Abstract:
The present invention is a system of locking arrow blades that provide excellent main shaft rotation without producing a large amount of aerodynamic drag. This system, including a plurality of v-shaped blades, is attached to the forward end of any conventional arrow shaft or integral to the forward end of any conventional arrow shaft.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to the field of archery. Specifically, the invention relates to the blades found on arrow devices. 
     2. Description of the Prior Art 
     Bowhunting and archery rely on arrows to have two key properties. First, arrows must achieve penetration of the intended target regardless of whether that intended target is a static bulls-eye or a hunted animal. Second, arrows must fly straight and true. Even the most skilled of archers, with the most trained eyes, can not compensate for an arrow that can not find its intended mark. These two great needs are somewhat at odds with one another. 
     Historical solutions have sought to balance these two needs in order to minimize the detrimental effects of each while maximizing the overall result. 
     The problem of target penetration has been addressed in several ways. Target penetration can be directly correlated to the likelihood of hunting success: an arrow that can not adequately penetrate an intended animal is of little use to a hunter. The overall mass of the arrow could be increased, but more massive arrows are clumsy and must be fired in a high arc to reach the intended target. Simple “field point” arrow tips can provide adequate penetration for straw targets in competition, but they are not very effective for killing hunted animals. Prior art broadhead arrows were invented to increase effective hunting penetration and success potential. Typically two to four flat, triangular blades are arranged around the forward pointed tip. As the tip enters the intended target, the blades slice a region much greater than the diameter of the arrow shaft. Unfortunately, these broad, flat blades have a pronounced aerodynamic effect that can radically impact the overall stability of the arrow in flight and significantly reduce the precision of flight. 
     Fletching, or other guidance fins, were added to the aft end of prior art arrows. Typically, two to four fins are applied parallel to the long axis of the arrow surrounding the aft end. As the arrow sails through the air, these fins are intended to straighten the overall flight path by effectively pushing the tip of the arrow in the right direction. However, these same fins typically account for sixty percent of the overall aerodynamic drag experienced by the arrow in flight. Fins of reduced size have less drag but also provide less overall stability. Minimizing drag is important to increase overall range and speed at impact. 
     Broadhead blades are also easily damaged during use. Poorly anchored broadhead blades, which can be removed and replaced, may dislodge during impact with a target. If replaced blades are not perfectly symmetrical, i.e., misapplied, with respect to the remaining blades, then the arrow will not fly accurately. Conversely, permanently attached blades are always symmetrical, but they can not be replaced at all without replacing the entire arrow head assembly. 
     SUMMARY OF THE INVENTION 
     The present invention is a system of locking arrow blades that provide excellent main shaft rotation without producing a large amount of aerodynamic drag. A system including a plurality of v-shaped blades is attached to the forward end of any conventional arrow shaft or integral to the forward end of any conventional arrow shaft. The invention is compatible with all contemporary arrow shafts. 
     The individual blades of this novel system include two key features. A first key feature of the present invention is the geometry of the blades wherein the leading edge of each blade is parallel to the long axis of the arrow shaft, and the trailing edge of each blade is deflected out of the plane of the blade in a smooth, continuous arc. All blades of the present invention are identical with all deflected portions facing the same direction when the arrow is viewed down its long axis. In flight, the arrow rotates as a result of airflow over the deflected portion of the blades much as the control surface on an aircraft wing changes the direction of the aircraft if said control surface is deflected out of the major plane of the aircraft wing. However, said blades being fashioned of smooth metal create little aerodynamic drag. The second key feature of the present invention is the robust manner in which each blade locks into the assembly, thereby providing simple, positive, accurate removal and installation of replacement blades. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a two-dimensional view of an arrow blade of the present invention, depicting all the elements of said blade. 
     FIG. 2 is first view of the three-dimensional blade of the present invention. 
     FIG. 3 is a second view of the three-dimensional blade of the present invention. 
     FIG. 4 is a third view of the three-dimensional blade of the present invention. 
     FIG. 5 is a side view of the arrow head body of present invention. 
     FIG. 6 is an oblique view of the assembled invention. 
     FIG. 7 is a rear-facing view of the body of the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 is directed to one of the plurality of removable/replaceable blades of the present invention as shown in two dimensions. Arrow blade  1  consists of a trapezoidal major portion  2  and an irregularly shaped minor portion  3 . Major portion  2  and minor portion  3  are separated from one another by longitudinal fold  4 . 
