Abstract:
A clamp for use in forming parts is disclosed. The clamp is durable and easily installed, thereby resulting in superior efficiency.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to U.S. Provisional Application No. 60/786,559 which was filed on Mar. 28, 2006. 
     
     FIELD OF THE INVENTION 
       [0002]    This invention relates generally to a clamp for use within a press used to form parts, and more specifically to a durable and easily installed clamp which has superior efficiency. 
       BACKGROUND OF THE INVENTION 
       [0003]    Presses used in forming parts usually require the use of clamps in order to hold the dies (workpieces) that form those parts. However, it can be difficult to install and remove these clamps, as they are subject to a significant amount of mechanical stress and thus must be carefully installed. Consequently, an improved clamp for attachment to a press used in forming parts is desired. 
       SUMMARY OF THE INVENTION 
       [0004]    It is an object of the present invention to provide a clamp for use in a press that is durable, but can also be installed and removed quickly. It is an additional object of the present invention to do so using a variety of implementations, including but not limited to an optional heelblock. These and other objects and advantages of the invention will become readily apparent as the following description is read in conjunction with the accompanying drawings. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]      FIGS. 1 and 2  show a first embodiment of the present invention; 
           [0006]      FIGS. 3 and 4  show the embodiment of  FIGS. 1 and 2  located within a press; 
           [0007]      FIG. 5  shows a fastener used within the present invention; 
           [0008]      FIGS. 6A-6B  show front and top views of a topcap used within the present invention; 
           [0009]      FIGS. 7A-7B  show front and top views of a clamp bar used within the present invention; 
           [0010]      FIGS. 8A-8B  show front and top views of a collet used within the present invention; 
           [0011]      FIGS. 9A-9B  show front and top views of a stem nut used within the present invention; 
           [0012]      FIGS. 10 and 11  show a second embodiment of the present invention; 
           [0013]      FIGS. 12A-12C  show a heelblock used within the embodiment of  FIGS. 10-11 ; and 
           [0014]      FIGS. 13 and 14  show side and front views respectively of a press incorporating the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0015]    Before explaining the disclosed embodiment of the present invention in detail it is to be understood that the invention is not limited in its application to the details of the particular arrangement shown, since the invention is capable of other embodiments. Also, the terminology used herein is for the purpose of description and not of limitation. 
       The Present Invention (Apparatus)  
       [0016]      FIGS. 1-4  show a quick die change collet clamp  1  according to the present invention. The clamp  1  is used to secure a workpiece  44  such as a die shoe, die, mold, or fixture to a work surface  43  of a press  65 . As shown in  FIGS. 2-3 , the workpiece  44  has upper and lower halves  44   U  and  44   L . [ 0001   7 ] As shown in  FIGS. 1 and 2 , the clamp  1  comprises a stem nut  26 , a topcap  3  for holding the stem nut  26  in position, a clamp bar  7  for securing the workpiece  44 , and a head  40 , all attached to a fastener  39 .  FIG. 2  further introduces a collet  1   7 . 
         [0017]    The process of stamping a part is shown in  FIGS. 3A-3B  and  4 . A ram  68  within the press  65  is shown going up and down, thereby opening and closing the workpiece  44 . The workpiece  44  is shown in  FIGS. 3 and 4  with a jagged edge to illustrate that it is one part of a larger operation, and works in conjunction with and rests on top of the work surface  43  of the press  65 . However, this jagged edge is for illustrative purposes only, so that the workpiece  44  and work surface  43  should not be considered as limited only to the exemplary jagged shape. Also, although  FIGS. 3A-3B  suggest a press  65  having a vertical motion, other directions of motion are also contemplated within the spirit and scope of the present invention 
         [0018]    To stamp a part, first, the press  65  is opened by raising the ram  68 , as shown in  FIG. 3A . This causes the workpiece  44  to separate into upper and lower halves  44   U  and  44   L  Different parts made by the press  65  may required different workpieces. Accordingly, the clamps  1  are then adjusted to fit to a specific workpiece  44  useful for making the desired part. Afterwards, strips of raw material are put into the workpiece  44 . Then, the press  65  is operated by lowering the ram  68 , thereby closing the workpiece  44 , forcing the upper and lower halves  44   U  and  44   L  together at enormous pressure. When the workpiece  44  is closed, a part (not shown) is then produced. The workpiece  44  is then opened and the part is removed. 
