US3704513A - Method of manufacturing rotating commutators, particularly adapted for automatic machine assembly - Google Patents

Abstract

A continuous strip of conductive material, for example copper, bronze, aluminum or the like is provided having, in alternate sections, the cross-sectional shape of commutator segments (channel-shaped, T-shaped, L-shaped, C-shaped), and rod-like connecting strips, preferably half, or less the thickness of the commutator segments. A ring-shaped mold is provided, having segmental steel inserts separated by separator strips of blued steel; the steel inserts form guide ways for the segments, which are pushed in, severed at the far end of the connecting strip, and the mold is then indexed to the next guide way position accepting a commutator segment from the continuous strip. The commutator ring is then secured together by molding plastic in the spaces between the commutator segments, as known, or are otherwise locked together for example by means of insulating spacer shims inserted between the segments, and the mold pressed together.

Description

United States Patent Coquard [S4] METHODOF MANUFACTURING ROTATING COMMUTATORS, PARTICULARLY ADAPTED FOR AUTOMATIC MACHINE ASSEMBLY [72] Inventor: Lucien Coquard, Asnieres, France [73] Assignee: Societe Industrielle de Travaux Electro-Mecaniques (S.I.T.E.M.)

221 Filed: May 14, 1970 21 Appl.No.:37,277

6/1968 Noris ..'...29/597 [451 Dec. 5, 1972 Primary Examiner-Charles W. Lanham Assistant Examiner-Carl E. Hall Attorney- Flynn & Frishauf [57 ABSTRACT A continuous strip of conductive material, for example copper, bronze, aluminum or the like is provided having, in alternate sections, the cross-sectional shape of commutator segments (channel-shaped, T-shaped, L-shaped, C-shaped), and rod-like connecting strips, preferably half, or less the thickness of the commutator segments. A ring-shaped mold is provided, having segmental steel inserts separated by separator strips of blued steel; the steel inserts form guide ways for the segments, which are pushed in, severed at the far end of the connecting strip, and the mold is then indexed to the next guide way position accepting a commutator segment from the continuous strip. The commutator ring is then secured together by molding plastic in the spaces between the commutator segments, as known, or are otherwise locked together for example by means of insulating spacer shims inserted between the segments, and the mold pressed together.

8 Claims, 6 Drawing Figures PATENTEDnEc 5 I972 3,704,513,

SHEET 3 BF 3 ma'rnon or MANUFACTURING ROTATING CQMMUTATORS, PARTICULARLY ADAPTED roa AUTOMATIC MACHINE ASSEMBLY commutators for dynamo-electric machines of small size, such as commutators having an overall diameter of 4 centimeters, or less, although the method is applicable to commutators of all sizes." I

Ordinarily, commutators. of dynamo-electric machines consist of a circular assembly of copper, or other electrically conductive strips, insulated from each other and secured to a ring shaped carrier. The commutator segments are, in accordance with one method of their manufacture, first cut to have, in the longitudinal direction of the commutator, the profile desired for assembly. The width' of the strips corresponds to an angle of 360, divided by' the number of commutator segments, less the width of one insulating gap. The commutator segments are assembled in a circle, separated one from the other by insulating strips, for example mica or the like. Thereafter, the entire assembly is rigidly secured together, for example by rings, clamps, or other locking arrangements; they may also be secured by connecting them together in aplastic molding material. Collectors which utilize plastic molding material may be assembled without first inserting the insulating spacers, since the plastic molding material can be injected to fill in the gap between the collector segments. The commutator is then assembled to the shaft of the dynamo-electric machine'and later connected to the windings of the rotor. Connection to the windings of the rotor is by terminals which may have the form of taps, pigtail extensions, loops for insertion of wires from a rotor, or other structure to be commutated, or the like.

Commutators of this type are made in large quantities, and it is desirable to completely automate their manufacture. Simulating the hand assembly of commutators is not, however, suitable since mechanical apparatus to grasp the collector segments and placing them on a mounting ringis cumbersome, particularly when small commutators are involved. Furthermore, in the final method steps, complicated and easily maladjusted equipment is necessary in order to provide terminal elements to connect the collector to other circuit components, for example the windings of a rotor.

It is an object of the present invention toprovide a method, and apparatus and sub-assembly components to carry out the method to manufacture, automatically, commutators, and more particularly commutators which are molded and which further provide terminal elements such as lugs, loops, or the like for connection to other electrical components, for example rotor windings.

