Abstract:
An electrical connector assembly having an electrostatic discharge device, a shield for an electrical connector assembly with an electrical discharge device. A device for discharging electrostatic charges includes a resilient, electrically conductive material to ensure a discharge of electrostatic charges on a permanent basis and with reduced space requirements.

Description:
FIELD OF THE INVENTION  
         [0001]    The invention relates in general to shielded electrical connectors and especially to an electrical connector assembly having an electrostatic discharge device protecting against electrostatic discharges, to a shield for an electrical connector assembly with an electrical discharge device and also relates to an electrical discharge device.  
         BACKGROUND OF THE INVENTION  
         [0002]    Electrical connector assemblies provide access to electrical and electronic circuits connected downstream to a power or signal path. However, in case of connecting two or more electronic devices, for example in electronic in-house networks or Intranets, firstly considerable electrical potential differences or voltages may occur between the individual devices and, secondly, in case of electrical potential-free connections, electrostatic charges can be applied and when the associated electrical connectors are joined together, undesired discharge of the charges producing the potential difference, or discharging of the electrostatic charge, may occur. These discharging processes are apt to cause severe damage in electronic equipment arranged downstream the signal or power path, it being possible for the damage even to lead to complete failure of the respective equipment.  
           [0003]    U.S. Pat. No. 5,947,773 describes an electrical connector with an electrostatic discharge protection (ESD protection), in which, in addition to the terminals of the connector, pairs of discharge contacts arranged in front of the said terminals are connected with a defined resistance to the ground potential of the electrical equipment. A disadvantage of this assembly is that, as a result of the additional pairs of terminals, further capacitances and resistances are coupled to the signal path. This, under certain circumstances causes a considerable detrimental influence on the high-frequency transmission characteristics of the electrical connector. In addition, introducing further pairs of electrical terminals leads to a significant enlargement of the dielectric housing of the connector, which is in contradiction to the continuous efforts for a further miniaturization.  
         SUMMARY OF THE INVENTION  
         [0004]    Consequently, it is an object of the invention to ameliorate the above-described disadvantages and, in particular, to provide an electrical connector assembly and a device for shielding an electrical connector assembly in which a discharge of electrostatic charges is permanently reliable and is possible with a small space requirement. This object is obtained in a surprisingly simple manner by an electrical connector assembly comprising a dielectric housing, terminals which are held in the dielectric housing and comprise connecting portions to provide electrical contact to terminals of an associated electrical connector, the terminals also comprising connecting ends for establishing an electrical connection to electrical feed lines, a device for discharging electrostatic charges, with the device for discharging electrostatic charges comprising a resilient, electrically conductive material.  
           [0005]    The inventors found out that, by means of a resilient conductive material, the terminals of an associated electrical connector can reliably discharged, especially electrostatic charge can be removed before these terminals come into contact with the terminal portions of the other connector.  
           [0006]    It has proven to be advantageous to arrange the device for discharging electrostatic charges close to an insertion opening of the dielectric housing, in insertion direction in front of the connecting portions of the electrical connector. When RJ 45 connectors are used, a comb-like portion of the resilient material provides great advantages since a considerably enlarged surface area of the terminals of the associated connector to be inserted can be gripped by its teeth and, moreover, in addition to the electrostatic discharge, a considerable cleaning action is provided.  
           [0007]    If the comb-like portions of the electrostatic discharge device project laterally into an insertion cavity formed in the dielectric housing of the electrical connector for an associated mating electrical connector, then the associated electrical connector undergoes a forced discharge as it is inserted, and it is possible for the resilient, electrically conductive material both to be forced back by means of volume compression and to be bent back resiliently. Such a design of the electrostatic discharge device means that the latter can be used without significant enlargement of the dimensions of the housing, for example in a socket-type RJ  45  connector, in which a front recessed housing accommodates the resilient conductive material.  
           [0008]    By using a ramp-like area formed behind the comb-like portion of the dielectric housing and extending obliquely with respect to the insertion direction, the conductive material can be prevented from shearing off, since by this means the comb-like portion is enabled to be bend back, even essentially without any volume compression. In a further advantageous refinement, the electrostatic discharge device comprises fastening means which are adapted to interact with fastening means of the dielectric housing and can hold the electrostatic discharge device in its position.  
