Abstract:
A wire fastener for use in providing a strong, slip resistant structure in which the fastener includes a hump which the wire passes over and includes ears on either side of the hump which are crimped over the wire on both sides of the hump to cause the wire to bend in a double “s” shape over the hump.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention is in the field of wire fasteners and more particularly to terminal fasteners for use with non-malleable wire. 
     2. Description of the Prior Art 
     Many wire fasteners are available in the prior art. The majority of prior art fasteners are for malleable wire such as copper. Some such fasteners include a pair of foldable members which are pressed down around the wire to hold it in place and may include a terminal member such as a loop which may be positioned around a binding post, bolt or other such device connected to a circuit to which connection is desired to be made. Stainless steel fasteners are often preferred to provide a strong long lasting and corrosion resistant fastener that makes good electrical contact. Generally, the wire is caused to deform around a portion of the stainless steel fastener to prevent slippage. 
     Such fasteners encounter difficulties when they are applied to a non-malleable wire such as tungsten since the non-malleable wire does not deform to provide a non-slipping connection to the fastener. Thus, when it is required that the wire be able to withstand axial forces or pull, the wire can slip out of the fastener and electric contact will be broken. Techniques such as welding are complicated and quite costly. 
     SUMMARY OF THE INVENTION 
     Although the present invention has utility for providing fasteners with various types of wire, the primary utility is intended for providing an electrical fastener for use with a non-malleable wire such as 0.008-inch tungsten, which can resist an axial pull of at least eight pounds without breaking contact. This is accomplished using simple production equipment to minimize cost and maximize ease of manufacture. Specifically, a double “S” shaped or “camel back” shaped mechanical attachment along the axis of the wire is used with the wire being crimped on either side thereof. To assure further pull resistance, the wire is passed in “camel back” fashion over a hump formed by a folded-over spring member which has small burrs that grip the wire at the contact points and the wire is forced perpendicular to its length against the burrs aided by the spring force of the spring member to significantly increase the contact force of the wire against the spring member. The ears that are folded over the wire and crimped on either side of the hump are positioned relatively close to the hump to cause a tight bend in the wire around the hump and thus force it into the double “S” shape that allows the assembly to resist separation even when extremely high axial pull forces are applied. The two pairs of ears are an integral part of the terminal and located directly across from each other. In order to prevent overlapping of the ears when folded, they may be shaped with, for example, a forty-five degree angle, so that when folded and crimped, the forty-five degree edges are close but not overlapping each other. The meshing reduces the leverage distance from the captured wire to the fold of each ear which results in greater force required to lift the ears away from the terminal body thus an increase of the resistance to pulling force and improving the overall wire to terminal axial pull strength. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows a top view of a series of terminal blanks stamped from a sheet metal strip; 
     FIG. 1 a  shows a view of FIG. 1 taken along sight A—A; 
     FIG. 2 shows a single fastener cut from the series of FIG. 1; 
     FIG. 2 a  shows a view of FIG. 2 taken along sight B—B; 
     FIG. 3 shows the fastener of FIG. 2 with the spring like hump folded over; 
     FIG. 3 a  shows a view of FIG. 3 taken along sight C—C; 
     FIG. 4 shows the fastener of FIG. 3 with the ears bent up and the wire positioned for capture; 
     FIG. 4 a  shows a view of FIG. 4 taken along sight D—D; 
     FIG. 5 shows the fastener of FIG. 4 with the ears crimped on either side of the hump to capture the wire; 
     FIG. 5 a  shows a view of FIG. 5 taken along sight E—E; and, 
     FIG. 6 shows an enlarged cross-section view of FIG. 5 taken along section F—F. 
    
    
     DETAILED DESCRIPTION 
     Referring to FIG. 1, a continuous strip of fasteners  10  is shown with individual fasteners  12 ,  14 ,  16  and  18  interconnected by portions  22 ,  24  and  26 . The fasteners are shown having a length generally extending along axes shown by arrows  20 ,  22 ,  24  and  26  may be formed from half hard stainless steel stock, which may be wound for storage on a reel (not shown). It should be understood that the punch press which stamps the strip of fasteners  10  leaves tiny burrs of metal on the down side of the metal or, as shown in FIG. 1, into the plane of the drawing. These burrs aid in the holding of the wire as will be explained. 
