Patent Publication Number: US-6908348-B2

Title: Box terminal with extended contact surfaces and controlled damage location during high voltage arcing with and without suppression under a magnetic field

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application claims priority of U.S. Provisional Application Ser. No. 60/429,469, filed Nov. 27, 2002, and entitled “Box Terminal With Extended Contact Surfaces and Controlled Damage Location During High Voltage Arcing With and Without Suppression Under a Magnetic Field. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to male to female contact terminals, particularly those in use with associated wire harnesses or cables involved in higher voltage and current carrying vehicle applications. More specifically, the present invention discloses an improved female terminal design for interengaging with a projecting blade of a male terminal and which in particular provides the combined features of improved contact area and controlled blade insertion. Additional features of the present design include the female terminal exhibiting one or more initial (sacrificial) contact points at the blade insertion end and which functions, with or without the application of a magnetic field inducing Lorentz force, to provide a controlled location at which voltage induced arcing will occur along the female terminal and without compromising the electrical interface created between the male terminal blade and the female terminal beams. The sacrificial contact tabs further provide a small area for applying any coatings, such as nickel, ceramic, silver, gold and others, which further reduce the damage resulting from arcing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Reference will now be made to the attached drawings, when read in combination with the following detailed description, wherein like reference numerals refer to like parts throughout the several views, and in which: 
         FIGS. 1A and 1B  are prior art schematic views of before and after conditions of a female to male contact terminal undergoing an arc discharge phenomenon and which results in the damage caused to the terminals; 
         FIG. 2  is a further diagrammatic and prior art schematic view of a known arc-prevention assembly termed as a magnetic field creating Lorentz force; 
         FIGS. 3A ,  3 B and  3 C are additional views according to the prior art and which explain the phenomenon associated with the creation of the Lorentz forces; 
         FIGS. 4A ,  4 B and  4 C illustrate first, second and third perspective and rotated views of a female box terminal according to the present invention and for receiving a male terminal insertion blade; 
         FIGS. 5A and 5B  are first and second partially cutaway and rotated perspective views of the box terminal as shown in  FIGS. 4A-4C  and which illustrate the configuration of the angled and torsioned beams with the further removal of the outer rectangular cage portion; 
         FIG. 6  is a plan view of a one-piece and configurable blank associated with the female terminal according to the present invention; 
         FIG. 7  is an enlarged side presented perspective view, in partial cutaway, and which more clearly illustrates the features of the forwardly positioned and sacrificial contact tabs associated with the insertion end of the female terminal, combined with the intermediate located and opposingly arrayed overstress protection ribs and against which the angled beams abut during male blade insertion; 
         FIG. 8  is an enlarged perspective view of the open insertion end associated with the female terminal according to the present invention; 
         FIGS. 9A and 9B  are perspective and cutaway schematic views of a pre-engagement position established between the female terminal and an associated male terminal according to the present invention; 
         FIGS. 10A and 10B  are perspective and cutaway schematic views of a progressive-engagement position established between the female terminal and an associated male terminal illustrated in  FIGS. 9A and 9B ; 
         FIG. 11  is a pre-engagement view, similar to that shown in  FIG. 9A , and illustrating the arc reducing magnets in place about the female terminal; 
         FIG. 12  is a progressive engagement view, similar to that shown in  FIG. 10A , and again illustrating the position of the arc reducing magnets according to the present invention; 
         FIG. 13  is a substantial duplicate of FIG.  8  and again illustrating an enlarged perspective view of the open insertion end associated with the female terminal according to the present invention; 
         FIGS. 14A and 14B  are perspective and cutaway schematic views of a pre-engagement position established between the female terminal and an associated male terminal according to a 16 way connector terminal array according to a further preferred embodiment of the present invention; 
         FIGS. 15A and 15B  are perspective and cutaway schematic views of a progressive-engagement position established between the multiple female terminal and an associated male terminal array illustrated in  FIGS. 14A and 14B ; 
