Abstract:
An aerodynamic multi-bladed expandable broadhead with rearward mounted overlapping blades with greater in-flight blade angles along with substantially perpendicular blade edges relative to the arrowhead body. Position of blades in flight guarantees they will always make a lethal cut on contact with an animal even before expansion. Greater in-flight blade angle means less force to open blades on hide guaranteeing expansion, and minimal rotation of blades to the penetration position results in a maximum entry cut and greater penetration. By expanding the distance between the blade edge and pivot a stronger blocky blade is produced. Geometry dictates during entry when blades hit bone on angle shots arrow direction will favorably remain in its intended lethal path to an animal.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional application Ser. No. 61/266,585, filed Dec. 4, 2009, which is incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to the field of archery, more specifically to hunting arrowheads called broadheads. There are two types of broadheads: fixed where there are no moving parts and a constant cutting diameter, and mechanical where there are moving parts. Mechanical broadheads have less surface area in flight for great accuracy, and an expanding diameter when contacting the animal for greater cutting diameter than when passing the bow riser and in flight. 
     A common problem of mechanical broadheads with the tips of the sharpened blade edges near the tip of the ferrule or head body is that the force it takes to open the blades reduces penetration, such as in Mizek et al., U.S. Pat. No. 5,564,713. Also, when a bone is hit upon entry the blade tip may act in a “pole vaulting” manner and push the arrow out from its intended path to a different angle and cause a non-fatal hit. 
     Another disadvantage is a small entry wound, such as is produced by the head described in Johnson, U.S. Pat. No. 5,879,252 where the blade tips enter the animal without having a fully expanded diameter. With a small entry hole, blood will not exit well for tracking. Also long slender blades have proven fragile when contacting bone. 
     Barrie et al., U.S. Pat. No. 6,910,979 attempts to improve mechanical performance by having the blades slide rearward, eliminating the pole vaulting effect of the blade tips. However, as in some other designs, blade securement is a problem, as the blade tips are lightly secured inserted inside an O-ring, such that removing the arrow from the quiver or the shock of launch may cause the head to open prematurely during flight, planing it off course. Further, the head is barbed in both its open and, more importantly, closed positions. 
     Forrest et al., U.S. Pat. No. 5,458,341, uses a trip blade to open the main cutting blade after that blade has penetrated the animal. This again produces a small entry wound. Also if the trip blade hits bone, it prevents the main blades from opening so the arrowhead loses penetration energy and is deflected. 
     Other patents on similar systems with similar problems include Vance, U.S. Pat. No. 2,820,634; Carlston, et al., U.S. Pat. No. 5,078,407; Ward, U.S. Pat. No. 5,286,035; Barrie et al., U.S. Pat. No. 6,517,454; Barrie et al., U.S. Pat. No. 6,910,979; Wohlfeil et al., U.S. Pat. No. 7,377,869; and Ward, U.S. Pat. No. D583,897. 
     All of the foregoing patents are hereby incorporated by reference. 
     SUMMARY OF THE INVENTION 
     The present invention is a mechanical broadhead whose geometry eliminates known problems with current broadheads. 
     The inventor has observed that the farther forward the blade tips are positioned and the more parallel the blade edge angle and blade tip is to the ferrule, the greater the undesirable “pole vaulting” effect of pushing the ferrule tip off course upon entry when the blade tips contact bone, resulting in an unintended arrow path away from the aimed path to the vital organs for a quick kill. By positioning the blades with their major cutting edges in a more perpendicular position to the ferrule axis during flight, upon contact with bone the arrow continues on a favorable path to the vitals. 
     Also, a more rearward position of the blade cutting edges allows the ferrule tip to contact the animal as the blade tips do on quartering shots, thereby directing the head to continue along the intended path. Greater in-flight angle of the blade cutting edges relative to the ferrule results in a shorter degree of pivoting rotation to a completely open position; this produces a maximum entry cut, and also gives greater leverage upon contact with an animal. This reduces the energy expended overcoming the resistance of the mechanism containing the blades in flight and reduces the force needed to pivot the blades to their fully rotated impact or penetration position, thus reliably insuring the blades will always open and producing improved penetration. 
