Patent Publication Number: US-6666698-B2

Title: Arc limiting electrical connector assembly

Description:
This application claims benefit of provisional 60/225,905 filed Aug. 17, 2000. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to the suppression or prevention of arcing between electrical connectors as the connectors are mated and unmated so as to minimize potential damage to mating contacts due to arcing. This invention also relates to mating electrical connectors which are mechanically unstable in an arc susceptible position so that spring or biasing forces are generated that will tend to physically move the mating connectors away from a partially mated, arc susceptible position. This invention is also related to the generation of inertial forces due to the deformation of connectors housing members during mating in such a way that the inertial forces will tend to move the connectors away from a partially mated, arc susceptible position. 
     2. Description of the Prior Art 
     Currently there appears to be no inexpensive and reliable technology to prevent arcing at relatively low voltages of approximately 50 volts or less in electrical connectors. A 42-volt electrical architecture will soon be adopted for automotive electrical systems, and arcing is a problem that must be addressed. Any solution to this problem should be fully automatic and allow safe hot mate and unmate without damage to an operator or appreciable damage to the connector or the connector terminals. 
     U.S. Pat. No. 6,217,356 discloses one approach to prevent damage to mating terminals due to arcing. A secondary contact surface is provided at the tip of a terminal that mates with a pin terminal. Arcing damage is limited to the secondary contact surface and the portion of the pin that first comes close to the secondary or sacrificial contact surface. The main contact regions on both mating terminals are spaced from the sacrificial areas. This type of solution adds length and size to the terminals and to the electrical connectors in which they would be used. Therefore it has disadvantages when applied to an application in which a large number of terminals are positioned in a single connector and in which space and mating force are serious considerations. 
     If electrical connectors are properly mated and not mated and unmated under load, arcing is not a problem. A great deal of effort has been expended to provide to insure that automotive electrical connectors are properly mated. Mechanical assist devices, such as levers, are commonly employed. Guide plates eliminate stubbing during mating to prevent damage to the terminals. Guide plates also protect an operator from shocks. Connector position assurance devices that can only be manually actuated if the connectors are fully mated are also employed to insure that electrical connectors have been fully mated. 
     Another approach that has been employed is the use of inertial locks which will either snap connectors into a fully mated configuration or will force the connectors apart. U.S. Pat. No. 4,010,998 discloses the use of an inertia lock in which, once a sufficient mating force has been applied, mating cannot be stopped until the connectors are locked and the connector terminals are fully engaged. If an insufficient manual force is applied, the inertia lock will cause the connectors to “self reject”. The inertial lock mechanism shown in U.S. Pat. No. 4,010,998 includes a latch arm on one connector that is deflected outward over a triangular locking ramp. The maximum mating force of the inertial lock mechanism is greater than the overall engagement force of the terminals so that the mating force tending to latch the connectors in place will be greater than the terminal engagement force. In other words, the maximum connector mating force exceeds the overall terminal engagement force. In many applications, such as automotive connector assemblies, the mating force is already too great and mechanical assist means, such as levers or bolts must be employed. However, these inertial locks are not typically used in conjunction with mechanical assist levers and guide plates and they are not used to prevent the connectors from occupying an intermediate, partially mated configuration in which mating terminals are in close proximity and susceptible to arcing. 
     SUMMARY OF THE INVENTION 
     The introduction of 42 volt electrical systems in automobiles and motor vehicles causes some concern that electrical terminals may be subject to arcing as electrical connectors are mated or unmated under load. Arcing has not been a significant problem for standard 14 volt electrical systems, because 14 volts is below the minimum arc voltage for most contact materials. A stable arc typically cannot exist below 15 volts. However, the power demands of vehicles are increasing to a point where the current 14 volt system is no longer adequate. All current terminals will arc when mated and unmated under load at 42 volts. All contact metals can sustain a stable arc above 20 volts. It is hoped, however, that the new 42 volt electrical systems can employ electrical connectors and terminals that do not differ significantly from those used in standard 14 volt systems. Although electrical connectors are not typically mated and unmated under load, even infrequent occurrences can result in problems. Most automotive electrical connectors include connector position assurance devices that are supposed to insure that connectors are fully mated and not left in a partially mated configuration. However, they require manual operation and will only achieve their intended function if properly used. If connectors are left in a partially mated, arc susceptible configuration or if the connector work loose during transit, arcing could cause injury and/or damage for a 42 volt electrical system. 
