Abstract:
A self-actuating tooling die located beneath an industrial press impact zone clamps a the tongue of an end ring side-to-side to hold it dimensionally stable during a pressing operation that clinches a nut to a hole in the tongue. The tooling die comprises a cone-shaped split collet fitted into a corresponding cone-shaped receptacle in the die housing. As the installation force of the press forces the collet into the receptacle, jaws of the collet grip the tongue a corresponding amount. At a pre-determined point of advancement, the collet bottoms out against a stop in the socket to hold the tongue in its pre-installation relaxed shape and size. A spring-loaded stepped pin, which reciprocates within an axial bore of the die, centers the nut and hole in the tongue during installation and later ejects the completed assembly.

Description:
RELATED APPLICATIONS 
       [0001]    This patent application is a non-provisional of provisional patent application Ser. No. 62/084,725 entitled “Ring Tongue Clamping Die” filed on Nov. 26, 2014 priority from which is hereby claimed. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to punch and die tooling for clinching two or more materials together. More specifically, it relates to self-clamping tooling for clinching a fastener onto the tongue of an electrical end-ring or ring terminal. 
       BACKGROUND OF THE INVENTION 
       [0003]    Rotatable clinch nuts of the type described in U.S. Pat. No. 7,374,382 are widely used for a variety of applications. One application is attachment to the tongue of an electrical end ring. The tongue is the flat extension of the terminal that has a hole for receiving a stud to which the end becomes attached. The use of a rotatable nut to complete the attachment to the stud provides the advantage of limiting the number of loose parts since it remains attached to the cable end. 
         [0004]    Electrical end rings or ring terminals are typically manufactured from relatively soft materials such as aluminum or copper. In many cases, the diameter of the hole in the tongue is relatively large compared to the width of the tongue; therefore, the width of tongue material around the hole is very small. With these conditions displacer-type fasteners, such as rotatable clinch nuts, tend to produce material bulging and dimensional growth of the tongue around the hole during installation. Such distortion can cause poor rotational and performance characteristics of the nut after installation because these unwanted dimensional changes reduce the tongue material retention overlap with the clinch features of the nut. 
         [0005]    Therefore, it would be desirable to provide installation tooling that prevents dimensional changes of the tongue during the installation of fasteners such as rotatable nuts. It would also be desirable to provide installation tooling having means for accurately centering the nut on the receiving hole and preventing over stressing of the tongue. It would be further desirable to provide means for ejecting the tongue from the installation tooling without damage to the part if it becomes stuck. 
       SUMMARY OF THE INVENTION 
       [0006]    According to one embodiment of the invention, self-actuating tooling beneath the press impact zone clamps the tongue of an electrical end ring side-to-side to hold it dimensionally stable during the pressing operation. The tooling die is self-actuating and comprises a cone-shaped split collet fitted into a corresponding cone-shaped socket. As the installation force of the press forces the collet into the receptacle, jaws of the collet move toward the sides of the tongue a corresponding amount. 
         [0007]    At a pre-determined point of advancement, the collet bottoms out against a stop to limit the position of the jaws to that which is necessary to hold the tongue in its pre-installation relaxed shape and size. At that point, the press continues to install a press-fit fastener. A spring-loaded, stepped pin centers the applied nut and later ejects the completed assembly. Another spring returns the collet to its home position after the installation is complete. 
         [0008]    More specifically, the applicant has invented tooling for an industrial press which functions as a self-clamping die to hold a cable end workpiece while a fastener is being pressed into it during an installation stroke of the press. The tooling includes a die which has a tapered receptacle with downwardly convergent sides within which a clamping collet is vertically moveable between an upward-most release position and a downward-most clamping position. The downward-most position is defined by a bottom end wall of the receptacle. The collet has tapered sides converging in the downward direction and includes moveable jaws for laterally clamping the workpiece. The jaws have clamping sides and a base portion for supporting the workpiece against the downward force of the press. 
