US2636253A - Means for and method of producing sheet metal lock washers - Google Patents

Description

April 28, 1953 c. A. REES 2,636,253

MEANS FOR AND METHOD OF PRODUCING SHEET METAL LOCK WASHERS Filed Feb. 20, 1948 2 SHEETS-SHEET 1 J6 INVENTOR.

c. A. REES 2,636,253

MEANS FOR AND METHOD OF PRODUCING SHEET METAL LOCK WASHERS April 28, 1953 2 Sl-lEETS-Sl-IEET 2 Filed Feb. 20, 1948 mm ..Q %E E w MEI N w 6 Y E QM N1 \h QNM M N K E E WM Q U Q g E.

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@E W M my n R E Patented Apr. 28, 1953 UITED STATES PATE'E' QFFIQE MEANS FOR AND METHOD OF PRODUCING SHEET METAL LOCK WASHERS Clarence A. Rees, Chicago, Ill., assignor to Illinois Tool Works, Chicago, 111., a corporation of Illinois This invention relates generally to means for and method of producing lock washers from sheet metal stock and, more particularly, to apparatus for and methods of producing lock washers having folded marginal body portions which provide a thickened rim to prevent complete flattening of locking teeth.

One of the problems incident to the manufacture of lock washers having folded over or thickened rim portions is that of preventing fractures. For example, when the annular internal margin of sheet metal normally employed in the manufacture of lock washers is drawn axially and then bent into overlapping relationship with the remainder of the stock, said stock is subjected to severe strains and stresses which have a tendency to encourage fractures. It is, therefore, one of the important objects of the present invention to make possible the manufacture of the lock washers mentioned above without experiencing the impairment or fracture of the metallic sheet 7 stock.

More specifically, the invention contemplates the provision of means whereby sheet stock may be progressively fed past a series of stations for perforating and subsequently forming the metal stock into a toothed lock washer having a folded rim construction.

To facilitate the practice of the methods of the present invention, the provision of a tool or mechanism of novel design is contemplated, which is adapted to extrude the material of the stock defining a pro-formed aperture in such a manner that the extruded material may finally be folded back against the remaining material in the form of a continuous, unbroken annular body. To this end, the aforesaid mechanism is designed to progressively engage the material with diameters of increasing size until the required amount of stock has been extruded.

It has also been found that during the initial perforating operation prior to the aforesaid extrusion step, it is not uncommon for a burr or flu to be formed at the underside of the stock immediately adjacent the aperture. The presence of this fin, and particularly minute scorings or cracks therein, tends to enhance stock fracture during the subsequent extrusion process. It is a further object of the present invention to overcome this difiiculty by so working the material of the aforesaid burr or fm that the tend ency for fracture in this'vicinity is precludedv The foregoing and other" objects and advantages will be more apparentfrom the following detailed description when considered in "connection with the accompanying drawings, wherein Figure 1 is a plan view of a lock washer having a folded over inner rim capable of being pro: duced by employing a mechanism and practicing methods contemplated by the present invention.

Figure 2 is a central sectional view ofthe abovementioned lock. washer, taken substantially along the line 22 of Figure 1.

Figure 3 is a side elevational view of one of the tools employed in practicing the present method,

the primary function of which is to so condition sheet metal material in the vicinity of a preformed aperture that said material may be extruded and completely folded back upon itself without danger of fracture.

Figure 4 is an enlarged transverse view illustrating the first or perforating step in the process of manufacture contemplated hereby.

Figures 5 to 10, inclusive, illustrate the progressive metal working or forging action of the tool illustrated in Figure 3.

Figure 11 is a sectional view of the work similar to the sections shown in Figures 4 to 10, inclusive, after the extruded stock has been folded back toward the remaining'portion of the stock.

Figure 12 is a sectional view similar to Figure 11, showing the results of a subsequent step in the process wherein the single thickness of the external areaof the washer is centralized with respect to the folded over or thickened inner rimof the washer.