     An electrical connector assembly comprising a receptacle connector and a mating plug connector shiftable toward each other through a mating travel distance to fully mate the receptacle connector to the plug connector. The receptacle connector includes a plurality of receptacle terminals mounted in a receptacle housing and the plug connector including a plurality of plug terminals mounted in a plug housing. When mating begins between the receptacle connector and the plug connector, a first inertial spring force opposing mating is generated before receptacle terminals and plug terminals reach an intermediate, partially mated position where arcing is possible between the receptacle terminals and plug terminals. Upon further movement toward a fully mated position of the receptacle connector and plug connector, a second spring force acting in a mating direction is generated. The first and second spring forces act to urge the receptacle connector and the plug connector away from an intermediate, partially mated position where arcing is possible between the receptacle terminals and the plug terminals. The first and second mating forces together act over only a portion of the mating travel distance of the receptacle. 
     In one embodiment, the receptacle connector has an inertial protrusion extending into the mating cavity from at least one interior surface of a receptacle housing wall. An inertial protrusion is located on an exterior surface of the plug connector housing, and the receptacle connector inertial protrusion and the plug connector inertial protrusion are mutually engagable during mating and unmating to force mating terminals away from an intermediate, partially mated position in which arcing between receptacle connector terminals and plug connector terminals can occur. These inertial protrusions will increase the mating and unmating velocities to minimize the arc times. If contacts are to be mated and unmated under load, the contact disconnect time must be short and the mating velocities high. 
     In another embodiment, an over-center lever is mounted on one connector housing. The lever engages the mating electrical connector to apply a force along a mating axis to mate and unmate the two electrical connectors. An additional spring force parallel to the mating axis is generated by actuation of the lever. The spring force urges the mating electrical connector toward either a pre-stage position or a fully mating position and away from an intermediate partially mated position in which arcing may occur between pin terminals in the electrical connector and mating terminals in a mating electrical connector. This additional spring force is generated by deformation of a cantilever beam about which the over-center lever pivots. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a three dimensional representation of a first embodiment of a connector assembly in which the two mating connectors are biased so that they do not remain in a partially mated position in which arcing can occur between unmated terminals. 
     FIG. 2 is a view of a receptacle connector housing of the type used in the assembly of FIG.  1 . 
     FIG. 3 is a view of a plug connector housing of the type used in the assembly of FIG.  1 . 
     FIG. 4 is a view of a pin protection plate that is mounted in the receptacle connector housing to guide terminals during mating. 
     FIG. 5 is a sectional view of the two connectors forming the connector assembly of FIG. 1 in which two corresponding terminals are shown in an arc susceptible position. 
     FIG. 6 is a sectional view in which the two connectors are in a position in which the two contacts are mated so that current can be carried by the two connectors without arcing. 
     FIG. 7 is a three dimensional view of an over-center lever connector assembly in a pre-stage position. 
     FIG. 8 is a side view, with internal structures diagrammatically shown, of the over-center lever connector assembly in the pre-stage position also shown in FIG.  7 . 
     FIG. 9 is a three dimensional view of an over-center lever connector assembly in which rotation of the lever has begun, but in which terminals in the two connectors would not be close enough for arc initiation. 
     FIG. 10 is a side view, with internal structures diagrammatically shown, of the over-center lever connector assembly in the position also shown in FIG.  9 . 
     FIG. 11 is a three dimensional view of an over-center connector assembly in which the connectors have moved to an intermediate, partially mated position in which arcing could be a problem. Deflection of the lever mounting arm to create a force tending to move the connectors away from this position is also shown. 
     FIG. 12 is a side view, with internal structures diagrammatically shown, of the over-center lever connector assembly in the intermediate, partially mated position also shown in FIG.  11 . 
     FIG. 13 is a three dimensionally view of the fully mated over-center connector assembly. 
