Patent Publication Number: US-9431740-B2

Title: Method of assembling an electrical terminal assembly

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 61/837,835, filed Jun. 21, 2013, and U.S. Provisional Application No. 61/864,155, filed Aug. 9, 2013, the disclosures of which are incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates in general to electrical terminals such as for use in high power vehicle electrical connectors. Electrical connectors commonly include a body having a nonconductive housing encasing a conductive set of female electrical terminals. The set of female terminals are each connected to a respective end of a wire connector or fuse element retained in the housing for completing an electrical circuit. The female terminals are inserted over a set of male blade terminals. For example, the male blade terminals may be housed in another connector housing, such as for example, a power distribution box. The female terminals are typically designed with a spring-type feature to maintain a strong electrical contact with the outer surface of the male terminal blades. 
     Copper has good electrical conductivity properties, and has been a preferred material for terminals even though it is relatively expensive. However, copper is susceptible to relaxation (i.e., loss of spring force) as the temperature of the copper material increases. Since the temperature of the terminals increases as the current drawn in the electrical circuit increases, copper terminals have a reduced ability to maintain strong clamping force onto the male terminal blades. Relaxation of the female terminals may decrease the overall contact area with the male blades, resulting in reduced electrical conductivity, increased resistance, and a further increase in temperature. 
     It is desirable to keep the overall size of an electrical distribution box or other connectors as small as possible while still providing the necessary current-carrying capacity. In some situations, the spring force cannot be further increased by simply making the terminals thicker or wider. When copper is used, the size limitations may make the desired spring force unattainable. 
     During handling and transportation of the female connectors after manufacture, the copper spring contacts of the female terminals are susceptible to being bent and damaged. Therefore, it is desirable to provide a female electrical terminal that is durable while still having desirable spring force characteristics. 
     SUMMARY OF THE INVENTION 
     This invention relates to electrical terminals and, in particular, to a method of assembling a two-piece electrical terminal having a base and a spring member. The base is provided with a plurality of base beams. The spring member is provided with a plurality of spring beams. The spring member defines an axis such that the plurality of spring beams is spaced radially apart from the axis. The spring beams deflected radially outwardly. The base is inserted in the spring member to position the base beams adjacent to the spring beams. The spring beams are released such that the spring beams retract radially inwardly against the base beams. 
     Various aspects of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiments, when read in light of the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an electrical terminal assembly in a fully assembled position. 
         FIG. 2  is a perspective view of the base of the electrical terminal assembly of  FIG. 1 . 
         FIG. 3  is a perspective view of the spring member of the electrical terminal assembly of  FIG. 1 . 
         FIG. 4  is a top plan view of the electrical terminal assembly of  FIG. 1  shown in a partially assembled position. 
         FIG. 5  is a top plan view of the electrical terminal assembly of  FIG. 1  shown in a fully assembled position. 
         FIG. 6  is a cross-sectional view taken along lines  6 - 6  of  FIG. 5  illustrating the electrical terminal assembly in a fully assembled position. 
         FIG. 7  is a perspective view of the spring member having an arbor shown at a pre-position for insertion into the spring member prior to an assembly operation. 
         FIG. 8  is a perspective view illustrating the insertion of the arbor into the spring member, and wherein the base is shown at a pre-position relative to the spring member. 
         FIG. 9  is a partial cross-sectional perspective view illustrating the base being inserted almost fully into the spring member while the arbor is in the same insertion position shown in  FIG. 8 . 
         FIG. 10  is an enlarged partial cross-sectional view taken along lines  10 - 10  of  FIG. 9  illustrating a securing feature of the electrical terminal assembly prior to the fully locked position. 
         FIG. 11  is an enlarged partial cross-sectional perspective view of a portion of the electrical terminal assembly illustrating a second securing feature prior to the fully locked position. 
         FIG. 12  is a bottom view of the spring member of  FIG. 3  illustrating a dovetail interlock. 
