US1654776A

US1654776A - Short-circuiting device

Info

Publication number: US1654776A
Application number: US54456A
Authority: US
Inventors: Edwin C Ballman
Original assignee: Individual
Current assignee: Individual
Priority date: 1925-09-04
Filing date: 1925-09-04
Publication date: 1928-01-03
Anticipated expiration: 1945-01-03

Description

Jan. 3, 1928.

E. C. BALLMAN SHORT CIRCUITING DEVICE Filed Sept. 4, 1925 Patented Jan. 3, 1928.

UNITED STATES EDWIN o. B LLMAN. or s'r. LOUIS, MISSOURI.

SHORT-CIRCUITING DEVICE.

Application filed September This invention pertains to electric motors and more partlcularly to a device for short circuiting the commutator as is done in the starting operation of many types of commutator motors. I

The customary manner of short circuiting a commutator involves the use of a series of contactors, usually operated by centrifugal force, and arranged to contact with the com mutator segments at a predetermined motor speed. These cont actors connect the various commutator segments with a short circuiting ring. At the instant at which the commutator is short circuited there is usually a heavy rush of current through the contactors. This'current must pass through the point of contact between the contactor and the commutator segment. The usual experience has been that considerable arcing takes place at these points of contact. After numerous operations theeffect of such arcing is to cause the commutator segments and the contactors' to become rough, so that a good contactis no longer possible. Accordingly the eifectiveness of the short circuit is impaired when such roughening or corrosion of the contact points takes place.

One of the objects of this inventionflcherefore, is to "provide a short circuiting device of novel construction which will obviate the trouble due to corrosionof the contact points.

Another object is to provide an auxiliary set of contactors whichwill accomplish the make and break operations so that the main contaotors will be relieved of the arcing.

Another object is to provide such a device which will be simple and economical to main ufactu're and reliable in service.

Further objects will appear from the following description taken in connection with the accompanying drawing in which:

Figure 1.is a view partly in section of a commutator equipped with a short circuiting device embodying this invention;

Figure 2 is a partial end view of Figure 1; and

Figures 3 and 4 are detail views illustrating the action of the contactors.

Referring to the accompanying drawing 1 designates the motor shaft which may have mounted thereon in any suitable manner a commutator hub 2, carrying commutator segments 3. This maybe of any ordinary construction well known in the art. Mounted on the shaft 1 just in front of the commutator is a metallic cup 4. This should be 4,'-1925. Serial no; 54,456.

made of a material having high electrical conductivlty such as brass or copper. The cup 4 is adapted not only to provide a mounting for the short circuiting contactors as will 7 presently be described, but also acts as a short circuit ring to carry the inter-change of currents between said contactors.

Pivoted in the ring 4 are two series of contactors, a series of main contactors 5 and a series of auxiliary contactors 6. These contactors are formed by punching, or other suitable operation, of wedge shaped copper or brass similar-to that used for commutator segments. shown in Figures 1, 3 and 4 comprising a lever portion 7; a tail piece 8, a sharply angled point 9, slightly rounded to form a p vot, a weight or body portion 10 and contacting faces 11 and 12. As will be seen from Figure 3 the main and auxiliary contactors are identical in form except for the contacting portions, that of the auxiliary contacts 6 being longer than that'of the main contacts 5 so that the contacting face 12 of each auxiliary contactor will extend beyond the contacting faces11 or the main contactors.

,Such construction provides that the auxiliary contactors will make contact in advance of and break contact after the main contactors.

The c-ontactors are mounted in the ring 4 In such a way that the pivots 9 of the contactors fit into the corner at the bottom of the rim 13 of said'ring. The contactors are assembled close together all around the cup 4 as shown in Figure 2, there being approximately three main to one auxiliary contactor. This mounting provides that each contactor will have a pivot at its corner 9 in the cup 4. A pressure plate 14 of .circular form and fitting over the shaft 1 so as to slide therealong engages the tail pieces of all of the contactors and is pressed thereagainst by acoil spring 15 surrounding the shaft 1.- This plate operates to'press the contactors into the cup 4; so that their tail pieces 8 will all be forced down against the rim'of the cup so as to maintain their con tactfaces clear of the commutator as shown in Figure 3;

The assembled contactors are protected by a cup shaped cover 16 mounted on the shaft 1 and having a flange 17 extending over the contactors and toward the commutator.

The contactors have the form The 1 half ring sections 18 fitting into an annula groove 19 in the shaft 1 and each is provided with an inwardly projecting car 20 extending through a notch .21 in the cover 16. The spring 15 bears at one end against the inte rior of the cover and at its other end against the pressure plate 14: so that this sprin not only provides pressure for retracting the contactors from engagca'ient with the commutator but also serves to re tain the cover 16 in locking engagement with the sections 18, which not. only hold the cover 16 in place but are themselves retained in place thereby.

