Patent Publication Number: US-RE44474-E

Title: Arrowhead with pivoting blade

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     The present application claims the benefit of U.S. provisional patent application Ser. No. 61/038,286 filed Mar. 20, 2008, the disclosure of which is hereby incorporated herein by reference in its entirety. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to arrows used archery hunting and, more particularly, to arrowheads used in conjunction with archery hunting. 
     BACKGROUND OF THE INVENTION 
     It is an aim of hunters to promote a humane kill of an animal. Archery hunters generally kill animals by causing blood loss in the animal. Therefore, it is desirable to provide an arrowhead that promotes maximum penetration into the animal with a large entry wound, thereby increasing the rate of blood loss of a wounded animal to allow for a more humane kill. Additionally, for an archery hunter to be effective and to prevent undue suffering of an animal, the hunter&#39;s arrow should travel a straight or substantially straight path to its intended mark, so that the hunter may place his or her shot accurately to rupture vital organs of an animal. 
     SUMMARY OF THE INVENTION 
     The present invention provides a pivotable arrowhead for an arrow with an arrowhead body having a substantially pointed portion or tip. The arrowhead includes at least one blade pivotally mounted at the body, with the blade having a substantially sharpened portion or leading edge and a rearwardly or trailing portion or edge. A retaining mechanism is configured to substantially engage a notch in the rear portion of the blade, thereby impeding pivotal movement of the blade about the pivotal connection. 
     Optionally, the retaining mechanism may include a biasing element that biases or urges an engaging element into the notch to retain the blade and limit or impede pivotal movement of the blade. The biasing element may allow the engaging element to move outward from the notch in response to an initial pivotal movement of the blade, whereby the blade may more freely pivot when the engaging element is withdrawn from the notch. 
     According to another aspect of the present invention, an arrowhead includes a pair of blades pivotally and movably received in a channel or slot formed in a body and mounted to the body via a pivot pin and a guide pin. The blades engage a pivot-limiter movably disposed at the channel or slot and are thereby substantially locked relative to one another when in either a deployed position or undeployed position. A retaining mechanism, including the pivot-limiter, is adapted to limit the range of pivotal movement of the blades when they are in the deployed position. 
     Therefore, the present invention provides a broadhead arrowhead that has a broad pivotal blade pivotally mounted to an arrow body. The arrowhead limits pivotal movement of the blade until one side of the blade encounters an object whereby the force of impact is sufficient to overcome a biasing force that retains the blade in its initial or centered position, whereby the blade may more freely pivot. Thus, the arrowhead may penetrate an animal and may continue penetration after impacting a bone with the blade by allowing the blade to pivot upon impact with the bone structure and thus allowing the arrowhead to continue penetration to one side of the bone structure. 
     These and other objects, advantages, purposes and features of the present invention will become apparent upon review of the following specification in conjunction with the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side elevation of an arrowhead with a pivoting blade in accordance with the present invention; 
         FIG. 2  is a side elevation and partial sectional view of the arrowhead of  FIG. 1 ; 
         FIG. 3  is a another sectional view of the arrowhead of  FIG. 1 ; 
         FIG. 4  is a side elevation of another arrowhead with a pivoting blade in accordance with the present invention; 
         FIG. 5  is a side elevation and partial sectional view of the arrowhead of  FIG. 4 ; 
         FIG. 6  is another sectional view of the arrowhead of  FIG. 4 ; 
         FIG. 7  is a side elevation of another arrowhead with pivoting blades in accordance with the present invention, shown with the blades in a folded position; 
         FIG. 8  is another side elevation of the arrowhead of  FIG. 7 , shown with the pivoting blades in the deployed position; 
         FIG. 9  is an exploded partial sectional view of the arrowhead of  FIG. 7 ; 
         FIG. 10  is a partial sectional view of the arrowhead of  FIGS. 7-9 , shown with the blades in the folded position; 
         FIG. 10A  is a side elevation view of a blade shown in  FIG. 10 ; 