         FIG. 13  is a sectional view taken along lines  13 - 13  of  FIG. 12  illustrating the lack of an overlap. 
         FIG. 14  is a perspective view of a second embodiment of spring member. 
         FIG. 15  is a side elevational view of the spring member of  FIG. 14 . 
         FIG. 16  is an end elevational view of the spring member of  FIG. 14 . 
         FIG. 17  is a schematic enlarged plan view of a portion of a blank used to form an interlock feature of the spring member of  FIG. 14 . 
         FIG. 18  is a schematic enlarged plan view of a second portion of the blank used to form the interlock feature of the spring member of  FIG. 14 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the drawings, there is illustrated in  FIG. 1  an electrical terminal assembly, indicated generally at  10 . The electrical terminal assembly  10  includes a base, indicated generally at  12 , and a spring member, indicated generally at  14 . In an assembled condition of the electrical terminal assembly  10 , the base  12  is inserted within the spring member  14 , as shown in  FIG. 1 . In the embodiment shown, the electrical terminal assembly  10  has a rectangular or box-shape such that both the base  12  and the spring member  14  have four sides, as will be described below. The widths of the each of the sides may be equal or unequal. It should be understood that the base  12  and the spring member  14  may be shaped other than a four sided box, as shown in the figures. For example, the base  12  and the spring member  14  may have three sides, six sides, or any suitable number of sides. Alternatively, the base  12  and the spring member  14  may be cylindrical in shape. In a preferred embodiment, the base  12  and the spring member  14  are generally symmetrical about an axis  46 . As will be described below, the base  12  is inserted within the spring member  14  along the axis  46  during assembly of the electrical terminal assembly  10 . 
     The electrical terminal assembly  10  is used to make an electrical connection with an electrical connector, such as a pin  16 , shown in  FIG. 1 . Although the pin  16  is shown having a cylindrical shape, the electrical terminal assembly  10  may also engage with a pin having a non-cylindrical shape. For example, the pin may have a generally rectangular cross-section corresponding to the four-sided electrical terminal assembly  10 . The electrical terminal assembly  10  may be inserted, molded into, or otherwise secured to a plastic body of a connector (not shown). The connector may include multiple electrical terminal assemblies  10  mounted therein. The electrical terminal assembly  10  is well suited for use in high power distribution boxes used in automotive vehicles. 
     The base  12  may be formed from a single metallic blank which is stamped and formed into the configuration shown in  FIG. 2 . Similarly, the spring member  14  may also be formed from a single metallic blank which is stamped and formed into the configuration shown in  FIG. 3 . The base  12  is preferably made of an electrically conductive material such as a copper alloy or an aluminum alloy. Aluminum has an advantage over copper in automotive applications since it is lighter and less expensive than copper. As will be explained below, the spring member  14  generally is provided to assist in forcing or pushing electrical contact engagement surfaces of the base  12  against the pin  16 . Therefore, the spring member  14  is preferably made of a material, such as stainless steel, having a relatively high yield strength or spring-like quality. Preferably, the material of the spring member  14  can retain its spring like qualities over a relatively large temperature range, which can act on the electrical terminal assembly  10  in high power applications, such as within electric or hybrid vehicles. 
     As shown in  FIG. 2 , the base  12  generally includes a box-shaped central or main portion  20  having a front end  22  and a rear end  24 . Extending outwardly from the rear end  24  is a plate  26 . The plate  26  is used to connect with an end of a wire conductor (not shown). The end of the wire conductor may be welded, soldered, or otherwise connected to a flat surface  27  of the plate  26  to provide electrical communication between the wire conductor and the base  12 . The plate  26  can have any shape or configuration suitable for connecting to the end of the wire. As shown in the embodiment of  FIG. 2 , the plate  26  is formed from a pair of relatively thin strip portions  28  of the blank folded against one another. The plate  26  may extend outwardly from the main portion  20  such that it is co-planar with one of the sides of the main portion  20 , as shown in the embodiment illustrated in  FIG. 2 , or it may be configured in other suitable arrangements. 