         [0019]    The clamp  1  holds the workpiece  44  securely within the press  65  by closely fitting (as shown by the jagged line in  FIGS. 3-4 ) the upper and lower halves  44   U  and  44   L  together. It is important that the workpiece  44  be secure within the press  65 , because some presses exert as much as 3000 tons onto the workpiece  44 . Consequently, the clamp  1  of the present invention must be reliable and extremely durable. However, the clamp  1  must also be easily loosened when it is time to change out the workpiece  44 . 
         [0020]    Any time spent making adjustments to a clamp is equivalent to time where the press  65  is not in productive use, in other words idle or down-time. It is desired to minimize all down-time, and have the press  65  be in productive economic use as high a percentage of time as possible. The clamp  1  of the present invention reduces such idle or down-time. 
         [0021]    As shown in  FIG. 5 , the fastener  39  can be but is not limited to a large bolt. Whatever the exact shape, the fastener  39  should have a shaft extending longitudinally with a generally circular cross-section. That shaft will have a threaded portion  81 . The threaded end  81  of the shaft may have a diameter other than the diameter of the remainder of the shaft. The fastener  39  also has a head  40  opposite the threaded end  81 . This head  40  is generally rectangular or square in cross-section, so as to facilitate slidable movement within the slots  42  of the stamping machine  65 . 
         [0022]    The topcap  3  ( FIGS. 6A and 6B ) secures the stem nut  26  and the collet  17  within the clampbar  7 . Among other functions, the topcap  3  retains the stem nut  26  in location, preventing dirt and debris from entering the overall collet assembly, and maintaining the clamp  1  as a single piece unit. 
         [0023]    As shown in  FIGS. 6A-6B , the topcap  3  includes two or more tapered apertures  4  extending therethrough. The topcap  3  includes suitable fasteners such as threaded screws  2  which pass through the apertures  4  in the topcap  3  and engage the threaded aperture  14  in the clamp bar  7  to secure the topcap  3  in position. One end of the topcap  3  contains an aperture  5 . intentionally formed to be similar in size to the stem nut  26  which allows the stem nut  26  to partially penetrate the opening  6  ( FIGS. 6A ,  6 B). One purpose of the aperture  5  is to retain the stem nut  26 , thereby limiting penetration of debris or dirt. 
         [0024]      FIGS. 7A and 7B  show side and top views respectively of the clamp bar  7 , which moves along the shank of the fastener  39  to engage and disengage the workpiece  44 . The clamp bar  7  is generally circular in shape and includes an aperture  13  extending therethrough. The aperture  13  is intentionally only slightly larger than the fastener  39 , is also generally circular in shape, and sits in close contact with the stem nut  26  and collet  17 , thereby keeping dirt and debris from entering the clampbar  7 . 
         [0025]    As shown in  FIG. 7A &amp; 7B , a collet aperture  16  contained within clamp bar  7  is generally conical in shape, with an enlarged area  15  opposite the aperture  13 . The collet  17  is contained within this conical aperture  16 . A conical aperture  16  provides the means to close the collet  17  upon action of the stem nut  26 . The conical aperture  16  is designed to be similar in taper to the collet  17 . 
         [0026]      FIGS. 8A and 8B  show the split-ring collet  17 , which in actual use is engaged by both the stem nut  26  on one end, and the clamp bar  7  on the other. The split-ring collet  17  may incorporate a singular or plurality of slits  19  therein, for separating it into equal pieces. Such separation may help reduce stress and provide for a more equal distribution of forces. The tapered exterior  20  slides up and down into the interior taper  16  of the clamp bar  7  when acted on by the stem nut  26  during tightening and loosening. Such tightening and loosening should preferably be performed by a wrench, as hand-tightening will not generate sufficient torque to lock the stem nut  26  into place. 
         [0027]    The action of the collet  17  is to compress under the forces exerted by the taper  16  and the bottom of the stem nut flange  25 , and also to encircle and inhibit the rotation of the stem nut  26 . This causes the collet  17  to contact and therefore restrict rotation of the stem nut  26  during tightening. Ideally, such restriction of rotation will occur only when a sufficient clamping force has occurred between the clamp bar  7  and the work surface. 
