Abstract:
A clinching tool is provided. A further aspect of the present application locates an anvil and/or movable die members closer to one lateral outside surface of a die body than the opposite lateral outside surface. In another aspect, an offset clinch die and pneumatic tool are employed. Another aspect includes a die body having an anvil and two linearly movable die members which essentially surround a lateral outside surface of the anvil when in inward positions.

Description:
BACKGROUND AND SUMMARY 
     The present invention relates generally to metal working and more particularly to a clinching tool. 
     It is well known to join sheet metal workpieces together by way of a clinch joint. Such a clinch joint is formed by a punch and die deforming workpieces in an interlocking manner. Exemplary clinch joints and tooling are disclosed in the following U.S. Patents and Patent Publication Nos.: 2006/0196034 entitled “Sheet Fastening Apparatus and Method;” U.S. Pat. No. 7,003,861 entitled “Tool Assembly Employing a Flexible Retainer;” U.S. Pat. No. 6,092,270 entitled “Die for Forming a Joint;” and U.S. Pat. No. 5,435,049 entitled “Apparatus for Joining Sheet Material;” all of which were invented or co-invented by the inventor of the present application and are incorporated by reference herein. 
     Various actuators have been used to advance punches relative to clinching dies. One such conventional actuator is a pneumatically powered motor, disclosed in U.S. Pat. No. 3,730,044 entitled “Fluid Operated Apparatus” which issued to Sawdon on May 1, 1973, and is incorporated by reference herein. Furthermore, there has been a desire to reduce the width of workpiece flanges in order to save material costs, weight and space. Such a reduced width flange, however, makes fastening the workpieces together at the flange much more difficult given the size and function of traditional clinching tools. 
     In accordance with the present invention, a clinching tool is provided. A further aspect of the present application locates an anvil and/or movable die members closer to one lateral outside surface of a die body than the opposite lateral outside surface. In another aspect, a tool is employed which can create a clinch joint on a narrow width workpiece flange. In yet another aspect, an offset clinch die and pneumatic tool are employed. Another aspect of the present application includes a die body having an anvil and two linearly movable die members which essentially surround a lateral outside surface of the anvil when in inward positions. A method of clinching is also disclosed. 
     The present invention is advantageous over prior constructions since the present clinching tool is capable of creating a clinch joint on a much narrower width workpiece flange. Furthermore, the present clinching tool is advantageously robust, durable and protects the internal moving parts within a die body. The present clinching tool is also less complex than various traditional constructions and is thereby relatively simple to disassemble for maintenance and cleaning. Moreover, the specific die blade and die body shapes used with various aspects of the present clinching tool advantageously deter die blade rotation, misalignment and binding during clinching yet provide interlocking engagement between the die blades, anvil and die body. Additional advantages and features of the present invention will become apparent from the following description and appended claims, taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view showing a clinch gun of a clinching tool; 
         FIG. 2  is a side elevational view showing the clinch gun of  FIG. 1 , but with an outside plate removed; 
         FIG. 3  is a side elevational view showing workpieces joined by a clinch joint employing the clinching tool; 
         FIG. 4  is an exploded perspective view showing a preferred embodiment of a die assembly employed in the clinching tool; 
         FIG. 5  is a perspective view showing the preferred embodiment die assembly; 
         FIG. 6  is a side elevational view showing the preferred embodiment die assembly; 
         FIG. 7  is a workpiece-accessible, top elevational view showing the preferred embodiment die assembly; 
         FIG. 8  is a side elevational view, like that of  FIG. 6 , showing a die body employed in the clinching tool; 
         FIG. 9  is a cross sectional view, taken along line  9 - 9  of  FIG. 8 , showing the preferred embodiment die body; 
         FIG. 10  is a top elevational view showing a preferred embodiment die blade employed in the clinching tool; 
         FIG. 11  is an end elevational view showing the preferred embodiment die blade; 
         FIG. 12  is an exploded perspective view showing an alternate embodiment die assembly employed in the clinching tool; 
         FIG. 13  is a perspective view showing the alternate embodiment die assembly; 
         FIG. 14  is a workpiece-accessible, top elevational view showing the alternate embodiment die assembly; 
         FIG. 15  is a fragmentary and enlarged view, taken within circle  15  of  FIG. 2 , showing a punch located in a retracted position relative to the preferred embodiment die assembly employed in the clinching tool; 
         FIG. 16  is a fragmentary and enlarged view, like that of  FIG. 15 , but showing the punch in an advanced and clinching position relative to the preferred embodiment die assembly; and 
         FIGS. 17   a - 17   c  are a series of fragmentary views showing the clinching tool and workpieces in various states of clinch forming. 