     The box-shaped main portion  20  includes an upper wall  30 , a bottom wall  32 , a first side wall  34 , and a second side wall  36 . The walls  30 ,  32 ,  34 , and  36  are generally oriented at 90 degrees relatively to adjacent ones. The upper wall  30  includes a protuberance or a tab  38  extending slightly upward from an outer surface  39  of the upper wall  30 . In the embodiment shown, the tab  38  is formed by creating a lateral slit into the upper wall  30  and pushing a slightly deformed portion adjacent the slit upwardly in a stamping or forming operation. As will be explained below, the tab  38  is part of a securing feature for securing the spring member  14  to the base  12 . 
     As stated above, the base  12  may be formed from a single stamped sheet or blank of material folded into the configuration shown in  FIG. 2 . As shown in  FIG. 2 , the main portion  20  may be formed by forming the four walls  30 ,  32 ,  34 , and  36  from a blank and adjoining opposite edges  43  and  45  of the blank. The edges  43  and  45  may include integrally formed locking features to connect the edges  43  and  45  together in a non-overlapping manner. For example, the base  12  may include a dovetail tab  39  extending from the first edge  43  of the blank which interlocks with a correspondingly shaped dovetail recess  41  formed in the second edge  45  of the blank. Of course, the edges  43  and  45  of the blank may also be welded, adhered, or otherwise attached to one another to form the base  12 . However, the use of a dovetail configuration provides a mechanical interlock such that the first edge  43  may not be pulled away from the second edge  45 . The dovetail tab  39  has a flared enlarged portion  39   a  that is connected to the first edge  43  by a reduced necked down portion  39   b.    
     Extending from the front end  22  of the main portion  20  are a plurality of elongated base beams  40  which engage the outer cylindrical surface of the pin  16  to complete an electrical connection between the base  12  and the pin  16 . In the embodiment shown, each of the base beams  40  include a slot  47  formed therein to define a pair of adjacent base beams  40 . A pair of base beams  40  extends from each wall  30 ,  32 ,  34 , and  36 , thereby providing four pairs of base beams  40 . Each of the base beams  40  includes an angled portion  44  extending radially inwardly relative to the axis  46 . Note that the pin  16  is inserted into the base  12  along the axis  46 , as shown in  FIG. 1 . Each of the base beams  40  also includes a tip portion  48  which is curved or bent slightly radially outwardly from the ends of the respective angled portions  44 . The connection between each of the angled portions  44  and the tip portions  48  defines a contact engagement surface  49  for contacting the outer surface of the pin  16 . Note that the use of pairs of base beams  40 , compared to a single base beam having a single contact engagement surface, provides a greater number of contact points with the outer cylindrical surface of the pin  16 . 
     Referring now to  FIG. 3 , the spring member  14  has a box-like shape and includes an upper wall  50 , a bottom wall  52 , a first side wall  54 , and a second side wall  56 . The walls  50 ,  52 ,  54 , and  56  are generally oriented at  90  degrees relatively to adjacent ones. The upper wall  50  includes an opening  58  formed therein. As best shown in  FIG. 6 , adjacent to a front edge  59  of the opening  58  is a resilient finger  60  extending at an angle radially inwardly towards an axis  62  defined by the spring member  14 . The finger  60  is also illustrated in cross-section in  FIG. 11 , as will be discussed below. Note that the axis  62  defined by the box-shaped spring member  14  is co-axial with the axis  46  of the base  12  when the base  12  and the spring member  14  are connected together to form the electrical terminal assembly  10 , as shown in  FIG. 1 . As will be explained below, the opening  58  and the finger  60  of the spring member  14 , and the tab  38  of the base  12  cooperate to provide securing features for securing the spring member  14  relative to the base  12 . 
