Abstract:
A blade system for a projectile includes a body having a front portion and a rear portion and an axis extending axially from the front portion to the rear portion. At least one blade is pivotably secured to the body. The blade includes an outer cutting edge and an inner cutting edge. The blade also includes a lever proximate a rear portion of the blade. An application of a force to the lever, for example as the lever contacts the skin, hide, or bone of an animal, pivots the blade from a closed position toward an open position. The lever has an unsharpened leading edge to prevent cutting of the target animal tissue to help ensure pivoting of the blade.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to and the benefit of U.S. Provisional Patent Application Ser. No. 61/451,875, filed Mar. 11, 2011, entitled “Pivoting Cutting Elements for Projectiles,” the disclosure of which is hereby incorporated by reference herein in its entirety. 
    
    
     INTRODUCTION 
     Mechanical broadhead arrowheads (“mechanical broadheads”) are used for hunting and are configured to expand upon impact with the hide or skin of a target animal. This expansion increases the cutting diameter of the broadhead as it penetrates the target, ideally resulting in more humane kills. Many mechanical broadheads include one or more blades pivotably engaged with an arrowhead body proximate a rear portion of the blade. Leading contact edges of each blade are positioned towards the front of the arrowhead and contact the hide or skin of a target as the arrowhead tip penetrates the hide or skin surface. This contact compels pivoting movement of each blade, thus extending the blades away from the body of the arrowhead. This pivoting movement exposes a sharp inner edge of the blade that cuts the tissue of the target. Once open, the blades are forced through the hide or skin of the target as the projectile travels further into the target. As a result, known mechanical broadheads lose significant kinetic energy as the extended blades penetrate the hide. This problem is exacerbated on larger targets like big game, targets with thick hide or hair, or when the projectile contacts the target proximate bone. Indeed, if the leading edges contact bone proximate the outer hide (for example, the ribs), the blades may open prior to significant penetration of the arrow into the target, thus reducing lethality. 
     Another type of mechanical broadhead  100  is depicted in  FIGS. 1A and 1B . The broadhead  100  may be attached to an arrow shaft, via a threaded connection  106 . The broadhead  100  includes a leading arrowhead or tip  104  and two or more blades  106  located within a slot  108 . The blades  106  include a lever portion  110  and a cutting portion  112 . A leading edge  110   a  of the lever portion  110  and a cutting surface  112   a  of the cutting portion  112  are sharpened. The blades  106  are pivotably connected to a body  114  of the broadhead  100  at a pivot connection proximate a rear portion of the blade  106 . A retention member  116  holds the blades  106  in the closed position, as depicted in  FIG. 1A . 
     When the broadhead  100  first penetrates a target, the arrowhead  104  and the body  114  form a puncture wound within the target. As the broadhead  100  further penetrates the target, the leading edge  110   a  of the lever portion  110  contacts the hide. Under desirable conditions, the force applied by this contact against the lever portion  110  compels the blades  106  to pivot, thus exposing the cutting edges  112   a  of the cutting portion  112 . This pivoting P breaks the retention member  116  and the blades  106  open to the position depicted in  FIG. 1B . There is a risk, however, that the broadhead  100  may not open as desired. Since the arrowhead  104  forms only a puncture wound as it penetrates the target, the leading edges  110   a  of the lever portions  110  are sharpened, allowing those elements to cut the tissue of the target. Should the blades  106  fail to open (due to lack of contact with denser muscle or bone), the broadhead  100  should still inflict a degree of damage to the target. This damage is not, however, as significant as damage inflicted by the exposed cutting portions  112 . Accordingly, further improvements of mechanical broadheads are still desirable. 
     SUMMARY 
     In one aspect, the technology relates to a blade system for a projectile, the blade system including: a body having a front portion and a rear portion and an axis extending axially from the front portion to the rear portion; a blade pivotably secured to the body, wherein the blade includes: an outer cutting edge; an inner cutting edge; and a lever proximate a rear portion of the blade, wherein an application of a force to the lever pivots the blade from a closed position toward an open position, wherein the lever comprises an unsharpened leading edge. In an embodiment, the body is adapted to be secured to at least one of an arrow shaft and an arrowhead. In another embodiment, the body is integral with at least one of an arrow shaft and an arrowhead. In yet another embodiment, when in the closed position, the inner cutting edge is located proximate the axis. In still another embodiment, the body defines a slot, wherein when in the closed position, the inner cutting edge is located within the slot and the outer cutting edge is exposed. 
