US1568675A - Short circuiter for electric motors - Google Patents

Description

Jan. 5 1926.

E. P. LARSH SHORT GIRCUITER FOR ELECTRIC MOTORS Filed Oct. 20, 1923 Patented il an. 5, 1926.

EVERETT 1. LABSH, OF DAYTON, OHIO.

SHORT CIRCUITER FOR ELE CTRIC MOTORS. I

Application filed October 20,'1923. Serial No. 669,716.

To all whom it may concern:

Be it known that I, EVERETT P. LARsH, a citizen of the United States, residing at Dayton, in the county of Montgomery and State of Ohio, have invented certain new and useful Improvements in Short C-ircuiters for Electric Motors, 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 automatically converting an alternating current motor from a repulsion starting condition to an induction running condition and vice versa in accordance with the variations of speed.

The. present construction embodies in a single structure the, advantageous features of both theflgovernor weight and garter spring type of short circuiting devices. One of the purposes of the construction is to give definition to the movement of the short circuiting members by which their movements' into and out of contact with the commutator bars will be decisive and which will eliminate the disadvantages of a gradual engagement and disengagement. The construction is further designed to embody the advantages of both the butt contact and the wiping contact.

To this end, the construction embodies an annular series of centrifugally controlled contact members located adjacent to the lateral or terminal face of the commutator and under centrifugal influence, possess a limited degree of oscillatory movement into butt contact with the ends of the commutator bars and upon further acceleration of speed possess expanding or radial movement in which they wipe the contacted ends of the commutator bars to insure clean, b'ri ht, electrical conducting contact surfaces. The

. contact members are inclined or beveled -at their inner ends whereby they normally extend in inclined relation with the axis of rotation in which position they are yieldingly that their center of gravity is normally displaced laterally beyond the plane of the annular resistance spring and in offset relation with the pivotal point or fulcrum of such members in their oscillatory movement. The

'centrifugal action upon rotation of the short circuiting device tends to move the center of gravity of the contact members mto the plane of rotation of its fulcrum or u-nter of oscillation which, in the present case, is at the opposite side of the plane of the restraining band or annular spring. The

Y movement of the contact members being limtion in a radial direction against the tensionor retractive action of the garter spring. The short circuiting'parts are enclosed and protected within a housing formed by a disc having an inclined inargiha'l1 flange approaching the ends of the commutator bars between which flange and the ends of the bars the extended members are wedged at the limit of their outward movement.

The object of the invention is to simplify the structure as well as the means and mode of operation of such circuit changin devices whereby they will not only be c capened in construction, but will be more efficient in use, automatic in operation, uniform in action, automatically controlled and unlikely to getout of repair.

A further object of the invention is to provide such centrifugally controlled short circuiting means which will promptly respond to variations of speed above and below a predetermined rate of rotation.

A further object of the invention is to i provide a short circuiting or current changing device which will have a definite make and break contact combined with a wiping action insuring perfect electrical contact and in which any clatter or vibration and the in cident arcing and burning of the contact surfaces will beelim'inated.

A further object of the invention is to provide such a short circuiting or current changing device which will be of compact form containing few parts and no pivotal joints or indirect movements, but in which the current controlling devices are directly operated by centrifugal tendency. 7

With the above primary and other incidental objeots in view as will more fully appear in the specification, the invention consists of the features of construction, the

parts and combinations thereof, and the mode of operation, or their equivalents as hereinafter described and set forth in the claims.

In the accompanying drawings wherein is shown the preferred but obviously not necessarily the only form of the embodiment of the invention, Fig. 1 is a longitudinal sectional view of a motor commutator to which the present form of short circuiting device has been applied. Fig. 2 is an end elevation of the commutator and short circuiting device, portions of which have been broken away. Fig. 3 is an enlarged detail View in which the relative movement of the short circuit device is diagrammatically indicated. Figs. i and 5 are similar views of a modification.

Like parts are indicated by similar characters of reference throughout the several views.

. The structure of the electric motor per se, forms no part of the present invention, which pertains wholly to the short circuitlng means for the commutator bars, by which the motor is caused to operate alternately as a repulsion motor and an induction motor.

