the speed operated governing or short cir-v cuiting device which forms the subject matter of the present invention. One of the advantages of a machine of this type is that it is inherently a constant speed motor having a high starting torque with low current consumption or minimum current surge.

The straight repulsion motor Without compensation gives the most eicient starting torque possible while the'l single phase induction rotor with the squirrel cage armature or its equivalent affords the most eHicient motor when running.

A repulsion-induction type of motor combines these most desirable qualities in a single machine. As it possesses such high starting torque characteristics it is well adapted for operating machinery which starts under full load, as pumps, air cornpressors, and grinding mills. Requiring no starter they-.are adapted for automatic con- They start quickly and operate quietly and smoothly.

The above is offered merely to facilitate a thorough understanding of the purpose of vthe invention, and with no intent nor desire that it shall in any way be construed as limiting or restricting the application or scope of the invention..

Referring to the drawings, 1 is the motor frame or housing, in which is located the annular stator 2 Within which rotates the rotor 3, carried upon the shaft 4, mounted in suitable bearings 1a in the opposite ends of the frame or housing. As shown in the drawings, the statorI is of laminated form, while\the rotor comprises the usual laminated core carrying a series of windings or coils (not shown in the drawing), the sev-- eral coils being connected to corresponding commutator bars 5. The commutator comprises a plurality ot' the bars 5 suitably mounted upon and insulated from a head 6, and insulated or electrically isolated one from the other. The commutator comprising the head 6 and electrically separated commutator bars carried thereby is mounted upon the shaft 4 and rotates therewith together with the rotor 3. That is to say, the rotor, the shaft and the commutator form a single rotating element, as is ordinary in electric motors. Carried by a suitable annular collar or supporting ring T mounted in one of the end trames, are two brush holders 8 only one ot which is shown, in the drawings,'which carry brushes 9, interconnected one with the other and bearing upon the periphery ot' the commutator. which the present invention is applied.

The short circuiting device forming the subject matter hereot' comprises a conductor collar 10, slidingly mounted upon the shaft 4 adjacent to the commutator. This conductor disc 10 is of concave or dished formation, having at its center and surrounding the shaft 4 an inwardly flanged boss 11. This central boss 1 1 is of such extent that it engages the insulating head 6 of the coinmutator and forms a stop to limitA the approach of the outer edge of the disc l() toward the terminal faces of the commutator bars 5. The conductor disc 10 is pressed inwardly or toward the 'commutator by a helical spring 12 interposed between the inturned flange ot' the central boss 11 of said disc and a stop collar 13 fixed upon the rotor shaft 4.. As shown in Figs. 4 and 5, this collar 13 may form a support or bearing for the disc 10 upon which the disc slides to and from the commutator. The inturnezl flange of the central boss of this disc may also have a sliding bearing upon the shaft 4. These bearings may be quite loose, and there will be but little friction .or wear at these bearing points.

The intermediate or web portion of the disc 10 is inclined or concave to form a cani surface against which the centrifugally controlled conductor slugs operate in their outward movement to afford a wedging action, which eventually shifts the conductor disc outward against the tension of the retracting spring 12. The ends of the connuutator bar project beyond the lateral face of the head 6,] and are beveled or inclined on their inner side, as at 14 in a direction oppositely disposed relative to the inclination of the conductor collar 10. The overhanging ends of the `contact bar 5 afford contact surfaces for the centrifugally controlled conductor.

