Patent Publication Number: US-2011053418-A1

Title: Modular jack with two-piece housing and insert

Description:
BACKGROUND 
     1. Field of the Invention 
     The present invention relates generally to modular telecommunications jacks and, more particularly, to a modular jack having a two-piece housing and a shock absorbing insert. 
     2. Description of Related Art 
     Modular jack (“modjack”) receptacle connectors mounted to printed circuit boards (PC boards) are well known in the telecommunications industry. These connectors are typically used for electrical connection between two electrical communication devices. With ever-increasing operating frequencies of data and communication systems and an increased density of information to be transmitted, the electrical characteristics of such connectors are of increasing importance. In particular, it has to be ensured that these modjack type connectors do not have deleterious effects on the signals to be transmitted and that no additional interference is introduced. Based on these requirements, various proposals have been made in order to minimize negative influences, especially of modjack connectors, used with communication or transmission links. 
     When used as Ethernet connectors, modular jacks generally receive an input signal from one electrical device and then communicate a cleaned up corresponding output signal to a second device coupled thereto. Magnetic circuitry is used in the transfer of the input signal of one device to the output signal of the second device and also cleans the input signal during transfer from the first device to the second. Currently, modjacks are made using a single channel ferrite choke. Usually these chokes are toroidal magnetic ferrite common mode chokes for use in various filtered connectors. The chokes are used to reduce the amount of unwanted common mode signal in differential signaling applications. 
     For the elimination of in-phase interference signal noise components, U.S. Pat. No. 5,015,204 teaches use of a common-mode choke arranged in a connector housing around which the contact leads of a RJ-45 modjack connector are integrally wound. In this design, the common-mode choke takes up a substantial portion of the connector housing, although only two signal-conducting leads are used. Furthermore, the respective leads need a certain rigidity to provide resilient forces to continuously facilitate a secure contact with the associated modular plug connector. Unfortunately, this makes for difficult manufacturing conditions, especially when the rigid wires have to be wound around the conductive core of the choke coil and the entire assembly placed within the modjack housing. 
     More particularly, difficulty in manufacturing arises from the fact that currently available modjacks are manufactured such that they are formed using a single frame configuration. That is, the modjack includes a hollow box-shaped housing that is formed as a single piece component. Magnets, choke coils and other filtering components are then placed within the frame through the relatively narrow opening. These components are then potted using silica gel, which once again must be applied through the relatively small opening in the modjack housing. 
     Therefore, it can be seen that inserting and potting of the components is difficult because of the relative inaccessibility of the interior of the single piece modjack housing. Furthermore, the performance of the choke in known modjack designs is significantly reduced if an unbalanced DC current is applied to the circuit. This may occur in Power over Ethernet type of applications because of the saturation of the ferrite core. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       Various other objects, features and attendant advantages of the present invention will become more fully appreciated as the same becomes better understood when considered in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the several views in which: 
         FIG. 1  is a front isometric view of a modjack in accordance with an embodiment of the invention; 
         FIG. 2  is a partially exploded view of the modjack of  FIG. 1  with the outer shielding removed; 
         FIG. 3  is a rear isometric view of the modjack of  FIG. 2 ; 
         FIG. 4  is partially exploded view of the modjack of  FIG. 3  with the internal modules removed; 
         FIG. 5  is an isometric view of a single internal module; 
         FIG. 6  is an exploded view of the internal module of  FIG. 5 ; 
         FIG. 7  is an exploded view of a component housing of the internal module of  FIG. 6  showing noise reduction components; 
         FIG. 8  is a wiring diagram for a transformer wire winding assembly; 
         FIG. 9  is a wiring diagram for a transformer and choke wire winding subassembly; 
         FIG. 10  is a wiring diagram for a PoE choke wire winding subassembly; 
         FIG. 11  is a partially assembled isometric view of the housing of the internal module with the noise reduction components inserted into the housing; 
         FIG. 12  is a partially assembled isometric view of the housing of the internal module with a shock absorbing insert placed into the housing; and 
         FIG. 13  is a cross section of a fully assembled component housing of  FIG. 6 . 
     
    
    
     DETAILED DESCRIPTION 
     In order to provide a modular jack with magnetic filtering (magjack) that avoids the problems of the prior art and also which is able to increase performance and ease of manufacturing, there is provided a modular jack system where the jack includes two component housing halves that are configured to mate with one another other. The filtering components or magnetics, which may include a multichannel choke, are placed inside either one or both halves of the housing and potted prior to assembly. A shock-absorbing insert is also placed between the two halves to protect any filtering components or assemblies located within the component housing. The halves of the housing are then brought together to form the assembled component enclosure or housing. 