     FIG. 14 is a side view, with internal structures diagrammatically shown, of the over-center lever connector assembly in the fully mated position also shown in FIG.  13 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The connector assembly  2 , which comprises the first embodiment of this invention, is the subject of FIGS. 1-6, in which components and the operation of the connector assembly are shown. Connector assembly  2  includes a receptacle connector  10  and a mating plug connector  50 . Pin terminals  44  are positioned within a molded receptacle connector housing  12 , and socket terminals  62 , matable with the pin terminals  44 , are mounted in a molded plug housing  52 . A mechanical assist lever  70  is pivotally mounted on the receptacle housing  12 , and engages the plug housing  52  to apply a force between the two connectors  10  and  50  to either mate or unmate the plug connector  50  from the receptacle connector  10 . Projections  24  are located on the receptacle connector housing  12  in opposition to projections  56  on the plug connector housing  12 . These projections  24  and  56  will cause deformation of at least portions of the receptacle connector housing during movement between a pre-stage position and a fully mated position. As will be subsequently described in greater detail, these projections  24  and  56  form inertial means that function to bias the two connectors  10  and  50  away from an intermediate, partially mated position in which corresponding matable terminals  44  and  62  are in close proximity and are susceptible to arcing if the connectors are mated or unmated in a hot or current carrying state. 
     The receptacle connector housing  12 , shown in FIG. 2 is a one-piece molded member. A mating cavity  14 , located on a mating end of housing  12  is formed by a housing shroud  16 , formed by four shroud walls  18 . Terminal cavities  15  extend through an interior wall forming the rear of the mating cavity  14 . As shown in FIGS. 5 and 6, male terminal pins or blades  44  extend through these terminal cavities  15  into the mating cavity  14 , where these male terminals can be received within the plug connector  50  to mate with female or socket terminals  62 . In the preferred embodiment of this invention, the male terminals  44  comprise right angle printed circuit board pins. The pin terminals  44  and the socket terminals  62  used in the preferred embodiment of this invention have a current rating of 25 amps. 
     The receptacle connector housing  12  also has two slots  22  extending from the mating face into side walls forming the housing shroud  16 . These slots  22  provide clearance for cylindrical pins  64  located on the exterior of the plug housing  52 , as shown in FIG.  3 . Two molded pins  20  extend from the sides of the housing  12  just to the rear of the root of the slots  22 . The molded pins  20  form the fulcrum of the lever  70 , when it is mounted on the receptacle housing  12 . 
     Three projections or bumps are located on the interior of the shroud wall  18 , and extend into the mating cavity. Inertial protrusion  24  is adjacent the front lip of the lower shroud wall  18 , as shown in FIG.  2 . As shown in FIGS. 5 and 6, an identical inertial protrusion  24  extends into the top of the mating cavity  14 . The inertial protrusions  24  have a front sloping surface  26  and a rear sloping surface  28 . In the preferred embodiment of this invention, the height of each protrusion  24  is equal to approximately 0.047 inch and the surfaces  26  and  28  are inclined at an angle of one hundred and five (105) degrees relative to the interior face of the corresponding shroud wall  18 . These inertial protrusions  24  will work with similar, but opposing, protrusions  56  on the plug housing  52  to prevent the receptacle connector  10  and the plug connector  50  from staying in an intermediate, partially mated, position in which the leading edges of a pin terminals  44  are in close proximity to the entrance of corresponding socket terminals  62 , where the terminals are susceptible to arcing in a 42 volt automotive electrical connector system. The manner in which these protrusions  24  and  56  act together during mating and unmating of the receptacle connector  10  and the plug connector  50  will be subsequently described in greater detail. 
     Two other molded projections  30  and  32  are also located on the interior of the shroud walls  18 . Each of these projections  30  and  32  engage a pin protection plate  34 , shown in FIG. 4, to retain the pin protection plate  34  in the mating cavity  14  and to shift the pin protection plate  34  into an extended position to protect the terminals  44  prior to mating the two connectors or when the plug connector  50  is withdrawn from the mating cavity  14  and to provide shock protection. The plate retention projection  30 , located below slot  22  on a side shroud wall  18 , prevents retraction of the pin protection plate  34  from the mating cavity  14 . Plate retention projections  30  are located on both shroud side walls  18 . The plate positioning projections  32  are located adjacent to the inertial protrusion  24 , and plate positioning projections  32  are located on both the top and bottom shroud walls  18 . The plate positioning projections  32  will engage pin plate transfer arms  40  to function as a stop limiting inward movement of the pin protection plate  34 . 
