Abstract:
An electrical contact crimp ear serration comprised of a plurality of teeth where each tooth has a cross-sectional profile comprising a leading face extending upwardly to an apex from the crimp ear surface, a central face extending downwardly from the apex to a valley below the crimp ear surface, and a trailing face extending upwardly from the valley to the crimp ear.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
   Not Applicable 
   STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
   Not Applicable 
   REFERENCE TO A SEQUENCE LISTING, A TABLE, OR A COMPUTER PROGRAM LISTING COMPACT DISK APPENDIX 
   Not Applicable 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to electrical contacts, more particularly, to methods of manufacturing crimp ears. 
   2. Description of the Related Art 
   The typical electrical contact has a contact portion and a crimp ear for attaching a wire. The inner surface of the open barrel or closed barrel crimp ear is serrated to provide a more secure wire attachment, where the serration may take the form of grooves or ridges. The simplest form is a groove that extends laterally across the face of the crimp ear to indent and clinch the outer layers of multi-stranded or single bare wire. Other forms are known in the art for providing a better bare wire connection or that pierce insulation. 
   A number of different serration cross-sectional profiles are known in the art. U.S. Pat. No. 3,549,786, issued to Kuo, discloses a serration that rises from a base below the crimp ear surface to a sharp edge above the crimp ear surface. The profile has a flat face perpendicular to the crimp ear surface and a face that curves downwardly and outwardly from the sharp edge. U.S. Pat. No. 3,735,331, issued to O&#39;Donnell et al., discloses a groove below the surface of the crimp ear. The profile has a face that slopes into the groove and slightly away from the center of the groove and another face the slopes into the groove and substantially toward the center of the groove. U.S. Pat. No. 3,812,448, issued to Haitmanek, discloses a serration with several different profiles. The common thread is that one face extends upwardly from the crimp ear surface while the other face extends upwardly from below the crimp ear surface. The two faces meet at a point. 
   BRIEF SUMMARY OF THE INVENTION 
   An object of the present invention is to provide a crimp ear serration that provides a secure electrical and mechanical attachment to a bare single or a multi-stranded bare wire. 
   The present invention is a serration for use on an electrical contact crimp ear. The serration is comprised of numerous teeth, each with an apex and a valley formed in the crimp ear surface. The arrangement of the teeth to form the serration depends upon the particular application. 
   The basic profile of the tooth is a saw tooth. A leading face ramps upwardly to an apex. From the apex, a central face extends downwardly to a valley below the crimp ear surface. A trailing face ramps up to the crimp ear surface. There may be a gap between the trailing face and the leading face of adjacent teeth. Preferably, the gap is minimized by adding rows of teeth if necessary. 
   Other objects of the present invention will become apparent in light of the following drawings and detailed description of the invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a fuller understanding of the nature and object of the present invention, reference is made to the accompanying drawings, wherein: 
       FIG. 1  is a drawing of an electrical contact with a crimp ear provided with a configuration of the serration of the present invention; 
       FIG. 2  is an enlarged schematic of a crimp ear provided with one configuration of the serration of the present invention; 
       FIG. 3  is an enlarged schematic of a crimp ear provided with another configuration of the serration of the present invention; 
       FIG. 4  is the cross-sectional profile of the crimp ear serration of  FIG. 1  along the line  4 — 4 ; 
       FIG. 5  is a photograph of a crimp ear provided with the serration of the present invention; 
       FIG. 6  is a photograph of the cross-sectional profile of the teeth of  FIG. 4 ; 
       FIGS. 7A–7C  are graphs comparing the serration of the present invention with the industry standard using 16 AWG wire; and 
       FIGS. 8A–8C  are graphs comparing the serration of the present invention with the industry standard using 18 AWG wire. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The present invention is a crimp ear serration  10  for use on the crimp ear  8  of an electrical contact  6 . The serration  10  is comprised of numerous teeth  12 , as shown in  FIG. 1 . As seen in  FIG. 4 , each tooth  12  has an apex  14  and a valley  16  (collectively, features) formed in the nominal surface  20  of the crimp ear  8 , that is, the plane of the surface of the crimp ear  8  prior to formation of the serration  10 . The number, size, and position of the teeth  12  vary depending on the particular application. The serration  10  can be used as an alternative to conventional serrations on many types of electrical connectors. 
     FIGS. 2 ,  3 , and  5  show two configurations of how the teeth  12  can be arranged to form the serration  10  on the crimp ear  8 . In  FIGS. 2 and 5 , the teeth  12  are arranged in aligned horizontal rows  19 . In  FIG. 3 , the teeth  12  are arranged in staggered horizontal rows. The present invention contemplates the use of any arrangement of teeth  12  that is suitable for the intended use. Further, the present invention does not intend that it be limited to any length  18  for the teeth  12 . The present figures show a relatively short tooth  12 . The present invention contemplates, however, that the tooth  12  may be long enough to extend completely across the face of the crimp ear surface  20 . 
   The basic profile shape of the tooth  10  is that of a saw tooth, as can be seen in the schematic of  FIG. 4  and the photograph of  FIG. 6 , and spans length  24 . From left to right, a leading face  30  starts upwardly from the nominal crimp ear surface  20  and curves slightly toward horizontal, for an average angle of about 18 to 28 degrees from the nominal surface  20 . At the apex  14 , it curves sharply downwardly, as at  32 , to a central face  34 , which is at an average angle of about 82 to 90 degrees from the nominal surface  20 . The central face  34  is more than twice the height that the apex  14  is from the nominal surface  20 , which means that the central face  34  ends in a valley  16  below the nominal surface  20  at a depth of more than the height of the apex. From the valley  16 , it curves upwardly, as at  36 , to a trailing face  38 , that ramps upwardly to the nominal surface  20  at an average angle of about 10 to 18 degrees from horizontal. Alternatively, the valley curve  36  may be very sharp, with little or no radius. 
     FIG. 4  shows that there is a gap  40  between adjacent teeth  12  that is short relative to the length of each tooth  12 . However, the present invention contemplates that the gap  40  may be any length. There may be no gap, that is, the teeth  12  abut or even overlap each other, or the gap  40  may be larger relative to the length of the teeth  12 . The preference is to keep the gap to a minimal size. Thus, so rather than increasing the spacing for larger crimp ears, the preference is to add additional rows of teeth and keep the gap to a minimum. 
   Table I lists typical dimensions for the various surfaces of a tooth  12  designed for wire sizes ranging from 22 AWG to 10 AWG. The table lists the reference numerals in  FIG. 4  and the corresponding ranges of dimensions. The dimensions can vary proportionately depending upon the intended size of the tooth  12 . 
   