       FIG. 1  illustrates the front side of an exemplary embodiment of the present invention in its fully assembled form. As shown, the magjack  100  is a multiple input, stacked jack for receiving multiple Ethernet or RJ-45 type of plugs (not shown). The magjack  100  includes a magjack housing  102  made of an insulating material such as 30% glass filled PBT or other similar material and includes front side openings  103  that are configured to receive Ethernet or RJ-45 type jacks (not shown). The magjack  100  is mounted on circuit board  104 . Metal or other conductive shielding  106  is used to surround the magjack housing  102  for RF and EMI shielding purposes as well as for providing a ground. It should be noted that similar configurations are possible in situations where only a single unit magjack is desired. 
     The shielding  106 , as shown in  FIG. 2 , is configured such that it may be installed on the magjack  100  subsequent to the magjack  100  being assembled and mounted on the circuit board  104 . The shielding  106  includes a front shield  106   a  and a back shield  106   b . These joinable shields are formed with interlocking tabs  108 ,  110  for engaging and securing each other when the shielding  106  assembly is placed into position around the magjack  100  and onto the circuit board  104 . Each of the shields  106   a ,  106   b  includes guide posts  112 ,  114  that are placed into through-holes  116  on the circuit board  104 . As shown in  FIG. 3 , the back portion of the exemplary magjack housing  102  includes relatively large openings  115  that are sized and shaped to receive internal subassembly modules  118  ( FIG. 4 ). These modules  118  provide the physical contacts for engaging Ethernet plugs and also provide the electrical functionality of the jacks, such as Power Over Ethernet (POE). A particular advantage of the present modular system is that the entire magjack  100  does not need to be populated with the same internal subassembly modules or more than a single external module at all. This helps keep manufacturing costs low and enables the manufacturer to customize the magjack as need by the customer. 
       FIG. 5  shows a detailed view of the exterior of the subassembly module  118 . The module  118  includes a contact module  120  that is electrically connected to a top printed circuit board (PCB)  122 . The top PCB  122  is mounted to a component housing  126 , which includes magnetic circuits and filtering components. The component housing  126  is then mounted on a bottom PCB  124 . 
     As shown more clearly in  FIG. 6 , the contact module  120  includes a top contact assembly  121   a  and a bottom contact assembly  121   b  for providing stacked jack, or dual jack, functionality. The top contact assembly  121   a  provides physical and electrical interfaces, including upwardly extending contact terminals  128 , for connecting to an Ethernet plug. The bottom contact assembly  121   b , which may be omitted in a single port magjack configuration, is physically connected to the top contact assembly  121   a  and includes downwardly extending contact terminals  130 . The contact terminals are manufactured from any material that provides electrical conductivity and is at least somewhat malleable so as to be able to be formed into a particular shape. The contact module  120  is functionally connected to the top PCB  122  through leads  132 , which are soldered, or electrically connected by some other means, onto the top PCB pads  134 . 
     The top and bottom PCBs  122 ,  124  include the resistors, capacitors and any other components associated with the chokes and transformers located inside the component housing  126 , which together comprise the filtering circuitry of the magjack. 
       FIG. 7  illustrates the component housing  126  in a first aspect of the invention. As shown, the component housing  126  is a two piece assembly having a right housing  136   a  and left housing  136   b  for holding the magnetics  151 , or filtering components. A shock absorbing insert  150  for cushioning the magnetics is provided as well. As can be seen, the left and right housings  136   a ,  136   b  are preferably physically identical for reducing manufacturing costs and increased ease of assembly. A latch  138   a  extends from the right sidewall  142 ,  144  of each housing. Preferably, each housing is formed from 30% GF LCP plastic resin or other similar material. The latch  138   a  includes an aperture  139  that engages a corresponding shoulder  138   b  located on the left sidewall  140 ,  146  of each housing. The shoulder  138   b  is configured as a ramp that gradually increases in height as it moves away from the opening  140  of the housing  136   a  and then ends abruptly downwardly. Each housing  136   a ,  136   b , is formed with large opening  140 , akin to a box without a lid. This opening enables the filtering magnetics  151 , to be easily placed within each of the halves. Thus results in increased manufacturing efficiency. 