     Since the blades are positioned at a point below where the ferrule tip is inserted in the quiver they are not subject to being opened accidentally or dulling blades. 
     In the preferred embodiments a simple elastic band may be positioned around the base of the blades near the pivot point, and they are reliably secured so as not to prematurely open by being bumped or by the force of the shot. The elastic band is positioned to constrain the blades until contact with an animal, then the band is either broken or pushed back as blades open allowing them to engage their penetration position, and after the shot the blades may pivot forward where they are not deemed illegally barbed. 
     In preferred embodiments, it is also possible for the band to remain positioned around the blades such that after the shot, the blades are forced forward by the band constrainment to a position where the blades are in a non-barbed position. Some regulations do not allow mechanical broadheads to be used as they may fail to open and produce a killing cut. However, in the broadhead of the present invention the novel blade geometry and position means that a substantial portion of the blade edges will make a lethal cut when the head contacts an animal, even without pivoting open, so the head is 100% guaranteed to reliably make a deadly cut as much as a fixed blade no matter what. 
     Since the blades substantially overlap each other inside the ferrule and in some embodiments outside the ferrule, surface area is reduced for greater aerodynamics and truer flight. 
     The blades are also of a blocky triangular geometry, resulting in greater strength as opposed to long slender blades which may break. In illustrative embodiments, the blade comprises a main cutting edge and a pivot, the distance from the pivot to the nearest point on the cutting edge being at least 50% as long as the distance from the point to a distal end of the blade. The absolute distance between the pivot and the nearest point on the cutting edge is preferably at least 0.25″. A generally triangular web between the cutting edge and the pivot further strengthens the blade and insures that the blade can be pulled out without any barb structure behind the cutting edge. 
     In embodiments of the invention, a mechanical broadhead comprises an arrowhead body having a central longitudinal axis, the body having a rearward end that attaches to an arrow shaft and a forward pointed end, the body having at least one slot; and at least two overlapping blades housed in the slot during flight, the blades being rotatably mounted in the slot to rotate rearwardly during impact with a target or game, each blade having a main cutting edge oriented at an angle of 90°±40° relative to the axis in flight. The orientation of the cutting edge is determined by drawing a line extending through the distal end of the edge (the end farthest from the central axis) and through the intersection of the edge with the axis, and measuring the angle between this line and the axis. In illustrative preferred embodiments, the cutting edge is straight, so the line and the edge are the same. The broadhead preferably comprises a pivot entirely behind the main cutting edge in flight. 
     The blades&#39; main cutting edges are preferably oriented 90°±15° relative to the long axis in flight and protrude a substantial distance, the distal ends of the cutting edges in flight preferably being spaced apart at least half their spacing in their fully open impact position. In some embodiments, each blade has cutting edge ends extending out both sides of the slot in flight. 
     Mechanical stops are preferably provided to set a maximum forward rotation of the blades in their closed flight position and to set a maximum rearward rotation in their open penetration position. Illustratively, each blade has a pivot base, rearward of the pivot, with a first portion which contacts the arrowhead body limiting the rotation of the blade in a closed flight position and a second portion which contacts the arrowhead body limiting the rotation of the blade in an open impact position. 
     In preferred embodiments of the invention, a line from the distal end of the cutting edge to the pivot point when the blade is in its open impact position forms an angle of 90°±20° with the central longitudinal axis. This orientation of the blade&#39;s main cutting edge insures that the spread of the blade&#39;s cutting edge in the fully open position is at least 95% of its maximum spread, in some embodiments at least 98% or more. Therefore, less energy is expended than in many previous designs in which the blades are momentarily opened farther than their final spread. 
