US2694952A - Manufacture of commutator bars - Google Patents

Description

Nov. 23, 1954 c. CLEVENGER MANUFACTURE OF COMMUTATOR BARS 2 Sheets-Sheet 1 Filed Aug. 29, 1950 Nov. 23; 1954 c. CLEVENGER MANUFACTURE OF COMMUTATOR BARS Filed Aug. 29, 1950 2 Sheets-Sheet 2 9&2! v Ef /f United States Patent "ice lVlANUFACTURE OF CGNIMUTATOR BARS Carl L. Clevenger, Anderson, Ind., assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Application August 29, 1950, Serial No. 182,012

1 Claim. (Cl. 78-60) This invention relates to the manufacture of commutator bars having dove-tail tangs and its object is to provide a method and apparatus for producing them economically without waste of material. To accomplish this object, I provide for use with a two-blow header apparatus comprising a die-holder adapted to be attached to a fixed part of the header, a die supported by the holder and having an opening for receiving two segments of bar stock of keystone cross section and to locate them in definitely spaced, parallel relation with their thinner edges facing one another, the segment receiving opening in the die being bounded by surfaces which are engageable respectively with the thicker edges of the segments and with the side surfaces thereof to prevent separation of the segments and to prevent thickening thereof, punches of cross sectional contour adapting them to be received by the die and having tang forming end surfaces between which the material of the segments between their thicker edges is squeezed and is caused to flow into the space between the segments, the material of one segment flowing toward the material of the other segment and into contact therewith whereby the displaced material is caused to conform to the tang shaping surfaces of the punches, one of the punches being supported by the die holder for movement of the operating end thereof from a position near the inner end of the die to a position beyond the outer end of the die to eject the formed commutator bars, said punch being aligned, when the die holder is mounted on the header, with the ejector rod of the header which operates to effect said movement of said punch, and a holder for the other punch adapted to be mounted on the header slide which the header ram supports for movement laterally of the slide-supported punch, said slide being operated by the header to align the slide-supported punch in alignment with the die and the ram being operated by the header to move the punch into the die to cause the segments to be squeezed by said punch against the holdersupported punch.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings wherein a preferred embodiment of the present invention is clearly shown.

in the drawings:

Fig. l is a longitudinal sectional view of the header operated apparatus in open position preparatory to receiving two segments of bar stock.

Figs. 2, 3 and 4 are views similar to Fig. 1 showing the steps of forming the pieces in the commutator bars.

Fig. 5 is a fragmentary sectional view on line 55 of Fig. 1.

Fig. 6 is a view in the direction of arrow 6 of Fig. 1.

Fig. 7 is a view in the direction of arrow 7 of Fig. 1.

Fig. 7a is a fragmentary detail view of plate 54.

Fig. 8, like the succeeding figures is drawn to a larger scale than Figs. 1 to S and is a sectional view on line 8-8 of Fig. 1.

Fig. 9 is a sectional View on line 99 of Fig. 1.

Fig. 10 is a sectional view on line lil1tl of Fig. 1.

Fig. ll is a sectional View on line ll.11 of Fig. 1.

Figs. 12 and 13 are respectively plan and end views of a member which guides bar stock into the header.

Figs. 14 and 15 are respectively side and end views of a segment of bar stock before forming.

a commutator bar formed by the machine.

2,624,952 Patented Nov. 23, 1954 Referring to Fig. l, the header with which the described apparatus is used provides a fixed support 20 and a movable slide 21 carried by the header ram (not shown) which the header mechanism causes, twice in one cycle, to advance toward and retract from the support 20. Between reciprocations of the ram, the header causes the slide to move transversely of ram movement to cause punches carried by the slide 21 to be successively aligned with a die attached to the support 20. A die-holder block 22 attached to the support 20 provides a guide for a sleeve 23 retained by a pin 24 which, as shown in Fig. 5, is received by a groove 25 of the sleeve 23 so that sleeve 23 may have movement relative to block 22. Sleeve 23 supports a die 26 which is made in four parts comprising two parts 27 (Fig. 10) and two parts 28 which are assembled together and which provide, when assembled, a tapering exterior surface adapted to fit into a tapered bore in the sleeve 23 whereby when they are forced into the sleeve 23 they are retained in assembled relation. As shown in Fig. 10, the die holder block 22 is made in two parts 22a and 2212 which are secured together. The space 29 between parts 27 receive forming punches to be described.

