US1685549A - Short circuiter - Google Patents

Description

Sept. 25, 1928. 1,685,549

E. P. LARSH SHORT GIRCUITER Filed April 7, 1924 Patented Sept. 25, i I

UNITED STATES 1,685,549 PATENT OFFICE.

mama r. man, or DAYTON, onro, assrenoa TO 'THE masrna ELECTRIC com rm, or DAYTON, OHIO, a coaronarxon or onto.

' SHORT CIRCUITER.

Application filed April 7,

This invention relates to electric motors and more particularly to a short circuiting or "operation changing device for automatically converting an alternatingcurrent motor from a repulsion starting Condition to an induction running condition and vice versa,

in accordance with variations of speed.

The present invention embodies in a single unitary structure, the advantageous features of both the governor weights and garter spring type of 7 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 movement into engaging position will be initially retarded, and their action delayed until suflicient centrifugal influence is developed to overcome their initial resistance, after which they will move more easily and hence quickly into engaging position with increased pressure upon the commutator bars.

To this end the construction embodies an annular seriesof centrifugally actuated weight members, located adjacent to the lateral or terminal face of the commutators, and concentric with the axis of rotation, which move radially into and out of engagement with the commutator bars, against the yielding resistance of an annular retaining member which may be ofthe garter spring type, in combination with a cammin influence, the retarding influence of w iich is gradually decreased as the weights progress outwardly under centrifugal influence. Not only does the camming feature of the present construction retard the initial movement of the weight as a collection or body until the centrifugal influence is sufficient to carry them quickly into operative position, but it also prevents ununiform movement of the weights, which is one of the obj ectionable features to the garter spring type of short circuiter, as ordinarily constructed.

5 Unless some equalizing influence is exerted as in the present instance by the camming action, there is a tendency for one or more loosely held weightsto move initially in advance of the main body of weights, as the speed of rotation approaches the critical point, at which the short circuiting devices are to operate. While the weights may expand initially at one point in advance of those at another point, the inconsistency is of cour e only momentary, and immediate- 1924. Serial in. 704,670.

ly afterward the remaining weights will move to expanded position. Thus while the defect is objectionable, it is not vital. However, to meet certain conditions of use, wherein precision and accuracy of operation is essential and to conform to exacting trade requirements and commercial efficiency tests, the eamming feature in the present construction will equalize the expansive movement, restraining any loosely held weight-s until the more, tightly held members of the series are brought into operative position.

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

A further object of the invention is to provide centrifugally controlled short circuiting means, which will respond promptly to variations of speed above and below a predetermined range of rotation, by quick and decisive movement.

A further and primary objectof the invention is to provide a short circuiting or current changing device, in which the movement of the operating elements will be equaliz ed, employing a flexible garter spring, or circumferential band, as the retaining and retracting element.

A further object of the invention is to provide such short circuiting and current changing device, which will be of compact form, very few parts and no pivoted joints or indirect movement, but in which the current control devices are directly operated by centrifugal tendency.

With the above primary and other incidental objects in view as will more fully appear in the specification, the invention consists of the features of construction, of 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 embodiment of the invention, Fig. l is a longitudinal sectional view of a motor commutator,'and short circuiting deviceforming the subject matter hereof, applied thereto. Fig. 2 is an end view thereof, with the various parts broken away to expose underlying portions. Figs. 3, 1 and 5 illustrate various modifications of the short circuiting device and control means therefor. Fig. 6 is a detail view of two weight elements showing the different steps to which such elements are notched or recessed for free engagement and driving engagement respectively of the mounting disc. Fig. 7 is a detail showing such weights mounted upon the disc, one of the weights being in driving engagement therewith, and the other free. Fig. 8 is an enlarged diagrammatic view, showing the movement and relative positions of the weight members, illustrated in Figs. 3, 4 and 5. Fig. 9 illustrates a modification of the mounting disc for the contacts.

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 circuiting 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 is one which as the name indicates, starts as a repulsion motor, andas the speed approaches its normal or maximum rate of rotation automatically changes its character, and runs as an induction motor. scribed, it consists of a field or stator of laminated toothed construction having a single winding thereon connected to the supply circuit and a progressively wound armature or rotor with a commutator engaged by brushes during the starting or repulsion period together with speed controlled devices for short circuiting the armature wings 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 alternating flux which reacts on the rotor and induces its rotation. This type of motor, therefore, starts as asimple repulsion motor without compensating or auxiliary windings and operates as a repulsion motor until the 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. It is the improvement of the speed operated governing or tion rotor with the squirrel cage armature or its equivalent affords, the most efficient motor when running. 7

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 and analogous installations. Requiring no starter, they are adapted for automatic control or distant 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 desire 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 means 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.