Subject matter of the present invention Briefly, a continuous strip of material is formed having, in alternate sections, the cross-sectional shape, and length of commutator segments, and connectingstrips which preferably are rod-like, that is of square or circular cross-section, and of half or less the thickness of the commutator segments. This continuous strip of alternate commutator and connecting strip sectionsis fed towards a fixture which is in the form of an open ring and has, at its innersurface, locating dividers forming locating arrangements to locate commutator segments. The commutator segments are pushed, in proper l0cation, into the mold and a cutter then cuts off the connecting strips close to, or flush with the beginning of the next adjacent commutator segments, the cutter simultaneously forming the connecting strip to form a terminal end, or lug, for example in ring shape, for connection to electrical components, such as the windings of a rotor. The moldisthen indexed to the next subsequent commutator position, and the process repeated. When the entire mold is filled with commutator segments, it is placed in a plastic molding injection apparatus, of known and customary type, for example supplied with a mandrel, to mold the commutator segments into a ring-commutator forassembly on a shaft; or, the mold can be directly placed over an already assembled rotor shaft and the commutator molded directly on theshaft of a dynamo-electric machine.

If desired, divider strips may be inserted between the commutator segments; this, also, can be dome automatically, the feed of the continuous strip of commuta tor and connection strip material, and the insulating strips being synchronized.

In accordance with a feature of the invention, a strip of material is provided which in alternate sections provides the commutator segments and the connecting strips.

In accordance with another feature of the invention, a mold or die is provided which is ring-shaped and contains therein sector-shaped inserts of generally trapezoidal cross-section, with the parallel sides of the trapezoid being rounded to match the curvature of the corn: mutator, the sections being divided by thin plates of blued steels, spring steel, or the like which project slightly beyond the segmental, trapezoidal pieces, to form guide ways for insertion of the commutator segments. These pieces are easily machined and manufactured, in substantial quantities and in various sizes to provide molds which, themselves, are inexpensive, so that a large number of commutators can inexpensively be made. i a

The invention will be described by way of example with reference to the accompanying drawings, wherein:

I FIG. 1 illustrates various shapes of commutator elements, in end views;

FIG. 2 is a perspective view of a continuous strip of commutator segments and connecting strips;

FIG. 3 is a fragmentary, perspective view showing insertion of commutator segments and an assembled segment with a formed terminal loop;

FIGS. 4 and 5 are fragmentary schematic side views, partly in cross-section, illustrating sequential steps in insertion commutator segments, forming of terminal strips, and severing of individual segment-strip elements;

FIG. 6 is a fragmentary end view illustrating one type of die or mold for use in the process.

Any type of commutator may be made in accordance with the present invention. It is, however, particularly applicable to high-volume production for small commutators of the molded type, having a diameter in the order of 4 centimeters (about I% inch) or less and having 20, or less individual commutator segments. The shape of the commutator segments is left to the choice of the designer of the commutator, and may have any desired shape, several customary and well known shapes being shown in FIG. 1 at a (arc-shaped); b (T-shaped); c (Id-shaped); and d (C-shaped). Each of these shapes has a profile which has a rounded outer partially cylindrical surface to match the circle of rotation of the commutator. The outer part of the collector segment is approximately trapezoidal in cross-section, followed by a converging region which, in element c of FIG. I may be defined by the next adjacent commutator segment, so that the base of the particular commutator segment will be smaller than the outside so that the segments themselves will be securely held and locked together by plastic material molded therearound. The segments themselves can be separated either by the molded plastic material, by additional separating strips, or by both.

In accordance with the present invention, the collector segments which may have any one of the shapes of FIG. I are formed as a continuous strip of material of copper, or' any other commutator material which, alternately, is followed by a connecting strip or lesser cross-sectional size, as best seen in FIG. 3. The entire assembly band, or strip, with the connecting strips shown exaggerated, is seen in FIG. 2, where the collector segments 1 are interconnected by connecting strips 2. The interconnecting strips should be of such crosssectionthat they can readily be severed by a cutter, a punch, or similar element, and they may be in rod-like form, round, rectangular or square in cross-section and preferably with a cross-sectional size half, or less than the thickness of the outer portion of the collector segments. Their length is, preferably, equal to, or less than the length of a collector segment. Manufacture of such strips is simple, requires only small stocking or storage areas and can readily be stored in coil form, for winding off a-turret, or in long longitudinal strips.

