Patent Publication Number: US-2016236259-A1

Title: Method and Apparatus for Attaching a Nut in a Hydro-Forming Tool

Description:
TECHNICAL FIELD 
     This disclosure is directed to a method and apparatus for punching openings in a tubular part in a hydro-forming tool and installing a nut or other threaded fastener inside the tubular part. 
     BACKGROUND 
     Tubular parts may be formed in a hydro-forming operation performed in a hydro-forming tool. A hydro-formed part may replace multiple conventionally stamped parts in a single part thereby reducing the number of separate parts and process steps required to make an assembly. In addition, hydro-formed parts may provide increased strength and may reduce the weight of a part. 
     One disadvantage of prior art hydro-formed parts is that fasteners, such as nuts and bolts, must be installed after the hydro-forming operation is complete and the tubular part is removed from the hydro-forming tool. Post hydro-forming operations also add to the cycle time for manufacturing a hydro-formed assembly. Post hydro-forming operations add to the capital equipment cost for making an assembly. Increased cycle times and capital equipment costs add to the cost of manufacturing a hydro-formed assembly. 
     In addition, attaching fasteners to a hydro-formed part may be a problem if the fasteners must be assembled to meet close tolerances. The hydro-formed part and fasteners may need to be manipulated multiple times to install a nut on or within a tubular part. Installing a nut inside a tubular part is problematic because of the difficulty in locating, retaining and securing the nut inside the tubular member. 
     This disclosure is directed to solving the above problems and other problems as summarized below. 
     SUMMARY 
     According to one aspect of this disclosure, a method of making a hydro-formed assembly is provided that includes the following steps. In the first step, a first opening is punched in a first wall of a tubular part with an outer punch. In a second step, a nut is clinched to an inner surface of the second wall of the tubular part and a second opening is punched in a second wall of the tubular part with a clinching feature provided on the nut around a bolt receiving opening defined by the nut. 
     According to other aspects of the method, an additional step of hydro-forming the tubular part in a hydro-forming tool is performed before the first opening is punched in the first wall. The method may further comprise loading the nut onto a nut retainer disposed within the outer punch before punching the first opening in the first wall. 
     According to another aspect of this disclosure, a tool for hydro-forming a part is disclosed. The tool comprises a hydro-forming die retained in a hydro-forming tool and a dual action punch operated by the tool. The dual action punch includes an outer punch and a nut retainer disposed inside the outer punch. An annular recess is provided on the die on an opposite side of the part from the dual action punch to facilitate securing the nut to an inner surface of the part. The nut defines a fastener receiving opening and includes a clinching feature disposed around the fastener receiving opening that punches an opening in the part. 
     According to other aspects of this disclosure as it relates to a tool for hydro-forming a part, the outer punch may form a first opening in a first portion of a wall of the part and the clinching feature on the nut forms a second opening in a second portion of the wall of the part that is axially aligned with the first opening. The nut is retained by the nut retainer within the outer punch while the outer punch forms the first opening in the first portion of the wall. The nut retainer secures the nut to the inner surface of the part by clinching the nut to the inner surface. 
     The hydro-form tool and die include an opening through which a slug formed by the clinching feature on the nut is removed from the second opening. The hydro-forming die may also define a relief area around the opening that receives material from the part that is displaced when the nut is clinched to the inner surface of the part. Material from the part is also formed around the clinching feature on the nut to retain the nut on the part. 
     According to another aspect of this disclosure, a punch assembly is disclosed for attaching a nut to a part in a hydro-forming tool. The punch assembly comprises an outer punch for forming a first opening in the part and a nut retainer received within the outer punch for forming a second opening in the part when the nut is attached to the part. The nut has a clinching feature that has a smaller diameter than the outer punch. The receptacle for retaining the nut is coaxially received within the outer punch. 
     According to other aspects of this disclosure as it relates to the punch assembly, the nut retained by the receptacle may be clinched to the part around the second opening. The outer punch may form the first opening in a first portion of the part and the nut may form the second opening in a second portion of the part. The nut is secured to the second portion in alignment with the second opening. The nut retainer is moveable within the outer punch. The outer punch forms the first opening in the part. The nut held by the nut retainer forms the second opening in the part at a location spaced from the first opening with the first punch engaging the part around the second opening as the nut is clinched to the part. 
     The above aspects of this disclosure and other aspects are described below with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a fragmentary cross-section view of a hydro-forming tool including a hydro-forming die showing a tubular part prior to forming a first opening with an outer punch. 
         FIG. 2  is a fragmentary cross-section view of the hydro-forming die showing the tubular part after forming the first opening with the outer punch. 
         FIG. 3  is a fragmentary cross-section view of the hydro-forming die showing the tubular part with the outer punch engaging an inner surface of the tubular part as a nut retainer supporting a nut with a clinching feature forms a second opening in the part. 
         FIG. 4  is a fragmentary cross-section view of the hydro-forming die showing the tubular part after a nut is attached to an inner surface of the tubular part in alignment with the second opening. 
     