         FIG. 10B  is a side elevation view of another blade shown in  FIG. 10 ; 
         FIG. 11  is another partial sectional view of the arrowhead of  FIGS. 7-9 , shown with the blades in the deployed position; 
         FIG. 12  is another sectional view of the arrowhead of  FIG. 7 ; and 
         FIG. 13  is a perspective view of an arrowhead body in accordance with the present invention; 
         FIG. 14  is an end elevation of the arrowhead body of  FIG. 14 ; 
         FIG. 15  is a side elevation of another arrowhead with pivoting blades in accordance with the present invention, shown with the blades in a retracted or undeployed position; 
         FIG. 16  is another side elevation of the arrowhead of  FIG. 15 , shown with the pivoting blades in a deployed position; 
         FIG. 17  is a partial sectional view of the arrowhead of  FIGS. 15-16 , shown with the blades in the undeployed position; 
         FIG. 18  is another partial sectional view of the arrowhead of  FIGS. 15-17 , shown with the blades in the deployed position; 
         FIG. 19  is a side elevation of the arrowhead shown in  FIG. 15 ; and 
         FIG. 20  is a side elevation of the arrowhead shown in  FIG. 16 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the drawings and the illustrative embodiments depicted therein, an archery hunting device or arrowhead  10  includes a blade  12  that is pivotally mounted at a body  14  and is pivotable about a pivot pin or axis  16  ( FIGS. 1-3 ). Blade  12  pivots between a first or center position and a second or angled position in response to contact or impact or engagement of a blade edge  18  with an object, such as bone, cartilage, or the like, in a target animal. A retaining mechanism  20  is biased or urged against a rear edge or portion  22  of blade  12  to resist such pivotal movement unless and until the force acting against a side region of the blade edge  18  is sufficient to overcome a biasing force of the retaining mechanism and cause the blade to pivot. Thus, arrowhead  10  will minimally impede travel of an arrow through an animal after encountering bone or cartilage (by allowing the blade to pivot to allow the arrowhead to continue its penetration into the animal at a side of the encountered or impacted bone structure), thereby resulting in a deeper wound cavity for a more humane kill. 
     In the illustrated embodiment, body  14  has an elongated shape, such as a cylindrical shape, and may have a substantially pointed portion or tip  26 . Body  14  may have a slot or passageway  15  ( FIG. 3 ) for receiving blade  12  and to allow passage of blade  12  through body  14  during assembly. Slot  15  may be located substantially coincident with the longitudinal axis of body  14  to promote balanced flight and accuracy of arrowhead  10 . Further, body  14  may include a biasing element passageway and internally threaded portion  30  for receiving retaining mechanism  20  (discussed below) and a pin passageway for receiving pivot pin  16 . Optionally, the pin passageway may include a passageway or threaded bore  28  to accept a threaded pivot pin  16  or, alternatively, may be adapted to receive pivot pin  16  by a press-fit or interference-fit or the like. 
     Body  14  may further include an externally threaded portion  32  for connection to an arrow shaft. In such a configuration, arrowhead  10  may be used as an arrowhead attached to a conventional arrow shaft or bolt for use with a bow or crossbow. Optionally, it is envisioned that arrowhead  10  may be unitarily formed with or otherwise attached to a shaft of an arrow, while remaining within the spirit and scope of the present invention. 
     As best seen in  FIG. 2 , blade  12  has one or more substantially sharpened cutting front portions or edges or faces  18  and a rear edge  22  with a notch  24 , and includes an aperture adapted to facilitate pivotable connection to body  14  with pivot pin  16 . Blade  12  is positioned at body  14  and through slot  15 . Thus, the thickness of blade  12  is selected to be sufficiently thin as to allow the blade to fit in the slot during assembly of the arrowhead and to pivot therein when in use, as discussed below. In the illustrated embodiment, blade  12  has two substantially symmetrical sharpened side portions or wings for balanced flight and to provide a large cutting surface (which will promote a large wound cavity). Notch  24  is located at rear edge  22  opposite cutting edges  18  and may be centrally located so as to be substantially equidistant from the ends of rear edge  22 . By centrally locating notch  24 , the blade is centered when notch  24  is engaged with retaining mechanism  20 , thereby promoting straight and accurate flight of the arrowhead. 
