US1898696A

US1898696A - Method of manufacturing commutator segments

Info

Publication number: US1898696A
Application number: US509577A
Authority: US
Inventors: Charles E Sorensen
Original assignee: Ford Motor Co
Current assignee: Ford Motor Co
Priority date: 1931-01-19
Filing date: 1931-01-19
Publication date: 1933-02-21
Anticipated expiration: 1950-02-21
Also published as: DE600822C; FR730554A; NL32506C; BE384849A; GB378253A

Description

V Feb. 21, 1933.

C. E. SORENSEN METHOD OF MANUFACTURING COMMUTATOR SEGMENTS Filed Jan. 19. 1931 Fig, Z.

2 Sheets-Sheet l INVENTOR.

A TTORNE Y.

Feb. 21, 1933.

c. E. SORENSEN METHOD OF MANUFACTURING GOMMUTATOR SEGMENTS Filed Jan. 19, 1931 2 Sheets-Sheet 2 I R Y @Q M 4% m o W 2 w- I 2A 1 l a Q 4 2 Ya 7.. 1 J .0,

Patented Feb. 21, 1933 UNITED STATES PATENT OFFICE CHARLES E. SORENSEN, OF DETROIT, MICHIGAN, ASSIGNOR TO FORD MOTOR COMPANY,

OF DEARIBORN, MICHIGAN, A CORPORATION OF DELAWARE METHOD OF MANUFACTURING GOMMU'IATOR SEGMENTS Application filed January 19, 1981.

invariably are composed of an annulus of copper segments, each of which is insulated from the rest and from the armature shaft to which the commutator is secured. These commutator segments consist of strips of copper each having a ring sector cross section. The segments are alternated with mica 1nsulating strips to form an annulus, the periphery of which is machined to a true circumference for the current carrying brushes to operate upon. That edge of each segment which goes to form the inside of the commutator ring is provided with a dovetailed portion or similar device for retaining the segment in place. In such commutators a relatively small number of segments are required so that there is a relatively large angle subtended by the sides of the segments, from which it may be seen that the thickness of each segment at its periphery is considerably greater than at its inside edge. lt 1s the purpose of this application to dlsclose a method whereby such tapered segments may be made at a much reduced cost from the cost heretofore required.

In all starting motor structures a lug extends radially from the inside end of each commutator segment to which the armature windings are secured. Usually radial slots are machined in these lugs in which two or more terminal wires from the armature windings are fastened. The armature windings of such starting motors are composed of copper bars of rectangular section, approximately inch thick and 1 5 inch wide, so that it will be seen that these lugs must extend a considerable height above the periphery or brush ring surface of the commutator in order that the slots receive these bars. It will further be seen that due to the great height required for these lugs, the thickness of their outer ends is two or more times that of the bottom or dovetailed portion of the Serial No. 509,577.

segment. Although this angularity or taper is not appreciable in the segments makin up large commutators, because of the great number of segments usually employed, it is nevertheless quite large and unavoidable in automobile starting motors and generators; and it is in the manufacture of the commutators used in such devices that my improved method is especially suited.

The former methods used to manufacture these segments has been to either machine the segments out of solid copper bar stock, which is a very costly and slow process, or else to roll tapered copper stock to a width equivalent to the distance between the bottom of the segment retaining dovetail and the top of the terminal lug. Such tapered stock is then fed through punch presses which stamp out the'required combined segments and terminal lugs. It will be seen that by this method the major portion of the copper stock is scrapped during the removal of the thick portion of the material to form the terminal lug. As this scrapped portion of the stock is at least twice as thick as the inside edge of the stock and extends the height of the lug and about ths of the length of the seg ment, the loss of material from this cause is very high.

According to my improved method the segments are formed from tapered stock having a width only as great as the depth of the segment'from the brush surface to the bottom of the retaining dovetail which is only about half that required with the former method. The material for the lug is taken from the stock itself which is cold-headed in suitable dies to thereby flow the metal outwardly, forming the terminal lug. An insignificant amount of stock is scrapped by this process which reduces the cost of such segments to only a fraction of their former cost.

