US1705231A - Short-circuiting device - Google Patents

Description

March 12 1929. D. M. BLISS 3 IIIIIIIIIIIIIIIIIIII a I v en l-ar /V/ flood/c Patented Mar. 12, 1929.

UNITED STATES PATENT OFFICE.

DONALD M. BLISS, OF CHICAGO, ILLINOIS, ASSIGNOR TO BODINE ELECTRIC COM- PANY, OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS.

SHORT-CIRCUITING DEVICE.

Application filed July 25,

My invention relates to short-circuiting devices tor repulsion induction motors of the single-phase conm'mtator type, as employed for automatically short-circuiting the entire commutator when the motor has attained a predetermined speed and particularly to the i elass of such short-circuiting devices in which the short-circuiting member .is moved in one direction by the action of centrifugal force on weights and .in the opposite direction by a retracting spring.

Among the general olnects of my invention are those of providing a device for this purpose consisting of very few and easily nlanutactured parts, and one wh ch wlll be easy to assemble or disassemble. Further ob- 'jects are those of providing a movable shortcireuiting member arranged itor engaging pcripheral and tapering parts oi. the commutator segments with a wiping action and with freedom for movement botl rotationally and longitudinally of the comn'mtator, and or providing a short-circuiting device in which the device-contacting portions of the commutator are exposed for convenientcleanmg and refinishing when the motor is not running. My invention also provides construction in which a single-piece member is directly engaged both 4 by the centriliugally movable weights and by the retracting spring, and in whihh this member also contacts with the commutator segments to e'li' ect the sl'iort-circuitin lvl oreover. my invention provides a short circuiting device in which the major operating parts are all freely rotatable on the shaft otthc motor, wln-ireby the short-circmting member continually presents di'lferent portions to any given commutator segment and whereby I reduce internal friction in the device.

Sti ll turthe and also more detailed objects will ap ear from the following specification and from the accompanying drawings, in which Pi 1 is a side elevation oi? one end of the commutator of an armature, together with a central and axial section through a short-circuiting device embodying my invention showing the latter as it appears when the motor is standing still.

Fig.1. 2 is a section similar to the right-hand upper corner portion of Fig. 1. showing the disposition of the parts when the motor has 1927. Serial No. 208,217.

speeded up so that the short-circuiting member engages all of the commutator segments. Fig. 3 is a view taken from the line 33 of F l, with portions of the cap and ot the SllOl'll-Cllfillltlllg member broken away.

Fig. 4 is a perspective view of the lower weight of Fig. 3 together with guide stems carried by this weight. 7

In the illustrated ei'l'ibodiment, the com mutator segments 1 are all beveled at their righahand end to a iiinitorm frustro-conical form to afford sloping contact portions 2. Sleeved upon the shaft 3 adjacent to this end. of the armature is a bushing at. This bush ing has a radially enlarged end 5 at its outer end, and the bushing is held close to the armature by any suitable means, such as a pin 5 driven through the bushing end 5 into the shaft.

The main shank portion 4t ot the bushing extends treely through central per-i erations in the back 7 of an outer weight-guiding memher, and in the fiat and disk-shaped main portion 8 of a shm't-circuiting member, and those portions 7 and 8 are spaced longitudinally of the shaft by a pair of relatively slidable weights 9. The slun't circuiting member also includes an annular cam portion 8 which flares radially outward, toward the back of the said cap, a relatively still tubular portion 8" extending toward the comumtator from the outer edge of the cam portion 8*, and a contact portion 8 which flares toward the commutator at an angle correspond ing to the slope of the segment contact portions 2.

Th e weights 9, which desirably are oi a nonmagnetic metal (such as brass or a die-cast metal) are slidably connected to permit their moving radially of the shaft both toward and away from each other while preventing relative movement of the weights circunrterentially ot the shaft, thus keeping the weights diametrically opposite each other. For this purpose I am here showing the weights as connected by a pair of parallel rods 10, each of which rods is secured to the lower weight 9 (in Fig. and slides treely in a bore ll in the upper weight.

