US3085951A - Method of making slip ring-commutator devices - Google Patents

Description

April 16, 1963 e. P. BENTLEY ETAL 3,085,951

METHOD OF MAKING SLIP RING-LCOMMUTATOR DEVICES Original Filed June 11, 1957 2 Sheets-Sheet 1 Fig.1

INVENTORS GEORGE P. BENTLEY GEORGE C. McNABB EDWARD L. LEWIS Fig-4 April 16, 1963 G. P. BENTLEY ETAL METHOD OF MAKING SLIP RING-COMMUTATOR DEVICES 2 Sheets-Sheet 2 Original Filed June 11, 1957 Fig.7

INVENTORS: GEORGE P. BENTLEY GEORGE C.MCNABB EDWARD L. LEWIS THEIR ATTORNEYS States nite The invention in this application, which is a division of application Serial No. 665, 021, now Patent 2,918,542, relates to a method of making slip ring-commutator devices.

An object of the invention is to provide a method of making compact and rugged commutating devices particularly suited for use in high speed rotary switching devices.

Another object of the invention is in the provision of a method of making integrated slip ring-commutator assembles which permits of division of commutator segments with dividing head accuracy.

Another object of the invention is in the provision of a method of making integrated slip ring-commutator assembles having long electrical leakage paths between commutator segments.

Another object of the invention is in the provision of a method of making slip ring commutator devices having in line cylindrical commutating surfaces whereby phase errors due to brush width variations are eliminated.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings in which like reference numerals designate like parts throughout the figures thereof and wherein:

FIGURE 1 is a plan view of an assembled slip ringcommutator device;

FIGURE 2 is a top view of an assembled slip ringcornmuntator device;

FIGURE 3 is a fragmentary perspective view of a commutator ring before separation of the segments;

FIGURE 4 is a cross sectional view taken along lines 44 of FIGURE 1;

FIGURE 5 is a view in section through the commutator assembly prior to machining to separate the cornmutator segments;

FIGURE 6 is a view in section through the commutator following machining to separate the commutator segments and expose the inserts to enable them to be removed by electrolytic etching;

FIGURE 7 is a view in section taken through one side of the slip ring; and

FIGURE 8 is a view in section taken through one side of the outer retaining ring of the commutator slip ring device.

Referring now to the drawings wherein like reference characters designate like or corresponding parts throughout the several views, and particularly to FIGURES 3, 4, 7 and 8, the slip ring-commutator construction comprises a slip ring 12, a commutator ring 13, and an outer retaining ring 14. The slip ring comprises an annular body portion 15 having annular flanges 16 and 17 extending axially from diametrically opposite sides of the body portion flush with the top and bottom surfaces of the body portion. Flange 16 is relatively thinner than flange 17 and is radially slotted about its periphery.

The commutator ring 13 preferably formed of rhodium comprises as most clearly seen in FIGURE 3 an annular 3,fl85,951 Patented Apr. 16., 1963 body portion 18 having first and second annular flanges 19 and 20 extending axially from opposite sides of the body portion flush with the bottom surface thereof, and third and fourth annular flanges 22 and 23 extending axially from opposite sides of the body portion flush with the top surface thereof. As seen in FIGURE 3 the third flange 22 is longer than the fourth flange 23. Both the third and fourth flanges are further provided at their ends with radially extending annular flanges 24 and 25 thereby forming an annular channel in the outer surface of the commutator ring. The commutator ring is thereafter provided with equally spaced stepped radial slots 27 (FIG- URES 1 and 3) about its periphery from the channelled top surface down into the first and second flanges, the number of slots depending on the number of segments desired for a particular application. It is to be noted that the radial distances to the inner peripheries of both the slip ring and commutator ring are equivalent.

The outer retaining ring 14 (FIGURE 8) comprises an annular body portion 28 which has an axially extending flange 29 extending from one side flush with the bottom thereof, and a relatively long axially extending flange 30 extending from the same side as flange 29 and flush with the top surface thereof. As seen in FIGURE 1, which illustrates as specific embodiment, the upper flange 30 is provided with equally peripherally spaced axially extending grooves 32, one of which has a substantially cutout portion 33, and with a plurality of similar relatively narrow indexing or alignment reference grooves 34. Additionally the body portion 28 is provided with a plurality of holes 35 about its circular face which in combination with a potting compound provides strength and rigidity to the assembled wafer.

