Abstract:
An expandable arrowhead having a blade-carrying body with a slot that houses at least one movably mounted blade. Each blade can be pivotally mounted about a shaft. In some embodiments, the shaft is fixed with respect to the body. In other embodiments, the shaft is movably mounted with respect to the body, for example by mounting a shaft within the slot so that the shaft moves within the slot with respect to the blade-carrying body. In some embodiments of this invention, a spring element positively holds one or more blades in a closed position or a retracted position, particularly during extreme forces encountered when launching an arrow from an archery bow, such as a compound archery bow. The spring element of this invention can be used to improve blade opening capabilities of conventional blade-opening arrowheads or broadheads.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to an expandable arrowhead or broadhead having one or more blades that each are movably mounted within a slot of a blade-carrying body, and during movement from a retracted position to an expanded position each blade pivots and/or translates with respect to the blade-carrying body. 
     2. Discussion of Related Art 
     Many conventional blade-opening arrowheads or broadheads are designed to launch and fly or travel in a closed position or a retracted position and then upon impact with a target to move to an opened position or an expanded position in which cutting edges of the blades are exposed to the target. When an arrow is launched from an archery bow, a tremendous amount of forces are generated from the archery bow, particularly a compound archery bow, and transferred through the arrow shaft and into the arrowhead. When experiencing the relatively high gravitational or G-forces during arrow launch, many conventional blade-opening arrowheads have one or more blades that undesirably move out of the closed position or the retracted position, which decreases aerodynamic performance of the arrowhead and thus of the overall arrow. 
     To hold or maintain all blades of the arrowhead in the closed position during launch and flight, many conventional blade-opening arrowheads use an elastic band, such as a rubber band, or an O-ring to hold all blades in the closed position, until the arrowhead strikes the target and either breaks, severs or moves away the elastic band, rubber band or O-ring. 
     There is an apparent need for an expandable arrowhead or broadhead that positively holds, maintains or keeps each blade of a blade-opening arrowhead in the closed position or the retracted position during launch and flight of an archery arrow. There is also an apparent need for an apparatus, method and/or system that can be used to enhance or improve the ability for conventional expandable arrowheads or broadheads to maintain each blade in the closed position, particularly during launch and flight of an archery arrow. 
     SUMMARY OF THE INVENTION 
     In some embodiments of the expandable arrowhead according to this invention, a spring element is used to hold a corresponding movably mounted blade in a retracted position, particularly while encountering the relatively high forces generated at and through an arrow and a corresponding arrowhead when launched from an archery bow, until impact with a target at which time the blade moves to the expanded position. In other embodiments according to this invention, the spring element can be added to conventional blade-opening arrowheads or broadheads, to improve the capability and performance and thus allow each blade to remain in the closed position until impact with the target. 
     In some embodiments according to this invention, a blade-carrying body has two different slots within a ferrule body or other suitable blade-carrying body. At least one blade is movably mounted within each slot. It is possible to mount two or more blades within each slot. Each blade has an impact portion that receives an impact force upon contact with the target and also a cutting portion that is exposed to the target when the blade is in the expanded position. Each blade is designed to move from the retracted position to the expanded position when the impact force traveling through the blade overcomes a resistance bias force exerted by the spring element on the blade. 
     In some embodiments of this invention, the cutting portion of each blade is positioned or located opposite of the impact portion, for example so that the cutting portion is on one side and the impact portion is on another side of the body and/or the slot of the body. The spring element, the cutting portion, the impact portion and/or the shape and dimensions of the slot can be varied to accommodate different desired cutting patterns and/or blade opening capabilities. 
