US2037457A - Silver faced slip ring - Google Patents

Description

4 April E. G. COLSON 2,0373157 SILVER FACED SLIP RING Filed Dec. 28, 1932 2 Sheets-Sheet 1 INVENTOR Eric 6. 60215072 BY %w% MZ 'ToRNEY April 14, 1936. E, LS 2,037,457

SILVER FACED SLIP RING Filed Dec. 28, 1932 2 Sheets-Sheet; 2

FNS ULIATION Z3 32 IN SULiATION INVENTOR TTORNEY Cal Patented Apr. 14, 1936 PATENT OFFICE SILVER FACED SLIP RING Eric G. (Jolson, New York, N. Y., assignor to Ford Instrument Company, Inc., Long Island City, N. 'Y., a corporation of New York Application December 28, 1932, Serial No. 649,143,

15 Claims.

'The present invention relates to slip rings of high conductivity with which brushes co-act in electricalapparatus whereby electrical circuits are well maintained through relatively movable elements. The inventive concept lies largely in the structure and method of making the slip ring, which has been devised to avoid serious defects that have been present in slip rings hitherto constructed to have intended high conductivity, but which has failed to attain this desirable quality. Such failure has resulted in slip rings which are formed mainly of base metal or alloy and which are provided with annular silver faces soldered thereto in such manner that the solder has been in contact with the silver faces. The solder has, in these instances, been found to penetrate and permeate the silver to such extent as to contaminate it and rob it of its normally high conductivity. Thus, the very purpose for which the silver faces were used on the slip rings has been defeated.

In silver faced slip rings of prior construction, the attachment of current-conducting leads thereto has been made with the aid of solder in such manner that the solder used for this purpose has also contacted with and, therefore, has permeated and contaminated the silver faces, still further depreciating the current conducting quality thereof. In other forms of slip rings of an earlier period, posts for the attachment of electrical conductors have had portions riveted to the slip rings with the rivet heads 'of these portions embedded in the band of silver which constituted .the silver face. A common fault in this type of construction is that the rivet heads are frequently not entirely flush with the exposed silver face, as they are intended to be. Consequently, sparking at and burning of the surface of the silver face of the slip ring occurs. An object of the present invention is to avoid the aforementioned defects and ill effects by a construction wherein the silver face of the slip ring is secured to a foundation annulus in a manner wherein no-solder comes into contact with the silver face so that the purity and high conductivity of the latter is maintained.

It is also an object to combine one or more terminal posts to the slip ring so that solder used toattach an electrical conductor to the terminal post cannot encounter the silver face of the slip ring and contaminate it.

Furthermore, by the improved construction, a smooth hard surface is given to the silver face, whereby it withstands'wear due to the pressure of a brush bearing against it over a long period of operation, and so that there is an absence of sparking between the brush and the silver face of the slip ring. v

Other features and advantages appearing hereinafter are, of course, to be understood as 5 forming part of the present invention.

In the drawings,

Fig. 1 is a sectional view, principally taken on the line Il, of Fig. 2, showing a plurality of silver faced slip rings of the improved type installed in an electrical step-by-step motor, parts being shown in elevation;

Fig. 2 is an end elevational view of the motor disclosing the slip rings in side view with brushes applied thereto, the bearing mounting the motor yoke being omitted for improved clearness;

Fig. 3 is an enlarged cross sectional view through one side of one of the slip rings, illustrating one mode of combining the silver face to the foundation ring;

Fig. 4 is an enlarged edge view of a portion of the novel slip ring, with a terminal post affixed thereto;

Fig. 5 is another enlarged fragmentary cross sectional view, taken substantially on the line 5-5, of Fig. 4, through one side of one of the slip rings, but at the point of attachment thereto of one of the terminal posts, portions of the latter being shown in elevation; and

Fig. 6 is an enlarged fragmentary cross sectional view of one side of a modified form of silver faced slip ring.

Referring to the drawings, l represents a portion of the yoke of an electric motor in which slip rings of the novel type disclosed herein are installed, while 2 indicates the end bell at the shown end of the motor, the end bell being secured to the motor yoke l by tap screws 3. The illustrated motoris of the step-by-step type in which the field yoke I and-the end bells 2 that are attached to the opposite ends of the yoke form a unitary metallic structure which is mounted at its opposite ends in ball bearings I so that the field structure as a whole may be turned, by unshown means, in accordance with required angular steps.

Integral with the end bell 2 is an inwardly directed annular flange 4, forming a socket 5 inset in which is a ball bearing 6, which, with a similar ball bearing at the opposite but unshown 5 end of the motor, mounted in similar manner, rotatably supports an armature shaft 1. Fast on the armature shaft is an armature 8, which is revoluble between the pole pieces (not shown) on which field coils 9 are mounted.

