Abstract:
A crimping apparatus and method are provided that enable secure crimping of objects to one another even when the objects are subject to thermal or stress cycling. Specifically, an apparatus for crimping a work-piece includes a die pair with a first die that defines a first groove characterized by a first cross-sectional shape as well as a second die opposing the first die. The second die defines a second groove characterized by a second cross-sectional shape different than the first cross-sectional shape. When the dies are moved together for crimping the work-piece, the first and second grooves are aligned to define a die cavity with a compound cross-sectional shape for crimping the work-piece.

Description:
TECHNICAL FIELD 
     The invention relates to a pair of die for crimping two components to one another and a method for the same. 
     BACKGROUND OF THE INVENTION 
     Crimping two pieces of metal or other materials to one another, by deforming one or both of them to hold the other, is used extensively in metalworking. Crimping is also used to connect an electrical connector to a conductive component such as an electrical wire. Crimping is a cold-working technique that can form a strong bond between the two crimped objects. 
     Certain materials, such as brittle materials or other materials with difficult cold-working properties, may be difficult to crimp to other materials. Additionally, when one of the objects is subjected to thermal or stress cycling, the bond created by crimping may weaken or fail. For example, if an electrical connector is crimped to an active material such as a shape memory material wire using a standard crimp with a uniform cross-sectional area (such as a circular crimp or a barrel crimp), the cyclical shape change of the active material occurring with thermal cycling may diminish the bond. 
     SUMMARY OF THE INVENTION 
     A crimping apparatus and method are provided that enable secure crimping of objects to one another even when the objects are subject to thermal cycling. 
     Specifically, an apparatus for crimping a work-piece includes a die pair with a first die that defines a first groove characterized by a first cross-sectional shape as well as a second die opposing the first die. The second die defines a second groove characterized by a second cross-sectional shape different from the first cross-sectional shape. For example, the first cross-sectional shape may be rectangular while the second may be triangular. When the dies are moved together for crimping the work-piece, the first and second grooves are aligned to define a die cavity with a compound cross-sectional shape for crimping the work-piece. 
     Preferably, each of the first and second dies has first and second portions connected to one another. Each portion defines a respective segment of the groove in the die. The groove is therefore multi-segmented, and has different cross-sectional shapes in the different segments. Specifically, the first groove may have the first cross-sectional shape in the first portion and be further characterized by the second cross-sectional shape in the second portion. The second groove may be characterized by the second cross-sectional shape in the first portion and by the first cross-sectional shape in the second portion. Thus, in such an embodiment, like cross-sectional shapes are positioned diagonally from one another when the first and second portions are connected together. Accordingly, the die cavity formed by the grooves when the dies move together has a compound cross-sectional shape in the first portion and a compound cross-sectional shape in the second portion that is rotated with respect to the shape of the first portion. A multi-segmented, compound cross-sectional shape can therefore be imparted to the work-piece crimped by the die pair. Alternatively, different cross-sectional shapes may be positioned diagonally from one another. 
     Another preferable feature of the crimping apparatus is that the respective grooves of the first and second dies are formed or otherwise machined such that the respective segments are partially offset from one another. That is, the centerline of the first groove in the first portion of the first die is offset from a centerline of the first groove in the second portion of the first die. Likewise, the centerline of the second groove in the second die is offset in the first and second portions of the second die. When crimping an electrical connector around an elongated conducting component, such as a shape memory material wire, the compound cross-sectional shape of the die cavity will be imparted to the crimped material (i.e., the electrical connector and the elongated conducting component) so that the crimped material will have a compound cross-sectional shape with partially offset segments, and will also be deformed with the offset segments. As used herein, “partially offset” means that the respective centerlines of the respective segments are not collinear, but the segments form a continuous cavity. The offset could be vertical or lateral. 
     The crimping apparatus preferably has an alignment feature that aligns the first and second dies as they are brought together so that the first and second grooves are directly opposite one another to form the die cavity with the multi-segmented compound cross-sectional shape. The alignment feature may be a notch in the first portion of one of the dies that is received in a recess in the first portion of the other die. The die that has the notch in one portion may have a recess in the other portion that aligns with a notch in the opposing portion of the other die. 
     Preferably, the die pair offers numerous aligned grooves forming alternate die cavities each with a compound cross-sectional shape and with the grooves having different depths such that the alternate die cavities have reduced compound cross-sectional shapes that may be selected for crimping smaller size objects. 