     According to some embodiments of this invention, a shaft is movably mounted within a second slot of the blade-carrying body, and the second slot is different than the first slot that houses a corresponding blade. The shaft can move with respect to the blade-carrying body when the blade moves between the retracted position and the expanded position. Movement of the shaft within the second slot allows the blade to translate or move in a generally linear direction with respect to the blade-carrying body. In some embodiments having the shaft movably mounted within the second slot, the blade also pivots about the shaft or moves in a radial direction about the shaft, and in such embodiments each blade can move along or follow a pivoting and translating movement path when the blade moves between the retracted position and the expanded position. In some embodiments of this invention, the spring element piggybacks the blade and thus moves with the blade, with respect to the body. 
     According to other embodiments of this invention, a shaft is fixedly mounted with respect to the blade-carrying body, for example within the second slot of the blade-carrying body. In some embodiments, the shaft only pivots or otherwise radially moves with respect to the blade-carrying body when the blade moves between the retracted position and the expanded position. Fixing or securing the shaft with respect to the blade-carrying body, for example within the second slot, can be used to prevent the blade from moving in a generally linear direction with respect to the blade-carrying body. In some embodiments having the shaft fixedly mounted with respect to the blade-carrying body, for example within the second slot, the blade only pivots about the shaft or only moves in a radial direction about the shaft. In some embodiments of this invention, when the shaft is fixedly mounted with respect to the blade-carrying body, for example within the second slot, the spring element remains fixed with respect to the body and thus does not move with the blade, with respect to the body. 
     The spring element of this invention can be used in combination with other elements of this invention and/or can be used as an improvement to conventional blade-opening arrowheads or broadheads. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       This invention is explained in greater detail below in view of exemplary embodiments shown in the drawings, wherein: 
         FIG. 1  is a perspective view of an expandable arrowhead, in a retracted position, according to one embodiment of this invention; 
         FIG. 2  is a perspective view of the expandable arrowhead as shown in  FIG. 1 , but in an expanded position; 
         FIG. 3  is an exploded perspective view of the expandable arrowhead as shown in  FIG. 1 , from one side; 
         FIG. 4  is an exploded perspective view of the expandable arrowhead as shown in  FIG. 1 , from a side opposite the side shown in  FIG. 3 ; 
         FIG. 5  is a perspective view of the expandable arrowhead as shown in  FIG. 1 , with the ferrule body hidden to show the blades in the retracted position; 
         FIG. 6  is a perspective view of the expandable arrowhead as shown in  FIG. 1 , with the ferrule body hidden to show the blades in the expanded position; 
         FIG. 7  is a sectional view taken along a centerline or central axis of the expandable arrowhead as shown in  FIG. 1 , with the blade shown in the expanded position; 
         FIG. 8  is a perspective view of an expandable arrowhead, in an expanded position, according to another embodiment of this invention; 
         FIG. 9  is a perspective view of a ferrule body, according to one embodiment of this invention; 
         FIG. 10  is a front view of the ferrule body as shown in  FIG. 9 ; 
         FIG. 11  is a top view of the ferrule body as shown in  FIG. 9 ; 
         FIG. 12  is a perspective view of a blade, according to one embodiment of this invention; 
         FIG. 13  is a perspective side view of a spring element, according to one embodiment of this invention; 
         FIG. 14  is a perspective side view, opposite the side view shown in  FIG. 13 , of the spring element shown in  FIG. 13 ; 
         FIG. 15  is a front view of the spring element as shown in  FIG. 13 ; 
         FIG. 16  is a side view of the spring element as shown in  FIG. 13 ; 
         FIG. 17  is a rear view of the spring element as shown in  FIG. 13 ; 
         FIG. 18  is a top view of the spring element as shown in  FIG. 13 ; 
         FIG. 19  is a side view, opposite the side view shown in  FIG. 16 , of the spring element as shown in  FIG. 13 ; 
         FIG. 20  is a bottom of the spring element as shown in  FIG. 13 ; 
         FIG. 21  is a perspective view of an expandable arrowhead according to another embodiment of this invention, showing blades in the retracted position; 