Figure 13 is a vertical sectional view of a die mechanism for progressively stamping and forming sheet material in accordance with the teachings of the present invention; and

Figure 14 is a plan View of sheet metal stock as it is fed through the progressive die of Figure 11, said view illustrating the successive stamping and forming operations to which the sheet stock is subjected as it moves step by step through said die. r

- Referring now to the drawings wherein like numerals have been employed to designate similar parts throughout the various figures, it will be seen that Figures 1 and 2 disclose a lock washer of the type capable of being produced by practicing the present invention, said lock washer being designated generally by the numeral M. This lock washer hi consists of an internal annular body portion comprising an annular flange portion is folded over a complementary annular flange portion I 8 so as to provide a double thick;

ness of washer stock. Suitable prongs 29 formed integral with and extending radially, outward from the body portion I8 present work engaging to that portion of the methodwhichrelates to the extrusion of the material in the vicinity of the washer aperture. For more detailedinforma-f tion concerning this type of lock washer, =refer-.

ence is made to the patent to Poupitch, No. 2,321,155.

In the process of stamping and forming parts, such as washer elements and the like from-fiat sheet stock, it is not uncommon to employ a mechanismknown 130- those: skilled in.- the art :as pro.-

gressi-ve die mechanisms. In Figure 13, a vertical sectional View. of such a die mechanism is shown.-

This die mechanism-orset-is designatedgenerally by the numeral 24- and consists of anuppervertically shiftable punch holder ZS and a-lower stationary dieblock-28;-- For the .purposeeofilluse trating one practical embodiment of the present invention; a die mechanism is disclosed: which is capable-o1. simultaneouslyproducing a plurality 2 of-.-lock washersi'from'a-single'strip of sheet metal stock 'lhestoch 35 is progressively. moved from rightto left-Figures-IS andsll, by -any.suitable work shifting means (not shown): The advancing end of the sheetmaterialtfids initially in,

positionedebeneatha station indicated by the letter -A,--said station consisting of .a plurality of punches 32; As the punch holder-Zfi-descends, the

punches-1'32:function-to punch *out blanks 34,

Figure l3,leaving aperturesttivin the work sheet. Upon subsequent or upward movementofthe punch holder 2%; the sheet 30" is advancedto-the nextstation E, which consists of a group of pilot pins:38:- Asthe punch? holder ZB'again descends,-

these pilot-pinsbt registerwith the previously formed apertures 36 and thus serve as the stock continues to" advance instep-by step-fashion through theidiefimechanism" to accurately position the stock for all punching and forming opera-- tions."

Eventually, the stock is advancedto a forming station C. At thisstation is:located a material extruding tool l 6, :whi'ch l functions to force the materialof the stock 'in'the vicinity of1theaper-; tures 35 axiallyrinto.antunhrokenifiange; as -indicated iniFigureil3lf The structural and-functional characteristics 'ofthis station C will be -de-' scribed more in detail in a latter portion of' this specification; FlCm th6:StatlOn' C, the stock then shifts-"tea station D; where-a tool 42 moves into engagement with the annular flange previously extruded by the tool til. This causes-the-fiange to be' folded-over'the remaining portion ofthe stock. 'As' the sto'ck'continues to advance; it ulti-- mately reache the station-Ejwhere a group of punches Ml produce clover leaf apertures 46. These apertures in thezaggregate form a plurality of connected tooth elementsor partly formed-lock washers. A second set: of pilot or. centering pins 46 at a station F functions to. maintain accurate alignment of the washer stockand also-serves to maintainthe hole sizes. ..At.the nextstation G; the. external prongs. of the. partially formed washers are twisted Icy-suitable forming tools 48, and atthe final... station these washers are the:

completely severed from each other by punches 50 Referring now more specifically to the stock extruding tool 43, Figs. 3 and 13, it will be seen that this consists of a frusto-conical upper extremity included within the bracket 52 of Fig. 3. Particular attention is directed to the fact that this frustoeconicalupperextremity or. head 52 is made up of a plurality of work engaging sections, each section slightly increased in external diameter as these sections progress from the upper or centering extremity of the head 52. For purposes of convenience, the uppermost section is designated as 52 and-the lower largest section by the numeral 52 Allof the section interposed between the section .52 and 52 slightly increase in diameter andeach section is preferably formed with a peripheral surface having a slight taper of approximately 1. Also, the upper and lower margins of each sections are rounded for purposes about tobe described,

When, the punches 32 produce the apertures 36 in the work piece 38, the shearingaction of.

the punches has a tendency to form an annular.v H burr or fin 54, illustrated in Fig. 4. Not. infrequently. these. annular fins have. minute tool marks or scorings which must beironed .outif further fracture is to be prevented. Experience has shown that if the .material of. thev stock '30.. in the vicinity of this finfid is extruded axially.. there is a tendency for the afoi'esaid..minute.

scorings to developinto longer fractures. The

tool ithes been designed to obviatethis difiiculty.