     The plug connector housing  52  is shown in FIG.  3 . The preferred embodiment of this plug housing  52  is molded as a single piece, and it includes two rows of side-by-side terminal cavities  54 , two individual cavities being shown in FIGS. 5 and 6. The entrance  55  to each of these cavities  54  is dimensioned to receive one of the pin terminals  44  during mating, and the socket terminals  62  are positioned within the terminal cavities  54 . Inertial protrusions  56  are located on the top and bottom faces of the plug housing  52 . As shown in FIG. 3, the inertial protrusion  56  on the top surface is located within channel  59  extending between a mating and a rear face of the housing  52 . The inertial protrusion  56  on the bottom surface is located in a similar channel. The inertial protrusion  56  has a sloping front surface  58  and a sloping rear surface  60 . These sloping surfaces  58  and  60  are inclined relative to the housing face from which they protrude at substantially the same angles formed by sloping surfaces  26  and  28  on the receptacle connector inertial protrusion  24 . When the plug protrusions  56  abut the receptacle protrusions  24 , the receptacle connector shroud housing walls  18  are outwardly deflected to permit the receptacle protrusions  24  to pass over the plug protrusions  56 . The protrusions are shaped so that receptacle connector  10  is in an unstable position relative to the plug connector  50  when the protrusions  24  ride over the protrusions  56 . The channel is dimensioned to receive the receptacle protrusion  24  in all of the remaining relative positions of the receptacle connector  10  and the plug connector  50 . The relative positions of protrusions  24  and  56  are thus chosen so that they will be in unstable engagement when the connectors  10  and  50  are in an intermediate, partially mated position in which mating terminals  44 ,  62  will be in close proximity, but not fully mated, where an arc can occur. The inertial protrusions  24  and  56  thus work to force the terminals  44 ,  62  away from this arc susceptible position, either toward a fully mated configuration or toward an unmated or pre-staged position. As opposed protrusions  24  and  56  slide along opposed sloping surfaces, the force applied between the two connectors will accelerate them away from the partially mated condition, arc susceptible position, and if an arc were to momentarily occur, the acceleration would help to rapidly mate the terminals and extinguish the arc. Although the inertial protrusions  24  and  56  will act to move the two connectors and the terminals away from the intermediate, partially mated position in which the terminals are susceptible to arcing in the presence of a potential difference, these protrusions  24  and  56  need not act over the entire distance which the connectors must travel from a pre-staged to a fully mated configuration. It is only necessary that these protrusions  24  and  56  act over a relatively short distance because the portion of the mating travel in which an arc is possible is much smaller than the entire mating travel of the connectors. 
     The inertial protrusions  24  and  56  function during mating to rapidly establish a high and stable contact normal force where and arc cannot occur. An arc will not occur unless there is some form of contact separation, which leads to a drop in normal force. When contacts are unmated without some form of arc suppression, it is desirable that the disconnect velocity be high and the inertial protrusions  24  and  56  act together to increase the disconnect velocity when the contacts are in an arc susceptible position. The protrusions  24  and  56  cause the mating connectors, when unmated, to move to a position in which there will be an air gap separating the contacts so there will be no or minimal tendency to arc through air. Although arcing is not as severe during mating as during unmating, it is nevertheless desirable that both high mating and unmating velocities be achieved, and the inertial protrusions  24  and  56  function to achieve high velocities in both directions. 
     The plug housing  52  also includes posts  64  extending from opposite sides. These posts or pins  64  will be received within a lever cam groove or cam profile  72  so that rotation of the lever  70  will move the pins  64  along the lever groove, thus forcing the plug connector  50  to move in either the mating or unmating direction relative to the receptacle connector  10 . Pins  64  are dimensioned to move within the slots  22  on the sides of the receptacle connector housing  12 . 
     Diamond shaped projections  66 , one of which is shown in FIG. 3, are located on the top and bottom of the plug housing  52 . These projections  66  engage the plate transfer arms  40  on pin plate  34  to retract the pin plate when the two connectors are unmated or are moved from a fully mated configuration to a pre-stage configuration. Plug housing  52  also includes recesses  68  that provide clearance for latch arms  38  located on the ends of the pin protections plate  34 . 