Such is the usual form of motor to' slugs with 'which said slugs make both butt V is a series of radially disposed conductor slugs l of a substantially trapezoidal form. 'lhe number of these slugs greatly exceeds that of the commutator bars, there being preferably an average of one and a half to two conductor slugs 15 for each commutator bar. The slugs 15 have each aslotted opening .16 therein thruv which extends an elastic retainer shown in Fig. 9 as two close coils of an evolute spring 17. The slugs 15 are strung upon the elastic retainer 17 closely together in a bead like fashion, whereby upon contraction of the elastic retainer 17, they are drawn into close association one with the other. The series of slugs assembled upon the retaining ring 17 are located within the disc '10 intermediate the disc and the insulating head 6 of the commutator against which the perpendicular inner faces of the slugs are pressed by the retraction of the disc 10 under the influence of the spring 12. The conductor slugs are oppositely beveled or substantially V-shaped' adjacent to theiry outer edges to agree with the oppositely disposed inclinedfaces of the disc 10, and conunutator bars 5. The slugs 15 must have a wedging action between the non-yielding inclined surface 14-on the commutator bar, and the inclined face of the conductor disc 10. It is to be noted by reference to Fig. 1, that the inclination 14 of the conductor bar 5 is located at a somewhat greater distance from the shaft 4 than the inclination of the conductor disc 10. Thus during the initial movement of the slugs 15, the inclined face thereof Vacts only on the disc 10, to force the disc outward against the tension of its spring 12. There is somewhat less resistance to the initial movement of the slugs 15 than'is met with uponengagement of the slu s with the inclined contact face 14. As t e slug 15 engages the contact face 14 of the commutav tor bar, it is directed slightly outward or laterally in unison with its lradial'movement under the influence of the camming' action of the'face 14, and against the tension of the spring 12. Its outward movement, however, is retarded by the inclined face14 with' which it makes a wiping contactin laddition to its butt engagement therewith, the necessary pressure of the contacting surfaces of the slugs and commutator bars beinginsured by the resistance of the conductor disc 10, and its spring 12. p

It will be understood that the rings 17 -while possessing sufficient tension to retract the slugs 15 when the rotor is at rest or Y operated at a'sub-normal speed, this tension is not suiicient to materially resist the outward movement of the slugs under the inuence of centrifugal tendency..

While the elastic ring 17 may comprise a simple wire coil or a flexible cable, as

shown and described in my prior and copending application Serial No. 363,402, filed March 5, 1920, of which invention the present construction is a continuation in part, thel ring 17 is preferably a flat strap spring as shown in the drawing. In order to insure more uniform operation of the slugs upon such ring, the ends of the ring arc preferably though not necessarily reduced to feather edges, in order that they may afford no obstruction to the sliding mov-ement of the slugs thereover. The flat strap yspring is formed into a convolute coil, the yconvolutions of which closely Contact one upon the other. To insure a close adherence of the ends of such coil, in order that they may not form obstructions orcngagc the slug, thetlat spring is initially coiled in one direction, and then before being used, it is recoiled in the same direction, but with the inner and outer ends transposed, whereby the original inner convolution, becomes the outermost, and the outer convolution ce-- comes the inner course of the completed ring. Thus. the tension or resiliency of the spring material is utilized to cause the ends of the coiled spring to conform closely to the succeeding convolutions thereof. That is to say, the inner convolution has an expansive tendency, while the outer convolution or end of the4 spring tends to contract in the completed retaining ring.

sie

So long as the motor operates atea low rate of speed, the centrifugal tendency is not sufficient to overcome the inertia of the slugs. However, as the speed increases, the slugs 15 tend to move outward, expanding the retaining rings 17, and exerting a camming pressure of the inclined faces 18 upon the inclined or concave web or face of the disc 10. rllhis camming action or wedging effect tends to increase the pressure of the contact of the slugs 15 upon the face of the commutator. As the speed and with it the centrifugal tendency increases, this cumming pressure upon the disc 10 exerts suicient force to move the disc 10 outwardly against the tension of its retracting spring 12, thus v'Ihese slugs 15 thus electrically bridge the individual commutator bars 5 with the common conductor disc 10.- It will be understood that the retaining ring 17 is not necessarily a part of the short circuiting shunt. In fact, so far as the essential operation of the device is concerned, the retaining member 17 may be of non-conductive material. The circuit is completed from each commutator bar thru a slug 15 to the common conductor disc 10, thence to another commutator bar, so that all the commutator bars are intei-connected `one with the other thru the disc 10 and intervening slugs 15. This bridging of the individual commutator bars 5, and the conductor disc 1() common to all the bars interconnects the armature windings one with another and the armature now becomes 1n efi'ect, a squirrel cage rotor.

Some constructors have thought 1t necessary or at least advisable to lift the brushes from contact with the commutator to prevent wear. l-However, the wear of the brush and commutator is so slight as to be negligible. The destruction of brushes heretofore attributed to wear has in fact been `due to burning of the brush, thru arcing between the brush and commut'ator. The constant arcing or sparking of the brush upon -the commutator burns the surface of the brush away rather than wears it away. Inasn'iuch as when the commutator bars are electrically interco-nnected one with the other thru the disc 10 or short circuited, no arcing can occur between the brushes and thecommutator, it has not been found necessary to lift the 'brushes or to separate them from the commutator bars.