     In the illustrated embodiment, retaining mechanism  20  includes an engaging element, such as a ball bearing  34 , that is urged toward notch  24  by a biasing element  36 . Biasing element  36  is disposed within arrowhead body  14  and engages ball bearing  34 , and may be set to a compressed state by threadably connecting a set screw (not shown) to internally threaded portion  30  of body  14 , whereby biasing element  36  is disposed between the set screw and the ball bearing  34 . Biasing element  36  may comprise any suitable element or material for urging ball bearing  34  toward notch  24 , such as, for example, a conventional spring-steel compression spring, or an elastomeric material such as rubber or the like. However, skilled artisans will recognize that other methods of urging ball bearing  34  toward notch  24  can be utilized without departing from the principles of the present invention. 
     When blade  12  is set or positioned in its initial or centered position, ball bearing  34  is urged into notch  24  to substantially retain blade  12  in its initial or centered position. When a force is applied to one of the side portions or wings or edges of the blade that is greater than a force applied to the other side portion or wing or edge of the blade, and when such an imbalance in forces is sufficient to overcome the force exerted by biasing element  36 , ball bearing  34  will be urged downward by pivotal movement of blade  12  and out of notch  24 , whereby blade  12  will pivot in a direction away from the side at which the greater force is applied. 
     Optionally, the retaining mechanism may have a biasing element that biases a bearing or other engaging element toward the tip or point or leading portion of the arrowhead body. For example, a blade otherwise substantially similar to blade  12  may have a notch positioned at the tip or point or forward portion of the blade, and a ball bearing or other suitable engaging element may be biased into the notch to engage the notch, thereby limiting pivotal movement of the blade until the biasing force is overcome and the bearing is forced out of the notch, such as in a similar manner as discussed above. Such a retaining mechanism may be used in addition to, or in lieu of, retaining mechanism  20  and notch  24  (described above). 
     In addition to holding blade  12  in a centered position relative to body  14 , retaining mechanism  20  may also function to dampen pivotal movement of blade  12 . As the amount of force exerted by biasing element  36  on ball bearing  34  increases (such as when ball bearing  34  is urged out of notch  24  by pivotal movement of the blade), ball bearing  34  may act to impede or limit pivotal movement of blade  12  (even after ball bearing  34  has been forced out of notch  24 ). Thus, a desired resistance to pivotal movement can be achieved by selecting a biasing element  36  capable of delivering a desired amount of force and damping. 
     Pivotal movement or resistance to pivotal movement of blade  12  may be limited or controlled by the configuration of rear edge  22  and/or spring force and/or engagement of the ball bearing  34  with the blade. For example, pivotal movement of blade  12  and/or resistance to such pivotal movement of blade  12  may be controlled or adjusted by altering the shape or configuration of rear edge  22 . Accordingly, if rear edge  22  has a substantially constant radius of curvature, the radius of such a circle may have an origin at the pivot axis of the blade, or the origin of the circular profile may be located longitudinally toward or away from the rear edge of the blade with respect to the pivot axis, in order to influence pivotal movement of the blade when the blade is not in its initial or centered position (such as, for example, biasing the blade toward or away from its centered position). Rear edge  22  may also take non-circular or non-arcuate forms, such as a linear or angular profile, for providing the desired or appropriate pivotal characteristics of blade  12 , depending on the particular application and desired performance characteristics of the arrowhead. 
     During assembly of arrowhead  10 , blade  12  is attached to body  14  by pivot pin  16  or other pivot connection. Such pivot connection may be made with a set screw or other threaded connector attached to threaded bore  28 . Optionally, the pivot connection may be an interference-fit pin, cotter, or other such device as will be apparent to the skilled artisan. Ball bearing  34  is placed in the biasing element passageway of body  12  with biasing element  36  being disposed in the passageway below ball bearing  34 . A set screw may then be threadably connected to the body via internally threaded portion  30 , and may be tightened against the force of biasing element  36  until a desired tension or biasing force at ball bearing  34  is achieved. Finally, the arrowhead assembly  10  may be attached to a bolt or arrow by externally threaded portion  32  or via other connection means or the like. 
