Abstract:
The invention is a broadhead arrowhead. The broadhead arrowhead includes a ferrule, one end portion of which is tapered to a substantial point. One or more blade assemblies extend outwardly from the ferrule. Each blade assembly has a first substantially planar main surface portion disposed in a plane at least substantially parallel to a longitudinal axis of the ferrule and a second surface portion having a planar region offset at an angle to the plane of the main surface portion. A generally continuously curved region is disposed between and connecting the first and second portions, such that the blade assembly has an airfoil-type shape. Only the first planar portion of the blade assembly is coupled to the ferrule thereby allowing the second portion to flex during penetration of a target and achieve greater penetration depth.

Description:
RELATED APPLICATIONS  
       [0001]    The present invention is a continuation-in-part of previous U.S. patent application Ser. No. 10/178,243 by the same inventor filed Jun. 25, 2002 which is incorporated herein by reference. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    The present invention relates to the field of archery. Specifically, the invention relates broadhead arrowheads found on arrow devices.  
           [0004]    2. Description of the Prior Art  
           [0005]    Bowhunting and archery rely on arrows to achieve penetration of the intended target regardless of whether that intended target is a static bulls-eye or a hunted animal. The problem of target penetration has been addressed in several ways. For hunters, 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 De 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 harvesting 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.  
           [0006]    Unfortunately, these broad, flat blades have a pronounced aerodynamic effect that can radically affect the overall stability of the arrow in flight and significantly reduce the precision of flight. Since the majority of hunting tips are broadhead in design, the combined effect of broadhead and fletching and/or vanes at opposite ends of an arrow may not promote a stable flight.  
         SUMMARY OF THE INVENTION  
         [0007]    The present invention is a continuation in part of previous U.S. patent application Ser. No. 10/178,243 by the same inventor filed Jun. 25, 2002. application Ser. No. 10/178,243 describes a broadhead arrowhead system wherein a plurality of blades, each including an airfoil design, provides excellent rotation of the arrow shaft during flight without producing a large amount of aerodynamic drag.  
           [0008]    A key feature of the present invention is the design of the airfoil blades, wherein the trailing portion of each blade is attached only to the leading portion of each blade and not to the main body or ferrule. When fired into a target, this design enables the flexible blade to collapse as it enters the target such that the leading and trailing portions of each blade are substantially coplanar during penetration. This flexing enables greater penetration than would be available with a rigid airfoil blade design. The invention is compatible with all contemporary arrow shafts.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]    [0009]FIG. 1 shows a side perspective of the broadhead arrowhead of the present invention.  
         [0010]    [0010]FIG. 2 shows a front-end view of the broadhead arrowhead looking rearwardly from the forward end of the arrowhead.  
         [0011]    [0011]FIG. 3 shows a side detail view of the broadhead arrowhead.  
         [0012]    [0012]FIG. 4 shows a detailed view of one of the blade assemblies of the arrowhead.  
         [0013]    [0013]FIG. 4A shows the curvature of the blade assembly at three sections taken along section lines “A-A”, “B-B”, “C-C”, respectively, in FIG. 4.  
         [0014]    [0014]FIG. 5 shows the broadhead arrowhead mounted to an arrow shaft. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0015]    The present invention is a continuation in part of previous application Ser. No. 10/178,243 by the same inventor. The content of the previous application is incorporated by reference and recited herein.  
         [0016]    With reference to FIGS. 1 through 5, the broadhead arrowhead of this invention comprises a body or ferrule  102 . At a first, or proximal, end, ferrule  102  incorporates a first end portion  104 . First end portion  104  typically tapers to a point  105 . Ferrule  102  also has a second, or distal, end portion  106 . Second end portion  106  may be slightly flared outwardly. It is not necessary that second end portion  106  be flared outwardly, however. In some embodiments, second end portion  106  may continue substantially straight to the rear end of body  102 . Ferrule  102  is typically symmetrical about a longitudinal axis  118  between first end portion  104  and second end portion  106 .  