At this point in the description, it should be. v understood that the sheet material 39" moves up:

wardly'as a unit with the punch holder 28 dueto.

the frictional iengagementpof the punches 32' within the apertures. formed thereby, As the,

material 3!! rises to a level which is 'sufiicient. to

clear the upper. extremity. of the extruding tool. All, a conventional fistripper, mechanism (not.

shown) functions to strip the stock fromthe punches 32 and the pilotrpins .38,.thereby enabling the stock to beadvanced. to a pOsition. immediately above the tools 40. As the punch. holder 26. again descends, the previouslyformed, apertures 35 make initial telescopic. association,

with the uppermost section 52 tool 40.,

of the extruding .The upper margin of the section 52 is rounded, and the diameter of the. section is.

slightly smaller than the aperture 36.. Figure ,5 discloses the initial forging orcolcl .workingactionon the fin .54; ,The bottomcuryature of the section 52 and: the upperflcurvature ofitheseoe, tion 7.52 Figure 5, cooperate initially to engage.

the fin 54 in cold. working. or forging, the may.

terialof the fin. As the work 311 continues tov be forced downwardlyover, the tool 40, the tapered. periphery. of. the. tool section 52 1exerts radial. outward pressure against the inner periphery of the work, and ultimately. the partially worked fin 54-moves into engagement with the lower.

curved portion of. the toolsection-52 and the up-.

per merging curved surface of the section 52 By.- this time-the fin or burr 54 has been kneaded or cold worked so as to materially reduce it in. cross. sectional. size,- thereby reducing materially any, tool scorings or the start-of fractures in the fin:

By the time the work piece is pushed downwardly over theztool section 52. Figurefl, the annular portion of the stock begins to experience outward bending. In this connectioni-t will be un-, derstood that the-outward bending-of the stock does not begin. until thefin 54. has,,been cold workeclto. such anextent .that...no t ool1 scorings;

or breaks in thestock exist. It will be noted from Figure '7 that the burr or fin has been kneaded away, and in place of the fin this annular corner of the stock is being rounded. In Figure 8 the work has been advanced to the point where an appreciable bend has occurred and the annular sections of the tool 40 are beginning'to exert a burnishing action. This burnishing action will be more; clearly understood from Figure 9, at which time the inner upturned flange of the work is being burnished by the peripheral surfaces of the tool'sections. Finally, when the work is moved to the position shown in'Figure 10, the'ent'ire inner surface of the bent up flange has been subiected to a polishing, cold burnishing or burnishing action. I

Itwill also be noted Figure 10 that the action of the tool 49 is such as to cause the upturned or bent flange to partake of a reverse curve or bend. This is of importance because after the stock has been moved upwardly and stripped from the tool Land then advanced to a position beneath the tool 52, it must be in readiness to be f'o lded over. As the tool 42 descends, the flange l6 readily bends outwardly because of the initial curlimparted thereto by the tool 40, as illustrated'in Figure 10. Obviously, the free margin of the fiange I6, Figure 11, is subjectedto severe strains and stresses 'asit is folded against the complementary annular portion [8 of the body. If this outer or free margin of the flange I 6 is not completely free from small fractures during the folding over process, said margin will not maintain its peripheral continuity. In other words, at this point in the process of manufacture, the avoidance of slight cracks or fractures of the most minute form of the margin of the extruded portion of the stock is extremely important. In folding over the material in this manner, increase in external diameter of the outer margin of the flange l6 occurs, thereby increasing quite materially the tendency for stock fracture in this vicinity.

After the flange 16 has been fo ded over and against the complementary marginal portion [8 of the stock, Figure 11, it is stripped from the tool 42 and advanced into position beneath a sleeve-like tool 56 which surrounds the pilot pin 46, Figures 11 and 12. This tool 56 cooperates with a complementary tool member 5'! positioned therebeneath to centralize the single thickness of washer stock with the double thickness presented by the folded over annular sections l6-I8. Thus, the plane of the single thickness of washer material is centrally positioned with respect to the bounding planes of the combined sections During a subsequent cycle of reciprocation, the work is advanced to the Station G, where the washer teeth are twisted. Subsequently, the work is advanced to the Station H, where the completely formed washers are severed from each other in readiness to be heat treated.

