Abstract:
A method and apparatus for discharging accumulated static charge in unshielded twisted pair cables. According to one example, an electrical jack includes a housing having an opening defined therein through which a mating plug is received, a grounding strip, and at least one elastically deformable signal contact residing within the housing. As the mating plug is received, the elastically deformable signal contact may move from a position in contact with the grounding strip to a position not in contact with the grounding strip, thereby discharging static charge from the unshielded twisted pair cables and allowing normal connection to the mating plug.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority under 35 U.S.C. §119(e) to commonly owned, copending U.S. provisional patent application Serial No. 60/275,045 entitled “Electrostatic Discharge Protected Jack”, filed Mar. 12, 2001 (not published), which is herein incorporated by reference in its entirety. 
    
    
     BACKGROUND 
     1. Field of the Invention 
     The present invention relates to cabling systems, and more particularly to connectors that may be used in systems including elements sensitive to static electric discharges. 
     2. Discussion of Related Art 
     Unshielded twisted pair (UTP) cables include several, for example, four, twisted pairs of conductors surrounded by a dielectric insulation. These cables are often used in high speed networks, for example, a local area network (LAN), to connect equipment, such as computers and/or telephones. 
     Unshielded twisted pair cables that are left unconnected or temporarily unused in a cabling system tend to act as capacitors and accumulate charge. The cables can often build up a very high charge, for example, up to 15 kV, which can cause serious damage to network equipment if the cable is connected before the accumulated charge is dissipated. 
     The cables can accumulate charge in a number of different ways. For example, if a cable is dragged along the floor, positive charges are created at the surface of the cable. The positive charges on the surface tend to attract negative charges on the twisted pairs, which causes charge separation leading to positive charges being present at the ends of the cable. If the cable is plugged into a directly or capacitively grounded connector, this build up of charge may cause arcing which could damage the cable or equipment to which the cable is connected. In another example, a cable that is placed in a strong electrostatic field and left there for some time will also accumulate charge on its surface. This charge tends to polarize the twisted pairs and cause some migration of the charge inside the dielectric insulation of the cable. After the cable is removed from the external electrostatic field, the charge remains, inducing a positive charge at the ends of the cable, as described above. Unconnected cables that are left in a dry environment can also accumulate charge from dust or other particles settling on the cable insulation. 
     When a cable has accumulated a large charge between its twisted pairs and the surroundings, this differential charge will cause charge carriers to migrate into the dielectric insulation. If the twisted pairs are grounded for a few seconds, the charge on the twisted pairs themselves, which can move quickly through the copper, will be neutralized. However, the charge carriers inside the dielectric insulation will not be removed. Thus, after removing the ground connection, the charges in the insulation will again cause a charge separation on the twisted pairs, leading to a potential difference between ground and the end of the twisted pairs. This potential difference may still damage network equipment when the cable is connected. For this an other reasons, providing shielded connector jacks in the cabling system will not effectively discharge the cables. Shielded jacks and electronic components on networking equipment are designed to dissipate charge build-ups according to the “Human body model,” i.e., the cable has accumulated an amount of static charge similar to that accumulated by a person, and having a similar characteristic. The static charge accumulated by unconnected UTP cables is often far greater than the “Human body model” and has a different discharge characteristic, and thus shielded jacks and electronic components on networking equipment are not an effective solution. 
     SUMMARY OF THE INVENTION 
     According to one embodiment, an electrical jack may include a housing having an opening defined therein through which a mating plug is received, a grounding strip and at least one elastically deformable signal contact residing within the housing. As the mating plug is received, the elastically deformable signal contact may move from a position in contact with the grounding strip to a position not in contact with the grounding strip, thereby grounding any electrostatic charges present in the mating plug. 
     According to another embodiment, an electrical connector panel comprises a housing and a plurality of connector jacks disposed in the housing. Each jack includes a plurality of spring contacts and the plurality of jacks is adapted to mate with a corresponding plurality of connector plugs. The connector panel further includes a grounding strip, coupled to a housing ground terminal, at least a portion of the grounding strip being disposed in a rear of the panel such that the plurality of spring contacts of each of the plurality of connector jacks are in contact with the grounding strip when in a first position, and wherein the plurality of spring contacts of one of the plurality of connector jacks move to a second position, not in contact with the grounding strip, when a connector plug is received by the connector jack. 