         [0009]    A first spring is located in the tool receptacle for upwardly biasing the collet to the release position. A vertically-reciprocal, cylindrical ejector pin is located within an axial bore in the die and is biased in the upward direction by an ejector spring. The pin has an annular step around the base of a top end portion of the pin of reduced diameter. The step and the top portion hold a fastener, such as a nut, in alignment with the workpiece. The release position of the tool die is where the collet and the pin are at their upward-most position, biased to that point by the collet and ejector springs. A collar at a top end of the die limits the collet&#39;s upward movement by abutment with a step on the outside wall of the collar at the release position, thereby captivating the collet within the tool socket. The collet has at least two jaws, preferably four, with bases that support the workpiece in opposition to the downward force of the press ram. 
         [0010]    The ejector pin extends upwardly between the jaws and functions to both support and eject the workpiece. The outside diameter of the pin is approximately equal to the hole in the workpiece with minimal clearance to ensure alignment of the nut with the hole. The collet, tool, die, springs and pin are constructed and arranged so that a downward force applied to the fastener and the workpiece by a ram press causes the collet to close about the workpiece due to the clamping position of the collet. While clamped, the collet jaws prevent expansion while the fastener is pressed into attachment with the workpiece. When the downward force of the press ram is withdrawn, the pin moves upward between the collet jaws and ejects the workpiece upward from the collet. 
         [0011]    The present invention has many advantages over the prior art. The tooling in accordance with an embodiment of the invention is simple and self-actuating device because its spring-actuated mechanisms do not rely upon any outside motive force other than the installation force of the press. Other advantages and differences will follow from the foregoing explanation and the following drawings and description of the invention. The preferred embodiment of the invention will provide one of ordinary skill in the art with a full understanding of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1  is a perspective, partial-cutaway view of tooling in accordance with a preferred embodiment of the invention; 
           [0013]      FIG. 2  is cross section of the tooling shown in  FIG. 2 ; right side sectional elevation view; 
           [0014]      FIG. 3 a    a top plan view of an electrical-cable end-ring seated on the tooling of  FIG. 1 ; 
           [0015]      FIG. 3 b    is a cross section taken along lines  3 B- 3 B of  FIG. 3A ; 
           [0016]      FIGS. 4 through 8  are cross sections showing the sequential steps of clinching a fastener to the tongue of an end ring in accordance with a preferred embodiment of the invention; and, 
           [0017]      FIGS. 9 and 10  are fragmentary schematic illustrations (not to scale) of the motion path of the collet in the upper housing socket. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0018]    Tooling in accordance with a preferred embodiment is shown in  FIGS. 1-10 . Due to the scale of the more detailed drawings of  FIGS. 1-8 , small clearances between the collet, stem, and upper housing socket are not discernible. Therefore, the fragmentary, schematic illustrations of  FIGS. 9 and 10 , not drawn to scale, are provided to illustrate said clearances. 
         [0019]    The tooling generally comprises a press ram tool  13  and a self-clamping die  11 . The outer supporting structures of the press are not shown and are not required for a full understanding of the invention by one of ordinary skill in the art. The press ram tool  13  and self-clamping die  11  are constructed and arranged to connect to the ram and anvil, respectively, of conventional press equipment. 
         [0020]      FIGS. 1 and 2  show an electrical end ring  9  seated in the self-clamping die  11 . The end ring  9  includes an end fitting or ferrule  10 , tongue  15  and threaded nut  17  after the nut  17  has been clinched to the tongue  15 . This position of the elements also corresponds to  FIG. 8 , wherein the end ring  9  is fully assembled and ready for removal from the die  11 . The tongue  15  is generally rectangular with a lengthwise dimension extending parallel to the central axis if the ferrule  10 . As described above, the thickness of the tongue  15  is minimized along the lengthwise-extending edge of the tongue  15  adjacent the hole. 
         [0021]    The press ram tool  13  generally comprises a solid cylindrical body  8  having a central, longitudinal axis and a cylindrical socket  12  in one end. The diameter of the socket  12  preferably approximates the outer diameter of the nut  17  or other fastener, which is to be crimped to the tongue  15 . The socket  12  holds the nut  15  in alignment with the hole in the tongue  15  during the installation process as described further below. 
         [0022]    The die  11  includes a cylindrical housing  21  having a central, axial bore  7  in which a cylindrical pin  23  reciprocates. The bore  7  extends from the housing upper end  21   a  to a point near the lower end  21   b  of the housing, but not entirely through the housing  21 . The bore  7  has several different diameters as described below. In use, the central axis of the housing  21  aligns with the central axis of the press ram tool  13 . 