         FIG. 16  is a pre-engagement view, similar to that shown in  FIG. 14A , and illustrating the arc reducing magnets in place about the multiple female terminal array; 
         FIG. 17  is an initial and proceeding engagement view, similar to that shown in  FIG. 15A , and again illustrating the position of the arc reducing magnets according to the present invention; 
         FIG. 18  is an enlarged perspective view of the open insertion end associated with a rectangular female terminal and which illustrates a single male blade engaging contact tab according to a further preferred embodiment of the present invention; 
         FIGS. 19A and 19B  are perspective and cutaway schematic views of a pre-engagement position established between the female terminal in FIG.  18  and an associated male terminal according to the present invention and with the arc reducing magnets in place about the female terminal in proximity to the inserting end location; 
         FIGS. 20A and 20B  are perspective and cutaway schematic views of a progressive engagement position established between the female terminal and an associated male terminal illustrated in  FIGS. 19A and 19B ; 
         FIG. 21  is a view substantially identical to that previously illustrated in FIG.  18  and with the exception of an alternatively configured engagement tab according to the present invention; 
         FIGS. 22A and 22B  are perspective and cutaway schematic views, similar to that previously illustrated in  FIGS. 19A and 19B , respectively, and further showing the alternatively configured engagement tab relationship of  FIG. 21 ; 
         FIGS. 23A and 23B  are perspective and cutaway schematic views, similar to that previously illustrated in  FIGS. 20A and 20B , respectively, and showing the manner of engagement of the male blade with the female terminal as also shown in  FIGS. 22A and 22B ; 
         FIG. 24  is an illustration of an open inserting end of a rounded female terminal according to the present invention and which illustrates a single initial contact tab; 
         FIGS. 25A and 25B  are perspective and cutaway schematic views of a pre-engagement or last engagement position established between the female  24  and an associated and round inserting male terminal according to the present invention; and 
         FIGS. 26A and 26B  are perspective and cutaway schematic views of the progressive engagement position established between the female terminal and an associated male terminal illustrated in FIGS.  25 A and  25 B. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring now to  FIGS. 1A and 1B , a series of environmental views are shown at  10  and  14 , according to the known art, and which illustrated, respectively, before and after conditions of a female to male contact terminal undergoing an arc discharge phenomenon. As is known in the art, higher voltages which are associated with such male to female terminal assemblies, and in particular such as vehicle assemblies which require operation at higher (e.g., 42V) operating voltages and which tend to cause arcing across the terminals as a result of an excessive amount of electrical energy (voltage and current), beyond which the terminal design is capable of sustaining and transferring. 
     As is best illustrated at  14  in  FIG. 1B , the by-product of electrical arcing is most typically heat and which can result in melting of a portion of the terminal assembly. The direction of arcing is usually counter to the flow of current, illustrating at  16  in  FIG. 1B , and results, in this instance, in a portion  18  of a female interconnecting terminal being melted, thus opening the current path along the terminal assembly. 
     Referring to  FIG. 2 , one known attempt at minimizing the likelihood of high voltage arcing is accomplished, as generally shown at  20 , by the creation of a lengthened energy flow path between associated gaps in male  22  to female  24  interface terminals (and such as previous or subsequent to engaging contact being established between the terminals  22  and  24 ). Electric wires (or cables) associated with the male  22  and female  24  terminals are further illustrated at  26  and  28 , respectively, and further illustrated schematically is an experimental set-up of a magnetic field  30 . 
     This field  30  is further understood to be created by the placement of a pair of attracting magnets (not shown in this illustration) perpendicular to the location of the male blade and associated female housing and such that a Lorentz force generated and arcing path  32  is created. A Lorentz force is generally calculated, according to the equation F=qv×B, to be the product of the electrical charge (q), the particle travel velocity (v) and the magnetic field direction (B). The furthering advantage of lengthening the arcing path between the associated male and female terminals is to draw as much energy as possible from the energy being transferred and in the attempt to minimize the arcing condition. 