     According to one example, the grounding strip of either of the above embodiments may comprise metal or conductive plastic, or may include a dielectric with electrical circuitry disposed thereon. 
     Another embodiment includes a cabling system comprising at least one electrical cable terminated in a connector plug and a connector panel including at least one electrical jack adapted to receive and mate with the connector plug of the electrical cable, the electrical jack including a plurality of spring contacts movable between a first position and a second position. A grounding strip is disposed in the connector panel such that the plurality of spring contacts of the electrical jack are in contact with the grounding strip when in the first position, and the grounding strip is coupled to a chassis ground terminal. The cabling system further comprises network equipment coupled to the connector panel, and terminal equipment coupled to the connector panel by the at least one electrical cable. The plurality of spring contacts of the electrical jack are moved into the second position when the connector plug is received by the electrical jack, and the plurality of spring contacts are not in contact with the grounding strip when in the second position. 
     According to yet another embodiment, a method of discharging an unshielded twisted pair cable includes steps of securing a grounding strip in a housing of an electrical jack having a plurality of movable signal contacts and an opening adapted to receive a mating connector plug, such that the movable signal contacts are in contact with the grounding strip when in a first position, inserting the mating connector plug that terminates the unshielded twisted pair cable into the opening, and causing, by said inserting, the movable signal contacts to elastically deform to a second position not in contact with the grounding strip, thereby grounding any electrostatic charges present in the mating connector plug. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The foregoing, and other features and advantages of the device will be apparent from the following non-limiting description of various exemplary embodiments, and from the accompanying drawings, in which like reference characters refer to like elements throughout the different figures. It is to be appreciated that the drawings are for the purpose of illustration only and are not intended as a definition of the limits of the invention. In the drawings: 
     FIG. 1 is a schematic block diagram of an exemplary cabling network in which the connector jack of the present invention may be used; 
     FIG. 2 is a rear view of a connector housing, showing dividers which separate one signal contact from another; 
     FIG. 3 is a plan view of an exemplary embodiment of a grounding strip suitable for use in the connector housing of FIG. 2; 
     FIG. 4 is a rear view of the connector housing of the FIG. 2 with the grounding strip of FIG. 3 installed. 
     FIG. 5 is a side view of the spring contacts which reside in the connector housing of FIG. 1, when assembled. 
     FIG. 6 is a plan view of another exemplary grounding strip that may be used in the connector housing of FIG.  2 . 
     FIG. 7 is a perspective view of an exemplary embodiment of a connector panel according to aspects of the invention; 
     FIG. 8 is cross-sectional side view of the connector panel of FIG. 7 taken along lines  8 — 8  of FIG. 7; 
     FIG. 9 a  is a cross-section of the connector panel of FIG. 7 with a connector plug partially inserted within the connector jack; 
     FIG. 9 b  is a cross-section of the connector panel of FIG. 7 with a connector plug fully inserted within the connector jack; 
     FIG. 10 is a plan view of an exemplary embodiment of a grounding strip that may be used with the connector panel of FIG. 7; 
     FIG. 11 is a plan view of another exemplary embodiment of a grounding strip that may be used with the connector panel of FIG. 7; 
     FIG. 12 is an exploded cross-sectional plan view of a connector jack and plug taken along lines  12 — 12  of FIG. 8; 
     FIG. 13 is cross-sectional rear view of the connector panel of FIG. 7 taken along lines  13 — 13  of FIG. 8; 
     FIG. 14 is an enlarged fragmentary cross-sectional view of the connector panel taken along lines  14 — 14  of FIG. 13; and 
     FIG. 15 is a perspective view of a partially formed grounding strip of FIG.  10 . 
    
    
     DETAILED DESCRIPTION 
     Referring to FIG. 1, there is illustrated an exemplary cabling system  100  including a plurality of unshielded twisted pair (UTP) cables  102 ,  104  and network equipment, such as hub equipment  106  and terminal devices, for example a computer  108  or telephone  110 . The exemplary cabling system  100  includes outlets  112  to which the terminal devices are connected by means of patch cables  114 . The UTP cables  102 ,  104  connect the outlets  112  to a connector panel  116 , which, is in turn connected to the hub equipment  106  via patch cables  118 . Of course, it is to be appreciated that other configurations of cabling system may equally embody the present invention. 
