Abstract:
A jumper cable plug for electrically connecting and physically engaging with a socket of the type used in the trucking industry is provided. The plug comprises a hollow cylindrical housing having a front end, a rear end, and a key extending from the front end toward the rear end. An annular grove is provided around the perimeter of the cylindrical housing, and a resilient seal is disposed in the annular grove.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to jumper cable plugs of the type used to electrically connect a jumper cable between a trailer and tractor, truck, or another trailer to establish an electrical connection between the two, and more particularly to a jumper cable plug with a moisture resistant seal. 
     BACKGROUND 
     Some heavy duty trucks assemblies include, in combination, a tractor and one or more trailers joined in series to the rear portion of the tractor. The trailer usually is equipped with various electrical systems, such as brake lights, turning signal lights, and anti-lock braking systems. These electrical systems in the trailer are typically powered by the electrical system of the tractor. To establish an electrical connection between the tractor and the trailer, an electrical cable is connected between the rear wall of the tractor and the front wall of the trailer. Similar connections can also be made between trailers if the truck assembly includes more than one trailer. 
     Each of the electrical cables typically has a suitable plug configured to connect to a cooperating socket. The socket is generally mounted on the rear wall of a tractor cab or the front wall of a trailer. The socket usually has a plurality of male pins that mate with a plurality of female terminals in the plug. The male pins are typically soldered, welded or mechanically connected to the metallic ends of the wires in a sheathed cable. Likewise, the female terminals are soldered, welded, or mechanically connected to the metallic ends of another sheathed cable. 
     The basic structures of a jumper cable plug and its cooperating socket are the subject of SAE (Society of Automotive Engineers) standards, specifically SAE standard J560. The SAE standard J560 provides the minimum requirements for primary and auxiliary 7-pin jumper cable plugs and sockets (or, receptacle) for the tractor-trailer and converter dolly jumper cable systems. The standard also includes the test procedures, design and performance requirements. Standardizing the geometries of the socket and plug ensures that any trailer can be electrically connected to any tractor using any cable connection. 
     While the SAE standard J560 is popular in the U.S., the ISO (International Standardization Organization) has similar standards. For example, the ISO standard 1185 was developed in Europe for transferring electrical signals from a towing vehicle to a trailer through a 7-pin electrical connector. Other relevant ISO standards include, ISO standards 7638 and 12098. The SAE standard J560 and the ISO standards 1185, 7638, and 12098 are incorporated herein by reference. 
     The SAE and ISO standards only specify the minimum requirements for the connectors governed by their standards. In other words, particular connectors can differ from one another in features outside the SAE or ISO specifications. 
     Neither the SAE or ISO standards require that the plug and socket form a water-tight seal when connected. As a result, it has been found that the metallic connections in the plug and the socket remain exposed to moisture in the environment even when the plug and the socket are mated. Moisture enters into the socket cavity over time through the space between the mating plug and socket. If the moisture migrates to the mated male pins and female terminals, the moisture will cause the mated electrical terminals of the socket and plug to corrode, which overtime may degrade the electrical connection, or if severe enough, even cause a fault in one or more of the circuits of which the connection terminals are components. If the moisture that finds its way into the terminals of the mated plug and socket contain salt, such as the MgCl and/or NaCl salts used to de-ice roads during the winter season, the corrosion process is typically accelerated due to the presence of chloride ions. 
     Accordingly, there is a need for an improved jumper cable plug of the type used to electrically connect a jumper cable between a trailer and tractor, truck, or another trailer to establish an electrical connection between the two. More particularly, there is a need for an improved jumper cable plug with a moisture resistant seal that when mated to a cooperating socket provides improved moisture resistance to the electrical terminals of the plug and socket. 
     SUMMARY OF THE INVENTION 
     A jumper cable plug for electrically connecting and physically engaging with a socket cavity of a socket of the type used in the trucking industry is provided. As an example, the plug comprises a hollow cylindrical housing having a front end, a rear end, and a key extending from the front end toward the rear end. An annular grove is provided around the perimeter of the cylindrical housing, and a resilient seal is disposed in the annular grove. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an exemplary electrical connector having a socket and a jumper cable plug shown an unmated position. 