     Referring further to  FIGS. 3A ,  3 B and  3 C, additional views are provided, again according to the prior art, and which further explain the physical phenomenon associated with the creation of the Lorentz forces. In particular, it is desired to place the magnets, see at  34  and  36  in  FIG. 3A , as closely together as possible in order to create the strongest possible magnetic field, and associated arcing path, at the arcing zone between the terminals. Referring to  FIG. 3B , the equation is presented at  38  for calculating the magnetic flux density at a given center point X established between the two magnets  34  and  36 . Referring further to  FIG. 3C , a graph is presented at  40  of arc energy to magnetic flux density variables and for both of large current and small current loads. The graph  40  further seeks to establish a desired target zone (such as for example exists in a 14V-300 W input condition) and within which the creation of an excessive degree of arc energy is avoided. 
     It has been found that damage occurring at the electrical interface zone, established between a plurality of elongated and angled beams of a female terminal and an associated and inserting male terminal pin or blade (not clearly shown in this illustration), can effectively interrupt the electrical flow path established between the terminals and even in the absence of the catastrophic results achieved in FIG.  1 B. This is so because, even in instances in which the overall damage caused by the arcing is small, any such damage occurring between the interengaging male blade/pin and female beams can affect the terminal function. Accordingly, and in view of the fact that such arcing conditions often occur at the main interengaging location between the male and female terminals, it is desirous to both control and redirect any damage resulting from arcing conditions to locations as far as possible remote from this main contact location so that, upon the occurrence of an arcing event, the remaining functionality of the terminal assembly is not impaired. 
     Referring to  FIGS. 4A ,  4 B and  4 C a series of first  50 , second  50 ′ and third  50 ″ perspective and rotated views are illustrated of a female box terminal according to a first preferred embodiment of the present invention. The female box (rectangular) terminal  50  is particularly suited for receiving, in inserting and interengaging fashion, a male insertion blade (not shown) of an associated. As best illustrated in  FIG. 4A , the female terminal includes a forwardly directed, elongated and rectangular shaped cage portion  52  terminating in an open inserting end  54 . One or more locking windows  53  are located through a selected face or faces of the terminal cage portion  52  and are intended to interengage with suitable sidewise projecting structure (not shown) associated with the male terminal and in order to maintain the engaged relationship between the male and female terminals. Pairs of cable gripping portions, see at  56  and  58 , are provided for engaging over an exposed end of a suitable cable or wire (see again at  26  and  28  in  FIG. 2 ) and extend from an interconnecting portion  59  of the main cage portion  52 . 
     As best further shown in the partial cutaway illustrations of  FIGS. 5A and 5B , first and second pairs of angled and torsioned beams  60  and  62  are revealed inside of the rectangular cage portion  52  (again removed for purpose of these illustrations). The configuration of the beams  60  and  62  is such that, upon inserting engagement of the male blade through the open end  54  of the female terminal, the beams  60  and  62  provide the combined features of increased contact area with respect to the male blade, while at the same time providing reduced insertion forces concurrent with providing increased normal (perpendicular) directed holding forces of the male blade. 
     It has further been found that male blade insertion forces are affected by both the deflection of the beam along its longitudinal direction, combined with torsional deflection in a perpendicular direction. As is also shown in  FIG. 6 , the female terminal can be constructed from a one-piece blank design and which is bent and manipulated according to a suitable manufacturing process in order to achieve the completed shape shown in  FIGS. 4A-4C . 
     Referring now to  FIG. 7 , an enlarged side presented perspective view is shown, again with the outer layer of the rectangular cage portion  52  in cutaway, of the female terminal. More clearly illustrated in  FIG. 7  is the feature of a pair of forwardly positioned and sacrificial contact tabs, see at  64  and  66  and as is also shown in  FIGS. 4A and 5A , associated with the insertion end  54  of the female terminal. The contact tabs  64  and  66  provide an initial contact point between the female terminal and the associated male terminal during their interengagement (as well as a final point of contact during reverse disengagement). 