     Similar to the base  12 , the spring member  14  may be formed by stamping and bending a blank into the configuration of the spring member  14 . The spring member  14  may be formed by forming the four walls  50 ,  52 ,  54 , and  56  from a blank and adjoining opposite edges  53  and  55  of the blank, as shown in  FIG. 12  (bottom view of the spring member  14 ). The edges  53  and  55  may include integrally formed lock features to connect the edges  53  and  55  together in a non-overlapping manner. For example, spring member  14  may include a dovetail tab  61  extending from the edge  53  of the blank which interlocks with a correspondingly shaped dovetail recess  63  formed in the edge  55  of the blank. Of course, the edges  53  and  55  of the blank may also be welded, adhered, or otherwise attached to one another to form the base  12 . However, the use of a dovetail configuration provides a mechanical interlock such that the edge  53  may not be pulled away from the edge  55 . The dovetail tab  61  has a flared enlarged portion  61   a  that is connected to the edge  53  by a reduced necked down portion  61   b . The cross-sectional view of  FIG. 13  illustrates that the dovetail  61  and the recess  63  provide a securing feature that does not have any overlapping portions such that the bottom wall  52  is relatively flat. The presence of a flat wall is ideal for sliding the electrical terminal assembly  10  into a bore of a connector housing (not shown) compared to some conventionally manufactured electrical terminals have raised overlapping regions of their securing features. 
     The walls  50 ,  52 ,  54 , and  56  of the spring member  14  define a box-shaped main portion  64  having a front end  65  and a rear end  66 . Extending from the front end  65  of the main portion  64  is an extension or framework, indicated generally at  67 , that provides protection for the base beams  40  of the base  12 . The framework  67  is defined by four legs  68  extending from the front end  65  of the main portion  64 . In the embodiment shown, the four legs  68  extend from corners of the box-shaped main portion  64 . The forwardly extending legs  68  are integrally attached to a four-sided band  69  generally disposed about the axis  62 . The presence of the framework  67  provides structural rigidity for the spring member  14  as well as providing cage like protection for the base beams  40  of the base  12 . During shipping and handling of the assembled electrical terminal assembly  10 , it is desirable to prevent the base beams  40  from bending out of proper position. The relatively strong stainless steel framework  67  helps provide such protection. The band  69  also functions as a guide during insertion of the pin  16  if the pin is misaligned with the base beams  40 . It should be understood that the spring member  14  may be configured without the framework  67 , thereby reducing the weight of the spring member  14 . 
     Each of the walls  50 ,  52 ,  54 , and  56  includes an elongated spring beam  70  extending forwardly from the front end  65  of the main portion  64 . The spring beams  70  engage the base beams  40  helping to force the contact engagement surfaces  49  against the outer cylindrical surface of the pin  16 . In the embodiment shown, a single spring beam  70  extends from each wall, thereby providing four spring beams  70 . Each of the spring beams  70  includes an angled portion  72  extending radially inwardly towards the axis  62 . Each of the spring beams  70  also includes a tip portion  74  which flares out laterally such that the width of the tip portion  74  is sufficient to engage the pair of respective base beams  40 . 
     The spring member  14  may include a polarizing key feature such that the electrical terminal assembly  10  can be inserted into a connector housing (not shown) in only one desired orientation. This helps direct the wires (not shown) extending from the connector housing in a desired orientation. For example, the bottom wall  52 , or any of the other walls  50 ,  54 , and  56 , may include a radially outwardly extending ear  80 . The ear  80  may provide an interference such that the electrical terminal assembly  10  can only be inserted into the connector housing in a desired orientation. For example, the connector housing may include a four sided hole or bore sized to receive the electrical terminal assembly  10 . The connector housing may include a slot formed in one of the four sides for receiving the ear  80  such that the electrical terminal assembly  10  can only be inserted in one of the four positions. The ear  80  may also be used as a stop member for insertion of the electrical terminal assembly  10  within the bore of the housing by a limited distance. In the illustrated embodiment shown in  FIG. 3 , the ear  80  is formed from bent portions  82  and  84  adjacent edges  86  and  88  of the blank. Location of the polarizing ear  80  at the edges  86  and  88  provides a suitable structure for forming the polarizing key feature. 