Formed as an integral part of the end bell 2 is another and outwardly extending annular flange I0 which forms apocket the inner end of which is of a slightly reduced diameter to form an annular seat for a circular base ll of insulating material. A sheet l2 of insulating material is interposed between the outer face of the end bell 2 and the inner face of the base ll of insulation and serves as a cover for certain recesses in the latter. An, appropriate number of screws l3 extend through the flat portion of the wall of the end hell 2 and the sheet of insulation [2, these screws being threaded into the insulation base I l to hold the same in place on the end bell 2.

In advance of the outer face of the insulation base II are a plurality of concentrically arranged slip rings l4, each of which is mounted on the insulation base H by means of a number of preferably cylindrical mounting studs I 5. Each stud l5 has a portion ii of reduced diameter which passes through and is conformed to a circular hole in the foundation ring ll of the slip ring. This hole is countersunk, and the end of the reduced portion l6 of the stud is upset to be conformedto and to fill the countersunk portion of the hole, thereby becoming a rivet head which rigidly holds the slip ring l4 against the shoulder formed by the main and reduced portions of the mounting stud l5. Screws l8 have their heads located in recesses in the inner side of the insulation base I I, the threaded shanks of the screws I8 being screwed into threaded holes in the mounting studs IS. The insulating sheet l2 shields the heads of the screws ill from the end bell 2 and prevents short-circuiting. Thus, the mounting studs l5 are securely mounted on the insulation base ll, and in turn hold the slip rings 14 in proper relation thereto and to themselves.

Suitably mounted on an insulating support, as a bar l9 of insulation, are brushes 20, each comprising a rigid metallic member 2| fastened to the insulation bar l9 by screws 22 and a flexible finger 23 riveted or otherwise combined with the rigid member 2|. The free end of the flexible finger 23 is preferably provided with a silver or silver-plated contact tip or button 24, which is urged by the spring-like quality of the flexible finger 23 into good electrical contact with the slip ring M with which it co-acts. A terminal clip 25 is attached by a screw 26 to the rigid member 2| of each brush 20, and has a bared portion of an electrical conductor 21 aflixed to it in the usual-manner. An insulating shield 28 is applied to the insulating bar l9 and projects between the slip rings l4 and the brushes 20.

The structure thus far described sets forth a typical installation of the novel slip rings in suitable electrical apparatus, and discloses certain parts of the invention, but other important features thereof remain to be described. Each slip ring I4 is formed in part of the foundation ring or annulus ll of any appropriate metal or alloy, such, for example, as brass. As shown in' Fig. 3, the outer and inner circumferential surfaces of the foundation ring I! are bevelled inwardly from the opposite edges of the vertical outside surface 29 of the' ring I! to an adequate extent for a purpose disclosed later, thereby forming an inwardly inclined face 30 and a circular shoulder 3| on each of the outer and inner circumferential surfaces of this ring. Extending from the shoulders A 3| these circumferential surfaces of the foundation ring I I are parallel as they extend to the vertical inside surface 32 of the ring H.

The vertical outside surface 29 and the inwardly inclined surfaces 30 of the outer and inner circumferential surfaces of the foundation ring I! are preferably silver-plated so as to constitute excellent electrical contact surfaces. An annular relatively thin piece of silver 33 of greater width than the circular outside surface 23 is applied to the latter and the marginal borders of the silver piece 33 are spun over to lie against the inwardly inclined surfaces 30 of the ring H. The process of applying the thin annular silver piece 33 to the foundation ring I! is such that the silver facing 33 is at all places in such thoroughly intimate contact with the enclosed portions of the foundation ring ll that the silver face 33 and the foundation ring l'l correspond, in effect, to'a unitary electrical current-conducting element.

During the application of the annular silver facing 33 to the foundation ring II, this silver face of the slip ring I4 is economically burnished by the spinning operation and at the same time it acquires a smooth, polished surface that is quite hard. Accordingly, there is an absence of sparking as the slip rings l4 revolve relatively to the brushes 20, and there is also resistance to wear whereby the slip rings have long life.

To provide a good path for electrical current between the slip rings l4 and the electrical means with which they turn, as the coils 9 of the motor field, terminal po,sts 34 are affixed to the slip rings, say, one to each slip ring, although any desired number of terminal posts may be secured to such ring. The attachment of the terminal post 34 to the slip 'ring I4 is made prior to the application of the silver facing 33 thereto so that circular continuity of smoothness of the silver face of the slip ring is maintained constant.