     It is the intended feature of the contact tabs  64  and  66  to provide a remote location, away from the electrical interface established between the contact beams  60  and  62  and the associated and interengaging male terminal blade (on sides of male terminal, not shown in this illustration) for accommodating and receiving an electrical arcing event and as has been previously described. In this manner, the integrity of the electrical interface established between the contact beams  60  and  62  and the male blade can most likely be saved in favor of sacrificing the initial contact tabs  64  and  66 . 
     As will be further explained in reference to subsequent variants, any number of contact tabs (or even a single tab) can be located at the open inserting end and can adequately function to provide an arcing bridge away from the main electrical interface. It is further desired that the surfaces of the contact tabs  64  and  66  can be coated with a suitable and arcing-resistant material, such as may further include coatings of nickel, ceramic, silver, gold, among others, and in an attempt to further elevate the threshold at which an arcing event will occur. It is also important to note that the configuration of the female terminal with the sacrificial contact tabs, can be utilized both with and without the Lorentz force inducing magnets and within the scope of the present invention. 
     Referring again to  FIG. 7 , an additional feature of the female terminal is the provision of a pair of contact ribs  68  and  70  which extend in laterally extending, inwardly projecting and opposing fashion from opposing interior walls of the rectangular cage portion  52 . Upon insertion of the male blade, the angled beams  60  and  62  are engaged and biased outwardly into an abutting contact with the ribs  68  and  70 . At this point, the ribs  68  and  70  protect against overstressing the elongated beams  60  and  62  during blade insertion. Additionally, it has been found that at least one of the ribs  68  and  70  function to provide a secondary benefit of conducting current through the main electrical interface. 
     Having undertaken an explanation of the female terminal design according to  FIGS. 4A-7 , reference will now be made to the succeeding figures and which illustrate various assembly arrangements of the female terminal according to the present invention, in combination with an appropriately configured and interengageable male terminal and the Lorentz force inducing magnets. Referring to  FIG. 8 , an enlarged perspective view is illustrated at  72  of the forward inserting end of the female terminal, as substantially previously described and which again includes such features as the rectangular spring cage portion  52 , locking window  53 , open inserting end  54  and configured pre-engagement tabs  64  and  66 . 
     Referring further to  FIGS. 9A and 9B , perspective and cutaway views are respectively shown of a pre-engagement position established between the female terminal  72  and an associated male terminal  74 . As previously discussed, the male terminal  74  is constructed so that it likewise includes a main and electrically conducting body  76  terminating at one end in wire or cable gripping portions, see at  77  and  78 , and at the other and forwardly projecting end in a male inserting blade  80 . It is also understood that, while capable of being uniquely configured with a suitable female terminal design and for a given assembly application, the male terminal  74  may also be provided as a stock item from a number of different manufacturers and for use with the female terminal configuration according to the present invention. 
     As further shown in  FIGS. 10A and 10B , perspective and cutaway views are illustrated of an engagement position established between the female terminal  72  and associated and interengaged male terminal  74 . In particular, the cross sectional cutaway of  FIG. 10B  illustrates the engagement of the tongue inserting end of the male blade  80  with the opposing and inwardly/laterally projecting contact tabs  64  and  66 . As previously described, the tabs  64  and  66  operate to provide a sacrificial conduit for receiving the electrical and heat energy associated with an arcing event and to safeguard the integrity of the main electrical interface established between the angled and longitudinally extending beams of the female terminal. As further previously explained, it is understood that the configuration of the female terminal design, exhibiting one or more sacrificial and arc-locating contact tabs, is a focus of the invention and that such can further be provided either both with or without the Lorentz force inducing magnets. 
     Referring now to  FIGS. 11 and 12 , illustrated are both pre-engagement and progressive engagement views of the female and male terminals, and further illustrating the positioning of arc reducing magnets  82  and  84  in place about the female terminal. In particular, the magnets  82  and  84  are placed in relation to a forward most end of the female terminal  72 , proximate the open inserting end and the location of the initial contact tabs  64  and  66 . 
