Electrical contact crimp ear serration

[0001] Not Applicable

[0002] Not Applicable

[0003] Not Applicable

[0004] 1. Field of the Invention

[0005] The present invention relates to electrical contacts, more particularly, to methods of manufacturing crimp ears.

[0006] 2. Description of the Related Art

[0007] 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.

[0008] 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'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.

[0009] 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.

[0010] 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.

[0011] 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.

[0012] Other objects of the present invention will become apparent in light of the following drawings and detailed description of the invention.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027]

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

[0028] 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.

[0029] 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.

[0030] Further, testing under the guidelines of UL standards 310 and 486A 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 8A–8C 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.

[0031] 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.

[0032] 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.

[0033] Thus it has been shown and described a crimp ear serration, which satisfies the objects set forth above.

[0034] 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.