         FIG. 22  is a perspective view of blades and an O-ring, with the body hidden, of the expandable arrowhead as shown in  FIG. 21 ; 
         FIG. 23  is a perspective view of an expandable arrowhead according to another embodiment of this invention, showing blades in the retracted position; 
         FIG. 24  is a perspective view of the expandable arrowhead as shown in  FIG. 23 , showing the blades in the expanded position; 
         FIG. 25  is a perspective view of blades and a spring element of the expandable arrowhead as shown in  FIG. 23 , with the blades in the retracted position; 
         FIG. 26  is a perspective view of the blades and the spring element of the expandable arrowhead as shown in  FIG. 23 , with the blades in the expanded position; 
         FIG. 27  is a front view of the expandable arrowhead as shown in  FIG. 23 ; 
         FIG. 28  is a front transparent view of an expandable arrowhead, according to another embodiment of this invention; 
         FIG. 29  is a front view of blades and a spring element, showing the blades in the retracted position, of the expandable arrowhead as shown in  FIG. 28 ; 
         FIG. 30  is a front view of blades and a spring element, showing the blades in the expanded position, of the expandable arrowhead as shown in  FIG. 28 ; 
         FIG. 31  is a front view of one blade and one spring element, showing the blade in the retracted position, of the expandable arrowhead as shown in  FIG. 28 ; 
         FIG. 32  is a front view of the blade and the spring element shown in  FIG. 31 , showing the blade in the expanded position, of the expandable arrowhead as shown in  FIG. 28 ; 
         FIG. 33  is a front view of another blade and the spring element, showing the other blade in the retracted position, of the expandable arrowhead as shown in  FIG. 28 ; 
         FIG. 34  is a front view of the blade and the spring element shown in  FIG. 33 , showing the blade in the expanded position, of the expandable arrowhead as shown in  FIG. 28 ; 
         FIG. 35  is a perspective view of a spring element, according to another embodiment of this invention; 
         FIG. 36  is a front view of the spring element as shown in  FIG. 35 ; and 
         FIG. 37  is a side view of the spring element as shown in  FIG. 35 . 
     
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
       FIGS. 1-37  show different embodiments of expandable arrowhead  10  according to this invention. As used throughout this specification and in the claims, the term expandable arrowhead or expandable broadhead is intended to relate to and include any apparatus and/or method in which one or more blades each moves between a retracted position and an expanded position, and while moving with respect to a blade-carrying body each blade pivots and/or translates with respect to the blade-carrying body, for example so that when moving between the retracted position and the expanded position each blade translates in a generally longitudinal direction of the blade-carrying body and/or pivots or moves radially outward from the blade-carrying body. Elements and method steps of this invention cooperate with and/or supplemented by other elements and/or method steps known to those skilled in the art of designing and manufacturing arrowheads and broadheads. For example, U.S. Pat. Nos. 5,564,713, 5,941,784, 6,174,252, 6,398,676, 6,517,454, 6,626,776, 6,910,979 and 6,935,976, the entire teachings of each and every one of which are incorporated into this specification by reference thereto, relate to pivoting and/or translating blade-opening arrowheads or broadheads that can remain in a closed position or a retracted position during arrow launch and flight and then move into an opened position or an expanded position upon impact at or with a target, including devices, systems and method steps which can be used in connection with the apparatus and/or the method and/or the system of the expandable arrowhead or broadhead according to this invention. 
       FIGS. 1-33  show different embodiments of a blade-opening expandable arrowhead  10  according to this invention. Many embodiments of this invention relate to expandable arrowhead  10  having both pivotal and translational movement between the retracted position and the expanded position. However, in other embodiments of this invention, expandable arrowhead  10  can have only pivotal movement or only translational movement. As used throughout this specification and in the claims, the terms expandable arrowhead, expandable broadhead, blade-opening arrowhead, blade-opening broadhead, arrowhead, broadhead and other similar terms are intended to be interchangeable with each other and relate to any arrowhead that opens, expands and/or moves from a closed position or a retracted position during arrow launch and flight to an opened position or an expanded position upon impact at or with a target. 
