Patent Publication Number: US-6981327-B2

Title: Two piece punch with pilot hole locator

Description:
BACKGROUND OF THE INVENTION 
   The present invention relates to an improved punch which is used in conjunction with a punch driver to punch holes in a work piece, such as for example, sheet metal, aluminum, fiberglass and plastic. 
   Generally, when a hole is to be punched in a work piece, a small pilot hole is first drilled in the work piece. A punch assembly is then used to create a hole of the desired dimensions in the work piece. A prior art punch assembly  10  is shown in FIG.  1 . The punch assembly  10  includes a die  12 , a punch  14 , and a draw stud  16 . A first end  18  of a draw stud  16  is threaded into a ram  20  of a hydraulic punch driver  21 . The operator locates the punch assembly  10  in the pilot hole  24  by using “alignment marks”. A second end  22  of the draw stud  16  is inserted through the die  12  and then through the drilled pilot hole  24  in the work piece  26 , the draw stud  16  having a circumference that is less than the circumference of the drilled hole  24 . The punch  14  is threaded onto the second end  22  of the draw stud  16  on the opposite side of the work piece  26  from the die  12  and the driver  21 . An operator actuates a hydraulic punch driver  21 . When the hydraulic punch driver  21  is actuated, hydraulic fluid forces the ram  20  to pull the draw stud  18 . The draw stud  18 , in turn, pulls the punch  14  through the work piece  26  into the die  12  such that the desired hole is punched in the work piece  26 . 
   Punch assemblies used in the prior art suffer from a number of disadvantages. One such disadvantage is that the prior art punch assemblies do not provide means for locating the punch assembly in the pilot hole as the punch and the die are drawn together by the draw stud to make a hole in the workpiece. The alignment marks currently used to align the punch assembly with the pilot hole can be difficult to see by the operator and may allow for error such that the hole to be created may not be properly positioned. 
   Another disadvantage of prior art punch assemblies is that a significant amount of material is used to manufacture the punch which adds to the expense of the punch assembly. 
   Yet another disadvantage of the prior art punch assemblies is that the process for forming the punch can be very costly. 
   An even further disadvantage of the prior art punch assemblies is that the punch is costly to replace as it becomes worn after use. 
   Thus, it is desirable to have a punch assembly which incorporates the advantages of the prior art punches, but which overcomes the disadvantages of the prior art punch assemblies, such as those identified above. The invention, as described herein, provides such a punch assembly. Other features and advantages of the punch assembly of the present invention will become apparent upon a reading of the attached specification in combination with a study of the drawings. 
   OBJECTS AND SUMMARY OF THE INVENTION 
   A primary object of the invention is to provide a punch which improves punch alignment over prior art punches, such as the current difficult to see alignment marks. 
   An object of the invention is to provide a punch which is lower in cost to manufacture than those found in the prior art. 
   Yet another object of the invention is to provide a punch which can be replaced more economically than punches found in the prior art. 
   Briefly, and in accordance with the foregoing, a punch is provided which includes two pieces, a nut and a cutter. One end of the nut is passed through an aperture in the cutter and the draw stud is threadedly engaged with the nut. The nut also functions as a pilot hole locator such that when the punch and the die are drawn together by the draw stud to make a hole in a workpiece, the pilot hole locator on the nut locates the punch assembly in the pilot hole. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The features of the present invention which are believed to be novel are described in detail hereinbelow. The organization and manner of the structure and operation of the invention, together with further objects and advantages thereof, may best be understood by reference to the following description taken in connection with the accompanying drawings wherein like reference numerals identify like elements in which: 
       FIG. 1  is an elevated view of a prior art punch assembly; 
       FIG. 2  is a perspective view of the punch of the present invention, the punch being formed of a nut and a cutter; 
       FIG. 3  is a side-elevational view of the punch of  FIG. 2 ; 
       FIG. 4  is another side-elevational view of the punch of  FIG. 2 ; 
       FIG. 5  is a top plan view of the punch of  FIG. 2 ; 
       FIG. 6  is a perspective view of one embodiment of the cutter of the present invention; 
       FIG. 7  is a side-elevational view of the cutter of  FIG. 6 ; 
       FIG. 8  is another side-elevational view of the cutter of  FIG. 6 ; 
       FIG. 9  is a top plan view of the cutter of  FIG. 6 ; 
       FIG. 10  is a perspective view of the nut of the present invention; 
       FIG. 11  is a side-elevational view of the nut of  FIG. 10 ; 
       FIG. 12  is another side-elevational view of the nut of  FIG. 10 ; 
       FIG. 13  is a top plan view of the nut of  FIG. 10 ; 
       FIG. 14  is a perspective view of an alternative embodiment of the cutter of the present invention; 
       FIG. 15  is a side-elevational view of the cutter of  FIG. 14 ; 
       FIG. 16  is another side-elevational view of the cutter of  FIG. 14 ; 
       FIG. 17  is a top plan view of the cutter of  FIG. 14 ; and 
       FIG. 18  is a cross-sectional view of the cutter of  FIG. 14  along the line  18 — 18  of FIG.  14 . 
