Abstract:
A connector for engaging an electrical conductor that includes a wire surrounded by insulation includes a housing formed with a first slot engageable with the wire and including first and second laterally-spaced surfaces having between them a first width that is less than a width of an outer surface of the insulation and greater than a width of the wire. A cover having a second slot engageable with the wire includes third and fourth laterally-spaced surfaces spaced along a length of the conductor from the first and second surfaces, and offset laterally from the first and second surfaces, the third and fourth surfaces having between them a second width that is less than a width of an outer surface of the insulation and greater than a width of the wire.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates generally to a connector that engages an insulated conductor, secures it against displacement, and produces an electrical connection. More particularly, the invention pertains to a connector such as is used in the electrical system of a motor vehicle. 
     Insulation displacement connection (IDC) is a technique employing a connector that engages the insulation surrounding an electrical conductor in order to secure the position conductor against unwanted movement and to produce an electric connection. Conductor strain relief restrains the conductor in the IDC and holds the conductor in place to prevent its movement relative to the IDC interface and potential damage to the interface. It also improves conductor pull force performance by cutting into the insulation when the conductor is pulled vertically or longitudinally. 
     Conventional conductor connectors in the prior art usually include strain relief and position definition features integrated into a mating part. These features often are in the form of bumps on a plastic connector cover, housing or another part of the connector, which bumps are used to form and IDC interface by pushing the conductor into the IDC. Such connectors rely on tolerances between the mating parts and positive mechanical locks to secure the parts mutually. Reliance on dimensional tolerances and mechanical locking permits variability in the position of the conductor relative to the IDC interface and affects the quality of the IDC interface. 
     The magnitude of the contact force varies in conventional IDCs with the diameter of the conductor and insulation. Furthermore, there is no provision in conventional IDCs for outside pressure on the conductor in two perpendicular directions, which would ensure sufficient contact force to accommodate variations in the size of the conductor. By adjusting the offset of the adjacent slots this contact force can be adjusted. A larger offset is be used for smaller conductor sizes; a smaller offset is used for larger conductor sizes. The magnitude of the contact force between the connector and conductor is preferably adjustable by changing the magnitude of the offset between adjacent slots of the connector. 
     It is preferred that a connector rely on mechanical engagement with the conductor insulation to provide repeatable positioning of the conductor relative to the connector and to prevent displacement of the conductor relative to the connector, especially displacement resulting from conductor pulling forces, which is an important requirement of the performance of the IDC. 
     SUMMARY OF THE INVENTION 
     In a connector according to this invention, adjustment of the contact force between the conductor and connector is achieved by providing two or more adjacent, offset opening through which the conductor passes, the offsets producing engagement of the connector with the insulation on the conductor. Larger offsets are used with smaller conductor sizes; smaller offsets are used with larger conductor sizes. The conductor provides at least eight points of contact with the wire conductor. 
     A first component of the connector is a housing having the form of a cube having an open top, two slots, located in axially opposite walls, and two latches used to secure the housing to a cover by bending the latches into contact with a surface of the cover. A second connector component is the cover, whose axial direction is slightly longer than that of the housing and contains slots, which are slightly offset from the slots of the housing. The cover has two relief openings, through which the latches pass, and a top surface, against which the latches become engaged when bent into the latching position. 
     An insulated conductor or wire harness is placed in the slots of the housing component, and the cover is located over the housing such that the conductor passes into the slots of the cover. The cover is then pressed downward until it connects with housing, and the latches are bent over and locked against the cover. 
     The slots of the cover and housing pierce through the insulation and cause the connector to contact the conductor at up to four points per pair of adjacent slots. Because the slots of the adjacent slots pairs are slightly offset mutually, two adjacent slots push the conductor in opposite directions, thereby producing a moment of force, which produces additional normal force on opposite ends of the adjacent slots. The cover presses both the conductor and insulation down into the slots of the housing producing multiple contact points and enhanced strain relief at the wire insulation. 
