Abstract:
An apparatus for retaining a tool (20) employs a fastener (22) which has a protuberance (122) engagable with a recess (60) of the tool. The fastener (22) is secured to a fixture (24) thereby serving to concurrently retain the tool (20) to the fixture (24).

Description:
BACKGROUND AND SUMMARY OF THE INVENTION 
     This is a continuation of PCT patent application Ser. No. PCT/US94/08561 filed Jul. 29, 1994, which designated the United States. 
     This invention relates generally to an apparatus for retaining a tool to a fixture and specifically to a fastener having a protuberance which engages an aperture within a tool. 
     Within the equipment, tool and die making industries, it is common to provide various fastening means between machinery components. For example, sheet metal stamping and injection molding dies are typically fastened to their respective die plates by bolts extending through holes within the die. These bolts have a head which engages the die and a threaded shank which enmeshes with a receiving hole within the die plate. Typically, four or more bolts are required to retain each die. 
     Another conventional system provides a T-bolt and an L-shaped brace to secure a die to a bolster plate. Such a system is shown in U.S. Pat. No. 4,912,961 entitled &#34;Structure for Securing a Die to a Bolster Plate&#34; which issued to Brown on Apr. 3, 1990. A riveting instrument has also employed a pair of fingers fastened to a side plate. The fingers retain a malleable anvil piece. This device is disclosed within U.S. Pat. No. 1,211,333 entitled &#34;Riveting Instrument&#34; which issued on Jan. 2, 1917. Yet another device is shown within U.S. Pat. No. 1,190,697 entitled &#34;Means for Shaping Spoon Bowls and the Like&#34; which issued to Wilzin on Jul. 11, 1916. This patent teaches use of four bars which are screwed to a tool holder. These bars act to retain contoured confining dies against the tool holder. However, all of these retention means require extraneous and relatively costly clamps and fasteners. 
     Yet another conventional construction has employed a set screw to retain a TOG-L-LOC® joint die within a die shoe. 
     In accordance with the present invention, the preferred embodiment of an apparatus for retaining a tool is comprised of a fastener which has a protuberance engagable with a recess of a tool. The fastener is secured to a fixture thereby serving to concurrently retain the tool to the fixture. In one aspect of the present invention, a bore within the fixture has a head of the fastener disposed therein. This bore prevents extreme deformation of the fastener upon securing the tool to the fixture. 
     The apparatus of the present invention is advantageous over traditional retention devices since the present invention only requires a single fastener for retaining a tool to a fixture. Thus, quick retention and removal can be affected. This leads to low cost and quick tool set-up. The apparatus of the present invention further provides a very secure retention of the tool to the fixture. The present invention apparatus is also advantageous over conventional designs in that the present invention construction can be employed in combination with any number of different tool and fixture types. The present invention is also much more compact than are the prior art devices. The apparatus of the present invention is also stronger and more reliable than traditional set screw systems. It is also self-centering and prevented from rotation. 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 side elevational view, partially in section, of a punch assembly and die assembly employing a preferred embodiment of the apparatus of the present invention; 
     FIG. 2 is an exploded perspective view showing a first alternate embodiment of the present invention apparatus in combination with the punch and die assemblies of FIG. 1; 
     FIG. 3 is a top elevational view showing the preferred embodiment of the present invention apparatus in combination with a die assembly similar to that of FIG. 1; 
     FIG. 4 is a side elevational view, partially in section as taken along line 4--4 of FIG. 3, showing the preferred embodiment of the present invention apparatus in combination with the die assembly; 
     FIG. 5 is a side elevational view, similar to that of FIG. 4, showing a second alternate embodiment of the present invention apparatus in combination with a die assembly; 
     FIG. 6 is a perspective view showing the first alternate embodiment of the present invention apparatus of FIG. 2; 
     FIG. 7 is a perspective view diagrammatically showing an alternate embodiment recess within a die assembly of the present invention apparatus of FIG. 1; and 
     FIG. 8 is a sectional view, taken along line 8--8 of FIG. 7, showing a bolt and fixture in relation to the alternate embodiment recess. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     An apparatus of the present invention serves to secure a tool to a fixture. The present invention apparatus may be employed with tools such as dies, molds, punches, shearing blades, corner braces or the like. The present invention retaining apparatus may also be used for various fixtures such as die shoes, die plates, presses, building floors, building walls, tables or the like. Referring to FIG. 1, a preferred embodiment of an apparatus of the present invention for retaining tools includes a die 20, a fastener 22 and a die shoe 24. The apparatus of the present invention is also used to retain a punch 26 to a punch holder 28 by way of a fastener 30. 
