Abstract:
A clinch punch including a core and an sleeve that includes a plurality of teeth for forming an enhanced clinch joint. The core includes a first cam surface that engages cam surfaces on the teeth that drive the teeth into the sides of the clinch joint. In an alternative embodiment, the core acts upon jaws that are driven into engagement with the sides of the clinch joint.

Description:
TECHNICAL FIELD 
       [0001]    The technical field of this disclosure is punches used to form clinch joints in sheet metal parts. 
       BACKGROUND 
       [0002]    Assembly operations for joining aluminum parts and mixed metal parts are being developed to maximize the use of lightweight parts and improve fuel economy. Currently, self-piercing rivets are used to join aluminum and mixed metal part assemblies because they can provide a strong joint between adjacent parts. Self-piercing rivets add weight to the assembly and also add cost that is added to the final product. 
         [0003]    Clinch joints are used in some applications but are not as strong as self-piercing rivet joints, particularly in the coach peel orientation. Clinch joints are lighter weight and less expensive than self-piercing rivet joints because they do not require a rivet Clinch joints are not as strong or robust as self-piercing rivets because they are limited by the extent of mechanical interlock that can be achieved between the joined panels. 
         [0004]    The above problems and challenges and others are addressed by this disclosure as summarized below. 
       SUMMARY 
       [0005]    This disclosure provides a new clinch joint punch and a new method of forming a clinch joint that increases the extent of mechanical interlock for clinch joints. Increasing the mechanical interlock results in higher joint strength. The total number of clinch joints in an assembly having multiple clinch joints may be reduced because the strength of each clinch joint is increased. 
         [0006]    According to one aspect of this disclosure, a clinch punch is disclosed for joining multiple panels with a clinch joint. The punch comprises a core having a first cam surface and an sleeve defining an opening. The sleeve has a plurality of teeth that each includes a second cam surface. An actuator drives the core and sleeve into a plurality of panels. The core is moved within the sleeve by the actuator with the first cam surface engaging the second cam surfaces to move the teeth outwardly to join the panels together. 
         [0007]    According to other aspects of the punch, a spring may operatively engage the core and the sleeve to bias the core away from the panels and disengage the first cam surface from the second cam surfaces to move the teeth inwardly to retract the punch from the panels. The core may have a head on a first end that is engaged by the actuator and the spring may be disposed between the sleeve and the head with the spring being compressed as the teeth are moved outwardly and expanded as the teeth are moved inwardly. 
         [0008]    The core may be a cylindrical member having a leading end that includes a partially conical surface and the second cam surfaces on the teeth may each have a contact surface that is disposed at a complementary angle to the first cam surface. 
         [0009]    Alternatively, the sleeve may include a plurality of separate jaws that are retained on the core by a connector that secures the jaws to the core. The connector may be attached to the core with a lost motion connection that allows the core to move to a limited extent relative to the jaws. The connector may be a fastener and the jaws may each define an opening that receives the fastener and the core may define a slot that is elongated in a direction that the core is moved by the actuator. 
         [0010]    The punch may further comprise a spring operatively engaging the jaws to bias the jaws toward the core, and wherein the jaws are driven apart by the first cam surface engaging the second cam surfaces. The spring may be a first spring attached to a first end of the fastener and a second spring attached to a second end of the fastener. The first and second springs bias the teeth toward the core with the first cam surface engaging the second cam surface to move the teeth away from the core. 
         [0011]    According to another aspect of this disclosure a method is disclosed for forming a clinch joint in a plurality of panels. The method comprises driving a punch assembly including a core and an sleeve having a plurality of teeth into the panels to form a depression in the panels. The teeth are shifted outwardly within the depression in the panels to mechanically interlock the panels. 
         [0012]    According to other aspects of the method, the core may have a first cam surface and the sleeve may have a second cam surface and the method may further comprise engaging the first cam surface and the second cam surface to shift the teeth outwardly. The sleeve may further comprise a sleeve and the teeth may be projections that extend in a longitudinal direction from the sleeve. The second cam surface may further comprise a plurality of second cam surfaces that are each provided on one of the teeth. 
