Abstract:
A steel rule cutting die having a slotted die backing board fabricated from wood with a laser burned slot therein and a steel rule in the slot, the steel rule having integral projections on its opposite side faces for engaging the walls of the slot, thereby precluding lift out of the steel rule from the slot.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The invention relates to cutting dies having steel rules for cutting and shaping cardboard and other stock.  
           [0003]    2. Description of Related Art  
           [0004]    It is standard practice to fit a steel rule into a slot provided in a wood base, the rule being held in the slot by friction or by shims forced into the slot or by other means bearing against the base of the steel rule.  
           [0005]    The walls of slots conventionally cut by means of a jig saw are usually rough and provide some degree of holding force when the base of a steel rule is inserted into the slot.  
           [0006]    The practice of cutting the slots in the base by means of a jig saw has proven to be time consuming and expensive. Accordingly, the slots are now usually burned into the base by means of a laser, a faster and more economical approach.  
           [0007]    However, such laser burned slots are very smooth, so that they offer little or no holding force for gripping a steel rule inserted therein.  
           [0008]    Such laser burned slots fall to firmly hold the steel rule in the slot of the base and, in time, the rule eventually lifts out of the slot.  
         BRIEF SUMMARY OF THE INVENTION  
         [0009]    The invention hereof provides a means for firmly anchoring a steel rule in a laser burned slot in a base. Herein, the upright, opposing, planar faces of the lower portion of a steel rule are knurled or barbed to provide projections which, when the steel rule is inserted in the slot, penetrate the walls of the slot thereby precluding the rule from lifting out of or falling out of the slot. 
       
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VEIWS OF THE DRAWINGS  
       [0010]    [0010]FIG. 1 is a fragmentary plan view of a die backing board having a slot defining a pattern extending into its upper surface for receipt of a steel rule;  
         [0011]    [0011]FIG. 2 is a fragmentary elevational view of a steel rule embodying a first form of the invention;  
         [0012]    [0012]FIG. 3 is an enlarged, fragmentary, cross sectional view showing the steel rule of FIG. 2 engaged in the pattern slot of the die backing board of FIG. 1;  
         [0013]    [0013]FIG. 4 is a fragmentary elevational view of a steel rule embodying a second form of the invention;  
         [0014]    [0014]FIG. 5 is a fragmentary, elevational view of a steel rule embodying a third form of the invention; and  
         [0015]    [0015]FIG. 6 is an enlarged, fragmentary, cross sectional view showing the steel rule of FIG. 5 engaged in the pattern slot of a backing board.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0016]    Referring to FIG. 1, a die backing board  10 , fabricated from wood, is shown fragmentarily, and has a slot  12  therein which extends downwardly from its upper planar face.  
         [0017]    Slot  12  outlines the pattern of an item to be stamped from cardboard or other stock, in known manner, and is burned into the backing board as by a laser.  
         [0018]    While backing board  10  is shown to be flat in FIG. 1, it may have a curved profile in end elevation to follow the contour of a drum, not shown, on which it may be mounted, all as is well known in the art.  
         [0019]    A steel rule embodying a first form of the invention is shown in FIGS. 2 and 3 and is generally indicated by  14 . Rule  14  is inserted into slot  12  of backing board  10  to form a steel rule cutting die.  
         [0020]    Steel rule  14  is rectangular in elevation and has opposing, spaced, flat, parallel, upright side walls  16  and spaced, parallel, horizontally-extending upper and lower walls  20  and  22 , respectively.  
         [0021]    Side walls  16  incline inwardly at their upper ends to form a cutting edge, generally indicated by  26 , which may be a knife edge  24   a,  as shown in FIG. 3, or a saw tooth edge  24   b  as shown in FIG. 2.  
         [0022]    Approximately the lower half of each side wall  16  of steel rule  14  is knurled as at  26  to provide a series of small ribs or projections  26   a  which extend the length of each side wall.  
         [0023]    When steel rule  14  is inserted in slot  12  of backing board  10 , and bottom wall  22  of the steel rule is brought into contact with a lower end  28  of the slot, ribs or projections  26   a  of knurling  26  bite into side walls  30  of slot  12  whereby the steel rule is firmly anchored in the slot to insure against the steel rule lifting out of the slot.  
         [0024]    A steel rule embodying a second form of the invention is shown in FIG. 4 and is generally indicated by  114 .  
         [0025]    Steel rule  114  differs from steel rule  14  of FIGS. 2 and 3 only in that its upper and lower walls  120  and  122  respectively, define a radius to follow the profile of a curved backing board, not shown.  
         [0026]    Steel rule  114  has spaced, flat, parallel, upright side walls  116 , only one of which is shown in the drawing.  
         [0027]    Side walls  116  incline inwardly at their upper ends to form a cutting edge generally indicated by  124 , which may be a knife edge, now shown, or a saw tooth edge  124   b,  as shown in FIG. 4.  
         [0028]    Approximately the lower half of each side wall  116  is knurled as at  126  to provide a series of small ridges or ribs  126   a  which extend the length of steel rule  114 .  
         [0029]    As with steel rule  14  of the embodiment of FIGS. 2 and 3, when steel rule  114  is inserted in slot  12  of backing board  10 , and bottom wall  122  of the steel rule is bought into contact with a lower end  28  of the slot, ridges or ribs  126   a  of knurling  126  bite into side walls  30  of slot  12  whereby the steel rule is firmly enclosed in the slot to insure against the steel rule lifting out of the slot.  
         [0030]    A steel rule  214  embodying a third form of the invention is shown in FIGS. 5 and 6.  
         [0031]    Steel rule  214  has opposing spaced, flat, parallel, and upright side walls  216 , spaced, curved, parallel, upright side walls  216 , and spaced curved, parallel, upper and lower walls  220  and  222  respectively, each of which defines a radius to follow the profile of a curved backing board  210 .  
         [0032]    Side walls  216  incline inwardly at their upper ends to form a cutting edge, generally indicated by  224 , which may have an upper knife edge  224   a  as shown in FIGS. 5 and 6.  
         [0033]    Lower half portion of steel rule  214  is provided with a series of spaced, downwardly-extending, fingers  226 .  
         [0034]    Fingers  226  are generally triangular in elevation and are truncated at lower ends.  
         [0035]    The lower ends of fingers  226  together define lower wall  222  of steel rule  214 .  
         [0036]    Each side wall  216  of steel rule  214  is provided with a series of spaced parallel inclined grooves  226 ′ which extend transversely across each finger  226 .  
         [0037]    Grooves  226 ′ define a series of spaced, sharply pointed, upwardly directed barbs  226   a,  best seen in FIG. 6, which extend angularly outwardly from each side wall  216 .  
         [0038]    When steel rule  214  is inserted in a slot  212  of backing board  210  and bottom wall  222  of the steel rule is brought into contact with a lower end  228  of the slot, barbs  226   a  of fingers  226  bite into side walls  230  of slot  212 , whereby the steel rule is firmly anchored in the slot to insure against the steel rule lifting out of the slot.