A further object of my invention is to provide a segment substantially twice as thick as could be formed by the ordinary stamping method. Due to the relatively small number of segments required in starting motors and generators and the relatively large terminal bars which need to be secured to the lugs of each segment, the angular thickness of each segment is necessarily large. It is not commercially possible to stamp out such segments from a single piece of thick stock because the thickness of the lug is greater than its width and the metal, when such attempt is made, distorts or spreads out producing a segment having curved side walls. In order to overcome such disadvantage, these segments have been built up from two stampings placed side by side, each of which is punched from metal of only. half the thicknessaof the segment. With my improved method one piece segments of any desired thickness may be made to form a commutator having only half the number of parts formerly necessary. The assembly cost of commutators built according to my improved method is materially lessened, due to the reduced number of parts therein.

Still a further object of my invention is to provide a method of forming commutator segments whereby the metal thereof will be niaterially hardened incidental to the forming operations, to thus form a harder and consequently longer lived commutator; lhe copper stock used to form the conventional commutator segments must be rolled to size and the subsequent punching of the segments therefrom leaves the copper stock in its original soft condition. According to my process, I deform the structure of the segment sllil'iciently to produce a hard metal structure. Ordinarily the hard structure formed by such working is undesirable and subsequent annealing must be provided for, however, in this instance the hard structure is desirable inasmuch as it produces a segment having a much longer life than could formerly be provided. A commutator built up from such segments "forming a harder brush surface will, therefore, be an advantage.

Still a further object of this invention is to provide a method whereby two segments are formed in a die at one operation, which operation can be carried on in an automatic machine to thereby reduce the cost of these segments to an amount only slightly more than the actual cost of the copper used therein.

With these and other objects in View, my invention consists in the particular material and sequence of operations used according to my improved method, as described in the specification, claimed in my claims, and 111118- trated in the accompanying drawings, in which:

Figure 1 shows a perspective view of a commutator segment produced according to my improved method.

Figure 2 shows a perspective view of a pair of the segments, shown in Figure 1, illustrating the manner in which they are formed in airs. p Figure 3 shows a length of copper stock used to form the pair of segments, shown in Figure 2.

Figure 4 shows a perspective view of the stock used to form the sections, shown in Figure '3.

Figure 5 shows a perspective view of a commutator constructed from segments formed according to my improved method.

F igurefi shows a fragmentary central sectional view through a starting motor commutator illustrating the means whereby the segments are retained in position.

Figure 7 shows a side view of one of the dies used to form the segments.

Figure 8 shows a plan view of a set of dies. consisting of a heading die, cut-off die and one-half of the holding die, the heading die being withdrawn to illustrate the p\ 'lll()ll of the stock therein prior to the heading operation.

Figure 9 shows a plan view of the dies shown in Figure 8, the heading die being inserted to illustrate its cold-heading action in forming the terminal lugs of the segn'mnt.

Figure 10 shows a perspective view of the cut-off dies shown in Figure 8.

Figure 11 shows a diagrammatic view of the complete set of dies illustrating the positions wherein the stock is fed into the dies.

Figure 12 shows a diagrammatic view illustrating the positions wherein the cut-off die has been lowered to shear a length of the stock.

Figure 13 shows a diagrammatic view of the several dies with the heading die forced home to form the terminal lugs on the scgments.

Figure 14 shows a diagrammatic view of the dies in their separated positions, showing how the incoming stock ejects the headed pair of segments from the dies, and

Figure 15 shows a plan view of the ordinary commutator, illustrating the construction wherein two stampings were required to form a single segment of the required thickness and angularity.

Referringto the accompanying drawings. 1 have used the reference numeral 10 to indicate an armature shaft usually associated with automobile starting motors and generators. I have provided a sleeve 11 upon which is mounted a commutator 12. This commutator is built up from an annulus of copper commutator segments 13 having tapered cross sections as required from the size of the commutator and the number of segments therein. The inner edges of these segments are dovetailed, as at 14:, so that a pair of clamping collars 15, secured on the ends of the sleeve 11, may co-act with these dovetails to retain the ring of segments in place. Suitable insulation 16 of mica or other material is placed between the collars 15 and the dovetail and also between the indivdual segments to thereby insulate each segment from the remaining segments and from the arma- Pressed on one end of this shaft ture shaft. Terminal lugs 17 extend radiing equivalent to the total height of two of ally from the inner ends of the segments 13, the segments and lugs. The proportion of each of these lugs having a radial slot 18 this die is governed by the dimensions of the machined therein to receive the ends of a required commutator segment and may be 5 pair of conductor bars 19 from the armature varied to the various sizes of commutator 7 windings. These windings consist of relasegments. The die block 2-l may be built tively heavycopper bars which are pressed up from two halves, if desired, so that the into the slots and then soldered in place to slots therein may be conveniently machined form a. permanent electrical connection with and the two halves secured together.