     When the arrow is fired and during its flight, retaining mechanism  20  cooperates with notch  24  to hold blade  12  in its centered position relative to body  14 , thereby maintaining a substantially even weight distribution about the longitudinal axis of body  14  for balanced flight and accuracy. When arrowhead  10  finds its mark on the animal being hunted, the centered position of blade  12  is maintained until one wing or side of blade  12  encounters a harder material than the material encountered by the other wing or side. Such differential hardnesses encountered by the respective wings of the blade creates a rotational force that may overcome the biasing force of retaining mechanism  20  at notch  24 , thereby allowing blade  12  to pivot about pivot pin  16 . For example, one wing may impact a bone in the ribcage of an animal, while the other wing may pass through the space between two ribcage bones. In such a situation, the blade pivots such that the wing contacting bone pivots to clear the bone, thereby reducing or minimizing the loss of the arrow&#39;s kinetic energy as a result of the impact and facilitating further penetration of the arrowhead. During such pivoting, ball bearing  34 , after being dislodged from notch  24 , traces rear edge  22  as the blade pivots toward one side or the other. The pivoting of blade  12  allows arrowhead  10  to continue its path into the animal, rather than slowing or stopping as a result of resistance encountered by one side of the blade as it hits bone or cartilage. 
     Thus, arrowhead  10  achieves deeper penetration into the animal than it otherwise would absent the pivoting of blade  12 . Deeper penetration, in turn, results in a larger wound cavity and a faster rate of bleeding of the animal and a more humane kill. Once past the bone or cartilage or object, the blade may pivot back toward its center position as the other wing then encounters a greater resistance than the first blade wing (which was pivoted to be generally along the arrowhead after impact with the bone or the like). In addition, the arrowheads are durable, and are capable of being reset to their centered position and reused many times before parts fail from wear. This is because the ball bearing, being preferably made of a hard, durable substance (such as steel or other suitable material), will not wear out or degrade by the small amount of movement of the blade relative to the ball bearing, such that the arrowhead may be re-used multiple times without adverse affects on its performance. Moreover, the arrowhead may be produced with little or no degradable materials such as rubber or plastic, thereby enhancing the durability and longevity of the arrowhead even in harsh outdoor environments. 
     Referring now to  FIGS. 4-6 , an archery hunting device or arrowhead  110  includes a wheeled retaining mechanism  120  for retaining a blade  112  in a centered position. Similar to arrowhead  10 , blade  112  of arrowhead  110  is pivotally mounted at a body  114  within a slot  115  and is pivotable about a pivot pin or axis  116 . The blade  112  includes one or more sharpened portions  118  and notched rear edge  122 . Body  114  may include a pointed portion  126  and a pivot passageway or bore  128 , such as a threaded passageway or the like, and an externally threaded portion  132 . Arrowhead  110  may be generally similar to arrowhead  10 , discussed above, such that a detailed discussion of the arrowheads need not be repeated herein. The similar components are referenced in  FIGS. 1-3  and  4 - 6  with like reference numbers, but with the reference numbers of  FIGS. 4-6  having 100 added thereto. 
     In the illustrated embodiment, retaining mechanism  120  includes a wheel  134  configured to rotate about pivot pin  116  as blade  112  pivots. Wheel  134  allows for pivotal movement of blade  112  by compressing of wheel  134  or movement of wheel  134  away from blade  112  or both. For example, wheel  134  may be made of a flexible material, such as rubber, elastomeric material or the like, such that wheel  134  may compress to allow the wheel to move out of notch  124  to allow the blade to pivot. Optionally, the wheel may be connected to a linear retaining mechanism or biasing element, such as in a similar manner as discussed above with respect to retaining mechanism  20 , to facilitate displacement of the wheel away from notch  124 . Retaining mechanism  120  may further include a bearing or bushing (not shown) to aid in smooth rotation of wheel  134 . Such bearing or bushing may be any suitable bearing or device for easing rotation of wheel  134 , such as, for example, a ball bearing, a bronze oilite-type bushing or the like, as will be apparent to the skilled artisan. 
     During assembly, wheel  134  may be pivotably attached to body  114  by an axle  136 . Axle  136  may, for example, be a set-screw, cotter pin, press-fit pin, or the like. Retaining mechanism  120  may be located in a slot or passageway in body  114 , thereby substantially centering wheel  134  with respect to body  114  for balance (see  FIG. 6 ). After assembly, arrowhead  110  may be connected to an arrow or used as a projectile as described above. When fired and during flight, blade  112  is in an initial centered position wherein wheel  134  is at and partially in notch  124 . When force is exerted at blade edge  118 , as when one wing of the blade  112  encounters a harder material than the material encountered by the other wing, wheel  134  may be compressed or displaced by such force differential whereby blade  112  may then pivot, such as in a similar manner as described above. 
