Abstract:
A method secures wire to an electrical contact using an insulation displacement contact (IDC) strain relief cap. The electrical contact has a bifurcated end for engaging and retaining the wire and is engaged with the strain relief cap in securing the wire. The cap attaches to the contact via means on the electrical contact for engaging both the cap and the wire. The wire is secured by placing cap onto the contact, aligning the wire with exit holes, and turning cap until locked into place.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention. 
     This invention relates to an electrical connector for insulation displacement contact (IDC) with insulation conducting wire. The invention finds particular utility in telecommunications where wires terminate in central office and building entrances. 
     2. Description of Prior Art. 
     It is common to find the use of insulation displacement contact (IDC) technology in the electrical connector industry, because it allows rapid and simple connection of conducting wires to terminals without stripping nor crimping. A typical IDC connection is made by disposing an insulated conducting wire perpendicular to a planar wall portion comprising an IDC slot stuffing a wire into the slot such that. edges thereof cut through the insulation and make electrical contact with conducting strands of a wire. The IDC slots are generally formed by opposed edges of the sheet metal wall portion which is necessarily of a certain width to have sufficient strength to support the contact pressure against the edges. 
     Commercially available connectors that utilize insulation displacement contact (IDC) technology provide strain relief for multiple conductors. IDC pins are molded into the connector body which is used to support the strain relief member. These commercially available connectors are, designed to terminate multiple conductors in a single connector. Strained relief for these types of connectors are designed as an intregal part of the connector body securing all conductors within a single strain relief member. Although this technology finds particular applicability when multiple wires are to be connected and unconnected, it does not lend itself to large pin array connectors where individual wires need to be reworked or rerouted without jeopardizing adjacent connections. Strain relief of the individual contacts or pins provide a great benefit during reworking or rerouting of individual wires. 
     SUMMARY OF THE INVENTION 
     It is a primary object of the present invention to provide strain relief for individual IDC pins or contacts. 
     It is another object of the invention to provide individual strain relief pins that make IDC a viable technology for large pin array connectors. 
     A further object of the invention is to provide strain relief for individual pins or contacts to allow for rapid assembly of large pin arrays. 
     Yet a further object of the invention is to provide strain, relief for individual IDC connections to ensure robust electrical connections, while allowing wiring changes and repairs without compromising adjacent electrical connections. 
     It is yet another object of the invention to provide strain relief for individual IDC pins or contacts to replace wire wrap technology on current products. 
     The foregoing objects have been accomplished by providing a tool and an IDC strain relief cap that operates in conjunction with an IDC contact to rapidly retain an insulated wire with the contact. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an isometric back view of a current projection block having wire wrap pins. 
     FIG. 2 is an isometric front view of a current projection block having wire wrap pins. 
     FIG. 3 is an exploded view of an IDC connection and tool according to the disclosure. 
     FIG. 4 is a side elevation view taken generally along line  4 — 4  of FIG.  3 . 
     FIG. 5 is an enlarged sectional view of a portion of the IDC connection according to the disclosure. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG.  1 . Illustrates the back  10  of a relatively standard protection block  12  with wire wrap pins  14  projecting through cylindrical openings  16  (FIG. 2) on the front  18  of block  12 . In the prior art, wire not shown, is wrapped in a spiral fashion around the pins  14  to provide contact. As described later in the specification, the disclosure of the present invention can make use of protection block  12 . 
     FIG. 3 illustrates an IDC pin and strain relief cap assembly  20  having an IDC contact  22  terminating at one end in a retainer clip  24  that is. engageable with a strain relief cap  26  to retain a wire  28 . IDC contact  22  includes a cylindrical hollow body portion  30  having a significant length to engage and be retained by a pin  14  on protection block  12 . Opposite from body portion  30  of IDC contact  22 , retaining clip  24  includes a bifurcated end  32  having a slot  34  defined by a pair of arms  36  and  38 . to grasp and retain wire  28 . Wire  28  is of a type commonly used to transmit electricity or signals and includes a center portion  40  made, for example, of solid copper that is surrounded by appropriate insulation  42  to protect center portion  40  from the exterior environment. 