         [0017]    A mounting stub  108  extends rearwardly from second end portion  106  of arrowhead body  102 . Typically, stub  108  is symmetrical about and coaxial with longitudinal axis  118 . Mounting stub  108  is intended to fit into a mating recess typically located at one end of a standard arrow shaft. Stub  108  may be threaded to mate with matching threads in the arrow shaft recess or it may be seated in the recess in a press fit arrangement. Alternatively, mounting stub  108  may be glued or otherwise sealed into the mating recess of the arrow shaft.  
         [0018]    In other variations of mounting means, instead of a stub  108 , second end  106  of body  102  may be hollowed out to fit over an arrow shaft. In such an arrangement, the inside of hollow second end  106  may be threaded to mate with threads on the outer surface of the arrow shaft; or distal second end  106  may be press fit over the arrow shaft. Alternatively, second end  106  may be fitted over the end of the arrow shaft and glued or otherwise sealed to the arrow shaft.  
         [0019]    One or more blade assemblies  110  extend laterally outwardly from ferrule  102 . Preferably the arrowhead is constructed with two, three, or four blade assemblies. Typically, if two blade assemblies are used, they are disposed substantially diametrically opposite each other about longitudinal axis  118  of ferrule  102 . Three blade assemblies are typically disposed at angles of approximately 120° around longitudinal axis  118 . Correspondingly, four blade assemblies  110  are typically mounted at 90° angles relative to each other about horizontal axis  118 .  
         [0020]    Blade assembly  110  is shown in detail in FIGS. 1 and 4. Each blade assembly  110  comprises a first substantially planar blade assembly portion  112  and a second substantially blade assembly portion  114 . A leading edge  113  of first portion  112  is typically sharpened to better allow the arrowhead to penetrate a target. First blade assembly portion  112  may comprise a solid substantially flat planar portion or optionally may have a cutout section  116 . Second blade assembly portion  114  extends rearwardly from first blade assembly portion  112  at an angle thereto. Second blade assembly portion  114  is preferably curved, with a radius of curvature optimally between about 0.2″ and 0.5″, giving the blade the characteristics of an airfoil. The radius of curvature may vary over the surface of the blade. A trailing edge  119  of the blade is at an angle to arrowhead body  102 . This angle may be as great as 45 degrees or more, but optimally it increases from approximately 5 degrees to approximately 35 degrees at the blade tip. The blades, acting together, form an axial-flow turbine.  
         [0021]    As shown in FIG. 3, second blade assembly portion  114  is joined to first blade assembly portion  112  by a continuously curved region  120 . The radius of curvature of region  120  is in the range of between about 0.2″ and 0.5″. An angle θ generally defines the angle between first planar portion  112  and second planar portion  114 . This angle θ is in the range of between about 5 degrees and 25 degrees. This configuration gives the blade assembly an airfoil-type shape. The length of first substantially planar portion  112  is between about 50% and 80% of the total length of blade assembly  110 . Correspondingly, second substantially planar portion  114  comprises between about 20% and 50% of the total length of blade assembly  110 . It will be understood by those skilled in the art that where the arrowhead has more than one blade assembly  110 , each second blade assembly portion  114  is preferably angled relative to each corresponding first blade assembly portion  112  in the same direction and at substantially the same angle for each blade assembly  110 .  
         [0022]    Alternatively, first planar portion  112  and second angled portion  114  may be joined at a more sharply defined angle θ with a radius of curvature close to or at “0”. However, this alternative configuration does not produce the same high quality of aerodynamic effects as does the airfoil shape shown in FIG. 3.  
         [0023]    [0023]FIG. 4A shows the curvature of the blade assembly  110  at three sections taken along section lines “A-A”, “B-B”, “C-C”, respectively, in FIG. 4.  
         [0024]    Arrowhead body  102  and blade assemblies  110  may be made of any suitable material, such as, but not limited to, steel, aluminum, plastic, etc. As shown in FIG. 4, first planar portion  112  of blade assembly  110  has a short extension  117  that fits into a slotted opening in body  102 . Extension  117  extends from the inner edge of first planar portion  112  substantially up to but just short of curved region  120 . Extension  117  may be glued, welded or soldered into the slot of body  102 . Alternatively, blade assembly  110  and body  102  may be integrally formed as by molding. Other techniques for securing blade assembly  110  to body  102  would be apparent to those skilled in the relevant arts.  
