Abstract:
A mechanical broadhead arrowhead has moveable blades that deploy from a retracted in-flight configuration to an outward deployed configuration as the broadhead strikes the target. Once in the deployed configuration, the blades are locked to each other against the resistance of the target, but freely pivot about the ferrule. Accordingly, if one blade strikes an obstruction such as a solid bone, the blade assembly simply pivots out of the way without damaging the blade, deflecting the trajectory of the arrow, or halting its penetration into the target.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of Provisional Patent Application Ser. No. 61/372,734 filed Aug. 11, 2010. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    The present invention relates to the field of archery and in particular to broadhead arrowheads often referred to simply as broadheads. 
         [0003]    Broadheads having blades that are held in a retracted configuration during flight that are moved to a deployed, expanded position when the arrow strikes the target are well known in the art. These mechanical broadheads overcome the wind drag and stability problems associated with fixed-blade broadheads. Mechanical broadheads can be classified generally into two categories. Broadheads in which the movable blades are pivoted rearward of the center of the blade so that the blades are swept forward during flight are often referred to as “forward-deployed” mechanical broadheads. U.S. Pat. No. 6,217,467 to Maleski and U.S. Pat. No. 6,595,881 to Grace, Jr. et al. are examples of forward-deployed mechanical broadheads. In each case, because the blades are pivoted behind the center of the blade, as the blade strikes the target, a torque couple is generated about the pivot access which causes the blades to pivot outwards and backwards approximately 120 degrees to form the broadhead arrow tip. Forward-deployed mechanical broadheads have an advantage in that the deployment mechanism is simple and straightforward, however, they suffer from the disadvantage that since the blades must move through such a large angle, the reaction forces exert significant stress on the blades and hinge, and substantial impact energy is consumed by the deployment process. Prior art forward-deployed mechanical broadheads also suffer from the fact that in the deployed configuration, the blades are typically locked to the ferrule. Accordingly, if one blade strikes an obstruction, such as a heavy bone, the impact may deflect the arrow&#39;s trajectory, significantly reduce the depth of penetration into the target, and/or damage the blade. 
         [0004]    Mechanical broadheads in which the blades are pivoted forward of the center of the blade so that the blades are swept backwards during flight are often referred to as “rearward-deployed” mechanical broadheads. U.S. Pat. No. 6,270,435 to Sodaro discloses a rearward-deployed mechanical broadhead in which the blades are spring loaded toward the deployed configuration. The blades are retained for flight by a retaining ring that is dislodged during impact to allow the blades to move to their deployed configuration. U.S. Pat. No. 7,717,814 to Sanford discloses a rearward-deployed mechanical broadhead in which the blades are spring loaded toward the deployed configuration. The blades are held in the retracted configuration for flight by means of a catch that is released when a plunger element strikes the target. As can be determined from the foregoing, although rearward-deployed mechanical broadheads have the advantage of using less impact energy for deployment, they suffer from a high degree of mechanical complexity and cost. Prior art rearward-deployed broadheads also suffer from the fact that the blades in the deployed configuration are effectively locked to the ferrule by the deployment springs, and therefore, if a blade strikes an obstruction, the arrow is likely to be deflected, penetration significantly reduced, and/or the blade damaged. 
         [0005]    U.S. Pat. No. 6,910,979 to Barrie et al. discloses a rearward-deployed mechanical broadhead in which the blades translate rearward by the interaction with the target. As the blades translate rearward, they are cammed outward along a track that causes the blades to extend outward to a locked, deployed configuration. The mechanical broadhead of Barrie et al. is considerably less complex then the spring-loaded rearward-deployed mechanical broadheads of Sodaro and Sanford, however, because the blades of Barrie et al. in the deployed configuration are still locked to the ferrule, the Barrie broadhead suffers from the same vulnerability if a blade strikes an obstruction. 