         FIG. 2  is a side elevational view of the electrical connector of  FIG. 1  showing the plug and socket in the mated position. 
         FIG. 3  is a cross-sectional view of the electrical connector of  FIG. 2  taken along line  3 - 3 . 
         FIG. 4  is a cross-sectional view of the electrical connector of  FIG. 2  taken along line  4 - 4 . 
         FIG. 5  is a perspective view of the jumper cable plug shown in  FIG. 1 . 
         FIG. 6  is a side elevational view of the plug of  FIG. 5 . 
         FIG. 7  is a perspective view of one embodiment of a plug housing of the jumper cable plug of  FIG. 5 . 
         FIG. 8  is a perspective view of another embodiment of a plug housing. 
         FIG. 9  is a perspective view of one embodiment of a seal ring. 
         FIG. 10  is a plan view of the seal ring of  FIG. 9 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Embodiments will now be described with reference to the drawings. To facilitate the description, any reference numeral representing an element in one figure will represent the same element in any other figure. Further, in the following description, references to the front of a component shall generally mean the portion of the component that is closest to the mating end of the described plug or socket of which it forms a part. Similarly, references to the rear of a component shall generally mean the portion of the component that is away from the mating end of the described plug or socket of which it forms a part. 
     Exemplary jumper cable plugs are described in connection with  FIGS. 1-10  below. The exemplary jumper cable plugs incorporate a number of distinct aspects. While these distinct aspects have all been incorporated into the jumper cable plugs described herein in various combinations, the scope of the present invention is not restricted to the jumper cable plugs described herein. Rather, the present invention is directed to each of the inventive features of the jumper cable plugs described below both individually as well as in various combinations. The present invention is also directed to the inventive features of the electrical connector, both individually as well as in various combination, described below. 
       FIG. 1  is a perspective view of an exemplary electrical connector  10  having a socket (or, receptacle)  12  and a jumper cable plug  14 , which are shown in an unmated condition. The socket  12  and plug  14  of electrical connector  14  meet SAE standard J560. In other embodiments, the socket  12  and plug  14 , may, for example, meet ISO standard 1185, 7638, or 12098, or other applicable standards. 
       FIG. 2  is a plan view of the electrical connector  10  of  FIG. 1  showing the socket  12  and plug  14  in a mated condition. Referring to both  FIGS. 1 and 2 , the socket  12  includes a cylindrical barrel  16  defining a generally cylindrical cavity  20  for receiving a mating plug  14 . Cavity  20  is open at one end, the front end, and closed by end wall  18  at the rear end of barrel  16 . The interior surface  30  of wall  22  defines a cavity  20  that includes a keyway  26  sized to receive a key  28  on the plug  14 . Keyway  26  and key  28  cooperate to properly orient the plug  14  relative to the socket  12  when the plug  14  and the socket  12  are mated. 
     Specific reference is now made to  FIGS. 3 and 4 , where  FIG. 3  is a cross-sectional view of the electrical connector  10  of  FIG. 2  taken along line  3 - 3  and  FIG. 4  is a cross-sectional view of the electrical connector  10  of  FIG. 2  taken along line  4 - 4 . End wall  18  has an interior surface  32  that defines the rear end of cavity  20 . Interior surface  32  is generally flat and cylindrical in shape. The end wall  32  has a plurality of metal male pins  36  extending therethrough. In the present embodiment, the socket  12  is made from injection molded plastic and the pins  36  are co-molded in the socket. In other words, the end wall  18  of socket  12  is directly injection molded around pins  36 . Co-molding pins  36  into the end wall  18  in this manner helps ensure that moisture cannot enter into the socket cavity  20  through the rear of the socket  12 . It also ensures a strong mechanical bond between pins  36  and end wall  18 , thereby improving the durability of the socket  12 . 