     
       
             
             
           
         
             
               TABLE I 
             
             
                 
             
             
               Reference 
                 
             
             
               Numeral 
               Dimension 
             
             
                 
             
           
           
             
               24 
               25–30 mils 
             
             
               30 
                8–12 mils length with an 18°–28° slope 
             
             
               32 
                2–3 mils radius 
             
             
               34 
                6–10 mils with an 82°–90° slope 
             
             
               36 
                0–4 mils radius 
             
             
               38 
               18–22 mils length with a 10°–18° slope 
             
             
               40 
                0–30 mils 
             
             
                 
             
           
        
       
     
   
   The serration  10  of the present invention has several advantages when compared to the industry standard serration consisting of parallel grooves that extend laterally across the face of the crimp ear. First, the apexes  14  and valleys  16  of the serration  10 , being both below and above the crimp ear surface  20 , cause deformation to the wire material as it conforms to the shape of the crimp ear serration. This deformation increases the surface contact area between the joining materials, thus improving both the electrical and mechanical connections. 
   Also, the profile of the present invention results in no loss of material mass, whereas the industry standard serration has a reduction in material mass due to forming a groove in the crimp ear surface. This reduction in material mass could be significant as the crimp height approaches the maximum crimp height limits. 
   Further, testing under the guidelines of UL standards  310  and  486 A show that the serration  10  of the present invention is superior through a broader range of crimp heights than the industry standard serration.  FIGS. 7A–7C  and  8 A– 8 C show graphical test data comparing a crimp employing the serration  10  of the present invention to the industry standard serration. The tests were conducted with three different standard crimp materials (tin brass, nickel-plated steel, and copper) using two different wire sizes.  FIGS. 7A–7C  show test results for 16 AWG wire and  FIGS. 8A–8C  show test results for 18 AWG wire. In general, for smaller crimp heights, the serration  10  of the present invention is comparable to the industry standard. For larger crimp heights, the test date show that the serration  10  of the present invention is significantly stronger than the industry standard serration. 
   The test data show that the serration  10  of the present invention is less sensitive to variations in the crimping or attaching process. The protruding features of the serration provide greater deformation to the conductor at broader crimp height ranges. The typical crimp height range is +/−2 mils. The serration allows an upward shift +2 mils of the nominal crimp height settings, combined with a broader crimp height range of +/−4 mils. Less crimping force is required to provide a good crimp, resulting in less wear and tear to assembly and application equipment. 
   The dimensional and visual qualities of the contact are improved. No coining or swaging is required to form the serration  10 , which virtually eliminates material growth and work hardening. 
   Thus it has been shown and described a crimp ear serration, which satisfies the objects set forth above. 
   Since certain changes may be made in the present disclosure without departing from the scope of the present invention, it is intended that all matter described in the foregoing specification and shown in the accompanying drawings be interpreted as illustrative and not in a limiting sense.