10 the particular commutator segment. A heading die 27, having a cross section 75 To assemble such a commutator the reof the same as the slot 26, is adapted to required number of segments, alternated with ciprocate in this slot to form the lugs of strips of insulation, are placed in an annular the commutator. I have also provided a cutcontracting die and contracted together to off die 28, which is mounted to reciprocate form a true annulus. The sleeve 11 is then transversely to the slot which cut-01f die 8 inserted and the collars 15, with the necesis provided with a slot 29 extending theresary insulation rings, are forced into the through of the same cross section as the slot grooves formed by the dovetailed portions 25 with which it is normally aligned. The and the ends of the sleeve flattened down to die 28 is provided with an integral lug 30 thereby prevent the withdrawal of the col projecting into a complementary shaped 85 lars. The commutator is then removed from groove 31 in the die block which lug and the die and the periphery given a light finishgroove extend through the center of the ing cut to thereby provide a smooth surface slot and projects perpcndicularly therefor the motor brushes to operate upon. The to. The contour of the lug and groove slots 18 are then machined in the segments 31 is determined by the recess 32 as and the device assembled on the armature shown in Figure 2, and retuired to form shaft. the outer half of the dovetails on each pair Referring to Figures 2 through 4, I desire of commutator segments. The die block to roll the copper material from which the 24 is held in a heading machine having a pair 30 commutator segments are to be made in the of slides reciprocating at right angles to each form of a strip 20 having a width just twice other and the heading die 27 is secured to one that of the depth of the segment between of these slides while the cut-off die 28 is se-' its brush face and the bottom of the dovetail cured to the other.

14. This strip is flat on one side with its Referring to Figures 11 through 14,1 have 35 center portion on the opposite side considerprovided a pair of feeding rollers 33 which ably thinner than the edges thereof, these are driven and timed to intermittently force dimensions being governed by the taper of the stock 20 into the slot 29 in the cut-oft die. the segments to be formed. It will be noted The dies are located in the machine with the that with such stock two segments are formed

slots

25 and 29 aligned when the machine is 40 sideby side; however, if desired, stock half at the end of its stroke at which time the 106 this width may be used thereby forming only feeding rollers 33 then push the stock through one segment at a time. these aligned slots until it strikes the end of The procedure according to my improved the die 2'4". As shown in Figure 12, the die method is to first cut off a length of the stock, 28 is then reciprocated downwardly which- 45 as shown at 21 in Figure 3, and While holdshears off the length 21 from the stock 20. 110

ing this length in a die the leading end is WVhile the die 28 is still in this lowered posispread out to form a blank 22, as shown in tion, the heading die 27 is driven forwardly Figure 2. That portion of the blank 22 outinto the slot 26 thereby deforming the length lined by the dotted lines 23 is then punched of stock 21 therein by forcing the metal into 50 out and the blank sheared along its center the inner end of the slot 26, as illustrated in line to form a pair of segments, as illustrated Figure 13. The die 27 is not driven to the in Figure 1. It will be seen that the only bottom of the slot 26 but the end of the die atloss of stock through this method is in the the completion of the stroke is spaced thereforming of one-half of the dovetailed retainfrom sufficiently to form the lugs 17 on the 55 ing member. As this portion of the segment segments. is relatively thin, only a very small portion The heading die is then withdrawn and r of the stock is scrapped through this method. the cut-otf die returned to its upper position --The dies and equipment by which my whereby the stock 20 may again be fed into method We carrierlwnsists of a die the machine thereby extruding the finished 60 block 24 having a transverse SlOtQdQ-Xtfi'lfl: blank 22 from the dies. as shoivnjnEiwurc ing therethrough, this slot being of a cross H TThe'die2"kis'thenmglginto its startsection equivalent to the cross section of ing position wherebv the portion of the stock the stock 20. The slot 25 is enlarged for within the die is accurately sized for len th about half the distance through the die block, and the foregoing operation repeated. The

65 as shown at 26, the width of the slot 26 be recesses 32 are then punched out and. the

blanks sheared along their center line thereby forming a pair of completed segments from each blank. It will be seen that these segments can he very rapidly formed by such method and, as the operations of the machine are entirely automatic and as very little stock is scrapped, the cost of producing these segments is only very slightly more than that of the copper material used.