     In the illustrated example, UTP cables  104  are connected to an unused outlet  112  (i.e., no terminal devices are attached to the outlet) and may thus accumulate charge as described above. In order to prevent the accumulated charge from discharging into any terminal devices that may later be connected to cables  104  through the outlet  112 , thereby damaging the terminal devices, the outlet  112  and/or connector panel  116  may be equipped with means for discharging the cable  104 . This means may include means for continuously discharging the cable, thereby preventing an accumulative buildup of charge, or means for discharging any previously built up charge at the later time when a terminal device, or other network equipment, is attached, without damaging the network equipment. It should be noted that the illustrated embodiment of aspects of the invention will also be effective to protect against charges built up in a previously unused patch cable  114 ,  118  that is later placed into service. The means and its operation is described in more detail below. 
     FIG. 2 illustrates an exemplary housing  200  of an RJ-45 style connector jack embodying aspects of the invention. It is to be appreciated that although the following description will refer to RJ-45 style connector jacks, the invention is not so limited, and may be adapted to be used in other types of connector jacks having elastically deformable signal contacts, or otherwise movable signal contacts. Referring to FIG. 2, it can be seen that the housing  200  includes a slotted separator  202  which may accommodate eight signal contacts. It is to be appreciated that although the illustrated example accommodates eight signal contacts, the invention is not so limited, and the housing may be adapted to accommodate any number of signal contacts as necessary. 
     Referring to FIG. 3, there is illustrated, in plan view, an exemplary embodiment of a grounding strip  300  that may be used in combination with the housing of FIG.  2 . The housing  200  may receive the grounding strip of FIG.  3  through holes in the sides of the housing  200 , through which the grounding strip  300  is positioned as shown in FIG.  4 . The grounding strip  300  may be provided with features, such as end portions  302  and indentation  304 , adapted to maintain the grounding strip  300  within the housing  200 . The grounding strip  300  may further be provided with a hole  306  through which a pin (not shown) of the housing  200  fits to secure the grounding strip  300  within the housing  200 . As shown in FIG. 3, the grounding strip  300  may be also provided with contact portions  308  that fit between the slotted separator  202  of the housing  200  when the grounding strip  300  is inserted into the housing  200 . 
     Referring to FIG. 5, there is illustrated, in side view, an exemplary contact assembly portion  500  of a connector jack. The contact assembly  500  may be inserted into the back of the housing  200  of FIG. 4, such that the signal contacts  504  contact the contact portions  308  of the grounding strip  300 . When a plug, for example, terminating a UTP cable, is inserted into the assembled connector, the plug signal contacts first make contact with the grounded jack signal contacts. Then, the plug signal contacts begin to elastically deform and flex the jack signal contacts away from the grounding strip. This will be described in more detail below in reference to FIGS. 8-10. Thus, any static charge carried by the cable attached to the plug signal contacts is discharged into the grounding strip before the jack signal contacts are disconnected therefrom. This serves to protect any electrical equipment connected to the jack. According to one example, if a patch cable  114  (see FIG. 1) has been left unconnected for some time and has accumulated static charge, when the patch cable  114  is connected into an outlet  112  that includes the connector jack embodying to aspects of the invention, the static charge accumulated within patch cable  114  will discharge into the grounding strip as the patch cable is connected, thereby preventing any damage from occurring to the terminal device. It is to be appreciated that the above-described connector jack may be used in many applications as a stand-alone unit or in combination with other connector jacks, for example, in the connector panel  116  or outlet  112  of FIG.  1 . 