         [0028]      FIGS. 9A-9B  show the stem nut  26 , which movably and rotatably engages with the threaded end  81  to move the clamp bar  7 , topcap  3 , collet  17  and heelblock  34  as one unit along the threaded end  81  of the fastener  39 . To achieve this, the stem nut  26  includes a protrusion  23  which can be cylindrical in shape and has a plurality of wrench flats  32  to form a shape suitable for allowing a tool to engage and rotate it. Contained on the nut  26  beside the wrench flats  32  is a cylindrical flange  25  extending radially outward from the stem nut  26  which is larger than the remainder of the stem nut  26 , yet smaller than but similar in thickness to the combined apertures  5  and  15 . The stem nut  26  also has an aperture  30  extending therethrough and being threaded  31  to engage with the threaded end  81 . 
         [0029]    The stem nut  26  further includes a stem  29  extending axially from the flange  25 . As shown in  FIG. 7 , the stem  29  can have a generally circular and tubular shape extending somewhat from the flange  25  of the stem nut  26  opposite the flange  25 . The stem  29  provides the location for the collet  17  to contact during tightening and active use. The stem  29  also acts to restrict the further rotation of the stem nut  26  when optimum clamping force is achieved. The stem nut  26  also contains radiused corners  24  and  28  ( FIGS. 7 and 8 ) to reduce point-loaded corners. Reducing point-loaded corners extends the useful life of the clamp  1  by eliminating stress-points that can cause the material of the clamp  1  to fatigue and fail after repeated usages. 
         [0030]    Under certain circumstances, it may be necessary to add a heelblock to the clamp  1 , such as when used with an unslotted die shoe. To that end,  FIGS. 10-11  show the clamp  1  with a heelblock  34  incorporated therein. As shown in  FIGS. 12A-12C , the heelblock  34  has a predetermined height to allow the clamp bar  7  to remain substantially planar when engaged with an unslotted die shoe  38 . The heelblock  34  is generally semi-circular in shape and may have a guide  36  extending outwardly at one end. The guide  36  is generally rectangular in shape and facilitates slidable movement within the slots  42 . The heelblock  34  may be located at the outer diameter of the clamp bar  7  to move the pressure center of the heelblock  34  away from the center line of the fastener  39 . 
         [0031]    It should be appreciated that the increased distance between the heelblock  34  and the center line of the fastener  39  has the effect of increasing the force of the clamp  1  on the workpiece  44 , as compared to a heelblock located beside the fastener  39 . To facilitate this, the heelblock  34  includes at least one, and preferably a pair of apertures  33  extending therethrough. The heelblock  34  is secured to the clamp bar  7  by suitable means such as threaded fasteners  35 , which pass through the aperture  33  and engage threaded aperture  11  in the clamp bar  7 . 
         [0032]      FIG. 13  is a side view of one possible configuration the press  65 , and  FIG. 14  is a front view of  FIG. 13 . As illustrated in  FIGS. 13-14 , the clamp(s)  1  may be used for securing an item such as a slotted die shoe  37  or unspotted die shoe  38  to the workpiece  44  within the press  65 . The work surface  43  of the press  65  includes at least one and preferably a plurality of generally T-shaped slots  40 . These T slots  40  will vary in width according to the size of the press  65 . 
         [0033]    Referring to  FIG. 13 and 14 , the head  40  also has a width less than a width of the slots  42  to allow the head  40  to slide in the slots  42 , but still has sufficient width to prevent damage to interior corners of the slots  42  during the inevitable turning of the head  40  when tightening the stem nut  26 . The shaft  39  may also have a relief portion (not shown) to provide the shaft with a diameter width to allow the head to have a larger width than conventional fasteners. The fastener  39  is anchored in the slot by the head  40 . 
         [0034]    If the clamp  1  is used to clamp to an unslotted die shoe  38 , the clamp  1  will include the heelblock  34 . Conversely, if the clamp  1  is to be used with a slotted die shoe  37 , the heelblock  34  may be omitted. 