Each weight has its radially outward edge 9 beveled towards the connnm'ator to a shape conforming substantially to the flare oi the cam portion 8 of the short-circuiting member. Consequently, a movement of the weights radially outward of the shaft will cause the said portions 9* by a cam action on the cam port-ion 8 of the short-circuiting member to move the latter member towards the commutator. Such motion is resisted by a compression spring 12 interposed between the armature and the disk-like main portion of the short-circuiting member, and by suitably proportioning the strength of the spring to the weights, I can deter the above described cam action until the armature reaches a substantially predetermined speed. Likewise, by suitably proportioning the sizes oi the various elements, I can cause the longitudinal sliding movement of the short-circuiting member (as due to the said cam action when the weights fly outward) to force the flap-1mg contact portion 8 of that member into lirm contacting engagement with the tapering end portions 2 of the commutator segments. To secure an effective contacting with all of these segments, I preferably provide this portion 8 with radial slits 13, as shown in Fig. 3, which slits divide the said portion into contact fingers as shown in Fig. 3. 7

When the current to the motor is shut oil, so that the speed of the arn'iature falls, the radially outward centrifugal thrust on the weights drogs,so that this thrust can no longer overcome thepressure of the spring 12. This spring pressure 12 then forces the shortcircuiting member away from the armature, and the cam portion 8 of the latter forces the weights radially inward until stopped by engagement with the shank l of the bushing, as shown in Fig. 3. Since the spring, the shortcircuiting member, the interconnected weights and the cap are all freely rotatable on the bushing (and hence with respect to the shaft), these parts can readily shitt ro tationally with respect to the commutator. Consequently, the contact lingers on the short-circuiting memberwhich member desirably is made off a spring bronze or the likenot only engage the beveled segment ends with a wiping movement longitudinally of the commutator, but also in continuously changing positions of the contact fingers with respect to the numerous commutator segments. This rotational shifting may be aug mented by a shifting in the position or" the weights rotationally of the two members between which the weights are interposed. Consequently, the provisions for the free rotation of so many parts of my device cause the wear to be distributed, thus prolonging the life of my contrivance.

Moreover, when the armature is standing still as in Fig. 1 the beveled commutator ends are readily accessible both for examining them and for sand-papering or otherwise refinishing them it desired, and the contact linger portions oi the short-circuiting member are likewise readily accessible. This makes it easy for the user to maintain the motor in fine working condition, which has not been possible with devices in which the contact is on undercut segment parts or on the flat ends of segments.

While a flat disk portion 7 sullices as the outer guide for the weights, 1 desirably provide this outer weight-guiding member with a peripheral flange 7 extending toward the lingered contact portion 8 thereby housing the major portion of my device against the entrance of dust. If any dust or the like should still enter, this will readily be thrown out by centrifu al force, so that my device is practically self-cleaning.

racing void or all levers, pivot pins and the like, my entire device is unusually simple and obviously inexpensive, besides being unusually to assemble. Moreover, it requires no special commutator construction, as the .mere beveling of the free end of an ordinary comn'uitator suli'ices. So also, my entire device is highly compact longitudinally of the armature.

Both of the two cup-shaped members between which the weights are disposed are easily formed by punch-press operations, and when the armature is standing still, the spring ps the weights between them, This JPiilg action continues to prevent a radially outward movement of the weights until thejspeed is such that the centrifuu ally actualer. J i

thrust of the weights, acting through the said pressure of the spring.

cibpcrating cam portions, overcomes .ily Tl lit?- my do Consequently, r can 1 cted soc-ed by merely choosing a cc responsive to se 1 spring of suitable ")ower in proportion to the weights.