     According to one example, the grounding strip (FIG. 3,  300 ) may be constructed of metal, or of a conductive plastic. In another example, the grounding strip (FIG. 6,  600 ) may include a dielectric material with electrical circuitry disposed thereon to provide a grounding connection  602  for the contacts of the connector jack, as shown in FIG.  6 . It is to be appreciated that the electrical circuitry may include many variations, provided it performs the basic function of grounding the contacts of the connector jack. Furthermore, the grounding strip may be connected to a ground terminal, which may be a grounded portion of the connector housing, or a grounded portion of the outlet  112  (see FIG. 1) or connector panel  116  in which the connector jack is disposed. It is to be noted that this ground terminal may be a “chassis ground”, which may not be equivalent to a “signal ground” of signals propagating in the cables and signal contacts  504  of the connector jack. In addition, the grounding strip  300  may not be directly connected to the ground terminal. For example, one or more resistors  604  may be connected in series between the grounding strip  300  and the ground terminal to provide a load through which an attached cable is grounded. The grounding strip  600  may further include contact portions  608  that contact the signal contacts of the connector jack. According to yet another example, the signal contacts may be provided with discharge protectors  606 , for example, zener diodes, connected between the signal contacts  504  and the ground terminal  602  to provide additional protection against static discharges. These discharge protectors  606  may be included in the electrical circuitry disposed on the grounding strip  600 , as shown, but may also be provided within the housing of the connector jack as separate elements from the grounding strip. 
     Referring to FIG. 7, there is illustrated an exemplary embodiment of a connector panel  116  that may be used in the cabling system  100  of FIG.  1 . As illustrated, the connector panel  116  may include a plurality of connector jacks  700  mounted in a housing  702 . It is to be appreciated that although the illustrated embodiment includes four connector jacks  700 , the connector panel is not so limited, and may include any number of connector jacks as necessary. The connector jacks  600  of the connector panel  116  may be RJ-45 style connector jacks, as described above, or another type of connector jack having elastically deformable, or otherwise movable, signal contacts. As shown, the connector jacks  700  are adapted to receive and mate with a corresponding connector plug  704  attached to UTP cable  706 . In one example, as shown in FIG. 1, the housing portion  702  may be mounted to an equipment rack or chassis  120  that may house a plurality of network equipment, such as hub equipment  106 . Placement of the connector panel  116  in the equipment rack  120  may be advantageous as it may be convenient for connecting the network equipment to the connector panel  116  via patch cables  118 . 
     Referring to FIG. 8, an exemplary connector jack  700  is shown in cross-section, with a corresponding connector plug  704  shown not yet mated with the connector jack  700 . The connector jack  700  includes spring signal contacts  708  that are in contact with contact portions  710  of a grounding strip. Thus, before the connector plug  704  is mated with the connector jack  700 , the signal contacts  708  of the connector jack  700  are continuously grounded, thereby preventing any build-up of static charge in a cable connected to the connector jack, for example cable  104  (see FIG.  1 ). The grounding strip may include tabs  712  that hold the contact portions  710  in place within the housing of the connector jack  700 . 
     Referring to FIGS. 9 a  and  9   b , it can be seen that when the connector plug  704  is partially inserted within the connector jack  700 , as shown in FIG. 9 a , the spring signal contacts  708  of the connector jack are still in contact with the contact portions  710  of the grounding strip  720 . Thus, the portion  716  of the plug signal contacts  714  initially make contact with the grounded jack signal contacts  708 . When the connector plug  704  is fully mated with the connector jack  700 , as shown in FIG. 9 b , the plug signal contacts  714  cause the jack signal contacts  708  to elastically deform and flex away from the grounding strip contact portions  710 , as described previously. Thus, when the plug is fully mated with the connector jack  612 , the jack signal contacts are no longer grounded. As shown in FIG. 1, the grounding strip  720  may be connected to a ground terminal, such as the equipment rack  120 . This connection may be made via a grounding patch cable  122 , as illustrated, or by another suitable means, for example, a screw or rivet (not shown) fastening the connector panel  116  to the equipment rack  120 . It is to be appreciated that this “chassis ground” is not necessarily equal in voltage to a signal ground of the signals propagating in the various UTP cables and in the network equipment. 
