Abstract:
An electrical plug blade according to a first embodiment the invention includes a blade portion, a wire cradle, two crimp ears, and centering means for centering a stranded wire within the wire cradle. The centering means is preferably in the form of two centering nubs projecting above the base of the wire cradle. Another embodiment of the invention includes a padded range-style blade portion specifically designed for use in 30 to 60 ampere applications. This embodiment can be constructed both with and without the centering means in the wire cradle.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This is a §111(a) application relating to U.S. application Ser. No. 60/076,134 filed Feb. 27, 1998. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to electrical plug blades and, more particularly, to electrical plug blades of a padded and/or a non-padded type. 
     BACKGROUND OF THE INVENTION 
     The type of electrical plug blade wire crimp known in the art (as shown in FIG. 1) has a wire cradle with two outwardly extending crimp ears and a flat bottom surface on which a stranded wire lies. The stranded wire is often not centered between the crimp ears prior to crimping, leading to finished crimps that are either lop-sided or that have not captured all of the wire strands. Either of these imperfect crimps could lead to contact failure between the stranded wire and the plug blade and a potential failure of the Underwriters&#39; Laboratories standard pull test, leading to overall plug failure and to a potentially hazardous electrical condition for the user. 
     There is presently a need for a wire crimp design that provides for improved wire termination and crimping, so as to avoid the problems of the prior art. There is also a need for a padded range-style electrical plug blade for use in 30 to 60 ampere applications, as the prior art is limited to padded electrical plug blades for use in 15 ampere applications. The embodiments of the present invention satisfy those needs. 
     SUMMARY OF THE INVENTION 
     One embodiment of the electrical plug blades of the present invention has a wire cradle with a base and two outwardly extending crimp ears, the improvement over the prior art being that there is a depression in the base of the wire cradle, which allows for easy and automatic self-centering of a wire within the wire cradle before crimping. The depression is created by a punch in the production die, which deforms the base of the wire cradle, creating two centering nubs, each of which is located adjacent to one of the crimp ears. 
     When a wire is laid in the wire cradle, it is automatically self-centered therein by the shape of the centering nubs, which slope downward toward the base of the wire cradle. The crimp ears can then be rolled around the wire, finishing the crimp and thereby firmly attaching the wire to the electrical plug blade. 
     In an another embodiment of the present invention, the electrical plug blade is of the padded range-style type, and is designed for use in applications from 30 to 60 amperes. This padded range-style electrical plug blade can be constructed either with or without the self-centering wire cradle described above. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a better understanding of the present invention, reference is made to the following detailed description of three exemplary embodiments considered in conjunction with the accompanying drawings, in which: 
     FIG. 1 is a side elevational view of an electrical plug blade typical of the prior art; 
     FIG. 2 is a side elevational view of a non-padded electrical plug blade constructed in accordance with one embodiment of the present invention; 
     FIG. 3 is a partial cross-sectional, side elevational view of a padded electrical plug blade constructed in accordance with a second embodiment of the present invention; 
     FIG. 4 is a top view of the embodiment shown in FIG. 3; 
     FIG. 5 is a rear elevational view of the embodiment shown in FIG. 3; 
     FIG. 6 is a partial side elevational view of a padded electrical plug blade constructed in accordance with a third embodiment of the present invention; and 
     FIG. 7 is a partial top view of the embodiment shown in FIG.  6 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 shows a prior art electrical plug blade  10 , with a blade portion  12  and a wire cradle  14 , which is surrounded on two sides by outwardly extending crimp ears  16 . As can be seen in FIG. 1, the wire cradle  14  has a flat base  18 , which does not allow for the self-centering of a stranded wire between the crimp ears  16 . 
     FIG. 2 depicts an electrical plug blade equipped with a self-centering wire crimp and constructed in accordance with one embodiment of the present invention. To facilitate consideration and discussion, elements illustrated in FIG. 2 which correspond to the elements described above with respect to FIG. 1 have been designated by corresponding reference numerals increased by one hundred. 
