US1577736A - Short circuiter - Google Patents

Description

MM 23 192a.

E. P. LARSH SHORT CIRCUITER Filed Feb. 15, 1924 Patented Man 23, 1926. I

v UNITED STATES PATENT want I FF'i Q E a nvnanrr r. Luisa, or Darren, onro.

snofar cmcurrnn;

Application filed February 15, 1924. Serial No. 898,020.

I motor from a repulsion starting condition to equalize the short circuiting movement of to an induction running condition and vice versa in accordance with variation of speed.

The, present construction embodies in a single structure the advantageous features of both the governor weight and garter spring type of short circuiting (lGVlCQS. ne of the purposes of the construction is an annular series of independent radially movable contact members to effect the simultaneous engagement of all commutator bars. One of the objectionable features of the garter spring type of short circuiter or one wherein the contact members oper ate against the yielding resistance of a flexible retaining and retracting element is the tendency for the contact members to move ununiformly. As the speed of rotation approaches. the; critical point at which the short circuiting'devices are to operate, the

tendency is to expand eccentrically or un-,

uniformly against the resistance of the flexible retainer. Thepontact members of such short 'circuiters of" the garter spring type being loosely mounted in an annular series,

' some of the members may be held more loosely than others, due to variation of the frictional contact or pressure laterally between succeeding, elements of the series. 'The tendency is for such loosely held con;

tact elements tomove' outward into engagement with the commutator. bars in advance of the remaining contacts of the series. lVhile the contacts may expand initially at one point, the eccentricity is of course only momentary, and immediately afterward the remaining contacts will expand. 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, it is quite desirable that the movement of the contact elements be equalized, andany loosely held .elements be of contact members against the yielding resistance of which the members are radially movableinto engagement with the commutator bars, under centrifugal influence. The particular feature in the present instance consists in inter osing between the annular series of independent radially movable contact elements and the circumferential contractile retaining band an in flexible movable collar or equalizer, against which the contact members exert pressure in their outward or operative movement, and which in turn transmits the pressure against the yieldin resistance of the circumferential contractile band.

The object of the invention is to simpli-i fy 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 efficient in use, automatic in operation, uniform vin .action, automatically controlled and unlikely to et out of repair.

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

A.fu-rther and primary object of the invention is to provide a short circuiting or current changing device in which the movement of the operating elements will be equalized, while employing a. flexible garter spring, or circumferential band, as there taining or retracting element.

respond promptjoints or indirect movements, but in which the current controlling 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, the parts and combinations thereof, and the mode of operation or their equivalents as hereinafter described and set forth in the claims.

In the accompanyin drawings, wherein is shown the preferre but obviously, not necessarily the only form of 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 view thereof, with various parts broken away to expose underlying portions. Figs. 3 and 4 are sectional views similar to Fig. 1, illustrating modifications.

Like parts are indicated by similar characters of reference upon 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 whichthe present invention is particularly adapted is one which as the name indicates, starts asa. repulsion motor and as the speed approaches its normal or maximum rate of rotation automatically changes its character, and runs as an induction motor. Briefly described, it consists of a field 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 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 alternating flux which reacts on the rotor and induces its rotation. This type of motor, therefore, starts as a simple 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 controlleddevices operate to automatically short circuit the armature winding through the commutator. Thus the motor is automatically trans:

formed 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 circuiting device which forms the subject matter of the present invention. I

mature or its equivalent affords, themost' 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, grindmg mills, and analogous installatlons. Re-

quiring no starter, they are adapted for automatic control or distant operation. They start quickly and operate quietly and smoothly; I a "The above is offered merely to facilitate a thoro 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 com-' mutator 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 bar is not an essential feature.

In the preferred embodiment of the invention as illustrated in the drawing, there is employed a disc 6 secured to the armature shaft 1, adjacent to, but in 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 contact members 7 These contact members are slightly sector or wedge 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 rotation. Furthermore in such series, each independent contact member is laterally restrained and supported by the succeeding contact members of the series and guided thereby in its radial movement... As shown in Fig. 1, each of the contact clined or tapered exterior of the annular series of contact members, is an elastic flex ible retaining and retracting band 10. This band 10 preferably comprises a helical spring, the ends of which are interconnected to form a continuous circular contractile member.