The commutator bars 3 may terminate flush with the core 2, and in .a plane perpendicular to the axis of rotation as shown in Figs. 4 and 5, or they may project beyond or overhang the face of the core 2, or be inclined or beveled.

It is obvious that the particular form or shape of the commutator bars is not an essential feature.

In the preferred embodiment of the invention as illustrated in the drawings, there is employed a disc 6 secured to the armature shaft 1 in parallel spaced relation with the face of the commutator. Located intermediate the disc' 6 and the lateral face of the commutator, is an annular series of independent centrifugally operated weights 7. These weights? are slightly sector or wedge shape and are assembled sideby side in an annular series in which each weight member is radiall deposed in relation with. the

axis of rotation. The weights 7 are independent of each other, but each member is laterally restrained and supported by the adjacent weights of the series and guided thereby in its radial movement. In Fig. 1 the weights 7 are deeply notched or slotted on their inner margins and are mounted upon a supporting disc 8, fixedly secured intermediate the disc 6 and the face of the commutator, the periphery of which is straddled by the bifurcated or notched weight 7. In order to afford drivingengagement between the annular series of weights 7, and the supporting disc 8, in order that the weights may rotate in unison with the commutator, the disc 8 is peripherallv notched at intervals as indicated at 9. Certain weights 7 of the series are notched or slotted less deeply than the remaining weight as shown in Fig. 6. Such weights 7 having the shallow or less deep notches or slots straddle the supporting disc 8 at the bottom of the notches 9, as shown more particularly in Fig. 7. These special spaced weights 7 having the driving engagement with the supporting disc are capable of radial movement in relation with the disc, but are interlocked therewith against relative peripheral or rotary movement. Such driving weights 7 divide the annular series of weights into groups, the members of which intermediate such driving weights 7' freely straddle the peripheral margin of thedisc 8. The herein-described method of interlocking certain weights of the series at spaced intervals with the sup porting disc-by a sort of loose halved joint affords a simple, chea but highly eflicient driving engagement etween the weights and supporting disc. The exterior margins of the weights are notched to form with the succession of notched weights an annular peripheral groove about the series, in which is seated the annular contractile band '10.

This contractile band 10 is preferably though not necessarily an endless helical spring, sub- .ject to stretching or yielding pressure under centrifugal influence of the weight. The

weights fit quite loosely uponthe supporting disc 8, so that there is but little if any frictional resistance to their radial movement against the yielding tension of the enovercome the resistance of the retracting spring 12. Thus the weights will start their radial movement rather reluctantly and slowly. The accumulation of centrifugal influence necessary to initiate their movement and initially retract the disc 6 against the resistance of its spring 12 will be sufficient to carry the weights quickly to their destination, inasmuch-as the resistance of the disc is gradually decreased due to the deflection of the camming surface to more acute relation with the direction of movement of the weight. This camming function of the convex flange 11 also has the effect of pressing the weights laterally toward the commutator, and into firm electrical contact with the commutator bars 3. This is permitted by the more or less loose fit of the weights 7 upon their supporting disc 8. At their final limit of movement, the weights 7, having a wedging engagement between the commutator bars. 3, on'one side and the convex face of the inclined peripheral flange 11. 'of the disc on their opposite sides. Instead of being beveled on straight lines, the commutator bars 3 may likewise be provided with convex bevels for engagement of the weights 7 as shown in Fig. 1. In the construction shown in Fig. 1, the disc 6 not only exerts a camming action upon the weights 7 as they move radially, but under the influence of the retracting spring 12, the disc 6 exerts lateral pressure upon the weights7 at an angle to the direction of their radial movement, and toward the face of the commutator. struction shown in Fig. 1, the garter spring 10 restrains the weights radially, with yielding pressure, while disc 6 exerts lateral pressure thereon independent of the circumferential spring 10.