         [0023]    The pin  23  has a central portion  23   b , an enlarged-diameter lower portion  23   c , and a reduced-diameter upper portion  23   a , which has the same diameter as the inside diameter of the nut  17  as best seen in  FIG. 2 . The diameter of the central portion  23   b  of the pin  23  is substantially equal to the inside diameter of the hole in the tongue  15  with an appropriate clearance. 
         [0024]    The die  11  includes a tapered, split collet assembly consisting of four collet segments  18  (hereinafter collectively “the collet  18 ”) that reciprocate within an upper housing socket  16  extending from the upper end  21   a  of the housing. The four cooperating collet segments are symmetrically arranged around the upper end of the central portion  23   b  of the stem  23 . Each segment of the collet  18  has four upper jaws with base portions  20  and teeth  19  that grip the lengthwise-extending sides of the tongue  15  as best seen in  FIGS. 1 and 3 . 
         [0025]    Referring to  9 , the interior side walls  32  of the collet segments are arcuate and compliment the outer diameter of the central portion  23   b  of the stem  23 . Referring to  FIG. 10 , the exterior side walls of the collet are generally cylindrical at the axial upper portion  30   a  and axial lower portion  30   c , both of which preferably have the same diameter. In contrast, the central portion  30   b  of the exterior side walls taper inwardly in the downward direction. In a preferred embodiment, the diameter of the exterior side walls in the central portion  30   b  increases proceeding from the lower portion  30   c  to the upper portion  30   a , thereby forming a shoulder  30   d  at the interface between the central portion  30   b  and the upper portion  30 . The shoulder  30   d  acts as a stop to prevent the collet from being ejected from the upper housing socket  16 . 
         [0026]    The inner walls  31  of the upper housing socket  16  have a shape that generally compliments the exterior side walls  30  of the collet. Referring to  FIG. 10 , the lower portion of the inner walls  31   b  has a generally cylindrical shape with a constant diameter. The upper portion of the inner walls  31   a  tapers outwardly in the upper direction. In other words, the inner diameter of the socket  16  increases proceeding from the interface between the lower/upper portion interface to the upper end of the housing upper end  21   a.    
         [0027]    A first compression spring  27  sits in a first enlarged pocket  7   a  at the bottom of the central bore  7 . The spring  27  abuts the bottom end of the pin  23  and biases the pin  23  upwardly. A second spring  25  surrounds the central portion  23   b  of the pin  23  and sits in a second enlarged pocket  7   b  in the central bore  7  co-extensive with but smaller in diameter than the upper housing socket  16 . The upper end of the second spring  25  contacts the bottom of the collet  18  and biases the collet  18  upwardly. A collar  29  surrounds the upper portion of the housing and has a reduced inner diameter slightly larger than the upper portion  30   a  of the collet  18 . The collar  29  captivates the collet  18  within the housing  21  and limits its upward movement while the bottom wall  26  of the upper housing socket  16  limits the collet&#39;s downward movement. The die housing  21  also includes appropriate stops that limit the range of motion of the pin  23 . 
         [0028]    From  FIGS. 1 and 2  and the above description, it will be apparent to those of skill in the mechanical arts that motion of the pin  23  and collet  18  are separate, and that downward force applied to the top of the collet  18  will cause its jaws  19  to close until the collet reaches the bottom wall  26  of the upper housing socket  16 . 
         [0029]      FIGS. 3 a    through  8  depict the sequential steps of a clinching a fastener to the tongue  15  of an end ring  9  using the tooling described above in accordance with a preferred embodiment of the clinching method of the invention. Front elevation sectional views have been chosen which more clearly show the operation of the collet jaws upon the tongue  15 . The position of the tongue  15  is also shown in the associated plan view of  FIG. 3 a   . Because the various elements of the tooling have been fully described and enumerated above with regard to  FIGS. 1 and 2 , it is unnecessary for a full understanding of the invention&#39;s operation to repeatedly enumerate all of the parts in  FIGS. 3 through 7 , which are identical except for changes in position of some of the components. The numbering of the components corresponds to the numbering shown in  FIGS. 1 and 2 . In practice, although not necessarily illustrated that way, all the dimensions and spring rates are chosen so that the following sequence of operation occurs as described. 