     Referring now to FIG. 2, an electrical plug blade  110  is comprised of a blade portion  112  and a wire cradle  114 , which is surrounded on two sides by outwardly extending crimp ears  116 . A base  118  of the wire cradle  114  has two centering nubs  120 , with each of the centering nubs  120  being located adjacent to one of the crimp ears  116 . The centering nubs  120  are shaped such that regardless of where a stranded wire  121  (shown in phantom) is placed in the wire cradle  114 , the stranded wire  121  will self-center in the wire cradle  114  between the two centering nubs  120 . 
     The centering nubs  120  are formed by a punch as the plug blade  110  progresses through the production die. The section of the blade portion  112  that extends into the wire cradle  114  is deformed by the punch; there is no additional material used to create the centering nubs  120 . The centering of the stranded wire  121  between the centering nubs  120  leads to improved overall crimping and termination of the stranded wire  121 , thereby reducing the chances of encountering the existing problems of finished crimps that are either lop-sided or that have not captured all of the wire strands. 
     FIGS. 3,  4 , and  5  illustrate a padded electrical plug blade equipped with a self-centering wire crimp and constructed in accordance with a second embodiment of the present invention. To facilitate consideration and discussion, elements illustrated in FIGS. 3,  4 , and  5  which correspond to the elements described above with respect to FIG. 2 have been designated by corresponding reference numerals increased by one hundred. The embodiment of FIGS. 3,  4 , and  5  is constructed and designed for use in the same manner as the embodiment of FIG. 2, unless otherwise stated. 
     Referring now to FIGS. 3,  4 , and  5 , an electrical plug blade  210  is comprised of a blade portion  212  and a wire cradle  214 , with a section of the blade portion  212  having a pad  222  embossed into each side thereof. To maintain a uniform thickness along the length of the pads  222 , the electrical plug blade  210  has a tip  224  with an open, oval-shaped cross-section (as can be seen in the side elevational view of FIG.  3 ). A pilot hole  226 , extending completely through the electrical plug blade  210 , is provided near the tip  224  as a guide for the production die. A dimple  228  is located on each of the pads  222 , near the end of each pad  222  opposite the tip  224 , to add strength to each pad  222 , such that if the pads  222  are compressed, they will not be crushed by the compression force. 
     FIGS. 6 and 7 show a padded electrical plug blade constructed in accordance with a third embodiment of the present invention. To facilitate consideration and discussion, elements illustrated in FIGS. 6 and 7 which correspond to the elements described above with respect to FIGS. 3,  4 , and  5  have been designated by corresponding reference numerals increased by one hundred. The embodiment of FIGS. 6 and 7 is constructed and designed for use in the same manner as the embodiment of FIGS. 3,  4 , and  5 , unless otherwise stated. 
     Referring now to FIGS. 6 and 7, an electrical plug blade  310  includes a blade portion  312  having a pad  322  embossed into each side thereof. To maintain a uniform thickness along the length of the pads  322 , the electrical plug blade  310  has a tip  324  with an open, oval-shaped cross-section (as can be seen in the side elevational view of FIG.  6 ). A pilot hole  326 , extending completely through the electrical plug blade  310 , is provided near the tip  324  as a guide for the production die. A dimple  328  is located on each of the pads  322 , near the end of each pad  322  opposite the tip  324 , to add strength to each pad  322 , such that if the pads  322  are compressed, they will not be crushed by the compression force. 
     The padded blade shown in FIGS. 6 and 7 has been designed as a range-style blade to be used in 30 to 60 ampere applications. The principal differences between the padded range-style blade of the present invention and padded blades of the prior art (which are used in 15 ampere applications) are that in the present invention, the blade portion  312  is longer and wider and the thickness of the blade portion  312  and the pads  322  may be varied relative to each other, such that the combined thickness does not exceed the maximum standard thickness of 0.100 inches. In addition, this embodiment can be constructed with a standard wire crimp or with a self-centering wire crimp similar to those described above in connection with FIGS. 2-5. 
     It will be understood that the embodiments described herein are merely exemplary and that a person skilled in the art may make variations and modifications without departing from the spirit and scope of the present invention. For instance, the shape of the centering nubs could be varied, provided they are constructed such that they slope downward toward the base of the wire cradle, allowing a stranded wire to be self-centered between the two nubs. Any such variations and modifications are intended to be included within the scope of the invention as defined in the appended claims.