In addition to its other functions, the disc 6 equalizes the radial movement of the weight 7 or expansion of the annular series of weights, by restraining those loosely held wei hts, which might tend to move in advance of others. Obviously, the camming pressure of a few, scattered weights 7 upon the convex face of the flange 11 will be insuflicient to retract the disc 6 against the, tension of its spring 12. The resistance of the spring 12 is such as to necessitate the Thus in the coninitiate their movement prematurely against the resistance of the garter spring 10, will be restrained by the inclined flange 11 of the disc 6.

In Fig. 3 there is shown a modified construction, wherein the bifurcated weights 17 straddle the supporting disc 8, as before described, and are circumferentially surrounded by the contractile garter spring 10. However, in this construction the dise16 corresponding to the disc 6 of the previous construction is stationarily' mounted in relation with the commutator, and a second annular contractile spring 18 performs the function of the spring 12 previously mentioned, exerting lateral pressure upon the weights. In this construction the weights 17 are formed with notches in their outer margins to afford an inclined beveled face 19. The registering of these notches upon each weight with its neighboring weight affords upon the annular series a beveled cam surface. The stationary disc 16 is formed with an annular groove 20 therein. registering with the notches of the weights 17. The annular contractile spring 18 bears upon the converging inclined faces 19 and 20 of the notches in the weight and the annular groove of the disc respectfully. The contraction of this band 18 exerts ramming act-ion upon the inclined face 19 of the weight, urging the weights 17 inwardly toward the commutator. To reduce the frictional resistance to outward radial movement of the weights under centrifugal influence, the inner margin of the weight is cut away, leaving a bearing point 21 adjacent to the outer end of the weight engaging with the face of the commutator and riding upon the commutator bars as the weight is extended, while the commutator core is provided with a head or reduced bearing face 22 upon which the weight-17 slides radially. This bead or limited bearing surface 22 is preferably, though not necessarily located in such relation with the point of application of pressure by the auxiliary spring 18, that when the weights 17 are fully retracted, such inward pressure will be slightly below the point of bearing upon the head 22, and consequently the lateral pressure of the weights at their bearing point 21 will be slightly relieved. However, as the weight moves outward and the point of pressure of the spring 18 moves beyond the bearing beads 22 the tendency will be to tilt the weights 17 toward the commutator and so insure more firm engagement with the commutator bars 3.

As the weights 17 move radially, they not only are subjected to camming action by the spring pressure upon the beveled face 19, but they expand the contractileannular band 18 radial-1y and at the same time displace this spring laterally out of its normal plane. The relative positions and spring action are best shown in the diagrammatic view Fig. 8. As the weights 17 are shifted radially, the marginal notch is moved out of registery with the annular recess or groove in the stationary disc 16, successive positions being indicated by dotted lines in Fig. 8. This movement gradually forces the contractile annular spring 18 up the incline 20 of the annular groove or recess, in the disc and out of the notches in the weights. However, this spring never entirely leaves the notches. Like the spring 12 of Fig. 1, the annular contractile band 18 resists the expansive movement of the annular series of weights, and simultaneously subjects the weights to lateral pressure in a direction angular to their radia'l movement. This spring 18 also tends to restrain any premature movement of a few weights in advance of the general movement of the annular series. The resistance of the spring 18 to the simultaneous expansion and lateral displacement of the incline 20 of the annular grooved recess in the disc is too great to be overcome by the action of a limited number of weights, and the combined action of approximately the full annular series.

In its retractive action, the resistance to expansive or radial movement of the weights the annular spring 18 is supplemental to the circumferential spring 10 which may be omitted. In Figs. 4 and 5, the radially movable weights are found controlled solely by the annular spring 18, seated in the registering notches of the weights and the annular groove of the disc.

The construct-ion shown in Figs. 4 and 5 is quite similar to that shown in Fig. 3 except for the omission of the circumferential spring 10. In Fig. 4 the movable weight 17 is shown provided with two bearing points 21 and 23. In Fig. 5 an annular ring which may be merely a solid wire ring or a second annular helical springof the garter variety is employed in lieu of the reduced bearings 22 and 23 of Figs. 3 and 4. An annular helical spring employed as the bearing 24 will afi'ord a limited rolling action to facilitate the radial movement of the weights.

In lieu of the peripheral indentations 9 of the disc 8, such disc may be laterally indented or grooved radially as at 9' in Fig. 9, in which event the notches or slots of the driving members of the series would be somewhat less wide than the remaining members for driving engagement in the radial grooves 9'.