   

   DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENT 
   While this invention may be susceptible to embodiment in different forms, there is shown in the drawings and will be described herein in detail, specific embodiments with the understanding that the present disclosure is to be considered an exemplification of the principles of the invention, and is not intended to limit the invention to that as illustrated. 
   A punch  40  is provided and illustrated in  FIGS. 2-5 . The punch  40  is useful for punching a hole through a workpiece (not shown). The punch  40  is used with a die (not shown) which is well known in the art as well as a draw stud (not shown) which is also well known in the art. A first end of the draw stud is typically threaded to a ram (not shown) of a punch driver (not shown). A second end of the draw stud is inserted through the die, and through a pilot hole (not shown) which is provided in the workpiece (not shown), the draw stud having a circumference that is less than the circumference of the pilot hole. The punch  40  is then attached to the second end of the draw stud on the opposite side of the workpiece than is the die and the hydraulic punch driver as will be described herein. In describing the punch  40  of the present invention, elements more closely located to the driver will be described as proximal and elements located further from the driver will be described as distal. 
   The punch  40  generally includes a cutter  42  and a nut  44 . The cutter  42  is generally disc shaped with a circular aperture  46  located through the axial center of the cutter  42 . The cutter  42  can be made from carbon or alloy steel, for example. In the preferred embodiment a surface hardness of Rc  53 - 58  and a minimum core hardness of Rc  40  are achieved. The cutter  42  can be formed, for example, by stamping, investment casting, die casting, cold heading or forging for minimal piece cost and tooling economy. 
   The nut  44  is generally cylindrical. The nut  44  is preferably made from metal and is preferably treated by quenching and tempering. The nut  44  is slip fit to the cutter  42  by positioning the nut  44  within the aperture  46  of the cutter  42 . 
   A first embodiment of the cutter  42  is shown in  FIGS. 2-8 . A second embodiment of the cutter is shown in  FIGS. 14-18 . 
   The first embodiment of the cutter  42  is best illustrated in  FIGS. 6-9 . The cutter  42  generally includes a proximal surface  50 , a distal surface  52  and the circular aperture  46 . The proximal surface  50  will be positioned proximate the workpiece to be cut. As viewed in a plan view (FIG.  9 ), the cutter  42  is generally circular. The proximal surface  50  of the cutter  42  includes center surfaces  54 , first inclined surfaces  56  and second inclined surface  58 . 
   As best shown in  FIG. 9 , the center surfaces  54  extend from opposite sides of the perimeter of the aperture  46  to the perimeter of the proximal surface  50 . The first inclined surfaces  56  are generally arch shaped and are diametrically opposed. Each first inclined surface includes an inner edge  64 , an outer edge  66 , and cutting edges  68 . The inner edges  64  of each of the first inclined surfaces  56  are generally C-shaped and abut center surfaces  54  and the aperture  46 . Each outer edge  66  is spaced from the aperture  46  and is generally parallel to the center surfaces  54 . The cutting edges  68  are arcuate and extend along the perimeter of the proximal surface  50  from the center surfaces  54  to the outer edge  66 . 
   The second inclined surfaces  58  are generally triangularly shaped. Each second inclined surface  58  includes an inner edge  70 , an outer piercing tip  72  and cutting edges  74 . Each inner edge  70  abuts a respective one of the outer edges  66  of the first inclined surfaces  56 . Each tip  72  is spaced from the respective inner edge  70  and positioned on the perimeter of the proximal surface  50 . The cutting edges  74  of each of the surfaces  58  extend from opposite ends of the inner edges  70  and join at the respective tips  72 . 
