Patent Abstract:
A method and apparatus for the precise manufacture of high quality, four-sided electrical contacts by means of a closely controlled material skiving process. The apparatus is designed so that the starting material from which the four-sided electrical contacts are made is closely constrained in the area of the shear boundaries so that predictable and precisely controlled shearing of the material can repeatedly be achieved to initially form four precursor sides, two of which are arcuate. The apparatus also includes sequentially operating forming mechanisms for precisely forming the precursor sides of the precursor contact into a final end product configuration.

Full Description:
This is a Divisional application of co-pending application Ser. No. 10/305,340 filed Nov. 25, 2002 which is a Divisional Application of Ser. No. 09/827,883 filed Apr. 5, 2001, now U.S. Pat. No. 6,523,387. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to electrical contacts and to a method and apparatus for making the contacts. More particularly, the invention concerns a method and apparatus for making four sided electrical contacts of the character having specially configured, spaced apart spring like tines. 
     2. Discussion of the Invention 
     Fork like electrical contacts are well known in the art and are widely used in a number of different kinds of electrical applications. Typically, the prior art fork contact includes a pair of inwardly biased sides or tines that extend out from a base so that a member such as a pin contact may be inserted between the pair of sides to make an electrical connection therewith. 
     Because of the extensive use in industry of electrical contacts of the character described in the previous paragraph, various methods have been suggested in the past for the high volume manufacture of the electrical contacts. In one common prior art method the contact members are stamped or lanced from a suitable piece of sheet material and the contact tongues or tines are then formed or coined as necessary. Exemplary of such electrical contacts is those disclosed in U.S. Pat. No. 3,286,220 issued to Marley et al. and in U.S. Pat. No. 3,812,452 issued to Sturm. 
     Another prior art method of making electrical contacts involves the splitting of a bar of electrically conductive metal longitudinally over a portion of its length to form two contact tongues. Such a method is described in U.S. Pat. No. 4,040,177 issued to Beeler et al. In one form of the Beeler et al. method, a portion of the bar to be split is to be enclosed between two tools. The tools are then moved, sliding along each other perpendicular to the longitudinal dimension of the bar in mutually opposed directions over a distance which is sufficient to produce the desired splitting. In another method of splitting, the bar to be split is retained over its length such that one end is free to receive a wedge which is longitudinally driven into the bar through this free end. 
     Experience has shown that, in order to repeatedly produce precision electrical contacts by splitting or shearing the material, it is absolutely essential that the portion of the material immediately adjacent the boundary of the split or shear be rigidly and positively contained. Only in this way can a predictable controlled, precise split of the material be achieved. 
     An elegantly simple prior art method and apparatus for producing two sided precision electrical contacts by a shearing method is disclosed in U.S. Pat. Nos. 4,909,763 and 4,970,782 issued to the present inventor. In the practice of the methods disclosed in these patents, the starting material from which the electrical contacts are made is closely constrained within the area of the shear boundaries so that predictable and precisely controlled shearing of the material can be repeatably achieved with great accuracy. The present invention comprises an improvement upon the method and apparatus disclosed in U.S. Pat. No. 4,909,763 and in U.S. Pat. No. 4,970,782 and, for this reason, these patents are hereby incorporated by reference as though fully set forth herein. 
     As will be better understood from the discussion which follows, the thrust of the present invention is to improve on the techniques described in the previously mentioned, incorporated by reference patents and in so doing to provide a method and apparatus for the high volume production of four sided electrical contacts from a starting material which comprises a plurality of spaced apart, pre-cut pins which are precisely split to form four, spaced apart tines or tongue like members. The apparatus of the present invention then forms these four tongue like members into precisely configured, four sided contacts. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a method and apparatus for the precise manufacture of high quality, four-sided electrical contacts by means of a closely controlled material skiving or splitting process. More particularly, it is an object of the invention to provide an apparatus of novel design for use in making the precision, four-sided electrical contacts wherein the starting material from which the electrical contacts are made is closely constrained in the area of the shear boundaries so that predictable and precisely controlled shearing of the material can repeatedly be achieved to initially form four precursor sides. 