       Method of Assembling the Present Invention  
       [0035]    Referring now to  FIGS. 1-2 , to assemble the clamp  1 , preferably the stem nut  26  is disposed in the split ring collet  17 , then inserted into the clamp bar  7  recess, and is then aligned with the aperture  15 . The stem nut  26  is inserted in the aperture  6 . After such insertion, the collet  17  will contact the opposing conical relief  16  of the clamp bar  7 , which allows movement of the stem nut  26  axially within the clamp bar  7 . The topcap  3  is then applied to the clamp bar  7  with the fasteners  2 . In this manner, the stem nut  26 , topcap  3 , and clamp bar  7  and collet  17  are a single integrated unit or assembly such that the stem nut  26  may freely rotate. It is important that the stem nut  26  not be hindered in movement, otherwise it will be difficult to assemble/disassemble and install/uninstall the clamp  1 . 
         [0036]    Once assembled, the fastener  39  is inserted through clamp bar aperture  13  and threaded into the threads  31  of aperture  30 . The stem nut  26  can then be rotated so as to move axially along the threaded end  81  of the fastener  39 , thereby tightening the clamp  1 . 
       Method of Using the Present Invention  
       [0037]    In operation, the head  40  of the fastener  39  is disposed in a slot  42  of the workpiece  44 , as shown in  FIGS. 13 and 14 . The clamp  1  is moved until the clamp bar  7  is partially or entirely disposed over the workpiece  44 . The stem nut  26  is then rotated to move the clamp bar  7  toward the work surface  37  or  38  such that the clamp bar  7  engages or snugs down on the workpiece  44 . At that point, the stem nut  26  is rotated further, perhaps  180  degrees, preferably with a tool such as a wrench, to develop a desired clamping force on a work surface  43 . As the clamping force develops on the workpiece  44 , the tapered side  20  of the split-ring collet  17  and the opposing, somewhat similar taper  16  of the clamp bar  7  engage to constrict the collet  17 . When the desired clamping force is achieved, the compressional engagement between the collet  17  and stem nut  26  prevents further rotation of the stem nut  26 , but also restricts it from loosening during operation but still maintains a clamping force on the workpiece  44 . 
         [0038]    To remove the clamp  1 , the stem nut  26  is rotated in the opposite direction. This causes the collet  17  to open and thereby relieve pressure upon the stem nut  26 , bringing the pressure down to a level preferably equal to that exerted on a standard threaded nut. As rotation occurs, the clamp bar  7  distances itself from the workpiece  44 , thereby releasing clamping pressure on the work piece  44 . As the stem nut  26  is rotated further, it moves along the threaded end  81  and away from the work piece  44  such that the clamp bar  7  eventually disengages the workpiece  44 . 
         [0039]    It should be appreciated that to entirely release the clamp, the stem nut  26  need be turned only slightly, just enough to clear the workpiece  44 . A user can then quickly remove the clamp  1  and re-insert, hence the name “quick die change collet clamp”. 
         [0040]    As shown in  FIGS. 1 and 2 , the clamp  1  combines a fastener  39 , stem nut  26 , clamp bar  7 , collet  17  and topcap  3  into a single combined unit or assembly thereby saving time in clamping the work piece  44  to the surface of the press  65 . Significant time is saved by eliminating any need to handle various bars, loose washers, or other things that are normally attached to a typical clamp. The clamp  1  also removes the possibility of loose washers and nuts from being left in the operating area of the press, which can cause damage to the dies during operation of the press. The clamp  1  also provides a single, unified, easily manipulated device, because the fastener  39 , clamp bar  7 , collet  17 , topcap  3  and stem nut  26  remain attached to one another during clamping, unclamping and even storage. However, the clamp  1  can still be quickly disassembled to be cleaned, repaired, or have parts replaced. 
         [0041]    The present invention has been described in an illustrative manner. It is to be understood that the terminology which has been used is intended to be in the nature of words of description rather than of limitation. Also, many modifications and variations of the present invention are possible in light of the above teachings. Therefore, within the scope of the appended claims, the present invention may be practiced otherwise than as specifically described. Accordingly, it is anticipated that various changes may be made in the arrangement and operation of the system of the present invention without departing from the spirit and scope of the invention, as defined by the following claims.