Abstract:
An electrical contact includes a contact body having a mating portion and a barrel portion configured for receiving an electrical conductor. The barrel portion includes a wall defining a bore having a closed end and open end, and the bore includes a core receiver portion for receiving the core of an electrical conductor and a plug receiver portion adjacent the closed end of the bore. A hole is formed in the barrel portion proximate the closed end of the bore and extending into the plug receiver portion of the bore through the wall. A plug has a body portion configured to be inserted into the bore and to engage the plug receiver portion of the bore. The plug is disposed in the end of the plug receiver portion and is further configured to seal the plug receiving portion of the bore and the hole from the rest of the bore.

Description:
RELATED APPLICATIONS 
     This application is a Continuation application of U.S. patent application Ser. No. 13/800,745, entitled “ENVIRONMENTALLY SEALED CONTACT”, filed Mar. 13, 2013, which application is herein incorporated by reference in its entirety. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to electrical contacts. Specifically, the invention relates to apparatus and methods for environmentally sealed electrical contacts for use in contaminating environments. 
     BACKGROUND OF THE INVENTION 
     Electrical contacts are conventionally provided as a means to provide separable continuity between the electrically conductive core of an insulated electrical wire and an electrical terminal, conductive core of another insulated electrical wire, or other device. They are used, for example, in lieu of solder joints for providing an electrical connection. The electrically conductive cores are typically composed of a conductive metallic material such as, copper, silver, gold, aluminum, their alloys, or the like. The cores may or may not be plated with a conductive-metal plating material. 
     Electrical contact assemblies often take a form in which a male or female mating portion and a barrel portion are generally aligned along a common axis. The contact is generally designed as either a male pin configured to be axially inserted into a female socket, or a female socket into which a male pin is to be inserted. In either configuration, the purpose of mating the male pin and the female socket is to complete an electrical circuit. The barrel portion or barrel has an axially extending tubular bore that is configured to receive and provide an attachment location for the core of an insulated electrical wire. When the barrel is of the type described as a closed barrel, the electrical contact is typically gold plated. For a plated contact, a small hole is radially disposed through the tubular wall of the barrel near the bottom end of the closed axially extending bore. This hole is required to allow full surface contact with plating solutions during the plating or manufacturing process. 
     During the assembly of the electrical contact to the end of an electrical wire, the insulation is stripped from the tip of the wire to expose a short length of the electrically conductive core of the wire. The short length of exposed core is then inserted into the axially extending bore in the tubular barrel of the electrical contact. The core of the wire may be either stranded or solid. The tubular wall of the barrel is then typically crimped into contact and electrical continuity with the bare tip of the core of the wire that is within the axial cavity. In some connector assemblies, the tubular barrel is also deformed, typically by crimping, into a hermetically sealing contact with the insulated coating on the wire. 
     As mentioned above, a hole, sometimes referred to as a bleeder hole, is disposed through the tubular wall of the barrel to facilitate plating. Consequently, the tubular bore of the closed barrel and the exposed core of the wire are partially exposed to the environment as a result of the hole. This hole produces an undesirable pathway for environmental contaminants, such as water or corrosive chemicals, to propagate to the conductive core of the wire. Entry of such contaminants can corrode the wire core, increase the electrical resistance value of the core/barrel interface, embrittle the core, or otherwise degrade the quality or longevity of the electrical and physical properties of the contact assembly. 
     Previous attempts to environmentally seal the bleeder hole have proven to be costly or have resulted in degradation of the core/bore interface. One ineffective solution involved placing a silver or malleable sleeve between the electrically conductive core of the wire and the bore of the barrel. Such a solution is costly due to the silver and only provided a moderate performance in environmentally sealing the contact assembly. Also, with such an arrangement, electrical conductivity between the core and the bore of the barrel was diminished and the contact resistance increased. Additionally, tensile strength of the mated wire and contact was diminished by the addition of the silver sleeve. 
     Another ineffective solution required placing a sleeve over the barrel of the contact assembly. While this avoided degrading the electrical connection of the core to the bore of the barrel, the loose outer sleeves could be lost or separated from the connector assembly prior to crimping them in place. Additionally, the loose outer sleeves often required complex geometries to ensure an adequate seal when applied with relatively complex crimping profiles. 