     It is another object of the present invention to provide an apparatus for making four-sided electrical contacts of the aforementioned character in which the apparatus includes forming means for forming the precursor sides into a final, end product configuration. 
     Another object of the invention is to provide an apparatus of the character described in the preceding paragraphs which automatically performs the shearing and forming steps on a progressive basis. 
     Another object of the invention is to provide an apparatus of the class described which is of simple, straightforward design requiring a minimum amount of maintenance. 
     Still another object of the invention is to provide a method and apparatus of the character described in the preceding paragraphs which is easy to use by relatively unskilled workmen and has the ability to accomplish very high volume production rates. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a generally perspective view of one form of the four sided electrical contact made in accordance with the method of the present invention.  FIG. 2  is a generally perspective, illustrative view of a greatly simplified form of shearing mechanism. 
         FIG. 2A  is a generally perspective, exemplary view of the general type of precursor article produced using a shearing mechanism of the character depicted in  FIG. 2 . 
         FIG. 3  is a top plan view of the shearing station of the apparatus of the invention and diagrammatically illustrates the initial steps in the method of the invention for shearing the starting workpieces to form the four sides of the precursor of the electrical contact of the general character shown in  FIG. 2A . 
         FIG. 4  is a cross-sectional view taken along lines  4 — 4  of  FIG. 3  showing the shearing tool advanced into one of the die portions of the shearing mechanism provided at the shearing station. 
         FIG. 5  is a cross-sectional view taken along lines  5 — 5  of  FIG. 3  showing the appearance of the outwardly extending tongues of the precursor contact after the starting workpiece has been sheared by the forward advance of the shearing tool between the dies of the apparatus of the invention. 
         FIG. 6  is a fragmentary top plan view showing removal of the shearing tool from the just formed precursor contact. 
         FIG. 7  is a cross-sectional view taken along lines  7 — 7  of  FIG. 6  showing the configuration of the precursor article after formation of the top, bottom and side precursor tongues. 
         FIG. 8A  is a fragmentary, generally diagrammatic top plan view of the tongue spreading station of the apparatus illustrating the first step of the method of the invention for forming the side tongues of the precursor article prior to their being shaped into their final configuration. 
         FIG. 8B  is a fragmentary, generally diagrammatic top plan view similar to  FIG. 8A  showing the next step in the side forming operation at the forming station, namely the insertion of the spreading tool between two forming dies. 
         FIG. 8C  is a fragmentary generally diagrammatic top plan view similar to  FIG. 8B , but showing the spreading tool in a retracted position following spreading of the side tongues. 
         FIG. 9  is a generally diagrammatic top plan view of the precursor tongue shaping stations showing the sequential steps of the method of the invention for shaping the top and bottom tongues of the precursor contact. 
         FIG. 10  is a cross-sectional view taken along lines  10 — 10  of  FIG. 9  showing the final shaping step for shaping the top and bottom precursor tongues. 
         FIG. 11  is a generally diagrammatic, top plan view showing the precursor tongue shaping station for shaping the spaced apart, precursor side tongues of the contact into their final shaped configuration. 
         FIG. 12  is a generally diagrammatic top plan view of the tongue shaping station shown in  FIG. 11 , illustrating the shaping tool of  FIG. 11  in a retracted position relative to the formed contact. 
         FIG. 13  is a cross sectional view taken along lines  13 — 13  of  FIG. 11 . 
         FIG. 14  is a generally diagrammatic top plan view showing an alternate form of the apparatus of the invention and depicting the steps of an alternate method of the invention for shearing a workpiece of a somewhat different construction. 
         FIG. 15  is a front view of a portion of the apparatus and workpiece shown in  FIG. 14  illustrating the method of shearing the alternate form of starting workpiece. 
         FIG. 16  is a cross-sectional view taken along lines  16 — 16  of  FIG. 14  showing the appearance of the top and bottom tongues following the initial shearing step. 
         FIG. 17  is a generally diagrammatic top plan view showing still another form of the apparatus of the invention and depicting the steps of the method of the invention for shearing a tapered workpiece. 