     The crimping apparatus preferably includes a fixture that secures the work-piece during crimping. Specifically, the fixture has recesses spaced a predetermined distance from one another. Each recess is sufficiently sized to receive the aligned die pair. Additionally, the fixture is configured to support the work-piece when the work-piece spans across the spaced recesses. Thus, the dies are able to crimp the work-piece at two locations spaced apart by the predetermined distance. 
     Optionally, the fixture may include an adjustment mechanism that permits the predetermined distance to be varied so that work-pieces of different lengths may be crimped. 
     A method of crimping two components of a work-piece to one another is further provided. The components may be a first component that is an elongated wire and a second component that is an electrical connector. The method includes coating a surface of the first component with an adhesive. The first component is then inserted into the second component and the second component is then crimped to the inserted first component with the tool that has the die cavity characterized by a compound cross-sectional shape. As used herein, “compound cross-sectional shape” means a shape that has first and second portions that are asymmetrical. 
     The method preferably further includes securing the work-piece to a fixture that has spaced supports for supporting a different second component near each end of the first component with predetermined spacing therebetween. The effective length of the first component is thereby regulated as the crimped second components at either end thereof are located according to the predetermined spacing. As used herein, “effective length” means the length of the first component (e.g., the elongated conducting component) between the two second components crimped thereto. 
     Preferably, the dies used in the method are configured to define multiple different sized compound cross-sectional die cavities. The method may then include selecting one of the cavities based on the size of the second component prior to crimping. 
     The above features and advantages and other features and advantages of the present invention are readily apparent from the following detailed description of the best modes for carrying out the invention when taken in connection with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic perspective illustration in exploded view of a die; 
         FIG. 2  is a schematic perspective illustration of the a die pair including the die of  FIG. 1  and a mating, lower die; 
         FIG. 3  is a schematic fragmentary top view of the lower die of  FIG. 2 ; 
         FIG. 4  is a partially fragmentary, schematic side view of the die pair of  FIG. 2  in a closed, crimping position; 
         FIG. 5  is a schematic, perspective fragmentary view of a work-piece including an electrical connector and an elongated conductor component prior to crimping of the electrical connector; 
         FIG. 6  is a schematic, perspective fragmentary view of the work-piece including an electrical connector and an elongated conductor component of  FIG. 5  after being crimped by the die pair of  FIG. 2 ; 
         FIG. 7  is a schematic perspective illustration of a fixture used to support the work-piece of  FIGS. 5 and 6 ; 
         FIG. 8  is an end view of another first and second die forming a die pair with a multi-segmented, compound cross-sectional die cavity with vertically offset segments; 
         FIG. 9  is a side view of portions of the first and the second die of  FIG. 8 ; and 
         FIG. 10  is a side view of other portions of the first and second die of  FIG. 8 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to the drawings wherein like reference numbers refer to like components, in  FIG. 1 , a first die  10 , which may also be referred to as an upper die, is shown in an exploded form with a first portion or die half  12  and a second portion or die half  14  configured to be connected side by side with one another as shown in  FIG. 2  by inserting pin  16  through aligned pin holes  18  (only one pin hole is visible on die portion  14 ). An opening  20  in die portion  12  aligns with a like opening (not visible in die portion  14  in  FIG. 1 ) for receiving a tool handle (not shown) therethrough, as will be understood by those skilled in the art), to form a pair of crimping pliers. 
     Referring to  FIG. 2 , the first die  10  is aligned with a second die  22  to form a die pair  10 ,  22 . The second die  22 , also referred to as a lower die, includes a first portion  26  and a second portion  28 . As will be discussed hereinafter, it is apparent from  FIGS. 1 and 2 , that the lower die  22  is essentially identical to the upper die  10  and is a duplicate component thereof. Each aligned pair of portions of the dies  10 ,  22  includes an alignment feature  30  consisting of a notch in one portion (i.e., notches  32 A and  32 B) matable with a recess in the opposed portion (i.e., recesses  34 A and  34 B). The lower die  22  also includes an opening  20  for the tool handle as well as opening  18  to receive connecting pin  16  therethrough to form a crimping apparatus  24 . 