     Therefore, there is a need for an effective environmentally sealed contact that yields excellent electrical conductivity as well as a robust physical design while being generally free of loose parts or sealing sleeves. 
     SUMMARY OF THE INVENTION 
     In one embodiment of the invention, a contact body having a mating portion and a barrel portion configured for receiving an end of an electrical conductor is provided. The barrel portion includes a wall defining a bore having a closed end and open end. The bore includes a core receiver portion for receiving the core of an electrical conductor and a plug receiver portion is adjacent the closed end of the bore. A hole is formed in the barrel portion proximate the closed end of the bore and extends into the plug receiver portion of the bore through the wall. A plug has a body portion configured to be inserted into the bore and to engage the plug receiver portion of the bore. The plug is further configured for being inserted into an end of the plug receiving portion to seal the plug receiving portion of the bore and the hole from the rest of the bore. The plug being disposed in the end of the plug receiver portion. An insulation receiver portion is disposed near the open end of the bore. A primary crimp region is disposed radially coincident to the core receiver portion and is configured to receive one or more crimp distortions. A secondary crimp region radially coincident with the insulation receiver portion is configured to receive one or more crimp distortions. 
     In another embodiment of the invention, an electrical contact assembly is provided. The electrical contact assembly includes a contact body having a mating portion and a barrel portion configured for receiving an end of an electrical conductor. The barrel portion including a wall defining a bore having a closed end and open end. The bore includes a core receiver portion for receiving the core of an electrical conductor and a plug receiver portion adjacent the closed end of the bore. A hole is formed in the barrel portion proximate the closed end of the bore and extends into the plug receiver portion of the bore through the wall. A plug has a body portion configured to be inserted into the bore and to engage the plug receiver portion of the bore. The plug is further configured for being inserted into an end of the plug receiving portion to seal the plug receiving portion of the bore and the hole from the rest of the bore. The plug is disposed in the end of the plug receiver portion. An insulation receiver portion is disposed near the open end of the bore. A wire having a conductive core covered in insulation is included. The core is disposed within the core receiver portion, and the insulation is disposed within the insulation receiver portion. A primary crimp region is disposed radially coincident to the core receiver portion and is impressed with one or more crimp distortions. A secondary crimp region radially coincident with the insulation receiver portion is impressed with one or more crimp distortions. 
     In another embodiment of the invention, a method producing an environmentally sealed electrical contact assembly is provided. The method uses a contact including a contact body having a mating portion and a barrel portion configured for receiving an end of an electrical conductor. The barrel portion includes a wall defining a bore having a closed end and open end. The bore includes a core receiver portion for receiving the core of an electrical conductor and a plug receiver portion adjacent the closed end of the bore. A hole is formed in the barrel portion proximate the closed end of the bore and extends into the plug receiver portion of the bore through the wall. An insulation receiver portion is disposed near the open end of the bore. A primary crimp region is disposed radially coincident to the core receiver portion and is configured to receive one or more crimp distortions. A secondary crimp region is radially coincident with the insulation receiver portion and is configured to receive one or more crimp distortions. The method includes inserting a plug having a body portion into the open end of the bore. The method also includes pressing the plug into an end of the plug receiving portion to seal the plug receiving portion of the bore and the hole from the rest of the bore. The method further includes inserting the core of a wire into the core receiver portion and inserting an insulation of the wire into the insulation receiver portion. The method lastly includes impressing one or more crimp distortions into a primary crimp region disposed radially coincident to the core receiver portion, and impressing one or more crimp distortions into a secondary crimp region radially coincident with the insulation receiver portion to establish an environmental seal between the bore and the insulation. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with a general description of the invention given above, and the detailed description given below, serve to explain the invention. 
         FIG. 1  is a partially dissembled cross-sectional view in partial longitudinal cross section of an embodiment of the invention. 
         FIG. 2  is a detailed cross-sectional side view of a portion of  FIG. 1   
         FIG. 3  is a perspective view of a component of an embodiment of the invention. 
         FIG. 4  is a partial side cut-away view of an assembly of an embodiment of the invention having a male pin. 