       SUMMARY OF THE INVENTION 
       [0006]    The present invention comprises a mechanical broadhead in which the blades are held in a retracted configuration for flight and, upon impact with the target, move to a deployed configuration. According to an illustrative embodiment, the blades are substantially L-shaped and are pivoted about a common axis located near the bend in the L. During flight, the short leg of the L is exposed, while the long leg of the L is retracted within the body of the ferrule. Upon impact with the target, resistance from the target presses the exposed, short leg of the L backwards. This causes the short leg to lever the longer blade portion outward. As the blade portions move outward, locking tabs formed on each of the blades ride over each other then act as stops to prevent the blades from moving back into the retracted position. This effectively locks the blades in the deployed configuration relative to each other, but the blades remain freely pivotable about the ferrule. Thus, if one blade strikes an obstruction such as a solid bone, the blade assembly simply pivots out of the way without damaging the blade, deflecting the trajectory of the arrow, or halting its penetration. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         [0007]    The present invention will be better understood from a reading of the following detailed description, taken in conjunction with the accompanying drawing figures in which like references designate like elements and, in which: 
           [0008]      FIG. 1  is an exploded, perspective view of a mechanical broadhead incorporating features of the present invention; 
           [0009]      FIG. 2  is a perspective view of a moveable blade incorporating features of the present invention; 
           [0010]      FIG. 3  is a perspective view of the mechanical broadhead of  FIG. 1  with the blades in the retracted configuration; 
           [0011]      FIG. 4  is a perspective view of the mechanical broadhead of  FIG. 1  with the blades in the deployed configuration; 
           [0012]      FIG. 5  is a partial cross-sectional view of the mechanical broadhead of  FIG. 1  with the blades in the deployed configuration; 
           [0013]      FIG. 6  is a plan view of the mechanical broadhead of claim  1  striking an obstruction within the target; 
           [0014]      FIG. 7  is a cross sectional view of the mechanical broadhead of claim  1  being withdrawn from a target; 
           [0015]      FIG. 8  is a cross-sectional view of an alternative forward-deployed mechanical broadhead incorporating features of the present invention with the blades in the retracted configuration; and 
           [0016]      FIG. 9  is a cross-sectional view of an alternative forward-deployed mechanical broadhead incorporating features of the present invention with the blades in the deployed configuration. 
       
    
    
     DETAILED DESCRIPTION 
       [0017]    The drawing figures are intended to illustrate the general manner of construction and are not necessarily to scale. In the detailed description and in the drawing figures, specific illustrative examples are shown and herein described in detail. It should be understood, however, that the drawing figures and detailed description are not intended to limit the invention to the particular form disclosed, but are merely illustrative and intended to teach one of ordinary skill how to make and/or use the invention claimed herein and for setting forth the best mode for carrying out the invention. 
         [0018]    With reference to  FIGS. 1-6  and in particular,  FIG. 1 , a mechanical broadhead  10  incorporating features of the present invention comprises a ferrule  12  having a front end  14  and a rear end  16 . Front end  14  may be of any conventional shape such as conical, faceted, or ogival etc. with, or without a fixed blade, however, in the illustrative embodiment of  FIG. 1 , front end  14  has an ogival contour and includes a fixed blade  18  which is secured to ferrule  12  by means of threaded fastener  20 . Rear end  16  of ferrule  12  is adapted to be attached to an arrow shaft for example by means of threads  22  formed in rear end  16  of ferrule  12 . Ferrule  12  may be formed of any suitable material such as steel, titanium, composite or plastic, but in the illustrative embodiment is formed of a lightweight aluminum alloy. 
         [0019]    Ferrule  12  includes a slot  24  that extends diametrically through ferrule  12  for a majority of the length of the cylindrical portion  26  of ferrule  12 . Pivoting blades  28 ,  28   a  are pivotably secured within slot  24  by means of shaft  30  which is threaded or pressed into aperture  32  formed in ferrule  12  and which registers in journals  34 ,  34   a  formed in pivoting blades  28 ,  28   a.    
         [0020]    With particular reference to  FIG. 2 , pivoting blade  28  comprises a substantially L-shaped blade formed of steel or other suitable material comprising a longer blade portion  36  and a shorter lever portion  38  extending away from the hub portion  40  containing journal  34 . The forward edge  42  of blade portion  36  is beveled preferably to a razor sharp edge to facilitate penetration into the target. The leading edge  44  of lever portion  38  is beveled to reduce wind resistance but preferably is left somewhat dull. Leading edge  44  is preferably left dull so that it does not penetrate the target by itself, but instead the target resistance against leading edge  44  causes lever portion  38  to lever blade portion  36  outward as mechanical broadhead  10  impacts the target. Pivoting blade  28  further includes a locking tab  46  which extends below lower surface  48  of the remainder of pivoting blade  28  a sufficient amount to lock the pivoting blades together as described more fully hereinafter, but preferably about 0.005 to 0.025 inch and most preferably about 0.015 inch. Locking tab  46  includes a beveled region  50  that terminates in an edge  52  which lies substantially along a radial line extending from the center of journal  34 . Pivoting blade  28  further includes a locking aperture  54  the function of which will be explained more fully hereinafter. 
         [0021]      FIG. 3  shows mechanical broadhead  10  in the flight configuration with pivoting blades  28 ,  28   a  in their retracted, in-flight configuration with the blade portions  36  substantially concealed within slot  24  formed in ferrule  12 . A frangible retainer such as a rubber band, piece of thread, etc. may optionally be placed in groove  56  to retain pivoting blades  28 ,  28   a  in the retracted configuration during flight. Alternatively, ferrule  12 , pivoting blades  28 ,  28   a  and/or shaft  30  may be configured to provide sufficient friction to retain pivoting blades  28 ,  28   a  in the retracted configuration thus obviating the need for a separate retainer. 