     In another embodiment of the above aspect, when in the open position, the inner cutting edge extends substantially orthogonal from the axis. In another embodiment, the blade system further includes a retention element for releasably holding the blade in the closed position. In yet another embodiment, the blade system of claim  1 , further includes a breakable retention member, and the blade includes a notch, wherein the retention member is located in the notch when the blade is in the closed position. In still another embodiment, the retention member is adapted to break when the blade moves from the closed position to an intermediate position. In another embodiment, the blade includes a plurality of blades. In another embodiment, the blade system includes a spring for biasing the blade toward the open position. 
     In another aspect, the technology relates to an arrow including the blade system described herein. In another aspect, the technology relates to an arrowhead including the blade system described herein. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       There are shown in the drawings, embodiments which are presently preferred, it being understood, however, that the technology is not limited to the precise arrangements and instrumentalities shown. 
         FIGS. 1A-1B  are rear perspective views of a prior art mechanical broadhead, in a closed position and an open position, respectively. 
         FIGS. 2A-2C  are rear perspective views of a mechanical broadhead in a closed position, an intermediate position, and an open position, respectively. 
         FIG. 3  is a top view of the mechanical broadhead of  FIGS. 2A-2C . 
     
    
    
     DETAILED DESCRIPTION 
       FIGS. 2A-2C  are partial perspective views of an arrow having a mechanical broadhead or expandable blade system  200 . Although the following embodiments of the expandable blade system are described in the context of arrows, the technologies described herein may also be incorporated into bolts or quarrels for crossbows or for other types of substantially elongate projectiles launched from other implements. The figures depict the blade system  200  in a closed position ( FIG. 2A ), an intermediate position ( FIG. 2B ), and an open position ( FIG. 2C ). In the figures, the blade system  200  includes a body  214  that substantially surrounds an arrow shaft  202 , but other embodiments are contemplated. For example, the blade system may be an element that is integral with the arrow shaft. In another embodiment, the rear portion of the blade system body may be secured to a front end of an arrow shaft with a threaded, press fit, and/or chemical adhesive connection. An arrowhead or tip may be secured to a front portion of the body with a similar or different connection. In another embodiment, the blade system may be integral with an arrowhead, such that the arrowhead/blade unit may be secured to a front end of the arrow shaft. In still another embodiment, the blade system may be completely integrated with the arrow shaft. 
     Returning to the figures, the body  214  includes a front portion  214   a , a rear portion  214   b , and an axis A. In the depicted embodiment, the front portion  214   a  is located just beyond a pivot point (defined by an axis B) of the blades  206 . In alternative embodiments, the front portion of the body may extend closer to or to touch an arrowhead. Each blade  206  includes a lever portion  210  and a cutting portion  212 , which may be formed as a unitary part or discrete from each other. In the latter embodiment, the lever portion may be secured to the cutting portion with mechanical and/or chemical fasteners. In this case, the body  214  defines a slot  222  or recess for receiving an inner edge  212   a  of the cutting portion  212  of the blade  206  when the blade  206  is in the closed or non-deployed position. An outer edge  212   b  of the cutting portion  212  projects away from the axis A, so as to be exposed. The distance from the outer edge  212   b  of the cutting portion  212  to the axis A increases as a distance from the arrowhead  204  increases. The outer edge  212   b  may define a notch  218  configured to receive a retention member  216  or other element when the blade  206  is in the closed position. The blade  206  may also define a number of through-holes  206   a  or openings that reduce the weight of the blade  206 . In the depicted embodiment, both the inner edge  212   a  and the outer edge  212   b  are sharp to facilitate cutting of the target. In other embodiments, only the outer edge of the blade may be sharp though this may limit the cutting ability of the blades when deployed. The blade  206  is connected at a pivot pin proximate the rear portion of the blade  206 . Also located near a rear portion of the blade  206  is a lever portion  210 . When a force is applied to the lever portion  210  (as described in more detail below), the blade  206  is urged to pivot about the axis B defined by the pivot pin. In the embodiment depicted in  FIGS. 2A-2C , a leading edge  210   a  of the lever portion  210  is not sharp. 