         FIG. 5  is a partial side cut-away view of an assembly of an embodiment of the invention having a female socket. 
         FIG. 6  is a table of test data corresponding to an embodiment of the invention. 
         FIG. 7  is a table of test data corresponding to an embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     A partially dissembled cross sectional perspective view one embodiment of an environmentally sealed contact  10  is shown in  FIG. 1 . The contact  10  has a body  11  that includes a mating portion  12  and a barrel portion  14  that are generally aligned along a common axis  61  between a distal end  16  and a proximal end  18  and are separated by a shoulder  20 . The contact  10  may be fabricated from a suitable metal such as brass, copper, aluminum, silver, gold, or some other suitable electrically conductive composition. In one embodiment, the contact  10  is gold plated over a nickel underplate. The mating portion  12  may be a pin, socket, plug, receptacle, spade, eyelet, or the like. In the embodiment illustrated in  FIG. 1 , the mating portion  12  is in the form of a male pin. Alternatively, in  FIG. 5 , a female socket  12   a  is shown. The barrel portion  14  is tubular and has an outer wall  22  and an inner wall  24 . The inner wall  24  forms a bore  26  having a plurality of portions. Starting at the distal end  16  and working toward the proximal end  18 , an insulation receiver portion  28 , a core receiver portion  30 , and a plug receiver portion  32  are linearly and coaxially disposed to form a bore  26 . 
     A bleeder hole  34  is bored radially through the outer wall  22  and through the inner wall  24  of the barrel portion  14  and into the bore  26 . The bleeder hole terminates near or within the plug receiver portion  32 . When the contact  10  is submerged in various plating solutions during manufacture (e.g., cleaning fluids, nickel plating solution, gold plating solution, etc.) the hole  34  serves to facilitate full contact of those fluids with the inner wall  24  of the bore  26 . In the absence of a hole  34 , air trapped within the bore  26  prevents full introduction of fluids, and also frustrates draining of any solution. The bleeder hole  34 , however, also provides an undesirable path for environmental contaminants to enter the contact  10  and propagate to the core  36  (and through capillary action, beneath insulation  38 ) of the wire  40 . The core  36  of wire  40  is shown de-coupled from the connector  10  in  FIG. 1 . 
     In accordance with one embodiment of the invention to seal the contact, and specifically to seal the core receiver portion  30  and insulation receiver portion of the bore  26  from exposure to the environment through bleeder hole  34 , plug  42  is used in combination with contact body  11 . The plug  42  is dimensional and is configured to seal the plug receiver portion  32  and hole  34  from the receiving portion of the bore  26  and prevent the introduction of contaminants into the contact  10 . In one embodiment, the plug  42  is fabricated from copper or brass alloy and plated with gold over a nickel underplate. In another embodiment, the plug  42  might be fabricated from a resilient material such as EPDM rubber or silicone. 
     Turning attention to  FIG. 2 , a detail view of the interface between the plug  42  and cooperating plug receiver portion  32  of bore  26  is shown. The plug  42  includes a covered portion  50 , a cylindrical body portion  52 , a shoulder portion  54  having a chamfer surface  56 . A depression  58  is formed in the end of the plug at the shoulder portion  54 . The covered portion  50 , establishes a generally frustoconical tip for the plug that is configured to guide the plug  42  down the bore  26 , and into the plug receiver portion  32  during assembly. An installation press (not shown) having a reciprocating arbor or the like, is used to press fit the plug  42  into its resting position in the plug receiver portion  32  by applying an axial force to the depression  58 . The shoulder portion  54  halts the travel of the plug  42  during insertion into the plug receiver portion  32 . The shape of the depression  58  is selected to cooperate with the shape of any installation press equipment and may be hemispherical or angular. In one embodiment of the invention, as illustrated in the Figures, the depression  58  is configured as a conical depression centered in the plug as shown. 