           [0009]    If the fastening means comprise recesses and protrusions, and if the recesses are formed by the resilient material and are somewhat smaller than the protrusions, this means that holding forces can already be provided which are suitable for holding the electrostatic discharge device permanently on the dielectric housing.  
           [0010]    With a shield which surrounds at least a front area of the dielectric housing and is in electrical contact with the electrostatic discharge device, the latter can be kept in a simple way at the electrical potential of the housing of the respective electrical or electronic device. A particularly preferred embodiment comprises a multiple connector assembly which comprises a large number of cavities for associated electrical connectors, and in which the connecting portions of the terminals for the associated electrical connectors are arranged in each case in two cavities adjoining in pairs on that inner side of the cavity which is closest to the respectively paired adjacent cavity.  
           [0011]    This makes it possible, in particular, to arrange the device for discharging electrostatic charges between two paired adjacent cavities in each case and to use a single device for both cavities.  
           [0012]    A preferred embodiment of the device for discharging electrostatic charges comprises a resilient, electrically conductive material with an essentially T-shaped cross section, in which the comb-like portions each point away from one another and in which the central portion rests at the end on the shield in such a way that this produces a mechanical bias or prestress which then contributes to holding the resilient conductive material in its position.  
           [0013]    In a further preferred embodiment, the shield for the electrical connector assembly comprises a metal sheet, in which insertion openings for associated cavities of the dielectric housing of the electrical connector are defined, and on which a resilient conductive material is arranged.  
           [0014]    In a particularly preferred further refinement, comb-like portions of the electrostatic discharge device extend somewhat into the insertion openings in such a way that this results in a forced discharge occurring during the insertion operation. In addition, given a defined lateral projection of the resilient material on all sides, a sealing and vibration-inhibiting action can be implemented, which protects circuits in a rough environment, such as PCMCIA board adapters or connectors arranged in lap-top housings, when the associated male connector is inserted.  
           [0015]    If the shield is produced as a retrofitting set for electrical connector assemblies, the electrically conductive resilient material of a preferred embodiment advantageously consists of a stamped sheet, which is already fastened to the metal sheet with a conductive adhesive. This provides a unit which can be treated and handled on its own and which, together with the shield, has an electrostatic protective function.  
           [0016]    The invention is described in more detail below with reference to the appended drawings and on the basis of preferred embodiments.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]    [0017]FIG. 1 shows a front view of the housing of a multiple connector assembly according to an embodiment of the invention,  
         [0018]    [0018]FIG. 2 shows a perspective sectional illustration, obliquely from the front, along the section plane A-A shown in FIG. 1,  
         [0019]    [0019]FIG. 3 shows a side view of the perspective sectional illustration from FIG. 2 in the direction of arrow B shown in FIG. 2,  
         [0020]    [0020]FIG. 4 shows an enlarged detail of the side view from FIG. 2,  
         [0021]    [0021]FIG. 5 shows a perspective sectional illustration of a detail from FIG. 3, which shows part of the shield and the electrostatic discharge device,  
         [0022]    [0022]FIG. 6 shows an enlarged detail of a side view corresponding to FIG. 2 in a further embodiment according to the invention,  
         [0023]    [0023]FIG. 7 shows an enlarged detail of a side view of a cross section similar to FIG. 6 in yet another embodiment according to the invention in the form of a single connector assembly without fitted shield, and  
         [0024]    [0024]FIG. 8 shows the embodiment of the single connector assembly illustrated in FIG. 7 with fitted shield.  
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0025]    The invention is described in more detail below and in view of preferred embodiments. In order to support a better understanding, in the description of the respective embodiments, identical reference symbols are used for identical or similar parts or subassemblies.  
         [0026]    Reference is made first to FIG. 1, which shows a front view of an electrical multiple connector assembly  1 , which comprises twelve socket-like RJ 45 connectors  3  to  14  in one dielectric housing  2  and depicts a first preferred embodiment of the invention.  
         [0027]    Although the invention will be described below in view of an embodiment using multiple connectors and in particular using socket-like RJ 45 connectors, it is not restricted to this special type of connector.  