       FIGS. 4 and 5  illustrate a first method of assembly of the spring member  14  onto the base  12  to form the electrical terminal assembly  10 . In this first method of assembly, no tools are used to pre-flex the base beams  40  or the spring beams  70 . To assemble, base  12  is inserted into the spring member  14  such that the rear end  66  of the spring member  14  is slipped over the front end  22  (hidden in  FIG. 4 ) of the base  12 , as shown in  FIG. 4 .  FIG. 4  illustrates the electrical terminal assembly  10  at a partially assembled position in which the spring beams  70  have engaged with the base beams  40  and started deflection of the base beams  40  radially inwardly towards the axis  46 . Upon initial contact between the spring beams  70  and the base beams  40 , the tip portions  74  of the spring beams  70  will engage with the tip portions  48  of the respective base beams  40 . Continued movement of the spring member  14  relative to the base  12  will cause the spring beams  70  to deflect the base beams  40  radially inwardly, as shown in  FIG. 4 . Note that the spring beams  70  may also deflect slightly radially outwardly as well but generally not as much due to the higher yield strength of the material of the spring member  14  compared to the material of the base  12 . Further continued movement of the spring member  14  over the base  12  will cause the base beams  40  to move back radially outwardly due to the angled orientation of the tip portions  74  of the spring beams  70  moving past the tip portions  48  of the base beams  40 , as shown in  FIGS. 5 and 6 .  FIGS. 5 and 6  illustrate the electrical terminal assembly at its fully assembled position. 
     When the electrical terminal assembly  10  is in its fully assembled position, as shown in  FIGS. 5 and 6 , optional securing features of the electrical terminal assembly  10  also prevent axial movement of the base  12  relative to the spring member  14 . More specifically, as best shown in  FIG. 6 , the tab  38  of the upper wall  30  of the base  12  is disposed in the opening  58  of the upper wall  50  of the spring member  14 . An edge of the tab  38  engages with an edge  57  of the opening  58  to prevent the spring member from moving in a rightward direction, as viewing  FIG. 6 , relative to the base  12 . Note that during insertion of the base  12  into the spring member  14 , the base  12  and/or spring member  14  may flex to accommodate the tab  38  sliding along a lower surface of the upper wall  30  of the base  12 . The tab  38  will then snap upwardly into the opening  58  when positioned therein. To prevent movement in the other direction, the finger  60  of the spring member  14  engages with an edge  75  of the slot  47  formed between the pair of base beams  40  on the upper wall  30  of the base  12 . 
     As shown in  FIG. 6 , the distance X between the contact engagement surfaces  49  of opposed tip portions  48  of the base beams  40  is preferably less than the width of diameter of the pin  16 . When the pin  16  is inserted into the electrical terminal assembly  10  during use thereof, the tip portions  48  of the base beams  40  and the tip portions  74  of the spring beams will deflect radially outwardly to accommodate the insertion of the pin  16 . This deflection biases the contact engagement surfaces  49  of the base beams against the outer surface of the pin  16 . 
       FIGS. 7 through 9  illustrate a second method of assembly of the spring member  14  onto the base  12 . In this second method of assembly, a tool, such as an elongated arbor  90 , is used to first flex the spring beams  70  radially outwardly prior to insertion of the spring member  14  onto the base  12 . In the illustrated embodiment, the arbor  90  has a generally cross shaped cross-section. The arbor  90  includes an elongated central body  91  having a generally rectangular cross-section. The arbor  90  further includes an upper rib  92 , a lower rib  94 , and a pair of side ribs  96  and  98  that extend radially outwardly from the central body  91 , as shown in  FIG. 7 . End portions of the ribs  92 ,  94 ,  96 , and  98  may include ramped surfaces  100  which initially engage with the tip portions  74  of the spring beams  70  during insertion of the arbor  90 . 