     The male pins  36  are double ended in that each includes a proximal end that extends into the cavity  20  for mating with the female terminals  38  of the plug  14  and a distal end that extends away from wall  18 . Socket  12  is a QCS® socket from Phillips Industries. As a result, the rear end of socket  12  is designed to plug into another socket (not shown) configured to mount together with socket  12  on the wall of a tractor or trailer and having female connectors configured to accept the distal end of male pins  36 . In this configuration, the socket  12  can be removed from the other socket by simply pulling it from the other socket. As a result, the socket  12  can be periodically replaced as use conditions demand without having to re-solder the wires from the sheathed cable to the distal end of male pins  36  to establish the necessary electrical connections between the conductors of the sheathed cable and the male pins  36 . 
     In other embodiments, the distal ends of male pins  36  may be configured to be directly connected in a conventional manner to the electrical wires carried in a sheathed cable by soldering or mechanical connection as is known in the art. 
     The interior surface  30  of the socket  12  is preferably provided with a plurality of ribs  42 . The ribs  42  are preferably elongated and extend in a direction corresponding to the longitudinal direction of the socket  12 . Ribs  42  are provided on the bottom of socket barrel  16  to facilitate drainage of moisture or water from the cavity  20 . Opposing ribs  42  are preferably provided on the top of barrel  42  to ensure that plug  14  remains properly spaced from interior surface  30  in all directions. In one embodiment, however, the plurality of ribs  42  are not evenly distributed around the interior surface  30  of wall  22 . In a further embodiment, the lower portion of the interior surface  30  of the socket  12  has more ribs  42  than the upper portion of the interior surface  30 . Yet in another embodiment, the plurality of ribs  42  are evenly spaced apart from each other on the interior surface  30  of the wall  22 . 
     The socket  12  preferably includes a flange  40  which extends outward from the socket barrel  16  at its forward end. Referring to  FIG. 2 , the flange  40  preferably lies in a plane that forms an angle  44  between the normal of the flange  40  and the longitudinal axis of the socket  12 . In other words, the plane of flange  40  and the longitudinal axis of the socket  12  are not perpendicular. With this configuration, when the socket  12  is mounted on a wall (not shown) of a tractor or a trailer with the flange  40  attached to the wall, the longitudinal axis of the socket  12  will slope slightly downward. The downward slope facilitates the drainage of water that may enter cavity  20  before the plug  14  is inserted into the cavity  20  for electrical connection, or when a conventional plug without seal  92  is mated with socket  12 . In one embodiment, the angle  44  between the normal of the plan of flange  40  and the longitudinal direction of the socket  12  is 5°. In other embodiments, other angles may be selected. 
     A pair of mounting holes  46  are preferably formed through the flange  40  on opposing sides of the socket barrel  16 . The mounting holes  46  can be used to facilitate the mounting of the socket  12  to the exterior wall of a tractor or a trailer. 
     The body of socket  12 , including its barrel  16 , end wall  18 , and mounting flange  40 , is preferably integrally formed from a hard material, for example, die cast metal, glass filled molded nylon, polyvinyl chloride material, or any other suitable materials. 
     The exterior wall (not shown) of a tractor or a trailer where the socket  12  is to be mounted is preferably provided with a pair of holes corresponding to the mounting holes  46 . In addition, the tractor or trailer wall is also preferably provided with a central hole sized to receive the barrel  16  of the socket  12 . 
     Optionally, a gasket (not shown) or other seating member having the same general shape as flange  40  may be used to mount with the socket  12  to the wall. The gasket or other seating member can be interposed between the wall of the tractor or trailer and the flange  40 . A pair of nuts and bolts can be used to mount the gasket or other seating member and the socket  12  to the wall of the tractor or trailer. 
     Socket  12  may be provided with a hinged lid  48  to cover the opening of socket cavity  20 . In the present embodiment, lid  48  is pivotally mounted between mounting bosses  50  provided on opposite sides of barrel  15  above cavity  20 . A biasing member  34  is provided to bias the hinged lid  48  to a closed position in which lid  48  closes the opening of cavity  20 . Thus, when plug  14  is not inserted in cavity  20  of socket  12 , lid  48  will automatically close in the absence of any other force holding the lid  48  open. In the present embodiment, biasing member  34  is a torsional coil spring. 