         [0028]    RJ 45 multiple connector assemblies of this type, without a device according to the invention for discharging electrostatic charges, are described in more detail, for example in the German Utility Model DE 298 19 341.0 from the same applicant, and the disclosure of this German Utility Model DE 298 19 341.0 in its entirety is also incorporated by reference into the description of the present disclosure of the invention.  
         [0029]    Formed in the dielectric housing  2 , for each socket-like RJ 45 connector in each case, is a cavity  15  to  18  to accommodate an RJ 45 connector, which will be described in more detail below with reference to FIG. 2 and cavity  17 .  
         [0030]    Into each of the cavities extend eight terminals in each case, of which in FIG. 2, because of the cross sectional plane chosen, only six terminals  19  to  24  can be seen, each being held in the dielectric housing  2 .  
         [0031]    In addition, FIG. 3 reveals, using the example of terminal  24 , that the terminal  24  forms a connecting portion  24   a  to provide an electrical contact with the terminals of an associated mating electrical connector well known to a person skilled in the art and, therefore, not shown in the drawings. In this case, the connecting portions for the associated electrical connector of two adjacent cavities  13 ,  17  are each arranged in front of that inner side of cavity  13  which is closest to adjacent cavity  17 .  
         [0032]    When an associated mating RJ 45 connector is inserted, the connecting portion  24   a  will come into contact with the terminals of the associated RJ 45 connector and in this way produce an electrical connection.  
         [0033]    Terminal  24  further comprises a connecting end  24   b  for an electrical connection to electrical feed lines, for example an electric printed circuit board or solder tabs for the connection of flexible flat conductor tracks or similar circuitry.  
         [0034]    Dielectric housing  2  is surrounded by a shield  25  which, in the form of a metal sheet  39 , extends essentially parallel and closely adjacent to the outer surface of the front side  26 , the rear side  27 , the top side  28  and side walls  29  and  30  (see FIGS. 1 and 3).  
         [0035]    In opposite insertion direction, i.e. in a direction opposite to arrows X illustrated in FIGS. 2 and 3, a device for discharging electrostatic charges  31  is in each case arranged in front of the terminals  19  to  24 , and comprises a resilient, electrically conductive material. The resilient, electrically conductive materials used according to the invention may be, in particular, all elastomers, thermoplastics or further resilient materials or any combinations thereof which exhibit a specific electrical conductivity which is suitable for carrying at least low current intensities. It is generally possible to use conductivities in the range from a few Ohm/cm to several MOhm/cm.  
         [0036]    Conductivity sufficient for the resilient material according to the present invention also can be provided by means of incorporated conductive grains, by means of doping or by means of an intrinsic conductivity of the resilient material itself. In the case of foam, cellular or sponge-like material, conductivity also can be provided by means of a surface coating with a conductive substance.  
         [0037]    As FIG. 2 shows in more detail, the device  31  for discharging electrostatic charges has, for each of the cavities  13 ,  17 , a comb-like portion  32 ,  33  which, in each Patent AO- 073  US case behind the insertion opening, projects into cavity  13 ,  17  formed by the dielectric housing and is in each case arranged between two paired adjacent cavities  13 ,  17 .  
         [0038]    Device  31  for discharging electrostatic charges has, in the first preferred embodiment, an essentially T-shaped cross section in which comb-like portions  32 ,  33  each point away from one another and in which the central section rests, at the end, on the shield  25  and thus produces an electrical contact with the potential of the shield  25  (see also FIG. 5).  
         [0039]    The teeth of the comb-like portion  32 ,  33  have a width which essentially corresponds to the spacing or pitch of the connecting portions of the terminals  19  to  14  in the dielectric housing  2 , and therefore corresponds to the spacing of the terminals of the associated electrical connector, so that when the associated electrical connector is inserted, a large-area contact is produced between the resilient material and the terminals of the associated mating connector.  
         [0040]    Behind comb-like portion  32 ,  33 , a ramp-like area extending obliquely with respect to the insertion direction X is defined by the dielectric housing and, when the associated electrical connector is inserted, permits resilient bending of the comb-like areas  32 ,  33  in the insertion direction X, without it being possible for any parts of the resilient, electrically conductive material to be sheared off.  
