Patent Document

FIELD OF THE INVENTION 
     This invention is related to electrical connectors and, in particular, to connectors of the type used to connect mobile devices together for data transfer. 
     BACKGROUND OF THE INVENTION 
     This application deals with electrical connectors, the type of which could be used to connect mobile communications or mobile data processing devices together. As an example, the connector could be used to connect various accessories, such as a GPS device, to a cellular telephone. Several difficulties exist with current state of the art connectors and other connectors existing in the prior art. 
     One problem is that of contact resistance at the point where the leads of the connector contact the contacts on the printed circuit board. Because of asperities existing at a microstructure level on the material of which the leads of the connector and the contact on the circuit board are constructed, the amount of surface area that contacts the connection point for the connector is dependent upon the pressure used to hold the contact against the connection point. The contact resistance is a function of the amount of surface area of the contact which contacts the connection point, and occurs at every contact interface surface. Connectors of the prior art are constructed using two piston like contacts separated by a spring which is compressed and which pushes the piston shaped contacts against their mating contact points. The two interfaces where the spring meets the piston shaped contacts introduces additional contact interface surfaces at which contact resistance exists, thereby limiting the current carrying capacity of the connection. In some cases this may render the connection unusable for the type of accessories that one may wish to connect to the cellular phone. It is therefore desirable to eliminate the contact interfaces between the spring and the piston shaped contact surfaces to lower the contact resistance introduced thereby. 
     It is possible to eliminate the additional contact interface surfaces with a type of cantilever spring design. In this type of design, each contact contains an “S” or “Z”-shaped bend in the connection between the two contacts at opposite ends of the connector. This cantilever spring type of arrangement will force the contacts outwardly when they are compressed. However, the problem with this type of design is that the size of the hole into which the contact can be housed is limited. It is desirable to have the contacts disposed in holes of very small diameter. Often, the desired diameter holes are so small that the cantilevered type design is untenable. It is therefore necessary and desirable to use the coil type spring, while still eliminating the additional contact interface surfaces between the spring and the contacts. 
     Another problem with the prior art design is that the geometry of the contacts at the point of contact is not optimal and it is therefore desirable to replace the straight type of contacts with a shape that is better suited for making the contact with the contact point. 
     SUMMARY OF THE INVENTION 
     The connector of the current invention utilizes a unique one-piece design for each contact in the connector and consists of a coiled spring having loops at each end which are used as the actual contacts. The one-piece construction eliminates the additional contact interface surfaces between the coiled spring and the contacts and the looped ends provide more stability and a good geometry to connect with the contact point. This type of connector provides the advantage of eliminating the additional contact interface surfaces while at the same time being able to fit into a extremely small diameter hole. Another advantage of this design is the savings involved in the assembly of the connector. Because both contacts and the spring are of unitary construction, it is much less labor intensive to assemble this type of connector then it is to assemble the piston and spring type connector. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     FIG. 1 shows an assembled connector according to this invention. 
     FIG. 2 shows an exploded view of the connector of FIG.  1 . 
     FIG. 3 shows an inverted exploded view of the connector of FIG.  1 . 
     FIG. 4 shows the connector in place in its native environment. 
     FIG. 5 shows another view of the connector in place in its native environment. 
     FIG. 6 shows a single spring and the geometry thereof. 
     FIG. 7 shows the single spring of FIG. 6 in a cut away of the body of the connector. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 shows an assembled connector according to this invention. The connector consists of non-conductive body  10 , preferably made of molded plastic, cap  12 , also preferably made of molded plastic and a plurality of conductive elements  15  enclosed in body  10  and cap  12 . Cap  12  has a plurality of slots through which the looped ends  14  of conductive elements  15  extend. Likewise, body part  10  has, on the underside thereof, a corresponding plurality of slots  12  through which the opposite ends  14  of conductive elements  15  extend. This can be seen in FIG.  3 . 