   The first inclined surfaces  56  slope upwardly (as shown in  FIG. 7 ) from the axial center of the cutter  42  in opposite directions at an angle ∝. In the preferred embodiment, the angle ∝ is approximately 70°. The second inclined surfaces  58  slope upwardly from the first inclined surfaces  56  at an angle β. In the preferred embodiment, the angle β is approximately 45°. 
   As best shown in  FIGS. 7 and 8 , the distal surface  52  of cutter  42  includes center portions  80 , first inclined surfaces  82 , seat portions  84 , and second inclined surfaces  86 . The center portions  80  are diametrically opposed and extend from the aperture  46  to the perimeter of the distal surface  52 . The center portions  80  are generally parallel to the center surfaces  54  of the proximal surface  50  and perpendicular to the axial center of the cutter  42 . The first inclined surfaces  82  are generally arched and abut the center portions  80  and the aperture  46 . The first inclined surfaces  82  extend radially outwardly from the center portions  80 , generally parallel to the first inclined surfaces  56  of the proximal surface  50 . The seat portions  84  extend outwardly from the first inclined surfaces  82 . The seat portions  84  include first walls  84   a  and second walls  84   b . The first walls  84   a  of the seat portions  84  are generally perpendicular to the axial center line of the cutter  42 . The second walls  84   b  extend from the outer ends of the first walls  84   a  and are generally perpendicular to the first walls  84   a  and parallel to the axial center line of the cutter  42 . The second inclined surfaces  86  extend from the first inclined surfaces  82  to the perimeter of the distal surface  52 . 
   An end surface  88  connects the proximal surface  50  to the distal surface  52 . The end surface  88  includes beveled portions  90  proximate the tips  72 . 
   As best shown in  FIG. 9 , the cutter  42  includes diametrically opposed chamfers  94  proximate the aperture  46 . Alternatively, the chamfers  94  can be eliminated from the cutter  42 . 
   As shown in  FIGS. 10-13 , the nut  44  includes a generally cylindrically shaped first portion  100  and a generally cylindrically shaped second portion  102 . The first portion  100  includes a fixed end  100   a  and a free end  100   b . The second portion  102  includes a fixed end  102   a  and a free end  102   b . The fixed end  100   a  of the first portion  100  abuts the fixed end  102   a  of the second portion  102 . The outer diameter of the first portion  100  is larger than the outer diameter of the second portion  102 . The outer diameter of the second portion  102  is smaller than the diameter of the pilot hole to be drilled in the workpiece. A tapered surface  104  is provided on the free end  102   b  of the second portion  102 . 
   A driving surface  103  is provided by the first portion  100 , proximate the fixed end  100   a . Diametrically opposed shoulders  106  are also provided proximate the fixed end  100   a  of the first portion  100 . As best shown in  FIG. 13 , the driving surface  103  includes two arch shaped portions  103   a ,  103   b . Each arch shaped portion  103   a ,  103   b  extends from the perimeter of the first portion  100  to the perimeter of the second portion  102  and between the shoulders  106 . Each shoulder  106  includes a first surface  106   a  parallel to and spaced from the driving surface  103  and a second surface  106   b  perpendicular to the first surface  106   a  and extending from the first surface  106   a  to perimeter of the first portion  100 . 
   A passageway  108  is provided through the axial center of the nut  44 . A thread  110  is provided on the inner wall of the passageway  108  for joining the nut  44  with the draw stud as will be described herein. 
   The second embodiment of the cutter is shown in  FIGS. 14-18 . The cutter  142  includes a proximal surface  150 , a distal surface  152  and a circular aperture  146 . The proximal surface  150  will be positioned proximate the workpiece to be cut. As viewed in a plan view (FIG.  17 ), the cutter  142  is generally circular. The proximal surface  150  of the cutter  142  includes center surfaces  154 , first inclined surfaces  156 , and second inclined surface  158 . 