     The lower die  22  is formed with a series of spaced, multi-segmented grooves  40 A,  42 A and  44 A. Each groove includes multiple segments. For example, groove  40 A includes a first segment  46 A in the first portion  26  and a second segment  48 A in the second portion  28 . Segment  46 A has a triangular cross-sectional shape while segment  48 A has a rectangular cross-sectional shape. Grooves  42 A and  44 A each also have multiple segments, including first segments  46 B and  46 C and second segments  48 B and  48 C, respectively. Groove segments  46 B and  46 C have triangular cross-sectional shapes, and groove segments  48 B and  48 C have rectangular cross-sectional shapes. 
     The upper die  10  also has a series of spaced multi-segmented grooves  40 B,  42 B and  44 B. As better viewed in  FIG. 1 , groove  40 B has two segments  48 D and  46 D, groove  42 B has two segments  48 E and  46 E and groove  44 B has two segments  48 F and  46 F. The first segments  48 D,  48 E and  48 F on portion  12  have a rectangular cross-sectional shape while the second portions  46 D,  46 E and  46 F on portion  14  have a triangular cross-sectional shape. 
     As is apparent in  FIG. 2 , the rectangular cross-sectional shape groove segments  40 B,  42 B and  44 B of portion  12  are aligned with the triangular cross-sectional shape groove segments  40 A,  42 A and  44 A of portion  26  while the triangular cross-sectional shape groove segment  46 D,  46 E and  46 F of portion  14  align with the rectangular cross-sectional shape groove segments  48 A,  48 B and  48 C of portion  28  (see also  FIG. 1 ). Thus, when the dies  10  and  22  are brought together for crimping, the groove segments with the rectangular cross-sectional shape are located diagonally from one another while the groove segments with the triangular cross-sectional shape are located diagonally from one another in the multi-segmented grooves formed. It should be appreciated that the dies may have groove segments that each have a different cross-sectional shape, in which case groove segments located diagonally from one another would not be similar. 
     Referring to  FIG. 3 , a fragmented top view of die portion  22  with portions  26  and  28  connected is illustrated. The triangular cross-sectional shaped groove segments  46 A,  46 B and  46 C are offset from their corresponding rectangular cross-sectional shaped groove segments  48 A,  48 B and  48 C, respectively. That is, a centerline of the groove segment  46 A is laterally offset from a centerline of groove segment  48 A, a centerline of groove segment  46 B is laterally offset from a centerline of groove segment  48 B and a centerline of groove segment  46 C is laterally offset from a centerline of groove segment  48 C. Thus, the respective segments of each multi-segmented groove  40 A,  42 A and  44 A are slightly offset from one another. A small gap  27  runs between the respective segments  46 A,  48 A;  46 B,  48 B; and  46 C,  48 C. The offset nature of the groove segments helps to strengthen a bond between crimped components, as will be explained further below. 
     Referring to  FIG. 4 , when the die  10  is aligned with the die  22  via the alignment feature  30 , the respective grooves  40 A,  42 A, and  44 A of the portion  26  and respective grooves  40 B,  42 B, and  44 B of portion  12  are aligned to form die cavities  50 A,  50 B, and  50 C, respectively, each having a multi-segmented, compound cross-sectional shape.  FIG. 4  illustrates the effect of the offset nature of the groove segments on the resulting compound multi-segmented die cavities  50 A,  50 B and  50 C. Additionally, it is apparent from  FIG. 4  that the compound cross-sectional shape of the segments of the die cavities  50 A,  50 B and  50 C formed by the first portions  12  and  26  are rotated with respect to the compound cross-sectional shape of the die cavities  50 A,  50 B and  50 C formed by the die portions  14  and  28 , as is visible from the outline of the perimeter of the die cavity in those segments. Specifically, the cross-sectional shape of the die cavities formed by the segments of the grooves  40 A,  42 A and  44 A (formed by portions  12  and  26 ) are rotated 180 degrees with respect to the die cavities formed with the segments of the grooves  40 A,  42 A,  44 A (formed by the portions  14  and  28 ). It should be appreciated that such diagonal symmetry is not required and that, in other embodiments, groove segments positioned diagonally from one another may have different cross-sectional shapes. 
     The grooves  40 A,  42 A and  44 A are different respective depths as are the grooves  40 B,  42 B and  44 B. As is best illustrated in  FIG. 4 , groove  40 A has a depth D 1  while groove  42 A has a lesser depth D 2  and groove  44 A has an even lesser depth D 3 . The respective depths of the grooves  40 B,  42 B and  44 B in the die  10  are successively decreasing as well. Thus, the die cavity  50 C will have a reduced compound cross-sectional shape as compared to die cavity  50 B, which in turn will have a reduced compound cross-sectional shape as compared to die cavity  50 A. As used herein, a “reduced compound cross-sectional shape” refers to the area of the cross-section of the groove. The differently-sized compound cross-sectional shapes offered by the series of die cavities  50 A,  50 B and  50 C allows a variety of differently-sized work-pieces to be crimped using the same crimping apparatus  24 . 
