Abstract:
A strain relief for a wire inserted through the cap of an insulation displacement connector including a tab hingeably mounted on the connector for selective movement between an unlocked position and a locked position. When the tab is in the unlocked position, the tab receives the wire after the wire passes through the connector, and when the tab is in the locked position, a restraining force is applied to the wire thereby inhibiting the removal of the wire from the connector.

Description:
FIELD OF THE INVENTION 
     This invention relates to a tool-less insulation displacement connector having a cap, and in particular to a wire strain relief mechanism attached to the cap for inhibiting the removal of wires connected to the insulation displacement connector. 
     BACKGROUND OF THE INVENTION 
     Telephone lines, which are carried by electrical conductors known as tip ring wire pairs, originate from a central office (CO) and are aggregated at a particular point in a building prior to being distributed and connected to various types of telephone equipment, such as, for example, telephones, fax machines, modems etc., in the building. The tip ring wire pairs, which generally enter the building as part of a multi-conductor cable, are connected to a junction box known as, for example, a building entrance protector (BEP), or network interface unit (NIU). Within the junction box, the individual telephone line tip ring wire pairs are separated from the cable, individually connected to a connector block, and made available for further electrical connection and distribution. 
     The connector block, also known as insulation displacement connector (IDC) block, may be the ubiquitous punch down connector block, also known as a 66-type connector block, or the tool-less insulation displacement connector block utilizing push cap connectors, such as that described in U.S. Pat. No. 4,913,659 dated Apr. 3, 1990, the entire disclosure of which is incorporated herein by reference. Such a connector block is commercially available under the product designation SC99 from Lucent Technologies Inc. 
     The tool-less insulation displacement connector block includes an IDC type connector on one side of the connector block having a terminal disposed therein for connecting a tip ring wire thereto. Opposite each IDC connector on the other side of the connector block is a matching, electrically connected wire wrap terminal, such that a wire connected on the wire wrap side may be connected to another wire coupled to the IDC side of the block. The tip and ring wires that are coupled to the IDC connector are strain relieved by the compression of the terminal within the IDC that holds the bare wire which has been stripped of its insulation layer. 
     A significant drawback of the prior art IDC connectors is that the terminal in the connector provides minimal strain relief on the inserted tip ring wire. As a result, when a pulling force is applied to the tip or ring wire, the wire can be dislodged from the terminal and disconnected from the connector. 
     Another drawback encountered in prior art IDC connectors is the need to trim excess wire that protrudes through and beyond the cap once the wire is secured within the IDC. These trimmings are generally short, difficult to handle wire lengths that can easily fall into the BEP or NIU or other associated equipment, posing the risk of causing short circuits or other malfunctions. 
     Thus, it is desirable to provide a better strain relief mechanism for wires connected to an IDC connector in a connector block to prevent the tip ring wires from being disconnected from the connector in response to a pulling force, and to eliminate hazardous wire trimmings. 
     SUMMARY OF THE INVENTION 
     The present invention is directed at overcoming the shortcomings of the prior art. The present invention is directed to a mechanism for providing strain relief for a wire inserted through a connector and includes a tab hingeably mounted on the connector for selective movement between an unlocked position and a locked position. When the tab is in the unlocked position, the tab receives the wire after the wire passes through the connector, and when the tab is in the locked position, a restraining force is applied to the wire thereby inhibiting the removal of the wire from the connector. Also, a plurality of ribs may be disposed on the tab and connector in a position so that when the tab is in the locked position the ribs contact the wire thereby applying an additional restraining force to the wire. In this way, there is provided strain relief for the wire inserted through the connector thereby inhibiting the removal of the wire from the connector. 
     Additionally, the tab includes a provision for limiting the length of wire that protrudes from the cap, thereby eliminating the need for trimming errant wire ends. 
     Other objects and features of the present invention will become apparent from the following detailed description, considered in conjunction with the accompanying drawing figures. It is to be understood, however, that the drawings, which are not to scale, are designed solely for the purpose of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING FIGURES 
     In the drawing figures, which are not to scale, and which are merely illustrative, and wherein like reference numerals depict like elements throughout the several views: 
     FIG. 1 is a side elevational view of a tool-less wire strain relief mechanism constructed in accordance to the present invention; 
     FIG. 2 is a side elevational view of the tool-less wire strain relief mechanism of FIG. 1 in the closed position; 
     FIG. 3 is a top view of the tool-less wire strain relief mechanism of FIG. 1; and 
     FIG. 4 is a top of the tool-less wire strain relief mechanism of FIG.  2 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to FIGS. 1-4, there is shown a tool-less wire strain relief mechanism  1  constructed in accordance to the present invention. Strain relief mechanism  1  includes a tab  3  which is hingeably mounted on a cap  13  of an IDC connector  10 . Tab  3  includes a surface  31 , preferably having formed thereon a channel  33  for receiving a wire  11  which—as part of the process of inserting wire  11  into connector  10  for electrical and mechanical connection to a terminal strip  15  within connector  10 —is passed into cap  13  through an entrance aperture  17 , passes within and through cap  13  in a wire passage  29 , and exits through an exit aperture  19 . Upon exit, wire  11  then extends beyond cap  13  for a predetermined extent along tab  3 , within channel  33  if so provided. As used herein the term wire means any elongated conductor, insulated or non-insulated, commonly encountered in the electrical and/or electronic arts. 
     A stop wall  5  is disposed on a first end  4  of tab  3  for limiting the extend to which wire  11  extends beyond cap  13  within channel  33  as the wire  11  is passed through cap  13  as described above. A latch  7  is disposed on the top portion of stop wall  5  for locking tab  3  against cap  13  in a locked position, described further below, via mating engagement with a notch  21  formed on a side surface of cap  13 . Protruding from the opposite side of stop wall  5  is a knob  25  used for gripping tab  3  and moving tab  3  between a first, unlocked position (FIGS. 1 and 3) and a second, locked position (FIGS.  2  and  4 ). 