From the above description it will be apparent 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; y

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 modifications within the legitimate and valid scopeof the appended claims.

Having thus described my invention, I claim:

.1.- A short circuiter construction for electric motors of the type wherein an annular series of weights are radially movable under centrifugal influence against the yielding resistance of a tension element to effect the electrical interconnection of the windings of a motor, characterized by a disc mounting for the radially movable weights the margin of which is straddled by the weights which are bifurcated for such engagement, the disc being provided with peripheral notches and certain Weights of the series being seated in such notches and dividing the series of weights into groups for the purpose of insuring rotation of the weights in unison with the disc, said weights being radially movable independently thereof.

2. A short circuiter construction for electric motors, an annular series of weights radially movable under centrifugal influence, a

tension element against the yielding resistance of which the weights operate to effect the electrical interconnection of the windings of a motor, the weights having lateral registering cam notches in their margins in which the yielding tension element engages to exert camming pressure in inwardly radial and lateral directions.

3. In a short circuiter for electric motor commutators, amannular series of centrifugally actuated weights arranged circumferentially and operable radially, relative to the armature shaft with which the series of weights rotates to effect short circuiting of the armature windings, said weights being bifurcated with certain of the weights at separated. intervals bifurcated lessdeeply than intermediate weights, a revoluble disc astride the periphery of which the weights are mounted, such disc having peripheral notches in whichthe less deeply bifurcatedweights are seated astride the disc to afford driving engagement with the disc for the remaining weights. 1

4. In a, short circuiter for electric motor commutators, an annular series of centrifugally actuated weights arranged circumferentially and operable radially relative to the armature shaft with which the series of weights rotates to effect short circuiting of the armature windings, a disk having therein a series of indentations, the weights being bifurcatedand mounted astride the periphery of the disc with weights of the series engaging in the indentations of the disc at separate intervals to afford driving engagement, insuring unison rotation ofthe weights and disc.

5. In a short circuiter for electric motors, an annular series of centrifugally actuated weights arranged circumferentially and operable radially relative to the armature shaft with which the series of weights rotates to effect short circuiting of the motor armature windings, registering cant notches in the lateral margins'of the weights, and anannular contractible band seated in said lateral cam notches tending to simultaneously retract the weights inwardly in opposition to centrifugal influence and to press the weights toward the commutator of the m0- tor.

6. In a short circiter for electric motors, an annular series of centrifugally actuated weights arranged circumferentially and operable radially relative to the armature shaft, and means for yieldingly resisting the radial movement of the Weights into short circuiting position and exerting lateral pressure thereon, including registering lateral cam shaped indentations in the margins of the weights, and a yieldingly member operatively engaging the cam shaped indentations.

7 In a short circuiter for electric motors, an annular series of centrifugally actuated weights arranged circumferentially and operable radially relative to the armature shaft, said Weights having registering notches in the lateral margins thereof, and a yielding control member having camming engagement within said lateral notches to yieldingly resist the radial movement of said weights and simultaneously urge said weights laterally.

8. In a short circuiter for electric motors, an annular series of centrifugally actuated weights arranged circumferentially and op' erable radially relative to'the motor armature shaft, said Weights having registering cam faces thereon spaced inwardly from their outer ends, and an annular contractile member having operative engagement with said cam faces, against the resistance of which the weights are radially movable under centrifugal influence into operative engagementwith the bars of the motor commutator. g

9. In a short circuiter for electric motors, an annular series of centrifugally actuated weights arranged circumferential-11y, and operable radially relative to the motor armature shaft. The weights and lateral face of the motor commutator having normally engaged spacedpoints of contact upon which the weights ride in their to and fro radial movement, and means for yieldingly resisting the movement of the weights under cen- 5 trifugal influence.

10. In a short circuiter for electric motors, an annular series of centrifugally actuated weights arranged circumferentially and operable radially relative to the motor arma- 10 ture shaft, spaced lateral bearings upon which the weights are slidingly adjustable into and out of short circuiting engagement with the bars of the motor commutator, and means for urging said Weights against said spaced bearings simultaneously with the to and fro radial movement of the weights.

In testimony whereof, I have hereunto set my hand this 5 day of April, A. D. 1924.

EVERETT P. LARSH.

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