Universal terminal block connector
BACKGROUND OF THE INVENTION 
     Field Of The Invention 
     The present invention relates to connectors. More specifically, the present invention is directed to a connector for an electrical terminal block. 
     SUMMARY OF THE INVENTION 
     The object of the present invention is to provide an improved electrical terminal block connector. 
     In accomplishing this and other objects, there has been provided, in accordance with the present invention, a terminal block connector having a first and a second nut with the first nut having a first diameter thread and the second nut having a second diameter thread smaller than the first diameter thread. The two nuts are coaxially arranged and are held captive in a coaxial recess with the large diameter nut being positioned at the entrance to the recess. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A better understanding of the present invention may be had when the following detailed description is read in connection with the accompanying drawings, in which: 
     FIG. 1 is a cross-sectional illustration of a terminal block embodying an example of the present invention, 
     FIG. 2 is a cross-sectional illustration showing the operation of the example of the present invention shown in FIG. 1 with a first diameter machine screw, 
     FIG. 3 is a cross-sectional illustration showing the operation of the example of the present invention shown in FIG. 1 with a second diameter machine screw and 
     FIG. 4 is a cross-sectional illustration of a second example of an embodiment of the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIG. 1 in more detail, there is shown a cross-sectional illustration of an example of the present invention used for connecting an electrical lead 2 to an electrically conductive plate 4, e.g., a portion of a so-called barrier strip or terminal block. The electrically conductive plate 4 is attached to an insulating substrate by any suitable means (not shown). The substrate 6 has a recess 8 therein which is arranged to rotationally captivate a first nut 10 and a second nut 12 therein. The first and the second nuts 10, 12 are arranged coaxially with each other and with an entrance 13 to the recess 8. The depth of the recess 8 is greater than the combined thickness of the nuts 10, 12 to allow the first, or inner, nut 10 to move away from the second, or outer, nut 12. However, the recess 8 is arranged to frictionally engage the first nut 10 to initially retain it against the second nut 12. The recess 8 may also be proportioned to frictionally engage the second nut 12 to maintain it at the entrance of the recess 8 after the first nut 10 has been displaced toward the bottom of the recess 8. A machine screw 14 is positioned to pass through a hole 16 in the electrical lead 2, a hole 18 in the plate 4 and the entrance 13 of the recess 8. Specifically, the threaded shank 20 of the machine screw 14 is arranged to enter the recess 8 to engage either one of the nuts 10, 12 held in the recess 8. Concurrently, the head 21 of the machine screw 14 is effective to urge the lead 2 against the plate 4 to secure the lead 2 to the plate 4. 
     In FIG. 2, there is shown a cross-sectional illustration of the operation of the example of the present invention shown in FIG. 1 with a machine screw 14A having a first diameter threaded shank 20A. The second nut 12 is arranged to have an internally threaded second diameter 22 which is larger than the internally threaded first diameter 24 of the first nut 10. The coaxial orientation of the first and the second nuts 10, 12 allows the threaded shank 20A of the machine screw 14A to pass through the larger thread diameter 22 of the second nut 12 and to engage the smaller thread diameter 24 of the first nut 10. 
     In FIG. 3, there is shown a cross-sectional illustration of the operation of the example of the present invention shown in FIG. 1 using a machine screw 14B having a second diameter shank 20B. In this operation, the larger threaded shank 20B of the machine screw 14B would engage the larger second diameter of the second nut 12 and would be unable to enter the internally threaded first diameter 24 of the first nut 10. In this embodiment, the entire length of the shank 20B of the machine screw 14B shown in FIG. 3 is accommodated by allowing the end of the shank 20B projecting past the second nut 12 to displace the first nut 10 toward the bottom of the recess 8 since the recess 8 has a depth greater than the combined thickness of the nuts 10, 12. In both of these operations as shown in FIGS. 2 and 3, the engaging of the threaded shank 20 of the machine screw 14 with one of the nuts 10, 12 would enable the lead 2 to be securely attached to the metal plate 4 while accommodating a substantial variation in the thickness of the lead 2. The machine screw 14 and the nuts 10, 12 are preferably made from metal although electrically insulating materials, e.g., plastics, could be used therefor. 
     In FIG. 4, there is shown a second example of an embodiment of the present invention wherein the recess 8A has a greater depth than the recess 8 shown in FIG. 1 and the first nut 10 has a substantially free sliding fit in the recess 8A. The first and second nuts 10 and 12 are positioned in the recess 8A and are held against the metal plate 4 by a spring 30 located within the recess between the first nut 10 and the bottom of the recess 8A. Thus, the expanded length of the spring 30 is effective to maintain the nuts 10, 12 at the entrance end 13 of the recess 8A. In this embodiment, the entire length of the shank 20B of the machine screw 14B shown in FIG. 3 is accommodated by allowing the end of the shank 20B projecting past the second nut 12 to displace the first nut 10 toward the bottom of the recess 8 against the pressure of the spring 30 since the recess 8 has a depth greater than the combined thickness of the nuts 10, 12 and the compressed length of the spring 30. Conversely, a screw shank 20A shown in FIG. 2 would engage the first nut 10 without a displacement of the first nut 10 against the pressure of the spring 30. In other words, the engagement of the lower or first nut 10 is achieved by a screw shank 20A passing through the upper nut 12 while the same length of the shank 20B which would engage the upper or second nut 12 would also project out of the second nut 12 and would simply displace the lower nut 10 against the pressure of the spring 30 as the end of the shank 20B emerged from the adjacent face of the upper nut 12. Upon a withdrawal of the machine screw 14 from a position engaging the nuts 10, 12, the spring 30 would restore the nuts 10, 12 to their stacked position at the entrance of the recess 8A for subsequent use. In either example of the present invention as shown in FIGS. 1 and 4, the nuts 10 and 12 can have either the same type of thread, e.g., SAE, or different types of threads, e.g., SAE and metric, to further enhance the universality of the present invention. 
     Accordingly, it may be seen, that there has been provided, an improved electrical terminal block connector.