     In illustrative embodiments, the distance between distal ends of the main cutting edges in closed flight position is between 1.0″ and 1.5″. This is a greater spread than is commonly found in mechanical broadheads. In these embodiments, the distance between the distal ends in open impact position is between 1.1 and 2.0 times the distance in closed flight position, and in some preferred embodiments the distance is between 1.1 and 1.5 times the distance in closed flight position. In these preferred embodiments, the maximum spread of the blades is also 1.1 to 1.5 times the closed spread between the distal ends of the cutting edges. Although this is far less than conventional mechanical broadheads, it has been found that the mechanical broadhead of the present invention has excellent flight characteristics and great effectiveness as a hunting head. 
     In preferred embodiments, the main cutting edge forms an angle of 45°±15° with the axis when the blade is in its open stop position. 
     In illustrative embodiments, at least a portion of the main cutting edge of each blade is exposed, and is spaced at least 0.25″ behind the point, the angle of a line through the blade tip and the pivot is 45°±15° in relation to the axis and the angle of the cutting edge is 90°±40° relative to the axis in flight in relation to the axis. 
     Also in illustrative embodiments, at least one blade is housed in the slot during flight, the blade being rotatably mounted by a pivot in the slot to rotate rearwardly from a closed flight position to an open impact penetration position during impact with a target or game, the blade having a main cutting edge, a line through the distal end of the main cutting edge and the pivot forming an angle with the axis of 45°±15 in the closed flight position and forming an angle with the axis of 90°±15° in the open penetration position. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a top plan view of one embodiment of novel arrowhead blade for use in a mechanical broadhead of the present invention. 
         FIG. 1A  is a plan view, partially cut away, of an expanding arrowhead of the present invention in flight position, containing dual pivoting blades of  FIG. 1 . 
         FIG. 1B  is a plan view of the arrowhead of  FIG. 1A  in its fully expanded penetrating position. 
         FIG. 2  is a plan view of a second embodiment of arrowhead blade of the present invention. 
         FIG. 2A  is a plan view of a second embodiment of expanding arrowhead in flight position containing dual pivoting blades of  FIG. 2 . 
         FIG. 2B  is a plan view of the arrowhead of  FIG. 2A  in its fully expanded penetrating position. 
         FIG. 3  is a plan view of a third embodiment of arrowhead blade of the present invention. 
         FIG. 3A  is a plan view of a third embodiment of expanding arrowhead in flight position containing dual pivoting blades of  FIG. 3 . 
         FIG. 3B  is a plan view of the arrowhead of  FIG. 3A  in its fully expanded penetrating position. 
         FIG. 4  is a plan view of a fourth embodiment of arrowhead blade of the present invention. 
         FIG. 4A  is a plan view of a fourth embodiment of expanding arrowhead in flight position containing dual pivoting blades of  FIG. 4 . 
         FIG. 4B  is a plan view of the arrowhead of  FIG. 4A  in its fully expanded penetrating position. 
         FIG. 5  is a plan view of a fifth embodiment of arrowhead blade of the present invention. 
         FIG. 5A  is a plan view of a fifth embodiment of expanding arrowhead containing dual pivoting blades of  FIG. 5 , in flight position and attached to an arrow contacting stretched animal hide. 
         FIG. 5B  is a top plan view of the arrowhead of  FIG. 2A  as the arrowhead further penetrates the animal hide and the blades are partially pivoted down by the animal hide. 
         FIG. 6  is a top plan view of a prior art arrowhead attached to an arrow, depicting the blade tip contacting animal hide and rib at a quartering angle. 
         FIG. 6A  is a top plan view of the prior art arrowhead and arrow of  FIG. 6 , depicting further progress of the arrowhead and its blade tip contacting animal hide and rib at a quartering angle. 
         FIG. 7  is a top plan view, corresponding to  FIG. 6 , of an expanding arrowhead of the present invention attached to an arrow, depicting its blade tip contacting animal hide and rib at a quartering angle. 