An alternating current, repulsion-induction motor of the single phase type to which the present invention is particularly adapted isone which as the name indicates, starts as a repulsion motor and as the speed approacheslts normal or maximum rate of rotation automatically changes its character,

and runs as an induction motor. Briefly described, it consists of afield or stator of laminated toothed construction having a single winding thereon connected to the supply'clrcuit and a progressively wound armature or rotor with acommutator engaged by brushes during the starting or repulsion period together with speed controlled devices for short circuiting the armature windings through the commutator after the armature has attained a predetermined speed, which speed controlled means in some instances lifts the brushes from the commutator simultaneously with the short circuiting operation. There is no electrical connection between the stator and the rotor.

. The currents in the stator create an alterthe rotor or armature approaches a synchronous speed or one commensurate with the windings, whereupon the speed controlled devices operate to automatically short circuit the armature winding through the commutator. Thus the motor is automatically transformed from a repulsion type into an induction motor having what is essentially a squirrel cage rotor. ment of the speed operated governing or short circuiting device which forms the subject matter of the present invention. One of the 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 typical repulsion motor without compensation gives the most efficient starting torque possible while the single phase induction rotor with the squirrel cage armature or its equivalent affords the most efficient 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 compressors, grinding mills, etc. Requiring no starter, they are adapted for automatic control .or distance operation. They start quickly and operate quietly and smoothly.

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

Inasmuch as the construction of the motor per se forms no part of this invention, it has not been illustrated. It is to be understood, however, that the short circuiting moans forming the subject matter hereof is applicable to various styles of motors of the character heretofore indicated. Referring to the drawings, 1 is the armature shaft, on which is carried the usual commutator comprising the core 2 about the periphery of which are located a continuous succession of commutator bars 3, insulated from the core 2 and from each other by intervening bodies of insulating material.

In the present instance, the commutator bars 3 are shown terminating flush with the core 2 and in a plane perpendicular to the axis of rotation. however, that if desired the commutator bars 3 may project beyond or overhang the face of the core 2 and that further they may, if desired, be inclined or beveled at their ends and the contact members hereinafter described similarly beveled or inclined for co-operative engagement therewith.

The short circuiting means is embodied in a unitary structure capable of being assembled independent of the motor and applied thereto or removed therefrom without the necessity of disassembling either the motor or the short circuiting unit. However, the short circuiting device may, if desired, be assembled directly upon the motor shaft.

It is to be understood It is the improveof the invention as illustrated in the draw- I ,ings, there is employed a disc 6 adapted to v be secured to the armature shaft 1 adjacent to the face of thecommutator but in spaced relation therewith. This disc 1 forms a mounting and housing for the short circuit.

ing members. The disc 6 is formed with an inclined marginal flange 7 projecting toward the commutator in converging spaced relation therewith. -The disc 6 is further provided with an inner flange 8 forming a sleeve or hub which fits the armature shaft 1. The disc or housing 6 is secured to the shaft 1 by the clamp ring 9 threaded upon the shaft.

Located within the. housing 6 is an annular series of independent contact members 10. These contact members are slightly sector or wedged shape and are assembled side by side in an annular series in which each contact member is radially disposed in relation with the axis of the shaft. The

' contact members 10 are each formed with a lateral notch 11 which registers with like notches in the adjacent contact members to form an annular channel or pocket in the outer face of the assembly of contact members. The formation of this pocket or channel by provision of the notches 11 affords upon each contact member a laterally projecting-arm or finger 12 at the inner ends of the contact members. annular recess or pocket afforded by the registering notches 11 is an elastic retracting band 13. 'In the present instance, the retracting band 13 comprises an endless helical spring generally known as a garter spring. The retractive tendency of this annular band or spring 13 seats the inner ends of the contact member 10 upon the inner sleeve or hub 8 of the housing 6. The inner ends of the contact members or short circuiting elements are slightly inclined in relation with the contact faces of such members whereby, when in retracted relation with the terminal edges of the contact members seated upon the inner sleeve or hub 8, the contact faces 14 are spaced away from the ends of the commutator bar 3. Sufficient clearance is provided however that, upon oscillationof the members 10, the faces '14 may be brought into engagement with the ends of the commutator bars 3. To

' efiect such contact, the members 14) fulcrum upon their inner, corners 15 while the outer ends of the members swing toward the commutator bars under centrifugal influence as hereafter described.