In assembly the slip ring 12 is placed adjacent the commutator ring 13 with the flange 16 thereof overlapping the first flange 19 of the commutator ring and maintained spaced therefrom by .a separator ring 36 (FIGURE 5) formed of an electrochemically active metal such as aluminum. Electrochemically active keys 37 are also placed within the narrow portion of each of the stepped radial slots 27 for reasons Which will hereinafter appear. Insulated lead wires 38 are secured as by soldering to predetermined ones of the segments 39 formed by said slots in the commutator ring and a lead wire 46* to the slip ring. The lead wires 38 and 40 are then caused to lie flat in the annular channel 26 in the outer surface of the commutator ring. The outer retainer ring 14 is then placed with its long flange 30 over both the slip ring and commutator ring and with its flange 29 between the second and fourth flanges 26 and 23 of the commutator ring; the lead wires being brought out through the cutaway groove 33 (FIGURES 2 and 5). The rings disposed with respect to each other as described above are held in a suitable jig and a plotting compound 42 of insulating material such as an epoxy resin whose coeflicient of thermal expansion matches that of the metal parts is poured into and fills all the slots in and spaces around and between the intermeshing flanges of the rings and the wide portion of the stepped slots 27 between segments whereby the assembly becomes an integrated annular wafer of great strength and rigidity. The resulting wafer is disclosed in FIGURE 5.

Thereafter the wafer is placed on a lathe and the inner surfaces of the slip ring and commutator ring (shown dotted in FIGURE 4) are turned down until the bottom of the radial slots 27 (FIGURE 3), which extend down into the lower flanged body portion of the commutator ring are reached (line 43) thereby dividing the commutator ring into individual segments insulated from one another and exposing inner edges of the keys 37 as shown in FIGURE 6. Thereafter the remainder of aluminum insert 35 separating the slip ring and commutator ring and the keys 37 within the narrow portion of the stepped radial slots 27 are electrochemically etched away to provide undercut segments as shown in FIGURE 4. As is apparent, the contact surfaces of the segments are cylindrical sections thereby permitting accurate timing.

The above method permits division of the commutator segments 39 from one another with dividing head accuracy as they are an integral part of the retaining ring 14 during embedment. The above method which is termed double slotting" provides a commutator having long electrical leakage paths between segments with concomitant high intersegment resistances. The leads 38 which as heretofore stated are brought out through one grooved section of the retaining ring flange as shown in FIGURE 2 are adapted when the ring or rings are assembled within a cylindrical casing to lie within the groove 32 thereof as seen in the assembled view of FIGURES l and 2.

It should be understood, that the foregoing disclosure relates to only a preferred embodiment of the invention and that it is intended to cover all changes and modifications of the example of the invention herein chosen for the purposes of the disclosure, which do not constitute departures from the spirit and scope of the invention.

The invention claimed is:

1. The method of making annulated wafer like commutators having first and second rings of equivalent internal diameters, said first ring having an annular body portion, first and second flanges extending axially from diametrically opposite sides of and flush with the radially outer and radially inner surfaces thereof, said second ring having a body portion, first and second flanges extending axially from opposite sides of and flush with the radially inner surface thereof, third and fourth flanges extending axially from opposite sides of and flush with the radially outer surface thereof and fifth and sixth flanges extending radially from and flush with the ends of said third and fourth flanges, said method comprising the steps of, forming slots in said second ring, said slots extending inwardly from the radially outer surface of said second ring and having inner ends spaced from the radially inner surface of said second ring, inserting electrochemically active metal keys in said slots adjacent to said inner ends, placing said first and second rings adjacent one another with said second flange of the first ring overlying and spaced from said first flange of said second ring, filling the spaces between said intermeshing rings with an insulating potting material, radially boring said radially inner surface of said second ring through to the slots thereby dividing said second ring into a plurality of radial segments and exposing said keys therebetween, and thereafter electrochemically etching away said keys to provide separate, undercut segments.