     The magnetics  151  provide impedance matching, signal shaping and conditioning, high voltage isolation and common-mode noise reduction. This is needed, for example, in 10/100 Base-T Ethernet that utilizes Unshielded Twisted Pair (UTP) transmission cable. The UTP wiring is prone to noise pickup, which may result in conducted and radiated noise emission. The magnetics help to filter out the noise, provide good signal integrity and electrical isolation. 
     The magnetics  151  include a transformer core  158 , PoE choke core  156  and transformer choke core  152 . For 10/100 Mbps communications, a common-mode choke is necessary for a system to pass FCC testing. The choke presents a high impedance to common-mode noise but a low impedance for differential-mode signals. Preferably both transmit and receive channels have a choke where both chokes are wired directly to the RJ-45 connector. Another consideration is crosstalk between transmit and receive channels. Crosstalk may create problems during EMC testing. Accordingly, magnetics with a shield between the two channels can minimize crosstalk. In addition, because of the additional DC current present in the PoE magjack, PoE systems require a resized common mode choke. 
     Because of the above requirements, the present invention provides a unique configuration of transformers and chokes to enable proper functioning of the magjack in all presently available communications systems. As shown in the exemplary embodiment, the magnetics  151  includes multiple core assemblies. The first is a standard or non-PoE core assembly  153  and the second is a PoE core assembly  157 . Each housing,  136   a ,  136   b  receives and stores a standard core assembly  153  and a PoE core assembly  157 . 
     Both types of core assemblies include a pair of transformer cores  158 , such as those sold by Steward, part no. 46TOI45-00P. A transformer choke core  152 , also sold by Steward, part no. 28N0277-11P is located on top of the transformer cores  158 . It is to be noted that the transformer choke core used in this exemplary embodiment includes two holes  154   a ,  154   b  in what may be called a “double donut hole” configuration. By providing the two holes  154   a ,  154   b , the core is able to support multiple transformer channels. Two channels are illustrated herein, but additional channels may be provided if needed. 
     Using the double donut hole configuration lowers the cost of materials since only a single part is required versus two separate chokes, as well as providing an elegant solution for multichannel use. It should be noted that functionally a pair of discrete single-hole choke cores could be used with equal effectiveness, but at a likely increased cost. In another exemplary embodiment (not shown), the PoE core may be split through the center so that an elongated aperture extends between the two holes  154   a ,  154   b . A particular advantage of such a configuration would be to enable the possible automation of the winding process. 
     The PoE core assemblies  157  also include a PoE choke core  156  for providing the necessary size for the increased current of PoE systems. Such PoE transformer cores are also available from Steward, part no. 28T0155-00P.  FIGS. 8-10 , illustrate the wiring diagrams for the transformer wire winding assembly, the transformers and choke wire winding subassembly and the PoE choke wire winding assembly, respectively. 
       FIGS. 11 and 12  illustrate how the component housing  126  is assembled. First, the core assemblies of the magnetics  151  are wrapped in wire as shown in  FIGS. 8-10 . Then, each housing  136   a ,  136   b  receives two core assemblies, including the standard core assembly  153  and the PoE core assembly  157 . The rubber shock-absorbing insert  150  is placed inside one of the housings  136   a . The insert  150  is sized such that a portion of the insert  150  partially extends out from the opening of the housing ( FIG. 12 ). 
     As the housings  136   a ,  136   b  are brought together, the latch  138   a  flexes slightly outwardly and moves up the ramp portion of the shoulder  138   b . As the latch  138   a  crosses over the back edge of the ramp  138   b , the latch aperture  139  fully engages the shoulder  138 . The latch  139  is securely held in place by the flat end of the back portion of the shoulder  138   b.    
     After assembly of the housings  136   a ,  136   b , the shock absorbing insert  150  compresses against the magnetics  151 . As shown in  FIG. 13 , the insert  150  deforms to the point of filling in spaces and crevices between the various transformers and chokes, such as the transformer core  158  and the transformer choke core  152 . The insert  150  also presses these components against the sidewalls of the interior of their respective housings to prevent sudden or hard movement that could possibly break the components or cause the windings to break. Therefore, the insert  150 , which may be made from cellular silicone rubber or other pliable material, provides soft cushioning for the components if needed. 
     Although the present invention has been described in terms of the presently preferred embodiments, it is to be understood that the disclosure is not to be interpreted as limiting. Various alterations and modifications will no doubt become apparent to those skilled in the art after having read the above disclosure. Accordingly, it is intended that the appended claims be interpreted as covering all alterations and modifications as fall within the true spirit and scope of the invention.