     Operation of the depicted blade system  200  is described below, again in conjunction with  FIGS. 2A-2C .  FIG. 2A  depicts the blade system  200  in the closed position. In the closed position, the inner edges  212   a  of each blade  206  are located proximate and substantially parallel to the axis A of the body  214 , within the slots  222 . The retention member  216  is located within the notches  218  so as to hold the leading tips  220  of the blades  206  in the closed position. During aiming, release, flight, and initial penetration of the arrow into the target, the blade system  200  is in the closed position. Initial penetration of the arrow begins with penetration of the arrowhead  204  into the hide of a target animal. As the arrowhead  204  travels further into the hide, the sharp outer edges  212   b  of the blades  206  cut the hide and outer muscles of the animal. This is a particular advantage over other expanding broadheads that do not have exposed outer blade edges. In such broadheads, initial penetration of the arrow causes only a puncture wound, prior to opening of the blade system. In the depicted embodiment however, the outer edges  212   b  of the blades  206  cause a cutting wound during initial penetration. This increases the initial lethality of the arrow strike, generally resulting in a cleaner, more humane kill. 
       FIG. 2B  depicts the blade system  200  in an intermediate position. This intermediate position may be defined as any position between the closed position and the open position, described below. In general, the intermediate position may be any position in which the blades  206  are located, after rupture of the retention element  216 , but prior to reaching the open position. The initial penetration phase ends when the forward advancement of the arrow causes the lever portions  210  to contact the outer hide, muscle, or bone of the target animal. As the arrow continues to move forward, the force applied by the hide, muscle, or bone against the lever portions  210  forces those elements backward, thus pivoting P open the blades  206 . Once the blades  206  pivot P sufficiently, the retention member  216  ruptures or breaks, allowing the leading tips  220  to protrude beyond an outer diameter of the arrowhead  204 . Unsharpened leading edges  210   a  of the lever portions  210  help ensure movement of the lever portions  210 , as opposed to further cutting that may occur with sharpened leading edges of the levers of prior art systems. As the leading tips  220  of the blades  206  contact the muscle tissue, the blades  206  open rapidly while advancement of the arrow continues. Further opening of the blades  206  exposes a greater length of the inner edge  212   a  to the internal muscular structure, organs, etc., again increasing the lethality of the shot. In certain instances, due to the length of the blades  206 , the blades  206  may penetrate beyond the ribs of a target animal. Once the lever portion  210  contacts the rib bones, expansion of the blades begins within the chest cavity of the target animal, causing considerable damage therein. 
       FIG. 2C  depicts the blade system  200  in a fully-open or deployed position. This open position may be defined by the furthest range of rotation of the blades  206 . Contact between the blades  206  and the blade system body  214  (in this case a rear portion of the slots  222 ) may limit the final open position of the blades  206 .  FIG. 3  depicts a top view blade system  200  of  FIGS. 2A-2C . In certain embodiments, the open position may be reached when the inner edge  212   a  of the blades  206  are at an angle α approximately orthogonal to the axis A of the body  214 . In alternative embodiments, the inner edges  212   a  of the blades  206  may be at an angle α of about 80° to about 100°. Other ranges are contemplated. Of course, the blades  206  need not reach the full open position during penetration of the target, although the force of penetration and the pivoting movement P of the blades  206  make this likely. 
     Materials for the blade systems disclosed herein may be those known in the art. For example, the body may be manufactured of injection molded robust plastics such as those used typically used to manufacture arrow shafts. Additionally, the bodies may be made of lightweight aluminum or other metals. The blades may be manufactured of ceramic form, ceramic, or ceramic composites, or from high density plastics. More desirable, however, may be blades made from durable metals such as steel, stainless steel, titanium, brass, etc. Other non-corrosive materials may be utilized as desired for a particular application. Additionally, the blade systems described herein may include one, two, three, or more blades, blades having different lengths, or multiple rows of blades to open at different depths within a target. In that regard, the total number of blades utilized may be limited by projectile size, geometry, and/or weight, or other factors apparent to a person of skill in the art. The individual blades may have serrated or smooth cutting edges. While blade systems having outer cutting edges that project outward from the arrow shaft may be more desirable, embodiments having outer edges closer to the arrow shaft (that is, thinner blades) are also contemplated. The lever is but one mechanism that could be used to cause the blades to deploy after penetration. An alternative opening mechanism includes one or more springs that bias the blades into a deployed position. A catch may release the blade upon sufficient penetration, thus allowing the spring to deploy the blade. 
     While there have been described herein what are to be considered exemplary and preferred embodiments of the present technology, other modifications of the technology will become apparent to those skilled in the art from the teachings herein. The particular methods of manufacture and geometries disclosed herein are exemplary in nature and are not to be considered limiting. It is therefore desired to be secured in the appended claims all such modifications as fall within the spirit and scope of the technology. Accordingly, what is desired to be secured by Letters Patent is the technology as defined and differentiated in the following claims, and all equivalents.