     While the plug  14  is being mated to socket  12 , the biasing member  34  biases the inside surface of the lid  48  towards the upper surface of the plug  14  locking tab  52  comes into contact with the top of plug  14 . More specifically, in the absence of being held open by an operator, as plug  14  is inserted into cavity  20  of socket  12 , the locking tab  52  will ride on the top surface of key  28 . Locking tab  52  is positioned on the inside surface of lid  48  so that when plug  14  is fully mated with socket  12 , locking tab  52  will act as a stop to prevent plug  14  from inadvertently becoming uncoupled from socket  12  during operation of, for example, a tractor-trailer combination. In particular, when the plug  14  is fully coupled to the socket  12 , locking tab  52  is disposed rearward of the distal end  68  of key  28 . As a result, locking tab  52  will stop plug  14  from uncoupling by blocking the distal end  68  of key  28  from moving more than a predetermined distance away from socket  12  in the absence of a user lifting lid  48  against the biasing force supplied by biasing member  34 . 
     Preferably the distal end  68  of key  28  includes a raised protuberance to provide a surface against which locking tab  52  may operably act. 
     Referring further to  FIGS. 5-6 , the plug  14  comprises a generally hollow plug housing  54  with openings at both the front and rear ends of the housing  14 , pull tabs  76  disposed on opposite sides of housing  54  adjacent the rear end of housing  14 , a terminal holder  64  disposed in the opening on the front end of plug housing  54 , and a cable guard  90  disposed in the opening on the rear end of the plug housing. 
     Plug housing  54  comprises a generally hollow cylindrical housing  54  having a front portion  56  and a rear portion  58  and defining an interior space  62 .  FIG. 7  is a perspective view of one embodiment of the plug housing  54  of  FIG. 5 . 
     In the present embodiment, the plug housing  54  and pull tabs  76  are preferably integrally molded from a tough nylon material or other suitable material. 
     The terminal holder  64  includes a main body  86  removeably disposed with the front portion  56  of plug housing  54  and a circular end wall  72  disposed adjacent the forward end of the plug housing  54 . The terminal holder  64  is preferably injection molded from a plastic material such as nylon. The terminal holder  64  is preferably shaped to generally close the opening at the front end of the plug housing  54 . The end wall  72  preferably has a diameter that is about the same as the exterior diameter of the cylindrical plug housing  54  while the main body  86  of the terminal holder  64  is preferably has a diameter that is about the same as (or slightly smaller than) the interior diameter of the plug housing  54 . Therefore, the main body  86  of the terminal holder  64  can be properly inserted into the interior space  62  of the plug housing  54  while the end wall  72  will abut the front end of the housing  54 . 
     A screw  88  (shown in  FIG. 6 ) can be used to fix the terminal holder  64  in a stable position within the front portion  56  of housing  54 . To facilitate the use of screw  88  to attach terminal holder  64  to housing  54 , a hole for receiving screw  88  through the wall of the plug housing  54  may be molded directly in the wall of the front portion  56  of the plug housing  54 . Alternatively, the hole may be drilled after the housing  54  is formed. 
     The terminal holder  64  preferably includes a plurality of elongated channels  70  that extend through the terminal holder  64 . Channels  70  are formed in a pattern matching the pin pattern of male pins  36  in the corresponding sockets, such as socket  12 , to which plug  14  is designed to mate. Each channel  70  is sized to receive a metallic female terminal  38  therein from the rear end of terminal holder  64 . Preferably the forward ends of the channels include an area for receiving a spring tab of a female terminal  38  as is known in the art. In this way, a terminal  38  can be inserted from the rear of terminal holder  64 , but once fully inserted, it will be blocked from leaving channel  70 . 