         FIG. 7A  is a top plan view of the expanding arrowhead and arrow of  FIG. 7  depicting further progress of the arrowhead and its blade tip contacting animal hide and rib at a quartering angle. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to  FIG. 1 , arrowhead blade  1  of the present invention includes a forwardly-facing sharpened main cutting edge  2 , a generally triangular web portion  3  behind the edge  2 , a pivot hole  5 , rotation-limiting base portions  6  and  7 , and a notch  14 . Because the sharpened cutting edge  2  of this embodiment is a straight line, the closest point  4  on the edge to the pivot hole  5  is the intersection with the cutting edge of a line perpendicular to it through the hole  5 . The main cutting edge  2  has distal end  11  in relation to pivot hole  5  and proximal end  12  in relation to pivot hole  5 . The cutting edge  2  of blade  1  is about 1.2″ long, about 0.7″ from the point  4  to the distal end  11  and about 0.5″ from the point  4  to proximal end  12 . The distance from the center of hole  5  to the point  4  is about 0.7″. 
       FIG. 1A  depicts an arrowhead of the present invention in a closed flight position. The arrowhead includes a body or ferrule  13  having a threaded arrow-engaging rear ferrule end  9  and a forward ferrule tip  10  in the form of a sharp point. The arrowhead has a central longitudinal axis C. A longitudinally extending interior slot  20  is cut laterally through the ferrule  13 . The slot  20  has a rear terminus  15  and forward terminus  16 , cut by cutting wheels to have central cusps  18  and  19  respectively. 
     The blade  1  is pivotably mounted in the slot  20  by pivot screw  8  extending through pivot hole  5 . Rotation-limiting base portion  7  is in contact with the right side of rear terminus  15 , limiting clockwise rotation. 
     An identical blade  1 ′, turned over so as to be a mirror image of blade  1 , is pivotably mounted on pivot screw  8  in longitudinally extending interior slot  20  of ferrule  3  under blade  1  as viewed in  FIG. 1A . Rotation-limiting base portion  7 ′ of the blade  1 ′ is in contact with the left side of rear terminus  15 , limiting counterclockwise rotation. 
     Blade  1 ′ also has proximal edge end  12 ′ in relation to pivot screw  8 , and distal edge end  11 ′ in relation to pivot screw  8 . Pivoting blades  1  and  2  are secured in ferrule  3  with screw  8 . Elastic band  17 , in the form of an o-ring, is positioned around ferrule  3  and the notches  14  and  14 ′ of blades  1  and  1 ′ securing them in a closed in-flight position. In this position, the distance between distal end  11  and distal end  11 ′ is about 1.5″. 
     As illustrated in  FIG. 1A , in its in-flight configuration, the forward main cutting edge  2  of the blade  1  (measured along a line from its distal end  11  to its intersection with the longitudinal axis C) forms a 90° angle with the longitudinal axis C of the body  13 . A line through the distal end  11  and pivot  8  forms an angle A with the axis C of about 47°. Likewise, a line through the distal end  11  and point  10  forms an angle B with the axis C of about 40°. The same angles apply to blade  1 ′. 
       FIG. 1B  depicts the arrowhead in an expanded penetration position. Rotation limiting base portion  6  has rotated so it is in contact with rear terminus  15 , limiting counterclockwise rotation, stopping blade  1  in its desired penetration position. Rotation limiting base portion  6 ′ of blade  1 ′ has rotated so it is in contact with rear terminus  15 , limiting clockwise rotation and stopping blade  1 ′ in its desired penetration position. 
     As shown in  FIG. 1B , in its extended, stop-limited impact position, the main cutting edge  2  forms an angle of about 45° with the axis C, as measured from the distal end  11  to a projected intersection with the axis C. A line through the distal end  11  and the center of pivot  8  makes an angle A′ of about a 92° with the axis C. These angles indicate that substantially the entire length of the cutting edge  2  is extended beyond the ferrule  13  and that the spread between the distal ends  11  and  11 ′ is 99.9% of the maximum spread attained during rearward rotation of the blades  1  and  1 ′. 