         [0030]    Referring now to  FIGS. 3 a  and 3 b   , the hole in the tongue  15  has been placed over the upper portion  23   a  of the pin  23 . The tongue  15  sits on the base portion  20  of the jaws in between the teeth  19 . Next, the nut  17  is placed over the upper portion  23   a  of the pin  23  and sits on the shoulder between the upper portion  23   a  and the central portion  23   b . At the same time, the hole snugly surrounds the very end of the central portion  23   b . These mechanical arrangements ensure alignment of the nut  17  and the hole in the tongue  15  during the installation process. 
         [0031]    Referring to  FIG. 4 , the clinching process continues as the press (not shown) advances the press ram tool  13  downwardly into contact with nut  17 , which enters and contacts the bottom of the socket  12 . As the press stroke continues to advance, the press ram tool  13  drives the nut and pin downwardly against the upward biasing force of the lower ejector spring  27  as shown in  FIG. 5 . 
         [0032]    In  FIG. 5 , the press ram tool  13  has now forced the nut  17  into contact with the tongue  15  since the ejector pin  23  has also moved downward. The force on the nut  17  and tongue  15  now begins to move the collet  18  downward, which causes two spring-loaded actions. First, it allows the nut and the tongue to be maintained in moveable, aligned contact against the reactive force of the bottom spring  27 . Second, the upper spring  25  urges the tongue  15  into constant contact with the top of the collet  18  between the jaws  19  as the collet  18  is moved downward by the force of the press ram tool  13  against the nut  17  and tongue  15 . 
         [0033]    Referring to  FIG. 6 , the downward motion of the press ram tool has continued until the tongue  15  has been fully captured between the collet jaws at their closest clamp distance by the wedging action of the tapered collet  18  against the tapered inner wall  31   a  of the upper housing socket  16  as shown by the arrows in this Figure. At this point in the installation sequence, the collet  18  has bottomed out against socket end wall  26  with the upper spring  25  fully compressed. The depth of the socket  16  in the housing  21  is designed so that the collet  18  will bottom out at the minimum clamp jaw distance equal to the proper free width of the tongue  15 . 
         [0034]    In  FIG. 7 , the tongue  15  remains clamped to prevent bulging. The pressing force on the nut  17  has continued to the maximum amount to achieve clinch attachment to the ring tongue  15 . The “hard stop” of the collet  18  against the bottom wall  26  of the socket ensures that the final desired installation force against the nut  17  is fully realized because it is independent of the clamping action of the collet  18 . The downward installation stroke of the press can continue up to a maximum point where the press ram tool  13  contacts the collet  18  as seen here. If so designed, the depth of the socket  12  in the end of the press ram tool  13  can define the maximum insertion distance of the nut  17  into the tongue  15 . 
         [0035]    In  FIG. 8 , with the nut fully clinched to the tongue  15 , the press ram tool  13  has been withdrawn and detached from the nut. The ejector pin  23  now ejects the end ring assembly upward from between the collet jaws  19 . The collet  18  and the ejector pin  23  are moved upward by the force of their respective springs  25  and  27 . Upward travel of the collet is limited by abutment between the shoulder  31   d  and collar  29 . At this point the completed end ring assembly has been ejected and is ready for removal from the ejector pin  23  so that the next installation cycle can begin. 
         [0036]    In this embodiment, the above-described tooling provides several sequential functions. The tooling clamps the lateral sides of the tongue  15  to prevent bulging during clinching. The tooling also concentrically aligns the fastener, such as a clinch nut, with the hole in the tongue  15 , and ejects the completed assembly after pressing. These functions are achieved by tooling that provides rapid assembly with fewer rejected parts, which therefore makes its operation very efficient and cost effective. 
         [0037]    The foregoing is to be considered illustrative only of the principles and possible embodiments of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described. Accordingly, suitable modifications and equivalents may be resorted to, all falling within the scope of the invention which shall be determined only by the following claims and their legal equivalents.