     For example,  FIG. 1  shows one embodiment of arrowhead  10  in a closed position or a retracted position, and  FIG. 2  shows the same embodiment of arrowhead  10  in an opened position or expanded position.  FIGS. 5 and 6  show the same embodiment of arrowhead  10  operating between the retracted position of  FIG. 5  and the expanded position of  FIG. 6 . As shown between  FIGS. 1 and 2  and also between  FIGS. 5 and 6 , the cutting diameter D increases and translational distance T, the distance blade  30  moves in a generally longitudinal direction along or with respect to body  20 , increases as arrowhead  10  moves from the retracted position to the expanded position. Thus, in some embodiments according to this invention, between the retracted position and the expanded position, blade  30  pivots and translates with respect to blade-carrying body or body  20 . In other embodiments of this invention, blade  30  only pivots or only translates or only moves along some other suitable path, with respect to body  20 . 
     In some embodiments according to this invention, such as shown in  FIGS. 9-11 , body  20  comprises slot  25  and slot  65 . Slot  25  and/or slot  65  can extend across or from one side to another side of body  20 . Slot  25  and slot  65  can merge into each other and/or intersect with each other. In other embodiments of this invention, slot  25  can be separated or independent from slot  65 . Slot  25  and/or slot  65  can have the same or similar shapes and dimensions as shown in  FIGS. 9-11 , or can have any other suitable different shape and/or dimension. 
     As shown in  FIGS. 1-4 , for example, two blades  30  are movably mounted within one slot  25 . In other embodiments according to this invention, one blade  30  or three or more blades  30  can be movably mounted within each slot  25 . Many conventional broadheads or arrowheads have ferrules or blade-carrying bodies with three or more slot configurations, so that the broadhead or arrowhead can have three or more movably mounted blades  30 . For example, U.S. Pat. No. 6,910,979 discloses arrowheads having three or more slot configurations. In some embodiments of this invention, each blade  30  has one corresponding slot  25  within which the one blade  30  is movably mounted and no slot  25  has more than one blade  30  movably mounted. In other embodiments of this invention with three or more slots  25 , some slots  25  house only one blade  30  and at least one other slot  25  houses more than one blade  30 . 
     As shown between  FIGS. 1 and 2 , for example, at least a portion of blade  30  is movably mounted within slot  25 . Blade  30  can be movably mounted to pivot, rotate, move along an arc, translate, move along a longitudinal direction and/or move in or along any other desired direction or movement path, by using elements taught by this invention or any other suitable elements that accomplish a similar movement. Also as shown in  FIG. 1 , for example, impact portion  71  and cutting portion  72  of each blade  30  are positioned or located on or at opposite sides of slot  25 . As shown in  FIG. 1 , for example, a distance of moment arm M can be increased or decreased to increase or decrease torque applied to blade  30  when opening force or impact force  28  is applied to impact portion  71 , such as through or along blunt edge  38 . Also, the size and/or shape of impact portion  71  and/or blunt edge  38  can be varied to differently apply a resutant impact force  28  and thus differently move blade  30 . In some embodiments of this invention, moment arm M provides a mechanical advantage for transferring opening forces, such as impact force  28 , from impact portion  71  through blade  30  to open and expose sharp edge  37  of blade  30  to the target material. 
     In some embodiments of this invention, at least a portion of cutting portion  72  of blade  30  extends beyond outer surface  35  of body  20 , such as shown in  FIG. 7 , when arrowhead  10  is in the retracted position and/or the expanded position. In other embodiments of this invention, cutting portion  72  can be completely contained within slot  25  so that no portion of cutting portion  72  extends beyond outer surface  35  of body  20  when arrowhead  10  is in the retracted position and/or the expanded position. 
