Abstract:
An auxiliary cutting implement for attachment between a broadhead and arrow shaft includes preferably two or more coils each having two cutting edges formed along their opposite elongated side edges. As the coils pass through the animal they unroll and slice through animal flesh in all directions. The coils are biased toward their rolled position which increases the multi-directional movement of the coil and cutting edges through the animal resulting in a large cutting area and fast kill as compared to the broadhead alone.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to arrows having a detachable arrowhead, and more particularly relates to an auxiliary cutting implement configured to attach between the arrow shaft and arrowhead. 
     Bow hunting utilizes an arrow fired at an animal target with the arrow having a pointed arrowhead to penetrate and kill the animal. Modern day arrowheads include the so-called “broadhead” having either fixed or movable blades with usually 2 to 4 single edge blades arranged in a radially spaced pattern about the broadhead center shaft. The purpose of the blades is to increase the cutting area as the arrowhead penetrates and moves through the animal leading to a hopefully fast kill. The cutting area may be considered in terms of cutting diameter and a common broadhead provides a cutting diameter of about 2 inches or less. 
     Broadheads include a threaded shaft opposite the tip allowing the hunter to removably thread the broadhead to a threaded opening formed in the end of the arrow shaft opposite the cocked end. There is a large variety of broadheads on the market today with prices ranging anywhere from about $10 to about $50 or more. Some of the mechanical (movable blade) broadheads allow replacement of the blades as necessary. The replacement blades may cost anywhere from a few dollars to about $10 or more. 
     In all broadhead designs, a primary concern is aerodynamics—how it travels in flight in terms of speed and flight path. Since the broadhead blades extend radially of the arrow shaft, the blades necessarily introduce a deviation from the aerodynamics of an arrow without radially extending blades. The broadheads must therefore be designed with aerodynamic effect in mind; however, the design which might be best aerodynamically may not necessarily be the best design in terms of cutting paths and diameters, and vice versa. Designers of broadheads must therefore always be weighing their blade designs against the two, often conflicting parameters of aerodynamic effect and cutting pattern. 
     While present day broadheads are widely popular with bow hunters, the broadheads and replacement blades are expensive and are becoming maxed out in their cutting size due to the aerodynamic concerns which discourage designers from pursuing broadhead designs with any significant increase in presently offered cutting sizes. 
     SUMMARY OF THE INVENTION 
     The present invention addresses the above needs by providing an auxiliary cutting implement which is not part of the broadhead but rather is an attachment which is mounted between the arrow shaft and detachable broadhead. 
     In an embodiment, the present invention provides an auxiliary cutting implement having at least one, but preferably two or more cutting coils radially extending from a center fitting having a hole wherethrough the threaded end of a broadhead may pass. The threaded end of the broadhead is then threaded into the threaded hole formed in the end of the arrow shaft in the usual manner thereby securing the auxiliary cutting implement therebetween. 
     The auxiliary cutting implement may be formed as a unitary part where the center fitting and coils are cut or otherwise formed as a single part. The auxiliary cutting implement may be made from sheet metal such as stainless steel or carbon steel having a thickness providing flexibility and spring memory into the coils cut therefrom. In one embodiment, the auxiliary cutting implement is cut from the metal stock with a central fitting in the shape of a washer with two or more elongated strips which are spaced about and extend radially outward of the central fitting. The strips are each formed in an elongated, generally rectangular shape having first and second opposite elongated side edges. These side edges form the cutting edges and there are thus two cutting edges per strip/coil. This contrasts with a broadhead which provides only a single cutting edge per blade. 
     The strips are then bent downwardly at the point where they extend from the central fitting and are formed into coils. When mounted between an arrow and broadhead as described above, the arrow is fired with the coils imparting no adverse effects on the arrow aerodynamics. 
     Once the broadhead penetrates the animal, the coils, which trail behind the broadhead blades, unroll as they encounter the force imparted by skin, flesh and organs. As the coils first strike the animal, they utilize substantially all the potential energy within the arrow at the time of impact. The level of potential energy produced at the time of arrow release is in proportion to the power of the bow. This potential energy is discharged in part by the aerodynamic drag and in part by the coils in the form of cutting and tearing. Without the coils, much of the potential energy is wasted as the arrow without coils passes through the animal and then continues to travel for a long distance. While the arrow used with coils still passes through the animal, it only then travels a few more feet as the potential energy is used up faster due to the coil action. 