     As further previously explained, it is desirable that the attracting magnets  82  and  84  be placed as close together as is possible and in order that a maximum Lorentz force arcing path (as previously illustrated and described in  FIG. 2 ) be created. In this manner, the electromagnetic arcing path thus created will serve the initial function of dissipating some of the excessive electrical energy between the male and female terminals, and by virtue of the lengthened flow path. Further, and at the point at which an arcing event is inevitable and will occur, the manner and location in which the magnets are positioned will further serve to facilitate the arcing event in proximity to the initial contact tabs  64  and  66  and to thus further segregate the electrical arcing at the tabs  64  and  66  and to again safeguard the main electrical interface within the female terminal interior. 
     Referring now to  FIG. 13 , a substantial duplicate of the illustration of  FIG. 8  is again shown of the female terminal and such that a repetitive description thereof is unnecessary. Referring further to  FIGS. 14A and 14B , both perspective and cutaway views of a pre-engagement position established between a selected female terminal (such as previously described at  72 ) and an associated male terminal (and further such as previously described at  74 ) are illustrated and according to a  16  way connector terminal array in a further preferred embodiment of the present invention. 
     The pre-engagement illustrations of  FIGS. 14A and 14B , in addition to the progressive engaging position of  FIGS. 15A and 15B , illustrate identically configured female  72  and interengageable male  74  terminals, such that additional and repetitive description is unnecessary, and in a multiple arrayed fashion (again a “16” way array as previously stated). Referring further to  FIGS. 16 and 17 , both pre-engagement and progressive-engagement views are again shown of the multiple terminal array and which further illustrate arc reducing magnets  86  and  88  in place about the multiple female terminal array. 
     The magnets  86  and  88  are similar in nature to those previously shown at  82  and  84  in  FIGS. 11 and 12 , except that they are elongated to accommodate the multiple arrays of female  72  and male  74  interengageable terminals. It is further the purpose of these illustrations to exemplify one possible multiple/plural arrangement of female/male terminals and it is further understood that any given multiple arrangement of interengageable terminals can be incorporated according to the present invention. The orientation of male and female terminals is conventionally known, therefore any modifications of such existing connection systems, in particular the installation of the magnets, is minimized. 
       FIG. 18  is an enlarged perspective view  90  of an open insertion end  92  associated with a rectangular female terminal  94  and which further illustrates a single male blade engaging contact tab  96  according to a further preferred embodiment of the present invention. As previously explained, it is possible that a single contact tab, or any plurality of contact tabs, can be incorporated into the design of the female terminal  94  and within the scope of the invention. 
     As is also illustrated in the perspective and cutaway views of  FIGS. 19A and 19B , a male inserting blade  98  is illustrated in position proximate the female open inserting end  92  and also shown are a pair of arc reducing magnets  100  and  102  in place about the female terminal in proximity to the inserting end location. Additional features associated with the female terminal  94  include the provision of side positioned locking windows, see at  104  and again for the purpose of being engaged by suitable structure extending from the associated male terminal (not shown). 
     Additionally, configured gripping tabs  106 , see in particular in  FIG. 20A  are shown and for engaging the extending end of an associated wire or cable (not shown). Further, and referring to the side cutaway views of  FIGS. 19B and 20B , interlocking keystone portions  108  and  110  are provided along a top surface of the female terminal  94  and, upon being compressed, facilitate the mechanical holding and compressing forces of an interiorly configured spring cage (not shown) relative to the male inserting blade  98 . 
       FIGS. 20A and 20B , in similar fashion to several of the preceding described embodiments, illustrate perspective and cutaway views, respectively, of a progressive engagement established between the female terminal  94  and associated male terminal (blade  98 ) as illustrated in  FIGS. 19A and 19B . It is also important to note that the inserting illustration as best shown in  FIG. 20B  does not necessarily represent the final inserting position of the male blade  98  relative to the open interior of the female terminal  94 , rather it is primarily intended to identify the initial contact (or pre/post contact) position of the blade  98  relate to the female tab  96  and at which an arcing event is likely to occur. 