A forming punch 30 received in space 29 is fixed at one end by rivets 31 (Fig. 8) to two cylindrical segments 32 which are received within a bore 33 of support 20 which receives also an ejecting rod 34 which is operated in one direction by the header mechanism to eject the formed bars. As viewed in Fig. 1 the movement imparted by the header mechanism to the rod 34 is upwardly and motion of the rod 34 in the opposite direction is effected by movement of the punch 39.

Referring to Fig. 9 punch 30 is received between semicylindrical segments 35 which together provide a bushing 36 (Fig. 1) having a flange 37 and received by a sleeve 38 which is guided by the block 22. The block 22 encloses a spring 39 located between sleeves 23 and 38 which urges these parts respectively against stop pin 24 (Fig. 5) and fixed support 20.

Referring to Figs. 1 and 6 the slide 21 carries a punch holder plate 40 attached thereto by studs 41 and nuts 42. Plate 49 carries a bushing 43 comprising halves 43a and 43b assembled by screws 44 with a pusher bar 45 having the same cross sectional contour as punch 30 whereby bar 45 can be received in the space 29 in the die 26. Plate 40 carries a bushing 46 comprising halves 46a and 46b assembled by screws 47 with a punch 48 as shown in Fig. 11. To provide clearance for the bar 45 and the punch 43 the block 22 is provided with recesses 49 and 50 respectively.

The block 22 and also the support 20, as indicated in Figs. 7, 12 and 13, support a guide 51 made in two parts 51a and 51b and providing cylindrical holes 52 into which bar stock is fed by the stock feeding mechanism of the header, said bar stock being guided into holes 53 of keystone cross-sectional contour. This feeding mechanism moves the bar stock through the holes 53 and against a fixed stop (not shown) spaced a distance from the surface 51s of the guide 51 equal to the length required for making the commutator bar. The ends of the bar stock lie between the edge of a plate 54 and retaining clips 55 secured to the plate 54. The header includes mechanism (not shown) for moving the plate 54 upwardly, as seen in Fig. 7, and during this movement the edge of such plate cooperates with the end suface 51s of the guide 51 to shear of? segments S (Figs. 14 and 15) of a length suitable for making commutator bars.

After these segments S have been sheared, the upward movement of plate 54 continues until the segments are moved to a position in alignment with recess 29 (Fig. 10) of the die 26.

The slide 21 is caused to move from the position shown in Fig. l to that shown in Fig. 2 to cause bar 45 to push the segments S into the die 26 and against the punch 30 which can then move only from the position shown in Fig. l to that shown in Fig. 2 due to the fact that the ejector rod operating mechanism of the header has then retracted to a position such that the rod 34 can move only from the position shown in Fig. l to that shown in Fig. 2.

Therefore the segments S are caused to be shaped by the punch 30 as shown in Fig. 2.