         [0013]    According to an alternative embodiment of the method, the sleeve may further comprise a plurality of jaws that each includes at least one of the plurality of teeth and one of the second cam surfaces. 
         [0014]    The method may further comprise shifting the teeth inwardly after mechanically interlocking the panels, and retracting the punch assembly from the depression in the panels. The core may have a first cam surface and the sleeve may have a second cam surface. The method may further comprise engaging the first cam surface and the second cam surface to shift the teeth outwardly, and withdrawing the first cam surface from the second cam surface to shift the teeth inwardly. 
         [0015]    The above aspects of this disclosure and other aspects are described in greater detail below with reference to the attached drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]      FIG. 1  is a fragmentary cross section view of a prior art clinch joint. 
           [0017]      FIG. 2  is an exploded perspective view of a clinch joint punch made according to one exemplary embodiment of this disclosure. 
           [0018]      FIG. 3  is a cross section view taken along the line  3 - 3  in  FIG. 2 . 
           [0019]      FIG. 4  is a fragmentary cross section view of the clinch joint punch of  FIG. 2  illustrating the punch in a first phase of the clinching operation. 
           [0020]      FIG. 5  is a fragmentary cross section view of the clinch joint punch of  FIG. 2  illustrating the punch in a second phase of the clinching operation. 
           [0021]      FIG. 6  is an exploded perspective view of the clinch joint punch of  FIG. 5   
           [0022]      FIG. 7  is a fragmentary cross section view of an alternative embodiment of a clinch joint punch. 
       
    
    
     DETAILED DESCRIPTION 
       [0023]    A detailed description of the illustrated embodiments of the present invention is provided below. The disclosed embodiments are examples of the invention that may be embodied in various and alternative forms. The figures are not necessarily to scale. Some features may be exaggerated or minimized to show details of particular components. The specific structural and functional details disclosed in this application are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art how to practice the invention. 
         [0024]    Referring to  FIG. 1 , a clinch joint  10  is shown joining a top panel  12  to a bottom panel  14 . The references to top and bottom correspond to the orientation of the panels as illustrated in  FIG. 1  and should not be used to interpret the orientation of the clinch joint  10  which may be used to join panels that are in any directional orientation. A mechanical interlock  16  secures the top panel  12  to the bottom panel  14 . 
         [0025]    Referring to  FIG. 2 , a clinch punch assembly  20  is shown to include a core  22  that is received in an sleeve  24 , or outer member, and a spring  26 , or biasing device. A head  28  is provided on the core  22 . The head  28  receives an actuation force, as will be described in greater detail with reference to  FIGS. 4 and 5  below. 
         [0026]    The head  28  is provided on an inner end  30  of the core  22 . The inner end  30  is received and retained in a clinch joint tool (not shown). A cam surface  32  that is a frusto-conical surface is provided at a distal end  34  of the core  22 . 
         [0027]    The sleeve  24  includes a plurality of fingers  36  that are provided at a leading end  38  of the sleeve  24 . A plurality of cam surfaces  40  are provided on each of the fingers  36 . The cam surfaces  40  are disposed at a complementary angle to the cam surface  32  of the core  22 . Forming surfaces  42  are provided on an outer surface of the fingers  36 . The forming surfaces  42  engage the clinch joint  10  in the final stages of forming the clinch joint. 
         [0028]    Referring to  FIG. 3 , the sleeve  24  is shown in cross section with the finger  36  partially in phantom to show the fingers in a retracted and an expanded position. The fingers  36  include cam surfaces  40  that are visible within the inner diameter of the sleeve  24 . When the cam surface  32  of the core  22  engages the cam surfaces  40 , the forming surfaces  42  on the fingers  36  are driven outwardly in the direction indicated by expansion arrows A 2 . 