     Further, as best seen in  FIGS. 3 and 5 , each channel  70  includes a stop  87  provided in the end wall  72  portion of the channel  70 . Stops  87  are provided to prevent the terminals  38  from being pulled through the front side of terminal holder  64  when plug  14  is uncoupled from socket  12 , or other corresponding socket, in the conventional manner or as a result of an inadvertent “drive off” Given that plug  14  is repeatedly coupled and uncoupled throughout its life, the stress relief function provided by stops  87  help to extend the life expectancy of plug  14  and/or the frequency of maintenance required related to the female terminals  38 . 
     Female terminals  38  are attached to the conductors in coated wires  73  of cable  74  in a conventional manner, such as by mechanically crimping female terminals  38  to the ends of the wire conductors in the coated wires  73 . After terminals  38  are attached to the ends of coated wires  73 , each terminal  73  is inserted into its corresponding channel in terminal holder  64  based on the color of the wire  73  attached to the terminal  38  as is conventional in the art. As described above, upon insertion of terminals  38  into their corresponding channel  70 , a tab on terminals  38  prevents the terminal from being withdrawn from the channel as is conventional in the art. 
     In one embodiment, the cable guard  90  is used to provide stress relief to the ends of the coated wires  73  that are mated with terminals  38  and thereby prevent accidental cable pull-out of cable  40  from the rear end of plug  14 . 
     In the illustrated embodiment, cable guard  90  includes a cylindrical hole  100  extending longitudinally therethrough. Cable  74  extends through the cylindrical hole  100  of cable guard  90 . The exterior surface of the cable guard  90  is longitudinally castellated with ridges  102  and recesses  104  for improved gripping. The internal surface of rear end  106  of plug housing  54  is threaded. Mating threads are provided on the external surface of the forward end of cable guard  90 . Thus, cable guard  90  may be removably threaded into the rear end of plug housing  54 . 
     A rubber grommet  110  is positioned about the forward end of the sheathed portion of cable  74 . Cable clamp  109  is provided about rubber grommet  110 . Cable clamp  109  includes a plurality of tapered clamping fingers  112  extending rearwards from an annular ring portion  114  at the forward end of the cable clamp  109 . The distal ends of clamping members  112  include a gripping edge  120  that extends radially inward toward cable  74  in a direction that is generally transverse to the longitudinal axis of the cable  74 . As explained more fully below, gripping edges  120  dig into the sheath of cable  74 , thereby preventing cable  74  from being accidentally pulled out of the rear of plug  14 . 
     The annular ring portion  114  of the cable clamp  109  abuts a stop  118  which extends radially inward from the wall of plug housing  54 . As a result, when cable guard  90  is screwed into plug housing  54 , the tapered clamping fingers  112  become interposed between beveled surface  116  at the forward end of cable guard  90  and cable  74 . Further, as cable guard  90  is threaded into plug housing  54 , the annular ring portion  114  of cable clamp  109  is prevented from moving forward in plug housing  54  beyond stop  118 . Thus, as cable guard  90  is continued to be screwed into the rear end of cable housing  54 , the cable guard  90  will translate in a forward direction toward stop  118 . As a result, the beveled surface  116  will press the tapered clamping fingers  112  radially inward toward the sheath of cable  74  and their respective gripping edges  120  will bite into the surface of the cable  74  to prevent the cable  74  from moving rearward. 
     The longitudinal key  28  formed on the front portion  56  of plug housing  54  preferably extends from the front end  66  toward the rear portion  58  of the plug housing  54 . The key  28  preferably has a distal end  68  that is disposed outside of cavity  20  of socket  12  when plug  14  is fully mated with socket  12 . The distal end  68  preferably comprises a protuberance that has a larger cross-sectional thickness than the rest part of the key  28 . As noted above, distal end  68  is configured to cooperate with a locking tab  52  of a mating socket  20  to prevent accidental pull-out of plug  14  during operation. 
     The key  28  cooperates with the keyway  26  formed in the sleeve  18  of the socket  12  to assure that the plug  14  and the socket  12  have the correct angular relation to each other when they are mated together. The key  28  is preferably integrally formed with the plug housing  54 . 