     As shown in  FIGS. 1 and 2 , for example, impact portion  71  and cutting portion  72  of the same blade  30  are on opposite sides of slot  25 . In some embodiments according to this invention, impact portion  71  is on an opposite side of longitudinal axis  63 , such as shown in  FIGS. 1 ,  2  and  8 . With impact portion  71  oppositely positioned of or with respect to cutting portion  72 , in some embodiments of this invention, a greater or different force can be used to open blade  30  or to move blade  30  from the retracted position to the expanded position. 
     In some embodiments according to this invention, such as shown in  FIGS. 1-8 , blade  30  has bore or opening  32  and pivot shaft or shaft  40  is mounted within opening  32 . In some embodiments of this invention, blade  30  pivots about shaft  40  and/or center axis  41 . The size and shape of opening  32  as well as the size and shape of shaft  40  can be varied to accomplish different pivoting actions or other similar or different movements of blade  30  with respect to body  20  and/or shaft  40 . For example, opening  32  can form a circle with a diameter that forms a relatively loose fit about shaft  40 , or can have a diameter that forms a relatively tight fit about shaft  40 , depending upon the frictional resistance and relative movement desired between blade  30  and shaft  40 . As shown in  FIGS. 23-34 , for example, opening  32  can form a non-circle, such as a slot, that can be sized and shaped to result in more than just pivotal movement of blade  30  with respect to shaft  40 , for example can result in pivotal and/or translational movement of blade  30  with respect to shaft  40 . In some embodiments according to this invention, opening  32  forms a relatively straight or linear slot while in other embodiments of this invention opening  32  forms a relatively non-linear, arcuate and/or curved slot. 
     As shown in  FIGS. 1 ,  2 ,  21  and  22 , for example, shaft  40  is movably mounted within slot  65 . In some embodiments of this invention, shaft  40  slides, translates or otherwise moves within slot  65  and with respect to body  20 . In other embodiments of this invention, shaft  40  can be movably mounted with or without slot  65  to slide, translate or otherwise move in a general longitudinal direction of body  20  or in any other suitable direction with respect to body  20 . In other embodiments of this invention, shaft  40  can be fixed with respect to body  20 , and for example, can be securely fixed and/or fixed with limited movement in a pivotal or translational direction. As shown in the drawings, shaft  40  has a circular or a generally circular cross-section. In other embodiments of this invention, shaft  40  can have a different cross sectional shape and/or can be sized and/or shaped to allow movement of shaft  40  with respect to body  20 . 
     In some embodiments of this invention, arrowhead  10  further comprises spring element  51  mounted with respect to blade  30  and/or relaeasably fixed with respect to blade  30 , to provide or supply a bias force to, upon and/or against blade  30 , by direct contact and/or indirect contact. In some embodiments of this invention, spring element  51  biases, urges or otherwise forces or moves blade  30  into the retracted position. In some embodiments of this invention, spring element  51  contacts blade  30 , directly or indirectly, such as in a frictional manner, a mechanical manner and/or in another engageable manner. 
       FIGS. 3-7  show one embodiment of how spring element  51  is secured or otherwise attached with respect to blade  30 .  FIGS. 13-20  show one embodiment of spring element  51  comprising two lock tabs  59 , shown as extending away from baseplate or body  56  of spring element  51 .  FIG. 7  shows one embodiment of spring element  51  mounted with respect to blade  30 . As shown, each of the two lock tabs  59  fits within or is releasably engaged within bore or recess  36  of blade  30 . In some embodiments according to this invention, the fit between spring element  51  and blade  30  is relatively tight, resulting in increased friction and thus little or no movement of spring element  51  with respect to blade  30 . In other embodiments according to this invention, the fit between spring element  51  and blade  30  is relatively loose, resulting in less friction and some movement of spring element  51  with respect to blade  30 . In some embodiments of this invention, spring element  51  piggybacks with, rides with and/or moves with blade  30  as blade  30  pivots, translates and or otherwise moves with respect to body  20 . 