     When the contact  10  is assembled as shown by the detail view of  FIG. 2 , either the cylindrical body portion  52 , the shoulder portion  54 , or both, may be dimensioned to provide an interference fit with the corresponding plug receiver portion  32  and core receiver portion  30  of the bore  26 , respectively. It should be noted that the cylindrical body portion  52  need not be dimensional and configured to completely obscure the hole  34  in order to achieve an effective environmental seal. The bleeder hole  34  and bore portion  32  are sealed from the remaining portions of the bore  26  and the exposed core  36  of the wire. For example, if the body  52  only partially seals or obscures the hole  34 , contaminants will nonetheless be halted from proximal propagation through the contact  10  as long as the body portion  52  is appropriately dimensioned to establish a press fit with the cooperating plug receiver portion  32 . Additional sealing action is achieved between the interface of the chamfer surface  56  of the plug  42  and a transitional chamfer surface  60  disposed at the transition from the plug receiver portion  32  to the core receiver portion  30 . In one embodiment, the chamfer surface  56  and the chamfer surface  60  are fabricated with an angle of approximately fifty degrees from a center axis  61  of the bore. 
       FIG. 3  shows a perspective view of the plug  42 . In this view, the depression  58  and the general profile of the plug  42  are more clearly seen. 
       FIG. 4  illustrates an environmentally sealed assembly  68  in accordance with on embodiment of the invention including the contact  10  and mated wire  40 . Here the core  36  of the wire  40  is generally fully seated within the core receiver portion  30  of the bore  26 . Additionally, the insulation  38  of the wire  40  is generally fully seated within the insulation receiver portion  28  of the bore  26 . A plurality of crimp distortions  70  are impressed into the outer wall  22  of the barrel portion  14  in a conventional fashion. In a primary crimp region  72 , the core receiver  30  of the bore  26  is crimped into physical and electrical contact with the core  36  to mechanically establish an electrical connection. The crimp distortions  70  in the primary crimp region  72  also serve to resist withdrawal of the wire  40  from the contact  10  when placed under axial tensile loads. In one embodiment, the crimp distortions  70  in the primary crimp region may be comprised of a plurality of radially applied indentations. Likewise, in a secondary crimp region  74 , the insulation receiver portion  28  of the bore  26  is crimped into contact with the insulation  38  of the wire  40 . In one embodiment a hexagonal crimp is used to reform the insulation receiver portion of the contact body  11 . Other crimp geometries which yield a contaminant-tight interface between the insulation  38  and insulation receiver portion  28  may produce acceptable results. It should be noted that the interference fit between various surfaces of the plug  42  and bore  26  establish environmental sealing toward the distal end  16  of the bore  26 , while the secondary crimp region  74  establishes environmental sealing at the proximal end  18  of the bore  26 . The primary crimp region  72  is positioned behind the plug receiver portion  32  of the bore and the plug receiver portion does not receive any crimp distortions  70  so as not to disturb the seal provided by the plug. 
     When the contact  10  is mated and crimped to the wire  40 , the integrity of the environmental seal may be verified by non destructive testing. The assembly  68 , having been adequately crimped, is submerged in water. Air is injected into the core  36  of the wire  40  at a point proximal to the contact  10 . An absence of bubbles exiting the contact  10  into the water provided qualitative evidence of an effective environmental seal. To provide a quantitative evaluation of environmental sealing, any air escaping the assembly  68  is captured and measured. For example, in one test regime, a 22 gauge assembly  68  is tested as explained above with an applied pressure of 14.5 PSI (1 bar) for one hour. A compliant assembly will, under this particular test regime, receive a passing score if less than 12 cm 3 /hour of air escapes the contact  10 .  FIGS. 6 and 7  illustrate test results for wires terminated with the contact of the invention. It has been observed that certain embodiments of the invention yield zero cm 3 /hour at 1 bar, and therefore greatly exceed the minimum passing criterion. The same zero leakage performance has been observed after the assembly  68  had been subjected to 500 thermal shock cycles. Additionally, contact resistance and tensile strength of the assembly  68  can be tested using conventional means known to one of ordinary skill in the art show desirable results. The elements of the disclosed invention yield contact resistance and tensile strengths that are substantially identical to comparable non-environmentally sealed contacts. 
     While the present invention has been illustrated by the description of one or more embodiments thereof, and while the embodiments have been described in considerable detail, they are not intended to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. The invention in its broader aspects is therefore not limited to the specific details, representative apparatus and method and illustrative examples shown and described. Accordingly, departures may be made from such details without departing from the scope of the general inventive concept.