The contact members or short circuitlng elements 10 are so proportioned and shaped that when in their normal retracted or seated position under the influence of the retractive band 13, the preponderance of weight of such members or the center of gravity Seated within the face of the commutator and offset in relation with the plane of rotation of the fulcrum point 15 and, in fact, beyond the plane of rotation of the retractive spring member 13. The annular s ring or elastic band 13- by its contraction a out the fingers or arms 12 tends to turn thecontact members 10 outwardly about their fulcrum points 15 into their retracted or inoperative positions wherein, as before stated, the center of gravity of the contact member is offset in relation with theplane of retraction of the spring.

As the commutator is. rotated, the short circuiting elements are carried with it. The centrifugal influence induced by rotation of the commutator tends to move the center of gravity of the contact members into the plane of rotation of their points of restraint. That is, the points of engagement of the garter spring or' elastic band 13. During this movement the contact members or short circuiting elements will fulcrum upon their inner points 15 thus tilting the .arms or. fingers 12 outwardly and subjecting the elastic band or garter spring 13 to extension. This oscillatory movement of the contact members 10 causes the faces 14 thereof to contact with the adjacent ends of the com-' mutator bars 3 and such movement is effected against the tension of the elastic band or spring 13. This initial position of contact is shown by dotted lines in Fig. 3. Upon further'increase of speed the centrifugal influence upon the members 10 will cause them to move outwardly with sliding or wipin contact upon the ends of the commutator ars against the tension of the re-. tractive band or garter spring 13 to their final position shown by dash lines in Fig. 3.

.In such final position, the outer ends of the contact members 10 engage and ride upon the inclined peripheral flange 7 of the disc or housing 6. Thisflange exerts a camming action which in conjunction with the centrifugal influence tends to press the contact members more firmly into the contact with the ends of the engaged commutator bars 3.

It will require an appreciable amount of influence or force to overcome the inertia of the contact members 10 as well as to over come the retractive tendency of the elastic band or garter spring 13. However, when the speed is reached at which such oscillation. of the contact members takes place, less effort will be required to move the contact' -members astheir centers of gravity approach the face of the commutator. Consequently such oscillatory movement, once initiated, will cause the members to quickly contact the ends of the bar. That is to say, it requires more effort to start the contact members from their positions of rest than to continue their movement into engagement with the commutator bars and the resistance to such movement progressively decreases, thereby insuring a quick and decisive shiftng movement under the initial impulse: In like manner, the retractive movement of the contact member is a quick and decisive shifting movement under the initial impulse. In like manner, the retractivc movement of the contact member is a quick and decisive one. as the centrifugal influence is relaxed to a point'of equality with or slightly below the equal influence of the spring or elastic band 13, the latter overcomes the centrifugal influence of the weight of the contact members tending to oscillate them outwardly about their fulcrum 15, the retractive influence of the spring being progressively increased as the leverage of the fingers or arms 12 increases thereby accelerating the breaking or releasing movement of the short circuiting members 10. Before this releasing or breaking movement is effected, however, the contact members are slidingly shifted in radial directions inwardly from their extreme outward operative positions to'their inner positions in which the fulcrum points 15 engage the flange or hub 8 of the housing 6 ,upon which points 15, the members then fulcrum under the retractive influence of the band or spring 18. The construction thus affords a sliding or wiping engagement in both directions and insures quick make and break movement by which arcing and burning of the contact faces is minimized.

In Fig. 5 there is shown-a modification, wherein in lieu of the annular retractive spring 13, ayielding collar 16 engages the arms 12, and constitutes the tension member hereafter mentioned in the claims against the yielding resistance of which the contacts are movable under centrifugal influence. The collar has a beveled ace 17 which by its cammin action, as th collar is urged axial- 1y by tile helical compression spring 18, exerts a retractive influence upon the contact slu s. The camming pressure of the beveled 001%11 retracts the contacts inward when distended, and also tends to oscillate them outward and away from the commutator when in their innermost positions. The overhanging marginal flange 19 limits the outward movement of the contacts. The relative location of the centers of gravity of the contacts and their action under centrifugal influence is substantially the same as beapparent that there is thus provided a device of the character described possessing the particular features of advantage before enumerated as desirable, but which obviously is susceptible of modification in its form, proportions, detail construction and arrangement of parts without departing from the principle involved or sacrificing any of its advantages.