     FIG. 2 shows an exploded view of the connector of FIG.  1 . The main body part  10  is constructed of molded plastic and contains a plurality of bores  20  defined therein for accepting the plurality of conductive elements  15 . Main body  10  also includes a plurality of recesses  24  for accepting clip members  22  defined on cap  12 . The plurality of conductive elements  15  are inserted into bores  20  such that the bottom loop  14  extends from slots  18  defined in the bottom of main body  10 . Cap  12  is then placed on top of main body  10  such that the upper loops  14  of conductive elements  15  extend through slots  18  defined in cap  12 . Note that while the connector of FIGS. 1-3 are shown as having  18  contacts, this invention is not limited thereby but can be used for connectors having any number of contacts. Cap  12  is then compressed onto main body  10  such that clip members  22  engage recesses  24 . Clip members  22  may be located either on cap  12  or on main body  10 , with the mating recesses being located on the opposite part. 
     FIG. 3 shows an inverted exploded view of the device of FIG. 1, showing the rectangular slots  18  defined in the bottom of main body part  10 . 
     One of conductive elements  15  is shown in FIG.  6 . Each conductive element  15  essentially consists of a spring portion  16  having defined on each end thereof a loop  14 . Although conductive elements  15  may be composed of any conductive material, in the preferred embodiment they are composed of stainless steel plated with nickel and hard gold. As the cap  12  is connected to main body part  10 , springs  16  are compressed thereby to provide a preload. Springs  16  are designed and constructed to provide an exact compression force when installed in the intended application. The compression must be sufficient to provide a contact resistance low enough to allow a current sufficient to support the necessary data signals being transmitted by the connector. The design of the springs (i.e., number of turns, material, gauge of wire, etc.) may be varied to provide varying amounts of compression, and therefore varying contact interface resistances when the connector is installed in the intended application. 
     FIG. 7 shows spring  15  in place in a cut away section of the molded plastic body of the connector. It can be seen that looped ends  14  extend through openings  18  in cap  12  and main body part  10 . The main portion of the cavity in which the spring portion  16  is received is preferably cylindrical in shape. This cylindrical cavity defined in body part  10  and cap  12  can be as small as 1 millimeter or less in diameter. This ability to use a hole of this size is an improvement over the prior art cantilevered design, which limited the size of hole that could be used. This feature of the invention provides a distinct advantage over the prior art, which would require a larger cylindrical cavity in which to receive the spring to provide the same compression as can be achieved in this design. 
     To assemble the connector, the plurality of springs are inserted in the cavities  20  with bottom loops  14  extending through rectangular slots  18  defined in the main body part  10 . Cap  12  is then placed on top of main body  10 , allowing upper loops  14  of conductive elements  15  to extend through the rectangular openings  18  and cap  12 . Clips  22  in cap  12  are received in recesses  24  defined in main body part  10  and engaged therein, thereby holding cap  12  securely in place and providing a preloaded compression on spring  16 . 
     FIGS. 4 and 5 show the connector in place in a typical application, for example, a cellular telephone consisting of frame  38  and main printed circuit board  34  having a plurality of contacts  36  defined thereon. Connector  8  is held in place by frame  38  and the lower looped ends  14  of connector  8  make contact with contacts  36  on printed circuit board  34 . FIG. 5 shows another view showing accessory  30  having a plurality of contacts  32  which contact the upper looped ends  14  of connector  8 , providing a positive connection between contacts  36  and contacts  32 . As springs  16  are compressed by pushing together accessory  30  and main unit  38 , the proper amount of electrical conductivity is achieved and contact resistance is minimized. 
     Although we have shown one embodiment of the connector, it can be seen by one of ordinary skill in the art that the frame consisting of main body part  10  and cap  12  can be made of any non-conductive material and conductors  15  can be comprised of any conductive material capable of providing sufficient construction of spring  16  to provide enough compression force to over come the necessary contact resistance. Additionally, the design parameters of spring  16  may be varied. Further, the connector need not be limited to application in mobile communications or data processing devices, but may be used for any application.

Technology Category: 5