     The connector assembly  2 , also includes a mechanical assist lever  70  that can be used to apply forces to mate and unmate the receptacle connector  10  and the plug connector  50 . Lever  70  includes two arms  76  extending from opposite ends of a lever base  78 . Each lever arm  76  also includes a camming groove  72  facing inwardly. Pin openings  74  are located adjacent to the camming groove  72 , and openings  74  are dimensioned to receive the receptacle housing pins  20 , so that the lever will pivot about the pins  20 . The camming groove  72  is dimensioned so that the plug actuating pins  64  move along the camming groove  72 , as the lever  70  is rotated, thus imparting relative movement between the receptacle connector  10  and the plug connector  50 . 
     In order to first insert the plug connector  50  into the receptacle connector mating cavity  14 , the lever  70  is first rotated to an upright position in which the entrance to camming groove  72  is aligned with the slot  22  on the side of the receptacle housing  12 . In this position, the plug pins  64  can be inserted into both the groove  72  and the slot  22  so that the plug connector can be inserted part way into the mating cavity  14 . At this point the terminals  44  and  62  will be separated by a distance sufficient to prevent arcing between opposed, matable terminals. The plug connector  50  will, however, be at least partially restrained with the mating cavity  14 . The lever  70  can also be partially rotated in a counterclockwise direction, as shown in FIG. 5 to partially restrain the plug connector  50  in this initial position, which can be referred to as a pre-stage configuration. As shown in FIG. 5, the leading ends of terminals  44  and  62  are separated and the receptacle inertial protrusion  24  is in initial contact with the plug inertial protrusion  56 . The plug connector  50  cannot move from the position shown in FIG. 5 unless a force is applied along the mating axis, an axis parallel to the longitudinal direction of sockets  62 . The connectors can be shipped in this manner, or they can be positioned in this manner during assembly or servicing. Typically the sockets  62  would be crimped to wires before insertion into the plug terminal cavities  54 , but for the purpose of illustration, one socket terminal is shown in FIG.  5 . Details of the socket terminal retention mechanism are not shown in FIGS. 5 and 6, but the socket terminals  62  are held in the terminal cavities  54  by conventional means that are not critical for the functioning of this device. 
     FIG. 6 shows the relative positions of the plug connector  50  and the receptacle connector  10  after the lever has been rotated sufficiently to bring socket terminals  62  into engagement with pin terminals  44 . In the position shown in FIG. 6, the terminals  62  and  44  are in sufficient contact so that no arc will occur between the terminals, and all of the current will pass through the electrically conductive terminals themselves. In this minimum fully mated position, the contacts are in a position consistent with USCAR requirements for 2 mm of contact wipe past lead in geometry. If the connector is accidentally left in this position, there will be no adverse effects. In the preferred embodiment, the terminals  44  and  62  should be moved a sufficient distance to provide 2 mm. of wiping action along their mating surfaces. It should be noted that relative movement from the position shown in FIG. 5 to that shown in FIG. 6, has resulted in relative movement of the receptacle inertial protrusions  24  from a position on the inside of plug protrusions  56  to a position on the outside of the plug protrusions  56 . In order to move between these positions, the inertial protrusions  24 , and the walls  18  from which they extend, must deflect outwardly so that protrusions  24  can pass over protrusions  56 . It is while the inertial protrusions  24  are passing over the inertial protrusions  56 , between the positions shown in FIGS. 5 and 6, that the leading ends of terminals  44  and  62  will be in sufficiently close proximity that they are susceptible to the formation of an arc through the air separating them, if the connectors are mated or unmated in the presence of a live current or load. This is true for both mating and unmating, that is movement from the position of FIG. 6 to the position of FIG.  5 . Indeed an arc is more likely to occur as the connectors are unmated under load. To fully mate the connectors  10  and  50 , the lever  70  is rotated from the position shown in FIG. 6 to a position corresponding to that shown in FIG.  1 . In this position, a connector position assurance latch  80  on the lever arm base  78  will engage a surface on the rear of the receptacle housing  12 . This latch  80  can be released to unmate the two connectors. 
     The inertial protrusions  24  and  56  will interfere with movement of pin protection plate  34 , which moves along the mating axis during mating and unmating of the connectors. In the extended position, the pin protection plate will be adjacent the ends of the pins  44 , where it will protect the pins from damage and will prevent an operator from inadvertently contacting the pins before the plug connector  50  is inserted to the pre-stage position. 