         [0025]    In summary, each blade assembly  110  comprises a substantially flat first planar portion  112  extending laterally outwardly from body  102  and substantially parallel to longitudinal axis  118 . A second blade assembly portion  114  is angled at an angle of between about 5° and 25° out of the plane of first planar portion  112  away from alignment with axis  118  and at an angle of between about 5° and about 45° to the ferrule body  102 . FIG. 2 shows second end portions  114  of each blade angles slightly clockwise relative to the major plane of first planar portion  112 . Alternatively, second end portions  114  can be angled slightly counterclockwise relative to the major plane of first planar portions  112 .  
         [0026]    In the embodiment shown, each blade assembly  110  has the general shape of a substantially triangular or delta wing configuration. In other embodiments, blade assembly  110  can have the general shape of a swept wing or a straight wing.  
         [0027]    Much like the control surfaces of an aircraft wing, the ratio of angled portion length to overall blade assembly length can be relatively small. For example, in one embodiment, the ratio of the length of angled second portion  114  to the overall length of blade assembly  110  is in the range of between 10% and 50%, and preferably between about 20% and 50%.  
         [0028]    Each blade of the broadhead arrowhead incorporates a substantially similar airfoil that produces a rotational torque about longitudinal axis  118 . In flight, these forces induce a rapid rotation of the arrow about longitudinal axis  118  while minimizing aerodynamic drag. The plane of each blade assembly  110  remains parallel to the shaft of the arrow along its cutting edge  113 .  
         [0029]    One of the features of the arrowhead of this invention is its ability to produce stabilized arrow flight without the use of fletching or tail fins (or feathers). FIG. 5 shows the broadhead arrowhead of this invention mounted to an arrow shaft  122  without fletching. Tests have shown that an arrow using the broadhead of this invention without fletching tracks true in flight and does not deviate significantly from the planned flight course. This is due to the rotation induced in the arrow by the aerodynamically designed broadhead blades, which is sufficient to stabilize the arrow in flight. Eliminating or reducing the size of the fletching in fact improves flight characteristics because the rotational drag normally induced by the fletching is avoided. It should be noted, however, that the arrowhead of the invention can be used with fletched arrow shafts as well.  
         [0030]    A key feature of the present invention is the ability of curved region  120  and second planar portion  114  to flex during penetration due in part to the fact that second planar portion  114  and continuously curved region  120  are only integral with first planar portion  112  and not directly integral with body  102 . In the preferred embodiment there is in fact a slight gap  130  between the combination of second planar portion  114  plus curved region  120  and body  102  as shown in FIG. 1. Being manufactured from rigid yet flexible material, such as stainless steel, the blade assemblies  110  of the present invention retain their airfoil shape during release and flight. Aerodynamic forces exerted on blade assemblies  110  during flight are not sufficient to flex second planar portion  114  nor to change angle θ. During impact, first planar portion  112  enters perpendicular to the target as with any conventional broadhead. As the arrow decelerates, the flexible blade of the present invention collapses such that the angle θ approaches zero degrees as a result of physical contact pressure on the top and bottom surfaces of blade assemblies  110  exerted by the penetrated target. Thus as the arrow decelerates completely, first planar portion  112  and second planar portion  114  become substantially coplanar. This flexing enables greater penetration than would be possible if second planar portion  114  was held in a completely rigid airfoil geometry by attachment to both first planar portion  112  and to body  102 . Such an inflexible broadhead must corkscrew into the target wasting kinetic energy and inhibiting complete penetration of the arrowhead.  
         [0031]    An additional benefit of the flexible blade assemblies  110  of the present invention is an increased probability that the arrow will remain buried in the target. Attempts to remove the arrow relieve the physical pressure on flattened second planar portion  114  thereby enabling it to spring back to its airfoil shape, due to the shape memory of materials such as stainless steel, and inhibit backing out through the same entry path. An arrow that remains buried in a hunted animal debilitates more than just the entry wound itself. In order to forcefully remove the arrowhead of the present invention, an animal would greatly expand the extent of the wound and only further increase the probability of its own demise.  
         [0032]    While various embodiments of the present invention have been described above, it should be understood that they have been presented by way of example only, and not limitation. Thus, the breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.