         FIG. 18  is a front view of a portion of the apparatus and workpiece shown in  FIG. 17  illustrating the method of shearing the alternate form of starting workpiece. 
         FIG. 19  is a cross-sectional view taken along lines  19 — 19  of  FIG. 17  showing the configuration of the tapered workpiece. 
         FIG. 20  is a cross-sectional view taken along lines  20 — 20  of  FIG. 17  showing the appearance of the top and bottom tongues following the initial shearing of the tapered workpiece. 
         FIG. 21  is a cross-sectional view taken along lines  21 — 21  of  FIG. 17  showing the appearance of the top and bottom tongues after the initial forming step. 
         FIG. 22  is a generally diagrammatic, fragmentary top plan view similar to  FIG. 17  but showing still another form of the method of the invention for shearing a tapered workpiece that also varies in width. 
         FIG. 23  is a cross-sectional view taken along lines  23 — 23  of  FIG. 22  further showing the configuration of the tapered workpiece. 
         FIG. 24  is a cross-sectional view taken along lines  24 — 24  of  FIG. 22  showing the appearance of the top and bottom tongues following the initial shearing of the tapered workpiece. 
     
    
    
     DESCRIPTION OF THE INVENTION 
     Referring to the drawings and particularly to  FIG. 1 , one type of four sided electrical contact made in accordance with the method of the present invention is there illustrated and generally designated by the numeral  14 . Contact  14  includes a stem portion  16  and four cooperating tongues  18 ,  20 ,  22  and  24  respectively. After being formed each of the four tongues of the electrical contact is generally arcuate in shape having one end integrally connected to the stem portion and the opposite, or free ends having an outwardly curved portion, generally designated in  FIG. 1  by the numeral  30 . 
     Before discussing the various tongue forming and shaping steps of the method of the present invention that are required to form contact  14 , a brief discussion of the basic shearing techniques of the invention is in order. In this regard, referring particularly to  FIG. 2 , a very basic type of shearing apparatus is there diagrammatically illustrated. Similarly,  FIG. 2A  shows a very basic form of precursor, four sided contact made using the apparatus shown in  FIG. 2 . As indicated in these figures, during the shearing step the workpiece “W” is secured within a clamping means here depicted as first and second cooperating clamping elements  38  and  40  ( FIG. 2 ). 
     As more fully discussed in U.S. Pat. Nos. 4,909,763 and 4,970,762, which patents are incorporated herein by reference, clamping elements of the same general character there described are used to support the workpiece “W” as the splitting tool or punch element  42  advances toward the securely clamped workpiece. As depicted in  FIG. 2 , the workpiece “W” has a width greater than the width of channels  38   a  and  40   a  which are formed in elements  38  and  40  in the manner shown in the drawings. 
     As will be discussed in greater detail hereinafter, by precutting the workpiece to some desired width greater than the width of channels  38   a  and  40   a , splitting of the workpiece by the shearing tool  42  ( FIG. 2 ) will result in the simultaneous formation of the side tongues  35   b  and the top and bottom tongues  35   c  and  35   d  (see  FIG. 2A ). Because of the way in which the workpiece is split by the skiving tool, if the width of the workpiece is properly selected, the thickness of the side tongues will be approximately half the thickness of the starting workpiece. More particularly, it is to be appreciated that the width of the workpiece “W” must be carefully selected to be about twice the thickness of the workpiece “W” if all four contacts are to have the same cross-sectional dimensions. Therefore, by judiciously choosing the width of the workpiece in proportion to its thickness, the controlled splitting of the workpiece “W” will uniquely produce a precursor contact having four tongues of substantially the same cross-sectional dimensions. 
     Notwithstanding the foregoing, it is to be appreciated that for some end product applications, having all four tongues the same may not be required, or even desired. By way of example, if the workpiece “W” shown in  FIG. 2A  were to be made somewhat wider than the width “D”, then the thickness of side tongues  35   b  would be greater than the thickness of top and bottom tongues  35   c  and  35   d . If this were to be done, the stiffer side contacts could be used as locators in the resulting connector. In similar fashion, side tongues  35   b  could be formed so that one could compensate for the increased thickness of the side tongues by increasing the length of the lever arm. This would provide the added benefit of reducing the insertion force of the mating male contact. 
