Abstract:
A robust and waterproof wires-to-meter connection that provides an apparatus for conducting signals from several signal-carrying, bundled wires to a circuit member that is mounted within the interior of a sealed case, and in particular an assembly for conducting the signals while providing a robust, compact and water-resistant connection between the internal main circuit and the entry wires.

Description:
BACKGROUND INFORMATION 
     This invention relates to a meter for motorcycles or the like, and in particular to an approach to connecting the individual wires of a wire bundle to an indicator dashboard or similar meter (hereafter collectively referred to as “dashboard”) that is mounted to the motorcycle bar for displaying information (speed, temperature, etc.). 
     The wire bundle comprises several insulated wires that emanate from connections to detectors or sensors that are located on the vehicle away from the dashboard. The wires are bundled within a protective outer sheath. The end of the sheath enters the dashboard case and the individual wires are connected in some manner to the main circuit board of the dashboard. 
       FIG. 1  illustrates a prior art approach for connecting the individual wires of a wire bundle to an indicator dashboard. The case  1  of the dashboard is typically mounted in front of the motorcycle bar to enable easy viewing of the dashboard display by a rider. 
     A battery  6  is secured in a mounting in the case by a cover  7  and O-ring  5 . The case  1  includes and interior  12  that houses the main circuit board and associated display components.  FIG. 1  shows the bottom of the case housing  13  and a resilient seal  3  that fits between the housing and a case cover (not shown) that includes a transparent lens for viewing the display that is housed in the case. 
     A wire bundle  11  is enclosed in a protective sheath  10  and enters an opening in the back of the case  1 . As shown in the exploded view of  FIG. 1 , the termini of these wires  11  (hereafter sometimes referred to as “entry” wires) are connected to the underside of an interface printed circuit board (PCB)  2 . Near one edge of that PCB, the ends of several, smaller “internal” wires  15  are joined to the upper surface of the interface PCB  2 . The internal wires  15  are bent to extend away from and generally parallel to the plane of the PCB. The outer ends of the internal wires  15  are crimped into a connector  14  that connects to the main circuit board (not shown) that is carried inside the case. 
     As part of the assembly process for this device, the PCB  2  is seated inside of a well  16  that is defined in the interior  12  of the case  1 . The well  16  is a compartment that is defined by the back wall of the case and by four, inwardly projecting thin sidewalls  17  that define a cubical volume within which the PCB  2  is secured. The wire bundle  11  extends through the opening in the back wall of the meter case to protrude inside the well  16 , for connection to the interface PCB as noted above. The well  16  is filled with epoxy for the purpose of providing strain relief and preventing water from migrating into the case. 
     The prior art assembly process for connecting the internal wires  15  between the upper surface of the interface PCB  2  and the main circuit board, as noted above, requires soldering of the ends of the wires  15  to the PCB and crimping the other ends of the wires into a connector that is in turn inserted into the mating connector carried on the main circuit board. To accomplish the insertion, and to facilitate handling of the wires  15  during assembly, the length of the wires between the PCB and connector  14  is made slightly longer than the distance between the wire ends at the PCB and the connector when finally assembled. Accordingly, each of the wires is necessarily bent slightly during and after assembly. Controlling the final configuration of the bends is difficult because each individual wire is free to buckle in any direction (upwardly, downwardly or sideways). Sideways buckling can be particularly troublesome because such a “stray” buckled wire can obstruct assembly or hinder connection of other components within the compact dashboard case. Thus, extra assembly time and cost is required to carefully control the buckling direction of all of the wires to avoid strays. 
     The prior art device is also susceptible to failure attributable to vibration and penetration of moisture into the case. In particular, the solder joints of the internal wires can be stressed by the continuous vibration occurring during operation of the motorcycle, and eventually separate from the PCB  2  at the location where the wire ends are soldered to the PCB. One way to address this problem is to reduce the mass of the wires (hence reduce the damaging energy transmitted via vibration) by using very small diameter wires. However, when wires are connected to the PCB using modern lead-free solders, the attendant higher melting points of such solders calls for relatively stiffer insulating jackets over the wire than is required with lead-based solders. The stiffer insulation in turn increases the overall mass of the wires, and thus returns the damaging vibration problem. 
     Finally, despite the presence of sealing epoxy in the well  16  mentioned above, some moisture may penetrate the well, and the presence of the internal wires that extend from the PCB in the well to the connector  14  on the main circuit board provide between the wires a capillary path for the moisture to flow to the connector  14  and damage the main circuit board. This capillary flow seems to be enhanced by the presence of an array of grooves  20  formed in the upper edge of the prior art sidewall  17  over which the internal wires  15  pass, each groove receiving a wire. 
     SUMMARY OF THE INVENTION 
     The invention disclosed here provides an apparatus for conducting signals from several signal-carrying, bundled wires to a circuit member that is mounted within the interior of a sealed case, and in particular an assembly for conducting the signals while providing a robust, compact and water-resistant connection between the internal main circuit and the entry wires. 
     Also provided is a robust method of conducting signals from several signal-carrying wires to a circuit member that is mounted within the interior of a sealed case. 
     Other advantages and features of the present invention will become clear upon study of the following portion of this specification and drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an assembly view of components used in a prior art technique for connecting a wire bundle inside of a dashboard. 
         FIG. 2  is a perspective view, with an enlarged detail showing a preferred embodiment of the connection technique of the current invention.  FIG. 2  shows the underside of a conductor assembly component of the present invention. 
         FIG. 3  is a perspective, top view of the conductor assembly component. 
         FIG. 4  is a cut-away, top perspective view of a dashboard case with which the preferred connection technique of the current invention is implemented. 
     