in the operation of this device, when the motor is at rest, the contactors assume the positions illustrated in Figure 3. lVhen the motor is started and attains a predetermined speed the centrifugal force of the body portions 10 of the contactors, acting through the lever portions 7 and the tail pieces 8 overcomes the pressure of the plate 14. hen this takes place the contactors turn on the pivots 9 so as to bring the contacting faces 12 and 11 into engagement with the commutator segments 3. The auxiliary contactors make contact first at their faces 12 and the arcing takes place at these contacts. Subsequently as the motor speed increases further, the main. contacts engage the con'in'iutator segments at their faces 11. \Vhen this point has been reached the contactors are in the positions illustrated in Figure 1. Here both series of contactors are in engagement with the commutator. However, the tail pieces 8 of the main cont actors have pushed the pressure plate 14 outwardly so as to free the tail pieces of the auxiliary contactors 6 as illustrated in Figure 1. The further action of centrifugal force on the auxiliary contaetor will now move them in such a Way that the pivot point 9 slides outwardly along the rim 13 until the tail pieces again engage the plate 14. This position is shown in Figure 1 During this movement the auxiliary contactors have a slight rocking motion at their contact faces 12 so that a varying contact is obtained at this point which assists in reducing the corrosion due to arcing. It will further be noted that the contact faces 11 and 12 are displaced radially with respect to one another. Accordingly they will engage the commutator at different parts thereon. This provides that the arcing at the face 12 will occur at a different point on the COlIlll'lUllZl-tOl than that engaged by the faces 11.

It will be seen, therefore, that in accordance with this invention a short circuiting device is provided in which the arcing is confined to a series of auxiliary contactors and to a certain place on the commutator segments, while the main short circuiting operation is accomplished by the main contactors which touch the commutator at a point which is not engaged by the auxiliary contactors and which is, therefore, kept clean and uncorroded by arcing. The auxiliary contacts engage the segments With a slight rolling or slipping engagement so that the roughness produced by arcing will be correspondingly reduced. As the contactors are not confined circumferentially nor limited to any fixed position, the continued operation of this device will shift the contactors circumferei'itially with re spect to the commutator so that the corrosion due to arcing will be distributed over the entire circumference of the con'nnutator and not confined to any one point.

'ilie device is very chetp to manufacture. it contactor may be formed by punching from sliitable metal. The cup 4, the plate 1 1, the cover 16 and the sections 18 may each be made oi suitable sheet metal formed at a single machine operation, and therefore, very cheap. The spring 15 is subject to only slight moven'oent upon operation of the contactors and, therefore, its change in strength due to conipressfon will be slight while the contactors move radially outwardly, thereby ii'icreasing the force which they exert upon the spring. Accordingly the contactors will move positively against the spring tension, an action which is desirable in order to avoid excessive arcing. The cover 16 provides protection for the device while at the same time aflording easy access thereto.

This construction also provides for easy accessibility, as the device is easily disassembled by simply pushing in the cover 16 to free the sections 18 which are then removed. and the cover slipped back on the shaft. This releases the spring 15 and the plate let so as to render all the contactors accessible for removal or replacement. The contactors are thus easily removable for cleaning the contacting surface of the commutator.

It is obvious that various changes may be made in the details of construction Without departing from the spirit of this invention; it is to be understood, therefore, that this invention is not to be limited to the specific details shown and described.

Having thus descirbed the invention what is claimed is:

1. In an electric motor, a short-circuiting device, comprising, a commutator, a series of main contactors adapted to make contact with the commutator segments, and a series of auxiliary contactors adapted to make contact with the commutator se 'inents in advance of said main contactors.

2. In an electric motor, a short-circuiting device, comprising, a commutator having segments, a series of main contactors centrifugally operated to contact with said segments at a predetermined motor speed and a series of auxiliary contactors centrifugally trifugally operated to contact with said segments at a predetermined motor speed and a series of auxiliary contactors centrifugally operated to contact with said segments at a difierent place on the commutator from said main contacts.

l. In an electric motor, a short-circuiting device comprising, a commutator having segments, a series of main contactors and a series of auxiliary contactors centrifugally operated to contact with said segments at a predetermined motor speed, said main and auxiliary contactors having their contacting portions relatively displaced.

5. In an electric motor, a short dircuiting device, comprising, a commutator having segments, a series of main contactors centrifugally operated to contact with said segments at a predetermined motor speed and a series of auxiliary contactors centrifugally operated to contact with said segments and to disengage said segments after said main contactors.

6. In an electric motor, ashort-circuiting device, comprising, a commutator having segments, a series of main contactors centrifugally operated to contact with said segments at a predetermined motor speed and a series of auxiliary contactors centrifugally operated to contact with said segments in advance of said main contactors and with a varying contact.

7. In an electric motor, a sliort-circuiting device, comprising a commutator having segments, a .series of main contactors and a series of auxiliary contactors cent-rifugally operated to contact with said segments at a predetermined motor speed, a cover for said contactors, locking means for retainin said cover in place, said locking means being adapted to be retained by said cover, and resilient means for retaining said cover in engagement with said locking means.

8. In an electric motor, a short-circuiting device, comprising, a commutator having segments, a series of main contactors and a series of auxiliary contactors centrifugally operated to contact with said segments at a predetermined motor speed, a spring for restraining said contactors against the centrifugal force thereof, a cover for said contactors, and a loose locking element adapted to retain said cover and to be retained by said spring.

In testimony whereof I afiix my signature this 21st day of April 1925.

EDI/VIN C. BALLMAN.