   As best shown in  FIG. 17 , the center surfaces  154  extend from opposite sides of the perimeter of the aperture  146  to the perimeter of the proximal surface  150 . Each first inclined surface  156  includes an inner edge  164 , an outer edge  166 , and cutting edges  168 . The inner edges  164  of each of the first inclined surfaces  156  are generally C-shaped and abut center surfaces  154  and the aperture  146 . Each outer edge  166  is spaced from the aperture  146  and is generally parallel to the center surfaces  154 . The cutting edges  168  extend along the perimeter of the proximal surface  150  from the center surfaces  154  to the outer edge  166 . 
   The second inclined surfaces  158  are generally triangularly shaped. Each second inclined surface includes an inner edge  170  an outer piercing tip  172 , and cutting edges  174 . Each inner edge  170  abuts a respective one of the outer edge  166  of the first inclined surface  156 . Each tip  172  is spaced from the respective inner edge  170  and positioned on the perimeter of the proximal surface  150 . The cutting edges  174  extend from opposite ends of each inner edge  170  and join at the respective tips  172 . 
   The first inclined surfaces  156  slope upwardly from the axial center of the cutter  142  in opposite directions at an angle ∝. In the preferred embodiment, the angle ∝ is approximately 70°. 
   The second inclined surfaces  158  slope upwardly from the first inclined surfaces  156  at an angle β. In the preferred embodiment, the angle β from the axial center of the cutter  142  to each second inclined surface  158  is approximately 45°. 
   The cutting edges  174  slope upwardly toward each tip  172 . As shown in  FIG. 16 , an angle θ is provided between the axial center of the cutter  142  and the cutting edges  172 . In the preferred embodiment the angle θ is approximately 108°. 
   As best shown in  FIGS. 15 ,  16  and  18 , the distal surface  152  of cutter  142  includes center portions  180 , first inclined surfaces  182 , seat portions  184 , and second inclined surfaces  186 . The center portions  180  are diametrically opposed and extend from the aperture  146  to the perimeter of the distal surface  152 . The center portions  180  are generally parallel to the center surfaces  154  of the proximal surface  150  and perpendicular to the axial center of the cutter  142 . The first inclined surfaces  182 , as shown in  FIG. 16 , are generally arched and abut the center portions  180  and the aperture  146 . The first inclined surfaces  182  extend radially outwardly from the center portions  180 , generally parallel to the first inclined surfaces  156  of the proximal surface  150 . The seat portions  184  extend outwardly from the first inclined surfaces  182 . The seat portions  184  include first walls  184   a  and second walls  184   b . The first walls  184  are generally perpendicular to the axial center line of the cutter  142 . The second walls  184   b  extend from the outer ends of the first walls  184   a  and are generally perpendicular to the first walls  184   a  and are generally parallel to the axial center line of the cutter  142 . The second inclined surfaces  186  extend outwardly from the first inclined surfaces  182  to the perimeter of the distal surface  152 . 
   An end surface  188  connects the proximal surface  150  of the cutter  142  to the distal surface  152  of the cutter  42 . The end surface  188  includes beveled portions  190  proximate the tips  172 . 
   As best shown in  FIGS. 17 and 18 , the cutter  142  includes diametrically opposed chamfers  194  proximate the aperture  146 . Alternatively, the chamfers  194  can be eliminated from the cutter  142 . 
   As shown in phantom line in  FIG. 18 , end surfaces  200  can be provided which extend from the end surfaces  188  of the cutter  142 . Unlike the end surfaces  188  which are generally perpendicular to the axial center of the cutter  142 , the end surfaces  200  are angled relative to the axial center of the cutter  142 . 
   Assembly of the two piece punch  40  will now be described. To begin, the operator selects a cutter, for example, cutter  42  which corresponds to the dimension of the hole to be cut. To assemble the two piece punch  40 , the nut  44  is positioned proximate the distal side  52  of the cutter  42 . The second portion  102  of the nut  44  is then passed through the aperture  46  of the cutter  42 . The cutter  42  is then rotated on the nut  44  in such a manner that the center surfaces  54  of the cutter  42  are aligned with the shoulders  106  of the nut  44 . The operator continues to pass the nut  44  through the cutter  42  until the distal surface of the cutter  42  engages the nut  44 . In particular, the center portions  80  of the distal surface  52  of the cutter  42  contact the first surfaces  106   a  of the shoulders  106  and the seat portions  184  of distal surfaces  82  of the cutter  42  contact the driving surfaces  103   a ,  103   b  of the nut  44 . Upon assembly of the cutter  42  and nut  44 , the inner wall of the aperture  46  of the cutter  42  will engage with the second surfaces  106   b  of the shoulders  106  to prevent the cutter  42  from rotating relative to the nut  44 . 