From the foregoing it will be apparent that the present invention contemplates improved, practical extrusion methods and apparatus. These improved methods and apparatus may be used in the manufacture of thick rim lock washers and the like. The invention particularly lends itself for use with progressive die mechanisms in which sheet material may be advanced step by step past the various stations. Cracks, fractures, tool marks and abrasions in sheet stock initiated during. the blanking operation do not develop into more extensive cracks or fractures when the 6 above described invention is employed. The stepped forming or extruding tool heretofore described serves to bend or extrude the stock in a direction normal to the plane thereof, and

contemporaneously to forge or cold work and be critically stretched in the subsequent fold-- ing over operation, tendencies for fracture are reduced to a minimum. By subjecting the edge of the stock to compression and contemporaneously forging one corner of said edge by beveled or rounded extruding shoulders of the tool, the danger of stock fracture when the material is subsequently folded over is eliminated. The method and apparatus herein contemplated make it possible to produce thick rim lock washers without increased cost in material by reason ofthe fact that the portion of the stock which is extruded would, under ordinary circumstances, be discarded as scrap. That is to say, the marginal portion of the sheet metal stock defining the aperture produced by the empumn would be removed in following conventional methods of lock washer manufacture. The present invention makes it possible axially to displace this hitherto unused annular section of stock surrounding the aperture into an annular flange or neck, and contemporaneously to Work, knead or forge said annular section including the marginal edge so as to counteract tendencies for stock fracture during the final folding over step in the process of extrusion.

Whi e for purposes of disclosure specific die structures have been disclosed herein, it will be apparent that the invention contemplates other modifications and changes without departing from the spirit and scope of the appended claims.

The invention is hereby claimed as follows:

1. The method of forming an annular flange in sheet metal stock which consists in punching an aperture in the stock resulting in a stamped burr along the corner of the stock defining the portion of the punched aperture adjacent the side of the stock from which the punched blank is ejected, forging said burr and bending the marginal area surrounding the aperture into an annular flange substantially free from fractures by initial engagement of said burr with an annular working surface of a diameter substantially equal to the diameter of the whole defined by the burr, and subsequently engaging the burr and marginal portion of the stock in the vicinity of said burr with a succession of annular working surfaces including curved shoulder areas of progressively and gradually increasing diameters.

2. The method of forming an annular flange in sheet metal stock as set forth in claim 1, including the step of engaging the inner periphery of said flange at a point spaced from the flange margin by a working surface of increased diameter whereby to dispose the flange substantially normal to the plane of the stock.

3. The method of forming an annular flange in sheet metal stock asset forth in claim 1 including the step of folding said flange against a comin an apertured sheet metal Work piece includ-.

ing annular abutment means for 'annularly contacting said work piece, and a shank-like tool disposed coaxially with respect to said annular abutment means and consisting of a plurality of relatively minutely stepped annular working surfaces designed to act upon the marginal area of stock with defines a work aperture, the annular working surface of minimum diameter being located at the entering end of the tool with succeeding annular Working surfaces gradually increasing in diameter, adjacent annular working surfaces being joined by curved shoulder areas,

for forging apertured sheet stock, the space between the periphery of said annular tool surfaces and the internal periphery of said annular abutment means diminishing from at least twice the thickness of the work piece at the entering end of the tool to a space not less than the worl piece thickness when the working surface of maximum diameter is in operative position with respect to said internal periphery.

6. In an apparatus of the type described in claim 5 wherein each of said annular working surfaces is frusto-conical with their smaller diameters extending toward the entering end of the tool.

7. In an apparatus of the type described in,

claim 5 wherein the axial extent of eachannular working surface is at least twice the radial extent ofits adjacent curved shoulder portion.

CLARENCE A. REES.

, References Cited in the file of this patent UNITED STATESPATENTS Number Name Date 1,793,296 Wilson Feb. 17, 1931 1,902,269 Stoll Mar. 21, 1933 1,915,612 Olson June 27, 1933 1,931,352 Kemp Oct. 17, 1933 1,989,750 Garret Feb. 5, 1935 2,051,639 Kalmbacker -1 Aug. 18, 1936 2,157,354 Sherman May 9, 1939 2,321,155 Poupitch June 8, 1943 2,352,265 Kapple et a1 June 27,1944 2,410,204 C'ummins Oct. 19, 1946' 2,427,756 West Sept. 23, 1947,

FOREIGN PATENTS Number Country Date 178,574 Great Britain Apr. 21', 1922

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