     The cutting edges formed on either edge of the coil strips slices through the animal. Since the coils have shape memory they are biased toward the coil position such that they transition from the initial coil position toward a fully unrolled position and bias back toward the coil position. As the coil transitions in this manner as it travels through the animal, the cutting edges of the coils slice through the flesh in all directions producing a cutting area which is significantly greater than that produced by the broadhead blades themselves. Such a large cutting area with no adverse aerodynamic effect has never before been realized and the present invention thus provides a significant advance in the art. 
    
    
     
       DESCRIPTION OF THE DRAWING FIGURES 
       The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become apparent and be better understood by reference to the following description of the invention in conjunction with the accompanying drawing, wherein: 
         FIG. 1  is a perspective view of a prior art arrow; 
         FIG. 2  is a perspective view of a prior art broadhead; 
         FIG. 3  is a perspective view of a roll of sheet metal from which the auxiliary cutting implements may be made; 
         FIG. 4  is a plan view of a three coil embodiment prior to formation of the strips into coils; 
         FIG. 5  is a plan view of a four coil embodiment prior to formation of the strips into coils; 
         FIG. 6  is a perspective view of an embodiment of a three coil auxiliary cutting implement; 
         FIG. 7  is a perspective view of another embodiment of a three coil auxiliary cutting implement; 
         FIG. 8  is a perspective view of a mechanical drawing of another embodiment of a three coil auxiliary cutting implement; 
         FIG. 9  is a perspective view of an embodiment of a four coil auxiliary cutting implement; 
         FIG. 10  is a perspective view of another embodiment of a four coil auxiliary cutting implement; 
         FIG. 11  is a fragmented, perspective view of another embodiment of a four coil auxiliary cutting implement mounted to an arrow and prior to firing the arrow; and 
         FIG. 12  is a fragmented, perspective view of an embodiment of the four coil auxiliary cutting implement following firing of the arrow to which it is mounted and removal from the stricken animal. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring now to the drawing figures, there is seen in  FIG. 1  a common prior art arrow  10  including an arrow shaft  12  having first and second ends  12   a  and  12   b  with an arrow nock  14  attached to first end  12   a  and an arrowhead in the form of a target point  16  attached to second end  12   b . Fletchings  18  located adjacent nock  14  provide the aerodynamics allowing for a substantially straight flight path upon firing the arrow  10  from a bow (not shown). Arrows may have permanently mounted arrowheads or removable arrowheads which allow the archer to interchange arrowheads upon the arrow shaft as desired. 
       FIG. 2  illustrates a typical broadhead type of arrowhead that is popular with hunters. The broadhead  20  shown in  FIG. 2  is referred to as a mechanical broadhead in that the blades  22   a ,  22   b  thereof are movable from a closed position (not shown) to the open position shown. Blades  22   a ,  22   b  include respective elongated slots  22   a ′,  22   b ′ which are mounted on a common pin  24  allowing the blades to slide on the stationary pin and come to rest within respective longitudinal grooves  26   a  and  26   b  formed in the broadhead main body  26 . The distal end of broadhead  20  includes a pointed tip  28  while the proximal end includes a threaded shank  30  allowing broadhead  20  to be removably mounted to the end of an arrow opposite the nock end. For example, in the arrow  10  of  FIG. 1 , the plain target point  16  may be removed from shaft  12  and replaced with broadhead  20  by threading threaded shank  30  into a threaded hole (not shown) provided at end  12   b . The threaded hole may be formed directly into the shaft or it may be provided as a separate insert as is known to those familiar with archery and particularly bow hunting. 
     As explained in the Summary of the Invention, designers of broadheads attempt to maximize the cutting capability of the broadhead blades without negatively impacting aerodynamic performance which has necessarily imposed limitations on the cutting area present day broadheads can provide. The present invention obviates these design limitations by providing an auxiliary cutting implement which is not part of the broadhead but rather is an attachment which is mounted between the arrow shaft and a detachable broadhead of any desired design (e.g., fixed blade, mechanical blade, double blade, triple blade, etc.). 