         [0041]    The enlarged illustration of FIG. 4 reveals that the electrostatic discharge device  31  comprises fastening means  36  which interact with fastening means  37  of the dielectric housing  2  and hold the electrostatic discharge device  31  on dielectric housing  2 .  
         [0042]    Without restricting generality, fastening means  36  comprise recesses which are formed in the resilient material and protrusions  37  which extend forwards from the dielectric housing  2 , i.e. in a direction opposite to that of arrows X from FIGS. 2 and 3. Since recesses  36  are formed by the resilient material and are smaller than protrusions  37 , the protrusions held in the recesses can provide suitable holding forces, depending on the dimensions, on the size ratio and suitable choice of the resilient material. In addition, the scope of the invention includes fastening the resilient, electrically conductive material to the dielectric housing  2  with an adhesive.  
         [0043]    Now, reference is made to FIG. 6, where a further embodiment according to the invention is illustrated, in which the electrostatic discharge device comprises a resilient, electrically conductive sheet  38  the two-dimensional extension of which, apart from the respective comb-like portions  32 ,  33 , correspond to the area of the front side  26  of the dielectric housing  2  or the front side of the shield  25 . In order to produce this geometry, sheet  38  can expediently be obtained, for example, by stamping it out from a carrier sheet.  
         [0044]    Sheet  38  can also be fastened to shield  25  by means of a conductive adhesive, so that in this way a shield subassembly which can be handled on its own, with an electrostatic discharge device, is provided.  
         [0045]    A further embodiment according to the invention is illustrated in FIGS. 7 and 8, to which reference is made below.  
         [0046]    [0046]FIG. 7 shows an enlarged detail of a side view of a cross section similar to the side view of FIG. 6, but in yet another embodiment according to the invention. This further embodiment comprises a socket-like RJ 45 connector having only a single cavity  45  to accommodate an associated RJ  45  plug-in or male connector. In FIG. 7, the connector assembly is illustrated without a shield, in order to be able to illustrate better the specific shape of the device  31  for discharging electrostatic charges.  
         [0047]    In this embodiment, the device  31  for discharging electrostatic charges is arranged in a passage opening  40  which leads to the interior of cavity  45 . This passage opening  40  defines an essentially rectangular cup-like area  41 , at the bottom of which a passage  46  to the interior of the cavity  45  is formed.  
         [0048]    The resilient material of the electrostatic discharge device  31  defines a widened area  42  the width of which essentially corresponds to the clear width of rectangular area  41  or is slightly greater than this. In the last-mentioned case, there is a deliberate press fit of the widened area  42  in the rectangular part  41  of the passage opening  40 , which holds the device  31  securely in its defined installation position, for example during assembly.  
         [0049]    Comb-like portion  32  of the electrostatic discharge device  31  extends from the widened area  42 , through the passage  46 , into the interior of cavity  45  and in this way reaches the terminals of an associated connector before these terminals get into the desired electrical contact with terminals  19  to  24 .  
         [0050]    Comb-like portion  32  has a recess  44  which reduces its tilting resistance locally and therefore ensures that defined tipping of the comb-like portion in the insertion direction, in the direction of arrow X into the ramp-like area  34  takes place when an associated RJ  45  plug-in or male connector is inserted into cavity  45 .  
         [0051]    Above the widened area  42 , on the electrostatic discharge device  31 , there is arranged an extension  43  which, in the undeformed state, projects beyond the passage opening  40 , as illustrated in FIG. 7.  
         [0052]    In the following text, reference will be made to FIG. 8, which shows the embodiment of the single connector assembly illustrated in FIG. 7 with the shield  25  fitted or in its finally assembled position.  
         [0053]    When shield  25  is fitted or mounted, it comes into mechanical contact with the extension  43  and therefore, because of the conductivity of the resilient material of device  31 , also comes into electrical contact with the said extension. The bending of the extension  43 , together with its resilient restoring forces, leads to a vibration-proof and reliable permanent electrical connection between the shield  25 , which is preferably at ground potential, and the comb-like portion  32 .