     Referring to  FIG. 5 , a work-piece  60  includes an electrical connector  62  (also referred to as an electrical terminal) that may be crimped to an elongated conducting component  64  using the crimping apparatus  24 . Work-piece  60  is shown prior to crimping. As is understood by those skilled in the art, an electrical connector such as electrical connector  62  completes the circuit between an incoming electrical component (not shown) and another electrical component such as elongated conducting component  64 . Preferably, elongated conducting component  64  is a shape memory alloy such as NITINOL. NITINOL (an acronym for NIckel TItanium Naval Ordnance Laboratory) is a family of intermetallic materials that contain a substantially equal mixture of nickel and titanium. Other elements may be added to vary the material properties. The work-piece  60  is prepared for crimping by coating a surface  66  of the conducting component  64  with an adhesive and inserting a portion of the elongated component  64  with the coated surface into an opening  61  in a neck portion  65  of the electrical connector  62 . An opposite end (not shown) of the elongated conducting component  64  is prepared in the same way and is inserted into a separate electrical connector, which may be identical to the electrical connector  62 . The electrical connector  62  has a groove  69  therearound. A flexible retaining ring (visible in  FIG. 7 ) may be placed in the groove for locating the electrical connectors  62  by abutting the supports  76 A and  76 B. 
     Referring to  FIG. 7 , the apparatus  24  may further include a fixture  70  on which the work-piece  60  may be supported and secured prior to crimping. The fixture  70  includes a base  72  having spaced recesses  74 A and  74 B. Supports  76 A and  76 B are secured to the base  72  at the respective recesses  74 A and  74 B. Extensions  73  are used for securing supports  76 A and  76 B to the base  72 . After the work-piece  60  is prepared as described with respect to  FIG. 5 , the connector portion  62  at either end thereof is supported at the respective supports  76 A and  76 B. A groove  78  formed in an upper face of the base  72  is designed to receive the elongated conducting component  64 . End supports  80 A and  80 B are secured at the respective connector portions  62  with thumbscrews  82 A and  82 B. A series of cover plates  84 A,  84 B,  84 C and  84 D are secured with additional thumbscrews  82 C,  82 D,  82 E and  82 F to hold down the elongated conducting component  64  and stabilize the work-piece  60  with respect to the base  72 . When the work-piece  60  is secured to the fixture  70  in this manner, the work-piece  60  spans the recesses  74 A and  74 B. The neck portion  65  of each electrical connector is thus stabilized over the respective recess. 
     The recesses  74 A and  74 B are located at a predetermined distance L from one another. Preferably, the predetermined spacing and distance L is variable by providing an adjustment mechanism  90  within the fixture  70 . The adjustment mechanism  90  includes a translatable portion  75  of the base  72  formed with a series of fastener openings  77 A,  77 B and  77 C that may be aligned with respect to a threaded opening  79  in a fixed portion  81  of the base  72  to receive a threaded fastener  83 . By aligning different ones of the fastener openings  77 A,  77 B and  77 C with the threaded opening  79 , the translatable portion  75  moves with respect to the fixed portion  81  of the base  72 . This permits different alternate work-pieces with different overall lengths to be supported on the fixture  70 . Notably, the recesses  74 A and  74 B have a width W 1  that is greater than an overall width W 2  of the die pair  10 ,  22  (see  FIG. 2 ). Thus, recesses  74 A and  74  are sized to receive the die pair  10 ,  22  for crimping the neck  65  of each respective electrical connector  62  on the work-piece  60 . The width of recess  74 A is at a minimum W 1  but may be enlarged by translating the translatable portion  75  as described above. Those skilled in the art will recognize that many other types of adjustment mechanisms may be used to vary the predetermined spacing and distance L; the adjustment mechanism  90  is just one example of such a mechanism. For example, a screw-type positioning system may be used to vary the position of the translatable portion  75  with respect to the fixed portion  81  of the base  72  by tightening or loosening a screw that connects the translatable portion  75  with the fixed portion  81  and controls the relative positions thereof. 