While in order to comply with the statute 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 details shown, but that the means and construction herein disclosed comprises the preferred form of several modes of putting the invention into effect and the invention, is, therefore, claimed in any of its forms or modificatio'ns within the legitimate and valid scope of the appended claims.

Having thus described my invention I claim:

.1. In a short circuiting device for motors, an annular series of radially disposed centrifugally actuated weights arranged circumferentially of the motor shaft, a bearing point adjacent the inner end ofeach weight about which the weight is capable of lateral oscillatory movement to and from the motor commutator, and an annular contractile band circumferentially engaging portions of said Weights against the yielding resistance of which the weights are movable about their bearing points under centrifugal influence to effect the short circuiting of the motor commutator.

2. In a short circuiting device for motors, an annular series of radially disposed centrifugally actuated weights arranged circumferentially of the motor shaft, a laterally extending arm on each weight normally extending in approximate parallelism with the axis of rotation of the motor shaft and an annular tension member common to all the weights and circumferentially engaging the lateral arms thereof to yieldingly resist the movement of the weights under centrifugal influence, and against the tension of which the weights effect the interconnection of the motor windings.

3. In a short circuiting device for motors, an annular series of radially disposed centrifugally actuated weights arranged circumferentially of themotor shaft, each weight member being laterally indented and a helical spring the ends of which are inter-. connected to form an annular contractile band-common to the weights engaging in the lateral indentures thereof, against the yielding resistance of which the weights are moved by centrifugal influence to effect the interconnection of the motor windings.

4. In a short circuiting device for motor 'commutators, an annular series of weights arranged circumferentially of the motor to all the weights and exteriorly surrounding portions thereof, against the yielding resist ance'of which the weights effect their tilting movement under centrifugal influence.

5. In a short circuiting device for commutators, an annular series of weights arranged circumferentially of the motor shaft and revoluble therewith, said weights being capable of tilting movement toward and from the commutator under centrifugal influence to effect short circuiting of the motor commutator, a contractile band common to all the weights of the series and an annular seat for the contractile band formed in said weights in which the band is engaged to 'yi'eldingly restrain the tilting movement of the weights.

6. In a short circuiting device for motors, a plurality of centrifugally controlled elements arran ed circumferentially and operable in radial planes relative to the-armature shaft, said elements being laterally notched and an annular contractile band engaged in the registered lateral notches of the elements and acting to restrain the centrifugal action thereof as .said elements are rought in contact with the commutator" of the motor.

'7, In a short circuiting device for motors the combination with a commutator, of a short circuiting element consisting of a series of segmental weights arranged circum ferentially of the motor shaft and capable of both lateral tilting and radial movement under centrifugal influence and an annular tension member in engagement with the weights, and acting to'restrain the tilting and radial movement thereof.

8. In a short circuiting device for motors, a plurality of contact members arranged side by side in an annular series circumferential- 1y of the motor shaft and normally inclined away from the motor commutator and an annular tension member against the resistance of which said contact members are initially oscillated toward the commutator and subsequently moved radially under centrifugal influence.

9, In a short circuiting device for motors, a plurality of centrifugallyoontrolled weights arranged side by sidelin an annular series circumferentially of the motor shaft, and an annular tension member restraining said weights against movement, said weights being normally positioned with their centers 0f gravity offset laterally beyond the plane of restraining influence of the tension member, whereby centrifugal action will tend to oscillate said weights to move their centers of gravity into the plane of restraining influence, such movement of the weight members serving to effect the short circuiting of the motor windings.

10. In a short circuiting device for electric motors, the combination with a commutator of an annular series of short cirof the motor shaft and centrifugally actuated into engagement with the commutator bars, said elements having therein laterally opening registering notches, and an annular elastic band seated in the registering lateral notches and acting to restrain the centrifugal action thereof.