     A connector, according to this invention, for engaging an electrical conductor that includes a wire surrounded by insulation includes a housing formed with a first slot engageable with the wire and including first and second laterally-spaced surfaces having between them a first width that is less than a width of an outer surface of the insulation and greater than a width of the wire. A cover having a second slot engageable with the wire includes third and fourth laterally-spaced surfaces spaced along a length of the conductor from the first and second surfaces, and offset laterally from the first and second surfaces, the third and fourth surfaces having between them a second width that is less than a width of an outer surface of the insulation and greater than a width of the wire. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       These and other advantages of the present invention will become readily apparent to those skilled in the art from the following detailed description of a preferred embodiment when considered in the light of the accompanying drawings in which: 
         FIG. 1  is a perspective view of a conductor before its insertion into a connector according to this invention. 
         FIG. 2  is a perspective view of the conductor secured to the connector; 
         FIG. 3  is a top view of the connector showing the conductor installed in the connector; 
         FIG. 4  is an end view of the connector and conductor of  FIG. 3 ; and 
         FIG. 5  is a cross section taken at plane  5 — 5  of  FIG. 4 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to the figures, an electrical connector for securing a conductor  6  of insulated wire to the connector includes a hollow rectangular housing  8  having an open top, and a cover  10 , which closes the top. The housing  8  includes a base and four vertical walls, two axial walls  14 ,  18  spaced mutually along the length of the conductor, and two lateral walls  16 ,  20  spaced mutually on opposite sides of the conductor. The conductor  6  may includes a single wire or a bundle of wires  22 . In neither case, the conductor  6  is enclosed by a sheath of insulation material  24 , which is usually in the form of a circular cylinder, preferably of plastic or another resilient material. The housing  8  and connector  10  are formed of electrically conductive metal, preferably a copper alloy such as  5100  or beryllium copper. 
     Each of the axial walls  14 ,  18  is formed with a slot  26 ,  28  directed generally downward from the upper surface  29  toward the base  30 , which is secured to the four walls and closes the bottom of the housing. Preferably the lateral edges of slots  26 ,  28  are aligned mutually. Each slot  26 ,  28  extends through the thickness of the respective axial wall and includes an upper tapered transition portion  32 , whose width decreases as distance along the slot  26 ,  28  from the upper surface  29  toward the base  30  increases. At the lower end of the transition  32 , each slot  26  includes a throat  34 , whose width is less than the outer diameter of the insulation  24  and the radial outer surface of the wire  22 . The lateral walls  16 ,  20 , which are secured to the axial walls  14 ,  18  and to the base  30 , are each formed with a latch  36 ,  40 , respectively, each latch having an contact surface  38 ,  42 . Each slot  26 ,  28  terminates at a semi-circular radius  43 . 
     The cover  10  includes a top  44  and two axial walls  46 ,  48 , each wall being substantially parallel to the axial walls  14 ,  16  of the housing  8  and spaced mutually along the length of the conductor, such that walls  46 ,  48  of the cover overlap and are adjacent the axial walls  14 ,  18  of the housing. The top  44  is relieved locally at each lateral edge  49  to permit a latch  36 ,  40  to extend through the thickness of the top. 
     Each of the axial walls  46 ,  48  is formed with a slot  50 ,  52  directed generally downward from the top  44  toward the base  30 . Preferably the lateral edges of slots  50 ,  52  are aligned mutually and offset laterally from the corresponding edges of the slots  26 ,  28  of the housing  8 , as seen best in  FIGS. 4 and 5 . Width of slot  26  being equal to width of slot  52  and width of slot  28  being equal to width of slot  50 . Each slot  50 ,  52  is formed through the thickness of the respective axial wall  46 ,  48  and includes an lower tapered transition portion  54 , whose width decreases as distance along the slot  50 ,  52  from the lower edge  56  toward the top  44  increases. At the upper end of the transition  54 , each slot  50 ,  52  includes a throat  58 , whose width is less than the outer diameter of the insulation  24  and the radial outer surface of the wire  22 . Each slot  50 ,  52  also terminates at a semi-circular radius  53 . 
       FIG. 1  shows the housing  8  disposed to receive the conductor  6  on the transition surface  32  of the slots  26 ,  28 , and the cover  10  located to contact the conductor  6  at the transition surface  54  of the slots  50 ,  52 . Each latch  36 ,  40  is straight, vertical and aligned with the corresponding relief cutout  49 , which provides space for the latch to extend above the top  44 . 