    
    
     DETAILED DESCRIPTION 
     The illustrated embodiments are disclosed with reference to the drawings. However, it is to be understood that the disclosed embodiments are intended to be merely examples that may be embodied in various and alternative forms. The figures are not necessarily to scale and some features may be exaggerated or minimized to show details of particular components. The specific structural and functional details disclosed are not to be interpreted as limiting, but as a representative basis for teaching one skilled in the art how to practice the disclosed concepts. 
     Referring to  FIG. 1 , a hydro-forming tool  10  is illustrated in part that is provided with a hydro-forming die  12 . A tubular part  14  is shown disposed within the hydro-forming die  12 . A dual action punch, generally indicated by reference numeral  16 , is shown that is operated by two separate hydraulic cylinders (not shown), or other actuators, that are part of the hydro-forming tool  10 . The dual action punch  16 , as shown in  FIG. 1 , is retracted relative to the hydro-forming die  12  and prior to performing a punching operation on the tubular part  14 . 
     The dual action punch  16  includes an outer punch  18  and a nut retainer  20  that is concentrically received within the outer punch  18 . A nut  26  is retained by the nut retainer  20  and includes a clinching feature  22 . The clinching feature  22  is a part of the nut and includes a cutting edge that functions as a cutting edge to punch a slug from the part to form a second opening as will be described below. The nut  26  is disposed within a cup-shaped recess  28  defined by the outer punch  18 . A shoulder  30  is part of the nut retainer  20  and engages the nut  26 . The shoulder  30  exerts a compressive force on the nut  26  to secure the nut  26  to an inner surface of the tubular part  14  by coining or clinching. 
     The hydro-forming die  12  defines an annular recess, or relief area, at  34 . The relief area  34  receives material displaced when the nut  26  is pressed onto the tubular part to retain the nut  26  on the tubular part  14  inner surface. The hydro-forming die  12  defines a slug removal hole  36 . 
     Referring to  FIG. 2 , the dual action punch  16  is shown after punching a slug  38  that is formed when the first opening  40  is formed in the tubular part  14 . The first opening slug  38  is punched from the tubular part  14  by the outer punch  18 , but is retained on the tubular part  14  by an attachment bridge. The outer punch  18  forms the first opening  40  when forced, as shown by the arrows in  FIG. 2 , into the tubular part  14 . The nut retainer  20  initially moves with the outer punch  18 , as shown in  FIG. 2 . The nut retainer  20  retains the nut  26  within the recess  28  magnetically or with a mechanical retention mechanism (fingers, detents or other holders). 
     Referring to  FIG. 3 , the dual action punch  16  is shown with the outer punch  18  engaging an inner surface of the tubular part  14 . At this point, the nut retainer  20  moves relative to the outer punch  18  in the direction indicated by the upper arrow in  FIG. 3 . The shoulder  30  is shown engaging the nut  26  to drive the nut into the inner surface of the tubular part  14 . The nut retainer  20  is shown after the nut  26  cuts the slug  42  from the second opening  44 . The slug  42  is shown after being removed from the hydro-forming die  12  through the slug removal hole  36  that is defined by the hydro-forming die  12 . 
     Referring to  FIG. 4 , the dual action punch  16  is shown after attaching the nut  26  and being retracted from the tubular part  14 . The dual action punch  16  moves for retraction in the direction indicated by the arrow in  FIG. 4 . The nut  26  is clinched to the inner wall of the tubular part  14  with a portion of the tubular part  14  being displaced into the relief area  34  defined by the hydro-forming die  12 . The first opening slug  38  is retained by the tubular part  14 . The first opening  40  provides access for a bolt or other fastener to be received in the nut  26 . The nut retainer  20 , including the shoulder  30 , is initially retracted within the outer punch  18  as the dual action punch  16  is refracted from the part. At this point, the first opening  40  and second opening  44  have been formed in the tubular part  14  and the nut  26  is clinched or coined into engagement with the inner surface of the tubular part  14 . 
     The nut  26 , first opening  40  and second opening  44  are all coaxially aligned. At this point in the process, the tubular part  14  may be removed from the hydro-forming die  12  as a hydro-formed part assembly  48 . After completion, the process may be repeated by loading another tubular part  14  into the hydro-forming die  12  and loading a new nut  26  into the dual action punch  16 . 
     No post hydro-forming operations are required to assemble the nut to the tubular part  14 . Because the openings  40  and  44  are both punched and the nut  26  is assembled in a single cycle of the dual action punch  16 , close tolerances may be maintained as to the relative location of the holes and the nut. 
     The embodiments described above are specific examples that do not describe all possible forms of the disclosure. The features of the illustrated embodiments may be combined to form further embodiments of the disclosed concepts. The words used in the specification are words of description rather than limitation. The scope of the following claims is broader than the specifically disclosed embodiments and also includes modifications of the illustrated embodiments.