     Referring to  FIGS. 3-5 ,  FIG. 3  shows an example of a roll of sheet metal  30  from which the invention may be formed (e.g., by cutting or stamping). The type of material chosen may vary as desired but it preferably a metal that will have a spring bias (shape memory) upon bending prior to reaching the fatigue point of the metal. In an embodiment, the material may be full hard stainless steel shim stock in a sheet thickness of about 0.007 to about 0.010 inches. 
     A three coil auxiliary cutting implement may be cut from an unrolled segment  30   a  of material in the form seen in  FIG. 4  which includes a central annular fitting  40  having a center hole  42  and three elongated, generally rectangular strips  44   a ,  44   b  and  44   c  extending radially therefrom in a substantially equally spaced manner thereabout. 
     A four coil auxiliary cutting implement  51  may be cut from an unrolled segment  30   a  of material in the form seen in  FIG. 5  which includes a central annular fitting  50  having a center hole  52  and four elongated, generally rectangular strips  54   a ,  54   b ,  54   c  and  54   d  extending radially from central fitting  50  in a substantially equally spaced manner thereabout. 
     A three coil cutting implement is preferred for use with a three blade broadhead whereas a four coil cutting implement is preferred for use with a two blade broadhead. As such, the coils may be positioned in a location which aligns with the spaces between the blades to create symmetry which aids in aerodynamically balancing the arrow (see  FIG. 11  where two coils  54   a ′ and  54   b ′ are located in between blades  22   a  and  22   b  while the other two coils are located on the opposite side and again in between blades  22   a  and  22   b ). While a maximum of six coils is preferred, it is possible to further increase the number of coils beyond six if desired. 
     It may thus be realized that the auxiliary cutting implement may be formed as a unitary part where the central fitting and elongated strips are cut or otherwise formed into a single piece of material. Each elongated strip  54   a ,  54   b ,  54   c  and  54   d  includes respective first and second opposite elongated side edges  51   a , 51   b ,  53   a , 53   b ,  55   a , 55   b  and  57   a , 57   b . These side edges form the cutting edges and there are thus two cutting edges per strip/coil. This contrasts with a broadhead which provides only a single cutting edge per blade. The side cutting edges may be formed in any desired blade cutting edge and point style such as straight, serrated and tanto, for example. The side cutting edges may be formed at the initial cutting of material segment  30   a  or may be performed in a subsequent operation. 
     The strips are then preferably bent away from the plane P (seen best in  FIG. 8 ) of the central fitting  40  and  50  at the point where the strips extend from the central fitting  40  and  50  (e.g., using a mandrel), and are formed into individual coils (e.g., using a sheet metal curling tool such as a step brake press) as seen in  FIGS. 6-8  (three coils  44   a ′,  44   b ′ and  44   c ′) and  FIGS. 9-11  (four coils  54   a ′,  54   b ′,  54   c ′ and  54   d ′). Using the four coil embodiment to illustrate, auxiliary cutting implement  51  may be mounted between an arrow shaft  12  and broadhead  20  by passing threaded shank  30  through central fitting hole  52  and threading threaded shank  30  into the threaded hole (not shown) provided at arrow end  12   b . The arrow may then be fired with the coils imparting no adverse effects on the arrow aerodynamics. 
     Once the broadhead  20  penetrates the animal, the coils  54   a ′,  54   b ′,  54   c ′ and  54   d ′, which trail behind the broadhead blades  22   a  and  22   b , unroll as they encounter the force imparted by skin, flesh and organs. As the coils unroll, the cutting edges formed on either edge of the coil strips (two per coil) slices through the animal. Since the coils have shape memory they are biased toward the rolled coil position seen in  FIGS. 9-11  such that they transition from this initial rolled coil position toward a fully unrolled position and bias back toward the coil position.  FIG. 12  illustrates an actual four coil auxiliary cutting implement after removal from the animal. It can be seen the coils have unfurled and are between the rolled coil conditions seen in  FIGS. 9-11  and the fully unrolled conditions seen in  FIG. 5 . As the coil transitions from the rolled coil condition as it travels through the animal, the cutting edges  51   a , 51   b ,  53   a , 53   b ,  55   a , 55   b  and  57   a , 57   b  of the coils (there are a total of eight cutting edges in the four coil embodiment) slice through the flesh in all directions producing a cutting area which is significantly greater than that produced by the broadhead blades themselves. 
     While the invention has been shown and described with reference to certain preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as described.