     In addition to holding blade  112  in a centered position relative to body  114  (such as during flight), retaining mechanism  120  may be used to dampen pivotal motion of blade  112 . For example, if the resilience of the material used for wheel  134  is increased, it may act to impede pivoting of blade  112  even after wheel  134  has been forced out of notch  124 . Also, the presence or absence of a ball bearing or bushing may affect how freely wheel  134  rotates and, thus, how freely blade  112  pivots. Thus, a desired resistance to pivotal movement of blade  112  can be achieved by selecting a material for wheel  134  that is capable of delivering a desired or appropriate amount of force, and/or selecting or omitting a bushing or bearing to promote or impede rotation of wheel  134 . 
     Referring now to  FIGS. 7-12 , an archery hunting device or arrowhead  210  includes a first blade  212  and a second blade  213  pivotally mounted at a body  214  and pivotable about a pivot pin or axis  216 . Arrowhead  210  may otherwise be substantially similar to arrowhead  10 , discussed above, such that a detailed discussion of the arrowheads need not be repeated herein. The similar components are referenced in  FIGS. 1-3  and  7 - 12  with like reference numbers, but with the reference numbers of  FIGS. 7-12  having 200 added thereto. 
     Body  214  may include a pointed portion  226 , a passageway or threaded bore  228 , and an externally threaded portion  232 , similar to body  14 , but may further include a wider slot  215  to accommodate at least two overlapping blades ( FIG. 12 ). First blade  212  and second blade  213  each have at least one substantially sharpened portion or edge  218  and  219 , respectively, and each includes an aperture adapted to facilitate pivotable connection to body  214  with pivot pin  216 . Each blade may include an interlocking tab  222  that lock the blades in a deployed position. As best seen in  FIGS. 10-10B , the interlocking tabs may comprise non-planar portions or curved or turned portions of the otherwise planar blades with the tabs  222  extending toward the other adjacent blade, such that when first blade  212  and second blade  213  pivot or open sufficiently, the non-planar portion or tab of the first blade snaps over the edge or non-planar portion or tab of the second blade, thereby substantially interlocking the two blades to form a substantially unitary whole blade. When so interlocked, the two blades may pivot together about pivot pin  216  in the manner of a single blade. First blade  212  and second blade  213  may be substantially identical to promote manufacturing efficiency and cost effectiveness. 
     In the illustrated embodiment, first blade  212  has a first opening lever  224  configured to convert the force of impact with an object, such as an animal, into pivotal motion of first blade  212  toward its open position ( FIG. 8 ). Second blade  213  may be configured similar to first blade  212 , with a second opening lever  225  configured to translate the same or similar force employed in pivoting first blade  212  into pivoting of second blade  213  toward its deployed position. Thus, arrowhead  210  may be fired with blades  212 ,  213  in a folded or closed position, as discussed below. When the arrowhead impacts an animal, the flesh of the animal pushes against levers  224 ,  225 , thereby pivoting the blades to an open or unfolded position. Further, because the opening of the blades occurs substantially immediately upon impact, the expanded wound cavity resulting from the opened blades (discussed below) runs along substantially the entire depth of the wound. 
     First blade  212  and second blade  213  may overlap in a folded or centered or aligned position ( FIG. 10 ) and may shift to a deployed position ( FIG. 11 ), wherein first blade  212  and second blade  213  may interlock to hold or lock the blades in the deployed position. Once interlocked, the blades, acting as a unitary whole, may be acted upon by a retaining mechanism to generally retain the blades in a centered position (as discussed below). The pivot connection between blades  212  and  213  and body  214  allows the blades to fold or deploy and to pivot after deployment, and may be made with a set screw or other threaded connector or the like. Alternatively, the pivot connection may be established with an interference-fit pin, cotter pin, or other such device, as will be apparent to the skilled artisan. 
     Thus, while arrowhead  210  is in flight, first blade  212  and second blade  213  may be in a folded position ( FIG. 7 ) to minimize the frontal area of the blades, thereby reducing wind drag and the potential for accuracy-degrading aerodynamic imperfections and helping the arrowhead fly like a field point, i.e. an arrowhead with no affixed blades. Upon impact with an object such as an animal, first blade  212  and second blade  213 , responding to forces exerted on first opening lever  224  and second opening lever  225 , respectively, pivot to a deployed position ( FIG. 8 ), thereby forming a broad cutting blade for promoting an increased rate of bleeding and a more humane kill. Further, when in the deployed position, the interlocked blades may pivot about pivot point  234  relative to the arrowhead body, such as in a similar manner as described above. 