    
    
     DETAILED DESCRIPTION 
       FIGS. 2-4  illustrate a preferred embodiment of the present invention.  FIG. 2  includes a perspective view and an enlarged detail showing the underside of a conductor assembly  22  component of the present invention. The conductor assembly  22  includes a rigid portion  24  which can be formed of conventional printed circuit board material. 
     The rigid portion  24  is planar and generally square shaped. As seen in  FIG. 4 , the rigid portion  24  fits inside of a cubical well  16  that is a compartment formed in the interior  12  of the case  1 . The well  16  is defined by four, inwardly projecting thin sidewalls  17  that define the cubical volume within which the rigid portion  24  is seated. The back of the dashboard case defines a protruding cylinder  30  that includes a bore or opening  32  through which the sheath  10  of the wire bundle extends. 
     As best shown in  FIG. 4  and the detail view of  FIG. 2 , the individual wires  11  of the wire bundle terminate at the underside of the rigid portion  24  of the conductor assembly  22  ( FIG. 2 ). The exposed terminus of each wire  11  passes into a through-hole in the conductor assembly  22  and is soldered to a flanged, conductive sleeve  34  that lines the hole to thus electrically connect the wires  11  with conductive traces  36  ( FIG. 4 ) that are printed on the upper surface of a flexible portion  23  of the conductor assembly. 
     The flexible portion  23  of the conductor assembly  22  is preferably a flexible plastic substrate having the conductive traces  36  printed thereon. The flexible portion  23  is, like the rigid portion  24 , planar in the sense that it is a thin, ribbon-like member having flat upper and lower surfaces. In this embodiment, the flexible portion  23  overlays and is bonded to the rigid portion  24 . At one edge of the rigid portion  24 , the flexible portion  23  extends away from the rigid portion to a remote end  38  ( FIG. 3 ) that is configured for attachment to the main circuit board of the dashboard. 
     With reference to  FIG. 4 , the thin, ribbon-like flexible portion  23  of the conductor assembly is a unitary element, the bending behavior of which is readily controlled (as opposed to the unpredictable, individualized buckling of the several, separate internal wires  15  as discussed above). The flexible portion  23  most readily bends in a direction transverse to its long axis, such as shown at bends  42  in  FIG. 4 . Problematic sideways buckling or bending (as discussed above) of the flexible portion is thus quite unlikely during the assembly process. Importantly, the combination of the relatively low mass of the flexible portion  23  (as compared to that of the prior art internal wires  15 ) and the elimination of soldered internal-wire-to-PCB connections effectively eliminates the damaging vibration problem of the prior art. 
     Moreover, the composition of the flexible portion is such that it holds its shape once bent. This feature thus enables the flexible portion  23  to be bent at specific locations before or during assembly (such as bends  42  in  FIG. 4 ) so that once connected, the flexible portion  23  will readily assume a predicted location within the case. For instance, the controlled location of the bends  42  shown in  FIG. 4  results in the formation of a predictably sized and located trough-like volume into which volume other internal components can located within the compact dashboard case  1 . 
     The flexible portion  23  conforms to the shape of a sidewall  17  of the well and extends across a flat, smooth upper edge of a sidewall  17 . That is, unlike the prior art, the flat upper edge of the wall  17  over which the flexible portion  23  passes has no grooves or other irregularities that might provide gaps between the flexible portion  23  and wall  17 , which gaps could enable moisture that may enter the well to penetrate outside of the well  16  and to the main circuit board as described above with respect to the prior art. 
     Once the flexible portion  23  of the conductor assembly  22  is properly located as shown in  FIG. 4 , fasteners that extend through holes  40  provided through the conductor assembly  22  are used to anchor an end of the conductor assembly (that is, the rigid portion  24  and overlying part of the flexible portion  23 ) to the interior of the well  16 . A square flat cover plate (not shown) that conforms to the shape of the well  16  is then secured over the upper edges of the well sidewalls  17  to enclose the well, which is filled with epoxy to seal the well and provide strain relief to the wire junctions. 
     It is noteworthy that the planar flexible portion  23  thus passes between the substantially flat, opposed surfaces of the sidewall  17  and cover plate, thereby allowing the flexible portion to extend from the well without creating any gaps for enabling moisture to move out of the well in the event that the epoxy seal fails or is damaged in a manner that allows outside moisture to enter the well. 
     While the foregoing description was made in the context of a preferred embodiment, it is contemplated that modifications to this embodiment may be made without departure from the invention as claimed.