US2843830A - Slip ring and brush assembly - Google Patents

Description

' y 1958 L. c. BQLAND'ING 2,843,830

' SLIP RING AND BRUSH ASSEMBLY Filed Nov. 2, 1953 2 Sheets-Sheetl 5 Lax i INSULH T/OA/ l IN V EN TOR.

Zea/20rd GB/mzdi/z July 15, 1958 L. c. BLANDING SLIP RING AND BRUSH ASSEMBLY 2 Sheets-Sheet 2 Filed Nov. 2, 1953 Ill d I lltlllII-lllllllll... llllllllll A I M INVENTOR. Leonard C. Blending United States SLIP RING AND BRUSH ASSEMBLY Leonard C. Blanding, Grand Rapids, Mich, assignor to Lear, Incorporated, Grand Rapids, Mich.

This invention relates to a slip ring and brush assembly of the subminiature type wherein absolutely minimum friction and mass are important desiderata.

Many present day gyroscopic instruments, e. g. as used aboard aircraft in connection with horizon indicators and automatic pilots, involve the conduction of current between two or more relatively rotatable parts, and under circumstances where the use of flexible conductors is contra-indicated. To provide the electrical connection various forms of miniature slip ring and brush assemblies have been devised, and in nearly all of these conventional practice has been followed. However, the generally known assemblies do not lend themselves well to miniaturization and therefore by using such constructions a lower dimensional limit is reached which is still far removed from the desired situation.

I have found that by using a novel form of slip ring and brush, forming the substance of the present invention, it is possible to provide a group of thirty-two independently connected slip rings having a diameter of 0.140 and a length of 0.960" or an average space occupancy per ring axially of 0.030 or close to inch.

Accordingly, the principal object of the invention resides in providing a subminiature slip ring and brush assembly having dimensions substantially less than similar assemblies heretofore known, hence less inertia and lower friction torque.

Another object lies in providing an assembly as aforesaid in which the slip ring portion may be assembled with the brush unit without the hazard of damaging any of the brushes.

A further object resides in providing means for positive alignment of a brush with the ring individual thereto.

Still another object is to provide a subminiature slip ring and brush assembly which, notwithstanding the congested arrangement of parts is easily accessible for wiring up in accordance with ordinary practice, and readily mounted on its supports.

Other objects will become apparent from the accompanying description and drawings in which latter:

Fig. 1 shows the assembly with the brush portion sectioned longitudinally;

Fig. 2 shows an end elevation viewed from the left of Fig. 1;

Fig. 3 is a cross section taken on the line 3-3 of Fig. 1;

Fig. 4 is a partial cross section taken on the line 4-4 of Fig 3;

Fig. 5 is a detail of a portion of a brush and its connecting lead;

Pig. 6 shows an endelevation of one of the brush supports; and

Fig. 7 is a partial cross section taken on the line 7-7 of Fig. 6.

In considering the description and the drawings it is believed that a fuller appreciation of the scope of the invention will be had if the thought prevails that the important features of the invention take on their form stem 0 f 2,843,83d Patented July 15, 1%58 because of the extremely small dimensions involved. Put another way, a typical embodiment of the invention utilizes a slip ring assembly of 32 rings approximately /s diameter and 1 long, and an exterior diameter of the brush assembly of approximately Either the brush assembly or the slip ring assembly may constitute the single rotating part, or both parts may rotate, depending upon the application. Preferably, the slip ring assembly is made the rotating part because of possible adverse effects of centrifugal force or momen' turn, or, in the case of both parts rotating, the slip ring assembly is preferably the part having the lower velocity. A typical instrument to which the improvement of the invention may be applicable is disclosed in U. S. Letters Patent No. 2,595,951.

The slip ring assembly may, in general, take any of several well known forms which may lend themselves to sub-miniature organizations, and therefore as such form no part of the invention. Accordingly, a suitable assembly is indicated somewhat schematically in the several views as 10 comprising slip rings 7 and insulating material 3 therebetween, and is carried on a flange or hub 11 secured in any convenient manner to the parent part 12. However, notwithstanding the broad disclosure of the assembly 10 the free end 14 thereof is: preferably cylindro-ogival for a purpose to be explained.

The brush assembly (Fig. 1) in the example shown, comprises a cylindrical shell 21 of metal having an internal shoulder 22 at one end and another shoulder 23 at the other, and which latter is preferably the result of swaging or spinning over a portion of the shell following the insertion of the brush units 25 which will secure the same firmly within the shell.

Referring to Figs. 1 and 3 particularly, each brush unit 25 comprises an electrically-insulating annular body 26 including the circular aperture 27 and a cylindrical recess 28. The marginal portion of the body 26 is perforated by a plurality of equally spaced bores 29 equal in number to the maximum number of brushes to which the invention lends itself, in this instance 36 in number. As will appear, the diameter of each bore 29 is related to the size of the conductor to be threaded therethrough and to the size of the base circle upon which the bores are located. Obviously a larger conductor, therefore, will yield less holes for the same diameter of base circle. At least one aperture, here shown as 2911 opens directly into the recess 28 by means of a V-shaped cutout 32 (Fig. 6).