FIG. 3 illustrates the insertion of commutator segments. A jig, in form of a mold 4 is provided which has guide ways 3, separated from each other by ridges 5. The guide ways 3 form guides for positioning of the commutator segments I, pushed between the ridges 5. Ridges 5 provide for spacing of the collector segments,

so that insulating material can flow therearound to separate the collector segments and insulate them from each other. The number of the guide ways is equal to the number of the commutator segments. The height of the separating ridges 5 is as small as consistent with good positioning, in view of manufacturing processing speed, that is just sufficient to hold the commutator segments in place, and leaving the major extent of the space between the commutator segments free for placement of resin during molding of the commutator.

Collector segment I, seen pushed in position, abuts a reinforcement ring 6 at the inner end of the ring-shaped jig, or fixture 4. After positioning a commutator segmerit, as seen in FIG. 3, the connecting strip 2 is cut just at, and preferably flush with the end of the next succeeding commutator segment to be placed in position. During, or after the cutting, the connecting strip is shaped to form a terminal; it may be split, or, if sufficiently long, bent over a small projecting ring 8 formed on fixture 4, to form a terminal loop 7. During the cutting operation, the connecting strip 2 may e given any desired shape or form; rather than being formed into a loop, or split for a pinch connection, the connecting strip may be entirely cut, it may be angled off, left as a straight lug, or be given any other form.

After assembling all the commutator segments, the die is put into a molding press in order to seal and lock the commutator segments by a plastic resin, in accordance with known manufacturing processes. A mandrel may be used if the commutator is formed separately, bearings can be molded inside of the commutator, or the commutator can be molded directly on a shaft.

The exterior surface of the mold 4 is preferably conical, so that it can readily be centered in a holder, and afterwards in a molding press. FIGS. 4 and 5 illustrate sequential steps in the process of automatically manufacturing a commutator. A table 10 supports a continuous strip of commutator segments, separated by the connecting strips 2. The mold 4, only a portion of the interior of which is shown in FIGS. 4 and 5, is aligned with an injection opening on table 10, the mold 4 being held in a conical holder 13 which can be indexed circumferentially. A pusher 11 pushes a segment into the mold 4, until the commutator segment strikes abutment ring 6. Cutter 12 then moves downwardly, cutting connecting strip 2 and simultaneously forming it to be bent over the ridge 8 (see FIG. 5). The cutter, and the ridge 8, can be shaped to provide a different form of terminal end. Thereafter, the cutter will retract, holder 13 index by one circumferential position, push element 11, having retracted during the cutting operation, will advance the strip of material forming the commutator segments and connecting strips to be inserted in the next, indexed position mold 4. Alignment of the mold with the insertion motion of strip 1, 2, is simple.

The mold itself can readily be manufactured, with inserts which can be changed to accommodate different commutators, of different sizes and having different numbers of elements. As seen in FIG. 6, a ring-shaped holder 14 has located therein inserts, the end view of which is generally trapeze-shaped, with rounded sides, and made, for example, of steel. The inserts 16 are separated from each other by divider strips 15, for example of blue steel, spring steel, or the like, extending slightly beyond the outline of units 16 shown exaggerated in FIG. 6. The space between inserts 15 then forms the guide way, positioning the commutator seg ments. The angle of the converging sides of unit 16 is approximately equal to 360 divided by the number of commutator segments to be assembled; the insert and separator strips 15 are usually so thin, in comparison to the width of units 16, that they can be parallel.

The invention has been described in connection with assembly of a commutator in which the individual commutator segments are separated and insulated from each other by molded material. It is, of course, equally possible to insert manually, or automatically, insulating strips between the commutator segments themselves. These insulator strips can be inserted simultaneously, or subsequent to the insertion of the commutator segments themselves (FIGS. 4 and 5) at the same, or a different insertion station and in a similar manner, being cut off, however, flush with the commutator by a knife manna MI '1 passing only to the depth of the commutator segments, or extending therebeyond, as desired by the designer of the commutator. Such insulating strips may be of mica, insulating board or other material. To lock the assembly together, the group of assembled commutator segments can be then be placed in a ring which is slightly smaller than that of the assembly ring 4, so that the commutator will form one unitary whole.