     Once the work-piece  60  is prepared as described with respect to  FIG. 5  and secured to the fixture  70  as described above, an appropriately sized die cavity  50 A,  50 B,  50 C (see  FIG. 4 ) may be selected for crimping based on the size of the electrical connector  62 . The die pair  10 ,  22  (connected to a tool handle (not shown)) is positioned around the neck portion  65  of the electrical connector  62  and then are moved together to crimp the neck  65  with the selected compound cross-sectional area multi-segmented die cavity. 
     Referring to  FIG. 6 , after crimping, the work-piece (referred to as  60 A in  FIG. 6 ) is removed from the fixture  70  with the resulting crimped neck portion, referred to as  65 A in  FIG. 6 , deformed in the shape of the multi-segmented, compound cross-sectional area die cavity selected (either  50 A,  50 B or  50 C). Specifically, the neck portion  65 A will have a compound cross-sectional shape corresponding with the first segment of the die cavity in a first segment  67 A and a compound cross-sectional shape corresponding with the second segment of the die cavity in a second segment  67 B of the neck portion  65 A. Crimping will also cause the inserted elongated conducting component  64  to deform with an offset pair of segments  68 A and  68 B, due to the offset nature of the segments of the grooves described with respect to  FIG. 3 . The electrical connector  62  will deform in an offset manner as well. A multi-segmented, compound cross-sectional crimp applied to connector portion  62  bonds the electrical connector  62  to the elongated conducting component  64  more securely than if a crimping tool with a uniform cross-sectional area were applied. The offset nature of the resulting crimp as well as the multi-segmented compound cross-sectional area prevents the elongated conducting component  64  from slipping out of the electrical connector  62 , as it would be more likely to do, especially when subjected to thermal cycling, often under changing stress, if an electrical connector having a uniform cross-sectional area were used. Even if the electrical connector  62  and/or the elongated conducting component  64  shrink or swell in size repeatedly with thermal cycling, the asymmetrical and offset deformation imparted to these crimped components prevents detachment and also diminishes wear on the adhesive bond placed therebetween. 
     Referring to  FIGS. 8-10 , another embodiment of a crimping apparatus  124  is depicted. The crimping apparatus  124  has many of the same features as the crimping apparatus  24  of  FIGS. 1-4 , as is apparent in  FIGS. 8-10 . The crimping apparatus  124  has a first die  110  and a second die  122 . The first die  110  includes first portion  112  connected to second portion  114 , while the second die  122  includes a respective first portion  126  connected to a respective second portion  128 . 
     The first portions  112  and  126  align to form a series of die cavity segments with a compound cross-sectional shape, each with a different cross-sectional area. Grooves with a rectangular cross-section, such as groove  148 D, are formed in portion  112  while grooves of triangular cross-section, such as groove  146 A, are formed in portion  126 . A centerline C 2  of the resulting die cavity segment is shown in  FIG. 8  (as represented by the interface of the two portions  112 ,  126 , which is at the same height as respective centerlines through each die cavity segment formed by the portions  112 ,  126 ). 
     The second portions  114  and  128  also align to form a series of die cavity segments with a compound cross-sectional shape, each with a different cross-sectional area. Grooves with a rectangular cross-section, such as groove  148 A, are formed in portion  128  while grooves of triangular cross-section, such as groove  146 D, are formed in portion  114 . A centerline C 1  of the resulting die cavity segment is shown in  FIG. 8  (as represented by the interface of the two portions  114 ,  128 , which is at the same height as respective centerlines through each die cavity segment formed by the portions  114 ,  128 ). As illustrated in  FIG. 8 , the centerlines C 1  and C 2  are offset from one another in the direction of the depth of the grooves  146 A,  148 D,  148 A,  146 D, by a distance D. The offset nature of the centerlines C 1  and C 2  may be referred to as “vertically offset”. Thus, each die cavity formed by the die pair  110 ,  122 , including cavity  150 A, is a multi-segmented die cavity of compound cross-sectional shape, with die cavity segments that are vertically offset from one another. The crimped shape imparted to objects crimped together using the crimping apparatus  124  will strengthen the bond between the objects, even if subjected to thermal or stress cycling, especially because the crimping force applied to the die pair  110 ,  122  (i.e., an inward-directed force) is in the same direction or plane as the vertical offset D. 
     While the best modes for carrying out the invention have been described in detail, those familiar with the art to which this invention relates will recognize various alternative designs and embodiments for practicing the invention within the scope of the appended claims.