     
    
    
     DETAILED DESCRIPTION 
     The preferred embodiment of a clinching tool  21  of the present application is shown in  FIGS. 1 ,  2 ,  3 ,  15  and  16 . Clinching tool  21  includes a hand-held clinch gun  23 , a punch  25 , a stripper  27  and a die assembly  29 . Two or more sheet metal workpieces  31  each have a nominal planar surface  33  and an offset angled flange  35 . Clinching tool  21  operably forms a leakproof, clinched joint  37  at the flange of the workpieces  31  as will be further discussed hereinafter. 
     Clinching gun  23  includes an aluminum body  41  having an internally machined chamber  43  within which rotates a cast piston  45 . Elastomeric seals  47  encircle piston  45  and seal against outer plates  49  screwed onto body  41 . Movement of piston  45  serves to rotate a link  51  pivotally attached to a middle thereof. Link  51  is further pivotally coupled to a linearly moving ram  53  and ram  53 , in turn, linearly drives punch  25 . Ram  53  also drives stripper  27  by way of a compression spring  55 . Pneumatic pressure advances and retracts piston  45 . Handles  57  and  59  are also mounted to body  41  to allow for manual positioning of the clinch gun relative to the workpieces. It should be appreciated, however, that clinch gun  23  may alternately be a stationary part of a statically mounted machine or attached to the end of a movable robotic arm. 
     Referring to  FIGS. 4-8 , die assembly  29  includes a generally rectangular parallelepiped-shaped die body  61 , an anvil  63 , a pair of die blades  65 , blade retainers  67  and compression springs  69 . Dowels, bolts, set screws or other fasteners are used to mount the die assembly onto the clinch gun by way of countersunk holes  71  or the like. Die body  61  has a cavity  73  with a laterally elongated and generally semi-circular first branch. A circular groove  75  is machined into cavity  73  adjacent each outboard lateral end. Furthermore, a recess  77  is machined into the internal sides of cavity  73  immediately outboard of each groove  75 . Each blade retainer  67  is inserted into its corresponding groove  75  and then moved into its associated recess  77  when assembled. Additionally, a second branch  79  of cavity  73  is internally machined in die body  67  so as to intersect a middle of the laterally extending branch. 
     Cylindrically-shaped anvil  63  is stationarily mounted within second branch  79  of cavity  73 . The height of a workpiece engaging surface  81  of anvil  63  may vary relative to a workpiece-accessible top surface  83  of die body  61  depending on the workpiece material type, thickness and number of workpieces employed. A set screw, dowel, roll pin or the like may optionally be used to secure anvil  63  within die body  61 . A knock out hole coaxially extends from second branch  79  to allow for removal of anvil  63  from die body  61 . Die body is preferably machined from 4150 steel. 
       FIGS. 4-7 ,  10  and  11  show further details of each blade  65 . Each die blade  65  has a generally flat workpiece-contacting top surface  91 , and a cavity-engaging side and bottom surface  93  defining a slightly greater than semi-circular shape. Furthermore, each die blade  65  has a generally semi-circular anvil-engaging end  95  and an opposite generally flat end  97  with a cylindrical bore  99  machined therein. A portion of compression spring  69  is received within bore  99 . The surface defining the first branch of cavity  73  of die body  61  is actually slightly greater than a semi-circular shape to match side and bottom surfaces  93  of each die blade  65 , thereby trapping the die blades within the cavity in an interlocking manner yet allowing smooth and non-binding inboard-outboard linear movement of the die blades toward and away from anvil  63 . In other words, each die blade  65  slides in a linear and non-rotational direction. Each die blade is preferably machined from 4150 steel and anvil  63  preferably machined from M2 steel which is heat treated and hardened. 