     As is also apparent from a study of  FIG. 2A , the thickness of top and bottom tongues  35   c  and  35   d  is determined by the thickness “T” of the workpiece “W”, while the width of the tongues is independent of the thickness of “W”. On the other hand, the width of side tongues  35   b  is determined by the thickness of “W”, and the thickness of the tongues and  35   b  is independent of the thickness of “W”. Uniquely, the width of the side tongues is substantially equal to the thickness of the workpiece. Thus the cross-sectional dimensions of the four tongues are determined quite differently from one pair to the other. For example, on some occasions, it may be desirable to have the side tongues  35   b  thicker and longer than the top and bottom tongues. In this instance, the width of the starting workpiece would be adjusted accordingly to achieve the desired end result. 
     As discussed in much greater detail in U.S. Pat. No. 4,909,763, the imposition of the very high shearing on the workpiece caused by the shearing tool causes a novel burnishing effect to occur on either side of the apex of the punch. This burnishing action results in the formation of a remarkably fine finish on the sheared surfaces of the precursor electrical contact. In accordance with one form of the method of the present invention, as the shearing tool  42  advances into the channel within which the workpiece is clamped, burnished, precursor top and bottom tongues  35   c  and  35   d  will be precisely formed. 
     Referring now to  FIGS. 3 through 7 , one form of the method and apparatus of the present invention for making the electrical contact  14  is there illustrated. In this instance, the starting workpiece is provided in the form of an elongated strip of material having a plurality of outwardly extending fingers  44  ( FIG. 3 .) This starting workpiece, which is identified in  FIG. 3  as “WP”, is formed by a conventional blanking operation well known to those skilled in the art which produces an indexable work strip having a plurality of outwardly extending fingers  44 . After the starting workpiece has been indexably positioned on the work surface of the apparatus using index pins  46 , it is advanced to the shearing station, generally identified by the numeral  48 , where the shearing step is accomplished. During this important shearing step, the fingers  44  are sequentially controllably sheared to produce four sided, precursor contacts  55  of the general configuration illustrated in  FIGS. 5 and 7 . After the shearing step, each individual precursor contact formed includes a stem portion  55 a, which, at this stage is a part of strip “WP”, spaced apart precursor side tongues  55   b  ( FIG. 6 ), a precursor top tongue  55   c  and a precursor bottom tongue  55   d  ( FIG. 7 ). 
     In a manner presently to be described, in using the apparatus of the present invention as generally depicted in  FIGS. 3 through 13 , the workpiece is controllably advanced to the right as seen in  FIG. 3 , first to the shearing work station  48  and then through several forming and shaping stations where the precursor tongues are strategically formed into their final shape. 
     At the shearing station, diagrammatically depicted in  FIG. 3 , a selected finger  44   a  is securely clamped in position by cooperating upper and lower clamping elements  58  which comprise a part of the support means of the apparatus of the invention. Each of the clamping elements is provided with a shearing tool receiving channel  58   a  which is of a width less than the width of fingers  44 . With finger  44   a  securely clamped in place between the clamping elements in the manner shown in the central portion of  FIG. 3 , shearing means, here shown in the form of a shearing tool or punch  60 , is advanced from the position shown in the central portion of  FIG. 3  to a position shown in the right-hand portion in  FIG. 3 . As the shearing tool advances it will controllably shear the workpiece in a manner to form the precursor contact which includes precursor side tongues and precursor top and bottom tongues. More particularly, after the shearing tool has reached the position shown in  FIG. 5 , the four precursor tongues comprising a pair of precursor side tongues  55   b , a top precursor tongue  55   c  and a bottom precursor tongue  55   d  will have been formed. As indicated in  FIG. 7 , after the shearing step the two precursor side tongues  55   b  and the precursor top and bottom tongues  55   c  and  55   d  respectively will have the general configuration shown. Following retraction of the shearing tool as illustrated in  FIG. 6 , the workpiece “WP” will be advanced to the right in a direction toward the first of several forming stations of the invention wherein the precursor tongues of the precursor contact will be shaped into their final configuration. 