     During the second method of assembly, the arbor  90  is first moved from a non-engaged position, as shown in  FIG. 7 , to an engaged position, as shown  FIG. 8 , such that the arbor  90  is inserted into the spring member  14 . During initial insertion, the tip portions  74  of the spring beams  70  slide along the four ramped surfaces  100  of the respective ribs  92 ,  94 ,  96 , and  98  such that the tip portions  74  are deflected radially outwardly until the tip portions  74  are positioned on the elongated axial surfaces of the ribs  92 ,  94 ,  96 , and  98  to their fully deflected position, as shown in  FIG. 8 . The base  12  is then inserted into the rear end  66  of the spring member  14 , as shown in  FIG. 9 . During insertion, the tip portions  48  of the base beams  40  may slide along portions of the central body  91  of the arbor  90 , as shown in  FIG. 9 . The width W of the central body  91  may be equal to or less than the distance between contact engagement surfaces  49  of opposed tip portions  48  such that the base beams  40  are not deflected during insertion of the base  12  within the spring member  14 . Of course, the arbor  90  may be sized such that a slight deflection of the base beams  40  may occur. 
     During insertion of the base  12  onto the arbor  90 , as show in  FIG. 9 , the ribs  92 ,  94 ,  96 , and  98  extend into the respective slots  47  between the corresponding pair of base beams  40  of the base  12 . Thus, the presence of the slots  47  permits the ribs  92 ,  94 ,  96 , and  98  of arbor  90  to engage with and extend the spring beams  70  radially outwardly without engaging with and extending the base beams  40  outwardly. 
       FIG. 9  illustrates the electrical terminal assembly  10  in a not yet fully assembled position such that the securing features have not yet engaged with one another. As shown in  FIG. 10 , the upper wall  50  of the spring member  14  may be spaced from the upper wall  30  of the base  12  by a distance or gap G. The gap G may be significantly reduced once the electrical terminal assembly  10  is in its fully secured position and the tab  38  extends into the opening  58 . Note that the tab  38  may include a ramped surface  101  to avoid interference during the insertion of the base  12  within the spring member  14 .  FIG. 11  illustrates the finger  60  being disposed within the slot  47  formed between the pair of base beams  40  on the upper wall  30  of the base  12  prior to full assembly. 
     When the base  12  is fully inserted into the spring member  14  and the securing features are engaged, as described above, the arbor  90  may be removed, thereby causing the spring beams  70  to deflect radially inwardly against the base beams  40 . Although the first method of assembly of the electrical terminal  10  does not use any tools, such as the arbor  90 , and may be less complicated, the second method of assembly has the advantage of not imparting too much bending force (overstressed force) on the base beams  40  due to the inward deflection against the spring beams  70 . Additionally, the width Z of the base beams  40 , as shown in  FIG. 8 , may be made wider than the base beams  40  used in an electrical terminal assembly  10  assembled in the first assembly method. For the first assembly method, the width Z of the base beams  40  are configured at a dimension enabling the tip portions  48  of the base beams  40  to be pushed radially toward one another during the radially inward deflection caused by the spring beams  70  being slipped over the base beams  40 . Note that although the curved radially outwardly configuration of the tip portions  48  of the base beams  40  requires deflection of the base beams  40  when inserting into the spring member  70 , removal of the curved tip portions  48  may not be desired. The curved regions at the contact engagement surface  49  at the tip portions  48  provide a relatively good contact engagement with the outer surface of the pin  16  compared to straight formed base beams (not shown) wherein the contact engagement surface is the very edge of the elongated straight beam. 