     In the present embodiment, rear portion  58  of the plug housing  54  includes a pair of pull tabs  76  that extend outwardly from opposing sides of the plug housing  54  to facilitate removal of the plug  14  from socket  12 . 
     Referring to  FIG. 7 , the front portion  56  of plug housing  54  preferably has an annular groove  78  that surrounds the plug housing  54 . The annular groove  78  should be located so that when plug  14  is mated with a corresponding socket, such as socket  12 , the groove  78  will be fully received within the socket cavity. The annular groove  78  is preferably formed in plug housing  54  rearward of screw  88 . In other words, the screw  88  is preferably interposed between the front end  66  of the plug housing  56  and the annular groove  78 . In one embodiment, the annular groove  78  is located in approximately the middle of the key  28 . In other embodiments, the annular groove  78  may be formed in other locations. 
     As best seen from  FIG. 7 , annular groove  78  extends around the entire circumference of plug housing  54 , and includes a portion  80  formed on the key  28 . In other words, annular groove  78  preferably tracks the outer profile of the plug housing  54 . 
     The annular groove  78  preferably has a width in the range of approximately 0.2 inches to 0.25 inches. However, other dimensions for the annular groove  78  may also be employed. 
     The annular groove  78  is preferably molded into the housing  54 . However, in some embodiments, it may be desirable to machine annular groove  78  into the plug housing  54 . 
     Referring to  FIG. 1 , the plug  14  comprises a resilient seal ring  92  disposed about plug housing  54  in the annular groove  78 . The resilient seal ring  92  preferably has a width corresponding to that groove  78  so that it may be received therein. Accordingly, the resilient seal ring  92  preferably has a contour that corresponds to the cross-sectional profile of the annular groove  78  around the plug housing  54  so that the seal ring  92  can be tightly fitted around plug housing  54  within annular groove  78 . 
     Referring to  FIGS. 9-10 , the resilient seal ring  92  includes a base portion  93 , which seats in the annular groove  78  and a plurality of flexible ribs  94  integrally formed therewith. The flexible ribs  94  extend radially outward from the base  93  about its circumference. In one embodiment, three flexible ribs  94  are provided. In other embodiments, other forms of seal rings may be employed. 
     The seal ring  92  is preferably made from a rubber material. In one embodiment, the rubber material is EPDM rubber. In another embodiment, the rubber material is silicone rubber. Other resilient materials can also be used to make the resilient seal ring  92 . 
     Although not required, a plurality of relief cuts  96  may be formed in the ribs  94 . Relief cuts  96  are positioned and sized to align with and receive ribs  42  when plug  14  and socket  12  are mated. 
     As noted above, the annular groove  78  is located so that when plug  14  is mated with a corresponding socket, such as socket  12 , the groove  78  will be fully received within the socket cavity. As a result, as shown in  FIGS. 2-4 , when plug  14  is fully engaged with socket  12 , resilient seal ring  92  will be positioned within the cavity  20  so that it is interposed between plug housing  14  and the interior surface  30  of wall  22 . 
     When the plug  14  is engaged with the socket  12  by inserting it into the cavity  20  of the socket  12 , a sealed internal volume  98 , which is closed by the resilient seal ring  92  is formed. Because the seal ring  92  (including ribs  94 ) is made of a generally resilient material, the seal ring  92  conforms to the profile of the interior surface  30  of wall  22  to form a water-resistant, if not a water-tight seal. Moreover, because the annular groove  78  is preferably formed rearward of screw  88 , the sealed internal volume  98  also includes the area where the screw  88  is inserted through plug housing  54 . Therefore, the female terminals  38  of plug  14  and the male pins  36  of the mating socket, such as socket  12 , will be protected from moisture in the environment, and thus the potential for corrosion that the presence of moisture can cause, when the plug is mating with a cooperating socket. 