     It is to be understood that as the precursor contact moves toward the first forming station of the apparatus, another finger  44  of the workpiece will automatically be moved into position to be securely clamped between upper and lower clamping elements  58  of the apparatus which are appropriately moved into position above and below on either side of the finger as the finger is moved into position within the shearing work station. Once the finger to be sheared is in position between the clamping elements and spanning the shearing tool receiving channels  58   a , the shearing tool  60  can once again be advanced toward the securely clamped workpiece to controllably shear the central portion of the finger and thereby form the next precursor contact which will also have the general configuration shown in  FIG. 7 . The means for indexably advancing the workpiece, for positioning the clamping elements and for advancing and retracting the shearing tool are well understood by those skilled in the art and will not be discussed in detail herein. 
     As best seen by referring to  FIG. 5 , shearing tool  60  includes a body portion  60   a  and a cutter portion  60   b  which is integrally formed with body portion  60   a . Cutter portion  60   b  includes walls  60   c  and  60   d  which taper inwardly and terminate in an apex  60   e  which defines the shearing edge of the shearing tool. Shearing tool  60  preferably has side walls tapering at an angle of between about 60 and about 80 degrees. The shearing tool functions in much the same manner as the earlier described exemplary shearing tool  42  and, as shown in  FIGS. 4 and 5 , as it moves inwardly of channel  58   a , precursor top and bottom tongues  55   c  and  55   d  are simultaneously formed into the general configuration shown in  FIG. 7  leaving side tongues  55   b  in a spaced-apart configuration. Once again, reference should be made to incorporated by reference U.S. Pat. Nos. 4,909,763 and 4,970,782 for a more detailed discussion of the design requirements for the shearing apparatus shown in  FIGS. 3 through 6  and for the details of the shearing step accomplished at the shearing station  48 . 
     After shearing of the selected finger  44  is completed, the shearing tool is retracted ( FIG. 6 ) and the precursor electrical contact formed during the shearing operation is advanced forwardly of the apparatus to a forming station  63  having the character generally illustrated in  FIGS. 8A ,  8 B and  8 C. In the manner next to be described, during the forming steps of the method of the invention, first forming means acts on the precursor contact to strategically shape the first and second precursor side tongues thereof to form shaped first and second side tongues. This important first forming means here comprises two separate forming mechanisms, the first of which comprises a spreading means located at station  63 . This spreading means, which here includes a spreading tool  64  and cooperating backing members  66   a  and  66   b  functions to controllably spread apart and initially shape the precursor side tongues  55   b . Also forming a part of the first forming means of the apparatus of the invention is a second forming mechanism which, as will presently be discussed, functions to finally shape the precursor side tongues after they have been controllably spread apart by the spreading means. 
     Considering first the important spreading means of the apparatus, this means here comprises first and second backing members  66   a  and  66   b  which are positioned on either side of a selected precursor electrical contact such as the contact identified in  FIG. 8A  by the numeral  67 . Also forming a part of the spreading means of the invention is the previously mentioned spreading tool  64 , which in the manner shown in  FIG. 8B , can be advanced between the precursor side tongues  67   a  and  67   b  so as to urge them outwardly to pressural engagement with the inner surfaces of the backing members  66   a  and  66   b . After the precursor side members have been acted upon by the spreading tool  64 , the electrical contact will take on the configuration generally shown in  FIG. 8C  wherein the partially formed contact is identified by the numeral  69 . 