     Optionally, a retaining mechanism (not shown in  FIGS. 7-12 ) may also be utilized with arrowhead  210 , such as a biasing element with a ball bearing or a spring wheel in accordance with retaining mechanisms disclosed herein. If a retaining mechanism is employed, first blade  212  and second blade  213  may each comprise a notched portion of a rear edge (not shown) to create a rear edge substantially similar to those described above when in the deployed position. The retaining mechanism may retain the blades in their folded or aligned positions to provide a straighter flight, and/or the retaining mechanism may retain the blades in a centered position when in their deployed position. Thus, such a retaining mechanism could act to retain the blades in a centered deployed position until one blade encounters a material harder than the other blade encounters, as described in detail above. 
     In any of the illustrated embodiments, and as shown in  FIGS. 13 and 14 , the arrowhead body  14  may include a tip portion  40  that has a wider flared section  40 a and a narrower flared section  40 b each extending outwardly from opposed sides of the arrowhead body, and with the wider flared section  40 a extending further from the arrowhead body than the narrower flared section  40 b. The narrower and wider flared sections are generally normal to one another, forming a star-shaped or diamond-shaped cross section at the flared portions. The outward extension of the blade or blades (not shown in  FIGS. 13 and 14 ) received in the slot  15  may generally coincide with the narrower flared section, so that the portion of the wound cavity created by the wider flared section is normal to the portion of the wound cavity created by the blade or blades. Therefore, the size of the wound cavity is enhanced by the flared portions of the arrowhead. Further, the large frontal area formed by the flared sections transfers a substantial amount of kinetic energy to the animal upon impact prior to the cutting action of the blade. 
     Therefore, the function of the pivoting or pendulum blade allows for a large wound cavity with deeper penetration because the blade will pivot upon contact with bone or harder tissue. This allows an arrow equipped with the arrowhead disclosed herein to pass through the animal with less resistance and without being jolted off its intended course. This provides enhanced penetration for increased bleeding of the animal, and therefore results in an efficient kill. With the pivoting of the blade, there may be little or no loss in accuracy because the retention mechanism ensures the blade will stay at a centered position during flight, thereby limiting problems that may arise from an unbalanced arrowhead. With two pivotable blades, the flight characteristics can be improved still further, providing for a more aerodynamic arrowhead with the same or nearly the same potential for a large wound cavity associated with the single-blade embodiments. 
     Referring now to  FIGS. 15-20 , an archery hunting device or arrowhead  310  includes a first blade  312  and a second blade  313  pivotally mounted at a body  314  and pivotable about a pivot pin or axis  316 . A blade retaining mechanism including a guide element or pivot-limiter  317  is received in a slot or channel  315  of body  314  that accommodates overlapping blades  312 ,  313 . Pivot-limiter  317  is movably disposed within the slot and retained within the slot  315  via a guide pin  321 . Arrowhead  310  may be substantially similar to arrowhead  210 , discussed above, such that a detailed discussion of the arrowheads need not be repeated herein. The similar components are referenced in  FIGS. 7-12  and  15 - 20  with like reference numbers, but with the reference numbers of  FIGS. 15-20  having 100 added thereto. 
     Body  314  may include a pointed or tip portion  326  (such as similar to tip portion  40 ), a passageway or threaded bore  328  ( FIGS. 19 and 20 ) for receiving pivot pin  316 , another passageway or threaded bore  329  for receiving guide pin  321 , an externally threaded base or attachment portion  332 , and slot  315  to accommodate at least two overlapping blades. As shown in  FIGS. 19 and 20 , the slot  315  is configured to receive the blades  312 ,  313  in a stacked or overlapping orientation so that the blades are movable within the slot relative to the body and to one another as they move from an undeployed position to a deployed position, as discussed below. The slot is also configured to movably receive the pivot-limiter therein whereby the pivot-limiter is movable within the slot with the blades as they move or pivot together when in their deployed position, as also discussed below. 