     FIGS. 7-14 show a second embodiment of an electrical connector assembly  102  that develops forces which prevent a receptacle connector  110  and a plug connector  150  from remaining in an intermediate, partially mated position in which terminals in the two connectors are in a position in which they are susceptible to arcing. This connector assembly employs an over-center lever  170  to generate a force that will urge the two connectors  110  and  150  away from the intermediate, partially mated, arc susceptible configuration. This force is generated by deflection of an arm  120  to which the lever  170  is mounted. 
     The plug connector  150  is received within a mating cavity  114  that extends into the molded receptacle housing  112 . The mating cavity  114  is formed by four housing walls  118  that form a housing shroud  116 . 
     Mating male and female terminals similar to that shown in the embodiment of FIGS. 1-6 can be employed in connector assembly  102 . Alternatively mating terminals that each can be terminated to wires can also be employed. Although some terminal configurations may be more susceptible to arcing damage than other configurations, the inventive aspects of this connector assembly  102  are not dependent upon the exact configuration of the mating terminals. For this reason, the terminals are not shown in FIGS. 7-14. 
     Receptacle connector  110  includes a molded cantilever beam  120  that extends from the rear of the connector housing  112 . In the preferred embodiment, this arm or beam is part of the one piece molded connector housing  112 , but the cantilever beam  120  could be a separate part attached to the main housing  112 . A separate cantilever beam  120  can also be made of a more resilient material, such as a spring metal, and not be a molded plastic component or extension of the connector housing  112 . The cantilever beam  120  includes a base  122  extending from the rear of the housing  112 . This base  122  is joined to an arm section  124  by an intermediate curved section and that extends parallel to adjacent face of the connector. Wings  126  extend downward from the arm section  124  on opposite sides, and a mechanical assist lever  170  is connected to the cantilever beam  120  by these wings. The lever  170  also is free to rotate or pivot relative to the curved cantilever beam  120 . 
     A slot  130  is formed on each side of the receptacle housing  112 . This slot  130  is wide enough for an actuating pin  178  on the lever  170  to pass through the slot  130  and engage the plug connector  150 . Slot  130  includes an arcuate section  132  adjacent the front of the receptacle connector  110 . The arcuate section  132  has a center of curvature that corresponds with the pivot point or fulcrum  128  of the lever  170 . The slot  130  also includes a linear section  134  that joins the arcuate section  132  and that extends parallel to the mating axis of the connector assembly  102 . As the lever  170  is initially pivoted about the fulcrum  128 , the actuating pin  178  initially follows a curved path while it is in the arcuate section  132 . Thereafter the actuating pin follows a linear path from the front to the rear of the linear slot section  134 . Deflection of the cantilever beam  120  allows the actuating pin  178  to follow this compound path. 
     The molded plug connector housing  152  includes a number of terminal cavities  154  in which plug connector terminals, not shown, can be mounted. Inclined slots  156  are located on opposite sides of the plug connector housing  152 , and lever actuating pin  178 , extending through slot  130  extends into the inclined plug slot  156 . 
     In FIGS. 7 and 8, the receptacle connector  110  and the plug connector  150  are in the pre-stage position. In this position, the plug connector housing  152  would be partially mated with the receptacle connector housing  110 . The actuator pin  178  would extend through slot section  132  and into slot  156 , thus holding the two partially mated connectors together in this pre-stage position. The terminals in the receptacle connector  110  and in the plug connector  150  would be widely spaced and would not be close enough for arcing to occur. 
     In FIGS. 9 and 10, the lever  170  has been rotated about the pivot or fulcrum  128  to a position in which the plug connector  150  is partially mated to the receptacle connector. Rotation of the lever  170  from the position shown in FIGS. 7 and 8 to the position shown in FIG. 9 and 10 causes the pin  178  to move through the arcuate or curved slot section  132 . The pin  178  will also move from the top of plug slot  156  to the bottom of that slot  156  causing a small movement of the plug connector  150  into the mating cavity  114 . Further axial movement of the pin  178  relative to the plug slot  156  is no longer possible, because the pin is now positioned at the root of slot  156 . Although the two connectors  110  and  150  have moved from the pre-stage position to a first partially mated position, the terminals in the two connectors are still not close enough to result in arcing. Movement of the lever from the pre-stage to the first partially mated position has also occurred without deformation or deflection of the cantilever beam  120 , and the pivot or fulcrum  128  has remained in its neutral, unstressed position relative to the remainder of the receptacle connector  110  and the plug connector housing  112 . The pin  128  is not deflected because the actuating pin  178  has moved in a curved slot section  132 , whose center of curvature coincides with the position of pivot or fulcrum  128 . 