     Turning next to  FIGS. 11 ,  12  and  13 , another forming station  70  is there shown. Located at station  70  is the previously mentioned second forming mechanism, which shapes the spread-apart side tongues into their end product configuration. As best seen in  FIG. 11 , the second forming mechanism, which comprises a part of the first shaping means, includes first and second forming members  72  and  74  which are positioned proximate the spaced apart, precursor side tongues  67   a  and  67   b  of the precursor contact  69 . After members  72  and  74  have been moved into the position shown in the left hand portion of  FIG. 11 , a first forming mandrel  76  is moved inwardly in the direction of the arrow  77  in  FIG. 11  to a location intermediate precursor side tongues  67   a  and  67   b . This done, members  72  and  74  are urged inwardly in the direction of arrows  79  shown in the right-hand portion of  FIG. 11  into pressural engagement with the precursor side tongues so as to urge the tongues into forming contact with the curved exterior surfaces  76   a  provided on mandrel  76 . The means used for moving the members  72  and  74  into pressural engagement with the precursor side tongues can take several forms well known to those skilled in the art including various types of mechanical means or, for example, hydraulically operated rams  79   a  which move the members in the direction of arrows  79  and which are diagrammatically illustrated in  FIG. 13 . 
     Following the final shaping of precursor side tongues  67   a  and  67   b  into their shaped, end product configuration, forming members  72  and  74  are retracted in the direction of arrows  81  of  FIG. 12  and forming mandrel  76  is moved outwardly in the direction of the arrow  83  of  FIG. 12 . Of course, members  72  and  74  are first retracted, and subsequently mandrel  76  is moved outwardly. This sequence of operation permits the formed tongues  67   a  and  67   b  to flex while the mandrel is being removed. It is to understood that forming members  72  and  74  can be moved into proximity with the precursor contact by several types of positioning means of a character well known to those skilled in the art 
     Prior to the final shaping of the precursor side tongues, as described in the preceding paragraph, the top and bottom precursor tongues are shaped by second forming means located at the shaping station  85 , the character of which is shown in  FIG. 9 . This important second forming means acts on the precursor contact to strategically shape the top and bottom precursor tongues. Provided at shaping station  85  are third and fourth, or bottom and top forming members  88  and  90  which are positioned proximate top precursor tongue  55   c  and bottom precursor tongue  55   d  (see also  FIGS. 7 and 10 ). As the forming members  88  and  90  move into the position shown in the central portion of  FIG. 9 , they will be urged inwardly toward a second forming mandrel  92  which has been advanced to a position interiorly of the precursor tongues of the contact. With forming mandrel  92  in the advanced position, forming members  88  and  90  are next urged inwardly in the direction of the arrows  93  of  FIG. 10  into a position wherein the top and bottom precursor tongues are urged into pressural engagement with the curved sides of mandrel  92  so as to shape the top and bottom tongues into their shaped configuration shown in  FIG. 10  wherein the shaped tongues are identified by the numerals  59   c  and  59   d . Once again the means for urging the precursor top and bottom tongues into pressural engagement with the mandrel can take various forms well understood by those skilled in the art and can comprise hydraulic rams  93   a , as diagrammatically illustrated in  FIG. 10 , for urging the forming members  88  and  90  in the direction of the arrows  93   c.    
     Referring next to  FIGS. 14 ,  15  and  16  an alternate apparatus of the invention for making four sided electrical contacts is there illustrated. This apparatus is similar in many respects to the apparatus of the invention previously described and is uniquely adapted to shear an alternate form of workpiece into a precursor contact having precursor side tongues and precursor top and bottom tongues. The workpiece here comprises an elongated, pin-like member  100  having a predetermined width and a predetermined thickness. The workpieces, or pin-like members  100  are affixed to a bandolier strip  102  of a character well known to those skilled in the art which has the configuration generally illustrated in  FIG. 14 . 
     Referring to  FIG. 16 , it can be seen that the stem portion  100   a  of the starting workpiece  100  is securely clamped to bandolier strip  102  by a clamping yoke  106 . After the starting pin  100  is securely clamped to the bandolier strip in a manner shown in the drawings, the strip is moved toward the shearing station generally designated by the numeral  108  where the shearing step is accomplished. Shearing station  108  is substantially similar to the previously described shearing station  48  and at this important shearing station a selected pin  100  is controllably sheared to produce a four sided, precursor contact of the general configuration illustrated in  FIG. 16  having a stem portion  160   a  that is equal in width and thickness to pin  100 . Following the shearing step, the precursor contact thus formed includes a stem portion  100   a , spaced apart precursor side tongues  110  and precursor top and bottom tongues  112  and  114  respectively. 