     Within channel  33  there are preferably, although not necessarily, disposed a plurality of ribs  27 . Also preferably disposed on cap  13  is one or more ribs  27 ′. Ribs  27  and  27 ′ are dimensioned and positioned so that when tab  3  is in a locked position, ribs  27  and  27 ′ contact wire  11  for assisting in the retention of wire  11  in channel  33 , as described in more detail below. 
     A second end  6  of tab  3  includes an upper edge surface  38  and a lower edge surface  39 . Upper edge  38  and lower edge  39  preferably have respective slopes so that they converge generally at a point  40  on second end  6  of tab  3 . Second end  6  of tab  3  is connected to a hinge support  9  via a hinge  23 . As cap  13  is preferably formed of a plastic material, hinge  23  is preferably a living hinge, permitting cap  13  to be injected molded in one manufacturing step. The person of skill, however, will recognize that the present invention may implemented in numerous ways, such, as for example, with tab  3  being a separate assembly, removeably or fixedly mounted to cap  13 . 
     Referring now to FIGS. 1 and 2, hinge support  9  is preferably trapezoidal in shape, having a wide surface  35  that is fixedly attached to or formed on cap  13  at a point that is below wire exit aperture  19  so that when tab  3  is in the unlocked position, channel  33  of tab  3  is substantially collinear with wire passage  29  within cap  13 . Hinge support  9  also has a narrow edge surface  37  that is adjacent to tab  3 . Narrow edge  37  is dimensioned and shaped so that when tab  3  is in the unlocked position, lower edge surface  39  of tab  3  contacts narrow edge surface  37  of hinge support  9 , thereby supporting tab  3  and preventing the further rotation of tab  3  in a direction away from cap  13 . In this way, the alignment of channel  33  and passage  29  is maintained when the tab  3  is in the first, unlocked position. 
     Disposed on hinge support  9  at a point intermediate narrow edge  37  and wide edge  35 , and adjacent wire output  19 , is a sloped edge  36 . Sloped edge  36  is dimensioned and shaped so that when tab  13  is in the locked position, upper edge  38  generally confronts sloped edge  36 . Of course, other geometries of tab  3  and hinge support  9  are possible, as a matter of design choice. 
     Hinge  23  connects point  40  of tab  3  to the point on hinge support  9  where narrow edge  37  meets sloped edge  36 . As mentioned above, in a preferred embodiment, hinge  23  is a living hinge but may be a hinge of any type that facilitates the rotation of tab  3  between the locked and unlocked positions, as further described below. 
     The operation of strain relief mechanism  1  will now be described. Initially, as best seen in FIGS. 1 and 3, tab  3  is in the unlocked position, in which channel  33  of tab  3  is in substantially collinear alignment with wire passage  29 . Tab  3  is supported in this alignment by hinge support  9 , which prevents the further rotation of tab  3  away from cap  13 . Wire  11  is inserted into wire passage  29  of cap  13  through wire input aperture  17  and is urged through wire passage  29 , and out through wire exit aperture  19 . Upon exiting wire exit aperture  19 , wire  11  enters channel  33  and continues until it contacts stop wall  5  at which point wire  11  is fully inserted in tab  3 . Knob  25  is then gripped and tab  3  is rotated from the unlocked position toward cap  13  to the locked position, bending wire  11 . In the locked position, latch  7  mates with notch  21  thereby securing tab  3  to cap  13 . No trimming of the portion of wire  11  that extends beyond cap  13  is needed. Of course the person of skill will recognize that numerous other means of releasably retaining the tab in the locked provision may be provided, such as for example a snaps, mating detents and protrusions, clips, and the like. 
     When cap  13  is in the locked position, the section of wire  11  disposed within cap  13  in passage  29 , and the section of wire  11  that is disposed in channel  33  of tab  3  are no longer collinear. The bending of wire  11  brought about by the rotation of tab  3  into the locked position strain relieves wire  11 , in that removing wire  11  from connector  10  when bent requires a greater force than that necessary to overcome the gripping force applied by the terminal strip  15  within connector  10 , which gripping force was the sole retaining force in prior art IDC connectors. 
     Also, when in the locked position, and if so provided, ribs  27  disposed on tab  3  and ribs  27 ′ disposed on cap  13  press into wire  11 , thereby providing additional restraining force on wire  11  to further inhibit the removal of wire  11  from connector  10 . Accordingly, by providing strain relief mechanism  1  of the present invention, wire  11  is better secured within connector  10  so that wire  11  will not be easily dislodged from connector  10  by a pulling force applied to wire  11 . 
     The person of skill will recognize that the wire  11  is preferably passed through cap  13  and locked via tab  3  prior to the wire  11  being brought into engagement with terminal strip  15  in connector  10 . However, the wire  11  may first be positioned as shown in FIGS. 1 and 3 in accordance with the description thereof above, then brought into engagement with terminal strip  15  in the art recognized manner. Tab  3  may then being brought into the locked position. The point at which the wire is strain relieved by the present invention is a matter of choice, that is, the wire may thus be strain relieved before contacting the terminal strip or after, without departing from the scope of the invention. 
     Thus, while there have been shown and described and pointed out fundamental novel features of the invention as applied to preferred embodiments thereof, it will be understood that various omissions and substitutions and changes in the form and details of the disclosed invention may be made by those skilled in the art without departing from the spirit of the invention. It is the intention, therefore, to be limited only as indicated by the scope of the claims appended hereto.