Referring to Figure 15, the ordinary commutator is shown. The terminal lugs which extend from each segment may be seen to have a relatively great angular width. In the ordinary method of stamping out such segments the thickness of the stock was limited so that each of such connnntator segments had to be made from two stampings placed side by side. In my improved process, the terminal lugs can readily he formed having a greater angular width than their thickness so that only one member is required for each segment. This feature reduces the assembly costand forms a better commutator.

Among the man f advantages arising from the use oi my improved method, it may be well to mention that by this process I am able to form an improved connnutator at only a fraction of the cost required formerly. This reduction is partially accomplished by the reduced labor cost,however, the practical elimination of waste stock, which waste has heretofore been unavoidable, contributes mainly to the lessened cost of this method.

A further advantage arises because the work done in forming the lugs materially increases the hardness of the copper so that when such hardened segments are formed into a commutator a much longer lived device results. Motors or generators equipped with such commutators should not require the dressing on of the commutator because of brush wear during the life of the vehicle upon which it is used.

Some changes may be made in the equipment used and sequence of operations which constitute my improved method without departing from the spirit of my invention, and it is my intention to cover by my claims such changes as may reasonably be included within the scope thereof.

I claim as my invention:

1. The method of simnltanemlsly forming a pair of connnutator segments of wedge shaped cross section tlnroughout their lengths each having a dovetailed retaining portion at its thin edge and a. terminal lug extending oppositely from its thick edge, consisting of transversely shearing a strip of metal into lengths, said strip being thin at its center and thick at its edges, the line of shear forming one end of each of said dovetails. then upsetting the opposite. end of said blank to form a pair of oppositely extending terminal lugs projecting from the sides ol said blank, then forming the remaining segments.

ends of the dovetails, and then shearing the blank along its center line to form said pair of segments.

2. 'lhe method of simultaneously forming a pair of commutator segments of wedge shaped cross section each having a dovetailed retaining portion at its thin edge and a terminal lug extending oppositely from its thick edge, consisting of upsetting one end of a strip of rolled stock to form a pair of oppositely extending terminal lugs, said strip having .a cross section thicker at its edges than at its center, then stamping away a portion of the center of said stock to form one end of the pair of dovetails, and then shearing said stock along its center line.

3. The method of simultaneously forming a pair of commutator bars each having a dovetailed retaining portion at one of its edges and each having a terminal lug extending oppositely from its other edge, consisting of upsetting one end of a strip of rolled stock to form a. pair of oppositely extending terminal lugs, then shearing said strip transversely to form a detached section of the stock, said transverse line of shear l'orming one end of a pair of dovetails, then stamping away a portion at the center of said detached section atthe opposite end thereof to form the remaining ends of said dovetails, and then shearing said section along its center line to form said pair of commutator bars.

4. The method of simultaneously forming a pair of commutator segments of wedgeshapcd cross section each having a terminal lug extending outwardly from its thick edge, consisting of upsetting one end of a strip of rolled stock to form a pair of oppositely extending terminal lugs, said strip having a cross section thicker at its edges than at its center, then shearing said strip lengthwise through its center to thereby form said pair of con'nnutator segments.

5. The method of simultaneously forming a pair of commutator segments of wedgeshaped cross section each having a dovetailed retaining portion at its thin edge and a terminal lug extending oppositely from its thick edge, consisting of upsetting one, end of a strip of rolled stock to form a pair of oppositely extending terminal lugs, said strip having a cross section thicker at its edges than at its center, then shearing said strip transversely to form detached sections, the line of said transverse shear forming one end of each ofsa-id dovetails, and then shearing said detached portions lengthwise through their centers to thereby form said CHARLES E. SORENSEN.