Claims: 1. Method of manufacturing rotating commutators having a plurality of commutator segments secured together, particularly adapted for automatic machine assembly comprising forming a continuous strip of material having spaced, repetitive segments formed in the cross-sectional shape, and length of the commutator segments (1) and connecting strips (2) connecting adjacent ones of said segments,

providing a mold (4) in ring form having an internal opening corresponding approximately to the final outer diameter of the commutator, the inner opening of said mold being formed with locating means for placing and retaining commutator segments in said mold, and defining commutator segment positions;

inserting one of said segments (1) forming part of said continuous strip into said mold and in position to be retained by said locating means;

severing the connecting strip (2) attached to the inserted segment at its junction with a subsequent commutator segment;

indexing said mold by one commutator segment position;

repeating said inserting, separating, and indexing steps until all commutator segment positions in the mold are filled with commutator segments to assemble the segments into a complete array of commutator segments;

and securing said assembled segments in position relative to each other.

2. Method according to claim ll, wherein said securing step includes the step of injecting a moldable plastic substance in the mold with said segments located therein to fit said segments in position while simultaneously insulating said segments from each other.

3. Method according to claim ll, including the step of deforming the connecting strip into a bent-over portion while severing'the strip from a subsequent commutator segment.

4. Method according to claim 3, wherein the deforming step comprises the step of forming the connecting strip into a loop.

5. Method according to claim 1, including the step of inserting an insulating divider strip adjacent said com mutator segment.

6. Method according to claim 1, including the step of inserting, after assembly of said segments into said mold, insulating divided strips between said segments;

and transferring said assembled segments, with said insulating strips therebetween, into a mold of smaller size than said first-assembly mold to lock said elements together.

7. Method according to claim 1, wherein said insertion step includes the step of aligning a commutator position in a predetermined line;

and feeding said commutator segment and connecting strip into the mold along said line to locate said segment into the mold;

and said indexing step comprises indexing said mold to a commutator position not yet filled by a commutator segment.

8. Method according to claim 1, wherein said locating means comprises ridges (5) formed internally of the mold and spaced approximately by the width of a commutator segment and leaving between the ridges an open way to form said commutator position receiving a commutator segment, the ridges having a thickness corresponding to the spacing of said commutator segments.

Claims (8)

1. Method of manufacturing rotating commutators having a plurality of commutator segments secured together, particularly adapted for automatic machine assembly comprising forming a continuous strip of material having spaced, repetitive segments formed in the cross-sectional shape, and length of the commutator segments (1) and connecting strips (2) connecting adjacent ones of said segments; providing a mold (4) in ring form having an internal opening corresponding approximately to the final outer diameter of the commutator, the inner opening of said mold being formed with locating mEans for placing and retaining commutator segments in said mold, and defining commutator segment positions; inserting one of said segments (1) forming part of said continuous strip into said mold and in position to be retained by said locating means; severing the connecting strip (2) attached to the inserted segment at its junction with a subsequent commutator segment; indexing said mold by one commutator segment position; repeating said inserting, separating, and indexing steps until all commutator segment positions in the mold are filled with commutator segments to assemble the segments into a complete array of commutator segments; and securing said assembled segments in position relative to each other.

2. Method according to claim 1, wherein said securing step includes the step of injecting a moldable plastic substance in the mold with said segments located therein to fit said segments in position while simultaneously insulating said segments from each other.

3. Method according to claim 1, including the step of deforming the connecting strip into a bent-over portion while severing the strip from a subsequent commutator segment.

4. Method according to claim 3, wherein the deforming step comprises the step of forming the connecting strip into a loop.

5. Method according to claim 1, including the step of inserting an insulating divider strip adjacent said commutator segment.

6. Method according to claim 1, including the step of inserting, after assembly of said segments into said mold, insulating divided strips between said segments; and transferring said assembled segments, with said insulating strips therebetween, into a mold of smaller size than said first assembly mold to lock said elements together.

7. Method according to claim 1, wherein said insertion step includes the step of aligning a commutator position in a predetermined line; and feeding said commutator segment and connecting strip into the mold along said line to locate said segment into the mold; and said indexing step comprises indexing said mold to a commutator position not yet filled by a commutator segment.

8. Method according to claim 1, wherein said locating means comprises ridges (5) formed internally of the mold and spaced approximately by the width of a commutator segment and leaving between the ridges an open way to form said commutator position receiving a commutator segment, the ridges having a thickness corresponding to the spacing of said commutator segments.

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