     Spring element  51  may comprise only one lock tab  59  or more than two lock tabs  59 . Lock tab  59  can have the shape and/or dimensions as shown in  FIGS. 13-20 , or can have any other suitable shape that allows spring element  51  to be fixed, secured or otherwise mounted with respect to blade  30 , with either a tight fit or a loose fit. Spring element  51  can further comprise through hole or opening  58  within which shaft  40  is mounted, in some embodiments of this invention. Opening  58  can form a circular bore or a non-circular bore. The clearance between spring element  51  and shaft  40  can be selected to provide either a relatively tight fit or a relatively loose fit between spring element  51  and shaft  40 . With shaft  40  mounted within opening  58  of spring element  51 , only one lock tab  59  is needed to hold or fix the position of spring element  51  on or with respect to blade  30 . Spring element  51  can releasably hold or removably fix blade  30  in the retracted position, such as by spring element  51  having at least one lock tab  59  and contact portion  52  or another similar structure interfering with movement of blade  30  and/or spring element  51 . 
     As shown in  FIGS. 13-20 , spring element  51  may further comprise detent  55  and/or raised portion or contact portion  52 , which can be integrated with each other as shown in  FIGS. 13-20  or can be separated from each other. In some embodiments according to this invention, detent  55  and/or raised portion  52  each contacts outer or skin surface or surface  68  of blade  30 . The size, dimensions and/or internal bias force of detent  55  and/or raised portion  52  can be varied to provide or supply a desired or a selected bias force acting upon blade  30 . In other embodiments of this invention, detent  55  and/or raised portion  52  engages within bore or recess  36  and/or another suitable opening within blade  30 , to releasably hold blade  30  in the retracted position. 
     In some embodiments according to this invention, opening force or impact force  28  applied to impact portion  71  and/or blunt edge  38  transfers forces through blade  30 , providing torque about shaft  40  and/or center axis  41 , to move blade  30  from the retracted position to the expanded position. Features or parts of impact portion  71  and or blunt edge  38 , for example, including but not limited to the moment arm acting at or through blade  30 , can be sized and designed to overcome the bias force of spring element  51  acting upon and holding or urging blade  30  in the retracted position. Thus, as arrowhead  10  enters a target material, spring element  51  and/or blade  30  can be designed to enter the target material with blade  30  in the retracted position and then upon contact between impact portion  71  and the target material move blade  30  into the expanded position, such as for exposing sharp edge  37  and/or cutting portion  72  to and thus cutting the target material. 
     Spring element  51  can releasably hold blade  30  in the retracted position. In some embodiments according to this invention, such as shown in  FIGS. 1-7 , spring element  51  is mounted to and thus piggybacks, rides or moves with blade  30  as blade  30  pivots and/or translates with respect to body  20 . In other embodiments according to this invention, such as shown in  FIGS. 23-34 , spring element  51  remains fixed in place or stationary with respect to body  20 , and in some embodiments as blade  30  moves with respect to body  20 , blade  30  also moves with respect to spring element  51  because spring element  51  remains relatively fixed or in a stationary position, allowing for fit tolerances, with respect to body  20 . 
     Thus, in some embodiments according to this invention, spring element  51  pivots, translates or otherwise moves with blade  30  from the retracted position to the expanded position, and in other embodiments of this invention, spring element  51  remains fixed to, detachably secured to and/or releasably attached to body  20  or another suitable element fixed with respect to body  20 , and blade  30  does not pivot, translate or otherwise move with blade  30  from the retracted position to the expanded position. 
     As shown in  FIGS. 25 and 26 , for example, side edge  57  abuts or contacts body  20 , such as at sidewall  22 , a shoulder portion and/or another suitable structural portion of body  20 . When assembled, such as shown in  FIG. 28  for example, shaft  40  mounted within bore  32  forms an interference fit and side edge  57  contacting body  20  limits or prevents movement of spring element  51  with respect to body  20 . Although side edge  57  is shown with an arcuate curve, side edge  57  can have a straight or linear shape and/or a curved or non-linear shape, in other embodiments according to this invention. 