     First blade  312  and second blade  313  each have at least one substantially sharpened portion or edge  318  and  319 , respectively, and each includes an elongate aperture  312 a,  313 a that is configured to facilitate pivotable and movable or slidable connection to body  314  via pivot pin  316 . Each blade includes a shelf region  331  that rests against the forward or leading surface of pivot-limiter  317  when the blades are in an undeployed state ( FIG. 17 ). Shelf regions  331  may be somewhat arcuate in shape to match the shape of the upper surface of the pivot-limiter and retain the blades relative to the pivot-limiter when the blades are in the undeployed state. Optionally, the shelf regions may be frictionally held against the upper surface of the pivot-limiter by a resilient member  327 , as described below. Each blade also includes a locking tab  322  that engages pivot-limiter  317  to lock the blades in a deployed position, as discussed below. First blade  312  and second blade  313  may be substantially identical to promote manufacturing efficiency and cost effectiveness. 
     In the illustrated embodiment, a first opening lever  324  of first blade  312  is configured to convert the force of impact with an object, such as an animal, into pivotal motion of first blade  312  toward its open position ( FIG. 16 ). Second blade  313  may be configured similarly to first blade  312 , with a second opening lever  325  configured to translate the same or similar force employed in pivoting first blade  312  into pivoting of second blade  313  toward its deployed position. Thus, arrowhead  310  may be fired with blades  312 ,  313  in a folded or closed or undeployed position. When the arrowhead impacts an animal, the flesh of the animal pushes against levers  324 ,  325 , which urges the blades in the aft direction to disengage the shelves  331  from the pivot-limiter, thereby allowing the blades to pivot to an open or unfolded or deployed position, as discussed below. 
     Blades  312 ,  313  are configured to be initially retained in an undeployed state ( FIGS. 15 ,  17 , and  19 ), with the blades oriented generally along the body with their opening levers  324 ,  325  flared partially outward at the tip portion of the body. When the arrowhead  310  strikes a target, such as an animal, the front portions may contact the object and cause the blades to move along the body (such as in an aft direction) while the blades move and pivot to their deployed position. The aft motion combined with pivoting motion of the blades during deployment is facilitated by the elongated curved or arcuate shapes of apertures  312 a,  313 a in blades  312 ,  313 , which permit pivot pin  316  to travel along the respective apertures from the aft ends of the apertures in the undeployed state ( FIGS. 15 and 17 ) to the forward ends of the apertures in the deployed state ( FIGS. 16 and 18 ). Once the blades are in the deployed state, their respective locking tabs  322  engage opposite end portions  317 a,  317 b of pivot-limiter  317  and are capable of pivoting about pivot pin  316  (which is positioned at the forward ends of the apertures  312 a,  313 a of the blades) to the extent permitted by guide pin  321  in channel  323 . 
     As best seen in  FIGS. 16 and 18 , locking tabs  322  of blades  312 ,  313  may comprise projections along opposite edges from the sharpened edges and extending generally toward body  314  when blades  312 ,  313  are deployed. When first blade  312  and second blade  313  pivot or open sufficiently, the locking tab of each blade snaps over a respective side of pivot-limiter  317 , thereby substantially locking the two blades in their deployed configuration to form a substantially unitary whole blade that moves with pivot-limiter  317 . When so locked, the two blades may pivot together about pivot pin  316  in the manner of a single blade (such as described above with respect to blade  10 ). 
     Pivot-limiter  317  is movably received in channel  315  of body  314  and defines a channel or slot or guide  323  having a generally arcuate shape with a radius of curvature approximately equal to the distance between guide pin  321  and pivot pin  316 . Pivot-limiter  317  is movable in a side-to-side manner along guide pin  321  and has opposed end portions  317 a,  317 b that are contacted by guide pin  321  to limit the extent of travel of pivot-limiter  317  in either direction within slot  315 . Optionally, guide pin  321  is semi-rectangular with a thickness or diameter corresponding to generally the width of channel  323  and an arcuate shape corresponding to the radius of curvature of the channel, thus permitting pivot-limiter  317  to move or slide along guide pin  321 , but substantially without pivoting or rotating about the guide pin. 