Upon rotation of the commutator and the series of contact members, centrifugal influence causes the contact member 7 to move outwardly in a radial direction against the yielding resistance of the circumferential contractile band 10. The contractile band 10 not only yieldingly resists the outward movement of the contact members 7, but dueto the inclination of the exterior margins upon which the contractile or retract in ressure is a lied a ca min action is exertedby which the contac '?members are pressed inwardly toward the commutator, whereby as they move outwardly they have a wiping or sliding engagement upon the ends of the commutator bars. I,

As before mentioned, if the yielding resistance or spring tension of the contractile" band 10 is applied directly to the" individual contact member 7, some of the individual contact members which may be loosely held between their neighboring members will res 0nd more quickly to the centrifugal influence and will move outward against the flexible yielding band, in advance of the main body of contact members. Such partial operation is. prevented in the present instance by interposing between the series of contact members and the contractile band 10, an inflexible tapered or inclfned collar 11, against-the inner circumference of which the tapered margins of the contact members exert outward camming pressure and against the outer tapered circumference of which the contractile band 10 exerts its retra'ctive pressure. The.

outer periphery of this tapered collar 11, extends in diagonal or angular relation with the plane of the disc 6. The contractile band 10.is seated within the tapered groove or recess formed by the divergent relation of the disc 6, and the interposed inflexible collar 11, The contractile or camming action of the circumferential band or spring '10 tends to press the tapered collar 11 axially inward toward the commutator, and against the tapered outer margins of the contact members. The contact members are thus subjected to pressure in two directions. That is, inwardly in a radial direction toward the center of rotation, and laterally in an axial direction toward the commutafl tor face. The outward camming pressure of the inclined ends of the contact members upon the. interior surface of the tapered collar 11 tends to cam such collar axially away from the commutator and toward the disc 6. It is 'to' be noted that the collar is so proportioned and is of such width that when urged inwardly by the contraction of the external band or spring 10, it occupies a spaced relation with the disc 6'. This clearance intermediate the tapered collar 11, and disc 6 permits its lateral movement as the contact members 7 move outwardly.

This. lateral shifting movement of the tapered collar 11, under outward pressure of the contact members exerts an outward camming action upon the contractile circumferential spring 10, expanding the spring against the yielding resistance of which the tapered collar 11 moves laterally under the outward radial pressure of the contact members due to centrifugal influence. The operated relation of the parts is shown by dotted lines in Fig. 1. The tapered collar 11 serves to restrain any loosely held contact members until the entire body of members is subjected to suflicient contrifugal influence to cause their movement in unison. Likewise if the spring 10 is of unequal resistance throughout its extent possessing a tendency to yield more easily at one point than at another, such condition is'corrected' by the interposed tapered collar 11. To the contrary, the interposed tapered collar serves to concentrate the entire resistance of the contractile band l0,upon any loosely held slug or slugs, which might tend toward radial movement in advance of the others. It is obvious that before any contact member or group of contact members can move radially in advance of the main b dy ,of such members, Such member or members must force the tapered collar 11 laterally against the retractive tension of the entire circular band 10. Without such interposed inflexible tapered collar 11, there is a tendency for the contact members to flex the retaining band locally orat one point only to accommodate such uneven expancontact members.

sion or advance movement of individual Such irregular or individual action of the 'contact members is prevented by the interposed collar 11.

In order that the contact members may rotate in unison with the commutator the disc 6 is preferably though not necessarily provided with inwardly projecting ears or lugs 12, at spaced intervals, which project between succeeding contact members of the annular series separating the series into groups and affording a driving connection which further tends to guide the contact members in 'their radial movement.