     When the plug  14  is inserted into the cavity  20  of the socket  12 , or another mating socket, the ribs  94  of the resilient seal ring  92  will be tilted rearward toward the rear portion  58  of housing  54  due to the frictional force between the ribs  94  and the interior surface  30  of the socket  12 . As a result, it will be easier for any residual moisture that may be within the sealed internal volume  98  to exit than for moisture from the environment to get in. In addition, when the plug  14  is pushed into the cavity  20 , the air pressure within the sealed internal volume  98  will be higher than the air pressure outside the sealed internal volume  98 . This will also help prevent moisture from the atmosphere from getting into the sealed internal volume  98 . 
     As those skilled in the art will appreciate, plug  94  will need to be able to mate with any type of socket meeting the same standard against which plug  14  is constructed, including sockets made by a host of different manufacturers. The jumper cable plugs  14  of the present patent document are capable of forming a water-resistant, if not a water-tight seal with any such corresponding socket. Because the seal ring  92  (including the ribs  94 ) is made out of a generally resilient material, seal ring  92  will conform to the interior surface  30  of wall  22  of a socket  12  thereby forming a water-resistant, if not a water tight seal in a variety of plug  14  and socket  12  combinations, including, for example: (1) the resilient seal ring  92  of plug  14  includes relief cuts  96  in ribs  94  and the socket  12  has corresponding ribs  42  provided on interior surface  30  of wall  22 ; (2) the resilient seal ring  92  of plug  14  has relief cuts  96  in ribs  94 , but the socket  12  does not have any corresponding ribs  42  on interior surface  30  of wall  22 ; (3) the resilient seal ring  92  of plug  14  does not include any relief cuts  96  in ribs  94 , but the socket  12  has ribs  42  formed on the interior surface  30  of wall  22 ; and (4) the resilient seal ring  92  of plug  14  does not include any relief cuts  96  in ribs  94  and the socket  12  does not have any ribs  42  on interior surface  30  of wall  22 . 
     Referring to  FIGS. 9 and 10 , in one embodiment, the resilient seal ring  92  is preferably formed separate from the plug housing  54  and then placed over the plug housing in the annular groove  78 . To mitigate the likelihood that seal  92  will be displaced during repeated coupling and uncoupling operations, seal  92  is preferably bonded within annular groove  78  of plug housing  54  using a suitable adhesive. 
     Instead of being adhesively bonded to plug housing  54 , seal ring  92  may be over-molded onto the annular groove portion of the plug housing. Alternatively, if a material with a sufficient glass transition temperature is used, the seal ring  98  may be co-molded with the plug housing so that the plug housing is injection molded around the seal ring. In this way, the seal ring may provided with features which improve the mechanical bonding between the seal ring  98  and plug housing  54   
       FIG. 8  is a perspective view of another embodiment of the plug housing  54  for use in plug  14 . In this embodiment, a protuberances  82  is formed at approximately the middle of the portion  80  of annular groove  78  formed on key  28 . The protuberance  82  is used to position and help retain seal  92  within annular groove  78 . Accordingly, in this embodiment, seal ring  92  would include a corresponding recess for receiving protuberance  82 . 
     Although in the illustrated embodiment, protuberance  82  is located on portion  82  of annular groove  78 , in other embodiments, protuberance  82  may be located in other positions around the perimeter of annular groove  78 . Further, more than one protuberance  82  and corresponding recesses in seal  92  may be employed. 
     While embodiments of the invention presented above have been shown and described as comprising a plug with female terminals so that the mating socket has male pins, it is within the scope of the invention for the electrical terminals to be reversed so that the plug has male pins and the mating socket has female terminals. If the plug  14  is constructed to comply with a particular SAE or ISO standard, then the plug  14  will mate with any socket that has also been constructed according to the standard. Thus, the plug  14  of the present patent document will provided water-resistant, if not water-tight seals when coupled to sockets within an existing fleet of trucks or trailers. 
     Although the invention has been described with reference to preferred embodiments and specific examples, those of ordinary skill in the art will readily appreciate that many modifications and adaptations of the invention are possible without departure from the spirit and scope of the invention as claimed hereinafter.