     As depicted in FIG. 5, slot  34  of bifurcated end  32  is defined by an entry section  44  having a pair of angled surfaces  46  and  48  terminating at an end portion  50  defined by parallel sides  52  and  54  and a curved end  56 . Parallel sides  52  and  54  are spaced a distance apart that is slightly less than the diameter of center portion  40  of wire  28 . Curved end  56  is of a shape to conform to a portion of the wire  28 . In assembly the wire moves into bifurcated end  32  between arms  36  and  38 , by angled surfaces  46  and  48  into end portion  50  whereby parallel sides  52  and  54  cut through the insulation  42  of wire  28  thereby malting contact with center portion  40  of wire  28 . The wire is moved in a direction until contact is made between wire  28  and end portion  56  of bifurcated end  32  of IDC contact  22 . 
     IDC contact  22  is preferably made of a standard metal material such as a steel alloy coated with brass to transmit electrical signals or electricity to the pins  14 . In the preferred embodiment, retaining means  58  comprises retaining cams  60  and  62  connected to arms  36  and  38  of bifurcated end  32 , which cams are inflexible and extend outwardly at an angle as shown in FIGS. 3 and 5. These retaining means  58  will be discussed in greater detail in reference to assembly of strained relief cap  26  with IDC contact  22  of assembly  20 . 
     Strain relief cap  26  includes a body portion  64  defining a cavity  66  to receive bifurcated end  32  of IDC contact  22 . Body portion  64  includes gripping means  68  illustrated as a pair of locking windows  70  and  72  oppositely spaced on body portion  64  to receive and retain retaining cams  60  and  62  when bifurcated end  32  is located within cavity  66 . 
     In a preferred embodiment, the retaining cams  60  and  62  are located diametrically opposed from one another. The locking window  70  and  72  are similarly located to correspond to the location of retaining cams  60  and  62 . As best shown in FIG. 3, the locking windows may be of a shoe-shape or “L” configuration, each having a longitudinally extending entry slot  74  that terminates in a laterally or circumferentially extending slot  76  to retain retaining cams  60  and  62  as illustrated in FIG.  5 . In its preferred embodiment, strain relief cap  26  is a cylindrical, cup-shaped member having axially extending entry slots opening into the open end of the cap. Wire slots  78  and  80  have been positioned diametrically opposed from one another to receive wire  28 . It should be appreciated that only one wire slot  78  is needed, if it is chosen to terminate center portion  40  within cavity  66  of strain relief cap  26 . Wire slots  78  and  80  may be configured similar to locking windows  70  and  72 . Further, although bifurcated end  32  may extend upwardly from a side surface of contact  22 , it is preferred to bend it in a know matter relative to the side surface toward the axis of cylindrical portion  30  and then upwardly along the axis to center the bifurcated end  32  relative to cylindrical portion  30  as illustrated in FIG.  3 . In this manner a cylindrical cap  26  can be positioned axially around a portion of cylindrical portion  30 . 
     In assembly, IDC contact is engaged with a pin.  14  extending outwardly from a block  12 . The end of a wire  28  is located within bifurcated end  32 . a distance to ensure contact of the wire across the entire length of groove  34  of bifurcated end  32 . The wire is moved downwardly between angled surfaces  46  and  48  to a position in contact with parallel sides  52  and  54 . Strain relief cap  26  is then located over bifurcated end  32 , with bifurcated end  32  within cavity  66 . The cap  26  is aligned with bifurcated end  32  to ensure that longitudinally extending entry slot  74  of locking windows  70  and  72 , are respectively aligned with retaining cams  60  and  62 . Additionally, the longitudinally extending entry slot  74  of wire slot  78 , must be aligned with wire  28 . The cap is then moved downwardly over bifurcated end  32  until contact is made with the top portion of retaining cams  60  and  62 , with the upper portions of circumferentially extending slot  76  of locking windows  70  and  72 . Wire slot is so configured that at this position, room is provided between the upper surface of circumferentially extending slot  76  of wire slot  78  with the insulation  42  of wire  28 . If a second wire slot  80  is provided in retaining cap  26 , this slot will be configured similar to wire slot  78 , allowing for the wire to extend through the retaining cap. It should be appreciated that the wire slot  80  is not needed and that wire  26  may terminate within cavity  66  of retaining cap  26 . Once contact is made between the upper surfaces of retaining cams  60  and  62  with the upper surfaces of circumferentially extending slots  76  of locking windows  70  and  72 , the cap may then be twisted as shown in FIG. 3, in a clockwise direction to lock retaining cams  60  and  62  at the end portion of locking windows of  70  and  72  to thereby releasably retain cap  26  relative to contact  22 . 