         [0022]    With additional reference to  FIGS. 4 and 5 , as mechanical broadhead  10  impacts a target, leading edges  44 ,  44   a  of lever portions  38 ,  38   a  encounter resistance from the target. This creates a torque couple around shaft  30  which causes blade portions  36 ,  36   a  to be rotated outward from the retracted configuration to the deployed configuration as shown in  FIGS. 4 and 5 . With particular reference to  FIG. 5 , as pivoting blades  28 ,  28   a  move to the fully deployed configuration, locking tabs  46 ,  46   a  pass over each other and, because the locking tabs  46 ,  46   a  extend below the lower surface of pivoting blades  28 ,  28   a , locking tabs  46 ,  46   a  ride over each other then snap into position where the beveled regions  50 ,  50   a  can not pass over each other in the opposite direction. Locking tabs  46 ,  46   a  act as stops that effectively lock the blades into the deployed configuration against the resistance of the target, but because the blades are locked to each other rather than to the ferrule, the blades in the deployed configuration are still free to rotate together about shaft  30  and ferrule  12 . 
         [0023]    The present invention has a significant advantage over prior art mechanical broadheads in that with the blades  28  and  28   a  locked together in the deployed configuration, if the blade portion of one of the blades impacts an obstruction (for example if blade portion  36  of blade  28  strikes a bone  58  within target  60  as shown in  FIG. 6 ), the pivoting blades  28  and  28   a  will simply rotate in unison about shaft  30  without deflecting the trajectory of arrow  62  or worse damaging a blade or stopping the penetration of arrow  62  altogether. Finally, because locking tabs  46 ,  46   a  are in reality merely stops that prevent pivoting blades  28 ,  28   a  from rotating inward/rearward toward the retracted configuration relative to each other, pivoting blades  28 ,  28   a  are free to rotate independently forward, for example as the arrow is withdrawn from the target as shown in  FIG. 7 . This prevents pivoting blades  28 ,  28   a  from “barbing” which is illegal in many states. 
         [0024]    It is also well recognized in the art that the flight characteristics of broadheads and practice tips are usually different. It is desirable to practice with arrows having identical flight characteristics as the hunting broadhead, however, using a broadhead on a target is unduly destructive to both the target and the broadhead unless the blade deployment mechanism can be disabled. For this reason, mechanical broadhead  10  includes an aperture  66  that registers with the locking apertures  54 ,  54   a  formed in pivoting blades  28 ,  28   a  when pivoting blades  28 ,  28   a  are in the retracted configuration. A locking pin  68  is inserted through aperture  66  and locking apertures  54 ,  54   a . Locking pin  68  is sufficiently robust to prevent rotating blades  28 ,  28   a  from deploying upon impact with the target. This enables mechanical broadhead  10  to be used as a practice tip without undue destruction of the practice target or dulling of the forward edges  42  of the blade. 
         [0025]    With reference to  FIGS. 8 and 9 , in an alternative embodiment of a mechanical broadhead  110 , pivoting blades  128 ,  128   a  are mounted about a common shaft  130 . Pivoting blades  128 ,  128   a  each include a locking tab  146 ,  146   a . As mechanical broadhead  110  impacts the target, the impact forces cause pivoting blades  128 ,  128   a  to rotate outwards until locking tabs  146 ,  146   a  engage corresponding surfaces on blades  128   a  and  128  respectively. As with the embodiment of  FIGS. 1-6 , although blades  128  and  128   a  are locked together they remain free to rotate about shaft  130 . As with the embodiment of  FIGS. 1-7 , the embodiment of  FIGS. 8 and 9  can be locked into the retracted position for practice by inserting a locking pin into locking aperture  166 . 
         [0026]    Although certain illustrative embodiments and methods have been disclosed herein, it will be apparent from the foregoing disclosure to those skilled in the art that variations and modifications of such embodiments and methods may be made without departing from the invention. For example, although in the illustrative embodiments the blades are deployed by direct interaction with the target, spring-loaded and/or plunger-deployed blades are considered within the scope of the present invention, as well as any mechanical broadhead in which the blades are locked together rather than being locked to the ferrule. Additionally, although the blades in the illustrative embodiment are symmetrical, asymmetrical blades including asymmetrical blades in which the stop member is formed on only one of the blades are considered within the scope of the present invention. Accordingly, it is intended that the invention should be limited only to the extent required by the appended claims and the rules and principles of applicable law. Additionally, as used herein, unless otherwise specifically defined, the terms “substantially” or “generally” when used with mathematical concepts or measurements mean within ±10 degrees of angle or within 10 percent of the measurement, whichever is greater.