     As can best be observed in  FIGS. 3 ,  5  and  7 , the preferred embodiment of clinching tool  21  locates anvil  63  and die blades  65  in a laterally offset manner (as viewed from the top) within die body  61 . In other words, anvil  63  and die blades  65  are closer to a first and generally flat outside surface  101  of die body  61  as compared to the opposite outside surface  103 . First surface  101  is operably placed immediately adjacent to nominal planar surface  33  of workpiece  31  during clinching. This allows anvil  63  and die blade  65  to act in concert with the punch to form clinch joint  37  onto a flange that is as small as 6.3-9.9 millimeters in width W, and even more desirably on a flange between 6.3-8 millimeters in width. Thus, the upper land of workpiece-accessible top surface  83  adjacent second surface  103  is at least twice as wide as the co-planar upper land of surface  83  adjacent first surface  101 , thereby providing additional contact area for the workpieces against the die body. It is also noteworthy that top surface  83  extends beyond the adjacent upper surfaces of anvil  63  and die blades  65  such that the anvil, die blades, springs and retainers are all well protected within the die body  61 . 
     An alternate embodiment of a die assembly  129  employed in clinching tool  21  is illustrated in  FIGS. 12-14 . This alternate embodiment die assembly  129  includes a die body  161 , anvil  163 , die blades  165 , blade retainers  167  and compression springs  169 , much like that of the preferred embodiment. With this alternate embodiment, however, anvil  163  and die blades  165  are centered between opposite flat outside surfaces  201  and  203  of die body  161 . Thus, the workpiece supporting lands upon top surface  183  of die body  161  are generally of equal width, yet small enough to accommodate the preferred small flange widths of the workpieces. This equal land width allows for reversible positioning when attaching the die assembly to the clinching tool. 
     The clinching operation will now be discussed with regard to  FIGS. 15-17   c . Workpieces  31  and clinching tool  21  are positioned relative to each other such that the workpiece flange is inserted between the spaced apart punch  25  and die assembly  29  (see  FIGS. 15 and 17   a ). Punch  25  is then linearly advanced toward anvil  63  while workpieces  31  rest against the top surface  83  of die body  61 . An end of punch  25  thereafter pushes the adjacent surface of workpieces  31  thereby deforming them into the space between ends  95  of die blade  65  before contact with anvil  63  (see  FIG. 17   b ). Punch  25  continues advancing and then compresses workpieces  31  against an opposing top end of anvil  63 . This causes radially outward expansion and interlocking of the workpieces between die blades  65  while die blades  65  are laterally and strictly linearly moved away from the adjacent lateral surfaces of anvil  63 . This movement compresses die blade  65  against springs  69  (see  FIGS. 16 and 17   c ). Accordingly, the interlocked and cup-shaped button of a leakproof, clinch joint  37  is thereby formed by clinching tool  21 . 
     Adjusting the size of the clinched joint head or “BD” button diameter is determined by the penetration depth of punch  25 . This is accomplished by using various length punches until the desired button diameter is reached. The length of anvil  63  will be chosen according to the metal thickness combination to be joined. Stripper  27  thereafter acts to hold the clinched and fastened workpieces  31  while punch  25  is retracted. Then, workpieces  31  are removed from die assembly  29  and springs  69  are allowed to urge die blade  65  back toward anvil  63 . 
     While various embodiments of the present invention have been disclosed, it should be appreciated that other modifications are possible. For example, alternate actuators for the punch may be employed although various advantages of the present application may not be realized. Furthermore, alternate springs or other biasing devices can be used to achieve the same function disclosed hereinabove although various advantages may not be realized. It is also envisioned to employ differing shaped die blades and die bodies although many advantageous aspects of the present application may not be achieved. Use of the clinching tool on offset workpiece flanges is the most advantageous use, however, other workpiece joint configurations can be employed. Moreover, the references hereinabove to “top,” “side,” “bottom,” “end,” “first” and “second” are merely relative and nonlimiting terms since the referenced parts may be reoriented depending upon the specific utilization. Finally, while various materials and manufacturing processes have been disclosed, it should be appreciated that alternate materials and manufacturing processes may be used. It is intended by the following claims to cover these and any other departures from the disclosed embodiments which fall within the true spirit of this invention.