     During the shearing step a selected pin  100  is securely clamped between cooperating upper and lower clamping elements  118  which comprise a part of the support means of this alternate form of the apparatus of the invention. As before, clamping elements  118  are each provided with a shearing tool receiving channel  119  which is of a width less than the width of pin  100 . 
     With the selected pin  100  securely clamped in place between upper and lower support members  118  and shearing tool receiving channels  119  in a manner shown in the center portion of  FIG. 14 , shearing means here provided in the form of a shearing tool or punch  120 , is controllably moved toward channels  119 . As the shearing tool enters channels  119 , it will cleanly shear the central portion of the pin in a manner to form the precursor contact, which is of the general configuration illustrated in  FIG. 16 . Following the shearing step, shearing tool  120  is retracted and the bandolier strip  102  is moved to the right carrying the precursor contacts  104  with it. 
     Following the shearing step, the precursor contacts are transported by the bandolier strip toward the first and second forming means of the invention which are of substantially identical construction and operation to those previously described herein. 
     As was discussed in incorporated by reference U.S. Pat. No. 4,909,763, in some instances the shearing of the starting work pierces WP and  100  causes a “plowing” like effect occurs on the material as the shearing tool advances. This “plowing” like effect can result in the increase in thickness of the tongues and the concomitant shortening thereof. Stated another way, an examination of the top and bottom tongues formed in the shearing process reveals that in some instances they have become thicker than one-half the thickness of the workpiece  100  and stem portion  100   a  of the contact. Accordingly, if the top and bottom tongues were to be bent inwardly toward one another, their overall length would be less than the length of the unsupported area of the starting workpiece. The reasons for this thickening of the tongue walls as well as the foreshortening effect is discussed in detail in columns  9  and  10  of incorporated by reference U.S. Pat. No. 4,909,763 and will not be repeated here. Suffice to say that in some cases the thickness of the upper and lower tongues can vary from between about 50% of the thickness of the workpiece “WP” and stem  100   a  and about 60% of this thickness. The thickness of the tongues is, of course, at least equal to 50% the thickness of the workpiece and stem. 
     Turning to  FIGS. 18 through 21 , the steps of still another method for making electrical contacts is there illustrated. The apparatus depicted in these drawings is virtually identical to the apparatus of the invention shown in  FIGS. 3 through 13  as previously described herein. However, in this instance, the apparatus is uniquely adapted to shear a tapered finger of a workpiece “WT” into a precursor contact having precursor side tongues and precursor top and bottom tongues. 
     As best seen in  FIG. 19 , the workpiece “WT” here comprises an elongated strip of material  124  having a plurality of outwardly extending fingers  126  which are tapered in cross-section in the manner indicated in  FIG. 19 . The advantages of using this novel tapered workpiece are discussed in the paragraph that follows: 
     Experience has shown that, while the prior art, uniform-thickness, beam-type contacts of the character described in U.S. Pat. Nos. 4,909,763 and 4,970,782 issued to the present inventor are well suited for most applications, such contacts exhibit an inherent drawback. More specifically, these types of contacts, that have a uniform thickness beam supported at one end, undesirably exhibit maximum bending stress at the point of support that is proximate the end of the split or shear. By making the starting workpiece finger in a tapered configuration in which the finger tapers from a lesser thickness proximate its free distal end to a greater thickness proximate its proximal fixed end, the stress of the fixed end can be markedly reduced and the tendency of the bending stress to propagate the shear considerably lessened. 
     Referring to  FIGS. 17 and 18 , the apparatus there depicted is used to form the improved contact as described in the preceding paragraph. As previously mentioned, this apparatus is substantially identical to that shown in  FIGS. 3 through 13  and like numerals are used in  FIGS. 17 through 21  to identify like components. In using the apparatus to form the improved tapered tongue contacts of the invention, the starting workpiece “WT” is first indexably positioned on the work surface of the apparatus in the manner previously described using index pins  46 . This done, the workpiece is advanced to the shearing station, generally identified by the numeral  48 , where the shearing step is accomplished in the manner previously described. It should, of course, be noted that blocks  40  must have surfaces in their clamping channels that match the top and bottom surfaces of the fingers. 