Reference to Fig. 5 shows that at the place of attachment of the terminal post 34 to the slip ring the brass foundation ring I! is provided with a hole extending from one vertical side to the other of the ring, which hole is countersunk from the outside vertical surface of that ring. The terminal post 34 is provided with a portion 35 of reduced diameter that extends in cylindrical form through the hole in the foundation ring I! and into the countersunk portion of this hole where it is converted into a frusto-conical head 36 that conforms to and substantially fills the countersunk portion of the hole. The shoulder 31 formed by the main and reduced cylindrical portions of the terminal post 33 is thus held tightly against the vertical inside surface 32 of the foundation ring l1, and the terminal post 34 is thus rigidly combined with the latter.

At its unattached end the terminal post 34 is provided with a saw-cut 38 of suitable width, in which is laid the bared end 39 of an electrical conductor 40. The saw-cut 38 is otherwise filled with solder 4| securely attaching the conductor 40 to the terminal post. As shown in Fig. 1, the conductor 40 goes to a field coil 3, of the motor, though in other electrical apparatus it may be connected to any current-conveying element.

From the preceding description it is clear that the silver face 33 is applied to and interlocked with the brass, or other, foundation ring I! without the use of solder, or any other fusible alloys, that would penetrate and contaminate the silver face, and consequently the silver forming the face of the slip ring is possessed of its maximum purity and high degree of conductivity. Also, the outer facing 33 and the foundation ring I! are combined with a silver to silver contact, and the attached end of the conductor." is secured to the the silver face 33 of the slip ring so that the silver face is not penetrated and contaminated by the solder 4| used to attach the bare end 39 of the conductor to the terminal post 34. If desired, the end of the conductor may be attached to the terminal post by mechanical fastening means. Moreover, the spun over marginal edges of the silver face 33 require the shoulders 3! of the foundation ring to be retracted from the brushengaged surface of the slip ringsufficiently to prevent any jumping of the electric current im mediately to the foundation ring H.

A modifiedform of the silver faced slip ring is shown in Fig. 6, wherein the silver' face 33' has reversely bevelled sides 30' that are inclined in the opposite directions to which the corresponding sides 30 of foundation ring ll of the first described form of slip ring are inclined. In the form of Fig. 6, the foundation ring ll of, say, brass, has an originally rectangular but subsequently bevelled groove 42, the groove-forming flanges 43 being forced inwardly to grip and retain the silver ring 33'. This arrangement has the virtue of being simple in construction but ordinarily requires the silver ring to be of greater thickness than the silver facing 33 of the form shown in the other views. Due to the convergence of the bevelled sides 30' toward the brushengaged surface of the silver ring 33', shown in Fig. 6, this surface is narrower and is suited to brushes of small contact area, While the surface 33 of the ring shown in cross section in Fig. 3 is wider and better adapted for engagement by comparatively wide brushes of rectangular cross section. In either form of slip ring, however, the silverfacing is securely affixed to the foundation ring with a dovetail construction, and Without the use of solder or other fusible alloys.

While the novel slip rings herein disclosed have been shown and described as being installed in one type of motor, it is to be understood that they maybe employed in other types of motors and, in fact, in any electrical apparatus wherein there are relatively rotatable parts between which an electrical connection, or connections, are required. Also, if desired, the silver facing may be applied to the outer circumferential surface of the foundation ring, instead of being affixed to a vertical side thereof, as in the illustrated form. This obvious alternative form would be the natural arrangement where a plurality of slip rings are arranged side by side, as in certain well-known types of dynamoelectric machines.

The herein described silver cup rings are simple and reliable in construction and service-giving qualities, as well as being relatively inexpensive to manufacture, and it is obvious that changes and alterations may be made in the particular form of construction of the slip ring without departing from the spirit of the invention as defined in the appended claims.

I claim:--

1. A slip ring comprising a metallic foundation ring, and a separate continuous current-conducting annular facing in immediate contact with an annular surface of said ring, part of the external surface of said facing forming an electrical contact surface, said ring and facing being formed to effect a dovetail connection between themselves.

2. A slip ring comprising a metallic foundation ring, and a separate continuous currentconducting annular facing in immediate contact with an annular surface of said ring, part of the external surface of said facing forming an electrical contact surface, said foundation ring and facing being formed as annular co-acting dovetail connection elements one of which has marginal flanges retentively bent over portions of the other.

3. A slip ring comprising a metallic foundation ring, having a portion thereof including an uninterrupted annular surface of said foundation ring formed as an annular dovetail member, and a continuous relatively thin annular facing of high electrical conductivity having an inner surface in electrical contact with said annular surextending over the annular dovetail-memberforming portion of said foundation ring in conformity to receding sides thereof.