     Also, it is worth pointing out here that the male terminal blades, in any of the several preceding embodiments, will arc along their side extending edges, due to the configuration and placement of the initial/sacrificial contact tabs associated with the female terminals. In this fashion, it is intended that the attendant damage to the male terminal blades be likewise limited, and as opposed to the arcing event occurring across the planar face or faces of male blades, which would further again result in substantial damage or destruction to the main electrical interface existing between the faces of the blade and the associated beams of the female terminal. 
       FIGS. 21 ,  22 A &amp;  22 B, and  23 A &amp;  23 B illustrate a rectangular male to female terminal assembly virtually identical to that illustrated and described in reference to  FIGS. 18 ,  19 A &amp;  19 B, and  20 A &amp;  20 B, and with the exception of a modified configuration of a single initial contact tab  112  and in substitution of that previously described and identified at  96 . The tab  112  in this variant is presented as a rearwardly and inwardly directed tang portion, and opposite to the forwardly and inwardly projecting direction of the tab  96  in the previous variant. Accordingly, and again, a repetitive description of the elements common to both of these sub-variants is unnecessary. 
     Finally, and now referring to  FIG. 24 , an illustration is provided at  114  of a rounded female terminal according to a still further variant of the present invention. The rounded terminal  114  includes a circular body  116 , terminating in a forwardly directed and open inserting end  118 . An initial contact tab  120  is illustrated and which extends from an interiorly held and substantially helix shaped spring cage  122  forming a part of the female terminal. As previously explained, any number of contact tabs  120  can be incorporated, ranging from one upwards, into the present design and the intention is that a leading inserting end of a rounded male inserting pin  124  come into initial contact for engagement or last contact for disengagement with the projecting tab  120  (see in particular cutaway of  FIG. 26B ) and thus electrically arc at that point and prior to completion of the inserting engagement or after completion of disengagement from main contact at which point the main electrical interface may be put in jeopardy. 
     Referring again to  FIGS. 25A and 25B , perspective and cutaway views are illustrated of both the pre-engagement or last engagement position established between the female terminal of FIG.  24  and the associated and round inserting male terminal. FIGS.  26 A and  26 B again are perspective and cutaway views of the progressive engagement position established between the female terminal and an associated male terminal and as previously explained. 
     All descriptions of the above paragraphs are applied to a disengagement situation, in which the tab(s) provide a last contact location during disengaging of the male and female terminals. The arcing is therefore localized on the tab(s) and the associated sides of the male terminal. Accordingly, it is not necessary to repeat the above described structure. 
     Having described our invention, it is evident that it discloses and teaches an improved female terminal design for initiating or limiting and localizing inevitable electrical arcing events at a forward and initial-engagement (or backward and disengagement, respectively) position and in order to safeguard a main electrical interface with an inserting (or disengaging) male terminal. The present invention further provides an improved assembly which, when utilized along with Lorentz force producing magnets, both increases the threshold at which an arcing event will occur (again by increasing the energy necessary to arc as a result of the establishing of the arcing path by the magnets) and again by localizing the arcing event at the forward initial engagement (or backward disengagement) end of the terminals. 
     The present invention accordingly also reduces the damage at the forward inserting (or disengagement) end of the female terminal by attempting to localize the same to the sides of the terminal, as well as along the corresponding and narrowed side edges of the male inserting blade (and not its top and bottom faces). Furthermore, the incorporation of the modified female terminal design (with or without the Lorentz force inducing magnets) can be accomplished without any major modifications to existing terminal systems and is additionally compatible with existing male connectors in either singular or multiple terminal arrangements. The tab(s) again also provide small area(s) upon which are applied any of a varying number of cost-effective coatings such as nickel or ceramics, among others. These coatings further help to reduce arcing damage. 
     Additional preferred embodiments will become apparent to those skilled in the art to which it pertains and without deviating from the scope of the appended claims.