     Continued rotation of the lever  170  causes the plug connector  150  to move from the position shown in FIGS. 9 and 10 to the position shown in FIGS. 11 and 12. When the connectors are in the intermediate, partially mated position shown in FIGS. 11 and 12, the leading edge of the receptacle connector terminals are sufficiently close to the leading edges of the plug connector terminals so that arcing can occur between receptacle and plug terminals. However, this is a mechanically unstable position in which the two connectors cannot remain in the absence of some external force holding them in this relative position. Movement of the lever from the position shown in FIGS. 9 and 10 to the position shown in FIGS. 11 and 12 has also resulted in deflection of the cantilever beam  120 . Beam  120  is stressed in this position, and the actuating pin  178  must move axially along the linear slot section  134  in order for the cantilever beam  120  to return to an unstressed condition. Since the pivot  120  and the actuating pin  178  are fixed with respect to the lever arm  174 , movement of the pin  178  along the linear slot section must result in movement of the fulcrum or pivot  128  away from the linear slot  134  as the pivot pin moves axially into a position beneath the pivot point  128 . The upper section  124  of the cantilever beam  120  rotates upward so that the pivot  128  moves away from the slot section  134  and the rest of the receptacle connector housing  112 . Since the cantilever beam  120  is joined to the rest of the connector housing through section  122 , stresses must build up in the cantilever beam  120  at this point. Axial movement of the pin  178  within slot section  132 , from the position shown in FIGS. 11 and 12 will reduce the deflection of cantilever beam  120  and will thus reduce the forces exerted on the plug connector  150  due to deflection of the cantilever beam  120 . Since the configuration shown in FIGS. 11 and 12 represents one in which arcing can occur between plug and receptacle terminals, it is very desirable that the two connectors move away from this position to either separate plug and receptacle terminals or to bring them into sufficient mating engagement so that arcing through air between terminals will no longer occur. 
     FIGS. 13 and 14 show the fully mated configuration of the connector assembly  102 . The plug connector  150  has been moved to this position by continued rotation of the lever  170 . In this fully mated configuration the connector position assurance latch  180  has snapped into engagement with the receptacle connector  110 . The actuating pin  178  has moved toward the root of the slot section  134  and the cantilever beam  120  has returned to its undeflected or neutral position. Terminals are fully mated and arcing will not occur. The connectors  110  and  150  have been brought to this fully mated position by a positive application of an external force to the the mechanical assist lever  170 . However, even if any external force applied to the lever  170  had been removed when the connector assembly  102  was in the intermediate, partially mated, arc susceptible position shown in FIGS. 11 and 12, axial movement of the plug connector  150  relative to the receptacle connector  110 , would still occur because of the spring force built up in the cantilever beam  120  by its deflection. The spring forces generated by the deflected cantilever beam  120  can be reduced either by movement of the plug connector  150  toward the fully mated configuration shown in FIGS. 13 and 14 or toward the initial or pre-stage positions of FIGS. 7-10. Movement in either axial direction will move the terminals away from an arc susceptible position. 
     Both of the representative embodiments depicted herein provide a means for generating a force parallel to the mating axis between two connectors so that the connectors are urged or biased away from an intermediate, partially mated, arc susceptible position. In each embodiment, one connector or a part of a connector housing is deflected to generate the spring force needed to prevent the connectors from residing in the arc susceptible position. In both of the embodiments depicted herein, both the mating and unmating velocities, at least through an arc susceptible region, are higher than for conventional connector configurations that do not include inertial features of which the two embodiments shown herein are representative. Furthermore each of these embodiments is suitable for use with other features, such as mechanical assist levers, terminal guide plates and connector position assurance devices that are typically used on high count electrical connectors, such as those used for automotive applications. Of course their use is not limited to motor vehicle electrical systems or to 42 volt automotive electrical systems. Furthermore, other embodiments would be apparent to one of ordinary skill in the art. The invention is therefore defined by the following claims and is not limited to the representative embodiments depicted herein.