As the speed of the rotor decreases and the centrifugal tendency becomes less effective, the conductor slugs 15 are retracted thru the combined tendency of the helical A elastic retainer 17 and the pressure of the head 6,

inclined web or face ofthe disc 10, under the influence of the lretracting spring 12. This retract-ing tendency causes the slugs 15 to move inward passing in such movement from the conductor bars 5 to the insulating tween the commutator bars and the disc 10. This returns the rotor to the influence of the brushes 9 and the windings or coils conmay be employed.

nected with the separated commutator bars 5, whereby the motor again operates under repulsion infiuence.

While the elastic or expansible retainer 17 formed as shown, of two helical coils is desirable, other forms of flexible connection However, the retainer may be omitted, and the slugs assembled side by side intermediate the disc 10 and commutator entirely independent of .each other. The slugsare suficient in number andsufiiciently closely associated that they cannot become materially disarranged, and the camming pressure of the disc 10 under the infiuence of the retracting spring 12 may be utilized toreturn the slugs' to their normal or central positions.

The construction as heretofore described isca able of various modifications, several of which have been illustrated in Figs. 3 to 8 inclusive. In Figs. 3 and 4 there is shown a modification in which in lieu of the in-l clined face 14,v the commutator bars 5 are extended at right angles to the face ofthe head 6 to form anfoverhanging annular fiange upon the commutator upon the inner faceof which the slugs abut, vwhen moved thereby breaking the contact beto their outermost position. In this construction, the form and operation of the conductor disc 10 and spring 12 are the same as heretofore described, and the construction differs from that of Figs. 1 and 2 in that the contact of the slugs with the commutator bar is a flat abutting engagement and not a wiping or wedging contact as previously described.

ln Figs. 5 and 6 there is shown a further modification differing from those previously described in that the head 6 is formed with an over-hanging inclined cam face 20, en gaged by a correspondingly beveled face upon the slugs 15, whereas the common conductor disc 10a forms without its inclination or concavity as before described. In this form of device the contact bars 5 overhang the slugs in the same manner as in Figs. 3 and 4. However, the slugsride radially in a comparatively straight line upon the disc 10, in the same manner that they ride upon the head 6 in the construction heretofore described. yields against its tension spring under the infiuence of the engagement of the slugs 15 with the inclined face 20, thus resisting to some extent theoutward movement of the slugs under centrifugal tendency. At the limit of the outward movement, the slugs abut upon the overhanging ends of the contact bars 5.

In Figs. 7 and 8 there is shown a further modification in which there is employed a stationary disc or collar 21 and a yielding collar or disc 10b which corresponds to the common-conductor discs 10 and 10a of the previous constructions. The slugs 15 are located between the discs 21 and 10b. The disc 10b is formed with a concave or inclined web portion, engaged by a corresponding inclined face uponA the slugs to ai'`v ford a camming action by which the disc or collar 10"` is pressed laterallyagainst the tension of the spring 12. In its outward position the slugs 15 Contact the inner side of the' overhanging commutator bars 5 as shown in Fig. 8. In Figs. 7 and 8 there is shown a further modification inwhich the eye or opening in the slugs 15', vthru which is extended the elastic ring 17, extending laterally to the edge of the slug. In other words, the opening in the slug'is in vthe orifice enabling the slugs 15 to be assembled laterally upon the ring or coil 17.

A further development and amplification of the subject matter of the present invention is illustrated and described, and the invention more broadly claimed in co-p'ending application Serial N o. 669,716, filed October 20, 1923, to.which reference isvto be had.

From the above description, it will be apparent that there is thus provided a device of the character described possessing the the invention has been described in language more or less specific as to structural features, it is to be understood that the invention is not limited to the specific'dctails shown, but that the means and construction herein disclosed comprise but one of several modes of putting the invention into effect, and the invention is therefore claimed in any of its forms or modifications Within the legitimate and validscope of the appended claims.

Having thus described my invention, I claim:

` l. In a short circuiting devicelfor motors,

a plurality of contrifugally actuated Weights "arranged circumferentially of the armature shaft of the motor and operable radially t`o effectv the electrical interconnection of the commutator bars of the motor, and a flat involute spring resisting the radial movement of the Weights and against the yielding resistance of Which the weights move under centrifugal influence to effect the short circuiting of the motor.