     As can best be observed in FIGS. 3 and 4, die 20 is generally of the type disclosed within U.S. Pat. No. 5,150,513 entitled &#34;Apparatus for Joining Sheet Material&#34; which issued to Sawdon on Sep. 29, 1992, and is incorporated by reference herewithin. Die 20 includes an anvil 40, a set of movable blades 42 and an expandable retention spring 44. Die 20 also has a bottom 46 and a cylindrical side 48. A recess 60 is cut by an end mill into side wall 48 of die 20. A circular mill cutter may also be used to cut a recess as is alternately shown in FIGS. 7 and 8. Returning to FIGS. 3 and 4, a tapered portion 62 is located along recess 60. Recess 60 is cut within die 20 such that dimension A preferably has a diameter of 0.250 inches as measured 45° from a longitudinal axis 70 of die 20. A dimension B between an apex of recess 60 and axis 70 of die 20 is preferably 0.222 inches. Of course, other sizes can be used depending on the specific tool to be retained. In the alternate embodiment shown in FIGS. 2 and 6, recess 60 further has a semi-cylindrical channel 80 projecting in a longitudinal manner along side 48 so as to extend between the lowermost portion of tapered surface 62 and bottom 46. 
     Referring again to FIGS. 3 and 4, die shoe 24 has a cylindrical cavity 90 cut therein for receiving a lower portion of die 20. A counterbore 92 is also cut within die shoe 24. Counterbore 92 further has a threaded shaft 94 centrally extending therebelow. A ledge 96 is located along the bottom of cavity 90 with a duct 98 projecting downwardly therefrom. Either a threaded dowl 100 (as is shown in FIG. 5) or a nonthreaded dowl 102 (as is shown in FIG. 4) is engaged with duct 98 while the opposite end of dowl 100 or 102 is secured to die 20. 
     The preferred embodiment of the fastener 22 of the present invention includes a threaded longitudinal shank 120 with a protuberance or head 122 laterally extending therefrom. Head 122 is defined by an upper surface 124, a lower and substantially parallel surface 126 and a cylindrical peripheral surface 128. A lower peripheral edge 130 is located at the intersection of lower surface 126 and peripheral surface 128. Upper surface 124 of fastener 22 further has a hexagonal shaped wrench receiving depression 132 formed centrally therein. 
     When die 20 is inserted within cavity 90 of die shoe 24, and dowl 102 is inserted within duct 98, shank 120 of fastener 22 is threadably engaged with shaft 94. Concurrently, lower peripheral edge 130 of head 122 is snugged against tapered surface 62 of recess 60 at contact points 152 and 154. Thus, fastener 22 serves to secure die 20 against die shoe 24. Preferably an M4×0.7×8 mm socket, low head, cap screw is used for fastener 22. Other size screws may also be employed. Counterbore 92 has a larger diameter than does peripheral surface 128 of fastener 22. Accordingly, peripheral surface 128 of fastener 22 contacts against counterbore 92 at contact point 160 when fastener 22 secures die 20 to die shoe 24. Counterbore 92 prevents excessive bending or healing of fastener 22 when secured. The two point contact of fastener 22 to die 20 causes self centering of die 20. 
     For the alternate embodiment die of FIGS. 2 and 6, the shank of fastener 22 is partially disposed within channel 80 of die 48 when secured. The retention apparatus construction described heretofore also applies to the punch 26 and punch holder 28 shown in FIGS. 1 and 2. 
     Another alternate embodiment of the present invention apparatus is shown in FIG. 5. In this embodiment, a #6-32 screw 172 has a head 174 and a longitudinal shank 176. Head 174 is defined by an upper surface 178 and a tapered peripheral surface 180. A longitudinal peripheral edge 182 is defined at an intersection between tapered surface 180 and upper surface 178. Screw 172 serves to secure die 20 to die shoe 24 in a manner similar to that of the preferred embodiment. FIG. 5 further shows an interlocking leakproof joint 200 formed between two sheets of material 202 and 204. Such a joint 200 is formed between drawing punch 22 and die 20 of any of the previously disclosed embodiments. 
     While the preferred embodiment of the apparatus for retaining tools has been disclosed, it will be appreciated that various modifications may be made without departing from the present invention. For example, the recess within the tool may be defined by many other shapes. Similarly, the fastener protuberance may have many alternate shapes and may even be a portion of the fastener other than the head thereof. It will also be appreciated that a plurality of recesses and fasteners may be employed to retain a single tool. Also, a dowl may not be required. Noncircular tools may also use the retention device of the present invention. Various dimensions have been disclosed in an exemplary fashion, however, other dimensions and fastener types may of course be employed. 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.