   Assembly of the punch  40  with the remainder of the punch assembly will now be discussed. As explained above, an operator threads a proximal end of the draw stud to a ram of a punch driver. The distal end of the draw stud is passed through a die and through a pilot hole which is provided in a workpiece, the draw stud having a circumference which is less than the circumference of the pilot hole. The punch  40  is then attached to the distal end of the draw stud on the opposite side of the workpiece than is the die and the hydraulic punch driver. The punch  40  is attached to the draw stud by threading the second end of the draw stud into the threaded passageway  108  of the nut  44 . 
   The operator then turns the punch  40  onto the draw stud until the punch  40  and the die fit snugly against the workpiece and the tapered surface  104  of the nut  44  enters the pilot hole and causes the punch  40 , the draw stud and die to center on the pilot hole. The operator could also actuate a hydraulic punch driver until the punch and the die are snug against the workpiece. 
   After the tapered surface  104  of the nut  44  enters the pilot hole to center the punch  40 , the operate actuates the hydraulic punch driver such that hydraulic fluid forces the ram to pull the draw stud, which in turn pulls the nut  44  of punch  40 . The driving surface  103  of the nut  44  pushes on the distal surface of the cutter  42  such that the tips  72  of the cutter  42  pierce the workpiece and the cutting edges  68 ,  74  cut the workpiece along the perimeter of the cutter  42 . As a result, a hole is created which has a diameter equivalent to the diameter of the proximal surface  50  of the cutter  42  and which is larger than the pilot hole. 
   The configuration of the punch  40 , in comparison to punches of the prior art, reduces the initial piercing force by reducing the area of contact between the punch  40  and the workpiece. Due to the angle β of the piercing tips  72 , the piercing tips  72  substantially pass through the workpiece before the cutting edges  68 ,  74  begin cutting the hole. Upon passage of the nut  44  through the workpiece, a hole having the desired dimensions is cut. 
   Several advantages are provided by the two piece punch  40 . One such advantage is that the operator does not have to use alignment marks to center the punch  40 . Rather, the operator simply places that tapered surface of the nut  44  within the pilot hole. When the operator actuates the hydraulic punch driver, the punch  40 , draw stud and die will center on the pilot hole, eliminating alignment errors. 
   Another advantage of the punch  40  of the present invention is that the operator can vary the size of the hole formed by the punch  40  by simply selecting a cutter  42  with the desired diameter dimensions. Thus, multiple sized cutters  42  can be used with a single nut  44 . 
   Yet another advantage of the present invention is the ability to economically replace the cutter  42 . After extended use of the punch assembly, the punch  40  becomes worn and must be replaced in order for the punch assembly to effectively cut the workpiece. A significant amount of material is used to make the punches of the prior art. In addition, the process of threading the interior surface of the prior art punches is costly. Due to the amount of material and the processes used to form the prior art punches, replacement of the prior art punches is costly. The two piece punch  40  of the present invention includes the nut  44  having the internal thread  110  and the cutter  42  which does not have a threaded portion. When the cutter  42  of the punch  40  becomes worn, only the cutter  42  of the punch  40  must be replaced, not the nut  44 . Thus, significantly less material is replaced than with the prior art punches. As no threading is required on the cutter  42  of the punch  40 , the cutter  42  can be economically stamped. Although, the cutter  42  of the punch  40  is replaced, the nut  44  portion of the punch  40 , which includes the threaded portion  110 , can continue to be used. 
   In an alternative embodiment, the cutter  42  of the punch  40  could include a proximal/working surface similar to the punch sold under the tradename SLUG BUSTER®. In such an embodiment, the portion of the workpiece which has been cut away to form the hole (i.e. the slug) is broken in to multiple pieces for easy removal of the slug from the die. 
   While preferred embodiments of the present invention are shown and described, it is envisioned that those skilled in the art may devise various modifications of the present invention without departing from the spirit and scope of the appended claims.