'nterposing a cylindrically bored tubuportion 8 between the contact lingers and the annular can portion of the short-circuiting member, I make this connection rigid for read ly transmitting the thrust, and by extending the beveled cam portions ol' the weights over large .irs l di:-:tril ute tl cam thrust over a considerable portion of the circumference oil. the substantially cup-shaped illgdl-CiT'Ctllililg member. l lowever, while r nave pictured and described my invention. in an eiubodin'ient including two weights, bushing end. for receiving the thrust. and a tubular housing portion on the outer weightguiding member, l do not wish to be limited to these or other details or the construction and arrangement thus disclosed. Many changes might obviously be made without dc parting either from the spirit of my invention from the appended claims. I

l claim as my invention:

1. The combination with a. commutator, of a single-piece and substzuitially cup-shaped short-circuiting member movable axially of the conmlutator and having the radially outer portion of its cup bottom tapered radially inward toward the conunutator to form an annular cam portion, weights movable radially lOU of the commutator and having radially outer beveled portions continuously engaging the said annular cam portion, and guide means for preventing movement of the weights longitudinally away from the commutator, the guide means and the short-circuiting member being freely and independently rotatable with respect to the commutator about the axis of the latter, the said men'ibcr having its mouth end portion adapted to engage the commutator.

The combination with a motor having a shaft projecting beyond. its commutator, of centrifugally actuated short circuiting means comprising: two weights at opposite sides of the projecting shaft, a pair of guides at opposite sides of the weights and both freely and inrlependently rotatable with respect to the comniuiator, stop means fast upon the shaft for maintaining the gu de furthest from the commutator at a fixed distance from the commutator, the other guide being movable toward and away from the connnutator and having integral contact fingers adapted to short-circuit the comnmiator, the said other guide and the weights having inter-engaging); frustro-conical. cam faces for cruising radii .iy outward movement of the weights to move the last named guide toward the con'unutator; the said short circuiting means being bodily detachable as a unit from the motor.

3. A commutator and short-circuiting device combination as per claim 2, in which the 7 stop means include rods respectively fast on one and slidably engaged by other of the weights.

4. The combination with the commutator of an induction motor, of a short-circuiting member slidable towards and away from the outer end of the COIIllIlUtzliOl, spring means resisting the movement of the said member toward the commutator, and weights movable radially outward of the axis of the con'nnutator by centrifugal force; the weights and the sa d member having inter-engaging frustroconical cam faces disposed so that when the weights are moved radially outward by centrifugal force the said inter-engaging cam faces will cause the short-eircuiting member to move axially toward and into engagement. with the connmitator, and will also cause a movement of the said member away from the commutator to move the Weights radially inward in combination with a cup-shaped guide member having a flat and rigid cup bottom engaging the side of the weights away from the commutator, the said guide member housing the major portion of the short-circuiting member, and means for preventing movement of the said guide member away from the commutator.

5. In an induction motor, a commutator having the outer end of its segments beveled to afford faces in a common conical surface, a shaft coaxial with and projecting beyond the commutator, a stop member mounted on the shaft a fixed distance from the commutator, an inner metal cup having its mouth directed toward the commutator and slitted at its n'ionth end to afford fingers adapted to engage the said beveled segment faces, the said cup having the radially outward portion of its bottom sloping inwardly toward the commutator to a ii'ord a f ustroronicai cam portion; an assemblage of flat weights engaging the outer face of the said cup bottom, each weight having an arcuate outer edge portion beveled to conform substantially to the said cam portion, the Weights assemblage including means for spacin the weights synunetrieally about the axis of the commutator while permitting movement of the weights radially of the commutator, an outer cup freely housing the said inner cup and having its bottom spacing the l s from the said top member, and a comon spring interposed between the commutator and the bottom of the inner cup.

(3. The combination with a motor having a shaft ],)lf()jCCllll1g beyond the end of its commutator, of a bushing dctachably secured to the shaft and having an enlarged head spaced from the comn'iutator; two guides independently journaled on the shank of the bushing, the outer guide engaging the inward face of the bushing head; an interconnected and radially expansible weight assembly interposed between the two guides and including weights having radially outer cam faces, the inner guide having an annular cam portion engaged by the said cam faces when the motor is halle l, the weights liaving radially inner faces engaging the shank of the bushing when the motor is halted; and a compression spring continually urging the inner guide outwardly; the inner guide having an annular portion disposed for engaging the commutator when the inner guide is moved against the resistance of the spring.

Signed at Chicago, Illinois, July 22nd, 1927.

DONALD M. BLISS.

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