     There is illustrated in  FIGS. 14 through 16  a second embodiment of a spring member, indicated generally at  214 . The spring member  200  may be used in place of the spring member  14  used in the electrical terminal assembly  10  described above. One of the main differences between the spring member  214  and the spring member  14  is that the spring member  214  includes a different locking feature, indicated generally at  215 , compared to the non-overlapping dovetail  61  configuration shown in  FIGS. 12 and 13 . The locking feature  215  may be integrally formed from a blank that is used to form the spring member  214  and is located in one of the walls  217  of the spring member  215 . For example, there is illustrated in  FIGS. 17 and 18 , portions of a blank  216  which are used to form the spring member  214 .  FIG. 17  illustrates features formed adjacent a first edge  220  of the blank  216 .  FIG. 18  illustrates features formed adjacent a second edge  222  of the blank  216 . The mating of the corresponding edges  220  and  222  can be seen in the assembled views of  FIGS. 14 through 16 . As will be explained below, the locking feature  215  helps prevent the first and second edges  220  and  222  from moving apart from one another in all three dimensional coordinate directions, labeled X, Y, and Z (Z 1  and Z 2 ) in  FIG. 14 . 
     Referring to  FIG. 17 , a tab  230  extends outwardly from the first edge  220 . The end of the tab  230  includes head portion  232  having a width which is larger than a neck portion  234 . The head portion  232  defines a pair of extensions  236  extending outwardly from the neck portion  234 . The tab  230  also includes a pair of wings  238  extending from the neck portion  234 . The wings  238  are spaced from the first edge  220  to define a pair of recesses  239 . The recesses  239  are spaced from one another by a distance x 1  and have a width y 1 , as indicated in  FIG. 17 . 
     Referring to  FIG. 18 , a stepped slot or recess  260  is formed in the blank  220  adjacent the second edge  222 . The recess  260  has a width x 2  adjacent the edge  222  and then narrows to a smaller width preferably having about the same width dimension as the neck portion  234  of the tab  230 . A pair of flaps  262  are provided adjacent the recess  260 . L-shaped cut-outs  264  can be formed in the blank  216  to define outer sides of the flaps  262 . The cut-outs  264  also define a pair of tab portions  265  spaced apart from one another the distance x 2 . 
     As shown in  FIG. 14 , to assembly the locking feature  215 , the flaps  262  are bent outwardly in the Z 2  direction from the surface of the blank  216  and are positioned over the wings  238  (hidden from view) of the tab  230 . Note that in the final assembly of the spring member  214 , the wings  238  are flush with the surrounding portions of the blank  216  while the flaps  262  are positioned outwardly therefrom in the Z 2  direction. Additionally, the tab portions  265  are positioned within respective recesses  239 . The dimensions x 1  and x 2  are preferably approximately equal to one another. The dimensions y 1  and y 2  are preferably approximately equal to one another. This configuration traps the tab portions  262  within the respective recesses  239  such that the edges  220  and  222  of the blank  216  are prevented from moving away from each other in the X and Y directions. During the final assembly process, the neck portion  234  of the tab  230  is bent in a U-shaped manner, as shown in  FIG. 16 , such that the extensions  236  of the head portion  232  are disposed over portions of the flaps  262 , as best shown in  FIG. 14 . Thus, the flaps  262  are captured and disposed between the wings  238  and the extensions  236 . This captured arrangement prevents the first edge  220  from separating from the second edge  222  in the Z direction. More specifically, the extensions  236  engaging with the flaps  262  prevent the edge  220  from moving in the Z 1  direction relative to the edge  222 . The flaps  262  engaging with the wings  238  prevent the edge  220  from moving in the Z 2  direction relative to the edge  222 . Additionally, the edges  220  and  222  are prevented from being moved relative to one another along the X direction due to the neck portion  234  being disposed in the recess  260 . Thus, the locking feature  215  provides a mechanical lock preventing the tab  230  from moving relative to the recess  260  in all three dimensions by physical blocking. Note that the dovetail locking feature provides mechanical locking in two dimensions while utilizing frictional interference engagement to prevent movement in the third dimension. 
     The principle and mode of operation of this invention have been explained and illustrated in its preferred embodiments. However, it must be understood that this invention may be practiced otherwise than as specifically explained and illustrated without departing from its spirit or scope.