         [0029]    Referring to  FIGS. 4 and 5 , the clinch punch assembly  20  is shown in  FIG. 4  in a first stage of the forming process. As shown in  FIG. 5 , the clinch punch assembly is shown in a second phase in which the mechanical interlock between the top panel  12  and the bottom panel  14  is illustrated. 
         [0030]    Referring to  FIG. 4 , an actuation arrow A 1  is shown to represent the force applied to the head  28  of the core  22 . The core is driven downwardly, as shown in  FIG. 4 , to force the cam surface  32  into engagement with the cam surfaces  40  provided on the fingers  36 . The forming surfaces  42 , as shown in  FIG. 4 , are in the retracted position. 
         [0031]    Referring to  FIG. 5 , the actuation force arrow A 1  is shown after the core  22  is driven into engagement with the fingers  36 . The cam surface  32  is driven across the cam surfaces  40  to force the forming surfaces  42  into the top panel  12  to create an enhanced interlock, as shown by the circle  46 . The top panel  12  is driven sideways into the bottom panel  14  by the forming surfaces  42 . After completion of the enhanced interlock phase shown in  FIG. 5 , the spring  26  biases the core  22  in an upward direction to provide a return force upon completion of forming the clinch joint. The spring  26  withdraws the core  22  back into the sleeve  24  in the direction opposite arrow A 1 . 
         [0032]    Referring to  FIG. 6 , an alternative clinch punch assembly  50  is shown in an exploded perspective view. The clinch punch assembly  50  includes a core  52  that is received between a first jaw  54  and a second jaw  56 . A threaded shaft  58 , or fastener, is assembled with a first spring  60  on an outer side of the first jaw  54  and a second spring  62  received on the threaded shaft  58  on the outer side of the second jaw  56 . Nuts  64  retain the springs  60 ,  62  on the threaded shaft  58 . The threaded shaft  58  extends through holes  66  formed in the first jaw  54  and second jaw  56 . A slot  70  provides a lost motion connection between the core  52  and the threaded shaft  58 . The threaded shaft  58  is inserted through the holes  66  and slot  70 . The slot  70  provides a lost motion connection so that the core  52  may be moved initially with respect to the first and second jaws  54  and  56 . 
         [0033]    The head  72  of the core  52  receives the actuation force A 1  and drives the core downwardly, as illustrated. A driving cam surface  74  provided on the core  52  engages the driven cam surface  76  that is provided on the first jaw  54  and second jaw  56 . 
         [0034]    Referring to  FIG. 7 , the alternative clinch punch assembly  50  is shown in a first phase of a clinching operation (corresponding to the phase illustrated in  FIG. 4 ) in which the clinch punch assembly  50  is driven into the top panel  12  that is, in turn, driven into the bottom panel  14 . The punch assembly  50  forms a depression  78  in the panels  12 ,  14 . At this point, the threaded shaft  58  is disposed in the lower portion of the slot  70 . As the actuation force continues to be applied to the head  72  of the core  52 , the core  52  moves relative to the threaded shaft  58  until the top of the slot  70  engages the threaded shaft  58 . The driving cam surface  74  engages the driven cam surface  76  to force the jaws apart, as shown by expansion arrows A 2 . The jaws are forced apart against the force of the first and second springs  60  and  62 . When the jaws  54  and  56  are driven in the direction of the expansion arrows A 2 , an enhanced clinch joint is formed that is similar to the clinch joint shown in  FIG. 5  above. The springs  60  and  62  bias the jaws  54  and  56  toward a retracted position to facilitate withdrawing the clinch punch  50  from the clinch joint  10 . 
         [0035]    While two jaws  54  and  56  are shown, it is anticipated that four or more jaws could be provided with suitable modifications of the clinch punch  50 . 
         [0036]    While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms of the disclosure. The words used in the specification are words of description rather than limitation. Changes may be made to the illustrated embodiments without departing from the spirit and scope of the disclosure as claimed. The features of the illustrated embodiments may be combined to form further embodiments of the disclosed concepts.