       FIGS. 2-2B  and  3 - 3 B illustrate modifications differing from the first embodiment only in the geometry, hence orientation, of the blades. 
     Referring to  FIG. 2  arrowhead blade  22  has pivot hole  25  and rotation limiting base portions  26  and  27 . Blade  22  also has proximal edge end  31  in relation to pivot hole  25  and distal edge end  32  in relation to pivot hole  25 . 
     Referring now to  FIG. 2A  depicting the arrowhead in a flight position, blade  22  mounted in a longitudinally extending interior slot of ferrule  24 , as defined by rear terminus  35  and forward terminus  36 , has pivot screw  28  and rotation limiting base portions  26  and  27 . Rotation limiting base portion  27  is in contact with rear terminus  35 , limiting clockwise rotation. Blade  22  also has proximal edge end  32  in relation to pivot screw  28  and distal edge end  31  in relation to pivot screw  28 . Blade  22 ′ mounted in longitudinally extending interior slot of ferrule  24  as defined by rear terminus  35  and forward terminus  36  has pivot screw  28  and rotation limiting base portions  26 ′ and  27 ′. Rotation limiting base portion  27 ′ is In contact with rear terminus  35 , limiting counter-clockwise rotation. Blade  22 ′ also has proximal edge end  32 ′ in relation to pivot screw  28 , and distal edge end  31 ′ in relation to pivot screw  28 . Pivoting blades  22  and  22 ′ are secured in ferrule  24  with screw  28 . Elastic band  37  is positioned around ferrule  24  and blades  22  and  22 ′ securing them in an in-flight position. Ferrule  24  has arrow engaging ferrule end  39  and ferrule tip  38 . 
       FIG. 2B  depicts the arrowhead in an expanded penetration position. Rotation limiting base portion  26  has rotated so it is in contact with rear terminus  35 , limiting counter clockwise rotation, stopping blade  22  in its desired penetration position. Edge end  32  and edge end  31  project out the same side of ferrule  24 . Blade  22 ′ has rotated rearwardly in the same way. Rotation limiting base portion  26 ′ has rotated so it is in contact with rear terminus  35 , limiting clockwise rotation, stopping blade  22 ′ in its desired penetration position. Edge end  34  and edge end  33  project out the same side of ferrule  24 . 
     Referring to  FIG. 3  arrowhead blade  42  has pivot hole  45  and rotation limiting base portions  46  and  47 . Blade  42  also has proximal edge end  52  in relation to pivot hole  45  and distal edge end  51  in relation to pivot hole  45 . 
     Referring now to  FIG. 3A  depicting the arrowhead in a flight position, blade  42  is mounted in a longitudinally extending interior slot of ferrule  44  as defined by rear terminus  55  and forward terminus  56  by pivot screw  48 . Rotation limiting base portion  47  is in contact with rear terminus  55 , limiting clockwise rotation. Blade  42  also has proximal edge end  52  in relation to pivot screw  48  and distal edge end  51  in relation to pivot screw  48 . 
     Blade  42 ′ is also mounted in the longitudinally extending interior slot of ferrule  44  as defined by rear terminus  55  and forward terminus  56  by pivot screw  48 . Blade  42 ′ has rotation limiting base portions  46 ′ and  47 ′. Rotation limiting base portion  47 ′ is in contact with rear terminus  55 , limiting counter clockwise rotation. 
     Elastic band  57  is positioned around ferrule  44  and blades  42  and  42 ′ securing them in an in-flight position. Ferrule  44  has arrow engaging ferrule end  59  and ferrule tip  58 . The forward main cutting edge of each blade  42  and  42 ′ forms an angle of about 70° with the central axis of the ferrule  44  in its flight position. This geometry reduces the spread between distal ends  51  and  51 ′ in the flight position. 