2. A short circuiting device for electric motors, a commutator and a disc relatively movable in axial relation against yielding resistance, the adjacent faces of said disc' and commutator being converging in a radial direction, a plurality of interposed Wedge shape centrifugally actuated circuit closer. members having marginal bearing surfaces extending in parallel relation with the adjacent faces of the disc and cominiitator upon Which they have sliding contact and commutator bar extensions into engagement with which the circuit closers are movable against the yieldingresistance of the con- `verging faces of the commutator and disc.

A short circuiting device for electric motors comprising a commutator and a disc in relatively spaced relation, a cam face on the commutator, centrifugally actuated circuit closer members having contact faces agreeing With the commutator cam face interposed between the commutatorand thc disc, and engaging the cam face to afford yielding resistance to their movement, and cominutator bar extensions engaged by the circuit closers when extended under centrifugal'infiiience.

A short circuiting device` for electric motors comprising a eominutator and a disc in relatively spaced relation, a cam face on the disc, centrifugally actuated wedged shapedcircuit closers interposed between the disfcland commutator having angularly circuit closers when extended under centrifugal influence.

A circuit closing device for electric motors, comprising two relatively movable members arranged in spaced relation, one of said members peripherally converging toward the other, centrifugally actuated wedged shape circuit closers interposed between the said members and having converging lineal bearing surfaces engaging the converging members in their movement to afford yielding resistance to their radial movement, and commutator bar extensions engaged Iby the circuit closers extended under centrifugal influence.

6. In a short circuiting device for motor commutators, an annular series of Weights arranged circumferentially of the motor shaft and revoluble therewith, said weights being radially movable under centrifugal influence to effect the short circuiting of the motor coinmutator and a radially crpansible and contractible (oiled spring the successive convolutions of Which are a rranged substantially concentrically relative to the annular series of Weights engaging with the Weights and acting to restrain their radial movement.

7. In a short circuiting device for electric motors, the combination with a plurality of commutator bars to be electrically connected one With another, of a series of centrifugally cont-rolled Weights, a fiat elastic band upon which the Weights are carried, said band being expansible and contractible in accordance with centrifugal influence of the Weights, said Weights When in their operated positions effectin'g the electrical interconnection of the connnutator bars one with another.

8. In a short circuiting device for motors, the combination with a plurality of commutator bars to be electrically connected one with another, of a series of centrifugally controlled Weights, each having an eye formed therein and having an entrance slot leading to said eye, an annular elastic retaining ring, engageable Within said eye thru the entrance slot, said ring heilig expansible under centrifugal influence of the weights, the weights when in ope-rated positions clfecting the electrical interconnection of the comn'iutator bars one with another.

9. In a short circuiting device for motors, the combination With a plurality of cominutator bars to be electrically connected one with another, of a series of centrifugally controlled Weights, an annular elastic ring acting to restrain the movement of the Weight under centrifugal influence comprising a flat strip Wound upon itself into convolute formation the outer convolutions of which possess greater contractive tendency than the inner convolutions, whereby the ends of the strip are made to closely adhere to the adjacent convolution, said ring being expansible under centrifugal inliuence of the weight to permit radial movement of the weights into the air operations positions to effect the electrical interconnection of the cominutator bars one with another. y

10. In a short circuiting device for electric motors, the combination with a plurality Vof commutator bars to be electrically connected one with another, of a series of centrifugally controlled weights, an annular elasticA ring having engagement with the weights comprising a flat strip wound upon itself into a convolute formation, expansible under centrifugal influence of the weights,

x said weights when -in their operated positions effecting the electrical interconnection of the commutator barsone with another.

1l. In a short circuiting device for motor cominutators, an annular' series of Weights arranged circumferentially of the motor shaft and revoluble therewith, said weights being radially movable under centrifugal iniuence to effect the short circuiting of the motor commutator, said` weights having registering eyes formed therein, vand access slots extending from said eyes to the marginal edges of the weights, and a retaining member insel-table through such slots into the eyes.

12. (In a short circuiting device for motor commutators, an annular series of Weights arranged circumferentially of the motor shaft and revoluble therewith, and movable vby centrifugal influence to effect short circuiting of the motor commutator,

and an annular lcontractile band yieldingly resisting the movement of said Weights and comprising a succession of concentric convolutions extending circumferentialiy of said band, the convolutions being maintained under opposing tension under which the outer convolution tends to contract and the inner convolution tends to expand wherei lweights are radially movable. i

lIn testimony whereof, I have hereunto set my hand this 26th day of June A. D. 1920.

EVERETT P. LARSH.

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