     FIG. 10 illustrates, in plan view, an exemplary embodiment of a grounding strip  720  that may be used with the connector panel  116 . It is to be appreciated that the invention is not limited to the example illustrated in FIG. 10, and the grounding strip  720  may have any structure suitable for use with a selected connector. For example, the grounding strip  300  of FIG. 3 or the grounding strip  600  of FIG. 6 may be modified to be used with the connector panel  116 . Referring to FIG. 10, the grounding strip  720  includes a base portion  722 , and a plurality of body portions  724  extending away from the base portion  722 . The number of body portions  724  may correspond to the number of connector jacks  700  in connector panel  116 . FIG. 10 also illustrates the contact portions  710  that contact the spring signal contacts of the connector jack  700 , and the tabs  712  that may be used to secure the body portion  724  and contact portions  710  within the connector housing (see FIGS. 8,  9   a  and  9   b ). 
     It is to be appreciated that, similar to grounding strip  300 , the grounding strip  720  may be metal or may be a conductive plastic, or may be formed of any other suitable material. In one example, shown in FIG. 11, another example of a grounding strip  730  may include a dielectric with electrical circuitry  732  disposed thereon to provide a grounding connection  734  for the signal contacts portions  736 . Furthermore, as described above, the circuitry may include series resistance or inductance  738  to provide a load between the signal contacts of the connector jack and the ground terminal  734 , through which the static charge may be dissipated. In another example, the spring contacts of the connector jacks  700  may be provided with discharge protectors, such as zener diodes, to further protect against static discharge. These discharge protectors may be provided as elements within the connector housing (not shown) or may be included as part of the electrical circuitry on the grounding strip  730 , as was illustrated for grounding strip  600  in FIG.  6 . 
     FIG. 12 illustrates a cross-sectional view taken along lines  12 — 12  of FIG. 8 of the connector jack and plug of FIG. 8 with the grounding strip  720  installed. It can be seen that the base portion  722  of the grounding strip  700  fits along the rear of the connector panel  116  while the body portions  724  of the grounding strip  720  are folded over a section of the connector housing such that contact portions  710  of the grounding strip fit inside a comb portion of the connector housing, in contact with the spring signal contacts of the connector jack  700 . 
     Referring to FIG. 13, there is illustrated a cross-sectional rear view of a portion of the connector panel  116 , showing two connector jacks  740  and  742 . Connector jack  740  does not have a connector plug mated with it, for example, corresponding to connector jack  740  of FIG. 7, and the spring signal contacts  708  are thus in contact with the contact portions  710  of the grounding strip  720 . Connector jack  742 , for example, corresponding to connector jack  742  of FIG. 7, has a connector plug  704  mated with it. As illustrated in FIG. 9 b , the spring signal contacts  708  of the connector jack  742  have been moved into a position no longer in contact with the grounding portions  710  of the grounding strip  720 . 
     Referring to FIG. 14, it can also been seen that the tabs  712  of the grounding strip  720  are deformed against the sides of the connector housing  744 , when the grounding strip is installed within the connector housing (as shown in FIG.  13 ), thereby retaining the body portions  724  and contact portions  710  of the grounding strip  700  in position within the housing  744  of the connector jacks  700 . FIG. 15 illustrates the grounding strip  720  folded and arranged as it appears within the connector panel  116 . 
     As described previously, the grounding strip  720  may have a selected number of body portions  722  corresponding to the number of connector jacks  700  installed within the connector panel  116 . However, in another embodiment, the grounding strip  720  may be manufactured with a predetermined number of body portions  722 , and two or more grounding strips  720  may be daisy-chained together to accommodate connector panels  116  having more connector jacks  700  that the predetermined number of body portions  722  of a single grounding strip  720 . In one example, the daisy-chaining may be accomplished by overlapping part of the base portions  722  of two grounding strips  720  and securing them together, for example, by way of a screw or conductive adhesive, or by pressing them together inside a part of the connector or panel housing. In another example, the base portions  722  may be provided with features, for example, a slot and tab, to allow two or more grounding strips to be daisy-chained together. It is to be appreciated that this feature of daisy-chaining two or more grounding strips together may also be applied to the grounding strips  730 ,  600  and  300  of FIGS. 11,  6  and  3  respectively. 
     Having thus described various illustrative, non-limiting embodiments and aspects thereof, modifications and alterations will be apparent to those of skill in the art. Such modifications and alterations are intended to be included in this disclosure, which is for the purpose of illustration and explanation and not intended to define the limits of the invention. The scope of the invention should be determined from proper construction of the appended claims, and their equivalents.