     The aft part of major portion  2  further comprises an extended control surface  6  that is continuous with the remainder of major portion  2  and contributes to the overall trapezoidal geometry of major portion  2 . Control surface  6  is deflected out of the plane of the remainder of major portion  2  in order to direct air flow over arrow blade  1  in a manner that causes the entire arrow to rotate. Control surface  6  extends longitudinally substantially beyond the length of minor portion  3  in the preferred embodiment. The leading edge  15  of major portion  2  is sharpened and slopes continuously up from fore to aft of arrow blade  1 . 
     The aft part of minor portion  3  further comprises a radially extended, sharp-edged triangular minor blade  5 . Minor blade  5  is greatly reduced in size relative to either major portion  2  or control surface  6  in order to minimize interaction with the rotational airflow generated by control surface  6 . Minor blade  5  and the remainder of minor portion  3  are coplanar in the preferred embodiment. 
     FIGS. 2-4 describe the three-dimensional geometry of arrow blade  1  once it is formed into its final configuration. FIGS. 2 and 4 show major portion  2  and minor portion  3  bent along fold  4 . In this exemplary embodiment, elements  2  and  3  are bent to a 60-degree “V” shape. FIGS. 3 and 4 show control surface  6  arched out of the plane of major portion  2 . In order for the system of the present invention to function correctly, all blades must be formed into the same three-dimensional geometry. Arrow blade  1  may be manufactured from any material known in the art of producing arrow blades. The preferred material is steel due to its ability to maintain a keen edge, its high strength to weight ratio, and its ability to retain a folded shape. 
     FIG. 5 depicts the main body of the present invention. Arrowhead body  8  comprises a main cylindrical housing  9  which further comprises a male-threaded forward end  10  and a flared trailing end  11 . Said forward end  10  is of slightly reduced diameter so that when a conical, female-threaded tip  12  is attached, the maximum diameters of tip  12  and cylindrical housing  9  are equal. Trailing end  11  is flared so that the maximum diameter of trailing end  11  is equal to the maximum diameter of the arrow shaft (reference only). Aft of trailing end  11 , and integral with the rest of arrowhead body  8  is a coupling means  13  which attaches the present invention to a prior art arrow shaft. Typically, coupling means  13  will be a male-threaded cylinder of the type well known in the art of attaching arrowheads to arrow shafts. However, coupling means  13  could also easily be a press/friction fit or a cylindrical mating surface of slightly reduced diameter attached to the prior art arrow shaft by any mechanical bonding means such as adhesives or pinning. Arrowhead body  8  may be manufactured from metal, plastic, ceramic, or composite materials. 
     A plurality of longitudinal channels  14  extend from the forward-most surface of forward end  10  completely through forward end  10  and through approximately 75% of the length of cylindrical housing  9 . Said channels  14  extend to a depth in cylindrical housing  9  equal to the length of minor portion  3 . There must be an even number of channels  14  in order to accept the folded arrow blades also of the present invention. The exemplary embodiment of the present invention includes six channels  14  capable of employing three folded arrow blades. The blades must therefore be folded along fold  4  such that elements  2  and  3  are bent to a 60-degree “V” shape. In an alternative embodiment including only four channels, the blades must be folded along fold  4  such that elements  2  and  3  are bent to a 90-degree “V” shape. As a rule, the number of channels  14  is equal to twice the number of arrow blades  1 , and the angle between elements  2  and  3  is equal to 360° divided by twice the number of arrow blades  1 . 
     The width of channels  14  must be equal to the thickness of arrow blade  1  so that each of said arrow blades  1  can be slid down into two adjacent channels  14  in cylindrical housing  9 . Minor portion  3  must have a height equal to or greater than the depth of longitudinal channels  14  in order to properly lock each blade in place. In the preferred embodiment, minor portion  3  is of a height equal to the depth of channels  14  with the exception of minor blade  5  which extends further radially outward. Once all arrow blades are installed, i.e., all channels are filled, tip  12  is screwed down over forward end  10  to complete the assembly. FIG. 6 shows a completed assembly  16  of the present invention. 
     The embodiments described herein are meant to be exemplary of the present invention and not limiting in scope.