2. The method of making slip ring-commutator wafers having a slip ring and a commutator ring of equivalent internal diameter, said rings having irregular cross sections, said method comprising the steps of forming substantially radially extending slots in said commutator ring extending inwardly from its outer periphery, said slots having inner ends spaced outwardly from the inner periphery of said commutator ring to form a plurality of segments joined together by an inner peripheral annular web, inserting electrochemically active metal keys in said inner ends of said slots, placing said rings adjacent one another with their cross sections spaced from and overlapping each other, filling said spaces between said rings and segments with a potting compound to secure said rings and segments together and electrically insulate them from one another, cutting away said web to separate said segments from each other and expose said keys and thereafter etching away said keys to provide undercut segments.

3. The method of making commutators comprising the steps of cutting stepped radial slots in the outer periphery of a cylindrical ring, said slots having inner ends spaced from the inner periphery of said ring, inserting electrochemically active metal keys in said inner ends of said slots, filling the remainder of said slots with a bonding insulating material, boring out the internal surface of said slotted ring to expose said inner ends of said slots and said keys therein to separate said ring into segments, and thereafter electrochemically etching away said keys to provide undercut segments.

4. A method of making commutators comprising forming stepped slots of progressively narrower width extending from one side of a metallic commutator ring toward an opposite side thereof, said slots having closed ends spaced substantially equal distances from said opposite side of said ring, inserting keys in said slots adjacent to the closed ends thereof, the remaining portions of said slots being open, filling the open portions of said slots with, and at least partially embedding said ring in, a bonding insulating material, cutting away said ring from said opposite side to said closed ends of said slots to divide said ring into a plurality of separate segments and expose a portion of each key therebweteen, and thereafter removing said keys from between said segments.

References Cited in the file of this patent UNITED STATES PATENTS 1,195,861 Smith Aug. 22, 1916 1,624,597 Heathcote Apr. 12, 1927 1,845,115 Apple Feb. 16, 1932 2,156,156 Mahlck Apr. 25, 1939 2,936,519 Blackman May 17, 1960

Claims (1)

1. THE METHOD OF MAKING ANNULATED WAFER LIKE COMMUTATORS HAVING FIRST AND SECOND RINGS OF EQUIVALENT INTERNAL DIAMETERS, SAID FIRST RING HAVING AN ANNULAR BODY PORTION, FIRST AND SECOND FLANGES, EXTENDING AXIALLY FROM DIAMETRICALLY OPPOSITE SIDES OF AND FLUSH WITH THE RADIALLY OUTER AND RADIALLY INNER SURFACES THEREOF, SAID SECOND RING HAVING A BODY PORTION, FIRST AND SECOND FLANGES EXTENDING AXIALLY FROM OPPOSITE SIDES OF AND FLUSH WITH THE RADIALLY INNER SURFACE THEREOF, THIRD AND FOURTH FLANGES EXTENDING AXIALLY FROM OPPOSITE SIDES OF FLUSH WITH THE RADIALLY OUTER SURFACE THEREOF AND FIFTH AND SIXTH FLANGES EXTENDING RADIALLY FROM AND FLUSH WITH THE ENDS OF SAID THIRD AD FOURTH FLANGES, SAID METHOD COMPRISING THE STEPS OF, FORMING SLOTS IN SAID SECOND RING, SAID SLOTS EXTENDING INWARDLY FROM THE RADIALLY OUTER SURFACE OF SAID SECOND RING AND HAVING INNER ENDS SPACED FROM THE RADIALLY INNER SURFACE OF SAID SECOND RING, INSERTING ELECTROCHEMICALLY ACTIVE METAL KEYS IN SAID SLOTS ADJACENT TO SAID INNER ENDS, PLACING SAID FIRST AND SECOND RINGS ADJACENT ONE ANOTHER WITH SAID SECOND FLANGE OF THE FIRST RING OVERLYING AND SPACED FROM SAID FIRST FLANGE OF SAID SECOND RING, FILLING THE SPACES BETWEEN SAID INTERMESHING RINGS WITH AN INSULATING POTTING MATERIAL, RADIALLY BORING SAID RADIALLY INNER SURFACES OF SAID SECOND RING THROUGH TO THE SLOTS THEREBY DIVIDING SAID SECOND RING INTO A PLURALITY OF RADIAL SEGMENTS AND EXPOSING SAID KEYS THEREBETWEEN AND THEREAFTER ELECTROCHEMICALLY ETCHING AWAY SAID KEYS TO PROVIDE SEPARATE, UNDERCUT SEGMENTS.

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