     In some embodiments of this invention, such as shown in  FIGS. 28-37  for example, spring element  51  has raised portion  52  and/or detent  55  positioned between side edge  57  and opening  58  of spring element  51 . In other embodiments according to this invention, the relative position of opening  58  and raised portion  52  and/or detent  55  can be switched or can have yet a different configuration or position arrangement. 
     In some embodiments of this invention, spring element  51  comprises a wave washer, a disc spring, a circular spring, a Belleville spring and/or any other suitable bias element and/or spring device. In some embodiments of this invention, spring element  51  is positioned between two corresponding blades  30 , while in other embodiments of this invention spring element  51  is positioned between blade  30  and body  20 , and in still yet other embodiments of this invention spring element  51  is positioned between any other suitable structure or device part of or similar to body  20  and/or another blade  30 . Intermediate elements can be directly or indirectly positioned between spring element  51  and body  20 , blade  30  and/or any other structure, part or piece of or cooperating with body  20  and/or blade  30 . 
     In some embodiments according to this invention, spring element  51  releasably holds blade  30  in the retracted position and when moving between the retracted position and the expanded position blade  30  follows a pivoting and translating movement path. In other embodiments according to this invention, blade  30  follows a different pivoting and/or translating movement path. Spring element  51  comprises contact portion  52  interfering with blade  30  along at least a portion of the pivoting and translating movement path of blade  30 . In some embodiments according to this invention, as blade  30  moves along the pivoting and translating movement path between the retracted position and the expanded position, such as shown from  FIG. 5  to  FIG. 6 , for example, distance  62  is varied between a shaft axis, such as center axis  41 , of shaft  40  and a contact area  67  formed at, near or between contact portion  52  and blade  30  and/or body  20  and/or any other suitable structure or element directly or indirectly connected to blade  30  and/or body  20 . 
     In some embodiments of this invention, spring element  51  contacts shaft  40  at or near opening  58  and spring element  51  has a lock surface engageable with body  20  and/or any other suitable structure, to prevent movement of spring element  51  with respect to body  20  as blade  30  follows the pivoting and translating movement path. 
       FIGS. 21 and 22  show expandable arrowhead  10 , according to one embodiment of this invention. In this embodiment, O-ring  75  is used in lieu of spring element  51 , but in other embodiments can be used in addition to spring element  51 , to hold each blade  30  in the retracted position. Upon impact with the target material, impact force  28  acts upon impact portion  71  to open each blade  30  into the expanded position. O-ring  75  can be designed for reuse or for disposable. 
       FIGS. 23-27  show another embodiment of expandable arrowhead  10  according to this invention.  FIG. 23  shows arrowhead  10  in the retracted position and  FIG. 24  shows arrowhead  10  in the expanded position.  FIGS. 25 and 26  show spring element  51  remaining in a fixed or relatively stationary position with respect to body  20 , and each blade  30  moves with respect to spring element  51  and body  20  between the retracted position and the expanded position.  FIG. 27  shows body  20  having two slots  25  and two blades  30  with each blade  30  mounted within one corresponding slot  25 . 
       FIGS. 28-34  show another embodiment of expandable arrowhead  10  according to this invention.  FIG. 29  shows blades  30  in the retracted position and  FIG. 30  shows blades  30  in the expanded position. As shown in  FIGS. 29-34 , spring element  51  remains in a fixed or relatively stationary position with respect to body  20 , and each blade  30  moves with respect to spring element  51  and body  20  between the retracted position and the expanded position. 
       FIGS. 35-37  show one embodiment of spring element  51  that requires no lock tab  59  to retain the position of spring element  51  with respect to body  20  and/or blade  30 . 
     While in the foregoing specification this invention has been described in relation to certain preferred embodiments, and many details are set forth for purpose of illustration, it will be apparent to those skilled in the art that this invention is susceptible to additional embodiments and that certain of the details described in this specification and in the claims can be varied considerably without departing from the basic principles of this invention.