11. In a short circuiting device for motors, an annular series of radlally disposed centrifugally actuated weights arranged circumferentially of the motor shaft, a concentric seat at the inner ends of the weights upon which the weights fulcrum foroscillatory movement under centrifugal influence and an annular tension member circumferentially enclosing portions of 'said weights and exerting contractive influence upon said weights in a plane offset in relation with their fulcrum points, against the yielding resistance of which the weights are oscillated by centrifugal influence to effect the interconnection of the motor windings.

12. In a short circuiting device for motors, an annular series of radially disposed centrifugally actuated weights arranged circumferentially of the motor shaft a fulcrum bearing for each weight, about which the weight 1s capable of oscillatory movement into and out of short circuiting position, and an annular tension member common to the weights en aging the weights at points outwardly ra ially disposed relative to their fulcrum points and out of the plane thereof against the yielding resistance of which the'weights are capable of oscillatory movement to effect the interconnection of the motor windings.

13. In a short circuiting device for motors, an annular series of radlally disposed centrifugally actuated weights arranged circumferentially of the motor shaft, a restraining member common to the weights comprising a helical spring having its ends interconnected to form an annular contractile band, operatively engagin with said weights, the centers of avity o the weights being located radially yond and laterally out of the plane of the restraining member against the yielding resistanceof which the weights are movable under centrifugal tendency to effect the interconnection of the motor windings. v

14. In a short circuiting device for motors, an annular series of rad ally disposed centrifugally actuated weights arranged circumferentially of the motor shaft,.a tenable.

sioned restraining member comprising an annular contractile band operatively engaged with the weights, a fulcrum for each weight at the inner end-thereof, the centers of gravity of the weights being normally located radially beyond and laterally out of the plane of the fulcrums about which the weights are movable against the tension of the estraining member under centrifugal influe. cc to effect the interconnection of the motor windings.

15. In a short circuiting device for motors,

an annular series of radially disposed centrifugally actuated weights arranged circumferentially of the motor shaft, said weights being capable of both oscillatory and radial movement under centrifugal influence, to efl'ectthe interconnection of the motor windings and a yieldable restraining member common to the weights yieldingly resisting both the oscillatory and radial movement of the weights.

16. In a short circuiting device for electric motor commutators, an annular series of weights arranged circumferentially of the motor shaft and revoluble therewith, said weights being radially movable under centrifugal influence, said weights having in their radially disposed marginal edges a series of registering notches, and a contractile band engaging within the registering notches and yieldingly resisting the radial movement of said weights under centrifugal influence to effect the short circuiting of the motor commutator.

17. In ashort circuiting device for motor commutators, an annular series of weights arranged circumferentially of the motor shaft and revoluble therewith, said weights being movable under centrifugal influence to effect the short circuiting of the motor commutator, arms upon the weights extending axially relative to the motor shaft, and a contractile band surrounding the arms of the series of weights against the yielding resistance of which the weights are mov- 18. 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 movable under centrifugal influence to effect the short circuiting of the motor commutator, said weights being laterally recessed, and a contractile band seating in the lateral recesses of the series of weights against the tension of which the weights are movable under centrifugal influence.

19. 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 movable under centrifugal influence to effect the short circuiting of the motor commutator, a contractile band common to the weights of the series and an annular seat for the contractile band, formed in the lateral margins of said weights, in which the band is laterally engageable to restrain the movement of said weights.

20. In a short circuiting device for motor commutators of the characterdescribed, an annular series of weights circumferentially arranged relative to the motor shaft, said weights being radially movable under centrifugal influence to effect the short circuiting of the commutator, .a series of registering indentations in the lateral margins of said weights and a contractile band common to the weights seated in said registering indentations ag inst the tension of which the weights are-jlradially movable.

21. In ashort circuiting device for motor commutators of the character described, an

annular series of weights circumferentially arranged relative to the ,motor shaft, said weights being movable under centrifugal influence to effect the short circuitin of the commutator, a series of registering indentations in the lateral margins of said weights and a contractile band common to the weights seated in said registering indentations against the tension of which the weights are movable' In testimony whereof, I have hereunto set my hand this 4th day of October, A. D.

. EVERETT P. LARSH.

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