The slide 21 is then retracted from the position shown in Fig. 2 to that shown in Fig. 1; and then is moved laterally to the left to align the pusher bar 45 with recess 49 of block'22 and to align the punch 48 with the punch 30. Then the slide 21 moves into the position shown in Fig. 3 to cause the segments to be formed into commutator bars B. During this final step of bar formation each bar B is provided with a dove-tail tang t (Fig. 16). The deformation of the segments S to form these tangs causes material of the segments to be forced against one another with pressures that are substantially equal and opposite so that the strain on the punches is minimized. This deformation causes the segments 13, which are confined by the die 26 so as to prevent appreciable separation thereof and increase of thickness thereof, to press on the die 26 and thereby to create considerable frictional resistance to movement of the segments relative to the die 26. Therefore, during movements of the segments S with respect to the punch 30 for a distance substantially equal to the distance between the lower ends of the segments (Fig. 2) and the shoulders 30a of the punch 30, the die 26 moves with the segments, said movement beingopposed by the spring 39 as the sleeve 23 moves from the position shown in Fig. 2 to that shown in Fig. 3, and said movement being permitted by the groove 25 (Fig. 5) which receives the pin 24. Since the die 26 moves with the segments as they are being formed into the bars B, Wear on the die 26 is substantially reduced. During the formation of the dove-tail tangs t, the material of the segments flows toward one another and into contact. Because further flow toward the center of the die is resisted, the material of the segments is caused to take on the shape of the ends of the punches. As the material forming the dove-tail tangs come together, the pressures which they apply to one another are equal and opposite thus substantially re ducing strain on the die and punches.

Following the operation shown in Fig. 3 the slide 21 moves to the position shown in Fig. 4 as the ejector rod 34 moves toward the slide 21 to force the punch 30 and the bars B out of the die 26. The separation of the punch 48 from the punch 30 is such that the bars are released from the punches so that they may gravitate into a hopper. As the rod 34 is moved to ejectthe bars, the cylindrical parts 32 are caused toengage the bottom, as seen in the drawings, of segments 35 which form the bushing 36, thereby causing the sleeve 38 to move from the position shown in Fig. 3 to that shown in Fig. 4 whereby the spring 39 is compressed to cause return of die 26 to normal position. When the ejector operating mechanism of the header retracts from the rod 34, the spring 39 expands to move the bushing 38 downwardly, as seen in the drawings, to the position shown in Fig. 1. Duringthis downward movement the bottom of bushing 36 engages the cylindrical parts 32' to which the punch 30 is attached and causes the punch 30 to-return to the starting position shown in Fig. 1.

Thus two segments S are formed simultaneously into two bars B by causing them to be located within a die while the punches 30 and 48 having shearing blades30b and 48b respectively cut into end portions of the segments to provide the dove-tail tangs t of the bars. The shoulders 30a and 48a of punches 30 and 48 respectively approach each other to such distance that the spacing between these shoulders is thesame as the length of the segments S. It is not the purpose of these shoulders to exert a deforming pressure upon the Segments S, but merely to confine the ends of the segments while other portions are being deformed to make the dove-tail tangs. Therefore during formation of these tangs the length of the bars remains substantially the same as that of the segments. Therefore the. length of the bars is uniform and the tangs are located a uniform distance from the ends of the bars.

While the embodiment of the present invention as herein disclosed constitutes a preferred form, it is to be understood that other forms might be adopted.

What is claimed is as follows:

A die assembly including a die, a die holder having a recess for receiving the die and Within which the die has movement relative tothe holder from a normal position to a position closer withinthe recess during operation, a passage in said die and die holder, an article ejecting punch in said passage, a member within said recess having an opening in which the punch is positioned, a spring in said recess positioned between said member and the die, and urging the member toward a fixed part of the holder and the die away from said fixed part to normal position, a stop arresting movement of the die away from said fixed part, and means operable by the ejecting punch as it moves toward ejecting position to move said member in the same direction so as to cause the spring to be additionally stressed to force return of the die to normal position, said spring operating to effect return of the ejecting punch to its initial position after movement of said punch to its ejecting position.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,402,919 Carlson Jan. 10, 1922 1,457,801 Van Dusen Jan. 5, 1923 1,690,917 Wilcox Nov. 6, 1928 1,693,997 Carter Dec. 4, 1928 1,898,696 Sorensen Feb. 21, 1933 2,042,375 Abel May 26, 1936 2,122,874 Whipple July 5, 1938 2,253,003 Whipple Aug. 9, 1941 2,360,528 Talmage Oct. 17, 1944 2,411,379 Langhammer Nov. 19, 1946 2,549,642 Seelig Apr. 17, 1951 FOREIGN PATENTS Number Country Date 199,109 Great Britain June 13, 1923

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