     First blade  312  and second blade  313  may overlap in a folded or centered or aligned position ( FIGS. 15 ,  17 , and  19 ) and may shift to a deployed position ( FIGS. 16 ,  18 , and  20 ), wherein locking tabs  322  of first blade  312  and second blade  313  engage pivot-limiter  317  to hold or lock the blades in the deployed position. Once locked, the blades, acting as a unitary whole with pivot-limiter  317 , are free to pivot to the extent allowed by guide pin  321 , which travels in channel  323  of pivot-limiter  317 . The pivot connection between blades  312 ,  313  and body  314  (at pivot pin  316 ) allows the blades to fold or deploy and to pivot after deployment, and may be made with a set screw or other threaded connector or the like. Alternatively, the pivot connection may be established with an interference-fit pin, cotter pin, or other such device, as will be apparent to the skilled artisan. 
     Optionally, and as shown in  FIGS. 17 and 18 , a retainer such as a resilient element or member  327  positioned in slot  315  aft of pointed portion  326  may also be utilized with arrowhead  310  to resist inadvertent, premature, or undesirable deployment of blades  312 ,  313 . Resilient member  327  is compressible and may include a concave region  327 a that engages convex regions  312 b,  313 b of blades  312 ,  313  adjacent opening levers  324 ,  325  when the blades are in the undeployed position. The resilient member is somewhat compressed or deformed when the blades are undeployed to urge shelf regions  331  against the upper or leading surface of pivot-limiter  317  and frictionally retain the blades in their folded or aligned positions. This provides a straighter flight of an arrow equipped with arrowhead  310  until one or both opening levers  324 ,  325  encounter resistance or a solid material, causing blades  312 ,  313  to begin to pivot while further deforming convex portions  327 b of resilient member  327  on either side of concave region  327 a and causing shelf regions  331  to slide along the upper or leading surface of pivot-limiter  317  as described above. 
     As forces are applied to the opening levers  324 ,  325 , the blades begin to pivot in response to these forces, but do not initially move aft because pivot-limiter  317  substantially prevents them from doing so until the blades pivot to an extent that the shelf regions disengage the upper or leading surface of the pivot-limiter. The shape of the slots allow for pivotal movement of the blades until the shelf regions are disengaged from the pivot-limiter, whereby the slots allow for aft movement and pivotal movement of the blades relative to the body and pivot pin. Once shelf regions  331  disengage the leading surface of pivot-limiter  317 , the blades continue to pivot outward and begin to move or slide aft in slot  315  toward their fully-deployed configuration. When the blades are fully deployed, the locking tabs engage the pivot-limiter to substantially lock the blades in the deployed position. The blades  312 ,  313  then pivot about pivot pin  316  as pivot-limiter  317  moves along guide pin  321 . The length or lateral extent of pivot-limiter  317  and channel  323  defines the outer travel limits of the blades when they are in the deployed position, where the longer the pivot-limiter and channel are, the greater the extent of pivoting travel available to blades  312 ,  313 . Thus, the length of pivot-limiter  317  and channel  323  may be selected to have either more or less pivoting travel available according to the needs for a particular application. 
     Thus, while arrowhead  310  is in flight, first blade  312  and second blade  313  may be in a folded position ( FIGS. 15 and 17 ) to minimize the frontal area of the blades, thereby reducing wind drag and the potential for accuracy-degrading aerodynamic imperfections and helping the arrowhead fly like a field point, i.e. an arrowhead with no affixed blades. Upon impact with an object such as an animal, first blade  312  and second blade  313 , responding to forces exerted on first opening lever  324  and second opening lever  325 , respectively, pivot and slide to a deployed position ( FIGS. 16 and 18 ), and may be substantially locked in the deployed position via pivot-limiter  317 , thereby forming a broad cutting blade for promoting an increased rate of bleeding and a more humane kill. Further, when in the deployed position, the locked blades may pivot about pivot pin  316  relative to the arrowhead body, such as in a similar manner as described above with respect to arrowheads  10 ,  110 ,  210 . After use, the blades may be manually pivoted outward to disengage them from the pivot-limiter, whereby the blades may be moved back to their undeployed position (and retained in the undeployed position via the retention or biasing forces provided by the resilient element) so the arrowhead is ready for another use. 
     Changes and modifications to the specifically described embodiments may be carried out without departing from the principles of the present invention, which is intended to be limited only by the scope of the appended claims as interpreted according to the principles of patent law.