       FIG. 3B  depicts the arrowhead in an expanded penetration position. Rotation-limiting base portion  46  has rotated so it is in contact with rear terminus  55 , limiting counter clockwise rotation, stopping blade  42  in its desired penetration position. Blade  42 ′ also has rotated rearwardly until rotation-limiting base portion  46 ′ has rotated so it is in contact with rear terminus  55 , limiting clockwise rotation, stopping blade  42 ′ in its desired penetration position. Each blade  42  and  42 ′ has rotated until a line through the distal ends  51  and  51 ′ respectively and the pivot  48  each form an angle of about 95° with the central longitudinal axis C. Therefore, in the final, stopped, open impact position the spread between distal ends  51  and  51 ′ is about 99.6% of the maximum spread attained while the blades rotate rearwardly from their flight position. The geometry of this embodiment makes the spread between distal ends  51  and  51 ′ in the impact position about 1.8 times the spread in the flight position. 
     Referring to  FIG. 4 , arrowhead blade  62  has pivot hole  65  and rotation limiting base portions  66  and  67 . Blade  62  also has proximal edge end  72  in relation to pivot hole  65  and distal edge end  71  in relation to pivot hole  65 . 
       FIG. 4A  depicts the arrowhead in a flight position, with blade  62  mounted in a longitudinally extending interior slot of ferrule  64  as defined by rear terminus  75  and forward terminus  76 . In this embodiment, the ferrule  64  is molded or cast with the rear terminus  75  and forward terminus  76  formed during molding or casting. The ferrule  64  has pivot screw  68 . Rotation limiting base portion  67  is in contact with rear terminus  75 , limiting clockwise rotation. Blade  62  also has proximal edge end  72  in relation to pivot screw  68  and distal edge end  71  in relation to pivot screw  68 . 
     Blade  62 ′ is mounted in the longitudinally extending interior slot of ferrule  64  as defined by rear terminus  75  and forward terminus  76  by pivot screw  68 . Blade  62 ′ has rotation limiting base portions  66 ′ and  67 ′. Rotation limiting base portion  67 ′ is in contact with rear terminus  75 , limiting counterclockwise rotation. Pivoting blades  62  and  62 ′ are secured in ferrule  64  with screw  68 . 
     Elastic band  77  is positioned around ferrule  64  and blades  62  and  62 ′ securing them in an in-flight position. Ferrule  64  has arrow engaging ferrule end  79  and ferrule tip  78 . The forward main cutting edge of each blade  62  and  62 ′ forms an angle of about 100° with the central axis of the ferrule  64  in its flight position. This geometry reduces the spread between distal ends  71  and  71 ′ in the flight position. 
       FIG. 4B  depicts the arrowhead in an expanded penetration position. Rotation-limiting base portion  66  has rotated so it is in contact with rear terminus  75 , limiting counter clockwise rotation, stopping blade  62  in its desired penetration position. Blade  62 ′ also has rotated rearwardly until rotation-limiting base portion  66 ′ has rotated so it is in contact with rear terminus  75 , limiting clockwise rotation, stopping blade  62 ′ in its desired penetration position. Each blade  62  and  62 ′ has rotated until a line through the distal ends  51  and  51 ′ respectively and the pivot  48  each form an angle of about 100° with the central longitudinal axis C. Therefore, in the final, stopped, open impact position the spread between distal ends  51  and  51 ′ is about 98.5% of the maximum spread attained while the blades rotate rearwardly from their flight position. The geometry of this embodiment makes the spread between distal ends  71  and  71 ′ in the impact position about 1.1 times the spread in the flight position. 
     Referring now to  FIG. 5  a blade  82  is substituted for the blade  1  of  FIGS. 1-1B . The blade  82  has pivot hole  85  and rotation limiting base portions  86  and  87 . Blade  82  also has proximal edge end  92  in relation to pivot hole  85  and distal edge end  91  in relation to pivot hole  95 . 
       FIG. 5A  depicts the arrowhead in a flight position, with blades  82  and  82 ′ mounted in a longitudinally extending interior slot of ferrule  84 , which may be identical with ferrule  13  of the first embodiment. Rotation-limiting base portion  87  limits clockwise rotation of blade  82 , and base portion  87 ′ limits counterclockwise rotation of blade  82 ′. Pivoting blades  82  and  82 ′ are secured in ferrule  84  with screw  88 . 