     Installation of the conductor  6  in the connector begins by placing the conductor on the transition surfaces  32  of the slots  26 ,  28  of the housing  8 , engaging the conductor with the transition surfaces  54  of the slots  50 ,  52  of the cover  10 , and then forcing the cover downward such that the conductor passes into the throats  34  of the housing and the throats  58  of the cover. Throats  34  cut into the insulation  24  at opposite lateral sides as the conductor  6  moves downward along slots  26 ,  28 . Throats  58  cut into the insulation at opposite lateral sides as the cover  10  and its slots  50 ,  52  move downward across the conductor. As the conductor  12  enters and passes through the throats  34 ,  58 , the insulation  22  is compressed and cut locally at each throat by its interference with edges of the throats, and the wire  22  contacts the lateral surfaces of the slots  26 ,  28 ,  50 ,  52 , thereby bringing the wire into direct contact with the sides of the slots. After the conductor  6  passes through the throats  34 ,  58  and the cuts are made through the thickness of the insulation  24 , the length of the insulation  24  and wires  22  that is spaced along the conductor from the slots  26 ,  28 ,  50 ,  52  expands radially outward from the compressed condition to the generally circular cylindrical shape seen best in  FIGS. 1 and 2 . 
       FIG. 5  shows the lateral offsets between the slots  26 ,  28  of the housing  8  and the slots  50 ,  52  of the cover  10 . As the conductor  6  moves downward along slots  26 ,  28 , the throats  34  of the housing cut into the insulation  24  at opposite lateral sides. As the conductor  6  moves upward along slots  50 ,  52 , throats  58  cut into the insulation  24  at opposite lateral sides. As the conductor  6  enters and passes through the throats  34 ,  58 , the insulation  24  is compressed and cut by its interference with edges of the throats. But because the lateral offset  60  located at the axial end shown at the top of  FIG. 5 , surface  62  of slot  50  contacts the wire  22  with a force that is directed leftward, and surface  64  of slot  28  contacts the wire with a force that is directed rightward. The points of contact  62 ,  64  and the contact forces are spaced axially producing a counterclockwise moment, which tends to rotate the conductor  6  counterclockwise with respect to the axis  68  of the conductor within the housing  8 . Similarly, because of the lateral offset  70  located at the axial end shown at the bottom of  FIG. 5 , surface  72  of slot  52  contacts the wire  22  with a force that is directed leftward, and surface  74  of slot  26  contacts the wire with a force that is directed rightward. The points of contact  72 ,  74  and the contact forces are spaced axially producing a clockwise moment, which tends to rotate the conductor  6  clockwise with respect to the axis  68  of the conductor within the housing  8 . The presence of these moments tends to increase the magnitude of contact between the lateral surfaces of the slots and the wire  22 . 
     The correctly installed position of the conductor  6  is reached when the lower edges of the cover  10  are aligned with the base  30  of the housing  8 , as shown in  FIG. 4 . After the housing  8  and cover  10  reach the correctly installed position relative to the conductor  6 , the latches  36 ,  40  are bent laterally inward over the outer surface of the top  44  of the cover such that surfaces  38 ,  42  contact the cover&#39;s top  44 . In this position, the tabs  36 ,  40  secure the cover  10  to the housing  8  and prevent movement of the conductor  6  relative to the connector.  FIG. 2  shows the connector with the conductor  6  installed and the tabs  36 ,  40  bent into the final configuration. 
     In high temperature applications, such as in the engine compartment of a motor vehicle, the housing is preferably of steel, the connector is of a copper alloy, and the walls  46 ,  48  of the cover  10  are fitted within the housing rather than overlapping the exterior surface of the housing. The steel housing does not expand as much as the copper alloy cover due to the elevated ambient temperature and restrains thermal expansion of the cover. This configuration maintains a large magnitude of contact force between wire  22  and the cover slots  58 , and excellent electrical contact between the housing and the cover. 
     In accordance with the provisions of the patent statutes, the present invention has been described in what is considered to represent its preferred embodiment. However, it should be noted that the invention can be practiced otherwise than as specifically illustrated and described without departing from its spirit or scope.