     After the shearing step is completed, each individual precursor contact that is formed includes a stem portion  130  which, at this stage, is a part of a finger  126  of strip “WT”. Extending from stem portion  130  are spaced apart precursor side tongues  132  ( FIG. 18 ), a tapered precursor top tongue  134  and a tapered precursor bottom tongue  136  ( FIG. 20 ). Each of these top and bottom precursor tongues has a distal, first portion  138  of a first thickness “T-1” and a second, proximal portion  140  of a second thickness “T-2” greater than the first thickness. 
     As before, in using the apparatus of this latest form of the invention, which is generally depicted in  FIGS. 17 and 18 , the workpiece is sequentially advanced to the right as seen in  FIG. 17 , first to the shearing work station  48  and then through the several previously described forming and shaping stations where the precursor tongues are strategically formed into their final shape. 
     After the shearing step has been completed, the two precursor side tongues  132  and the precursor top and bottom tongues  134  and  136  respectively will have the novel tapered configuration shown in  FIGS. 20 and 21  wherein the tongues are thicker at their fixed or proximal ends and become thinner in a direction toward their free or distal ends. As earlier discussed, this unique tapered construction will reduce stress at the fixed proximal end thereby lessening the tendency of the shear to propagate. 
     Referring again to  FIGS. 17 and 18 , following the initial shearing step at station  48  and the subsequent retraction of the shearing tool, the workpiece “WT” will be advanced to the right in a direction toward the spreading means located at station  63  wherein the precursor side tongues of the precursor contact will be shaped in the manner previously described. Next, the workpiece will be advanced to the forming station  85  where, in the manner previously described, the top and bottom tongues will be shaped into their end product configuration wherein the product exhibits its novel tapered tongue configuration illustrated in  FIGS. 20 and 21 . 
     Referring to  FIGS. 22 through 24 , the apparatus used to form still another form of improved contact is there illustrated. This apparatus is substantially identical to that shown in  FIGS. 17 and 18  and like numerals are used in  FIGS. 22 through 24  to identify like components. In using the apparatus to form this latest form of improved contacts of the invention, the starting workpiece, here identified as WP- 1 , is first indexably positioned on the work surface of the apparatus in the manner previously described using index pins  46 . This done, the workpiece is advanced to the shearing station, where the shearing step is accomplished also in the manner previously described. It is to be noted that in this instance the workpiece WP- 1  includes a plurality of spaced apart fingers  150  each of which varies in width from a first width W-1, proximate its free end, to a second greater width W-2 proximate its fixed end ( FIG. 22 ). (The variation in width shown in the drawings is somewhat exaggerated for purposes of illustration.) As depicted in  FIG. 23 , each of the fingers  150  also varies in thickness from a lesser thickness proximate its free end to a greater thickness proximate its fixed end. As in the earlier described embodiments of the invention, in actual operation, the workpiece is sequentially advanced to the right as seen in  FIG. 22 , first to the shearing work station  48  and then through the several previously described forming and shaping stations where the precursor tongues are strategically formed into their final shape. 
     After the shearing step has been completed, the two precursor side tongues  152  and the precursor top and bottom tongues  154  and  156  not only vary in width, but also, as shown in  FIG. 24 , vary in thickness with the tongues being thicker at their fixed or proximal ends thinner in a direction toward their free or distal ends. As previously discussed, by making the starting workpiece finger in a tapered and variable width configuration as shown in  FIGS. 22 and 23 , the stresses at the fixed end of the formed contacts can be markedly reduced and the tendency of the bending stress to propagate the shear considerably lessened. 
     Having now described the invention in detail in accordance with the requirements of the patent statutes, those skilled in this art will have no difficulty in making changes and modifications in the individual parts or their relative assembly in order to meet specific requirements or conditions. Such changes and modifications may be made without departing from the scope and spirit of the invention, as set forth in the following claims.

Technology Classification (CPC): 8