5. A slip ring comprising a foundation ring having a portion thereof including an annular surface of said foundation ring formed as an annular dovetail member, the same being plated with metal of high electrical conductivity, and

a relatively thin annular facing of high electrical conductivity formed as a co-acting dovetail member lying in intimate contact with the plated portion of said foundation ring, said facing having marginal edges spun over opposite sides of the annular dovetail-member-forming portion of said foundation ring.

6. A slip ring comprising a metallic foundation ring and an electrifiable annular facing covering an annular surface of said foundation ring, one having portions bent over and completely exterior to opposite sides of the other, said portions extending inwardly toward each other so that the free ends of said portions are separated by an amount less than the width of said annular surface of said foundation ring, whereby said annular facing is held in electrifiable contact against said annular surface of said foundation ring.

7. A slip ring comprising a metallic foundation ring having an annular surface and opposite bevelled surfaces exterior to said ring and inclined inwardly from said annular surface forming an annular dovetail tongue, and a relatively thin silver annulus in continuous parallelism and intimate contact with said annular surface and having spun over marginal edges, said silver annulus and its said edges forming a dovetail groove receiving said dovetail tongue and constituting the means of attachment of said silver annulus to said foundation ring, the outer surface of said silver annulus being burnished and hardened.'

8. A slip ring comprising a foundation ring, a relatively thin silver facing in parallelism with an annular surface of said foundation ring and interlocked with the latter, and. a terminal post rigidly afflxed to said foundation ring and provided with electrical conductor attaching means removed from said silver facing.

9. The combination with electrical apparatus having a current conveying contact and an electrical conductor, of a slip ring engaged by said contact and comprising a foundation ring, a relatively thin facing of high electrical conductivity in parallelism with an annular surface of said foundation ring and interlocked with the latter, a terminal post rigidly aflixed to said foundation ring and provided with a recess removed from said foundation ring and facing in which recess a bare portion of said conductor lies, and a deposit of fusible metallic substance in said recess combining said conductor and terminal post.

10. The combination with electrical apparatus having relatively movable parts one of which carlies a current-conveying contact and the other of which is provided with electrifiable means and an electrical conductor connected therewith, of an insulating base mounted on the last named part, a slip ring mounted on said base and comprising a foundation ring and an annular facing of high electrical conductivity therefor interlocked therewith and engaged by said contact, a terminal post rigidly affixed to said foundation ring and provided with a recess away from said ring in which recess said conductor lies, and a fusible metallic substance in said recess combining said conductor and terminal post.

11. The combination with electrical apparatus having relatively-rotatable parts one of which carries a current-conveying contact and the other of which has electriflable means provided with a conductor and a member containing a pocket, of an insulating base mounted on said member in the pocket thereof, a slip ring mounted on said base and comprising a foundation ring and an annular facing of high electrical conductivity therefor interlocked therewith and engaged by said contact, a terminal post afiixed to said foundation ring recessed for and receiving said conductor, and a fusible metallic substance combining said conductor and terminal post.

mounting said slip rings on and insulating the same from said second named part, said slip rings individually comprising a foundation ring, an annular facing therefor of relatively high electrical conductivity interlocked therewith and engaged by one of said contacts, and terminal posts rigidly affixed to the respective foundation rings and provided with recesses remote from said facings, said conductors having terminal portions in said recesses combined with said posts by fusible metallic material.

13. In combination, an electrical conductor, a slip ring comprising a foundation ring provided with a hole therethrough expanded near an annular surface of said foundation ring, a relatively thin facing of high electrical conductivity in parallelism with and intimately engaging said annular surface, said facing being spun into interlocked relation with said foundation ring, a terminal post having a portion of reduced diameter extending through said hole and having a head fitting the expanded portion of said hole, said post having a recess at a point removed from said facing in which recess a part of said conductor lies, and a fusible alloy in said recess uniting said conductor and post.

14. A slip ring including a metallic foundation ring having a plurality of faces and a pair of annular recesses each of which is located between a pair of adjacent faces of the ring and is formed with an inwardly inclined face and a circular shoulder, and a metallic facing held in contact with the face of the ring located between the recesses by having the marginal portions of the facing in engagement with the inwardly inclined faces of the recesses.

15. A slip ring including a metallic foundation ring having a plurality of faces and a pair of annular recesses each of which is located between a pair of adjacent faces of the ring and has an inwardly beveled face and an annular shoulder and a metallic facing having its marginal portions in engagement with the inwardly beveled faces of the recesses, whereby the facing is held in contact with the face of the ring located between the recesses.

ERIC G. COL-SON.

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