Each of the brushes 41 is arranged for wiping action on two diametrically opposite points of a slip ring to provide balanced tension between the two arms of the brush and, secondarily, to insure, in case of damage or error in manufacture, that at least one arm will have contact. Thus, a brush comprises resilient wire, e. g. Phosphor bronze including two parts 42 and 43 (Figs. 4 and 5) soldered together, as at 44. Preferably the adjoining elements of the parts 42 and 43 are left unsoldered over a short distance, such as X, to afford freedom of torsion about the axis of each wire as the brush arms are flexed in assembly and use. Each part 42 and 43 includes, in the confines of the recess 28, an arm or finger 46-46 so proportioned as to result in each thereof being tangent to the associated slip ring at the ends of a diameter, although such precise considcration is not essential. It will be observed that the portions of each part 42 and 43 joining the finger 46 to the axially-extending portions cliverge slightly in the vicinity of the cut-out 32 in order to permit flexing movement thereof, and to limit the minimum spaced position of the fingers 46. Stated otherwise, upon withdrawal of the slip ring assembly the tension of the brushes will urge them to assume a position indicated by the outer set of dotted lines, and as limited by a pair of projections 5151 extending from the floor of the recess 28. Obviously it is desirable to maintain the fingers 46-46 sufliciently far apart to permit the nose 14, upon re-assembly, to pass between the fingers 46 without risk of deformation thereof.

As will now be apparent each brush is provided with an individual one of the bores 29 for passage of its related parts 42 and 43 (Fig. 4). Clearance for the brush fingers is afforded within the recess 28.

One of the important advantages of the invention resides in the integration of the brush and its conductor. Accordingly, parts 4344 are carried around an electrically insulating layer 61, e. g. plastic compositon, formed on a flange 62 extending from the cylinder 21. Supplemental anchorage of the layer 61 may be accomplished by providing apertures 64 in the flange 62 and molding the composition therewithin as shown. As part of the molding operation aforesaid a plurality of terminal lugs 67 of U-form may be included and thereby rigidly carried on the flange 62 and simultaneously electrically insulated. Following preparation of the brush support including the terminal lug 67 each part or conductor 43 may be wound around and soldered to one of the legs of a lug, and the leg thereafter bent over as additional security. The leads,

such as 71, from the component to which a brush relates may be similarly soldered and anchored to the other leg of the terminal lug.

Although the flange 62 is shown in the example as frusto-conical this is only for considerations involved in a particular application. However, it is essential, in a subminiature assembly to fan the leads radially (Fig. 2) to provide working clearance at the lugs 67.

It will have become clear that the invention lends itself ideally to units having one or a large number of brushes. Each brush and its associated holder 25 is an independent subassembly. For example, the cylinder or housing 21 may be simply decreased or increased in length in accordance with the number of brush units or, if a standard length of cylinder 21 appears to be desirable from a manufacturing or inventory standpoint holders 25 may be utilized as dummies.

For clarity Figs. 1 and 2 show only a single conductor representing the pair of conductors 43 and 44.

By virtue of the minimal dimensions achieved in the instant construction the assembly may be readily fitted within the bearing of a gimbal joint, and space-consuming protrusion exteriorly of the joint thereby avoided.

While I have shown a particular embodiment of my invention, it will be understood, of course, that I do not wish to be limited thereto since many modifications may be made, and I therefore contemplate by the appended claims to cover any such modifications as fall within the true spirit and scope of my invention.

I claim: p

1. A slip ring and brush assembly comprising a slip rlng arbor, a plurality of slip rings carried on said arbor and having active faces flush therewith, means at one end of said arbor for rotatably supporting the same, the opposite end of said arbor having a tapered nose, an equal plurality of electrically-insulating brush housings of hollow, cylindrical form and a casing for supporting said housings in face-to-face relation, each housing having an annular recess in one radially-disposed, flat face thereof and the central opening of each holder being of greater diameter than the rings, a brush individual to each housing located in said recess for wiping on an associated slip ring, each brush including a pair of fingers for tangential contact with the ring substantially at the opposite ends of a diameter thereof, an axially-extending conductor for each brush, and said holders as a group having aperture means for passage of said conductors, said brush being radially resilient and having, in the absence of the slip ring, a relaxed position within the area of said central opening and, in the presence of the slip ring, an operative position substantially outside the area of said opening, said recess providing a guide for radial movement of the brush but restraining the brush against appreciable movement axially whereby the slip ring arbor may be moved axially into and out of operative relation with the brushes without damage thereto.

2. A brush assembly in accordance with claim 1 wherein said aperture means comprises a plurality of bores distributed around the end face portion of a holder surrounding the recess therein, the bores of all holders being in alignment and each aligned plurality receiving the conductor of a single brush.

3. A brush assembly in accordance with claim 1 wherein each said brush comprises two resilient wire members each formed to provide a said finger and cojoined over a common portion of each to provide a unitary brush, one of said portions being extended to provide a conductor for connecting said brush to the electrical component with which the brush is associated.

4. A slip ring and brush assembly comprising an arbor having a plurality of axially spaced-apart slip rings, a cylindrical sleeve having a radially-extending flange at one end thereof, a like plurality of hollow, cylindrical brush holders retained in said sleeve in face-to-face relation, each said holder having an annular recess in one radially disposed face thereof providing an annular space with the abutting holder, a bifurcated resilient wire member positioned in each said space, the furcations whereof are so formed and tensioned as to bear on opposite sides of the slip ring associated with the brush, said arbor having a tapered end for facilitating assembly of the arbor within the group of brushes, said end being constructed and arranged to pass between said furcations and to separate them without injury, each brush being provided with a projection at the junction of the furcations, extending perpendicularly to the plane of the brush, each said holder having an aperture for receiving said projection to prevent rotation of a brush on the axis of the holder, a conductor joined to said projection, each said holder having a plurality of axially extending aligned bores for passage of said conductors, said conductors terminating at a common end of said sleeve and said sleeve being provided with a radially extending flange at one end thereof, a layer of electrically insulating material on the outer face of said flange, a plurality of U-shaped terminal lugs secured in said layer by imbedment of the bight of the U and the legs thereof protruding outwardly of said layer, the terminus of each conductor being connected to one leg and the several other legs serving for connection of the external, incoming conductors.

References Cited in the file of this patent UNITED STATES PATENTS Sweden June 20, 1944

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