     As is known to those skilled in the art, retaining cams  60  and  62 , along with circumferentially slot  76  of locking windows  70  and  72 , may be so constructed as to ensure tight and relatively permanent engagement of cap  26  relative to contact  22 . 
     It is possible to construct cap  26  in other configurations other than cylindrical. The significance of the configuration of the cap is to ensure the presence of the longitudinally extending entry slot  74  and circumferentially extending slot  76  to retain the retaining cams  60  and  62 . It is also necessary to ensure that at least one other slot  78 , having a similar configuration, is provided so that during assembly of cap  26 , relative to contact  22 , the retaining cams  60  and  62  and wire  28  may move in a general longitudinal direction along longitudinally extending entry slots  74  and then be free to move in a general lateral or circumferential direction along circumferentially extending slots  76  of locking windows  70  and  72  and wire slot  78 , and  80  if provided. If, for example, cap  26  would be square or rectangular, retaining cams  60  and  62  would have to be long enough to continue engagement with body portion  64  of cap  26  during twisting movement of cap  26  relative to contact  22 . 
     To disassemble cap  26  from contact  22 , a reverse, or clockwise twisting action as shown in FIG. 3, will be employed until wire  28  and retaining cams  60  and  62  are aligned with the respective longitudinally extending entry slots  74  and then the cap may be moved longitudinally upward away from the contact, thereby exposing the wire within the bifurcated end  32 . 
     It should be appreciated that the cap  26  is also so constructed to allow for automated assembly of assembly  20  with pins  14 . To this end, it is desirable, to design the contacts  22  in cap  26  in a consistent manner to allow for first placement of the wire in the slots  34 , and then rapid movement and twisting of the cap  26  relative to the contact  22 . Insertion of the contact  22  into the respective pin may occur before or after securement of cap  26  to contact  22 . 
     Further, end  30  of contact  22  is constructed in a known manner to be engaged with or disengaged from a pin  14  in a rapid manner when it is necessary to change contact points for the wires  28  relative to the pins  14  on block  12 . Retention means in the form of an annular indentation  82  on end  30  can be used for this purpose. 
     Up to this point in the detailed description of the invention, the disclosure is similar to that disclosed in co-pending U.S. patent application Ser. No. 09/482,898 filed on the same day by the co-inventors and assigned to the assignee of this application. As illustrated in FIGS. 3 and 4, the top of relief cap is configured to have a raised portion  84  extending longitudinally away from the cap  26  to form a gripping section. 
     An assembly tool  86  is provided having a holding section  88  with a slot  90  configured for mating engagement with raised portion  84  as best seen in FIGS. 3 and 4. Tool  86  includes another portion  92  secured to section  88  that may be configured to be gripped by a hand for turning tool  86  laterally or circumferentially in a clockwise or counterclockwise rotation to turn cap  26  relative to contact  22 . In this way, more torque may be applied to cap  26  to secure it to or release it from contact  22 . 
     Further, the portion  92  to be held may be moved a distance away from holding section  88  by a connecting shaft  94  to allow for insertion of the section  88  and a cap  26  into space limited areas where a plurality of pins  14  are located on a block  12 . Without assembly tool  86 , it could be difficult to locate these caps  26  on contacts  22  and turn them by fingers on the human hand. 
     Additionally, in instances where the cap  26  is already secured to a contact  22  away from a block  12 , tool  86  allows for gripping of the strain relief assembly  20  and locating it on a pin  14 . In such instances contact is made with slot  90  and raised portion  84  and the strain relief assembly is located on a pin  14  projecting upwardly through the hollow portion  30 . Force can be exerted by tool  86  to move the contact into engagement with pin  14  against the resistance of indent  82 . Also the connected part can thereafter be rotated, in assembly to align wire  28  relative to block  12  and the other connections.