     Elastic band  97  is positioned around ferrule  84  and blades  82  and  82 ′ securing them in an in-flight position. Ferrule  84  has arrow engaging ferrule end which is threaded into arrow  96 ; Ferrule  84  also has a forward ferrule tip  98 .  FIG. 5A  shows arrowhead tip  98  penetrating animal hide  97  in a broadside position. It will be seen that the blade tips do not touch the hide  97 , despite its being severely distorted by the penetration of arrow tip  98 . 
     Referring now to  FIG. 5B , expanding arrowhead  93  is shown further penetrating animal hide  97  with arrowhead tip  98 . Tips of blades  82  and  82 ′ have contacted animal hide  97  and pivoted down initiating the opening of expanding arrowhead to a penetration position. 
     Referring now to  FIG. 6 , a prior art expandable arrowhead  103  has tip  109  and is attached to arrow  106 . Overlapping blades  104  and  105  are mounted in expanding arrowhead  103  by screw  101  and constrained by elastic band  100  in an in-flight position. Tip of blade  104  is shown penetrating animal hide  107  and contacting animal rib  108  at a quartering angle. 
     Referring now to  FIG. 6A  as expanding arrowhead  103  progresses further, the tip of blade  104  striking rib  108  as expanding arrowhead  103  progresses forward has initiated opening of blade  104 . This action has caused expanding arrowhead  103  to be pushed (pole vaulted) at an unfavorable angle away from its intended lethal course. 
     Referring now to  FIG. 7 , the expandable arrowhead  93  of  FIG. 5A  in accordance with the present invention is shown striking an animal rib in the same manner as the foregoing prior art example. Tip of blade  82  is shown penetrating animal hide  117  and contacting animal rib  118  at a quartering angle. 
     Referring now to  FIG. 7A , as the expanding arrowhead progresses further, the tip of blade  82 , striking rib  118  as the expanding arrowhead progresses forward has initiated opening of blade  82 . The direction of the mechanical broadhead, however, continues forward in a favorable lethal angle to the animal&#39;s vitals for a quick, efficient kill. The function of this form of broadhead should be obvious from the sequential motion  FIGS. 5 and 5A , and  7  and  7 A, depicting blade tips contacting an animal so that blades are rotated downward to an open position. Blades may be mounted substantially perpendicular at various in-flight positions, as long as a greater length of blade edge extends from the side of the ferrule rotating down than the side of the ferrule rotating up. Greater leverage from contacting an animal with the greater length blade edge insures the blade will rotate down to its fully open penetration position. 
     Numerous variations in the construction of the broadhead of this invention will occur to those skilled in the art in the light of the foregoing disclosure. The external shapes or dimensions of the blades and the angles of the sharp edges can be varied. The arrowhead body (ferrule) and the tip can be made various shapes and can be made unitary or in parts. The body may be made of any appropriate material, including for example metal, such as aluminum, carbon steel, stainless steel, tungsten, or metal alloys, or hard plastic, such as composites. Numerous blades may be mounted. Fixed blades may be mounted in the tip or body in addition to moveable blades. The blades also may be made of any appropriate material, including for example those mentioned for the body. The terminal portion of the ferrule may also include numerous fittings besides the threaded shank. The elastic band may be either an o-ring as illustrated or a flat band. Various mechanisms may be used to secure the blades besides elastic band arrangements, such as blade-to-blade or blade-to-ferrule friction, spring arrangements, shear pins, magnetic attraction, etc. The blades may have ends that are blunt, recessed or pointed. The blades edges may be straight, curved, or irregular, such as serrated. Blade tips may extend forward from the ferrule, be parallel with the ferrule, or extend backward from the ferrule. These variations are merely illustrative. 
     In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results are obtained. As various changes could be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.