Abstract:
A variable plug of a connector has a modular construction and includes a base module with cable connection and plug contacts. Depending on the desired total number of contacts of the plug, one or more add-on modules having additional plug contacts can be mechanically and electrically connected with the base module.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present invention relates to a plug of a connector which is designed to have a variable number of plug contacts. 
         [0002]    Increasingly, new technologies such as bus systems, fiber optic systems and more complex plug systems require innovative test strategies for electrical and non-electrical tests. The demand for higher throughput in mass production has to be weighed against small batch sizes and the demand for short set-up times. 
         [0003]    The test specification may require a simple check of the connection, but may also require a high-voltage test to detect insulation faults. Furthermore, a test of electronic and electromechanical components and assemblies in wire harnesses may be requested. 
         [0004]    The tests use plug-in connectors. The number of plug contacts must correspond to the test plug. This means that a large number of different connectors must be provided. For this reason, modular plug-in connectors exist which produce a plug adapted to the requirement through expansion of basic elements. These are laboriously assembled by screw connections or must be disassembled in a complex process when parts subject to wear must be replaced. This in turn results in financial and logistical expenditures. 
         [0005]    It would therefore be desirable and advantageous to obviate prior art shortcomings and to provide an improved plug of a connector that can be assembled in a less expensive and less complex manner. 
       SUMMARY OF THE INVENTION 
       [0006]    According to an aspect of the invention, a variable plug of a connector has a modularly constructed base module having a cable connection and first plug contacts. One or more add-on modules have second plug contacts and are constructed to be mechanically and electrically connected with the base module, wherein a total number of the add-on modules depends on a desired total number of contacts. 
         [0007]    The variable plug of a plug-in connector according to the invention has a modular design and is composed of a base module with a cable connection and plug contacts. 
         [0008]    Depending on the desired total number of contacts, one or more add-on modules provided with plug contacts may be connected to the base module. The base module is preferably composed of a base shell and a cover. 
         [0009]    The cable relief is inserted in the base shell, and a printed circuit board carrying the plug contacts is inserted between the base shell and the cover and secured when the base shell and the cover are joined. 
         [0010]    The cover of the base module has detent hooks which enter in corresponding recesses of the base shell arranged transversely to the longitudinal extent of the base shell when the base shell and the cover are joined. 
         [0011]    Pin-shaped locking devices, which extend in the longitudinal direction and are open to the outside and engage behind the detent hooks when inserted into recess channels of the base shell connecting the aforementioned recesses, are provided for positive locking of the cover, thereby locking the cover. 
         [0012]    A corresponding retaining spring having a projection is arranged in the recess channels, in which the latches are inserted, so that the projection engages into a correspondingly shaped portion disposed on the locking device in the inserted position of the locking device and fixes the position. A notch is introduced into the end of the locking device facing the insertion side of the locking device, whereas an indentation is introduced into the outer contour of the base shell at the beginning of the recess channel in which the locking device is inserted. Both measures are designed to facilitate handling when removing the locking device. 
         [0013]    To increase the number of contacts of the plug, add-on modules are provided that can be connected with the basic module. The add-on modules are composed of a middle shell which, as also the cover, is provided on the side facing the base side of the shell with detent hooks for connection with the base shell during assembly, and on the opposite side, as also the base shell, is provided with recesses and recess channels. The base shell is joined with one or more middle shells in the same manner as described above in conjunction with joining of the base shell and the cover by locking devices. Lastly, the cover is attached to the outermost middle shell in the same manner. 
         [0014]    Preferably, a mandrel is provided on the base shell and on each middle shell transversely to their longitudinal extent wherein the mandrel engages in an opening provided in the printed circuit board for receiving and centering the printed circuit board. The printed circuit board is mounted so as to allow a predetermined clearance between the printed circuit board and the base shell or middle shell for compensating a vertical and horizontal tolerance of the contacts. 
         [0015]    Each middle shell has a printed circuit board carrying the contacts as well as an opening for the passage of the cable wires to the contacts of the middle shells. 
         [0016]    Preferably, the base shell, the middle shells and the cover are made of plastic. 
         [0017]    The retaining springs securing the locking devices are preferably incorporated in the geometry and material of the base shell and of the middle shells, i.e. they are made of the same material as each of the modules. 
         [0018]    The outer contour of the housing parts base shell, middle shells and cover may be provided with a rectangular spring for absorbing tensile forces of a completely inserted system, wherein the corresponding groove may be arranged in a rail connected to the mating connector. 
         [0019]    On the outer contour of the housing parts base shell, middle shells and cover, a handle-shaped extension may be provided on the cable entry side for handling of the connector. 