     Each fastener,  12 ,  14 ,  16  and  18  includes the same elements and for simplicity, only fastener  12  will be described. Fastener  12  includes an eyelet portion  12   a , for use in attachment to a binding post or connector to make electrical contact with a circuit (not shown). Below the eyelet portions  12   a , oppositely disposed semi-circular cutout portions  12   b   1  and  12   b   2  are shown for use with dowel shaped members (not shown) to position or “pilot” the fasteners during their attachment to a wire. Below the cutouts  12   b   1  and  12   b   2 , a first pair of ears  12   c   1  and  12   c   2  are formed with slanting edges to prevent overlap when folded as will be explained. Below the ears  12   c   1  and  12   c   2 , the connector includes a tab  12   d  which will be folded over to provide a spring like hump to push against the wire as will be described. Finally, below the tab  12   d , a second pair of ears  12   e   1  and  12   e   2  are formed, like the first pair of ears  12   c   1  and  12   c   2 , with slanting edges to prevent overlap when folded. 
     The fasteners  14 ,  16  and  18  as well as others (not shown) are formed in the same way as fastener  12 . When they are to be attached to a wire, they will be separated along dotted lines such as  12   f   1  and  12   f   2  for fastener  12  during an assembly process which would normally be performed in a straight forward assembly machine (not shown) but, for purposes of clarity, the process will be described in connection with FIGS. 2-6, for the individual fastener  12  as if performed manually. 
     In FIGS. 2 and 2 a , the individual fastener  12  of FIG. 1 is shown separated from the others in the strip. A dotted line  28  is shown across tab  12   d  to show where a bend is to be performed. 
     In FIGS. 3 and 3 a , the bend along line  28  of FIG. 2 has been performed resulting in tab  12   d  bending over the rest of the fastener. In FIG. 3 a , tab  12   d  is shown angling slightly upwards and to the right as seen in FIG. 3 a . This ramp formed by tab  12   d  provides a springiness which will be used to increase the holding power of the fastener, as will be described. Of course, a ramp is not required to provide springiness. For example, the tab could be bent in a radius so that it extended back toward the fastener. It is desirable that the tab be bent so as not come to rest against the fastener and at least some space exist between the tab and the fastener to provide springiness. 
     In FIGS. 4 and 4 a , the ears  12   c   1 ,  12   c   2 ,  12   e   1  and  12   e   2  are shown folded upward as best seen in FIG. 4 a , and a wire  30  has been laid in the channel formed by the ears  12   c   1 ,  12   c   2 ,  12   e   1  and  12   e   2  and extends generally along axis  20  across the tab  12   d.    
     In FIGS. 5 and 5 a , the ears  12   c   1  and  12   c   2  have been crimped over the upper part of wire  30  above the hump formed by tab  12   d  and the ears  12   e   1  and  12   e   2  have been crimped over the lower part of wire  30  below the hump formed by tab  12   d . It is seen that the crimping of ears  12   c   1 ,  12   c   2 ,  12   e   1  and  12   e   2  on either side of the hump formed by tab  12   d  forces the wire  30  into a double “S” shaped bend as will be best seen in FIG.  6 . 
     FIG. 6 is enlarged for clarity and shows the fastener  12  of FIG. 5 in cross-section taken along section F—F. It is seen that the folded ears  12   c   1  and  12   e   1  are fairly close to the folded tab  12   d  so that the double “S” shaped hump is rather tight to increase the holding power provided. It is also seen the tab  12   d  has been folded so that the burrs which were formed by the stamping process and which extended into the plane of the drawings, now point away from the plane of the drawings and toward wire  30  so as to tend to “dig in” and increase the grip formed between the tab  12   d  and the wire  30 . 
     The resulting fastener is strong and easy to produce. It resists pulling forces applied between the fastener and the wire and is far simpler in construction that other fasteners presently available. It should be understood that many modifications to the apparatus and process herein described will become apparent to those having ordinary skill in the art. For example, while the wire has been described as being composed of tungsten and the fastener as being composed of stainless steel, other materials may be used. Also, while the process was described as being performed on a single fastener as if done manually, the automatic assembly of the fasteners sand the wires will be more commonly performed. Finally, while the specific shapes of the ears with forty-five degree sides and the tab of generally rectangular cross section, have been described, other shapes may be used without departing from the spirit of the invention. We therefore do not wish to be limited to the specific disclosures used in connection with describing the preferred embodiment.