In Figs. 3 and fl there is shown a modification, where in lieu of the annular tapered collar 11, previously described, there is employed-an axially movable disc 13, having a tapered or inclined flange 14, projecting in divergent spaced relation with the disc 6. The contractile band or retaining member 10 is seated in the divergent groove or recess intermediate the inclined flange 14 and the disc 6, and by its contraction tends to urge the disc 13 inwardly toward the commutator face, The contact nem hers 7 are located intermediate the movable disc 13, and the face of the commutator. These contact members 7 in their outward or radial movement, bear upon the inner inclined face of the flange 14, and exert an outward camming movement upon the disc 13, tending to move the disc axially away from the commutator, and in turn exert a camming influence upon the contractile band 10 expanding such band against its yielding resistance as the disc 13 approaches the disc 6. The function, operation and result of this construction is substantially identical with that shown in Fig. 1 and previously described. Fig. 4

illustrates the parts mounted in a unitary structure, applicable to and removable from the armature shaft without disassembly. The stationary disc 6 and movable disc 13 are carried upon the laterally projecting central sleeve or hub 15 of a third disc adjacent to the face of the commutator,

the contact members 7' being interposed between the disc 13 and the disc 16. By

such construction the short circuiting unit may be assembled independent of the motor and subsequently applied thereto, or removed therefrom at will, as a single integral structure.

In order that there may be driving engagement between the rotating parts and the contact members, the disc 16 may be radially beaded vorgrooved as may be de sired, or such radial lineal configuration may be formed in the disc-13 to guide the contact members in their radial movement and insure their rotation in unison with the commutator. I

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 obvi-- ously is susceptible of modification in its forms, 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 s eclfic as to struc--,

tural eatures, it is ,to understood that the invention is not limited to the specific tators, an annular series of weights disposed-- concentrically and radially in relation with the armature shaft, and movable radially in relation thereto under centrifugal influence,

a flexible contractile band ciroum'ferentially surrounding the series of weights against the tension of which the weights move 'radially under centrifugal influence to effect the short circuiting of the commutator, and a yieldingly mounted inflexible band interposed between the weights and spring restraining the unequal distension of the annular series of-weights.

2. In a short circuiter for motors, an annular expansible and contractible series of centrifugally actuated weights an annular;

yielding tension spring against the resistance of which the weights move radially under centrifugal influence to effect the short cir c-uiting of the motor armature, and an equalizing element interposed between the annular spring and the weights restraining the unequal distension of the annular series of weights.

3. Ina short circuiter for electric motors, an annular expansible and contractible series of centrifugally actuated weights, an annular contractile band circumferentially surrounding the weights against the resistance of which the weights are radially movable under influence of'centrifugal influence, to effect the short circuiting of the motor armature, and equalizing means additional to the circumferential band for yieldingly restraining .ununiform movement of the weights. i

4. In a short circuiter for electric motors, an annular series of centrifugally actuated weights, radially movable under influence ofcentrifugal influence, to effect the short oircuiting of the motor armature, said series of weights being peripherally beveled, and

an inflexible tapered collar circumferentially surrounding the weights and engaging with the beveled (peripheral face thereof, and

tending to yiel ngly restrain ununiform radial movement thereof, said collar being axially movable under the camming influence of the weights, and an expansible and contractible tension. element resisting the lateral movement of the collar and expanded by the .Wedging action of the tapered collar under expanding influence of the weights.

5. In a short circuiter for motors, an annular series of centrifugally actuated weights, an axially movable abutment member engaged by the weights upon radial movement thereof-and restraining unequal movement of said weights, said abutment member having an external tapered cam face, and a yielding tension member engaging the external tapered face of the abutment member to resist the axial movement thereof.-

"6. In a short circuiter. for motor commutators, an annular series of'centrifugally actated weights, said weights being beveled to present an exterior inclined face divergent to the axis of rotation, an elastic contractile u'ated weights, an annular contractile band against the tension of which the weights are radially movable to effect the short circuiting of the motor commutator, and an axially movable tapered collar engaged by the weights upon radial movement tending to resist ununiform expansion of the series of weights, said tapered collar being exterio-rly engaged by the contractile band and laterally displaced by the combined camming action of the weights during their radial movement against the tension of the contractile band.

In testimony whereof, I have hereunto set my hand this 28th day of January, A. D. 1924.

EVERETT P. LARSH.

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