         [0020]    Advantageously, the base shell has in the region of the printed-circuit-board receptacle a recess configured to receive an ID chip located on the printed circuit board for self-identification. 
         [0021]    A commercially available printed-circuit-board connector of the type Card Edge may be used as a mating connector of the circuit connector. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         [0022]    Other features and advantages of the present invention will be more readily apparent upon reading the following description of currently preferred exemplified embodiments of the invention with reference to the accompanying drawing, in which: 
           [0023]      FIG. 1 : shows the base shell of a connector according to the present invention from the open side, 
           [0024]      FIG. 2 : shows the base shell from the cable-entry side 
           [0025]      FIG. 3  shows the detail of  FIG. 1 , 
           [0026]      FIG. 4  shows a perspective view of the base shell, 
           [0027]      FIG. 5  shows the middle shell of a connector according to the present invention from the outer side, 
           [0028]      FIG. 6  shows the middle shell from the cable-entry side 
           [0029]      FIG. 7  the detail of  FIG. 5 , 
           [0030]      FIG. 8  shows a perspective view of the middle shell, 
           [0031]      FIG. 9  shows a perspective view of the cover of a connector according to the present invention, 
           [0032]      FIG. 10  shows a connector system according to the present invention with a base shell and two middle shells, 
           [0033]      FIG. 11  shows an exploded view of a connector system with five middle shells, and 
           [0034]      FIG. 12  shows a pin-shaped locking device. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0035]    Throughout all the figures, same or corresponding elements may generally be indicated by same reference numerals. These depicted embodiments are to be understood as illustrative of the invention and not as limiting in any way. It should also be understood that the figures are not necessarily to scale and that the embodiments are sometimes illustrated by graphic symbols, phantom lines, diagrammatic representations and fragmentary views. In certain instances, details which are not necessary for an understanding of the present invention or which render other details difficult to perceive may have been omitted. 
         [0036]    Turning now to the drawing, and in particular to  FIG. 1 , there is shown a base shell with four recesses  2  disposed on the upper and lower inner side, in which the detent hooks  7  of the middle shell  9  ( FIG. 6 ) or of the cover  10  ( FIG. 9 ) can engage transversely of the longitudinal extension of the shell during assembly. The retaining springs  5  ( FIGS. 3 and 4 ) with the engaging projections  11  ( FIG. 3 ) that engage in the inserted state of the locking device  4  in the recess  6  ( FIG. 12 ) on the locking device  4  and secure these, are located in the recess channel  3  which extends in the longitudinal direction of the shell and into which the pin-shaped locking devices  4  ( FIGS. 11 and 12 ) are inserted in the direction A for positively securing the middle shell  9  ( FIG. 6 ) and the cover  10  ( FIG. 9 ), respectively. 
         [0037]      FIGS. 6 ,  8  and  9  clearly show the detent hooks  7  disposed on the middle shell  9  and the cover  10 , respectively, while  FIGS. 5 and 8  clearly show the recesses  2  in the transverse direction of the middle shell and the recess channels  3  in the longitudinal direction of the middle shell  9 . 
         [0038]      FIGS. 3 and 7  show each the retaining spring  5  with its projection  11  arranged in the recess  2 ,  3 . 
         [0039]      FIG. 10  shows a connector system with a base shell  1  and two middle shells  9 . The plug contacts of the printed circuit board are labeled as  12 . 
         [0040]      FIGS. 4 and 5  show the mandrel  13  on which the printed circuit board  14  ( FIG. 11 ) carrying the plug contacts  12  is affixed by way of a borehole in the printed circuit board. 
         [0041]      FIG. 11  also shows for the cable relief  15  which is secured in the plug when the base shell  1  and the middle shell  9  and the cover  10 , respectively, are joined. 
         [0042]      FIG. 12  shows a pin-shaped locking device  4  with the recess  6 , in which the retaining spring  5  engages, and with the notch  16  to facilitate removal of the locking device  4  from the recess channel  3 . 
         [0043]    A recess  8  ( FIG. 8 ) located on the side of the shell recess channels  3  extending in the longitudinal direction of the shells and facing the cable is provided in the base shell and in each of the middle shells, which also serves to facilitate removal of the locking device. 
         [0044]    A handle-shaped extension ( 17 ) on all housing parts ( 1 ,  9 ,  10 ) improves the handling of the plug. 
         [0045]    While the invention has been illustrated and described in connection with currently preferred embodiments shown and described in detail, it is not intended to be limited to the details shown since various modifications and structural changes may be made without departing in any way from the spirit and scope of the present invention. The embodiments were chosen and described in order to explain the principles of the invention and practical application to thereby enable a person skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated. 
         [0046]    What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims and includes equivalents of the elements recited therein: