CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to Provisional Patent Application No. 62/360,464, filed on Jul. 10, 2017, which is incorporated herein by reference in its entirety. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    Arrows have long been used for target archery and hunting. A conventional arrow has a shaft with fletching, a knock at one end to receive the bow string, and an arrowhead at the other end. Arrowheads used for hunting typically have one or more sharp cutting blades and a ferrule that retains the blades and connects them to the arrow shaft. 
       2. Description of the Related Art 
       [0004]    A common hunting arrowhead design includes a primary triangular shaped blade attached to a ferrule with the blade protruding wider than the arrow shaft on both sides and extending in front of the ferrule to form a pointed tip of the arrowhead. U.S. Pat. No. 2,137,014 issued on Nov. 15, 1938 to Arthur J. Brochu shows an arrowhead of this type. 
         [0005]    In this type of arrowhead, the primary blade typically has two straight cutting edges coming together at a one angle all the way to the tip. This can cause the blade to be long and narrow at the tip. The blade tip is relatively weak and commonly breaks when impacting hard objects such as bone. 
         [0006]    A secondary blade, much smaller and not extending to the tip, is commonly added to this type of arrowhead to create a second cut perpendicular to the primary blade. This cross-shaped cut opens up a bigger hole for blood to escape through the hide for better blood tracking as compared to a single primary blade alone. U.S. Pat. No. 2,829,894 issued on Apr. 8, 1958 to Edward J. Henkel shows this type of arrowhead with a secondary blade. In Henkel&#39;s design, the secondary blade is inserted through a slot in the ferrule and rear tabs snap into recesses in the ferrule. A common problem with secondary blades is that they become dislodged when impacting hard objects such as bone. 
       BRIEF SUMMARY OF THE INVENTION 
       [0007]    The present invention is an improved arrowhead for bowhunting. Furthermore, it is an arrowhead with improved blade strength and blade retention. 
         [0008]    A ferrule is included in the arrowhead and is used to connect the blades to the arrow shaft. The ferrule has an open slot and a closed slot perpendicular to each other. In the new arrowhead, a primary blade is contained in the open slot. The primary blade protrudes wider than the ferrule on both sides and extends in front of the ferrule to form a tip. A secondary blade is also included in the arrowhead and is contained in the closed slot. The two blades interlock by the use of notches along the edges of the two blades that fit together. A screw is included in the arrowhead and passes through the ferrule and the primary blade, thereby retaining both blades in a superior manner while also allowing the blades to be removed for re-sharpening or replacement. 
         [0009]    With the new arrowhead design, the primary blade has improved impact strength at the tip. The angle at the tip is larger than the angle on the remainder of the primary blade. This makes the tip shorter and wider as compared to a single angle blade, providing superior strength which is useful to reduce the potential for breaking when the tip strikes a hard object such as bone. In one exemplary preferred embodiment, the angle at the tip of the primary blade is in the range of 70-100 degrees with an edge length of 0.15 to 0.50 inches. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1  is a perspective view of the arrowhead in one embodiment of the present invention. 
           [0011]      FIG. 2  is a plan view of the arrowhead of  FIG. 1 . 
           [0012]      FIG. 3  is an elevation view of the arrowhead of  FIG. 1 . 
           [0013]      FIG. 4  is a perspective view of the ferrule of the arrowhead of  FIG. 1 . 
           [0014]      FIG. 5  is a plan view of the ferrule of  FIG. 4 . 
           [0015]      FIG. 6  is an elevation view of the ferrule of  FIG. 4 . 
           [0016]      FIG. 7  is a perspective view of the primary blade of the arrowhead of  FIG. 1 . 
           [0017]      FIG. 8  is a plan view of the primary blade of  FIG. 7 . 
           [0018]      FIG. 9  is a perspective view of the secondary blade of the arrowhead of  FIG. 1 . 
           [0019]      FIG. 10  is a plan view of the secondary blade of  FIG. 9 . 
           [0020]      FIG. 11  is an exploded view of the arrowhead of  FIG. 1 . 
           [0021]      FIG. 12  is a plan section view of the arrowhead of  FIG. 1 . 
           [0022]      FIG. 13  is an elevation section view of the arrowhead of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0023]    The following describes an arrowhead for hunting that is configured for addressing problems associated with the strength of an arrowhead including the strength of the primary blade tip and the secondary blade retention.  FIG. 1  is a perspective view of the arrowhead  10 . The arrowhead  10  components include a ferrule  11 , a secondary blade  12 , a primary blade  13 , and a screw  14 .  FIG. 2  is a plan view of the arrowhead  10  of  FIG. 1 . It can be seen in  FIG. 2  that the primary blade  13  protrudes wider than the ferrule  11 , extending to the first side widest point  15  and the second side widest point  16 . It can also be seen in  FIG. 2  that the primary blade  12  extends in front of the ferrule  11  forming a pointed tip  17 .  FIG. 3  is an elevation view of the arrowhead  10  of  FIG. 1 . From  FIG. 3 , it can be seen that the secondary blade  12  is oriented perpendicular to the primary blade  13 . 
         [0024]      FIG. 4  is a perspective view of the ferrule  11  of the arrowhead  10  of  FIG. 1 . The ferrule  11  includes a locating cylindrical base  25  with a diameter chosen such that the base  25  fits precisely inside an end of an arrow shaft, not shown. The ferrule  11  also includes a male threaded section  26  adjacent the base  25  which mates with threads inside the arrow shaft to hold it securely to the arrow shaft. The locating diameter and threads of the base  25  and threaded section  26  are standard in the archery industry for replacement point systems. 
         [0025]      FIG. 5  is a plan view of the ferrule  11  of  FIG. 4 . The ferrule  11  includes a closed slot  23  which creates a hole through the body of the ferrule  11 . This slot  23  is referred to as a closed slot since there is material on all sides of the slot as can be seen in  FIG. 5 .  FIG. 6  is an elevation view of the ferrule  11  of  FIG. 4 . The ferrule  11  also includes an open slot  24  which extends all the way to the tip  19  of the ferrule  11 . This slot  24  is referred to as an open slot since no material is enclosing the right end of the slot  24  as shown in  FIG. 6 . The open slot  24  is perpendicular to the closed slot  23 . The open slot  24  overlaps the closed slot  23  by an exemplary range of 50 to 90 percent of the closed slot&#39;s length L 4 . The width L 5  of the open slot  24  is 0.001 to 0.010 inches wider than the thickness of the primary blade. The width L 3  of the closed slot  23  is 0.001 to 0.010 inches wider than the thickness of the secondary blade. The length L 4  of the closed slot  23  is in the exemplary range of 0.15 to 0.50 inches. The length L 6  of the open slot  24  is in the exemplary range of 0.5 to 1.0 inches. The ferrule  11  also includes a threaded screw hole  27  that passes through the entire body of the ferrule  11  including the open slot  24 . The axis of hole  27  is perpendicular to the planar slot  24 . Hole  27  is spaced apart from and between the tip  19  of the body of the ferrule  11  and the closed slot  23 . The ferrule  11  has a length L 8  in the exemplary range of 1.2 to 2.0 inches. The ferrule  11  has a width L 7  in the exemplary range of 0.25 to 0.35 inches. The ferrule  11  would commonly be made from metal such as aluminum, titanium, or steel using a lathe or screw machine. 
         [0026]      FIG. 7  is a perspective view of the primary blade  13  of the arrowhead  10  of  FIG. 1 . The primary blade  13  is commonly made from a plate of metal such that it has a constant thickness of 0.045 to 0.100 inches except where material has been removed for instance by a stamping die process or by grinding the cutting edges to a sharp bevel of 15 to 30 degrees per side. The primary blade  13  includes a notch  31  and a hole  32 . The remaining holes through the blade shown in  FIG. 5  are included for weight reduction and could also be removed for this invention. The primary blade  13  is symmetrical about its centerline which passes through the point of the tip  17  and the hole  32  center. 
         [0027]      FIG. 8  is a plan view of the primary blade  13  of  FIG. 7 . A first set of cutting edges  41  and  42  starting at tip  17  form a first angle A 1 . A second set of cutting edges  43  and  44  form a second angle A 2 . The first angle A 1  starting from the blade tip  17  is larger than the second angle A 2 . The first angle A 1  is in the exemplary range of 70 to 100 degrees, but preferably about 80 degrees. The second angle A 2  is in the exemplary range of 25 to 60 degrees, but preferably about 45 degrees. The first set of cutting edges have a length L 1  and the second set of cutting edges have a length L 2 . Length L 1  is in the exemplary range of 0.15 to 0.5 inches, but preferably about 0.3 inches. Edge length L 2  can be adjusted to achieve a desired length and width of the arrowhead, but is preferably in the range of 0.6 to 1.0 inches. The length L 10  of the primary blade  13  is in the exemplary range of 0.9 to 1.4 inches. The width L 9  of the primary blade  13  is in the exemplary range of 0.9 to 1.5 inches. 
         [0028]      FIG. 9  is a perspective view of the secondary blade  12  of the arrowhead  10  of  FIG. 1 . The secondary blade  12  is commonly made from a plate of metal such that it has a constant thickness of 0.040 to 0.080 inches except where material has been removed for instance by a stamping die process or by grinding the edges to a sharp bevel of 15 to 30 degrees per side. The secondary blade  12  includes a notch  22  and two cutting edges  28  and  29 . 
         [0029]      FIG. 10  is a plan view of the secondary blade  12  of  FIG. 9 . The secondary blade  12  has a width L 12  in the exemplary range of 0.5 to 1.0 inches and a length L 11  in the exemplary range of 0.15 to 0.50 inches. The secondary blade  12  has an angle A 3  in the exemplary range of 60 to 110 degrees. 
         [0030]      FIG. 11  is an exploded view of the arrowhead  10  of  FIG. 1 .  FIG. 11  has dashed lines showing the positioning of the components during assembly. First, the secondary blade  12  is inserted into the closed slot  23  in the side of the body of the ferrule  11  until it is centered within the body of the ferrule  11  with the notch  22  facing toward the tip  19  of the body of the ferrule  11  and aligned with open slot  24 . The primary blade  13  is then inserted into the open slot  24  of the ferrule  11  (to be centered in the body of the ferrule  11  with the notch  31  centered in the open slot  24 ) from the tip  19  backward until the primary blade  13  contacts the back of the slot  24  and the notch  31  of the primary blade  13  interlocks with notch  22  of the secondary blade  12 . The screw  14  is then assembled into the screw hole  27  of the ferrule  11  passing through the hole  32  of the primary blade  13 . The screw  14  and the screw hole  27  both include threads which are not shown in this simplified view. 
         [0031]      FIG. 12  is a plan section view through the center of the arrowhead  10  of  FIG. 1  showing the components in their secured positions from this perspective. The screw  14  secures the primary blade  13  to the ferrule  11 . The notches of the primary blade  13  and secondary blade  12  interlock and mate at position  41 .  FIG. 13  is an elevation section view through the center of the arrowhead  10  of  FIG. 1  showing the components in their secured positions from this perspective. The screw  14  secures the primary blade  13  to the ferrule  11 . The notches of the primary blade  13  and secondary blade  12  interlock and mate at position  41 . Position  42  shows the location of the thread engagement on the screw  14  and the ferrule  11 . 
         [0032]    The above described embodiments include the preferred embodiment and the best mode of the invention know to the inventor.
The present invention is an improved arrowhead for bowhunting. Furthermore, it is an arrowhead with improved blade strength and blade retention. A ferrule is included in the arrowhead and is used to connect the blades to the arrow shaft. The ferrule has an open slot and a closed slot perpendicular to each other which receive a primary blade and a secondary blade. The two blades interlock by the use of notches along the edges of the two blades that fit together within the open slot. The primary blade has an angle at the tip that is larger than the angle on the remainder of the primary blade improving the strength at the tip of the arrowhead.